JP2004339344A - Method for producing modified polytetrafluoroethylene film - Google Patents
Method for producing modified polytetrafluoroethylene film Download PDFInfo
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Abstract
Description
【0001】
【発明の属する技術分野】
本発明は、改質ポリテトラフルオロエチレン(以下、ポリテトラフルオロエチレンをPTFEという)フィルムの製造方法に関する。さらに詳述するなら、本発明は、燃料電池などの電解質膜基材に使用される耐放射線性を有するPTFEフィルムの製造方法に関するものである。本発明の製造方法による基材を使用すれば、従来は耐放射線性が乏しい故に困難であった、電解質膜基材の製造における放射線グラフト重合の適用が可能となる。
【0002】
【従来の技術】
PTFEは耐薬品性、耐熱性に優れており、産業用、民生用樹脂として広く利用されている。しかし、PTFEはγ線、電子線などの放射線に対する感受性が極めて大きく、放射線により分子切断が生じて機械的特性が低下する。そのためPTFEは放射線照射下において使用し難い。
【0003】
上記PTFEの耐放射線性に関する問題に対して、特許文献1には、短尺のPTFEフイルムに、PTFEの結晶融点以上の温度で酸素不在下において、1×103Gy以上の電離性放射線を照射して、当該PTFEフィルムを改質する方法が開示されている。かかる方法によれば、耐放射線性の改質されたPTFEフィルムが得られている。
【0004】
上記方法を、長尺PTFEフィルムに適用する場合には、当該フィルムを連続するライン上でPTFEの融点以上の高温に保持しつつ、しかも酸素不在下で連続的に放射線を照射しなければならず、腰のないフィルムを走行させるために複雑な設備となり、多大な設備投資を必要とするため、実用的な製造方法とはいえなかった。そこで、本発明者等はこの問題点を解決すべく検討を重ねた結果、PTFE粉末を塊状に圧縮成形した後、焼成して得られる成形物に、酸素不在下、PTFEの融点以上の温度にて、放射線を照射して前記塊状成形物を改質した後、これを切削して長尺フィルムとすることを特徴とする改質PTFEフィルムの製造方法を開発した(特許文献2を参照のこと)。
【0005】
しかしながら、特許文献2に記載される方法をスケールアップしたところ、得られるフィルムのフィルム強度や破断伸びは、塊状成形物の厚さ方向の外部表面から切削して約3mmまでは良好であったが、さらに、厚さ方向の外部表面から5mm以上になると、機械的物性が低下することが判明した。
【0006】
【特許文献1】特開平6−116423号公報
【特許文献2】特開2002−36376号公報
【0007】
【発明が解決しようとする課題】
本発明は、上記従来技術の問題点を解決するため、耐放射線性の良好な改質PTFEフィルムを、その機械的物性の低下を伴わず、多大な設備投資を必要とすることなく、製造しうる方法を提供することを目的とする。
【0008】
【課題を解決するための手段】
本発明者らは、上記課題を解決すべく鋭意検討を重ねた結果、以下に示す方法により上記目的を達成できることを見出し、本発明を完成するに至った。
【0009】
要するに、本発明は、PTFE粉末に、PTFEを融点近辺で放射線照射したときに発生する分解ガスを吸着する吸着剤を添加して、これらを塊状に圧縮成形した後、酸素不在下、PTFEの融点以上の温度にて、放射線を照射して前記塊状成形物を改質した後、これを切削して長尺フィルムとすることを特徴とする改質PTFEフィルムの製造方法である。
【0010】
吸着剤の添加目的は、放射線照射によって生成したPTFEからの分解ガスを円滑に吸着させることにより、PTFEの架橋の阻害を防止することにある。
【0011】
本発明の改質は、放射線照射によってPTFE分子鎖からF原子が離脱した主鎖のC同士が化学結合して架橋する、PTFEの架橋によって達成されると思料されるところ、このとき、離脱したF原子が元の主鎖Cに再結合しては架橋構造とならず、耐放射線性の改質効果は不充分なものとなる。従って、離脱したF原子がF2ガス等となってPTFEの架橋を阻害することのないよう、フッ素系分解ガスを系外へ拡散させる工夫が必要となる。
【0012】
本発明者等は、このフッ素系分解ガスを吸着剤にトラップすることにより、吸着剤による架橋阻害防止の効果を認め、本発明を完成した。
【0013】
上記本発明の製造方法によれば、PTFEの改質が、PTFEの塊状成形物に対して施されるため、特許文献1に開示されているPTFEフィルムに改質を施す方法に比べて非常に簡易な方法であり、多大な設備投資を必要としない。また、上記本発明の製造方法により得られる改質PTFEフィルムは、特許文献1に開示されているPTFEフィルムに改質を施したものと同様、PTFEに架橋構造等が付与されるため、優れた耐放射線性を有する。
【0014】
上記本発明の製造方法に従えば、長尺フィルムの厚さ調整は通常の切削と同様の方法により容易に行うことができる。ここで、本発明でいう長尺とは通常10mm以上をいう。
【0015】
本発明における放射線の線質は、透過力を有する線質が有用であり放射線のなかでもγ線またはX線もしくは電子線が本発明に適している。放射線として電子線を用いる場合には、透過力がよく、PTFEの塊状成形物の内部まで改質できる5×106電子ボルト以上、さらには7×106電子ボルト以上のものが好ましい。上記のように放射線の線質を選択することにより、効果的にPTFEフィルムの改質を行うことができる。
【0016】
【発明の実施の形態】
本発明の製造方法では、予めPTFE粉末に吸着剤を添加後、圧縮成形して塊状の成形物を調製しておく。成形物の焼成は、圧縮成形後にPTFEの融点以上に加熱して焼成してもよく、あるいは、放射線改質する際に融点以上の温度にすることにより焼成してもよい。
【0017】
本発明に使用する吸着剤は、PTFEを放射線照射した際に発生するフッ素系分解ガスを吸着するものを使用することができる。具体的には、活性炭、シリカゲル、活性アルミナ、酸化チタン、炭酸カルシウム、酸化カルシウム、水酸化カルシウム、金属酸化物等が挙げられ、これらから選択される1種又は2種以上の混合物を使用することができる。本発明を電解隔膜として使用する場合は、吸着剤として金属を含むと特性低下をきたすことがあることから、活性炭が好ましい。
【0018】
使用する吸着剤の粒径は10ミクロン以下の細かいものが好ましく、10ミクロンより大きいものは粉砕し、篩分けし、除去しておく。
【0019】
吸着剤の添加量はPTFEの重量の3%以下で充分であり、3%以上添加すると、得られるPTFEフィルムの機械的物性が低下する場合があることから、通常、PTFEの重量の0.01〜1%添加する。0.01%以下では添加効果が認められにくい。そして、充分均一に混合することが必要である。
【0020】
また、燃料電池用電解質膜の基材に使用する時は、活性炭のような電子導電性物質は好ましくないと想像されるが、実際には、1%以下なら実用上の電子絶縁性は損なわれず問題ない。
【0021】
PTFE粉末の粒子径は特に制限されないが、通常、0.1〜500μm程度とするのが好ましい。
【0022】
圧縮成形は、所望形状の金型に前記原料粉末を均一に充填し、通常、常温でプレスを挟んで100〜1000kgf/cm2程度で圧縮を行う。
【0023】
所望形状の金型は特に制限されず、得られる成形物が塊状となるようなものであれば、板状、円柱状、円筒状等のいずれでもよいが、塊状成形物を切削することによりフィルム化の容易な円筒状のものが好ましい。また、放射線として電子線を採用する場合には、塊状成形物(PTFE)内部に電子がチャージアップするおそれがあるので、チャージした電子を逃す細工、たとえば、塊状成形物を中空状とし、内面側にもアースをとることは有効である。
【0024】
圧縮成形による予備成形の後には、この予備成形物を金型から取り出し、炉に入れ、340〜360℃程度に昇温後、その温度で焼結が全体に均一に完了するまで保持する。これによりPTFEの焼結体である塊状の成形物が得られる。予備成形物の焼成は、圧縮成形後に行ってもよく、あるいは、放射線改質する際に行ってもよい。
【0025】
なお、上記は、塊状PTFE成形物の圧縮成形法として、フリーベイキング法を代表させて説明したが、適宜、ホットコイニング法、自動圧縮成形法、等圧圧縮成形法等を応用することもできる。
【0026】
次いで、上記の塊状成形物を、酸素不在下、340℃近辺の温度にて、放射線を照射して改質する。
【0027】
放射線の照射環境である「酸素不在下」とは、実質的な真空中(1Pa以下)ないしは窒素、ヘリウム、アルゴン等の不活性ガス雰囲気下をいう。
【0028】
照射温度はPTFEの結晶融点(327℃)以上であり、327℃以下では改質(架橋反応)が進行しない。一方、照射温度が高くなりすぎると、PTFEの分解が進み強度低下するため、照射温度の上限は360℃である。従って、照射温度は、好ましくは327℃〜360℃であり、更に好ましくは335〜345℃である。
【0029】
放射線量は、通常1×103Gy〜1×107Gy程度とする。PTFEの改質(架橋物性)を有効に発現させるためには、放射線量は1×104Gy以上とするのが好ましい。一方、放射線量を多くしすぎるとPTFEの分解が進むため、放射線量は1×106Gy以下とするのが好ましい。
【0030】
放射線照射により改質されたPTFEの塊状成形物は、切削して長尺フィルムとする。切削方法は特に制限されず、一般的なPTFEの切削工具を使用できる。また長尺フィルムの厚さに応じて、切削工具の種類、使用条件等は適宜に選択される。
【0031】
【実施例】
以下、実施例にて本発明を詳述するが、本発明はこれら実施例に限定されるものではない。
【0032】
実施例1
PTFEモールディングパウダー(ダイキン工業(株)製,品番ポリフロンTFEM−12)に、活性炭(和光純薬工業のCharcoa1 Activated Powder)を予め粉砕して10ミクロン以上の粒子を除去したものをPTFEの0.2重量%添加し、よく混合した。この混合粉末を内径200mmφ、肉厚30mm、高さ800mmφの金型に入れ、280kg/cm2の圧力で1時間圧縮して予備成形した。この予備成形品を金型から取り出し、360℃の炉に48時間入れ焼成した。外径約200mmφ、高さ500mmの円柱状ブロックを得た。次いで、この円柱状ブロックを内径300mmφ、高さ700mmのステンレス製の容器に入れ、容器内部の空気を窒素に置換し、更に容器の外周にバンドヒータを巻き内部温度を340℃±10℃に設定した後、20時間そのまま維持することで、円柱状ブロック全体を340℃±5℃にした。温度を340℃±5℃に維持しつつ、放射線を均一に照射するため容器を毎分1回転させながら、毎時2×103Gyのコバルト60γ線を50時間照射して(放射線量1×105Gy)、改質PTFEの円柱状ブロックを得た。
【0033】
この改質PTFEの円柱状ブロックを切削旋盤にて切削し、厚さ0.1mm、幅460mm、長さ150mの長尺PTFEフィルムを得た。
【0034】
実施例2
予めシリカゲル(和光純薬工業のSilica Ge1、Small Granular)を粉砕後、10ミクロン以上の粒子を除去したものを、PTFEの0.2重量%となるようPTFEモールディングパウダー(ダイキン工業(株)製,品番ポリフロンTFEM−12)に添加し、よく混合した。この混合粉末を内径200mmφ、肉厚30mm、高さ800mmφの金型に入れ、320kg/cm2の圧力で1時間圧縮して予備成形した。この予備成形品を金型から取り出し、360℃の炉に48時間入れ焼成し、外径約200mmφ、高さ500mmの円柱状ブロックを得た。
【0035】
以下は実施例1と同様に操作して、改質PTFEの円柱状ブロックを得た。そして、実施例1と同様に切削し、厚さ0.1mm、幅460mm、長さ150mm長尺PTFEフィルムを得た。
【0036】
(評価)
実施例で得られた改質PTFEフィルムについて、空気中、室温で、電子線を1×104Gy照射する前後の降伏点強度、破断伸びを万能引張り試験機にて、20℃で、200mm/分の引張り速度で測定した。また、比較例1として、未改質の切削PTFEシート(実施例1で焼成後、放射線照射せずに切削した0.1mm厚のシート)についても同様の測定を行った。評価結果を表1に示す。
【0037】
【表1】
【0038】
表1に示したように、改質PTFEフィルムでは、空気中で放射線を照射しても降伏点強度、破断伸びの低下が殆どなく耐放射線性に優れていることが認められる。
【0039】
【発明の効果】
本発明の製造方法によれば、耐放射線性の良好な改質PTFEフィルムを、多大な設備投資をすることなく製造することができる。特に、PTFEフィルムの厚さが1mm未満のものを製造する場合に有用である。
【0040】
得られた改質PTFEフィルムは、未改質のPTFEフィルムに比べて耐放射線性に優れている。本発明により得られた改質PTFEフィルムは、これまで使用が不可能であった放射線環境下での工業材料として使用できる。
【0041】
また、PTFEは耐放射線性に乏しいことから、放射線グラフト共重合では強度低下をきたすことから不向きであったが、本発明により得られた改質PTFEフィルムは耐放射線性を有するので、前照射法や同時照射法で放射線グラフト共重合してイオン交換膜や電池隔膜の基材として採用しうる物性とすることもできる。
【0042】
また改質PTFEフィルムは、未改質のPTFEフィルムによりも降状点強度が向上している。また、未改質のPTFEフィルムと同等の破断伸びを有し、低磨耗量といった物性にも優れる。このように改質PTFEフィルムはゴム特性を備えているので、シール材料やパッキン材料として耐熱、耐薬品性、耐クリープ性を具備した特性が要求させる各種用途へも利用できる。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for producing a modified polytetrafluoroethylene (hereinafter, polytetrafluoroethylene is referred to as PTFE) film. More specifically, the present invention relates to a method for producing a radiation-resistant PTFE film used for an electrolyte membrane substrate such as a fuel cell. The use of the substrate according to the production method of the present invention makes it possible to apply radiation graft polymerization in the production of an electrolyte membrane substrate, which was conventionally difficult due to poor radiation resistance.
[0002]
[Prior art]
PTFE has excellent chemical resistance and heat resistance, and is widely used as an industrial or consumer resin. However, PTFE has extremely high sensitivity to radiation such as γ-rays and electron beams, and molecular breaks occur due to the radiation, thereby deteriorating mechanical properties. Therefore, PTFE is difficult to use under irradiation of radiation.
[0003]
To solve the above-mentioned problem regarding the radiation resistance of PTFE, Patent Document 1 discloses that a short PTFE film is irradiated with ionizing radiation of 1 × 10 3 Gy or more in the absence of oxygen at a temperature equal to or higher than the crystal melting point of PTFE. Thus, a method for modifying the PTFE film is disclosed. According to such a method, a radiation-resistant modified PTFE film is obtained.
[0004]
When the above method is applied to a long PTFE film, the film must be continuously irradiated in the absence of oxygen while keeping the film at a high temperature equal to or higher than the melting point of PTFE on a continuous line. However, since complicated equipment is required for running a film having no rigidity and a large capital investment is required, it cannot be said that this is a practical manufacturing method. The inventors of the present invention have conducted various studies to solve this problem, and as a result, after compression-molding PTFE powder into a lump, a molded product obtained by firing is heated to a temperature higher than the melting point of PTFE in the absence of oxygen. Thus, a method for producing a modified PTFE film characterized by irradiating radiation to modify the mass-formed product and cutting the mass into a long film was developed (see Patent Document 2). ).
[0005]
However, when the method described in Patent Document 2 was scaled up, the film strength and elongation at break of the obtained film were good up to about 3 mm when cut from the external surface in the thickness direction of the massive molded product. Further, it was found that when the distance from the outer surface in the thickness direction was 5 mm or more, the mechanical properties were reduced.
[0006]
[Patent Document 1] JP-A-6-116423 [Patent Document 2] JP-A-2002-36376
[Problems to be solved by the invention]
In order to solve the above-mentioned problems of the prior art, the present invention is to produce a modified PTFE film having good radiation resistance without reducing mechanical properties and without requiring a large capital investment. The purpose of the present invention is to provide a method that can
[0008]
[Means for Solving the Problems]
The present inventors have conducted intensive studies to solve the above problems, and as a result, have found that the above object can be achieved by the following method, and have completed the present invention.
[0009]
In short, the present invention provides a method of adding an adsorbent for adsorbing decomposition gas generated when PTFE is irradiated near the melting point to PTFE powder, compression-molding these into a lump, and then, in the absence of oxygen, melting point of PTFE. A method for producing a modified PTFE film, which comprises irradiating radiation at the above temperature to modify the mass-formed product, and cutting the mass to form a long film.
[0010]
The purpose of the addition of the adsorbent is to prevent the inhibition of PTFE crosslinking by smoothly adsorbing the decomposed gas from PTFE generated by irradiation with radiation.
[0011]
The modification of the present invention is considered to be achieved by crosslinking of PTFE, in which the C of the main chain from which the F atom has been released from the PTFE molecular chain by irradiation is chemically bonded and crosslinked. When the F atom is recombined with the original main chain C, a crosslinked structure is not obtained, and the effect of improving the radiation resistance becomes insufficient. Therefore, leaving the F atoms so as not to inhibit the crosslinking of PTFE becomes F 2 gas or the like, it is necessary to devise to diffuse the fluorine-based decomposition gas to the outside of the system.
[0012]
The present inventors have recognized the effect of preventing crosslinking inhibition by the adsorbent by trapping the fluorine-based decomposition gas in the adsorbent, and have completed the present invention.
[0013]
According to the production method of the present invention, since the PTFE is modified on the PTFE bulk molded product, the PTFE modification is very much compared to the method of modifying the PTFE film disclosed in Patent Document 1. This is a simple method and does not require a large capital investment. Further, the modified PTFE film obtained by the production method of the present invention is excellent in that a cross-linked structure or the like is imparted to PTFE as in the case of modifying the PTFE film disclosed in Patent Document 1. Has radiation resistance.
[0014]
According to the production method of the present invention, the adjustment of the thickness of the long film can be easily performed by the same method as in ordinary cutting. Here, the term “long” in the present invention usually means 10 mm or more.
[0015]
As the radiation quality in the present invention, a radiation quality having a transmitting power is useful, and among the radiations, γ-rays, X-rays, or electron beams are suitable for the present invention. When an electron beam is used as the radiation, it is preferable that the electron beam has a good penetrating power and is 5 × 10 6 electron volts or more, and more preferably 7 × 10 6 electron volts or more, which can modify the inside of the PTFE bulk molding. By selecting the radiation quality as described above, the PTFE film can be effectively modified.
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
In the production method of the present invention, after adding an adsorbent to PTFE powder in advance, compression molding is performed to prepare a lump-shaped molded product. The firing of the molded article may be performed by heating to a temperature equal to or higher than the melting point of PTFE after compression molding, or may be performed at a temperature equal to or higher than the melting point during radiation modification.
[0017]
As the adsorbent used in the present invention, an adsorbent that adsorbs fluorine-based decomposition gas generated when PTFE is irradiated with radiation can be used. Specific examples include activated carbon, silica gel, activated alumina, titanium oxide, calcium carbonate, calcium oxide, calcium hydroxide, metal oxides, and the like, and one or a mixture of two or more selected from these may be used. Can be. When the present invention is used as an electrolytic membrane, activated carbon is preferable because the properties may be deteriorated if a metal is contained as an adsorbent.
[0018]
The particle size of the adsorbent used is preferably as small as 10 microns or less, and those larger than 10 microns are pulverized, sieved and removed.
[0019]
The amount of the adsorbent to be added is preferably 3% or less of the weight of PTFE, and if added at 3% or more, the mechanical properties of the obtained PTFE film may be reduced. Add ~ 1%. If it is less than 0.01%, the effect of addition is hard to be recognized. And it is necessary to mix them sufficiently uniformly.
[0020]
Also, when used as a base material for an electrolyte membrane for a fuel cell, an electronic conductive substance such as activated carbon is supposed to be unfavorable, but in practice, if it is 1% or less, practical electronic insulation is not impaired. no problem.
[0021]
Although the particle diameter of the PTFE powder is not particularly limited, it is usually preferable to be about 0.1 to 500 μm.
[0022]
In the compression molding, the raw material powder is uniformly filled in a mold having a desired shape, and the compression is usually performed at room temperature with a press at about 100 to 1000 kgf / cm 2 .
[0023]
The mold having the desired shape is not particularly limited, and may be any of a plate shape, a columnar shape, a cylindrical shape, and the like, as long as the obtained molded product has a lump shape. It is preferable to use a cylindrical material which can be easily formed. When an electron beam is used as the radiation, there is a possibility that the electrons may be charged up inside the massive molded product (PTFE). It is effective to take the ground as well.
[0024]
After the preforming by compression molding, the preformed product is taken out of the mold, placed in a furnace, heated to about 340 to 360 ° C., and held at that temperature until the sintering is completed uniformly. As a result, a massive molded product that is a sintered body of PTFE is obtained. The firing of the preform may be performed after compression molding, or may be performed during radiation modification.
[0025]
In the above, the free baking method has been described as a representative example of the compression molding method of the massive PTFE molded product. However, a hot coining method, an automatic compression molding method, an equal pressure compression molding method, or the like can be applied as appropriate.
[0026]
Next, the above-mentioned bulk molded article is irradiated with radiation at a temperature of around 340 ° C. in the absence of oxygen to modify it.
[0027]
The term "in the absence of oxygen", which is a radiation irradiation environment, refers to a substantially vacuum (1 Pa or less) or an atmosphere of an inert gas such as nitrogen, helium, or argon.
[0028]
The irradiation temperature is equal to or higher than the crystal melting point of PTFE (327 ° C.), and if it is lower than 327 ° C., the reforming (crosslinking reaction) does not proceed. On the other hand, if the irradiation temperature is too high, the decomposition of PTFE proceeds and the strength decreases, so the upper limit of the irradiation temperature is 360 ° C. Therefore, the irradiation temperature is preferably from 327C to 360C, and more preferably from 335C to 345C.
[0029]
The radiation dose is usually about 1 × 10 3 Gy to 1 × 10 7 Gy. The radiation dose is preferably 1 × 10 4 Gy or more in order to effectively express PTFE modification (crosslinking properties). On the other hand, if the radiation dose is too high, the decomposition of PTFE proceeds, so that the radiation dose is preferably 1 × 10 6 Gy or less.
[0030]
The block-shaped PTFE mass modified by irradiation is cut into a long film. The cutting method is not particularly limited, and a general PTFE cutting tool can be used. In addition, the type of cutting tool, use conditions, and the like are appropriately selected according to the thickness of the long film.
[0031]
【Example】
Hereinafter, the present invention will be described in detail with reference to examples, but the present invention is not limited to these examples.
[0032]
Example 1
Activated carbon (Charcoa1 Activated Powder of Wako Pure Chemical Industries, Ltd.) was previously pulverized into PTFE molding powder (manufactured by Daikin Industries, Inc., product number: Polyflon TFEM-12) to remove particles of 10 μm or more from PTFE 0.2. % By weight and mixed well. This mixed powder was placed in a mold having an inner diameter of 200 mmφ, a wall thickness of 30 mm, and a height of 800 mmφ, and was compressed at a pressure of 280 kg / cm 2 for 1 hour to be preformed. The preform was removed from the mold and placed in a furnace at 360 ° C. for 48 hours and fired. A cylindrical block having an outer diameter of about 200 mmφ and a height of 500 mm was obtained. Next, the cylindrical block is placed in a stainless steel container having an inner diameter of 300 mm and a height of 700 mm, the air inside the container is replaced with nitrogen, and a band heater is further wrapped around the outer periphery of the container to set the internal temperature to 340 ° C. ± 10 ° C. After that, the entire columnar block was kept at 340 ° C. ± 5 ° C. by keeping the same for 20 hours. While maintaining the temperature at 340 ° C. ± 5 ° C., the container is irradiated with 2 × 10 3 Gy / hour of cobalt 60γ ray for 50 hours while rotating the container once per minute for uniform irradiation with radiation (radiation dose 1 × 10 5 Gy) to obtain a columnar block of modified PTFE.
[0033]
The columnar block of the modified PTFE was cut by a cutting lathe to obtain a long PTFE film having a thickness of 0.1 mm, a width of 460 mm, and a length of 150 m.
[0034]
Example 2
Silica gel (Silica Ge1, Small Granular manufactured by Wako Pure Chemical Industries) was previously pulverized, and particles having a particle size of 10 μm or more were removed, and PTFE molding powder (manufactured by Daikin Industries, Ltd .; It was added to the product number Polyflon TFEM-12) and mixed well. This mixed powder was placed in a mold having an inner diameter of 200 mmφ, a wall thickness of 30 mm, and a height of 800 mmφ, and was compressed at a pressure of 320 kg / cm 2 for 1 hour to be preformed. The preformed product was taken out of the mold and placed in a furnace at 360 ° C. for 48 hours and fired to obtain a cylindrical block having an outer diameter of about 200 mmφ and a height of 500 mm.
[0035]
The following operations were performed in the same manner as in Example 1 to obtain a columnar block of modified PTFE. Then, cutting was performed in the same manner as in Example 1 to obtain a long PTFE film having a thickness of 0.1 mm, a width of 460 mm, and a length of 150 mm.
[0036]
(Evaluation)
Regarding the modified PTFE film obtained in the examples, the yield point strength and elongation at break before and after irradiation of an electron beam with 1 × 10 4 Gy in air at room temperature were measured at 20 ° C. at 200 ° C. using a universal tensile tester. It was measured at a pull rate of min. Further, as Comparative Example 1, the same measurement was performed on an unmodified cut PTFE sheet (a sheet having a thickness of 0.1 mm which was cut without being irradiated with radiation after firing in Example 1). Table 1 shows the evaluation results.
[0037]
[Table 1]
[0038]
As shown in Table 1, it is recognized that the modified PTFE film has almost no decrease in yield point strength and elongation at break even when irradiated with radiation in the air, and has excellent radiation resistance.
[0039]
【The invention's effect】
According to the production method of the present invention, a modified PTFE film having good radiation resistance can be produced without significant investment in equipment. In particular, it is useful when manufacturing a PTFE film having a thickness of less than 1 mm.
[0040]
The resulting modified PTFE film has better radiation resistance than the unmodified PTFE film. The modified PTFE film obtained according to the present invention can be used as an industrial material under a radiation environment, which has heretofore been impossible to use.
[0041]
In addition, PTFE is poor in radiation resistance and is not suitable for radiation graft copolymerization because of its reduced strength. However, since the modified PTFE film obtained by the present invention has radiation resistance, it is difficult to use a pre-irradiation method. Alternatively, radiation graft copolymerization may be performed by a simultaneous irradiation method to obtain physical properties that can be used as a base material for an ion exchange membrane or a battery membrane.
[0042]
In addition, the modified PTFE film has an improved yield point strength over the unmodified PTFE film. Further, it has an elongation at break equivalent to that of an unmodified PTFE film, and is excellent in physical properties such as low abrasion. Since the modified PTFE film has rubber properties as described above, it can be used for various applications that require properties having heat resistance, chemical resistance, and creep resistance as seal materials and packing materials.
Claims (4)
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Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP2008007703A (en) * | 2006-06-30 | 2008-01-17 | Hitachi Cable Ltd | Modified fluororesin composition and molded article using the same |
CN114228254A (en) * | 2022-01-20 | 2022-03-25 | 深圳市兴业卓辉实业有限公司 | Manufacturing method of high-concentration alcohol resistant composite bag |
-
2003
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Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP2008007703A (en) * | 2006-06-30 | 2008-01-17 | Hitachi Cable Ltd | Modified fluororesin composition and molded article using the same |
CN114228254A (en) * | 2022-01-20 | 2022-03-25 | 深圳市兴业卓辉实业有限公司 | Manufacturing method of high-concentration alcohol resistant composite bag |
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