JPH06170181A - Hollow fiber membrane module and production thereof - Google Patents

Abstract

PURPOSE:To separate an org. solvent at relatively high temp. by a hollow fiber membrane module. CONSTITUTION:A least one end part of the bundle of hollow fiber membranes is immersed in a resin compsn. melt consisting of 5-99wt.% of low density polyethylene wax and 95-1wt.% of a low density olefin polymer with a melt index of 50 or more to be sealed and fixed to a casing. Polyethylene is contained in the wax and the polymer. The density of the wax is 0.94g/cm<2> or less and the mol.wt. thereof by a viscosity method is 20000 or less. When the wax and the polymer are together used, a hollow fiber membrane module relatively high in the adhesion to hollow fiber membranes and heat resistance and having a sealed and fixed part excellent in solvent resistance is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hollow fiber membrane module having excellent solvent resistance and useful for efficiently membrane-separating a fluid to be treated and a method for producing the same.

[0002]

2. Description of the Related Art In recent years, semipermeable membranes having various separation characteristics such as reverse osmosis type, ion exchange type, pervaporation type and ultrafiltration type have been developed. These semipermeable membranes are modularized in the form of, for example, a flat membrane, a spiral, or a hollow fiber.

Among these modules, the hollow fiber membrane module has an advantage that the membrane surface area per unit volume of the device can be increased, and the device can be downsized and the cost can be reduced. Therefore, the hollow fiber membrane module is used for medical applications,
It is used in a wide range of fields such as precision electronics industry, food industry, and physics and chemistry.

In the hollow fiber membrane module, usually, the bundled hollow fiber membranes are housed in a casing, and the hollow fiber membranes and between the hollow fiber bundles and the casing are sealed and fixed at a casing end or the like. .

On the other hand, in the separation operation by the hollow fiber membrane module, a fluid is supplied from the primary side to the hollow fiber membrane under high pressure, and a predetermined component in the fluid is selectively permeated to the secondary side through the hollow fiber membrane, Concentrates the non-permeable components. Also, in order to increase the permeation efficiency, it is advantageous to supply the heating fluid.
Since pressure history and heat history act on such a hollow fiber membrane module, particularly the sealing and fixing portion, the module is required to have a high sealing property between the hollow fiber bundle and the case. As a material for sealing and fixing the hollow fiber bundle, an epoxy resin-based adhesive and a urethane resin-based adhesive have been widely used.

However, in the module produced by using these adhesives, the adhesives swell or crack during the chemical treatment at a high temperature such as the filtration of the organic solvent, resulting in the adhesiveness, and thus the sealing. Sex decreases. Therefore, the type of fluid to be processed is limited. Further, when the fluid to be treated is subjected to membrane separation under high temperature and high pressure, the fluid to be treated leaks from the sealing and fixing portion within a short time, and the membrane separation operation cannot be continued.

Japanese Unexamined Patent Publication No. 61-129006 discloses a technique for vulcanizing rubber having excellent chemical resistance to seal the end of the hollow fiber bundle. However, in order to vulcanize the rubber, a high temperature treatment of 160 ° C. or higher is required. for that reason,
A hollow fiber membrane having low heat resistance cannot be used, and only a hollow fiber membrane made of a specific material can be used. Moreover, the manufacturing process of the module is complicated.

Japanese Unexamined Patent Publication (Kokai) No. 3-221128 discloses a technique of adhering and fixing the ends of hollow fiber bundles with an adhesive resin containing, as at least one component, a polyolefin copolymerized with unsaturated carboxylic acids. However, a polyolefin obtained by copolymerizing an unsaturated carboxylic acid alone has low heat resistance and cannot be used for membrane separation at high temperature. Furthermore, the compatibility with other polyolefins is poor, and it is difficult to provide stable membrane separation for a long period of time.

[0009]

Therefore, an object of the present invention is to provide a hollow fiber bundle in which a hollow fiber bundle is firmly adhered and fixed, has excellent solvent resistance, and can be stably subjected to membrane separation for a long period of time. It is to provide a membrane module and a manufacturing method thereof.

Another object of the present invention is to provide a hollow fiber membrane module capable of performing membrane separation at a relatively high temperature even with an organic solvent, and a method for producing the same.

[0011]

As a result of intensive studies, the present inventors have found that the above problems can be solved by sealing and fixing a hollow fiber bundle to a casing using a resin composition containing a specific polyolefin, and completed the present invention. did.

That is, the hollow fiber membrane module of the present invention is a resin composition containing a low-density polyolefin wax and a low-density olefin polymer having a melt index of 50 or more, and the ends of the hollow fiber membrane bundles are sealed and fixed. ing.

In the method of the present invention, at least one end of the hollow fiber membrane bundle is immersed in a molten resin composition containing a low density polyolefin wax and a low density olefin polymer having a melt index of 50 or more. Then, the hollow fiber membrane module is manufactured by sealing and fixing.

The present invention will be described below in detail with reference to the accompanying drawings as needed.

FIG. 1 is a schematic sectional view showing an example of a hollow fiber membrane module.

In this example, the hollow fiber membrane module comprises a casing 1 having outlets 2a, 2b through which permeated liquid or permeated gas selectively permeated on the permeate side of the hollow fiber membrane, that is, the secondary side. A hollow fiber bundle 3 composed of a plurality of hollow fiber membranes housed in the casing 1 and lids 4a and 4b for closing both ends of the casing 1 are provided. Both ends of the hollow fiber bundle 3 are adhesively sealed by the sealing fixing portions 5a and 5b in a state where the end faces of the hollow fiber membrane are open.

A supply port 6a for supplying the liquid to be treated to the primary side of the hollow fiber membrane is formed in one cover 4a, and a discharge port 6b for discharging the concentrated liquid is formed in the other cover 4b. Has been formed. In addition, the casing 1 and the sealing fixing portion 5a,
An elastic O-ring 7 is provided at the intersection of the lid 5a and the lid 4a, 4b.
a and 7b are arranged in a pressed state to seal the intersection.

The sealing and fixing portions 5a and 5b are made of low density polyolefin wax and melt index 50.
It is formed of a resin composition containing the above low-density olefin polymer.

In such a hollow fiber membrane module, since the sealing and fixing portions 5a and 5b are formed of the olefin resin, the solvent resistance is extremely high. Therefore, various organic solvents other than gas and water can be efficiently treated. Moreover, since the sealing and fixing portions 5a and 5b are formed of a resin composition containing the wax and the polymer instead of a single olefin-based polymer, there is practically no problem in adhesive sealing and heat resistance. And has strength.

The low-density polyolefin wax includes
Density 0.94 g / cm ² or less, preferably 0.91
0.94 g / cm ³ or so, molecular weight 2000 by viscometry
A polyolefin wax of 0 or less, preferably 2500 to 15000, and more preferably 5000 to 12,500 is included.

In the present invention, a low density olefin polymer having a melt index of 50 or more, preferably 50 to 200, more preferably 50 to 150 is used together with the low density polyolefin wax.

The melt index is ASTM
2 measured according to the test method specified in D1238
It means the amount (g) of the melt at 190 ° C. extruded through a specific orifice in 10 minutes when a load of 160 g is applied onto the piston. Generally, the higher the melt index, the lower the molecular weight of the polymer.

As the low density olefin polymer,
Density 0.94 g / cm ² or less, preferably 0.91
About 0.94 g / cm ³ , molecular weight of 200 by viscosity method
00 or more polyolefins can be used.

The low density polyolefin wax and the low density olefin polymer are often composed mainly of ethylene. The low-density polyolefin wax and the low-density olefin polymer may be a copolymer of polyethylene, ethylene and another olefin, for example, propylene, butylene, 4-methylpentene-1, etc., vinyl acetate, vinyl propionate. It may be partially modified by copolymerization with a vinyl ester or the like. When the wax and the olefin polymer are ethylene copolymers, the proportion of the monomers copolymerized with ethylene is, for example, 1 to 40% by weight, preferably 5 to 3%.
It is about 0% by weight. Preferred low density polyolefin waxes include, for example, polyethylene waxes, and preferred low density olefin polymers include, for example:
An ethylene-butene copolymer and the like are included.

The crystallinity of the low-density polyolefin wax such as polyethylene wax and the low-density olefin polymer such as polyethylene by X-ray analysis is, for example, about 60 to 75%.

Generally, although polyolefins are excellent in solvent resistance, they are said to have a large heat shrinkage ratio and are inferior in heat resistance, adhesiveness to hollow fiber membranes, strength and the like. However, when the specific wax and the olefin polymer are used in combination, a module having no practical problem can be obtained.

More specifically, as the degree of crystallinity of the polyolefin increases, the heat shrinkage generally increases, so that a gap is likely to be formed between the polyolefin and the hollow fiber, and the adhesive sealing property deteriorates. However, when used in combination with the low-density polyolefin wax, heat shrinkage can be suppressed and the adhesive sealing property can be improved.

The wax generally has low heat resistance.
However, a low-density polyolefin wax, for example, a wax having a molecular weight of about 4000 by the viscosity method has a softening point of 1
Since it is about 20 ° C., it can be used without any trouble in the separation treatment at 100 ° C. or less. Furthermore, when an olefin polymer is used in combination with the wax, heat resistance can be increased.

Since an olefin polymer having a melt index of 100 or less generally has a high melt viscosity, it is difficult to uniformly immerse and seal the hollow fiber bundle even when melted at 160 ° C. However, if an olefin polymer having a melt index of 50 or more is used in combination with the wax,
While maintaining the excellent properties of low density olefin polymer,
The melt viscosity can be reduced, and the adhesive sealing property with the hollow fiber bundle can be improved.

Further, when an olefin polymer is used,
Even if the adhesiveness is improved by the surface treatment of the hollow fiber membrane, heat shrinkage causes a slight gap at the interface between the polyolefin and the hollow fiber membrane. However, when used in combination with the wax, the adhesive sealing property with the hollow fiber bundle can be enhanced.

Furthermore, as the crystallinity of the olefin polymer increases, the solvent resistance generally improves. on the other hand,
Polyolefin wax also has relatively high solvent resistance. For example, even with a polyolefin wax having a low crystallinity of 60% and a molecular weight of 7200, ethyl acetate: acetic acid: water =
200 at 80 ° C. in a solvent such as 6: 2: 2: (weight ratio)
Even if it is immersed for 0 hours, the weight change is about 5%, and it shows solvent resistance which is practically no problem. Therefore, when the wax and the olefin polymer are used in combination, a higher solvent resistance than the wax can be secured.

Furthermore, although the strength of the olefin wax alone is low and cracks may occur due to shrinkage during cooling, when combined with the above-mentioned specific olefin polymer, the strength can be increased and the occurrence of cracks can be prevented.

The proportion of the low-density polyolefin wax and the low-density olefin polymer is such that the melt viscosity becomes low, so that practical strength can be obtained, for example, low-density polyolefin wax / low-density olefin polymer = 5.
It can be appropriately selected within the range of 99/95 to 1 (wt%), but it is preferable that the proportion of the low density polyolefin wax is large. The preferable ratio is, for example, low density polyolefin wax / low density olefin polymer = 25 to 9
5/75 to 5 (wt%), preferably 50 to 95/50
It is about 5 (% by weight). If the proportion of the wax is less than 5% by weight, the heat shrinkage rate and melt viscosity are large, and the adhesive sealing property tends to be lowered. easy.

The resin composition may optionally contain various additives such as antioxidants such as antioxidants and fillers.

Examples of the polymer constituting the hollow fiber membrane are polyethylene, ethylene-propylene copolymer, polypropylene, poly-4-methylpentene-1.
Olefin-based polymers such as; polytetrafluoroethylene, polychlorotrifluoroethylene, polyvinylidene fluoride, tetrafluoroethylene-ethylene copolymers, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymers and other fluorine-containing polymers;
Cellulose-based polymers such as cellulose acetate; polyvinyl chloride; acrylonitrile-based polymers; acrylic-based polymers such as polymethylmethacrylate and acrylonitrile-methylmethacrylate copolymers; silicone resins; polyamides; polyimides; polyethersulfones; polysulfones; polyphenylene oxides; Examples include polyphenylene sulfide; polyarylate; polyetheretherketone; polyetherimide; polycarbonate; polyvinyl alcohol-based polymers.

Preferred hollow fiber membranes include porous membranes. Such a porous hollow fiber membrane has a high adhesive surface sealing property due to the resin composition due to an increase in the adhesive surface area due to the rough surface and anchors.

The surface roughness and pore size of the hollow fiber membrane are not particularly limited, and can be selected according to the separation method and the type of separation component. If necessary, the hollow fiber membrane may be subjected to surface treatment such as treatment with an organic solvent, plasma discharge treatment, corona discharge treatment, ozone treatment, and the like, and then subjected to adhesive sealing.

The shape of the casing can be selected according to the application, etc., but is usually cylindrical, and often has a nozzle-like supply port or the like on its side portion. The material of the casing is
It can be selected according to the fluid to be treated and the type of separated component, and may be, for example, plastic such as polyvinyl chloride, polycarbonate, (meth) acrylic polymer, polysulfone, polyether sulfone; metal such as stainless steel. . The casing is often made of polysulfone, polyether sulfone, stainless steel, or the like in terms of solvent resistance.

The casing may be capable of reducing the pressure on the permeate side through the outlet, or may be disposed in a chamber capable of reducing the pressure, if necessary. Further, contrary to FIG. 1, the fluid to be treated may be supplied from the outlet of the casing to let the permeate component flow out from the opening of the hollow fiber membrane.

In the hollow fiber membrane, at least one end face of both end faces may be open. For example, one end of the plurality of hollow fiber membranes may be adhesively sealed with a sealing and fixing part in a state where the end faces are open, and the hollow portion of the other end of the hollow fiber membrane may be closed. Further, both ends of the plurality of hollow fiber membranes may be converged, and the converging portion may be adhesively sealed in a state where the end faces of the hollow fiber membranes are open.

Further, in the membrane module, at least one end of the plurality of hollow fiber membranes may be adhered and sealed without being equipped with a casing, and the hollow fiber membranes may be attachable to the case. In this case, the membrane module can be mounted in the case in a cartridge type. In a preferred hollow fiber membrane module, at least one end of the plurality of hollow fiber membranes is often adhesively sealed to the casing by the sealing and fixing portion.

The fluid to be treated can be selected according to the separation characteristics of the hollow fiber membrane, and fluids containing gas or liquid such as air, oxygen and nitrogen can be used. As the liquid, water; alcohols such as methanol, ethanol and isopropyl alcohol;
Ethers such as diethyl ether, dipropyl ether and butyl ether; esters such as methyl acetate, ethyl acetate, butyl acetate and ethyl propionate; ketones such as acetone and methyl ethyl ketone; organic acids such as acetic acid, acetic anhydride and propionic acid; Amines such as diethylamine and aniline; Aliphatic hydrocarbons such as hexane and octane; Aromatic hydrocarbons such as benzene and toluene; Alicyclic hydrocarbons such as cyclohexane; Halogen such as chloroform, carbon tetrachloride and trichloroethylene Chemical hydrocarbons and the like can be mentioned.

The hollow fiber membrane module shown in FIG. 1 can be manufactured as follows.

A plurality of hollow fiber membranes are bundled together, and if necessary, the openings on the end faces of the hollow fiber membranes are sealed by a sealing means such as an adhesive and housed in a casing. One end of the hollow fiber bundle is immersed in the molten resin composition and naturally cooled to seal and fix it. Similarly, the other end of the hollow fiber bundle is similarly sealed and fixed, and the end of the sealing and fixing part is cut to open the end face of the hollow fiber membrane. When a gap is created between the inner wall of the casing and the sealing and fixing portion, it can be sealed with a sealing member such as an elastic O-ring as described above.

When the hollow fiber membrane module is, for example, the cartridge type module, it is not necessary to seal and fix the end portion of the hollow fiber bundle to the casing.

The melting temperature of the resin composition can be selected within a range that does not hinder the sealing and fixing of the hollow fiber bundle, but the higher the melting temperature, the greater the shrinkage ratio after cooling and solidification. for that reason,
In order to reduce the heat shrinkage of the sealing and fixing portion, it is advantageous that the melting temperature of the resin composition is low. The resin composition has a softening point of 10 to 50 from the softening point of the wax and polymer mixture.
It is preferable to melt at a temperature as high as 20 ° C, preferably 20 to 40 ° C. By immersing the hollow fiber bundle in the resin composition melted at such a temperature, the simple operation of natural cooling,
It is possible to prevent a gap from being generated at the interface between the sealing and fixing portion and the hollow fiber membrane.

The membrane separation module of the present invention can be used for membrane separation of liquid, membrane separation of gas component from liquid, and the like.

[0048]

According to the hollow fiber membrane module and the method for producing the same of the present invention, the end portion of the bundle of hollow fiber membranes is sealed and fixed by the resin composition containing the specific wax and the polymer. The bundle can be firmly adhered and fixed, and it has excellent solvent resistance, and can stably perform membrane separation of the fluid to be treated for a long period of time.

Further, although the sealing and fixing part is made of a resin composition of wax and an olefin polymer, it has relatively high heat resistance, and even an organic solvent can perform membrane separation at relatively high temperature.

[0050]

EXAMPLES The present invention will be described in more detail based on the following examples.

Example 1 A polyacrylonitrile-based copolymer hollow fiber membrane having an inner diameter of 500 μm and an outer diameter of 800 μm was placed in a 1N-NaOH aqueous solution for 8 hours.
After hydrolyzing at 0 ° C. for 55 minutes to convert a part of the nitrile group into a carboxyl group, a polyion complex was formed with an ionene type polycation.

Low-density polyolefin wax (Mitsui Petrochemical Co., Ltd., Mitsui High Wax 720P, density 0.9)
80 parts by weight of ² g / cm ² , molecular weight of 7200, and low density polyolefin [ethylene (80% by weight) -butene (2
0% by weight) copolymer, manufactured by Nippon Unicar Co., Ltd., MG-3
65, density 0.93 g / cm ² , melt index 1
10] 20 parts by weight were mixed and melted at 135 ° C. in a mold.

The hollow fiber membranes are uniformly bundled and the tip is sealed,
It was housed in a cylindrical casing made of polyethersulfone. One end of the hollow fiber bundle was immersed in the heat-melted resin resin composition to cool and solidify, and then the other end was similarly sealed and fixed. Next, both ends of the hollow fiber bundle were cut and opened to prepare a module.

Then, when a 99% by weight aqueous ethanol solution was supplied to the hollow fiber membrane module at 60 ° C., separation performances of separation coefficient α = 2450 and permeation coefficient Q = 75 g / m ² · hr were exhibited. When the above operation was performed for 7 consecutive days, no abnormality was found in the sealing and fixing portion.

Example 2 Acrylonitrile having an inner diameter of 500 μm and an outer diameter of 800 μm /
A hollow fiber membrane made of a methyl methacrylate copolymer (molar ratio = 95/5) was used. Low-density polyolefin wax (Mitsui Petrochemical Co., Ltd., Mitsui High Wax 720P,
90 parts by weight of density 0.92 g / cm ² , molecular weight 7200 and low density polyolefin (manufactured by Nippon Unicar Co., Ltd., low density polyethylene NUC-8360, density 0.92 g / c)
m ² and 10 parts by weight of melt index 65) were mixed and melted in a mold at 140 ° C., and a hollow fiber membrane module was produced in the same manner as in Example 1.

80% by weight of the hollow fiber membrane module
When the acetic acid aqueous solution was supplied at 80 ° C., the separation coefficient α = 1
The separation performance was 850 and the permeation coefficient Q was 330 g / m ² · hr. When the above operation was performed for 7 consecutive days, no abnormality was found in the sealing and fixing portion.

Example 3 98% by weight was added to the hollow fiber membrane module prepared in Example 2.
When the toluene solution was supplied at 80 ° C, the separation coefficient α
= 1650, and the permeation coefficient Q = 250 g / m ² · hr. Even if the above operation was carried out continuously for 7 days, no abnormality was found in the sealing and fixing part.

Comparative Example 1 Using the hollow fiber membrane of Example 1, as a sealing resin, a wax (Mitsui Petrochemical Co., Ltd., Mitsui High Wax 800P,
80 parts by weight of density 0.97 g / cm ² , molecular weight 8000 and polyolefin (manufactured by Nippon Unicar Co., Ltd., MG-36)
5, density 0.93 g / cm ² , melt index 11
0) A mixture with 20 parts by weight was used. The mixture was melted in a mold at 145 ° C. and a hollow fiber membrane module was produced in the same manner as in Example 1.

When a 99% by weight aqueous ethanol solution was supplied to the hollow fiber membrane module at 60 ° C., the separation coefficient α = 85 and the permeation coefficient Q = 210 g / m ² · hr, showing low separation performance. Further, when the cause of the decrease in separation performance was investigated, a gap was found between the hollow fiber membrane and the sealing and fixing part.

Comparative Example 2 Using the hollow fiber membrane of Example 1, as a sealing resin, a polyolefin wax (Mitsui Petrochemical Co., Ltd., Mitsui High Wax 1100P, density 0.97 g / cm ² , molecular weight 11) was used.
000) was used. When the wax was melted in a mold at 145 ° C., one end of the hollow fiber bundle was immersed and naturally cooled, cracks were generated in the resin at the sealing and fixing part.

Comparative Example 3 100 parts by weight of an epoxy resin (Okaka Shell Epoxy Co., Ltd., Epicoat 828) and 25 parts by weight of a curing agent (Okaka Shell Epoxy Co., Ltd., Epicure U) were mixed and sealed. The agent was prepared. The hollow fiber membrane of Example 2 was uniformly bundled and the tip was sealed, the hollow fiber bundle was housed in a cylindrical casing made of polyethersulfone, and both ends were sealed and fixed with the above-mentioned sealant. In order to open the hollow fiber membrane, both ends were cut to produce a hollow fiber membrane module.

Then, when an 80 wt% acetic acid aqueous solution was supplied to the hollow fiber membrane module at 80 ° C., the separation coefficient α =
The separation performance was 1730 and the permeation coefficient Q was 300 g / m ² · hr. When the above operation was continued, after 24 hours, a crack occurred in the sealing and fixing part and the liquid to be treated leaked.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing an example of a hollow fiber membrane module.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Casing 3 ... Hollow fiber bundle 4a, 4b ... Lid 5a, 5b ... Sealing fixing part

Claims (5)

[Claims] 1. A hollow fiber membrane module comprising a resin composition containing a low density polyolefin wax and a low density olefin polymer having a melt index of 50 or more, and at least one end of a bundle of hollow fiber membranes is sealed and fixed. . 2. The hollow fiber membrane module according to claim 1, wherein at least one end of the bundle of hollow fiber membranes is sealed and fixed to the casing. 3. The resin composition has a density of 0.94 g / cm ^2.
Hereinafter, a low-density polyolefin wax having a molecular weight of 20000 or less and a melt index of 50 to 20 by a viscosity method
The hollow fiber membrane module according to claim 1, comprising 0 low density olefin polymer. 4. The ratio of the low density polyolefin wax to the low density olefin polymer is 5 to 99/95 to 1.
(% By weight) The hollow fiber membrane module according to claim 1. 5. At least one end of the bundle of hollow fiber membranes is immersed in a molten resin composition containing a low-density polyolefin wax and a low-density olefin polymer having a melt index of 50 or more, and fixed by sealing. Method for manufacturing hollow fiber membrane module.