JP2004290751A

JP2004290751A - Method for manufacturing steam permeable membrane

Info

Publication number: JP2004290751A
Application number: JP2003084053A
Authority: JP
Inventors: Hideki Tashiro; 秀樹田代
Original assignee: Nok Corp
Current assignee: Nok Corp
Priority date: 2003-03-26
Filing date: 2003-03-26
Publication date: 2004-10-21
Anticipated expiration: 2023-03-26
Also published as: JP4100215B2

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a steam permeable membrane having excellent gas permeability, not causing a water leak toward a gas side, also excellent in strength stability and effectively usable as a humidifying membrane for a fuel cell, in a porous hollow fiber membrane using a polysulfone resin. <P>SOLUTION: A spinning raw liquid comprising a water soluble organic solvent solution of a polyphenylsulfone resin or a polysulfone resin and a hydrophilic polyvinyl pyrrolidone is subjected to dry/wet spinning using water as a core liquid to manufacture the steam permeable membrane comprising a porous polyphenylsulfone or polysulfone hollow fiber membrane. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【０００１】
【発明の属する技術分野】
本発明は、水蒸気透過膜の製造法に関する。さらに詳しくは、燃料電池用加湿膜等として有効に用いられる水蒸気透過膜の製造法に関する。
【０００２】
【従来の技術】
近年、多孔質中空糸膜を用いて除湿・加湿を行う方法が注目されている。多孔質中空糸膜方式は、メンテナンスフリーであるばかりではなく、駆動に電源を必要としないなどの多くの利点を有している。
【０００３】
水蒸気を選択的に透過させる膜として、現在数種類のものが市販されているが、それぞれ素材および透過原理が異っている。ポリイミド樹脂を素材として用い、溶解拡散法によって本操作を行う膜においては、耐熱性および強度にはすぐれているが、水蒸気透過係数が低いという欠点がみられる。また、フッ素系イオン交換膜を素材に用い、イオン水和法を原理としている膜は、水蒸気透過係数は高いものの耐熱性に乏しく、膜自体が非常に高価であるという欠点がある。
【０００４】
一方、ポリエーテルイミド樹脂を素材とし、毛管凝縮法で除湿・加湿を行う膜は、水蒸気透過性と耐熱性の両立が図られており、多くの産業分野で採用されているが、膜の絶対強度が弱く、特に柔軟性に乏しいため、多量の気体の除湿・加湿の際、中空糸膜が切断されるという問題がみられる。
【０００５】
この多孔質中空糸膜は、近年燃料電池スタックの隔膜加湿に用いられるいるが、燃料電池の場合、車載用では４０００ＮＬ／分程度の多量の空気加湿が必要であり、また定置用では加湿の駆動源に温水が使用される場合が多く、いずれにしても多孔質中空糸膜への耐久性と耐熱性の付与が特に必要とされている。
【０００６】
実際に、固体高分子型燃料電池の場合、実稼動温度は約６０〜８０℃で水蒸気飽和状態での雰囲気となる。ポリエーテルイミド樹脂は、耐熱性にすぐれ、加水分解し難い樹脂ではあるものの、湿潤加熱条件下では従来から伸びや柔軟性の低下の著しいことが指摘されており、多孔質中空糸膜の切断に至っていた。
【０００７】
さらに、ポリスルホン樹脂素材は、水ロ過用限外ロ過膜、精密ロ過膜等として一般的に用いられており、湿潤加湿条件下での強度安定性にすぐれていることは知られているが、水蒸気透過膜用途としては実用化が困難とされている。その理由は、毛管凝縮法を適用するために適当な細孔径を得ることが困難であり、従来の技術では水が気体側に浸み出してくるなどの不具合があった。
【０００８】
ポリフェニルスルホン樹脂および親水性ポリビニルピロリドンの水溶性有機溶媒溶液よりなる紡糸原液を用い、Ｎ−メチル−２−ピロリドン水溶液を芯液として乾湿式紡糸し、多孔質ポリフェニルスルホン樹脂中空糸膜を得る方法は、既に本出願人によって提案されているが（特開２００１−２１９０４３号公報）、ここで得られた多孔質中空糸膜は油水分離用限外ロ過膜等に好適に使用されると述べられており、水蒸気透過を目的とするものではない。
【０００９】
また、ポリフェニルスルホン樹脂および親水性ポリビニルピロリドンの水溶性有機溶媒溶液よりなる紡糸溶液中にさらに水を加え、水を芯液として乾湿式紡糸し、多孔質ポリフェニルスルホン樹脂中空糸膜を得る方法も本出願人によって提案されているが（特開２００１−４６８６７〜８号公報）、ここでもその目的は純水透過係数の改善を図ることにあるとされている。
【００１０】
【発明が解決しようとする課題】
本発明の目的は、ポリスルホン系樹脂を使用した多孔質中空糸膜において、気体透過性にすぐれているばかりではなく、気体側への水漏れがなく、強度安定性にもすぐれ、燃料電池用加湿膜などとして有効に使用し得る水蒸気透過膜の製造法を提供することにある。
【００１１】
【課題を解決するための手段】
かかる本発明の目的は、ポリフェニルスルホン樹脂またはポリスルホン樹脂および親水性ポリビニルピロリドンの水溶性有機溶媒溶液よりなる紡糸原液を、水を芯液として乾湿式紡糸し、多孔質ポリフェニルスルホン中空糸膜または多孔質ポリスルホン中空糸膜よりなる水蒸気透過膜を製造することによって達成される。
【００１２】
【発明の実施の形態】
ポリフェニルスルホン樹脂は、以下に示されるくり返し単位

即ちビフェニレン基を有し、イソプロピリデン基を有しないものであり、実際には市販品、例えばアモコ社製品ＲＡＤＥＬＲシリーズのもの等をそのまま使用することができる。また、ポリフェニルスルホン樹脂と同様に、ポリスルホン樹脂を用いることもできる。
【００１３】
ポリフェニルスルホン樹脂またはポリスルホン樹脂を製膜成分とする紡糸原液は、そこに親水性ポリビニルピロリドンおよび水溶性有機溶媒が添加され、紡糸原液が形成される。水溶性有機溶媒としては、ジメチルホルムアミド、ジメチルアセトアミド、Ｎ−メチル−２−ピロリドン等の非プロトン性極性溶媒が用いられる。ポリスルホン系樹脂は、紡糸原液中約１０〜４０重量％、好ましくは約１５〜３０重量％を占めるような濃度で用いられる。このような濃度範囲より少なくてもあるいは多くても、所望の孔径および膜強度を有する多孔質中空糸膜は得られない。
【００１４】
親水性高分子物質として添加されるポリビニルピロリドンとしては、分子量が約１０００（Ｋ−１５）〜１２０００００（Ｋ−９０）、好ましくは約１００００（Ｋ−３０）〜１２０００００（Ｋ−９０）のものが、ポリスルホン系樹脂１００重量部当り約５０〜１５０重量部、好ましくは約５０〜１００重量部の割合で用いられる。ポリビニルピロリドンのこのような割合での添加は、多孔質膜の表面孔径等の構造制御にも多少の影響はみられるが、それ以上に多孔質膜の空気透過速度を低下させ、すなわちガスバリア性を向上させ、水蒸気透過速度を向上させるという効果を達成させる。
【００１５】
このような紡糸原液を用いての乾湿式紡糸は、水を芯液として行われ、水または水性凝固溶中で凝固させた多孔質中空糸膜は水洗後乾燥させる。水洗は、常温あるいは温水、オートクレーブによる高温（例えば１２１℃）などにより行われる。
【００１６】
【発明の効果】
本発明方法により得られる多孔質ポリフェニルスルホン樹脂またはポリスルホン樹脂中空糸膜は、膜強度および耐久性の点ですぐれているばかりではなく、水蒸気透過膜の点で特にすぐれているので、燃料電池用加湿膜などとして有効に使用することができる。
【００１７】
【実施例】
次に、実施例について本発明を説明する。
【００１８】
実施例１
ポリフェニルスルホン樹脂（アモコ社製品ＲＡＤＥＬＲ−５０００）２０部（重量、以下同じ）、ポリビニルピロリドン（ＩＳＰ社製品Ｋ−３０Ｇ）１５部およびジメチルアセトアミド６５部よりなる室温で均一な紡糸原液を、水を芯液として二重環状ノズルから水凝固浴中に乾湿式紡糸し、その後１２１℃の加圧水中で１時間洗浄してから６０℃のオーブン中で乾燥し、多孔質ポリフェニルスルホン樹脂中空糸膜を得た。
【００１９】
実施例２
実施例１において、ノズル径、紡糸原液の吐出速度などを変更することにより、内、外径の異なる多孔質ポリフェニルスルホン樹脂中空糸膜を得た。
【００２０】
実施例３
実施例１において、ポリフェニルスルホン樹脂の代りに同量のポリスルホン樹脂（ＢＡＳＦ社製品ＵｌｔｒａｓｏｎＳ３０１０）を用い、多孔質ポリスルホン中空糸膜を得た。
【００２１】
比較例１
ポリエーテルイミド樹脂（ＧＥポリマー社製品ウルテム１０００）２０部およびジメチルアセトアミド８０部よりなる室温で均一な紡糸原液を用い、実施例１と同様に乾湿式紡糸し、６０℃のオーブン中で乾燥して、多孔質ポリエーテルイミド樹脂中空糸を得た。
【００２２】
比較例２
比較例１において、ノズル径、紡糸原液の吐出速度などを変更することにより、内、外径の異なる多孔質ポリエーテルイミド樹脂中空糸膜を得た。
【００２３】
以上の各実施例および比較例で得られた多孔質中空糸膜について、いずれも２５℃における水蒸気透過速度、純水透過速度および空気透過速度を測定し、さらに引張強度および伸度（９５℃の温水浸漬前、２８０時間浸漬後）も測定した。得られた結果は、次の表１に示される。

【００２４】
さらに、実施例２で得られた多孔質ポリフェニルスルホン樹脂中空糸膜（有効長１５０ｍｍ）１７００本をモジュール化し、入口空気圧０．５ＭＰａ、バージ率２０％の条件下で、膜型除湿器を使用して除湿機能を測定すると、次の表２に示されるような結果が得られた。

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for producing a water vapor permeable membrane. More specifically, the present invention relates to a method for producing a water vapor permeable membrane effectively used as a humidifying membrane for a fuel cell or the like.
[0002]
[Prior art]
In recent years, a method of performing dehumidification and humidification using a porous hollow fiber membrane has attracted attention. The porous hollow fiber membrane system is not only maintenance-free, but also has many advantages such as not requiring a power supply for driving.
[0003]
Currently, several types of membranes for selectively transmitting water vapor are commercially available, but each has a different material and a different transmission principle. A membrane using a polyimide resin as a raw material and performing this operation by a solution diffusion method has excellent heat resistance and strength, but has a drawback that the water vapor transmission coefficient is low. Further, a membrane using a fluorine-based ion exchange membrane as a material and based on the ion hydration method has a drawback that although the water vapor permeability coefficient is high, the heat resistance is poor and the membrane itself is very expensive.
[0004]
On the other hand, membranes made of polyetherimide resin and dehumidified and humidified by the capillary condensation method have achieved both water vapor permeability and heat resistance, and have been adopted in many industrial fields. Since the strength is low, and particularly the flexibility is poor, there is a problem that the hollow fiber membrane is cut when a large amount of gas is dehumidified and humidified.
[0005]
This porous hollow fiber membrane has recently been used for humidifying a membrane of a fuel cell stack. In the case of a fuel cell, a large amount of air humidification of about 4,000 NL / min is required for a vehicle, and a humidifying drive is required for a stationary cell. In many cases, hot water is used as a source, and in any case, it is particularly necessary to impart durability and heat resistance to the porous hollow fiber membrane.
[0006]
Actually, in the case of the polymer electrolyte fuel cell, the actual operating temperature is about 60 to 80 ° C., and the atmosphere is in a water vapor saturated state. Although polyetherimide resins are excellent in heat resistance and are difficult to hydrolyze, it has been pointed out that under wet heating conditions, the elongation and flexibility have been remarkably reduced. Had been reached.
[0007]
Furthermore, polysulfone resin materials are generally used as ultrafiltration membranes for water filtration, precision filtration membranes, and the like, and are known to have excellent strength stability under wet and humidified conditions. However, it has been considered difficult to put it to practical use as a water vapor permeable membrane. The reason is that it is difficult to obtain an appropriate pore diameter in order to apply the capillary condensation method, and the conventional technique has problems such as water seeping out to the gas side.
[0008]
Using a spinning solution comprising a polyphenylsulfone resin and a hydrophilic polyvinylpyrrolidone solution in a water-soluble organic solvent, dry and wet spinning is performed using an N-methyl-2-pyrrolidone aqueous solution as a core solution to obtain a porous polyphenylsulfone resin hollow fiber membrane. The method has already been proposed by the present applicant (Japanese Patent Application Laid-Open No. 2001-219043), but the porous hollow fiber membrane obtained here is suitably used for an oil-water separation ultrafiltration membrane or the like. It is stated and is not intended for water vapor transmission.
[0009]
Further, a method of obtaining a porous polyphenylsulfone resin hollow fiber membrane by further adding water to a spinning solution composed of a water-soluble organic solvent solution of a polyphenylsulfone resin and a hydrophilic polyvinylpyrrolidone, and spinning dry and wet with water as a core liquid. Has also been proposed by the present applicant (Japanese Patent Application Laid-Open No. 2001-46867-8), but it is said that the purpose here is also to improve the pure water permeability coefficient.
[0010]
[Problems to be solved by the invention]
An object of the present invention is to provide a porous hollow fiber membrane using a polysulfone-based resin, which not only has excellent gas permeability, does not leak water to the gas side, has excellent strength stability, and has excellent humidification for fuel cells. An object of the present invention is to provide a method for producing a water vapor permeable membrane that can be effectively used as a membrane or the like.
[0011]
[Means for Solving the Problems]
An object of the present invention is to provide a spinning solution comprising a polyphenylsulfone resin or a polysulfone resin and a hydrophilic polyvinylpyrrolidone solution in a water-soluble organic solvent, which is subjected to dry-wet spinning using water as a core solution to obtain a porous polyphenylsulfone hollow fiber membrane or This is achieved by producing a water vapor permeable membrane composed of a porous polysulfone hollow fiber membrane.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
Polyphenyl sulfone resin has the repeating unit shown below

That is, it has a biphenylene group and no isopropylidene group, and a commercially available product, for example, a product of AMOCO RADEL R series can be used as it is. Further, similarly to the polyphenylsulfone resin, a polysulfone resin can also be used.
[0013]
A spinning dope containing a polyphenylsulfone resin or a polysulfone resin as a film forming component is added with hydrophilic polyvinylpyrrolidone and a water-soluble organic solvent to form a spinning dope. As the water-soluble organic solvent, an aprotic polar solvent such as dimethylformamide, dimethylacetamide, and N-methyl-2-pyrrolidone is used. The polysulfone-based resin is used in such a concentration that it accounts for about 10 to 40% by weight, preferably about 15 to 30% by weight in the spinning dope. If the concentration is lower or higher than such a range, a porous hollow fiber membrane having a desired pore size and membrane strength cannot be obtained.
[0014]
Polyvinylpyrrolidone added as a hydrophilic polymer substance has a molecular weight of about 1,000 (K-15) to 12,000,000 (K-90), preferably about 10,000 (K-30) to 1200,000 (K-90). It is used in an amount of about 50 to 150 parts by weight, preferably about 50 to 100 parts by weight, per 100 parts by weight of the polysulfone resin. Although the addition of polyvinylpyrrolidone at such a ratio has some influence on the structural control of the porous membrane such as the surface pore diameter, the air permeability of the porous membrane is further reduced, that is, the gas barrier property is reduced. To achieve the effect of improving the water vapor transmission rate.
[0015]
Dry-wet spinning using such a spinning stock solution is performed using water as a core solution, and a porous hollow fiber membrane solidified in water or an aqueous coagulation solution is washed with water and dried. The water washing is performed at normal temperature, hot water, high temperature (for example, 121 ° C.) by an autoclave, or the like.
[0016]
【The invention's effect】
The porous polyphenylsulfone resin or polysulfone resin hollow fiber membrane obtained by the method of the present invention is not only excellent in terms of membrane strength and durability, but also particularly excellent in terms of a water vapor permeable membrane. It can be used effectively as a humidifying film.
[0017]
【Example】
Next, the present invention will be described with reference to examples.
[0018]
Example 1
A uniform spinning solution at room temperature consisting of 20 parts (weight, the same applies hereinafter) of polyphenylsulfone resin (RADEL R-5000 manufactured by Amoco), 15 parts of polyvinylpyrrolidone (K-30G manufactured by ISP) and 65 parts of dimethylacetamide was added to water. As a core liquid, spin-dry spinning from a double annular nozzle into a water coagulation bath, washing in pressurized water at 121 ° C. for 1 hour, and drying in an oven at 60 ° C. to form a porous polyphenylsulfone resin hollow fiber membrane Got.
[0019]
Example 2
In Example 1, a porous polyphenyl sulfone resin hollow fiber membrane having different inner and outer diameters was obtained by changing the nozzle diameter, the spinning stock solution discharge speed, and the like.
[0020]
Example 3
In Example 1, a porous polysulfone hollow fiber membrane was obtained by using the same amount of polysulfone resin (Ultrason S3010 manufactured by BASF) in place of the polyphenylsulfone resin.
[0021]
Comparative Example 1
Using a uniform spinning solution at room temperature consisting of 20 parts of a polyetherimide resin (Ultem 1000 manufactured by GE Polymer) and 80 parts of dimethylacetamide, spinning was performed in the same manner as in Example 1, and then dried in an oven at 60 ° C. Thus, a porous polyetherimide resin hollow fiber was obtained.
[0022]
Comparative Example 2
In Comparative Example 1, porous polyetherimide resin hollow fiber membranes having different inner and outer diameters were obtained by changing the nozzle diameter, the spinning stock solution discharge speed, and the like.
[0023]
For the porous hollow fiber membranes obtained in each of the above Examples and Comparative Examples, the water vapor transmission rate, pure water transmission rate, and air transmission rate at 25 ° C. were measured, and the tensile strength and elongation (95 ° C. Before immersion in warm water for 280 hours). The results obtained are shown in Table 1 below.

[0024]
Further, 1,700 porous polyphenylsulfone resin hollow fiber membranes (effective length 150 mm) obtained in Example 2 were modularized, and a membrane dehumidifier was used under the conditions of an inlet air pressure of 0.5 MPa and a barge rate of 20%. Then, when the dehumidifying function was measured, the results as shown in the following Table 2 were obtained.

Claims

A method for producing a water vapor permeable membrane, comprising spinning a spinning solution comprising a polyphenylsulfone resin and a solution of a hydrophilic polyvinylpyrrolidone in a water-soluble organic solvent using water as a core solution in a dry and wet manner.

A water vapor permeable membrane comprising a porous polyphenylsulfone resin hollow fiber membrane produced by the method according to claim 1.

A process for producing a water vapor permeable membrane, comprising spinning a spinning solution comprising a polysulfone resin and a solution of a hydrophilic polyvinylpyrrolidone in a water-soluble organic solvent using water as a core solution in a dry and wet manner.

A water vapor permeable membrane comprising a porous polysulfone resin hollow fiber membrane produced by the method according to claim 1.

The water vapor permeable membrane according to claim 2, which is used as a humidifying membrane for a fuel cell.