JPH0734852B2 - Method for manufacturing hollow fiber microfilter bundle - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing a hollow fiber-shaped microfilter bundle used in a fluid filtration device, and more specifically, bonding ends of a bundle of hollow fiber-shaped microfilters. The present invention relates to a method of integrally melt-bonding by heat fusion without using an agent.

(Prior Art) As a technique for heat-melt-bonding end portions of a tube bundle, as described in Japanese Patent Publication No. 46-4228, heat-bonding is performed by applying a pressure difference between the inside and outside of the bundled tubes. Method is used. Further, as to the technique of heat fusion bonding of the hollow fiber-shaped porous membrane, as described in JP-A-63-59311, the hollow fiber-shaped porous membrane is heated and melted in advance to eliminate voids, and a simple tube is formed. A method of hot-melt adhering to the inside of the above portion while applying a pressure difference between the inside and outside thereof is used.

(Problems to be Solved by the Invention) There are the following problems in performing the hot-melt bonding of the hollow fiber-shaped porous membrane by the conventional technique. Since the hollow fiber-like porous membrane has voids, not just tubes, even if a pressure difference is provided between the hollow part and the outside, gas will escape through the voids during heating, resulting in the shape of the hollow fiber-like porous membrane. Can't keep up. Further, in the method of performing heating and melting in advance, the inner diameter and the outer diameter of the hollow fiber-shaped porous membrane are drastically reduced due to the shrinkage.

For example, an ethylene-tetrafluoroethylene copolymer resin produced by the method described in JP-A-62-106808, an inner diameter of 0.77 mm, an outer diameter of 1.24 mm, a hollow fiber-like porous membrane having a porosity of 67% is 285 ° C. After leaving it in the furnace set for 10 seconds, it was air-cooled to room temperature, and the inner diameter of the hollow fiber was 0.30 mm, which was drastically reduced to about 39% before heating.

This is fatal in the filtration element composed of the hollow fiber-like porous membrane. That is, when filtering a liquid with a high SS content, the holes may be blocked by the SS content and cannot be filtered because of the small diameter of the holes in the hot-melt adhesive portion.

Further, when filtering a high-viscosity liquid, the pressure loss in the longitudinal direction of the hollow fiber-like porous membrane increases when the diameter of the pores of the hot-melt adhesive portion is small, so the filtration pressure that is effectively used decreases in the longitudinal direction. However, the amount of permeation also decreases, and the economical efficiency of the filter element also decreases, which is a practical disadvantage.

As a result of repeated studies, the present inventors have completed a method of performing hot melt adhesion without reducing the inner cross-sectional area of the hollow fiber-like porous membrane and without changing the hollow portion cross-sectional shape of the hollow fiber-like porous membrane. .

(Means for Solving the Problems) The present invention provides a semi-extracted hollow fiber-like porous membrane which is made of a thermoplastic resin and contains an inorganic fine powder in any part other than the outer surface. 50 to 20 of the melting point of the thermoplastic resin
Covering with a tubular material made of a thermoplastic resin having a melting point of 0%, heating the end portion at a temperature equal to or higher than the melting point of the resin for the porous membrane material, and thermally adhering adjacent end portions to each other. The first feature is that the inorganic fine powder is extracted from the porous film.

Further, according to the present invention, the end portion covered with the tubular material is inserted into a sleeve made of a thermoplastic resin having a melting point of 50 to 200% of the melting point of the resin for the porous membrane material and then heated to be adjacent to each other. The second feature is that the end portions and the end portions and the sleeve are hot melt-bonded to each other.

(Operation) Hereinafter, the features of the present invention will be specifically described together with the operation thereof.

The hollow fiber microfilter referred to in the present invention has an average pore size of
A film having a thickness of 0.05 to 1 μm, an outer diameter of 8 mm or less, preferably 2 mm or less, and a film thickness of 5 μm or more, preferably 30 to 500 μm is suitable. The pore size of the membrane was measured by ASTM F316-70.
The porosity of the film is preferably 30 to 90%, particularly 55 to 85%. The porosity (Pr) as used herein has the same meaning as is generally used and is defined by the following equation.

Pr = (1−Pb / Pa) × 100 (%) where Pa is the density of the membrane material without voids, and Pb is the weight of the membrane divided by the volume of the wall membrane.

Further, as the thermoplastic resin constituting the hollow fiber microfilter, PTFE (polytetrafluoroethylene), FE
P (tetrafluoroethylene-hexafluoropropylene copolymer resin), PFA (tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer resin), ETFE
(Ethylene-tetrafluoroethylene copolymer resin), PV
Fluororesin such as DF (polyvinylidene fluoride); Polyolefin such as polyethylene and polypropylene; Polyvinyl chloride; Nylon; Polyester; Polysulfone; Polyether sulfone; PEEK (Polyether ether ketone)
Etc. can be mentioned.

As the inorganic fine powder, fine particles having a specific surface area of 50 to 500 m ² / g and an average primary particle diameter of 0.005 to 0.5 μm are preferable, and the material is silicic acid, calcium silicate, aluminum silicate,
Magnesium oxide, alumina, calcium carbonate, kaolin, clay, diatomaceous earth, etc. are used. Of these, finely divided silicic acid is particularly preferable. The average primary particle diameter is the average value of the diameters of the fine powder single particles, and is not the diameter of the aggregate (secondary particles) of the single particles. The average primary particle diameter can be measured by an electron microscope.

When the inorganic fine powder is subsequently sufficiently solvent-extracted from the hollow fiber-like porous membrane containing the inorganic fine powder, it becomes a microfilter.

The hollow fiber-like porous membrane in the semi-extracted state in the present invention is a hollow fiber (semi-extracted fiber) in which the inorganic fine powder is not completely extracted and a certain proportion of the inorganic fine powder remains. However,
It is porous even when fine powder is not extracted.

A hollow fiber from which no fine powder is extracted or a hollow fiber from which the fine powder is not sufficiently extracted from the outer peripheral portion does not melt-bond sufficiently to the tube even when heated. Further, when the extraction is excessive, the inner diameter of the hollow fibers is significantly shrunk by heating, and even if the hollow fibers can be melt-bonded to each other, they will not be practical.

On the other hand, the appropriately extracted semi-extracted yarn does not shrink in diameter due to heating because it contains the inorganic fine powder in the portion other than the outer surface. Therefore, it can be directly used for hot melt adhesion without using a support for suppressing a decrease in inner diameter due to shrinkage. A semi-extraction film containing fine powder in the portion excluding the outer peripheral portion is preferable.

As the thermoplastic resin forming the tubular material and the sleeve, any thermoplastic resin having a melting point of 50 to 200%, preferably 80 to 150% of the melting point of the hollow fiber membrane material resin can be used, but the hollow fiber membrane It is more preferable that the material is the same as the material or the melting points are almost the same. If the melting point of the tubular material or the like is out of the range of 50 to 200%, the physical properties of the hollow fiber membrane are so different from each other that sealing is insufficient.

The melting point as used herein means a melting point in the case of a crystalline resin and a glass transition point in the case of an amorphous resin. Examples of the thermoplastic resin used include PTFE (melting point 327 ° C); FEP
(Melting point 250 to 295 ° C.); PFA (melting point 302 to 310 ° C.); ETFE (melting point 270 ° C.); polyethylene (melting point 108 to 135 ° C.); polysulfone (glass transition point 190 ° C.) and the like.

According to the production method of the present invention, first, a semi-extracted yarn is made by extracting at least the inorganic fine powder in the outer peripheral portion from the main extracted yarn in which the inorganic fine powder is not extracted. For example, when the inorganic fine powder is silica, an aqueous solution of sodium hydroxide may be used to extract the inorganic fine powder, and the extraction solvent for the inorganic fine powder is generally used. Extraction time is preferably 5 minutes to 2 hours, and even 10
Minutes to 30 minutes are desirable.

After the extraction process, the semi-extracted yarn is washed and dried. At least the entire outer peripheral portion of the portion near the end of each semi-extracted yarn where heat fusion is performed, has the same material as the hollow fiber porous membrane, or has a melting point of 50 to 200% of the melting point of the hollow fiber membrane resin. Attach a tube made of plastic resin.

The tube to be mounted should have an inner diameter larger than the outer diameter of the semi-extracted yarn and not more than 4 times the outer diameter of the semi-extracted yarn, and the inner diameter is preferably 1.1 to 1.4 times the outer diameter of the semi-extracted yarn. .
If a heat shrinkable tube is used, the inner diameter of the tube may be 1.1 to 9 times the outer diameter of the semi-extracted yarn.

Next, a plurality of semi-extracted yarns are bundled together and fixed at the portions where the tubular material is attached. When a heat-shrinkable tube is used, the tube is shrunk by heating before bundling. For fixing, a heat-shrinkable tape may be wrapped, or a bundle made of the same material as the tube material may be packed into a bundle and the sleeve may be tightened from the outside with a jig. When packed in a sleeve, the outer diameter of the bundle is
It is necessary to be 80% or more, more preferably 90% or more.

Place the tube mounting part of the fixed bundle in the furnace and heat it,
Perform hot melt adhesion. The heating temperature needs to be 5 to 100 ° C. higher than the melting point of the raw material polymer of the hollow fiber-like porous membrane, and is preferably 10 to 30 ° C. higher. The heating time is preferably 30 minutes to 2 hours, more preferably 40 minutes to 1 hour. After the heating is finished, it is taken out of the furnace and gradually cooled.
Further, if the other end of the bundle is heat-melt-bonded by the same method, both ends can be liquid-tightly heat-melt-bonded to form a bundle. Moreover, if the other end is sealed, it is possible to create a bundle in which only one end is heat-melt-bonded.

When a part of the end of the bundle is cut and opened, a filter element is obtained. After hot-melt adhesion, the inorganic fine powder is completely extracted again with a solvent to prepare a hollow fiber microfilter. It is better to extract after opening the end faces of the bundle. At this time, if light coloring due to impurities can be seen, the impurities can be removed by immersing in an aqueous solution of sodium hypochlorite or hydrogen peroxide solution for treatment.

When attaching a tube to the end of the bundle, it may be done at the same time when the semi-extraction system and the tubular material are heat-melt-bonded to each other, or once the ends of the bundle are melt-bonded and the sleeve is melt-bonded. May be.

In the present invention, by arranging the tubular material at the end of the semi-extraction system, without reducing the inner diameter of the hollow fiber microfilter, a filter element comprising a hollow fiber microfilter part used for filtration and a hot melt adhesive part Can be created. Further, by using the sleeve together, a filtration element having a sufficient filtrate space when mounted on the case can be obtained.

(Example 1) A hollow fiber-like porous body of ethylene-tetrafluoroethylene copolymer having a length of 350 mm, an outer diameter of 1.2 mm and an inner diameter of 0.7 mm produced by the method described in JP-A-62-106808. Using.

First, a non-extracted thread from which silicon dioxide is not extracted is immersed in a 10% sodium hydroxide aqueous solution at 40 ° C. for 10 minutes to extract silicon dioxide, thereby producing a semi-extracted thread. The outer diameter of one end of this semi-extracted yarn is 1.3 mm, the outer diameter is 2.0 mm, and the length is 60 mm.
A tube of tetrafluoroethylene copolymer was attached. Then, the tube attachment parts were bundled together and bundled into 500 pieces, and a Teflon seal tape was wrapped and fixed. Next, put the tube mounting part of the bundle in the furnace and heat at about 280 ° C for 30 minutes,
After that, it was gradually cooled. Further, the other end was also heat-melt-bonded by the same method, and the bonded part was partially cut to open both ends. Remove the tape and apply 3% to a 20% aqueous sodium hydroxide solution at 80 ° C.
It was immersed for a period of time to completely extract silicon dioxide. In this way, a filter element having both ends thermally fused and bonded was prepared. Further, 30 filter elements were prepared by the same method. When water was passed through these filter elements and inspected for leaks due to scratches or cracks in the vicinity of the hot-melt adhesive portion, none of the filter elements leaked. In addition, the diameter of the opening on the end face of the adhesive part is about 0.
It was 7 mm. In the obtained transmissive element, there was no reduction (constriction) in the outer periphery of the microfilter bundle at the fusion-bonded portion, and the microfilters were bonded and fixed in a state in which they were aligned substantially in parallel.

(Comparative Example 1) A hollow fiber-like porous material of the same ethylene-telorafluoroethylene copolymer used in Example 1 was immersed in a 40% aqueous sodium hydroxide solution at 70 ° C for 6 hours to completely remove silicon dioxide. A hollow fiber microfilter was obtained by extraction. Using this microfilter, a filter element was prepared by the method described in JP-A-63-59311. In other words, the microfilter 100 whose edges were heat treated in advance at 280 ° C
The books were heat-melt-bonded at 280 ° C with a pressure difference inside and outside.

We made 30 of these filter elements and inspected them for leaks due to scratches and cracks in the vicinity of the hot-melt adhesive joint by passing water, and found that 10 or more leak elements were 4 or less than 10 filter elements. There were seven filtration elements in which this occurred.

(Example 2) A sleeve made of an ethylene-tetrafluoroethylene copolymer having a maximum clearance with the outer diameter of 0.2 mm or less, which is bundled together with the tube mounting portions (length 60 mm, thickness 5 m).
A filter element of a microfilter having melt-bonded ends was obtained in the same manner as in Example 1 except that the filter element was inserted into m).
The heating time in the furnace was 45 minutes.

The diameter of the opening at the end face of the bonded portion of each of the obtained filter elements was about 0.7 mm.

(Effects of the Invention) In the conventional method, since the hollow fiber microfilters are directly bound to form the hot-melt adhesive portion, excessive force is applied to the hollow fiber microfilters, cracks and the like easily occur, and the reliability of the filtration element is reduced. drop down. On the other hand, the hollow fiber-shaped microfilter prepared by the method of the present invention has the same inner diameter of the opening as the inner diameter of the microfilter and does not cause a decrease in filtration performance, and does not cause shrinkage in the welded portion. No damage, no clogging during filtration. In addition, hot melt adhesion can be performed without preheating.

Claims (2)

[Claims] 1. A semi-extracting hollow fiber-like porous membrane which is made of a thermoplastic resin and contains an inorganic fine powder in a portion other than the outer surface, and the outer peripheral portion of the end portion has a melting point of 50 to 50 ° C. of the thermoplastic resin.
Covering with a tubular material made of a thermoplastic resin having a melting point of 200%, heating the end portion at a temperature equal to or higher than the melting point of the porous membrane material resin, and heat-melt adhering the adjacent end portions to each other, and thereafter, A method for producing a hollow fiber-shaped microfilter bundle having at least one end bonded, which comprises extracting inorganic fine powder from a porous membrane. 2. An end covered with a tubular material is inserted into a sleeve made of a thermoplastic resin having a melting point of 50 to 200% of the melting point of the resin for the porous membrane material, and then heated to adjoin the ends. The method for producing a hollow fiber-shaped microfilter bundle according to claim 1, wherein the parts and the ends and the sleeve are heat-melt-bonded.