本発明は、ポリテトラフルオロエチレン（以下、「ＰＴＦＥ」という。）多孔質膜の製造方法、ＰＴＦＥ多孔質膜が巻き回されることにより構成される巻回体、ならびに、ＰＴＦＥ多孔質膜を用いたフィルタ用濾材およびその製造方法に関する。 The present invention uses a method for producing a polytetrafluoroethylene (hereinafter referred to as “PTFE”) porous membrane, a wound body formed by winding a PTFE porous membrane, and a PTFE porous membrane. The present invention relates to a filter medium and a manufacturing method thereof.
従来、クリーンルーム用エアフィルタや掃除機用フィルタ、焼却用バグフィルタなどには、ＰＴＦＥ多孔質膜を用いた濾材が使用されている。これらのフィルタ用濾材は、表面積を大きく確保する目的で蛇腹状に折り曲げられているのが一般的である。 Conventionally, a filter medium using a PTFE porous membrane has been used for an air filter for a clean room, a filter for a vacuum cleaner, a bag filter for incineration, and the like. These filter media are generally bent in a bellows shape for the purpose of ensuring a large surface area.
フィルタ用濾材は、通常、ガラス繊維や不織布などの通気性支持材にＰＴＦＥ多孔質膜をラミネートして作られる。そして、蛇腹状のフィルタ用濾材を連続的に生産するには、まずテープ状の通気性支持材にテープ状のＰＴＦＥ多孔質膜を接合してテープ状のフィルタ用濾材を作製し、ついでこのフィルタ用濾材を、折り目が所定間隔だけ離間して長手方向について互いに平行に配列されるように、すなわちフィルタ用濾材が幅方向に延びる線を境に表側と裏側に交互に折り返されるように、プリーツ加工していくことが望ましい。 The filter medium is usually made by laminating a porous PTFE membrane on a breathable support material such as glass fiber or nonwoven fabric. In order to continuously produce a bellows-like filter medium, first, a tape-like PTFE porous membrane is joined to a tape-like air-permeable support material to produce a tape-like filter medium. The filter medium is pleated so that the folds are spaced apart by a predetermined distance and arranged in parallel with each other in the longitudinal direction, that is, the filter medium is folded back alternately on the front side and the back side with a line extending in the width direction as a boundary. It is desirable to do.
テープ状のＰＴＦＥ多孔質膜は、例えば特許文献１に示されているような方法で製造される。具体的には、まずＰＴＦＥ微粉末に液状潤滑剤を加えた混合物を所定方向に延びるシート状に成形し、ついでこのシート状成形体から液状潤滑剤を除去した後に当該シート状成形体をまず長手方向に延伸して繊維化する。すなわち、シート状成形体を、長手方向にフィブリルが伸びかつ幅方向にノードが伸びた構造を有するＰＴＦＥ多孔質膜とする。その後、ＰＴＦＥ多孔質膜をさらに幅方向に延伸する。 The tape-like porous PTFE membrane is manufactured by a method as disclosed in Patent Document 1, for example. Specifically, a mixture obtained by adding a liquid lubricant to PTFE fine powder is first molded into a sheet shape extending in a predetermined direction, and then the liquid lubricant is removed from the sheet-shaped molded body, and then the sheet-shaped molded body is first elongated. Stretch in the direction and fiberize. That is, the sheet-like molded body is a PTFE porous membrane having a structure in which fibrils extend in the longitudinal direction and nodes extend in the width direction. Thereafter, the PTFE porous membrane is further stretched in the width direction.
また、特許文献２には、シート状成形体から液状潤滑剤を除去する前に、シート状成形体を液状潤滑剤を含んだまま幅方向に予備延伸することが記載されている。ただし、この予備延伸は高い通気性を持つ通気膜を得るために行われるものであり、特許文献２に記載の方法においても、予備延伸後には特許文献１と同様にシート状成形体を乾燥させた後にまず長手方向の延伸が行われるようになっている。
ところが、前記のような方法で製造されたＰＴＦＥ多孔質膜は、フィブリルが当該ＰＴＦＥ多孔質膜の幅方向にのみ並んでいるかフィブリルの並びが当該ＰＴＦＥ多孔質膜の幅方向に支配的であるため、幅方向に伸びることはできるものの長手方向にはあまり伸びることができない。そのため、前記のようにＰＴＦＥ多孔質膜が通気性支持材に接合された後に通気性支持材と共に幅方向に延びる線を境に折り返されると、通気性支持材の折れ点を支点としてＰＴＦＥ多孔質膜が長手方向に引き伸ばされることによりＰＴＦＥ多孔質膜に亀裂が生じることがあった。 However, in the PTFE porous membrane manufactured by the method as described above, the fibrils are arranged only in the width direction of the PTFE porous membrane or the arrangement of fibrils is dominant in the width direction of the PTFE porous membrane. Although it can extend in the width direction, it cannot extend so much in the longitudinal direction. Therefore, when the PTFE porous membrane is joined to the air-permeable support material as described above and then folded back along the line extending in the width direction together with the air-permeable support material, When the membrane is stretched in the longitudinal direction, cracks may occur in the PTFE porous membrane.
本発明は、このような事情に鑑み、長手方向に伸びやすいＰＴＦＥ多孔質膜を製造することができる製造方法およびこの製造方法により製造されるＰＴＦＥ多孔質膜、このＰＴＦＥ多孔質膜が巻き回されることにより構成される巻回体、ならびに、ＰＴＦＥ多孔質膜を用いたフィルタ用濾材およびその製造方法を提供することを目的とする。 In view of such circumstances, the present invention provides a production method capable of producing a PTFE porous membrane that is easily stretched in the longitudinal direction, a PTFE porous membrane produced by the production method, and the PTFE porous membrane being wound. It is an object of the present invention to provide a wound body constituted by the above, a filter medium for a filter using a PTFE porous membrane, and a method for producing the same.
本発明の発明者は、前記の目的を達成するためには、シート状成形体を最初に延伸して繊維化すればよいのではないかと考えた。しかし、従来の方法により得られるシート状成形体では、液体潤滑剤を除去した後に、先に幅方向に延伸しようとすると、その方向に均一に繊維化せず、多孔質膜の強度にバラツキが発生し、繊維化の程度が低い部分をきっかけに破断が生じることがある。そこで、発明者らは、液状潤滑剤を含んだ状態でシート状成形体をいったん幅方向に延伸することで、幅方向にも均一に繊維化させ、強度を向上させることを思いついた。 The inventor of the present invention thought that in order to achieve the above-mentioned object, the sheet-like molded body may be first drawn into fibers. However, in the sheet-like molded body obtained by the conventional method, if the liquid lubricant is removed and then the stretching is first performed in the width direction, the fiber is not uniformly formed in that direction, and the strength of the porous film varies. It may occur and break when triggered by a portion with a low degree of fiberization. Thus, the inventors have come up with the idea that a sheet-like molded body is stretched in the width direction once in a state containing a liquid lubricant, so that the fibers are uniformly made into fibers in the width direction and the strength is improved.
本発明は、上記のような観点からなされたものであり、ＰＴＦＥ微粉末に液状潤滑剤を加えた混合物を成形して所定方向に延びるシート状成形体を得る工程と、前記シート状成形体を前記液状潤滑剤を含んだ状態で前記所定方向と直交する幅方向に延伸した後に、当該シート状成形体から液状潤滑剤を除去する工程と、前記液状潤滑剤が除去されたシート状成形体を前記幅方向に延伸して、当該シート状成形体を前記幅方向にフィブリルが伸びかつ前記所定方向にノードが伸びた構造を有するＰＴＦＥ多孔質膜とする工程と、を含むＰＴＦＥ多孔質膜の製造方法を提供する。 The present invention has been made from the above viewpoint, and a step of obtaining a sheet-like molded body extending in a predetermined direction by molding a mixture obtained by adding a liquid lubricant to PTFE fine powder; A step of removing the liquid lubricant from the sheet-like molded article after stretching in the width direction perpendicular to the predetermined direction in a state containing the liquid lubricant, and a sheet-like molded article from which the liquid lubricant has been removed. Stretching the sheet in the width direction, and forming the sheet-like molded body into a PTFE porous film having a structure in which fibrils extend in the width direction and nodes extend in the predetermined direction. Provide a method.
また、本発明は、上記の製造方法により、所定方向にノードが伸びかつ当該所定方向と直交する幅方向にフィブリルが伸びた構造を有するＰＴＦＥ多孔質膜を製造し、このＰＴＦＥ多孔質膜を通気性支持材に接合してフィルタ用濾材を得るフィルタ用濾材の製造方法を提供する。 Further, according to the present invention, a PTFE porous membrane having a structure in which nodes extend in a predetermined direction and fibrils extend in a width direction orthogonal to the predetermined direction is manufactured by the above-described manufacturing method, and the PTFE porous membrane is vented. Provided is a method for producing a filter medium for filtering to obtain a filter medium by bonding to a conductive support material.
さらに、本発明は、ＰＴＦＥ多孔質膜が巻き回されて構成された巻回体であって、前記ＰＴＦＥ多孔質膜は、前記巻き回し方向にノードが伸びかつ前記巻き回し方向と直交する幅方向にフィブリルが伸びた構造を有するものである巻回体を提供する。 Furthermore, the present invention is a wound body constituted by winding a PTFE porous membrane, wherein the PTFE porous membrane has a node extending in the winding direction and a width direction perpendicular to the winding direction. And a wound body having a structure in which fibrils are elongated.
さらには、本発明は、通気性支持材にＰＴＦＥ多孔質膜が接合されたフィルタ用濾材であって、蛇腹状に折り曲げられていて所定方向に並ぶ折り目を有しており、前記ＰＴＦＥ多孔質膜は、前記所定方向にノードが伸びかつ前記所定方向と直交する幅方向にフィブリルが伸びた構造を有するものであるフィルタ用濾材を提供する。 Furthermore, the present invention is a filter medium for a filter in which a PTFE porous membrane is bonded to a gas-permeable support material, and has a fold lined in a bellows shape and arranged in a predetermined direction, and the PTFE porous membrane Provides a filter medium having a structure in which nodes extend in the predetermined direction and fibrils extend in a width direction orthogonal to the predetermined direction.
本発明に係る製造方法によれば、シート状成形体を液状潤滑剤の除去後に幅方向に延伸してＰＴＦＥ多孔質膜とすることにより、フィブリルがＰＴＦＥ多孔質膜の長手方向に並ぶかフィブリルの並びがＰＴＦＥ多孔質膜の長手方向に支配的となるために、長手方向に伸びやすいＰＴＦＥ多孔質膜を得ることができる。そして、このＰＴＦＥ多孔質膜を用いれば、通気性支持材と共に幅方向に延びる線を境に折り返す際に当該ＰＴＦＥ多孔質膜が良好に長手方向に引き伸ばされるようになるため、不具合の発生を抑えながら蛇腹状のフィルタ用濾材を連続的に生産することができるようになる。 According to the production method of the present invention, the sheet-like molded body is stretched in the width direction after removing the liquid lubricant to form a PTFE porous film, whereby the fibrils are aligned in the longitudinal direction of the PTFE porous film or the fibrils are formed. Since the alignment is dominant in the longitudinal direction of the PTFE porous membrane, a PTFE porous membrane that is easily stretched in the longitudinal direction can be obtained. If this PTFE porous membrane is used, when the PTFE porous membrane is stretched in the longitudinal direction well when folded back along the line extending in the width direction together with the breathable support material, the occurrence of problems is suppressed. However, the bellows-like filter medium can be continuously produced.
以下、本発明のＰＴＦＥ多孔質膜の製造方法について説明する。この製造方法は、図２に示すような通気性支持材４に接合されてフィルタ用濾材２を構成するＰＴＦＥ多孔質膜３を得るためのものであり、第１工程から第３工程までの３つの工程からなる。なお、フィルタ用濾材２は、蛇腹状に折り曲げられているとともに、図１に示すような枠体５などの構造体に保持されてフィルタ１を構成する。 Hereinafter, the manufacturing method of the PTFE porous membrane of this invention is demonstrated. This manufacturing method is for obtaining a PTFE porous membrane 3 which is bonded to a gas-permeable support material 4 as shown in FIG. 2 and constitutes the filter medium 2 for the filter. It consists of two steps. The filter medium 2 is bent in a bellows shape and is held by a structure such as a frame 5 as shown in FIG.
第１工程では、ＰＴＦＥ微粉末に液状潤滑剤を加えた混合物を押出法および圧延法の少なくとも１つの方法により未焼成状態で所定方向に延びるシート状に成形してシート状成形体を得る。 In the first step, a mixture obtained by adding a liquid lubricant to PTFE fine powder is molded into a sheet extending in a predetermined direction in an unfired state by at least one of an extrusion method and a rolling method to obtain a sheet-shaped molded body.
ＰＴＦＥ微粉末は、特に制限されるものではなく、種々の市販のものを使用できる。例えば、ポリフロンＦ−１０４（ダイキン工業社製）、フルオンＣＤ−１２３（旭硝子社製）、テフロン６Ｊ（三井・デュポンフロロケミカル社製）などが挙げられる。なお、ＰＴＦＥ微粉末としては、前記のようなＰＴＦＥホモポリマーで構成された粉末に、例えばテトラフルオロエチレン−パーフルオロアルコキシビニルエーテルコポリマー（ＰＦＡ）、フッ化エチレンポリプロピレンコポリマー（ＦＥＰ）、エチレンテトラフルオロエチレンコポリマー（ＥＴＦＥ）などの改質ＰＴＦＥポリマーで構成された粉末を混合させたものであってもよい。また、ＰＴＦＥ微粉末は、例えばＴｉＯ2、ＳｉＯ2、カーボンブラックなどのフィラー粒子を含むものであってもよい。The PTFE fine powder is not particularly limited, and various commercially available products can be used. For example, polyflon F-104 (manufactured by Daikin Industries), full-on CD-123 (manufactured by Asahi Glass Co., Ltd.), Teflon 6J (manufactured by Mitsui / DuPont Fluorochemical Co., Ltd.) and the like can be mentioned. The PTFE fine powder includes, for example, tetrafluoroethylene-perfluoroalkoxy vinyl ether copolymer (PFA), fluorinated ethylene polypropylene copolymer (FEP), and ethylene tetrafluoroethylene copolymer. A powder composed of a modified PTFE polymer such as (ETFE) may be mixed. The PTFE fine powder may contain filler particles such as TiO2 , SiO2 , and carbon black.
液状潤滑剤は、ＰＴＦＥ微粉末を濡らすことができ、蒸発や抽出などの方法によって除去できるものであれば特に制限されるものではない。例えば、炭化水素類の流動パラフィン、ナフサ、トルエン、キシレンが挙げられ、他にもアルコール類、ケトン類、エステル類、フッ素系溶剤が挙げられる。また、これらの２種類以上の混合物を使用してもよい。潤滑剤の添加量は、シート状成形体の成形方法によって異なるが、通常、ＰＴＦＥ微粉末１００重量部に対して約５〜５０重量部である。 The liquid lubricant is not particularly limited as long as it can wet the PTFE fine powder and can be removed by a method such as evaporation or extraction. Examples include hydrocarbons such as liquid paraffin, naphtha, toluene, and xylene, and alcohols, ketones, esters, and fluorinated solvents. Moreover, you may use these 2 or more types of mixtures. The addition amount of the lubricant varies depending on the molding method of the sheet-like molded body, but is usually about 5 to 50 parts by weight with respect to 100 parts by weight of the PTFE fine powder.
ＰＴＦＥ微粉末に液状潤滑剤を加えた混合物をシート状に成形する方法の一例としては、液状潤滑剤を加えたＰＴＦＥ微粉末をシリンダーで圧縮し、ラム押出機で押し出してシート状に成形した後に、ロール対で適当な厚み（通常、０．０５〜０．５ｍｍ）に圧延する。 As an example of a method for forming a mixture of a PTFE fine powder and a liquid lubricant into a sheet shape, the PTFE fine powder to which a liquid lubricant is added is compressed with a cylinder, extruded with a ram extruder, and then formed into a sheet shape. Then, the roll is rolled to an appropriate thickness (usually 0.05 to 0.5 mm).
第２工程では、まず、第１工程で得られたシート状成形体を、液状潤滑剤を含んだ状態で、すなわち液状潤滑剤が蒸発し難い温度（通常は常温）で、シート状成形体が延びる方向（長手方向）と直交する幅方向に延伸する。ここでの幅方向の延伸倍率は、特に規定されないが、延伸時に裂けずに幅方向の強度を強くする観点から、好ましくは１．５〜２０倍、より好ましくは２〜１０倍である。なお、本工程での延伸を、液状潤滑剤が満たされた浴槽中で行ってもよい。 In the second step, first, the sheet-like molded product obtained in the first step is in a state containing a liquid lubricant, that is, at a temperature at which the liquid lubricant is difficult to evaporate (normally normal temperature). It extends | stretches in the width direction orthogonal to the extending direction (longitudinal direction). The draw ratio in the width direction here is not particularly specified, but is preferably 1.5 to 20 times, more preferably 2 to 10 times from the viewpoint of increasing the strength in the width direction without tearing during stretching. In addition, you may perform extending | stretching at this process in the bathtub filled with the liquid lubricant.
その後、加熱法または抽出法によりシート状成形体から液状潤滑剤を除去してシート状成形体を乾燥させる。 Thereafter, the liquid lubricant is removed from the sheet-shaped molded body by a heating method or an extraction method, and the sheet-shaped molded body is dried.
第３工程では、第２工程で液状潤滑剤が除去されたシート状成形体を幅方向に延伸して、当該シート状成形体を、図３に示すような幅方向にフィブリル３２が伸びかつ長手方向にノード３１が伸びた構造を有するＰＴＦＥ多孔質膜３とする。ここでの延伸倍率は、４〜１００倍が好ましい。４倍より低い倍率では通気性を確保し難く、１００倍よりも高い倍率では延伸時にシート状成形体が避けやすくなるからである。また、延伸時の温度は、通常は４０〜４００℃であるが、１００〜３２７℃が好ましい。１００℃より低い温度では延伸時にシート状成形体が裂けやすく、ＰＴＦＥの融点である３２７℃より高い温度ではＰＴＦＥ多孔質膜の長手方向の伸びが小さくなる。なお、本工程での幅方向への延伸は、複数回に分けて行ってもよい。 In the third step, the sheet-like molded body from which the liquid lubricant has been removed in the second step is stretched in the width direction, and the fibril 32 is elongated in the width direction as shown in FIG. The PTFE porous membrane 3 has a structure in which the nodes 31 extend in the direction. The stretching ratio here is preferably 4 to 100 times. This is because it is difficult to ensure air permeability at a magnification lower than 4 times, and it becomes easy to avoid a sheet-like molded body at the time of stretching at a magnification higher than 100 times. Moreover, the temperature at the time of extending | stretching is 40-400 degreeC normally, However, 100-327 degreeC is preferable. When the temperature is lower than 100 ° C., the sheet-like molded product is easily torn during stretching, and when the temperature is higher than 327 ° C., which is the melting point of PTFE, the elongation in the longitudinal direction of the PTFE porous membrane is reduced. The stretching in the width direction in this step may be performed in a plurality of times.
以上の３つの工程により、所定方向に延びるテープ状のＰＴＦＥ多孔質膜３であってその長手方向にのみフィブリル３２が並ぶＰＴＦＥ多孔質膜３を得ることができるが（図３参照）、このようにして得られたＰＴＦＥ多孔質膜３に対して、さらに長手方向および幅方向の一方もしくは双方への延伸を必要により複数回行ってもよい。長手方向に延伸すると、長手方向にフィブリルが伸びた構造となる。ただし、長手方向に延伸する場合でも、ノードの形状は、長手方向に細長い形状、すなわち長手方向の長さが幅方向の長さよりも長い形状となるように延伸することが好ましい。 By the above three steps, a PTFE porous membrane 3 that is a tape-like PTFE porous membrane 3 extending in a predetermined direction and in which fibrils 32 are arranged only in the longitudinal direction can be obtained (see FIG. 3). The PTFE porous membrane 3 obtained as described above may be further extended several times as required in one or both of the longitudinal direction and the width direction. When stretched in the longitudinal direction, a structure in which fibrils extend in the longitudinal direction is obtained. However, even when extending in the longitudinal direction, the shape of the node is preferably elongated so that the length in the longitudinal direction, that is, the length in the longitudinal direction is longer than the length in the width direction.
なお、ＰＴＦＥ多孔質膜の長手方向の伸びを大きくするには、幅方向の合計延伸倍率を大きくすることによって可能になり、このときの延伸時の温度はＰＴＦＥの融点（３２７℃）より低い温度が好ましい。また、多孔質膜の長手方向の強度を大きくするには、幅方向の延伸後に長手方向に延伸する方法、幅方向の延伸をポリマー融点以上で行う方法、ポリマー融点以下で延伸したシート状成形体を拘束したままポリマー融点以上の高温に加熱する方法がある。 In order to increase the elongation in the longitudinal direction of the PTFE porous membrane, it is possible to increase the total stretching ratio in the width direction, and the temperature during stretching at this time is lower than the melting point (327 ° C.) of PTFE. Is preferred. Further, in order to increase the strength in the longitudinal direction of the porous membrane, a method of stretching in the longitudinal direction after stretching in the width direction, a method of stretching in the width direction at a temperature higher than the polymer melting point, a sheet-like molded body stretched at a temperature lower than the polymer melting point There is a method of heating to a high temperature not lower than the melting point of the polymer while restraining.
最終的に得られる膜の長手方向の伸びが幅方向の延伸倍率によって異なることを後で実施例によって説明する。 The fact that the elongation in the longitudinal direction of the finally obtained film varies depending on the stretching ratio in the width direction will be described later in Examples.
上記のようにして得られた所定方向に延びるテープ状のＰＴＦＥ多孔質膜を、その長手方向に巻き回すことにより巻回体を構成すれば、いったん保管したり別の場所に搬送したりすることができる。 Once the tape-like PTFE porous membrane extending in the predetermined direction obtained as described above is wound in the longitudinal direction to form a wound body, it can be stored once or transported to another place. Can do.
また、上記のようにして得られた所定方向に延びるテープ状のＰＴＦＥ多孔質膜を用いて蛇腹状のフィルタ用濾材を連続的に製造するには、まずＰＴＦＥ多孔質膜をテープ状の通気性支持材に接合してフィルタ用濾材を作製し、ついでこのフィルタ用濾材を折り目が長手方向に互いに離間して並ぶようにプリーツ加工していけばよい。 In order to continuously produce a bellows-like filter medium for a filter using the tape-like PTFE porous membrane extending in a predetermined direction obtained as described above, first, the PTFE porous membrane is made into a tape-like air permeability. A filter medium may be produced by joining to a support material, and then the filter medium may be pleated so that the folds are arranged apart from each other in the longitudinal direction.
なお、製造後の蛇腹状に折り曲げられたフィルタ用濾材は、フィルタを構成する際には、図１に示すように平面的な姿勢で保持されていてもよいが、図示は省略するが、円筒を構成するような姿勢、または折り目が放射状に並ぶ円盤を構成するような姿勢で保持されていてもよい。すなわち、フィルタ用濾材の折り目が並ぶ方向は、直線方向だけでなく、円筒面上の周方向または平面上の周方向となっていてもよい。 Note that the filter medium folded into a bellows shape after manufacture may be held in a planar posture as shown in FIG. 1 when constituting the filter. Or may be held in such a posture as to constitute a disk in which creases are arranged radially. That is, the direction in which the folds of the filter media are arranged may be not only the linear direction but also the circumferential direction on the cylindrical surface or the circumferential direction on the plane.
以下、実施例を挙げて本発明を詳細に説明するが、本発明は、これら実施例に何ら制限されるものではない。 EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated in detail, this invention is not restrict | limited to these Examples at all.
（実施例１）
ＰＴＦＥ微粉末（ポリフロンＦ−１０４、ダイキン工業社製）１００重量部に対して、液状潤滑剤（ｎ−ドデカン、ジャパンエナジー社製）１９重量部を均一に混合し、シリンダーに圧縮した後にラム押出機で押し出して所定方向に延びるシート状成形体を得た。このシート状成形体を液状潤滑剤を含んだ状態で金属製圧延ロール間に通して厚さ０．２ｍｍに圧延し、幅方向に４倍の倍率で延伸した。その後、シート状成形体を１５０℃に加熱することにより液状潤滑剤を除去し、シート状成形体を乾燥させた。このシート状成形体を１５０℃で幅方向に９倍の倍率で延伸してＰＴＦＥ多孔質膜を得た。Example 1
19 parts by weight of a liquid lubricant (n-dodecane, manufactured by Japan Energy Co.) is uniformly mixed with 100 parts by weight of PTFE fine powder (Polyflon F-104, manufactured by Daikin Industries, Ltd.), compressed into a cylinder, and then ram extruded. A sheet-like molded body that was extruded by a machine and extended in a predetermined direction was obtained. The sheet-like molded body was passed through a metal rolling roll in a state containing a liquid lubricant, rolled to a thickness of 0.2 mm, and stretched at a magnification of 4 times in the width direction. Then, the liquid lubricant was removed by heating the sheet-shaped molded body to 150 ° C., and the sheet-shaped molded body was dried. This sheet-like molded body was stretched at a magnification of 9 times in the width direction at 150 ° C. to obtain a PTFE porous membrane.
（実施例２）
実施例２では、乾燥前のシート状成形体の幅方向の延伸倍率を８倍にした以外は実施例１と同様にしてＰＴＦＥ多孔質膜を得た。(Example 2)
In Example 2, a PTFE porous membrane was obtained in the same manner as in Example 1 except that the stretching ratio in the width direction of the sheet-like molded body before drying was increased to 8.
（比較例）
比較例１のＰＴＦＥ多孔質膜は、従来のように、乾燥前に延伸を行わず、乾燥後に長手方向に９倍の延伸を行ったものである。(Comparative example)
The PTFE porous membrane of Comparative Example 1 is obtained by stretching 9 times in the longitudinal direction after drying without drying before drying as in the prior art.
比較例２および比較例３は、国際公開番号ＷＯ９０／０８８０１号公報に記載されているように、乾燥前に幅方向に４倍または８倍の予備延伸を行い、乾燥後に長手方向に９倍の延伸を行ったものである。 In Comparative Example 2 and Comparative Example 3, as described in International Publication No. WO 90/08801, pre-stretching is performed 4 times or 8 times in the width direction before drying, and 9 times in the longitudinal direction after drying. Stretched.
（引張試験）
上記の各ＰＴＦＥ多孔質膜に対して、長手方向および幅方向の引張最大荷重伸び（引張り強さに対応する伸び）を求めるために引張試験を行った。本試験では、各ＰＴＦＥ多孔質膜を測定対象の伸びの方向に延びる幅１０ｍｍの短冊状に切断し、このＰＴＦＥ多孔質膜を２５℃の環境下で２００ｍｍ／ｍｉｎの速度で引っ張った。そして、次の式から引張最大荷重伸びを求めた。
ｌ＝｛（Ｌ−Ｌ0）／Ｌ0｝×１００
ｌ：引張最大荷重伸び（％）
Ｌ：最大荷重時の標線間距離（ｍｍ）
Ｌ0：元の標線間距離（ｍｍ）
この同一試験を３回行って平均値を算出した。その結果は表１に示す通りであった。(Tensile test)
A tensile test was performed on each of the above PTFE porous membranes in order to obtain the maximum tensile load elongation (elongation corresponding to the tensile strength) in the longitudinal direction and the width direction. In this test, each PTFE porous membrane was cut into a strip shape having a width of 10 mm extending in the direction of elongation of the measurement object, and the PTFE porous membrane was pulled at a speed of 200 mm / min in an environment of 25 ° C. And the tension | pulling maximum load elongation was calculated | required from the following formula.
l = {(L−L0 ) / L0 } × 100
l: Maximum tensile load elongation (%)
L: Distance between marked lines at maximum load (mm)
L0 : Original distance between marked lines (mm)
This same test was performed three times to calculate an average value. The results were as shown in Table 1.
乾燥前に延伸を行わず、乾燥後に長手方向に延伸を行った比較例１のＰＴＦＥ多孔質膜では、長手方向の伸びが３０％であった。一方、乾燥前に予備延伸を行い、乾燥後に長手方向に延伸を行った比較例２および比較例３のＰＴＦＥ多孔質膜では、長手方向の伸びが４０％または５０％と少し改善したが、いずれも１００％を下回っている。 In the PTFE porous membrane of Comparative Example 1 which was not stretched before drying and stretched in the longitudinal direction after drying, the elongation in the longitudinal direction was 30%. On the other hand, in the PTFE porous membranes of Comparative Example 2 and Comparative Example 3 that were pre-stretched before drying and stretched in the longitudinal direction after drying, the elongation in the longitudinal direction was slightly improved to 40% or 50%. Is less than 100%.
これに対し、乾燥前および乾燥後に幅方向に延伸を行った実施例１および実施例２のＰＴＦＥ多孔質膜では、長手方向の伸びが１００％を大きく上回った。この結果から、本発明の製造方法によれば、ＰＴＦＥ多孔質膜の長手方向の伸びを飛躍的に大きくできることが分かる。 In contrast, in the PTFE porous membranes of Example 1 and Example 2 that were stretched in the width direction before and after drying, the elongation in the longitudinal direction greatly exceeded 100%. From this result, it can be seen that according to the manufacturing method of the present invention, the elongation in the longitudinal direction of the PTFE porous membrane can be remarkably increased.
また、幅方向に対する長手方向の伸び比は、比較例１、比較例２、および比較例３のＰＴＦＥ多孔質膜ではいずれも１を大きく下回っているのに対し、実施例１および実施例２のＰＴＦＥ多孔質膜ではどちらも１を大きく上回っており、本発明の製造方法によれば幅方向よりも長手方向に大きく延びるＰＴＦＥ多孔質膜を得られることが分かる。なお、本発明の製造方法によれば、幅方向の引張最大荷重伸びに対する長手方向の引張最大荷重伸びの倍率を、延伸倍率の設定により適宜選定することができるが、その倍率は１．１〜２００倍であることが好ましく、より好ましくは５〜５０倍である。 Further, the elongation ratio in the longitudinal direction with respect to the width direction is much lower than 1 in the PTFE porous membranes of Comparative Example 1, Comparative Example 2, and Comparative Example 3, whereas in Examples 1 and 2, Both of the PTFE porous membranes greatly exceed 1, and it can be seen that according to the production method of the present invention, a PTFE porous membrane extending greatly in the longitudinal direction than in the width direction can be obtained. In addition, according to the production method of the present invention, the ratio of the maximum tensile load elongation in the longitudinal direction relative to the maximum tensile load elongation in the width direction can be appropriately selected by setting the stretching ratio. It is preferably 200 times, more preferably 5 to 50 times.
（構造の比較）
走査型電子顕微鏡を用いて、実施例２、比較例２、および比較例３のＰＴＦＥ多孔質膜を１０００倍の倍率で撮影した写真が図４（ａ）〜図４（ｃ）である。図４（ｂ）および図４（ｃ）に示すように、乾燥前に幅方向に予備延伸し、乾燥後に長手方向に延伸した比較例２および比較例３の多孔質膜は、長手方向にフィブリルが伸びた構造を有しているのに対し、図４（ａ）に示すように、本発明の製造方法により製造した実施例２のＰＴＦＥ多孔質膜は幅方向にフィブリルが伸びた構造を有している。この結果から、本発明の製造方法で製造した、長手方向の伸びが向上したＰＴＦＥ多孔質膜は、特許文献２（国際公開第９０／０８８０１号パンフレット）に記載の方法により得られるＰＴＦＥ多孔質膜とは明らかに異なる構造を有していることが分かる。(Structure comparison)
4A to 4C are photographs of the PTFE porous membranes of Example 2, Comparative Example 2, and Comparative Example 3 taken at a magnification of 1000 using a scanning electron microscope. 4 (b) and 4 (c), the porous membranes of Comparative Example 2 and Comparative Example 3 that were pre-stretched in the width direction before drying and stretched in the longitudinal direction after drying were fibrillated in the longitudinal direction. 4 (a), the PTFE porous membrane of Example 2 manufactured by the manufacturing method of the present invention has a structure in which fibrils extend in the width direction. doing. From this result, the PTFE porous membrane with improved longitudinal elongation produced by the production method of the present invention is a PTFE porous membrane obtained by the method described in Patent Document 2 (International Publication No. 90/08801). It can be seen that it has a clearly different structure.
１ フィルタ
２ フィルタ用濾材
３ ＰＴＦＥ多孔質膜
３１ ノード
３２ フィブリル
４ 通気性支持材DESCRIPTION OF SYMBOLS 1 Filter 2 Filter medium 3 PTFE porous membrane 31 Node 32 Fibril 4 Breathable support material
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| JP2007186077AJP5148187B2 (en) | 2007-07-17 | 2007-07-17 | Method for producing polytetrafluoroethylene porous membrane, wound body, filter medium for filter, and method for producing the same |
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