JPH08283447A - Porous membrane made of hydrophilic tetrafluoroethylene resin and its production - Google Patents
Porous membrane made of hydrophilic tetrafluoroethylene resin and its productionInfo
- Publication number
- JPH08283447A JPH08283447A JP7113883A JP11388395A JPH08283447A JP H08283447 A JPH08283447 A JP H08283447A JP 7113883 A JP7113883 A JP 7113883A JP 11388395 A JP11388395 A JP 11388395A JP H08283447 A JPH08283447 A JP H08283447A
- Authority
- JP
- Japan
- Prior art keywords
- hydrophilic
- porous membrane
- tetrafluoroethylene resin
- membrane
- hydrophilic material
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
Landscapes
- Coating Of Shaped Articles Made Of Macromolecular Substances (AREA)
- Manufacture Of Porous Articles, And Recovery And Treatment Of Waste Products (AREA)
- Laminated Bodies (AREA)
Abstract
Description
【0001】[0001]
【産業上の利用分野】本発明は、親水性四弗化エチレン
樹脂多孔質膜に関し、さらに詳しくは、耐久性に優れた
親水性材料層を有し、水透過流量維持性及び耐薬品性に
優れた親水性四弗化エチレン樹脂多孔質膜とその製造方
法に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydrophilic tetrafluoroethylene resin porous membrane, and more specifically, it has a hydrophilic material layer having excellent durability and is capable of maintaining water permeation flow rate and chemical resistance. The present invention relates to an excellent hydrophilic tetrafluoroethylene resin porous membrane and a method for producing the same.
【0002】[0002]
【従来の技術】四弗化エチレン樹脂(PTFE)を素材
とする多孔質体(多孔質膜)は、耐薬品性、耐熱性など
PTFEが本来有する材質的な特徴と、均一で微細な多
孔質構造に基づく高分離能、高い気孔率に基づく高透過
性などの構造的な特徴を併せもつため、メンブランフィ
ルター、電池隔膜、電線、衣類、人工血管などの広範な
分野で、高機能材料として使用されている。ところで、
PTFEに固有の撥水性は、例えば、スキーウエアへの
適用など撥水性が必要な分野に対して非常に有効である
が、全ての用途において有利に働くとはいえない。PT
FE多孔質膜は、例えば、分離膜の用途において、空気
や有機溶媒の透過流量は高いものの、分離用途の大半を
占める水系での分離用途においては、撥水性のため微細
多孔質構造内を水が透過しにくく、満足な分離機能を発
揮することができない。PTFE多孔質膜の微細多孔質
構造内に、水に可溶性の有機溶媒を含浸した後、水で置
換すれば親水化することができるが、この方法は、非常
に煩雑であることに加えて、親水化処理しても、水溶液
中の気泡や溶存気体が徐々に付着して、短期間に水透過
流量が低下するという問題点がある。2. Description of the Related Art A porous body (porous film) made of tetrafluoroethylene resin (PTFE) is a material having the original characteristics of PTFE such as chemical resistance and heat resistance, and a uniform fine porosity. Since it has structural features such as high resolution based on structure and high permeability based on high porosity, it is used as a highly functional material in a wide range of fields such as membrane filters, battery diaphragms, electric wires, clothing and artificial blood vessels. Has been done. by the way,
The water repellency inherent in PTFE is very effective for fields requiring water repellency such as application to ski wear, but it cannot be said to be advantageous in all applications. PT
The FE porous membrane has a high permeation flow rate of air and an organic solvent in the use of a separation membrane, for example. Is difficult to permeate, and a satisfactory separation function cannot be exerted. Although it is possible to make hydrophilic by impregnating a water-soluble organic solvent in the microporous structure of the PTFE porous membrane and then substituting with water, this method is very complicated, Even with the hydrophilic treatment, there is a problem that bubbles and dissolved gas in the aqueous solution are gradually attached and the water permeation flow rate is reduced in a short period of time.
【0003】従来、PTFE多孔質膜を半永久的に親水
化する方法として、例えば、電子線などのエネルギー照
射やアルカリ金属によるPTFE多孔質膜の表面改質、
あるいは親水性樹脂のPTFE多孔質膜の微細多孔質構
造の表面への固定など、様々な方法が提案されている。
これらのPTFE多孔質膜の親水化法の中でも、効果が
確実であり、広く実用化されているのは、PTFE多孔
質膜にポリビニルアルコール(PVA)を含浸させて、
微細多孔質構造の表面にPVAを塗布し、該PVAを架
橋して不溶化する方法である(特公昭53−21270
号公報)。このPVA塗布PTFE多孔質膜は、PVA
の親水性により、水に接触すると濡れるため、微細多孔
質構造内に水が侵入しやすくなっており、未処理のPT
FE多孔質膜のままでは殆ど水が透過しないような低い
圧力でも、水溶液を容易に濾過することができる。Conventionally, as a method of semipermanently hydrophilizing a PTFE porous membrane, for example, energy irradiation of electron beam or the like and surface modification of the PTFE porous membrane with an alkali metal,
Alternatively, various methods have been proposed, such as fixing a hydrophilic resin to the surface of the microporous structure of the PTFE porous membrane.
Among these methods for hydrophilizing the PTFE porous membrane, the effect is certain and widely used is that the PTFE porous membrane is impregnated with polyvinyl alcohol (PVA),
This is a method in which PVA is applied to the surface of a fine porous structure and the PVA is crosslinked to make it insoluble (Japanese Patent Publication No. 53-21270).
Issue). This PVA coated PTFE porous membrane is made of PVA
Due to its hydrophilicity, it becomes wet when it comes into contact with water, which makes it easier for water to penetrate into the microporous structure.
The aqueous solution can be easily filtered even at a low pressure at which water hardly permeates with the FE porous membrane as it is.
【0004】このような微細多孔質構造の表面に親水性
材料を塗布した親水性PTFE多孔質膜は、製造方法が
比較的簡単であり、親水化処理の確実性においても優れ
ているが、長期間使用すると、経時的に透過流量が低下
し、ついには水溶液を殆ど透過しなくなるなど、耐久性
に問題があった。また、このような従来の親水性PTF
E多孔質膜は、有機溶媒や酸・アルカリに対する耐性も
不十分であった。このような経時による水透過流量の低
下原因は、親水性材料の脱落によるものであると推定さ
れたが、実際に、水に濡れにくくなったPTFE多孔質
膜の重量を測定すると、親水化処理した当初の重量と殆
ど同じであり、塗布された親水性材料の総量に対して、
高々数%程度の重量減少が見られるに過ぎない。したが
って、微細多孔質構造の表面に親水性材料を塗布したP
TFE多孔質膜の親水性が低下する原因は、これまで十
分に把握されておらず、水透過流量維持のための対策に
ついても、満足できる方法は提案されていなかった。特
に、親水性材料を塗布したPTFE多孔質膜を使用後、
乾燥すると、体積が収縮する。これを再び水溶液に浸漬
すると、ほぼ元の体積に戻るが、水透過流量が低下す
る。このような水溶液に対する浸漬−乾燥のサイクルが
多くなると、ついには親水性PTFE多孔質膜の水溶液
に対する濡れ性が喪失する。しかし、その原因と対策に
ついても、これまでに報告されていない。The hydrophilic PTFE porous membrane in which a hydrophilic material is coated on the surface of such a fine porous structure is relatively easy to manufacture and is excellent in the reliability of the hydrophilization treatment. When it is used for a period of time, the permeation flow rate decreases with time, and finally the aqueous solution hardly permeates, which is a problem in durability. In addition, such conventional hydrophilic PTF
The E porous film also had insufficient resistance to organic solvents, acids and alkalis. It was presumed that the cause of the decrease in the water permeation flow rate with time was due to the fall-off of the hydrophilic material, but actually, when the weight of the PTFE porous membrane that became difficult to wet with water was measured, the hydrophilic treatment was performed. It is almost the same as the original weight, and for the total amount of hydrophilic material applied,
Only a few percent weight loss is observed at most. Therefore, P having a hydrophilic material applied to the surface of the microporous structure
The cause of the decrease in hydrophilicity of the TFE porous membrane has not been sufficiently understood so far, and no satisfactory method has been proposed as a measure for maintaining the water permeation flow rate. Especially after using a PTFE porous membrane coated with a hydrophilic material,
When dried, the volume shrinks. When this is immersed again in the aqueous solution, the volume returns to almost the original volume, but the water permeation flow rate decreases. When the number of such dipping-drying cycles with respect to the aqueous solution increases, the wettability of the hydrophilic PTFE porous membrane with respect to the aqueous solution is finally lost. However, the cause and measures have not been reported so far.
【0005】[0005]
【発明が解決しようとする課題】本発明の目的は、微細
多孔質構造の表面に耐久性に優れた親水性材料層が形成
され、水透過流量維持性及び耐薬品性に優れた親水性四
弗化エチレン樹脂多孔質膜とその製造方法を提供するこ
とにある。本発明者は、PVAなどの親水性材料の塗布
層を設けた親水性PTFE多孔質膜の水に対する透過流
量の低下問題について鋭意研究を重ねた結果、流量低下
の原因は、使用前に微細多孔質構造の表面を比較的均一
に覆っていた親水性材料が部分的に凝集し、基膜のPT
FE表面が剥き出しになることにあることを見いだし
た。An object of the present invention is to form a hydrophilic material layer having excellent durability on the surface of a fine porous structure, which is excellent in water permeation flow rate maintenance and chemical resistance. It is an object of the present invention to provide a porous fluorinated ethylene resin membrane and a method for producing the same. The present inventor has conducted earnest research on the problem of a decrease in the permeation flow rate of water into a hydrophilic PTFE porous membrane provided with a coating layer of a hydrophilic material such as PVA. As a result, the cause of the decrease in the flow rate is microporous before use. The hydrophilic material, which covered the surface of the textured structure relatively uniformly, partially aggregates to form the PT of the base film.
It was found that the FE surface was exposed.
【0006】使用前に微細多孔質構造内のPTFE表面
を比較的均一に覆っていた親水性材料が部分的に凝集
し、PTFE表面が剥き出しになる現象には、2つの要
因が絡んでいると推定される。第一の要因は、親水性材
料塗布層の強度である。もともと疎水性のPTFEと親
水性材料との間には親和性が乏しく、しかも親水性材料
が水を含んだときと乾燥したときの体積変化が非常に大
きいことから、親水化材料の塗布層の強度が弱く、その
形状を強固に保つことができないと、繰り返し使用中に
塗布層が微細多孔質構造の表面から脱落したり、あるい
は脱落しないまでも、PTFE表面の剥き出しになる部
分が増加し、親水性が低下してしまう。Two factors are involved in the phenomenon that the hydrophilic material, which covers the PTFE surface in the microporous structure relatively before use, partially aggregates to expose the PTFE surface. Presumed. The first factor is the strength of the hydrophilic material coating layer. Originally, hydrophobic PTFE and a hydrophilic material have a poor affinity, and the volume change when the hydrophilic material contains water and when it is dried is very large. If the strength is weak and the shape cannot be kept strong, the exposed portion of the PTFE surface increases even if the coating layer falls off from the surface of the microporous structure during repeated use, or even if it does not fall off, The hydrophilicity will decrease.
【0007】第二の要因は、乾燥時における親水性PT
FE多孔質膜の体積の収縮である。親水性PTFE多孔
質膜を水溶液に浸漬して使用した後、乾燥すると、親水
性材料の塗布層が湿潤時の数十分の一から数百分に一に
体積が減少し、この際の収縮力により多孔質膜全体が収
縮する。実際は、再び水溶液に浸漬して湿潤状態に戻す
と、収縮した多孔質膜は、ほぼ元の体積に戻るため、水
溶液の透過抵抗が増大することは殆どない。しかし、こ
の多孔質膜の大きな体積変化によって、親水性材料の塗
布層とPTFE表面との間に剥離が生じる。この2つの
要因によって起きるPTFEと親水性材料の剥離は、親
水性PTFE多孔質膜の微細多孔質構造の表面を親水性
から元の疎水性に変えてしまう。そのため、水の透過抵
抗が上がり、流量は徐々に低下していく。The second factor is the hydrophilic PT during drying.
This is the contraction of the volume of the FE porous membrane. When the hydrophilic PTFE porous membrane is dipped in an aqueous solution and then dried, the volume of the coating layer of the hydrophilic material decreases from several tenths to several hundreds of times when it is wet, and the shrinkage at this time occurs. The force causes the entire porous membrane to contract. In fact, when the porous membrane is shrunk in the aqueous solution and returned to the wet state, the contracted porous membrane returns to almost its original volume, and therefore the permeation resistance of the aqueous solution hardly increases. However, due to the large volume change of the porous film, peeling occurs between the coating layer of the hydrophilic material and the PTFE surface. The peeling of PTFE and the hydrophilic material caused by these two factors changes the surface of the microporous structure of the hydrophilic PTFE porous membrane from hydrophilic to original hydrophobic. Therefore, the permeation resistance of water increases and the flow rate gradually decreases.
【0008】本発明者らは、親水性PTFE多孔質膜の
出発材料として、アルコール/水の混合溶液を含浸した
状態(湿潤状態)で測定した場合と、含浸後に乾燥した
状態で測定した場合とで、表面積と膜厚とが実質的に変
化しないPTFE多孔質膜を使用し、さらには、PVA
などの親水性材料の塗布量や塗布法、架橋法などを工夫
することにより、前記目的を達成できることを見いだし
た。本発明の親水性PTFE多孔質膜は、イソプロピル
アルコール(以下、IPAと略記)と水との混合溶液に
浸漬し、乾燥する処理を行った後に測定したIPAの透
過流量と水の透過流量との比が、未処理のものについて
測定したIPAの透過流量と水の透過流量との比を高い
割合で保持している。つまり、本発明の親水性PTFE
多孔質膜は、体積収縮率が小さく、かつ、親水性材料の
塗布層の耐久性に優れている。本発明は、これらの知見
に基づいて完成するに至ったものである。[0008] The inventors of the present invention used the starting material for the hydrophilic PTFE porous membrane as a starting material when impregnated with a mixed solution of alcohol / water (wet state) and as a starting material after impregnation in a dried state. In addition, a PTFE porous membrane whose surface area and film thickness do not substantially change is used.
It was found that the above object can be achieved by devising the coating amount, coating method, crosslinking method, etc. of the hydrophilic material. The hydrophilic PTFE porous membrane of the present invention is immersed in a mixed solution of isopropyl alcohol (hereinafter, abbreviated as IPA) and water and dried to perform a treatment, followed by measuring the permeation flow rate of IPA and the permeation flow rate of water. The ratio holds a high ratio of the permeation flow rate of IPA and the permeation flow rate of water measured for the untreated one. That is, the hydrophilic PTFE of the present invention
The porous film has a small volume shrinkage and is excellent in durability of the coating layer of the hydrophilic material. The present invention has been completed based on these findings.
【0009】[0009]
【課題を解決するための手段】本発明によれば、四弗化
エチレン樹脂多孔質膜の微細多孔質構造の表面に架橋し
た親水性材料の塗布層が形成された親水性四弗化エチレ
ン樹脂多孔質膜であって、それぞれ差圧0.42kg/
cm2で測定したイソプロピルアルコール透過流量(m
l/cm2/min)に対する水透過流量(ml/cm2
/min)の比をA値とした場合、下記の関係式1を満
足するものであることを特徴とする親水性四弗化エチレ
ン樹脂多孔質膜が提供される。 A1/A0≧0.90 (1) A1:親水性四弗化エチレン樹脂多孔質膜をイソプロピ
ルアルコールと水との6:4(容量比)の混合溶液に浸
漬し、乾燥する処理を行った後のA値 A0:前記浸漬乾燥処理前の親水性四弗化エチレン樹脂
多孔質膜のA値According to the present invention, a hydrophilic tetrafluoroethylene resin having a coating layer of a crosslinked hydrophilic material formed on the surface of the microporous structure of a tetrafluoroethylene resin porous membrane is provided. Porous membrane with a differential pressure of 0.42 kg /
isopropyl alcohol permeation flow rate measured in cm 2 (m
Water permeation flow rate (ml / cm 2 / l / cm 2 / min)
/ Min) as an A value, a hydrophilic tetrafluoroethylene resin porous membrane satisfying the following relational expression 1 is provided. A 1 / A 0 ≧ 0.90 (1) A 1 : A treatment in which a hydrophilic tetrafluoroethylene resin porous membrane is immersed in a mixed solution of isopropyl alcohol and water at a volume ratio of 6: 4 and dried. A value after performing A 0 : A value of the hydrophilic tetrafluoroethylene resin porous film before the immersion drying treatment
【0010】また、本発明によれば、四弗化エチレン樹
脂多孔質膜の微細多孔質構造の表面に架橋した親水性材
料の塗布層が形成された親水性四弗化エチレン樹脂多孔
質膜の製造方法において、(1)四弗化エチレン樹脂多
孔質膜の微細多孔質構造内にアルコールを含浸させる工
程、(2)0.4〜1.0重量%の濃度の親水性材料の
水溶液を含浸させて前記アルコールを親水性材料で置換
する工程、(3)水に浸漬する工程、及び(4)含浸し
た親水性材料を架橋する工程を含むことを特徴とする親
水性四弗化エチレン樹脂多孔質膜の製造方法が提供され
る。Further, according to the present invention, there is provided a hydrophilic tetrafluoroethylene resin porous film having a coating layer of a crosslinked hydrophilic material formed on the surface of the fine porous structure of the tetrafluoroethylene resin porous film. In the manufacturing method, (1) a step of impregnating alcohol into the fine porous structure of the tetrafluoroethylene resin porous membrane, (2) impregnating an aqueous solution of a hydrophilic material with a concentration of 0.4 to 1.0% by weight. The hydrophilic tetrafluoroethylene resin porous material is characterized by including the steps of substituting the hydrophilic material with the alcohol, (3) immersing in water, and (4) crosslinking the impregnated hydrophilic material. A method of manufacturing a quality membrane is provided.
【0011】以下、本発明について詳述する。本発明で
使用するPTFE多孔質膜は、微細多孔質構造を有する
ものであれば特に限定されない。このようなPTFE多
孔質膜は、例えば、特公昭42−13560号公報に記
載の方法によって製造することができる。すなわち、先
ず、PTFEファインパウダーと潤滑剤との混合ペース
トを所定形状に成形する。ペースト押出に先立って、予
備成形を行ってもよい。カレンダーロールなどにより圧
延し、あるいはペースト押出後に圧延するなどして所定
形状に成形することもできる。成形体の形状は、シー
ト、チューブ、ロッド、ストリップ、フィルムなどがあ
る。この成形体は、潤滑剤を除去した後、あるいは除去
ぜずに、少なくとも一軸方向に延伸する。延伸後は、通
常、PTFEの融点である327℃以上に加熱し燒結す
る。延伸工程では、押出工程で圧着されたPTFEファ
インパウダー同士が延伸により離れて裂けるようにして
できた亀裂状の孔間に、糸を引くように微細な繊維が延
伸方向に形成される。このような微細繊維状構造が多孔
質構造を造る。PTFEファインパウダーやPTFEデ
ィスパージョン液に、溶媒や溶液に可溶な粒子を混練し
て所定形状に成形し、その後、粒子を溶解除去して多孔
質化したPTFE多孔質膜、あるいはこれを延伸したP
TFE多孔質膜なども使用することができる。PTFE
多孔質体の形状は、シート状、フィルム状、チューブ状
などのいずれでもよい。The present invention will be described in detail below. The PTFE porous membrane used in the present invention is not particularly limited as long as it has a fine porous structure. Such a PTFE porous membrane can be produced, for example, by the method described in Japanese Patent Publication No. 42-13560. That is, first, a mixed paste of PTFE fine powder and a lubricant is molded into a predetermined shape. Preforming may be performed prior to paste extrusion. It can be molded into a predetermined shape by rolling with a calendar roll or the like, or rolling after extruding the paste. The shape of the molded body includes a sheet, a tube, a rod, a strip, a film and the like. This molded body is stretched at least uniaxially after or without removing the lubricant. After stretching, it is usually heated to 327 ° C. or higher, which is the melting point of PTFE, and sintered. In the stretching step, fine fibers are formed in the stretching direction between the crack-shaped holes formed by allowing the PTFE fine powders pressed in the extrusion step to be separated and split by stretching. Such a fine fibrous structure creates a porous structure. A particle which is soluble in a solvent or a solution is kneaded with a PTFE fine powder or a PTFE dispersion liquid to form a predetermined shape, and then the particle is dissolved and removed to make a porous PTFE membrane, or this is stretched. P
A TFE porous membrane or the like can also be used. PTFE
The shape of the porous body may be any of a sheet shape, a film shape, a tube shape and the like.
【0012】本発明で使用する親水性材料としては、ポ
リビニルアルコール(PVA)、エチレンビニルアルコ
ール共重合体(EVOH)、アクリレート系樹脂などを
挙げることができる。これらの中でも、PVAは、その
水溶液をPTFE多孔質膜への含浸させるときに、微細
多孔質構造内のPTFE表面に吸着しやすく、かつ、水
溶液の濃度管理によって、均一で形状保持性の高い塗布
層を容易に形成することができるため、特に好ましい。
PVAとしては、平均重合度300〜2500で、けん
化度が85〜99%のものが好ましく使用することがで
きる。Examples of the hydrophilic material used in the present invention include polyvinyl alcohol (PVA), ethylene vinyl alcohol copolymer (EVOH), and acrylate resin. Among these, PVA is easily adsorbed on the PTFE surface in the fine porous structure when the aqueous solution of PTFE is impregnated into the porous PTFE membrane, and the PVA is applied uniformly and with high shape retention by controlling the concentration of the aqueous solution. It is particularly preferable because the layer can be easily formed.
PVA having an average degree of polymerization of 300 to 2500 and a degree of saponification of 85 to 99% can be preferably used.
【0013】本発明では、PTFE多孔質膜の微細多孔
質構造の表面に親水性材料の塗布層を形成し、かつ、塗
布した親水性材料を架橋して固定化する。微細多孔質構
造とは、例えば、微細な繊維(フィブリル)、あるいは
繊維−結節構造などからなる多孔性組織を意味し、その
表面とは、繊維や結節などを構成するPTFE表面を意
味する。したがって、PTFE多孔質膜の微細多孔質構
造の表面に親水性材料の塗布層を形成するには、通常、
PTFE多孔質膜を親水性材料の溶液中に浸漬して、多
孔性空間内に親水性材料を含浸させる。In the present invention, a coating layer of a hydrophilic material is formed on the surface of the microporous structure of the PTFE porous membrane, and the coated hydrophilic material is crosslinked and immobilized. The microporous structure means, for example, a porous structure composed of fine fibers (fibrils) or a fiber-nodule structure, and the surface thereof means the PTFE surface constituting the fibers or nodules. Therefore, in order to form a coating layer of a hydrophilic material on the surface of the fine porous structure of the PTFE porous membrane,
The PTFE porous membrane is dipped in a solution of hydrophilic material to impregnate the hydrophilic material into the porous space.
【0014】本発明の親水性PTFE多孔質膜は、それ
ぞれ差圧0.42kg/cm2で測定したIPAの透過
流量に対する水の透過流量の比をA値とした場合、下記
の関係式1を満足するものである。 A1/A0≧0.90 (1) A1:親水性PTFE多孔質膜をIPAと水との6:4
(容量比)の混合溶液(60%IPA水溶液)に浸漬
し、乾燥する処理を行った後のA値 A0:前記浸漬乾燥処理前の親水性四弗化エチレン樹脂
多孔質膜のA値 A=水の透過流量/IPAの透過流量(差圧0.42k
g/cm2で測定) 各透過流量は、差圧0.42kg/cm2、常温の条件
下で、1分間の当りのIPAまたは水の透過流量(単
位:ml/cm2/min)を測定するか、あるいは測
定値を前記単位に換算する。また、A1/A0=Bと置い
て、以下、この値をB値と称することがある。このB値
が大きいほど、親水性材料の塗布層の耐久性が優れてい
ることを示す。本発明の親水性PTFE多孔質膜は、こ
のB値が0.90以上を示す。When the ratio of the permeation flow rate of water to the permeation flow rate of IPA measured at a differential pressure of 0.42 kg / cm 2 is taken as the A value, the hydrophilic PTFE porous membrane of the present invention has the following relational expression 1. I am satisfied. A 1 / A 0 ≧ 0.90 (1) A 1 : A hydrophilic PTFE porous membrane composed of IPA and water 6: 4.
A value after dipping in a mixed solution (volume ratio) (60% IPA aqueous solution) and drying A 0 : A value of hydrophilic tetrafluoroethylene resin porous membrane before dipping and drying treatment A = Permeate flow rate of water / Permeate flow rate of IPA (Differential pressure 0.42k
Measured in g / cm 2 ) For each permeation flow rate, measure the permeation flow rate (unit: ml / cm 2 / min) per minute of IPA or water under conditions of differential pressure 0.42 kg / cm 2 and room temperature Or convert the measured value to the above unit. Also, assuming that A 1 / A 0 = B, this value may be hereinafter referred to as a B value. The larger the B value, the better the durability of the coating layer of the hydrophilic material. The B value of the hydrophilic PTFE porous membrane of the present invention is 0.90 or more.
【0015】親水性材料がPTFE表面と密着し、剥離
しないようにするには、第一に、親水性材料の塗布層に
強固な形状保持性を付与する必要がある。そのために
は、親水性材料をPTFE多孔質膜の微細多孔質構造の
表面に均一に塗布し、かつ、塗布した親水性材料を架橋
して固定する必要がある。この形状保持性を強くするに
は、親水性材料を厚く塗布すればよいが、親水性材料の
塗布層があまり厚くなると、PTFE多孔質膜の孔が目
詰まりを起こしてしまう。したがって、親水性材料の塗
布層の厚みをある範囲内に制御する必要がある。In order to prevent the hydrophilic material from adhering to the surface of PTFE and preventing it from peeling off, it is first necessary to impart a strong shape-retaining property to the coating layer of the hydrophilic material. For that purpose, it is necessary to uniformly apply the hydrophilic material to the surface of the microporous structure of the PTFE porous membrane, and to crosslink and fix the applied hydrophilic material. In order to enhance the shape-retaining property, it is sufficient to apply the hydrophilic material thickly, but if the coating layer of the hydrophilic material becomes too thick, the pores of the PTFE porous membrane will be clogged. Therefore, it is necessary to control the thickness of the coating layer of the hydrophilic material within a certain range.
【0016】親水性材料の好ましい塗布量は、PTFE
多孔質膜の微細多孔質構造の表面積によって変動する。
この微細多孔質構造の表面積は、PTFE多孔質膜の気
孔率と相関関係を有している。本発明者らは、耐久性に
優れた親水性PTFE多孔質膜を作成するには、気孔率
が60%以上、好ましくは60〜80%のPTFA多孔
質膜を使用することが望ましいこと、そして、気孔率と
の関係で親水性材料の塗布量の最適化を図ることが望ま
しいことを見いだした。すなわち、気孔率が60%以上
のPTFE多孔質膜を使用し、PTFE多孔質膜に対す
る親水性材料の塗布量を下記の関係式2を満足するよう
に調整すると、耐久性に優れた親水性材料層を有し、水
透過流量維持性及び耐薬品性に優れた親水性PTFE多
孔質膜を得ることができる。 (C/5)−11.5≦D≦(C/5)−9.5 (2) C:四弗化エチレン樹脂多孔質膜の気孔率(%) D:(親水性材料の塗布重量/四弗化エチレン樹脂多孔
質膜重量)×100The preferred coating amount of the hydrophilic material is PTFE.
It depends on the surface area of the microporous structure of the porous membrane.
The surface area of this fine porous structure has a correlation with the porosity of the PTFE porous membrane. The present inventors prefer to use a PTFA porous membrane having a porosity of 60% or more, preferably 60 to 80%, in order to produce a hydrophilic PTFE porous membrane having excellent durability, and It was found that it is desirable to optimize the coating amount of the hydrophilic material in relation to the porosity. That is, when a PTFE porous film having a porosity of 60% or more is used and the coating amount of the hydrophilic material on the PTFE porous film is adjusted so as to satisfy the following relational expression 2, the hydrophilic material having excellent durability is obtained. A hydrophilic PTFE porous membrane having a layer and excellent in water permeation flow rate maintenance and chemical resistance can be obtained. (C / 5) -11.5 ≦ D ≦ (C / 5) -9.5 (2) C: Porosity (%) of porous tetrafluoroethylene resin membrane D: (Coating weight of hydrophilic material / Polytetrafluoroethylene resin porous membrane weight) x 100
【0017】PTFE多孔質膜の気孔率が低いほど、親
水性材料の塗布量が少なく、逆に、気孔率が高くなるほ
ど、塗布量が多くなるが、その範囲は、上記関係式2で
規定される範囲内にあるべきである。図3は、実施例1
〜6と比較例1〜6で得られた各親水性PTFE多孔質
膜(親水化シート)の気孔率とPVA塗布量との関係を
示すグラフである。同様の方法でPVA塗布PTFE多
孔質膜を作成しても、PVA塗布量が上記関係式2を満
足しない場合(比較例)には、耐久性に優れた親水性P
TFE多孔質膜を得ることはできない。気孔率に関連す
る親水性材料の塗布量が少なすぎると、親水性が不十分
となり、強固な塗布層を形成することも困難となり、逆
に、多すぎると、孔の目詰まりや浸漬時と乾燥時におけ
る多孔質膜の体積変化の要因となる。親水性材料の塗布
量を前記関係式2を満足するように調整する方法として
は、後述するように、親水性PTFE多孔質膜の製造工
程において、含浸工程で使用する親水性材料の水溶液濃
度を特定の範囲に調整し、さらには、含浸工程と架橋工
程の間に、水に浸漬して洗浄を行う方法が挙げられる。The lower the porosity of the PTFE porous membrane, the smaller the coating amount of the hydrophilic material, and conversely, the higher the porosity, the larger the coating amount. The range is defined by the above relational expression 2. It should be within the range. FIG. 3 shows the first embodiment.
6 is a graph showing the relationship between the porosity of each hydrophilic PTFE porous membrane (hydrophilized sheet) obtained in Comparative Examples 1 to 6 and the PVA coating amount. Even if a PVA-coated PTFE porous membrane is prepared by the same method, if the PVA coating amount does not satisfy the above relational expression 2 (Comparative Example), hydrophilic P excellent in durability is obtained.
It is not possible to obtain a TFE porous membrane. If the coating amount of the hydrophilic material related to the porosity is too small, the hydrophilicity will be insufficient, and it will be difficult to form a strong coating layer. Conversely, if it is too large, the pores will be clogged or when immersed. This causes a change in the volume of the porous membrane during drying. As a method of adjusting the coating amount of the hydrophilic material so as to satisfy the relational expression 2, as will be described later, in the manufacturing process of the hydrophilic PTFE porous membrane, the concentration of the aqueous solution of the hydrophilic material used in the impregnation process is adjusted. There is a method of adjusting to a specific range and further immersing in water for washing between the impregnation step and the crosslinking step.
【0018】本発明の親水性PTFE多孔質膜は、60
%IPA水溶液に湿潤した状態で測定した表面積
(S0)及び膜厚(d0)と、60%IPA水溶液を含浸
後、乾燥させてから測定した表面積(S1)及び膜厚
(d1)との間に、それぞれ以下の関係式3及び4が成
立する点にも特徴を有する。 |〔(S1−S0)/S0〕×100|≦2% (3) |〔(d1−d0)/d0〕×100|≦2% (4) 上記の関係式は、湿潤時の表面積(S0)及び膜厚
(d0)の測定に際し、60%IPA水溶液に代えて、
水やIPAなどの有機溶媒に湿潤させた場合にも成立す
る。また、各表面積(S0、S1)及び膜厚(d0、d1)
の測定に際し、60%IPA水溶液に代えて、水または
IPAなどの有機溶媒をそれぞれ単独で使用した場合に
も一般に成立する。PVAは、水以外の溶媒には殆ど溶
解せず、一方、IPAは、PTFEと最も親和性の高い
溶媒のひとつである。水とIPAの混合溶液は、IPA
の割合が60%未満では疎水性のPTFEを濡らすこと
ができない。したがって、60%IPA水溶液は、PV
A塗布PTFE多孔質膜と最も親和性が高く、この水溶
液を用いて試験を行うことは、PVAとPTFEとの層
間剥離の観点からは、最も厳しい条件下での試験に該当
する。PVA以外の親水性材料を用いる場合についても
同様のことがいえる。従来のPVA塗布PTFE多孔質
膜は、乾燥時に体積が収縮するため、湿潤時と乾燥時と
では、多孔質膜の表面積と膜厚が大きく異なる。これに
対して、本発明品は、湿潤時と乾燥時における体積変化
が少なく、親水性材料の塗布層の剥離が防止されてい
る。The hydrophilic PTFE porous membrane of the present invention comprises 60
% Surface area (S 0 ) and film thickness (d 0 ) measured in a wet state with an IPA aqueous solution, and surface area (S 1 ) and film thickness (d 1 ) measured after drying after impregnation with a 60% IPA aqueous solution It is also characterized in that the following relational expressions 3 and 4 are established between and. | [(S 1 −S 0 ) / S 0 ] × 100 | ≦ 2% (3) | [(d 1 −d 0 ) / d 0 ] × 100 | ≦ 2% (4) The above relational expression is When measuring the surface area (S 0 ) and film thickness (d 0 ) when wet, instead of the 60% IPA aqueous solution,
This is also true when wetted with an organic solvent such as water or IPA. Further, each surface area (S 0 , S 1 ) and film thickness (d 0 , d 1 )
In general, it also holds true when water or an organic solvent such as IPA is used alone instead of the 60% IPA aqueous solution. PVA is almost insoluble in solvents other than water, while IPA is one of the solvents with the highest affinity for PTFE. The mixed solution of water and IPA is IPA
If the ratio is less than 60%, the hydrophobic PTFE cannot be wetted. Therefore, 60% IPA aqueous solution
The A-coated PTFE porous film has the highest affinity, and performing the test using this aqueous solution corresponds to the test under the most severe conditions from the viewpoint of delamination between PVA and PTFE. The same applies to the case of using a hydrophilic material other than PVA. Since the volume of the conventional PVA-coated PTFE porous film shrinks during drying, the surface area and the film thickness of the porous film greatly differ between when wet and when dry. On the other hand, the product of the present invention has little volume change between wet and dry, and peeling of the coating layer of the hydrophilic material is prevented.
【0019】図1は、従来技術によって得られたPVA
塗布PTFE多孔質膜を60%IPA水溶液に浸漬し、
非拘束で乾燥する操作(浸漬−乾燥サイクル)を繰り返
した場合におけるPTFE多孔質膜の表面積と膜厚の変
化、及び差圧0.42kg/cm2で測定した水透過流
量の変化を表わすグラフである。図2は、本発明品につ
いて、同様に浸漬−乾燥サイクルを繰り返した場合にお
けるPTFE多孔質膜の表面積と膜厚の変化、及び水透
過流量の変化を表わすグラフである。先ず、親水性PT
FE多孔質膜を用いて、水透過流量を測定し、水に
湿潤状態で表面積と膜厚を測定し、60%IPA水溶
液に浸漬した後、乾燥し、乾燥状態で表面積と膜厚を
測定し、次に、の水透過流量の測定に戻るサイクルを
繰り返した。上記の湿潤状態での表面積と膜厚の測定
は、の60%IPA水溶液に浸漬した後、乾燥前の6
0%IPA水溶液に湿潤状態で測定してもよい。FIG. 1 shows the PVA obtained by the prior art.
Immerse the coated PTFE porous membrane in a 60% IPA aqueous solution,
FIG. 3 is a graph showing changes in surface area and film thickness of a PTFE porous membrane and changes in water permeation flow rate measured at a differential pressure of 0.42 kg / cm 2 in the case where a non-constrained drying operation (immersion-drying cycle) is repeated. is there. FIG. 2 is a graph showing changes in surface area and film thickness of the PTFE porous membrane and changes in water permeation flow rate when the immersion-drying cycle was similarly repeated for the product of the present invention. First, hydrophilic PT
Using a FE porous membrane, the water permeation flow rate was measured, the surface area and the film thickness were measured in a wet state with water, and the sample was immersed in a 60% IPA aqueous solution and then dried, and the surface area and the film thickness were measured in a dried state. Then, the cycle of returning to the measurement of the water permeation flow rate was repeated. The measurement of the surface area and the film thickness in the above-mentioned wet state was carried out by immersing in 60% IPA aqueous solution and
It may be measured in a 0% IPA aqueous solution in a wet state.
【0020】図1から明らかなように、従来品は、湿潤
時と乾燥時における表面積及び膜厚の変化が大きく、か
つ、浸漬−乾燥サイクルを繰り返すにしたがって、水透
過流量が大きく低減する。これに対して、図2から明ら
かなように、本発明品は、浸漬時と乾燥時における表面
積及び膜厚の変化が極めて小さく、しかも、浸漬−乾燥
サイクルを繰り返しても、水透過流量が大きく変化する
ことなく、高水準を維持している。なお、従来品は、住
友電工(株)製ポアフロンシートWP−020−40
(気孔率75%)に、IPAを含浸させた後、2.5重
量%PVA水溶液を含浸させてIPAをPVAで置換
し、次いで、PVAを電子線架橋させたものである。As is apparent from FIG. 1, the conventional product has a large change in surface area and film thickness between wet and dry, and the water permeation flow rate greatly decreases as the dipping-drying cycle is repeated. On the other hand, as is apparent from FIG. 2, the product of the present invention has a very small change in surface area and film thickness during immersion and drying, and has a large water permeation flow rate even after repeated immersion-drying cycles. It remains high, unchanged. The conventional product is a Pore Clon sheet WP-020-40 manufactured by Sumitomo Electric Industries, Ltd.
(Porosity of 75%) is impregnated with IPA, then impregnated with a 2.5 wt% PVA aqueous solution to replace IPA with PVA, and then PVA is electron beam crosslinked.
【0021】本発明の親水性PTFE多孔質膜は、以下
の(1)〜(4)の工程により製造することができる。 (1)四弗化エチレン樹脂多孔質膜の微細多孔質構造内
にアルコールを含浸させる工程、(2)0.4〜1.0
重量%の濃度の親水性材料の水溶液を含浸させて前記ア
ルコールを親水性材料で置換する工程、(3)水に浸漬
する工程、及び(4)含浸した親水性材料を架橋する工
程。The hydrophilic PTFE porous membrane of the present invention can be manufactured by the following steps (1) to (4). (1) a step of impregnating alcohol into the fine porous structure of the tetrafluoroethylene resin porous membrane, (2) 0.4 to 1.0
A step of impregnating an aqueous solution of a hydrophilic material with a concentration of wt% to replace the alcohol with the hydrophilic material, (3) a step of immersing in water, and (4) a step of crosslinking the impregnated hydrophilic material.
【0022】PTFEは疎水性が高いため、直接、親水
性材料の水溶液に浸漬しても、親水性材料を微細多孔質
構造の内部にまで含浸させることはできない。親水性材
料の水溶液を真空状態で含浸させても、微細多孔質構造
内には侵入しない。したがって、水に相溶性のあるアル
コール(例:イソプロピルアルコール)で一旦微細多孔
質構造内を充満させたあとに、多量の親水性材料の水溶
液中に浸漬し、含浸したアルコールを親水性材料により
置換含浸することが必要になるPTFE多孔質膜の微細
多孔質構造の表面に親水性材料を制御された塗布量で塗
布するには、親水性材料の水溶液濃度を0.4〜1.0
重量%の比較的低濃度に調節することが必要である。こ
の濃度が低すぎると、親水性の度合や塗布層の形状保持
性が低下し、高すぎると、孔の目詰まりや浸漬時と乾燥
時における多孔質膜の体積変化が大きくなる。Since PTFE has a high hydrophobicity, even if it is directly immersed in an aqueous solution of a hydrophilic material, the hydrophilic material cannot be impregnated into the inside of the fine porous structure. Even if the aqueous solution of the hydrophilic material is impregnated in a vacuum state, it does not penetrate into the fine porous structure. Therefore, once the microporous structure is filled with an alcohol compatible with water (eg, isopropyl alcohol), it is immersed in a large amount of an aqueous solution of a hydrophilic material, and the impregnated alcohol is replaced with the hydrophilic material. To apply the hydrophilic material in a controlled coating amount on the surface of the microporous structure of the PTFE porous membrane that needs to be impregnated, the aqueous concentration of the hydrophilic material is 0.4 to 1.0.
It is necessary to adjust to a relatively low concentration by weight. If this concentration is too low, the degree of hydrophilicity and shape retention of the coating layer will be reduced, and if it is too high, pores will be clogged and the volume change of the porous membrane during dipping and drying will be large.
【0023】ところで、親水性材料の塗布層の厚みは、
PTFE多孔質膜の孔径にも関連するものと推定され
る。これは、PTFE多孔質膜の微細多孔質構造と親水
性材料の固定が、部分的な双方の物理的吸着だけでな
く、複雑な多孔質構造同士の絡み合いの効果があるため
である。すなわち、孔径が小さい、より微細な多孔質構
造の表面に沿って形成される親水性材料の塗布層は、形
状が複雑で微細なものとなり、PTFE多孔質膜と複雑
に絡み合うのに対し、孔径が大きいと多孔質構造も粗と
なり、1本1本のPTFEの繊維の太さや長さも大きく
なるため、形状による絡み合いの効果が減ると推定され
る。発明者らの検討結果では、孔径が0.数μ相当の膜
では、親水性材料の最適濃度幅は、0.4〜1.0重量
%まで比較的広いが、1μmを越える孔径ものは、低濃
度による形状保持性不足や高濃度による目詰まりが発生
しやすく、0.75重量%付近の濃度の水溶液を使用す
ることが好ましいことがわかった。By the way, the thickness of the coating layer of the hydrophilic material is
It is presumed that it is also related to the pore size of the PTFE porous membrane. This is because the microporous structure of the PTFE porous membrane and the hydrophilic material are fixed not only partially by physical adsorption, but also by entanglement of complicated porous structures. That is, the coating layer of the hydrophilic material formed along the surface of the finer porous structure having a smaller pore diameter has a complicated and fine shape and is complicatedly entangled with the PTFE porous membrane, whereas Is large, the porous structure also becomes rough, and the thickness and length of each PTFE fiber become large, and it is presumed that the effect of entanglement due to the shape is reduced. According to the results of the study by the inventors, the pore size is 0. In the case of a membrane equivalent to several μ, the optimum concentration range of the hydrophilic material is relatively wide from 0.4 to 1.0% by weight. It was found that clogging is likely to occur and it is preferable to use an aqueous solution having a concentration near 0.75% by weight.
【0024】本発明では、PTFE多孔質膜を親水性材
料の水溶液に浸漬して、親水性材料を含浸した後、水に
浸漬して洗浄する工程を採用する。この水洗工程を省略
すると、その他の工程や使用材料を同じにしても、高い
水透過流量を得ることが困難となる。この水洗工程によ
り、親水性材料の塗布量の最適化を行うことができ、ま
た、余分な残存アルコールを除去することができる。親
水性材料を含浸したPTFE多孔質膜を水に浸漬する方
法としては、切断した各枚葉を水中に浸漬する方法、ロ
ールに巻いた多孔質膜を巻き戻して順次水中に浸漬させ
た後、再び別のロールに巻き取る方法、ロールに巻いた
多孔質膜を水中にある別のロールに巻き取る方法などが
挙げられる。親水性材料を含浸したPTFE多孔質膜を
水に浸漬する時間は、通常、30秒間以上であり、1分
間程度までで十分である。所望により1分間以上、例え
ば、1時間あるいは24時間程度浸漬してもよいが、長
時間浸漬しても効果が飽和するため効率的ではない。In the present invention, a step of immersing the PTFE porous membrane in an aqueous solution of a hydrophilic material to impregnate the hydrophilic material, and then immersing it in water to wash it is adopted. If this washing step is omitted, it will be difficult to obtain a high water permeation flow rate even if the other steps and materials used are the same. By this water washing step, the coating amount of the hydrophilic material can be optimized, and the excess residual alcohol can be removed. As a method of immersing the PTFE porous membrane impregnated with a hydrophilic material in water, a method of immersing each cut sheet in water, a method of rewinding the porous membrane wound on a roll and successively immersing in water, Examples thereof include a method of rewinding on another roll and a method of winding the porous film wound on a roll on another roll in water. The time for immersing the PTFE porous membrane impregnated with the hydrophilic material in water is usually 30 seconds or more, and about 1 minute is sufficient. If desired, it may be dipped for 1 minute or more, for example, for about 1 hour or 24 hours, but if it is dipped for a long time, the effect is saturated and it is not efficient.
【0025】本発明における親水性材料の架橋方法に
は、電子線などの電離性放射線による照射架橋、熱架
橋、あるいは架橋剤を用いた化学架橋などの各種の方法
がある。これらの架橋法の中でも、架橋の確実性から
は、架橋剤を用いた化学架橋が適している。親水性材料
としてPVAを使用すると、PTFE多孔質膜に含浸塗
布した状態が常温の水溶液中で非常に安定している。と
ころが、加熱架橋や嫌気的に行う照射架橋では、PVA
の吸着状態を乱したり、あるいはPTFE自身を低強度
化するなどのデメリットを持つのに対して、化学架橋
は、水溶液中での架橋が可能である。There are various methods for crosslinking the hydrophilic material in the present invention, such as irradiation crosslinking by ionizing radiation such as electron beam, thermal crosslinking, or chemical crosslinking using a crosslinking agent. Among these crosslinking methods, chemical crosslinking using a crosslinking agent is suitable from the viewpoint of reliability of crosslinking. When PVA is used as the hydrophilic material, the state in which the PTFE porous membrane is impregnated and coated is very stable in an aqueous solution at room temperature. However, in the case of heat crosslinking or irradiation crosslinking performed anaerobically, PVA is used.
However, the chemical cross-linking is possible in an aqueous solution.
【0026】特に、酸触媒下に、架橋剤としてグルタル
アルデヒドやテレフタルアルデヒドを用いて行う架橋法
は、常温で反応性が高く、架橋量が一定量に安定する反
応であり、架橋点であるアセタール結合も比較的耐薬品
性が高いことから、特に本発明の目的に適する方法であ
る。さらに、これらのアルデヒド類による架橋が、特に
親水性PTFE多孔質膜の製造に有利な点は、架橋にア
ルコールの影響を受けない点である。工程(1)で含浸
したアルコールは、工程に(2)において、親水性材料
により置換され、さらに、水洗工程(3)でも洗浄除去
されるが、PTFE多孔質膜の微細多孔質構造から完全
に取り除くのは容易ではない。In particular, the cross-linking method using glutaraldehyde or terephthalaldehyde as a cross-linking agent in the presence of an acid catalyst is a reaction which is highly reactive at room temperature and stabilizes the cross-linking amount to a certain amount, and is the acetal which is the cross-linking point. Bonding is also a method particularly suitable for the purpose of the present invention because it has relatively high chemical resistance. Furthermore, the advantage that the crosslinking with these aldehydes is particularly advantageous for the production of the hydrophilic PTFE porous membrane is that the crosslinking is not affected by alcohol. The alcohol impregnated in the step (1) is replaced by the hydrophilic material in the step (2) and further removed by washing in the water washing step (3). However, the alcohol is completely removed from the fine porous structure of the PTFE porous membrane. It's not easy to remove.
【0027】本発明者らの検討結果では、例えば、PT
FE多孔質膜の置換含浸の際に一般的に使用されている
IPAと、親水性材料としてPVAを使用した場合、電
子線による架橋では、残存IPAの濃度を0.1重量%
以下にしないと架橋に影響がある。微細多孔質構造内の
IPA濃度を安定に0.1重量%以下にするには、膜面
積50m2当り1時間の水洗を3回以上行う必要があ
る。ところが、グルタルアルデヒドやテレフタルアルデ
ヒドを用いて行う架橋の場合、数重量%のIPAが存在
していても架橋に影響が殆ど出ない。本発明では、前記
工程(1)〜(4)の4つの工程が順に行われることが
少なくとも必要であるが、これらの工程のうち、工程
(2)及び(3)などは、効果を確実にするため繰り返
してもよい。ただし、先に述べたようにPVAをアルデ
ヒド類で架橋する場合には、各工程を1回づつ順に行う
ことで十分である。According to the results of the examination by the present inventors, for example, PT
When IPA that is generally used for displacement impregnation of the FE porous membrane and PVA as the hydrophilic material are used, the concentration of residual IPA is 0.1% by weight when crosslinked by electron beam.
Unless below, crosslinking is affected. In order to stably keep the IPA concentration in the fine porous structure at 0.1% by weight or less, it is necessary to perform water washing for 1 hour per membrane area of 50 m 2 three times or more. However, in the case of cross-linking using glutaraldehyde or terephthalaldehyde, the cross-linking is hardly affected even if several wt% of IPA is present. In the present invention, it is at least necessary that the four steps (1) to (4) be performed in order, but among these steps, the steps (2) and (3) ensure the effect. You may repeat to do this. However, as mentioned above, when PVA is crosslinked with aldehydes, it is sufficient to perform each step once in order.
【0028】本発明の親水性PTFE多孔質膜は、前記
したとおり、乾燥による体積(膜の表面積と膜厚)の収
縮が抑制されている。乾燥時の多孔質膜の収縮は、PT
FEと親水化材料の剥離原因の一つである、乾燥による
多孔質膜の収縮現象自体は、気孔率や孔径が小さくなっ
て、液体の透過抵抗の増大をもたらすものではない。図
1には、一般的なPVA塗布PTFE多孔質膜を60%
IPA水溶液に浸漬した後、非拘束で乾燥させたときの
見かけの表面積及び膜厚の変化の一例が示されている。
乾燥時に多孔質膜が収縮しても、再び水に浸漬すると元
の体積にほぼ復元するため、透過流量に対する妨げにな
るとはいえない。As described above, the hydrophilic PTFE porous membrane of the present invention is suppressed in shrinkage of the volume (membrane surface area and membrane thickness) due to drying. The shrinkage of the porous film during drying is PT
The contraction phenomenon of the porous membrane due to drying, which is one of the causes of separation between the FE and the hydrophilic material, does not bring about an increase in liquid permeation resistance due to a decrease in porosity and pore diameter. Figure 1 shows 60% of a general PVA coated PTFE porous membrane.
An example of changes in the apparent surface area and film thickness when the film is unconstrained and dried after being immersed in the IPA aqueous solution is shown.
Even if the porous membrane shrinks during drying, it cannot be said that it impedes the permeation flow rate because it is almost restored to its original volume when immersed in water again.
【0029】濾過膜は、通常、プリーツ状に折り畳んで
カートリッジ化するにしても、平膜で使用されるにして
も、面積が変化しないように支持された状態で使用され
るため、大きな面積変化は起こり得ない。したがって、
従来、膜面積の収縮は、専ら組立加工上の問題と考えら
れてきた。さらに、この収縮現象は、通常の疎水性のP
TFE膜ではさほど大きくない。これに対して、親水性
材料を塗布した多孔質膜においては、水に濡れて膨潤し
ていた親水性材料が乾燥時に数十分の一から数百分の一
程度に収縮することによって、PTFE多孔質膜単独の
場合に比べて、かなり大きな収縮力が働く。したがっ
て、前記のような乾燥時の収縮現象は、親水性材料を用
いた親水性PTFE多孔質膜に特有の現象であるといえ
る。The filtration membrane is usually used in a supported state so that its area does not change, whether it is folded into a cartridge by pleating it or used as a flat membrane. Cannot happen. Therefore,
Conventionally, the shrinkage of the membrane area has been considered to be a problem in the assembling process. Furthermore, this contraction phenomenon is caused by the usual hydrophobic P
The TFE film is not so large. On the other hand, in the porous film coated with the hydrophilic material, the hydrophilic material that has been swollen by being wetted with water shrinks to about several tenths to several hundredths when it is dried. A considerably large contraction force works as compared with the case of using the porous film alone. Therefore, it can be said that the above-described shrinkage phenomenon during drying is a phenomenon peculiar to the hydrophilic PTFE porous membrane using the hydrophilic material.
【0030】本発明者らは、一見無関係に見えるこの多
孔質膜の乾燥による収縮と水透過流量低下との関係につ
いて、鋭意研究の結果、流量低下は、親水性材料の収縮
による形状変化によってPTFEと親水性材料の塗布層
がずれていき、PTFEが表面に剥き出しになることに
よると考えた。そこで、水溶液あるいは有機溶媒を含浸
した状態での膜の表面積(S0)及び膜厚(d0)と、こ
れを乾燥させたときの膜の表面積(S1)及び膜厚
(d1)とが実質的に変化しない親水性PTFE多孔質
膜を開発し、この多孔質膜について図1同様の評価を行
ったところ、図2に示すように水透過流量の低下が抑制
されることを見いだした。The present inventors have earnestly studied the relationship between the shrinkage of the porous membrane due to drying and the decrease in the water permeation flow rate, which seemed to be unrelated. It was considered that the coating layer of the hydrophilic material was displaced and the PTFE was exposed on the surface. Then, the surface area (S 0 ) and film thickness (d 0 ) of the film in the state of being impregnated with the aqueous solution or the organic solvent, and the surface area (S 1 ) and film thickness (d 1 ) of the film when dried. When a hydrophilic PTFE porous membrane having substantially no change was developed and this porous membrane was evaluated in the same manner as in FIG. 1, it was found that the decrease in water permeation flow rate was suppressed as shown in FIG. .
【0031】水透過流量の低下は、前記式3及び4の関
係が成立するような実質的に乾燥状態と湿潤状態とで体
積変化がない多孔質膜であれば起こらないが、図1に示
すように、外観上は殆ど収縮していないように見える1
0%程度の膜の表面積あるいは膜厚の変化により、水透
過流量低下が明らかに認められるようになることがわか
った。膜の表面積や膜厚が数10%も変化すれば、水を
殆ど透過しなくなる場合もある。面積収縮する膜は、厚
み方向の収縮も起こすため、カートリッジ化して面積変
化を防いでも、厚み方向に拘束することは不可能なの
で、乾燥時に収縮してしまう膜は、流量低下を起こす結
果となる。The decrease in the water permeation flow rate does not occur in a porous membrane which does not substantially change in volume between a dry state and a wet state so that the relations of the equations 3 and 4 are established, but it is shown in FIG. So it looks like it has almost no shrinkage 1
It was found that a decrease in the water permeation flow rate became apparent when the surface area or the thickness of the membrane changed by about 0%. If the surface area of the membrane or the membrane thickness changes by several tens of percent, it may become almost impermeable to water. A film that shrinks in the area also causes shrinkage in the thickness direction, so it is impossible to constrain it in the thickness direction even if it is made into a cartridge to prevent area changes, so a film that shrinks during drying will result in a decrease in the flow rate. .
【0032】本発明の乾燥時と湿潤時の体積変化のない
親水性PTFE多孔質膜を製造するためには、PTFE
多孔質膜として、60%IPA水溶液で湿潤した状態で
測定した表面積(SA)及び膜厚(dA)と、該水溶液を
含浸後、乾燥させてから測定した該膜の表面積(SB)
及び膜厚(dB)との間に、それぞれ以下の関係式5及
び6が成立するものを使用することが好ましい。 |〔(SB−SA)/SA〕×100|≦2% (5) |〔(dB−dA)/dA〕×100|≦2% (6) このようなPTFE多孔質膜は、通常の延伸法で得られ
たPTFE多孔質膜を拘束下に熱処理して、延伸による
歪みを緩和することにより得ることができる。具体的に
は、PTFE多孔質膜を金属板(金属ベルトやシートな
どを含む)に圧着状態で融点以上に加熱することにより
得ることができる。PTFE多孔質膜の製造工程におい
て、延伸工程の後に、このような加熱工程を配すること
が好ましい。加熱処理は、例えば、延伸法により得られ
たPTFE多孔質膜をステンレスベルトに面圧1〜30
kg/cm2、好ましくは5〜15kg/cm2で圧着し
た後、ベルトを290〜380℃、好ましくは300〜
360℃で、30秒間〜5分間程度加熱することにより
行うことができる。In order to produce the hydrophilic PTFE porous membrane of the present invention, which does not have a change in volume during dry and wet, PTFE is used.
As the porous membrane, the surface area (S A ) and the membrane thickness (d A ) measured in a state of being wet with a 60% IPA aqueous solution, and the surface area (S B ) of the membrane measured after the aqueous solution was impregnated and dried.
And the film thickness (d B ), the following relational expressions 5 and 6 are preferably satisfied. | [(S B -S A) / S A ] × 100 | ≦ 2% (5 ) | [(d B -d A) / d A ] × 100 | ≦ 2% (6 ) such porous PTFE The membrane can be obtained by heat-treating a PTFE porous membrane obtained by an ordinary stretching method under restraint to relax strain due to stretching. Specifically, it can be obtained by heating the PTFE porous film to a metal plate (including a metal belt, a sheet, etc.) in a pressure-bonded state to a temperature equal to or higher than the melting point. In the manufacturing process of the PTFE porous membrane, it is preferable to arrange such a heating process after the stretching process. The heat treatment is carried out, for example, by applying a PTFE porous film obtained by a stretching method to a stainless belt with a surface pressure of 1 to 30.
After pressure bonding with kg / cm 2 , preferably 5-15 kg / cm 2 , the belt is 290-380 ° C., preferably 300-
It can be performed by heating at 360 ° C. for about 30 seconds to 5 minutes.
【0033】このような製法にて得られたPTFE多孔
質膜は、延伸による歪みが加熱工程で緩和されているた
め、PTFE多孔質膜のみの状態でも、溶媒などへの湿
潤時の面積と、乾燥時の面積との間に変化が殆どない。
さらに、加熱処理したPTFE多孔質膜は、金属ベルト
等への圧着時に圧縮されるために、膜厚方向にはむしろ
拡大しやすい傾向をもち、それによって、親水性材料の
収縮力に耐えうる形状保持強度が付与されている。この
形状保持性は、先に述べた親水性材料の塗布層が強度の
強い層として形成された場合、乾燥時の収縮力も強くな
るため、特に必要となってくる。本発明品は、従来の同
様の親水性PTFE多孔質体に比べ、経時による水透過
流量の低下が殆どなく、有機溶媒、アルカリ、酸などに
対する耐薬品性にも優れたものであり、特に、分離膜用
途として好適に用いることができる。In the PTFE porous membrane obtained by such a manufacturing method, the strain due to stretching is relaxed in the heating step. Therefore, even in the state of only the PTFE porous membrane, the area when wet with a solvent or the like, There is almost no change from the dry area.
Furthermore, since the heat-treated PTFE porous film is compressed during pressure bonding to a metal belt or the like, it tends to expand in the film thickness direction, and as a result, a shape that can withstand the shrinking force of the hydrophilic material. Holding strength is given. This shape-retaining property is particularly necessary because when the coating layer of the hydrophilic material described above is formed as a layer having high strength, the shrinkage force during drying also becomes strong. The product of the present invention has almost no decrease in the water permeation flow rate with time as compared with the similar hydrophilic PTFE porous body of the related art, and has excellent chemical resistance to organic solvents, alkalis, acids and the like. It can be suitably used as a separation membrane application.
【0034】[0034]
【実施例】以下、本発明について、実施例及び比較例を
挙げて具体的に説明するが、本発明は、これらの実施例
のみに限定されるものではない。EXAMPLES The present invention will be specifically described below with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples.
【0035】[実施例1〜7、比較例1〜9]実施例1
〜7及び比較例1〜9の親水性PTFE多孔質膜は、全
て、PTFE多孔質基材(PTFE基膜)にPVAを含
浸した後、PVAを架橋したものであり、以下に示す各
材料及び方法の中のいずれかの方法を選択して作製し
た。各例での選択した材料及び方法は、表1に示す通り
である。[Examples 1 to 7, Comparative Examples 1 to 9] Example 1
7 to 7 and the hydrophilic PTFE porous membranes of Comparative Examples 1 to 9 are all obtained by impregnating a PTFE porous substrate (PTFE base membrane) with PVA and then cross-linking PVA. Any one of the methods was selected and produced. The materials and methods selected for each example are shown in Table 1.
【0036】(1)PTFE基膜、及び該基膜のベルト
加熱 PTFE基膜として、住友電工(株)製ポアフロンシー
トUP−010−40RS(未燒結品)、UP−020
−80(未燒結品)、及びWP−020−40(燒結
品)の3種類のシートを用い、各シートをステンレスベ
ルトに、面圧10kg/cm2で圧着した後、ベルトを
340℃、1分間の条件で加熱した。ただし、比較例7
では、このベルト加熱処理は行わなかった。ベルト加熱
処理した各シートの気孔率を測定したところ、前記順に
75%、70%、及び60%であった。式1で定義され
るB値は、PTFE基膜の段階では、いずれも0.98
以上であった。ベルト加熱処理した各シートの式5の左
項の値は、順に−1.7%、−0.6%、及び1.3%
であり、式6の左項の値は、いずれも1.5%以下であ
った。ただし、比較例7のベルト加熱処理を行っていな
いものでは、式5の左項の値は4%で、式6の左項の値
は5%であった。(1) PTFE base film and belt of the base film
As a heating PTFE base film, Sumitomo Electric Co., Ltd. Pore Clon sheet UP-010-40RS (unsintered product), UP-020
Three types of sheets, -80 (unsintered product) and WP-020-40 (sintered product) were used, and each sheet was pressure-bonded to a stainless belt at a surface pressure of 10 kg / cm 2 , and then the belt was placed at 340 ° C. for 1 hour. It heated for the conditions of 1 minute. However, Comparative Example 7
Then, this belt heating treatment was not performed. When the porosity of each sheet subjected to the belt heat treatment was measured, it was 75%, 70%, and 60% in the stated order. The B value defined by the formula 1 is 0.98 at the stage of the PTFE base membrane.
That was all. The value of the left term of the formula 5 of each sheet subjected to the belt heat treatment is -1.7%, -0.6%, and 1.3% in order.
And the values of the left-hand side of Equation 6 were all 1.5% or less. However, in Comparative Example 7 in which the belt heat treatment was not performed, the value of the left term of Expression 5 was 4%, and the value of the left term of Expression 6 was 5%.
【0037】(2)PTFE基膜へのPVAの含浸 各シートは、IPAに30分間浸漬した後に、それぞれ
濃度が0.3重量%、0.4重量%、0.9重量%、及
び1.2重量%のいずれかの濃度のPVA水溶液に、1
時間浸漬した。次いで、液を変えて再び1回目と同じ濃
度のPVA水溶液に15時間浸漬した。このあと、比較
例9を除いて、純水に1分間浸漬した後に、下記の方法
で架橋を行った。(2) Impregnation of PVA into the PTFE base film Each sheet had a concentration of 0.3% by weight, 0.4% by weight, 0.9% by weight, and 1. after being immersed in IPA for 30 minutes. 1% to any concentration of PVA aqueous solution of 2% by weight
Soak for hours. Next, the liquid was changed, and it was again immersed in the PVA aqueous solution having the same concentration as the first time for 15 hours. Then, except for Comparative Example 9, after immersing in pure water for 1 minute, crosslinking was carried out by the following method.
【0038】(3)PVAの架橋 PVAの架橋方法としては、グルタルアルデヒド架橋
(GA)、テレフタルアルデヒド架橋(TPA)、及び
電子線架橋(EB)の3種類のうち、各例でいずれか1
種類を行った。 グルタルアルデヒド架橋では、PVA含浸工程で純水
浸漬後のシートを直ちに0.1規定の塩酸を含む2.5
重量%グルタルアルデヒド水溶液に浸漬し、常温で1時
間反応させた後、多量の純水中で15時間撹拌洗浄し
た。 テレフタルアルデヒド架橋では、PVA含浸工程で純
水浸漬後のシートを直ちに5重量%テレフタルアルデヒ
ドのテトラヒドロフラン溶液に浸漬し、15分間の後、
この液から0.2規定塩酸中にシートを移し換えて室温
で30分間反応させた。その後、多量の純水中で15時
間撹拌洗浄した。 電子線架橋は、PVA含浸工程で純水浸漬後のシート
を20μmのポリエチレンシート2枚の間に気泡を含ま
ないように挟んで、ポリエチレンシートとPTFEシー
トの間の純水をできるだけ排除したものに、片面3Mr
adの電子線照射を両面に行い、合計6Mradの電子
線照射を行った。次いで、ポリエチレンシートを除去
し、多量の純水中で15時間撹拌洗浄した。(3) Cross-linking of PVA As a cross-linking method of PVA, one of three types of glutaraldehyde cross-linking (GA), terephthalaldehyde cross-linking (TPA), and electron beam cross-linking (EB) is used in each example.
Made a kind. In the glutaraldehyde cross-linking, the sheet after soaking in pure water in the PVA impregnation step immediately contains 2.5N of 0.1N hydrochloric acid.
It was immersed in a wt% glutaraldehyde aqueous solution, reacted at room temperature for 1 hour, and then washed with stirring in a large amount of pure water for 15 hours. In the terephthalaldehyde cross-linking, the sheet after being immersed in pure water in the PVA impregnation step is immediately immersed in a tetrahydrofuran solution of 5% by weight terephthalaldehyde, and after 15 minutes,
The sheet was transferred from this solution into 0.2 N hydrochloric acid and reacted at room temperature for 30 minutes. Then, it was washed with stirring in a large amount of pure water for 15 hours. Electron beam cross-linking should be carried out by dipping pure water in the PVA impregnation step between two 20 μm polyethylene sheets so as not to contain air bubbles, and removing pure water between the polyethylene sheet and the PTFE sheet as much as possible. , One side 3Mr
Electron irradiation of ad was performed on both sides, and a total of 6 Mrad of electron irradiation was performed. Then, the polyethylene sheet was removed, and washed with stirring in a large amount of pure water for 15 hours.
【0039】(4)サンプルの準備 各親水化シートは、枠に固定して面積変化を束縛した状
態で、自然乾燥を6時間行った後、真空乾燥を6時間行
い、重量を測定し、元のPTFE重量との差から各PT
FE基膜に対するPVAの固定重量を求めた。結果を一
括して表1に示す。(4) Preparation of Sample Each hydrophilic sheet was naturally dried for 6 hours and then vacuum dried for 6 hours while being fixed to a frame and restrained in area change, and then weighed. From the difference in PTFE weight of each PT
The fixed weight of PVA on the FE base membrane was determined. The results are collectively shown in Table 1.
【0040】[0040]
【表1】 [Table 1]
【0041】(脚注) (*1)架橋方法 GA:グルタルアルデヒド架橋 TPA:テレフタルアルデヒド架橋 EB:電子線照射架橋 (*2)PVA量:PTFE多孔質膜重量に対するPV
Aの固定重量の割合である。 (*3)式1のB値 B値は、下記式1により定義される値である。 B=A1/A0 (1) A0:60%IPA水溶液への浸漬乾燥処理前のA値 A1:60%IPA水溶液への浸漬乾燥処理後のA値 A=水の透過流量/IPAの透過流量(差圧0.42k
g/cm2で測定) (*4)式2の範囲 式2の範囲とは、D値が下記式2で定義される範囲内で
あるか否かを示すものである。 C/5−11.5≦D≦C/5−9.5 (2) C:被塗布体であるPTFE多孔質膜の気孔率(%) D:(親水性材料の塗布重量/PTFE多孔質体重量)
×100(Footnote) (* 1) Cross-linking method GA: Glutaraldehyde cross-linking TPA: Terephthalaldehyde cross-linking EB: Electron beam irradiation cross-linking (* 2) PVA amount: PV per weight of PTFE porous membrane
It is the ratio of the fixed weight of A. (* 3) B value of Expression 1 The B value is a value defined by the following Expression 1. B = A 1 / A 0 (1) A 0 : A value before immersion drying treatment in 60% IPA aqueous solution A 1 : A value after immersion drying treatment in 60% IPA aqueous solution A = water permeation flow rate / IPA Permeation flow rate (differential pressure 0.42k
(measured in g / cm 2 ) (* 4) Range of Formula 2 The range of Formula 2 indicates whether or not the D value is within the range defined by Formula 2 below. C / 5-11.5 ≦ D ≦ C / 5-9.5 (2) C: Porosity (%) of the PTFE porous membrane that is the coated object D: (Coating weight of hydrophilic material / PTFE porous) Body weight)
× 100
【0042】(5)初期流量の評価 各実施例及び比較例の各親水化シートの水透過流量を測
定した。差圧0.42kg/cm2、常温の条件下で
は、PTFE基膜がUP−010−40RSのもので毎
分4.7〜5.0ml/cm2、UP−020−80の
もので毎分7.8〜8.2ml/cm2、そしてWP−
020−80のもので毎分5.1〜5.3ml/cm2
であり、実施例1〜7と比較例1〜3、7及び8の各親
水化シートの間に有意な差はなかった。比較例4、5、
6及び9のものは、1.5〜3.0ml/cm2と水透
過流量が特異的に低かった。走査型電子顕微鏡による観
察の結果、これらの親水化シートには、全面にPVA塊
と見られる孔の目詰まり部分が存在していることがわか
った。この目詰まり部分は、特に比較例9のものに多く
見られた。(5) Evaluation of initial flow rate The water permeation flow rate of each hydrophilized sheet of each Example and Comparative Example was measured. Under the conditions of a differential pressure of 0.42 kg / cm 2 and room temperature, the PTFE base membrane is UP-010-40RS with a rate of 4.7 to 5.0 ml / cm 2 , and the UP-020-80 is with a rate of 0.4 minute. 7.8-8.2 ml / cm 2 , and WP-
020-80, 5.1-5.3 ml / cm 2 per minute
There was no significant difference between the hydrophilized sheets of Examples 1 to 7 and Comparative Examples 1 to 3, 7 and 8. Comparative Examples 4, 5,
The water permeation flow rates of 6 and 9 were specifically low at 1.5 to 3.0 ml / cm 2 . As a result of observation with a scanning electron microscope, it was found that these hydrophilic sheets had a clogging portion of pores, which were considered as PVA lumps, on the entire surface. This clogged portion was especially seen in Comparative Example 9.
【0043】(6)流量保持性の評価 十分に高い初期流量を示した実施例1〜7と比較例1〜
3、7及び8の各親水化シートについて、流量低下の加
速評価として、イソプロピルアルコールと水の6:4混
合溶液(60%IPA水溶液)に浸漬後、非拘束で乾燥
させ、IPA及び水の透過流量を差圧0.42kg/c
m2で測定する操作を1サイクルとしたサイクル試験を
行った。その結果、比較例1〜3、7及び8の親水化シ
ートは、20サイクル後の水透過流量がいずれも、初期
値の50%以下に低下しており、特に比較例7及び8の
親水化シートは、水に全く濡れず、水透過流量がほぼ0
になった。これに対して、実施例1〜7の親水化シート
は、いずれも20サイクル後の水透過流量が初期値の8
0%以上を保持しており、水透過流量の低下が殆ど起こ
らないことがわかった。また、実施例1〜7の親水化シ
ートのIPA透過流量は、いずれの場合も20サイクル
後に初期値の80%以上を保持していた。同様に、各サ
イクル前後の膜の湿潤表面積と膜厚及び乾燥表面積と膜
厚を測定し、式3及び4の左項の値を求めたところ、比
較例7の親水化シートは、それぞれ17%と10%であ
ったが、他はいずれも式3及び4の範囲内であった。(6) Evaluation of flow rate retention Examples 1 to 7 and comparative examples 1 to 10 showing sufficiently high initial flow rates
For each of the hydrophilized sheets of Nos. 3, 7 and 8, as an accelerated evaluation of the reduction in the flow rate, the hydrophilized sheets were immersed in a 6: 4 mixed solution of isopropyl alcohol and water (60% IPA aqueous solution), and then dried without binding to permeate IPA and water. Flow rate differential pressure 0.42kg / c
A cycle test was conducted with the operation of measuring at m 2 as one cycle. As a result, in the hydrophilized sheets of Comparative Examples 1 to 3, 7 and 8, the water permeation flow rates after 20 cycles were all reduced to 50% or less of the initial value, and especially the hydrophilized sheets of Comparative Examples 7 and 8 were made. The sheet does not get wet with water at all, and the water permeation flow rate is almost zero.
Became. On the other hand, in all of the hydrophilic sheets of Examples 1 to 7, the water permeation flow rate after 20 cycles was 8 which is the initial value.
It was found that the water permeation flow rate was maintained at 0% or more, and the decrease in water permeation flow rate hardly occurred. The IPA permeation flow rate of the hydrophilic sheets of Examples 1 to 7 was maintained at 80% or more of the initial value after 20 cycles in all cases. Similarly, the wet surface area and film thickness and the dry surface area and film thickness of the film before and after each cycle were measured, and the values in the left-hand side of formulas 3 and 4 were determined. Was 10%, and the others were within the ranges of Equations 3 and 4.
【0044】(7)耐薬品性の評価 十分に高い初期流量を示した実施例1〜7と比較例1〜
3、7及び8の各親水化シートについて、30%塩酸、
30%硫酸、及び10%水酸化ナトリウムに、それぞれ
60℃で1ヶ月間浸漬し、その前後での水透過流量を比
較した。その結果、比較例1〜3、7及び8の親水化シ
ートでは、いずれも浸漬後の水透過流量が初期流量の5
0%以下になっていたのに対し、実施例1〜7の親水化
シートでは、初期流量の90%以上を維持していた。特
に10%水酸化ナトリウム処理の場合、比較例の親水化
シートがいずれも水に濡れなくなり、水透過流量が0に
なったのに対して、実施例1〜7の親水化シートでは、
水透過流量の低下が殆ど起こらなかった。(7) Evaluation of chemical resistance Examples 1 to 7 showing comparatively high initial flow rates and Comparative Examples 1 to 1
For each of the hydrophilic sheets 3, 7, and 8, 30% hydrochloric acid,
Each was immersed in 30% sulfuric acid and 10% sodium hydroxide at 60 ° C. for 1 month, and the water permeation flow rates before and after the immersion were compared. As a result, in the hydrophilic sheets of Comparative Examples 1 to 3, 7 and 8, the water permeation flow rate after immersion was 5 which was the initial flow rate.
While it was 0% or less, the hydrophilic sheets of Examples 1 to 7 maintained 90% or more of the initial flow rate. In particular, in the case of the 10% sodium hydroxide treatment, none of the hydrophilization sheets of Comparative Examples became wet with water and the water permeation flow rate became 0, whereas in the hydrophilization sheets of Examples 1 to 7,
Almost no decrease in the water permeation flow rate occurred.
【0045】[0045]
【発明の効果】本発明の親水性PTFE多孔質膜は、安
定した親水性材料層を有し、流量維持性、耐薬品性に非
常に優れたものであり、各種分離膜用途に好適に用いる
ことができる。特に従来の親水性PTFE多孔質膜の弱
点であった有機溶媒と水との混合溶媒や、酸・アルカリ
などの薬品を溶媒とする分離用途に適している。これら
の薬品類は、分離膜システムの休止に伴う洗浄などにも
利用されることから、本発明の親水性PTFE多孔質膜
は、単なる水系の分離でも高寿命な分離膜として利用す
ることが可能となる。EFFECT OF THE INVENTION The hydrophilic PTFE porous membrane of the present invention has a stable hydrophilic material layer, is extremely excellent in flow rate maintenance and chemical resistance, and is suitably used for various separation membrane applications. be able to. In particular, it is suitable for a separation solvent using a mixed solvent of an organic solvent and water, which is a weak point of the conventional hydrophilic PTFE porous membrane, or a chemical such as acid or alkali as a solvent. Since these chemicals are also used for cleaning when the separation membrane system is stopped, the hydrophilic PTFE porous membrane of the present invention can be used as a long-life separation membrane even in simple water-based separation. Becomes
【図1】従来技術によって得られたPVA塗布PTFE
多孔質膜を、60%IPA水溶液に浸漬し、非拘束で乾
燥する操作(浸漬−乾燥サイクル)を繰り返した場合に
おけるPTFE多孔質膜の表面積と膜厚の変化、及び差
圧0.42kg/cm2で測定した水透過流量の変化を
表わすグラフである。FIG. 1 PVA coated PTFE obtained by prior art
A change in surface area and film thickness of the PTFE porous membrane and a differential pressure 0.42 kg / cm when the operation of immersing the porous membrane in a 60% IPA aqueous solution and drying without restraint (immersion-drying cycle) is repeated. 3 is a graph showing the change in water permeation flow rate measured in 2 .
【図2】本発明品を60%IPA水溶液に浸漬し、非拘
束で乾燥する操作(浸漬−乾燥サイクル)を繰り返した
場合におけるPTFE多孔質膜の表面積と膜厚の変化、
及び差圧0.42kg/cm2で測定した水透過流量の
変化を表わすグラフである。FIG. 2 shows a change in surface area and film thickness of a PTFE porous membrane when an operation of immersing the product of the present invention in a 60% IPA aqueous solution and drying without restraint (immersion-drying cycle),
3 is a graph showing a change in water permeation flow rate measured at a differential pressure of 0.42 kg / cm 2 .
【図3】PTFE多孔質膜の気孔率と最適な親水性材料
の塗布量の関係を表すグラフである。FIG. 3 is a graph showing the relationship between the porosity of the PTFE porous film and the optimum coating amount of the hydrophilic material.
───────────────────────────────────────────────────── フロントページの続き (51)Int.Cl.6 識別記号 庁内整理番号 FI 技術表示箇所 C08J 7/04 CEW C08J 7/04 CEWT // C08L 27:18 29:04 ─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. 6 Identification code Internal reference number FI Technical display location C08J 7/04 CEW C08J 7/04 CEWT // C08L 27:18 29:04
Claims (8)
質構造の表面に架橋した親水性材料の塗布層が形成され
た親水性四弗化エチレン樹脂多孔質膜であって、それぞ
れ差圧0.42kg/cm2で測定したイソプロピルア
ルコール透過流量(ml/cm2/min)に対する水
透過流量(ml/cm2/min)の比をA値とした場
合、下記の関係式1を満足するものであることを特徴と
する親水性四弗化エチレン樹脂多孔質膜。 A1/A0≧0.90 (1) A1:親水性四弗化エチレン樹脂多孔質膜をイソプロピ
ルアルコールと水との6:4(容量比)の混合溶液に浸
漬し、乾燥する処理を行った後のA値 A0:前記浸漬乾燥処理前の親水性四弗化エチレン樹脂
多孔質膜のA値1. A hydrophilic tetrafluoroethylene resin porous membrane having a coating layer of a crosslinked hydrophilic material formed on the surface of a fine porous structure of the tetrafluoroethylene resin porous membrane, each of which has a differential pressure. When the ratio of the water permeation flow rate (ml / cm 2 / min) to the isopropyl alcohol permeation flow rate (ml / cm 2 / min) measured at 0.42 kg / cm 2 is A value, the following relational expression 1 is satisfied. What is claimed is: 1. A hydrophilic tetrafluoroethylene resin porous membrane, characterized in that A 1 / A 0 ≧ 0.90 (1) A 1 : A treatment in which a hydrophilic tetrafluoroethylene resin porous membrane is immersed in a mixed solution of isopropyl alcohol and water at a volume ratio of 6: 4 and dried. A value after performing A 0 : A value of the hydrophilic tetrafluoroethylene resin porous film before the immersion drying treatment
60%以上であり、かつ、四弗化エチレン樹脂多孔質膜
に対する親水性材料の塗布量が下記の関係式2を満足す
るものである請求項1記載の親水性四弗化エチレン樹脂
多孔質膜。 (C/5)−11.5≦D≦(C/5)−9.5 (2) C:四弗化エチレン樹脂多孔質膜の気孔率(%) D:(親水性材料の塗布重量/四弗化エチレン樹脂多孔
質膜重量)×1002. A porous tetrafluoroethylene resin membrane having a porosity of 60% or more, and a coating amount of a hydrophilic material on the porous tetrafluoroethylene resin membrane satisfies the following relational expression 2. The hydrophilic tetrafluoroethylene resin porous membrane according to claim 1, which is (C / 5) -11.5 ≦ D ≦ (C / 5) -9.5 (2) C: Porosity (%) of porous tetrafluoroethylene resin membrane D: (Coating weight of hydrophilic material / Polytetrafluoroethylene resin porous membrane weight) x 100
(容量比)の混合溶液に湿潤した状態で測定した親水性
四弗化エチレン樹脂多孔質膜の表面積(S0)及び膜厚
(d0)と、該混合溶液を含浸後、乾燥させてから測定
した該膜の表面積(S1)及び膜厚(d1)との間に、そ
れぞれ以下の関係式3及び4が成立する請求項1または
2記載の親水性四弗化エチレン樹脂多孔質膜。 |〔(S1−S0)/S0〕×100|≦2% (3) |〔(d1−d0)/d0〕×100|≦2% (4)3. 6: 4 of isopropyl alcohol and water
The surface area (S 0 ) and film thickness (d 0 ) of the hydrophilic tetrafluoroethylene resin porous membrane measured in a wet state with the mixed solution (volume ratio), and after impregnation with the mixed solution and drying. The hydrophilic tetrafluoroethylene resin porous film according to claim 1 or 2, wherein the following relational expressions 3 and 4 are established between the measured surface area (S 1 ) and film thickness (d 1 ) of the film. . | [(S 1 -S 0 ) / S 0 ] × 100 | ≦ 2% (3) | [(d 1 −d 0 ) / d 0 ] × 100 | ≦ 2% (4)
る請求項1ないし3のいずれか1項に記載の親水性四弗
化エチレン樹脂多孔質膜。4. The hydrophilic tetrafluoroethylene resin porous membrane according to any one of claims 1 to 3, wherein the hydrophilic material is polyvinyl alcohol.
質構造の表面に架橋した親水性材料の塗布層が形成され
た親水性四弗化エチレン樹脂多孔質膜の製造方法におい
て、(1)四弗化エチレン樹脂多孔質膜の微細多孔質構
造内にアルコールを含浸させる工程、(2)0.4〜
1.0重量%の濃度の親水性材料の水溶液を含浸させて
前記アルコールを親水性材料で置換する工程、(3)水
に浸漬する工程、及び(4)含浸した親水性材料を架橋
する工程を含むことを特徴とする親水性四弗化エチレン
樹脂多孔質膜の製造方法。5. A method for producing a hydrophilic tetrafluoroethylene resin porous membrane, wherein a coating layer of a crosslinked hydrophilic material is formed on the surface of a microporous structure of the tetrafluoroethylene resin porous membrane, comprising: (1) ) A step of impregnating alcohol into the fine porous structure of the tetrafluoroethylene resin porous membrane, (2) 0.4-
A step of impregnating an aqueous solution of a hydrophilic material with a concentration of 1.0% by weight to replace the alcohol with the hydrophilic material; (3) a step of immersing in water; and (4) a step of crosslinking the impregnated hydrophilic material. A method for producing a hydrophilic tetrafluoroethylene resin porous membrane, comprising:
ソプロピルアルコールと水との6:4(容量比)の混合
溶液に湿潤した状態で測定した表面積(SA)及び膜厚
(dA)と、該混合溶液を含浸後、乾燥させてから測定
した該膜の表面積(SB)及び膜厚(dB)との間に、そ
れぞれ以下の関係式5及び6が成立するものを使用する
請求項5記載の親水性四弗化エチレン樹脂多孔質膜の製
造方法。 |〔(SB−SA)/SA〕×100|≦2% (5) |〔(dB−dA)/dA〕×100|≦2% (6)6. A surface area (S A ) and a film thickness (d A ) measured in a wet state with a mixed solution of isopropyl alcohol and water at a volume ratio of 6: 4 as a porous tetrafluoroethylene resin film. And the surface area (S B ) and the film thickness (d B ) of the film, which are measured after impregnation of the mixed solution and drying, are used so that the following relational expressions 5 and 6 hold, respectively. The method for producing the hydrophilic tetrafluoroethylene resin porous membrane according to claim 5. │ [(S B -S A ) / S A ) × 100 | ≦ 2% (5) │ [(d B −d A ) / d A ] × 100 | ≦ 2% (6)
に圧着した状態で融点以上に加熱処理したものである請
求項6記載の親水性四弗化エチレン樹脂多孔質膜の製造
方法。7. The method for producing a hydrophilic tetrafluoroethylene resin porous membrane according to claim 6, wherein the porous tetrafluoroethylene resin membrane is heat-treated at a temperature equal to or higher than the melting point in a state of being pressed onto a metal plate.
を用い、前記架橋工程(4)において、グルタルアルデ
ヒド及びテレフタルアルデヒドからなる群より選ばれる
少なくとも1種の化合物の存在下に化学架橋する請求項
5ないし7のいずれか1項に記載の製造方法。8. A polyvinyl alcohol is used as the hydrophilic material, and in the crosslinking step (4), the chemical crosslinking is carried out in the presence of at least one compound selected from the group consisting of glutaraldehyde and terephthalaldehyde. The manufacturing method according to any one of 1.
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-
1995
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