JP5737318B2 - Method for producing fiber-reinforced porous hollow fiber membrane - Google Patents

Description

  The present invention relates to a method for producing a fiber-reinforced porous hollow fiber membrane. More specifically, the present invention relates to a method for producing a fiber-reinforced porous hollow fiber membrane having excellent mechanical strength.

  Porous hollow fiber membranes are used in various fields such as water purification treatment by membrane filtration, wastewater treatment, dehumidification or humidification.

  Water purification and wastewater treatment using membrane filtration has been widely used in the water treatment field in recent years because it is easier to maintain and manage operation and has better quality compared to conventional filtration methods for coagulation and precipitation. It has been. For example, the membrane used in the membrane reactor process (MBR), which combines activated sludge treatment and membrane separation treatment, requires high strength, durability, and chemical resistance. A prepared polyvinylidene fluoride [PVDF] membrane is often used.

However, the PVDF membrane prepared by the thermally induced phase separation method has a strength of about 8 to 22 MPa, and among them, many are about 11 MPa in practical use, although some strength is shown, Compared with a membrane prepared by a non-solvent induced phase separation method, it does not necessarily have sufficient strength. In addition, the thermally induced phase separation method has a complicated process and requires cleaning with a large number of solvents, so that it is difficult to say that it is expensive and environmentally friendly.

On the other hand, a membrane module (membrane area of about 10 to 100 m ² ) with a structure in which polysulfone, PVDF, etc. prepared using a non-solvent induced phase separation method are fixed in a resin case with an adhesive is also used for wastewater treatment and water purification treatment. Many are used. Such a membrane module is supplied with water in an amount of several tens of liters to several hundreds of liters per minute. At that time, since the chemical cleaning or the peristaltic cleaning for the purpose of recovering the flow rate is periodically performed, the hollow fiber membrane may be broken at the time of use or cleaning.

Further, the method of dehumidifying or humidifying by the hollow fiber membrane method is not only maintenance-free, but also has many advantages such as not requiring a power source for driving. As such a dehumidifying film or humidifying film, a film-forming resin material such as polyimide, polysulfone, or polyphenylsulfone is used ( for example, Patent Document 1) . Dividing wet film using these materials, although used in many industrial fields, for the absolute strength of the membrane to a porous weak, which is used by passing a large amount of gas depending on the application, using there is a possibility such at the hollow fiber membrane is broken. On the other hand, in recent years, humidification membranes are often used to humidify diaphragms of fuel cell stacks, but in this case as well, for example, a large amount of air of about 4000 NL / min flows in in-vehicle applications. Therefore, there is a risk of the hollow fiber membrane being cut.

  A porous membrane in which reinforcing fibers are buried in a hollow fiber membrane has been proposed as a means for preventing the hollow fiber membrane from being broken and improving the mechanical strength (Patent Document 2). Here, when the reinforcing fiber is buried in the hollow fiber membrane and the reinforcing fiber is extruded together with the spinning stock solution from the outer nozzle of the double annular nozzle to produce a porous hollow fiber membrane, the spinning discharged from the nozzle In the process of solidifying the stock solution into a membrane, there is a tendency for the reinforcing fibers to move outside the hollow fiber membrane, resulting in a portion that is not partially buried in the hollow fiber membrane and insufficiently reinforced, resulting in increased strength. Variations may occur and thread breakage may occur during use or cleaning.

Japanese Patent Application Laid-Open No. 2004-290751 JP 2002-166141 A

  An object of the present invention is a porous hollow fiber membrane in which reinforcing fibers are completely buried in a hollow fiber membrane, and the fiber reinforced porous material has improved mechanical strength without impairing the original function of the porous hollow fiber membrane. Is to provide a method for producing a hollow fiber membrane.

An object of the present invention is to provide a core liquid for the inner nozzle of the triple annular nozzle that constitutes a triple ring in the order of the inner nozzle, the middle nozzle, and the outer nozzle, the reinforcing fiber and the spinning dope for the outer nozzle, and the outer This is achieved by a method of producing a fiber-reinforced porous hollow fiber membrane in which a spinning undiluted solution is introduced into a nozzle and wet spinning or dry wet spinning is performed to completely embed the reinforcing fiber in the hollow fiber membrane .

When spun using a double annular nozzle, the reinforcing fibers discharged together with the spinning dope will be moved outside of the hollow fiber membrane-like material, forming a film spinning solution discharged from the outer nozzle solidifies In the process, the reinforcing fiber is not partially buried in the hollow fiber membrane, and there is a case where the reinforcement is insufficient, but in the method of the present invention, the reinforcement pushed out from the middle nozzle using the triple annular nozzle Since the spinning solution is discharged from the outer nozzle further to the outside of the fiber, the hollow fiber membrane can be manufactured in a state where the reinforcing fiber is completely embedded inside the porous hollow fiber membrane, and the high strength hollow fiber There is an effect that a film can be obtained.

2 is an enlarged cross-sectional photograph of a reinforcing fiber-embedded porous hollow fiber membrane obtained in Example 1. 4 is an enlarged cross-sectional photograph of a reinforcing fiber-embedded porous hollow fiber membrane obtained in Comparative Example 4.

  As the triple annular nozzle, a conventionally known one is used, that is, a triple ring in the order of an inner nozzle, a middle nozzle and an outer nozzle having a diameter corresponding to a desired hollow fiber membrane size. It can be used without any particular limitation. Permeation performance is achieved by placing reinforcing fibers at a position that does not exceed 90% of the thickness of the hollow fiber membrane as viewed from the surface of the hollow fiber membrane that is not the functional layer (workpiece contact side) of the porous hollow fiber membrane. Since the mechanical properties can be further improved while keeping the separation performance high, a triple annular nozzle having an inner diameter, an inner nozzle having an outer diameter, an inner nozzle, and an outer nozzle, which can preferably spin such a hollow fiber membrane, is provided. Selected.

Fiber-reinforced porous hollow fiber membrane, a core liquid inside the nozzle of the triple annular nozzle, the reinforcing fibers and dope the middle side nozzle, subjected to wet spinning or dry-wet spinning by introducing further spinning solution, respectively to the outer nozzle It is manufactured by.

As the core liquid, a non-solvent of a film-forming resin, for example, water, an aqueous polyvinylpyrrolidone solution, or the like is used. As the polymer of the spinning dope, any of known hollow fiber membrane-forming materials (polymers) can be used. For example, cellulose materials such as cellulose acetate, cellulose propionate, cellulose butyrate, regenerated cellulose or a mixture thereof, polysulfone Examples thereof include hydrophobic polymers such as resins, polyethersulfone resins, polyvinylidene fluoride resins, polyacrylonitrile resins, polyetherimide resins, aramid resins , polypropylene resins, and polyethylene resins. As a soluble solvent for the film-forming resin, an aprotic polar solvent such as alcohol, dimethylformamide, diethylformamide, dimethylacetamide, diethylacetamide, dimethylsulfoxide, N-methyl-2-pyrrolidone is preferably used.

  The spinning dope is introduced into both the middle nozzle and the outer nozzle, but the spinning dope used may be the same or different.

  The reinforcing fiber introduced into the middle nozzle together with the spinning dope can be used without particular limitation as long as it is a fiber material used as a conventionally used reinforcing material. For example, monofilament, multifilament, spun yarn, etc. Specifically, natural or synthetic fibers made from polypropylene, polyethylene, fluororesin, polyethylene terephthalate, polybutylene terephthalate, polyacrylonitrile, polyphenylene sulfide, vinyl chloride, cellulose, polylactic acid, polyvinyl alcohol, polyamide, polyimide, aramid, etc. And at least one of metal fibers such as stainless steel and copper, glass fibers, and carbon fibers. Polyethylene terephthalate fibers are preferably used.

Such reinforcing fibers are introduced into the middle nozzle together with the spinning dope. Introduction into the medium side nozzles of the reinforcing fibers, implemented method, or a triple tubular nozzle, the reinforcing fiber inlet pipe in a state capable of introducing the reinforcing fibers in the middle side in the nozzle performed with spinning solution from the area whereto the spinning solution is supplied reinforcing fiber medium side in the nozzle and a method carried out using the what may be any method as long as the method to be introduced.

The introduction of the reinforcing fibers is preferably performed along the outer peripheral surface of the inner nozzle. This is because the spinning fiber discharged from the nozzle comes into contact with the core solution and the non-solvent of the core solution and the solvent of the spinning solution are exchanged to form a membrane, so that the reinforcing fibers in the spinning solution are pushed out to the outer peripheral side of the membrane. The purpose is to suppress exposure of the reinforcing fiber to the outer periphery of the membrane. Further, the reinforcing fibers are used evenly dispersed in the intermediate nozzle, but a plurality of reinforcing fibers may be inserted partially, for example, at a part of the intermediate nozzle or at a symmetrical position (see FIG. 1).

In spinning, the core liquid discharged from each nozzle and the spinning liquid may be discharged at the same pressure, but are preferably introduced to the outer nozzle to prevent the reinforcing fibers from being exposed outside the hollow fiber membrane. The extrusion pressure for the spinning dope is set higher than the extrusion pressure for the spinning dope introduced into the middle nozzle.

Porous hollow fiber membrane, solidifying the porous hollow fiber membrane-like material is spun using a coagulating liquid by wet spinning or dry-wet spinning method, washing is produced by performing drying.

  Next, the present invention will be described with reference to examples.

Example 1
Inner nozzle from inner nozzle than inner nozzle of triple ring nozzle consisting of inner nozzle of inner diameter 0.5mm, outer diameter 0.7mm, outer nozzle of inner diameter 2mm and inner diameter 1mm, outer diameter 1.125mm sandwiched between them While flowing out the water as the liquid, two polyethylene terephthalate multifilaments (yarn fineness 110 dtex / 24 filament; breaking strength 6N) as the reinforcing fiber and the spinning stock solution were compared with the feed rate of the spinning stock solution. Supply to two locations that are symmetrically arranged on the circumference of the intermediate nozzle at a supply ratio at which the supply speed is about the same, and only the spinning stock solution is discharged from the outer nozzle. Solidification was performed in water (coagulation liquid) at 50 ° C., and a hollow fiber membrane embedded with reinforcing fibers was obtained by dry and wet spinning.

Here, as the stock solution for spinning, 20% by weight of polyphenylsulfone, 65% by weight of dimethylformamide, and 15% by weight of polyvinyl pyrrolidone are used. This was carried out using a pipe equipped with a reinforcing fiber introduction pipe in a state where the reinforcing fiber could be introduced into the middle nozzle.

Reinforcing fiber embedded hollow fiber membrane material is subjected to high-pressure sterilization treatment at 121 ° C for 1 hour, and then placed in a constant temperature bath at a chamber temperature of 40 ° C for drying treatment, thereby reinforcing fiber embedded porous polyphenylsulfone A hollow fiber membrane was obtained. An enlarged cross-sectional photograph (× 175) of the obtained reinforcing fiber-embedded porous hollow fiber membrane is shown in FIG. 1, and it was confirmed that the reinforcing fiber was completely buried in the hollow fiber membrane film thickness.

The obtained porous polyphenylsulfone hollow fiber membrane has an outer diameter of 1000 μm, an inner diameter of 500 μm, a water vapor transmission rate at 25 ° C. of 0.28 g / cm ² / min / MPa, and a pure water transmission rate of 0 ml / cm ² / hour. / MPa, the air permeation rate was 0 ml / cm ² / min / MPa. Further, a tensile test was conducted at a distance between marked lines of 50 mm and a test speed of 20 mm per minute, and the fracture stress was calculated to be 58 MPa.

Example 2
In Example 1, a spinning stock solution prepared by using the same amount (20% by weight) of polysulfone instead of polyphenylsulfone was used. The obtained porous polysulfone hollow fiber membrane has an outer diameter of 1000 μm, an inner diameter of 500 μm, a water vapor transmission rate at 25 ° C. of 0.23 g / cm ² / min / MPa, and a pure water transmission rate of 0 ml / cm ² / hour / MPa. The air transmission rate was 0 ml / cm ² / min / MPa. A tensile test was conducted at a distance between marked lines of 50 mm and a test speed of 20 mm per minute, and the breaking stress was calculated to be 57 MPa.

Example 3
In Example 1, a spinning stock solution comprising 20% by weight of polyetherimide and 80% by weight of dimethylacetamide was used. The obtained porous polyetherimide hollow fiber membrane has an outer diameter of 1000 μm, an inner diameter of 500 μm, a water vapor transmission rate at 25 ° C. of 0.36 g / cm ² / min / MPa, and a pure water transmission rate of 0 ml / cm ² / hour. / MPa, the air permeation rate was 0 ml / cm ² / min / MPa. A tensile test was conducted at a distance between marked lines of 50 mm and a test speed of 20 mm per minute, and the breaking stress was calculated to be 57 MPa.

Comparative Example 1
In Example 1, spinning is performed without using reinforcing fibers while water as core liquid is discharged from the inner nozzle of a double tubular nozzle comprising an inner nozzle having an inner diameter of 0.4 mm and an outer diameter of 0.6 mm and an outer nozzle having an inner diameter of 1.15 mm. The stock solution was discharged from the outer nozzle, passed through a free running space, solidified in water (coagulating liquid) at a water temperature of 50 ° C., and a hollow fiber membrane embedded with reinforcing fibers was obtained by dry and wet spinning. The porous polyphenylsulfone hollow fiber membrane obtained by drying this has an outer diameter of 1000 μm, an inner diameter of 700 μm, a water vapor transmission rate at 25 ° C. of 0.28 g / cm ² / min / MPa, and a pure water transmission rate of 0 ml / cm ² / time / MPa, air permeation rate was 0 ml / cm ² / min / MPa. A tensile test was performed at a distance between marked lines of 50 mm and a test speed of 20 mm per minute, and the breaking stress was calculated to be 8.5 MPa.

Comparative Example 2
In Comparative Example 1, when the spinning stock solution used in Example 2 was used as the spinning stock solution, the obtained porous polysulfone hollow fiber membrane had an outer diameter of 1000 μm and an inner diameter of 700 μm, and the water vapor transmission rate at 25 ° C. was 0.23. g / cm ² / min / MPa, pure water permeation rate 0 ml / cm ² / time / MPa, the air permeation rate was 0 ml / cm ² / min / MPa. A tensile test was conducted at a distance between marked lines of 50 mm and a test speed of 20 mm per minute, and the breaking stress was calculated to be 8.1 MPa.

Comparative Example 3
In Comparative Example 1, when the spinning stock solution used in Example 3 was used as the spinning stock solution, the obtained porous polyetherimide hollow fiber membrane had an outer diameter of 1000 μm and an inner diameter of 700 μm, and the water vapor transmission rate at 25 ° C. 0.36 g / cm ² / min / MPa, pure water permeation rate was 0 ml / cm ² / hr / MPa, and air permeation rate was 0 ml / cm ² / min / MPa. A tensile test was performed at a distance between marked lines of 50 mm and a test speed of 20 mm per minute, and the breaking stress was calculated to be 8.0 MPa.

Comparative Example 4
In Example 3, polyethylene terephthalate multifilament (yarn fineness 110 dtex / 24 filament) as a reinforcing fiber and spinning dope while water as core liquid was allowed to flow out from the inner nozzle of a double annular nozzle comprising an inner nozzle and an outer nozzle Was discharged from the outer nozzle, solidified in water (coagulating liquid) at a water temperature of 50 ° C., and a hollow fiber membrane embedded with reinforcing fibers was obtained by dry and wet spinning. An enlarged cross-sectional photograph (× 175) of the reinforcing fiber-embedded porous polyetherimide hollow fiber membrane obtained by drying this is shown in FIG. 2, and a part of the reinforcing fiber is exposed to the outside of the hollow fiber. It was confirmed that

This porous polyetherimide hollow fiber membrane has an outer diameter of 1000 μm, an inner diameter of 700 μm, a water vapor transmission rate at 25 ° C. of 0.36 g / cm ² / min / MPa, and a pure water transmission rate of 0 ml / cm ² / hour / MPa The air transmission rate was 0 ml / cm ² / min / MPa. In addition, a tensile test was performed at a distance between marked lines of 50 mm and a test speed of 20 mm per minute, and the breaking stress was calculated. Depending on the location from 8.0 to 27.0 MPa, such as the strength without reinforcement to about half of the strength during full reinforcement. Unevenness was seen.

  The obtained fiber-reinforced porous hollow fiber membrane can suppress yarn breakage under high load and long-term use, so it can be used in various fields such as water purification treatment by membrane filtration, wastewater treatment, dehumidification or humidification. Can be used effectively.

Claims (3)

The core liquid is introduced into the inner nozzle of the triple ring nozzle that forms a triple ring in the order of the inner nozzle, the inner nozzle, and the outer nozzle, the reinforcing fiber and the spinning dope are introduced into the inner nozzle, and the spinning dope is introduced into the outer nozzle. Then, a method for producing a fiber-reinforced porous hollow fiber membrane in which the reinforcing fiber is completely buried in the hollow fiber membrane , wherein wet spinning or dry wet spinning is performed.   The method for producing a fiber-reinforced porous hollow fiber membrane according to claim 1, wherein the reinforcing fibers are introduced along the outer peripheral surface of the inner nozzle. The method for producing a fiber-reinforced porous hollow fiber membrane according to claim 1, wherein spinning is carried out by setting the extrusion pressure for the spinning dope in the outer nozzle higher than the extrusion pressure for the spinning dope in the middle nozzle.