JP3679043B2 - Cross-linked fluororesin composite material and method for producing the same - Google Patents
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Description
【０００１】
【発明の属する技術分野】
本発明はフッ素樹脂に加熱処理または放射線処理を施すことにより靭性や摺動特性、耐熱性などが向上した架橋フッ素樹脂複合材料に関する。
【０００２】
【従来の技術】
ポリテトラフルオロエチレンなどのフッ素樹脂は、優れた耐熱性、耐薬品性、撥水性、防汚性、潤滑性、耐摩擦性を有するプラスチックであり、これらの特徴を利用して、産業用や民生用のパッキン、ガスケット、チューブ、絶縁テープ、軸受けなどの材料として利用が拡大されつつある。しかし、ポリテトラフルオロエチレンは放射線に対する感受性が高く、照射線量が１ｋＧｙを超えると力学特性が低下するため、原子力施設などにおける放射線環境下で使用することはできない。また、摺動環境下では摩耗やクリープ変形が起こるために使用できない場合がある。また、ポリテトラフルオロエチレンは靭性が低く、材料にごくわずかな傷などの欠陥がある状態で応力が加わると、すぐに破壊してしまう。
【０００３】
これらの欠点を克服するために、放射線架橋によるフッ素樹脂の改質、あるいは充填剤や添加剤を加えるなどの方策が採られている。しかし、放射線架橋によって摺動環境下での摩耗やクリープ変形の問題は改善できるものの、靭性は改善されない。また、靭性を改善するために充填剤や添加剤を加えた場合、フッ素樹脂の優れた耐熱性や耐薬品性のために充填剤や添加剤がフッ素樹脂と化学反応することはなく、しかも、フッ素樹脂本来の優れた特徴、すなわち耐熱性、耐薬品性、撥水性、防汚性、潤滑性、力学特性などを低下させてしまう。
【０００４】
【発明が解決しようとする課題】
上記の問題点に鑑み、本発明の目的は、フッ素樹脂の優れた特徴である耐熱性、耐薬品性、撥水性、防汚性、潤滑性などを低下せしめることなく、フッ素樹脂の従来からの欠点であった低い靭性、摺動環境下での摩耗やクリープ変形、低い耐放射線性などの問題を一挙に解決し、フッ素樹脂の利用に制限があった工業分野においてこれを利用できるようにすることである。
【０００５】
【課題を解決するための手段】
上記課題を解決するため、本発明によれば、フッ化ピッチの粉体を添加したフッ素樹脂に加熱処理および／または放射線照射処理を施すことによってフッ素樹脂が架橋したフッ素樹脂複合材料であって、フッ化ピッチがフッ素樹脂と化学反応することによって分子複合化した網目構造を有することを特徴とする架橋フッ素樹脂複合材料が提供される。フッ素樹脂としてはポリテトラフルオロエチレン樹脂またはテトラフルオロエチレン系共重合樹脂を用いるのが好ましい。また、フッ化ピッチの粉体の添加量は、フッ素樹脂の量に対して０.０５〜５０重量％であるのが好ましい。
【０００６】
また、本発明によれば、上記のフッ素樹脂が連続繊維材料または短繊維材料と混合して繊維強化されている複合材料が提供される。連続繊維材料または短繊維材料としては、ＰＴＦＥ繊維、ガラス繊維、炭素繊維、炭化ケイ素繊維、窒化ケイ素繊維、アラミド繊維、ＰＢＯ繊維、および金属繊維から選択された１種または２種以上を用いるのが好ましい。
【０００７】
さらに、本発明によれば、金属部材の表面に上記の架橋フッ素樹脂複合材料がコーティングされている複合部材、すなわちフッ化ピッチの粉体を添加したフッ素樹脂に加熱処理および／または放射線照射処理を施すことによってフッ素樹脂が架橋したフッ素樹脂複合材料であってフッ化ピッチがフッ素樹脂と化学反応することによって分子複合化した網目構造を有するフッ素樹脂複合材料が金属部材の表面にコーティングされていることを特徴とする複合部材が提供される。金属部材としては例えば、アルミニウム、ステンレススチール、銅などからなる板材や筒状の部材を用いる。
【０００８】
また、本発明によれば、上記の架橋フッ素樹脂複合材料の製造方法であって、フッ化ピッチの粉体を添加したフッ素樹脂に加熱処理および／または放射線照射処理を施すことによってフッ素樹脂を架橋させるとともに、フッ化ピッチとフッ素樹脂を化学反応させることを特徴とする製造方法が提供される。加熱処理は１２０〜４００℃の温度範囲で行われるのが好ましい。また、放射線照射処理は０〜２００torrの酸素濃度の雰囲気中で室温から４００℃の温度範囲で行われ、放射線の照射線量は０.１kGy〜１０MGyであるのが好ましい。
【０００９】
また、本発明によれば、フッ化ピッチの粉体を添加したフッ素樹脂を連続繊維材料または短繊維材料に含浸し、この混合体に加熱処理および／または放射線照射処理を施すことによってフッ素樹脂を架橋させるとともに、フッ化ピッチとフッ素樹脂を化学反応させることを特徴とする架橋フッ素樹脂複合材料の製造方法が提供される。
【００１０】
さらに、本発明によれば、フッ化ピッチの粉体を添加したフッ素樹脂を金属部材の表面にコーティングし、次いで、フッ素樹脂に加熱処理および／または放射線照射処理を施すことによってフッ素樹脂を架橋させるとともに、フッ化ピッチとフッ素樹脂を化学反応させ、また同時にフッ素樹脂のコーティングと金属部材を強固に接着させることを特徴とする複合部材の製造方法が提供される。
【００１１】
【発明の実施の形態】
以下、本発明に係る架橋フッ素樹脂複合材料、複合部材、およびそれらの製造方法についての具体的な態様を説明する。
【００１２】
ポリテトラフルオロエチレン樹脂やテトラフルオロエチレン系共重合樹脂などのフッ素樹脂にフッ化ピッチを添加する工程は、フッ素樹脂の粉体が均一に分散した分散液にフッ化ピッチの粉体を添加して混合することにより行われる。粉体を効率よく分散するための液体すなわち分散媒は、水と乳化剤、水とアルコール、水とアセトン、または水とアルコールとアセトンの混合溶媒などであり、いずれも当業者であれば容易に選択し調製し得る。あるいは、分散液を用いずに、フッ素樹脂の微粉末にフッ化ピッチの粉体を添加して混合してもよい。フッ化ピッチの粉体の添加量は、フッ素樹脂の量に対して０.０５〜５０重量％であるのが好ましい。０.０５重量％未満であるとフッ化ピッチとフッ素樹脂が反応して分子複合化した網目構造の架橋密度が低くなり、フッ素樹脂の欠点である低い靭性、クリープ特性、摩耗特性などが十分に改善されない。一方、５０重量％を超えると架橋密度が大きくなり、硬くなるとともに脆くなるため、フッ素樹脂本来の特性を失ってしまう。
【００１３】
本発明で用いるフッ化ピッチの粉体は、平均分子量２０００〜３０００程度で平均粒径約１.２ミクロンのものである。その軟化温度は２７０℃程度であり、３００℃以上で分解し始める。フッ化ピッチは、フッ素ガス中でコールタール中の水素をフッ素に置換することによって得られる。このようなフッ化ピッチの粉体は大阪ガスケミカル（株）からリノベスＰ(登録商標)という商品名で市販されている。
【００１４】
フッ素樹脂を連続繊維材料または短繊維材料に含浸する工程は、上記のようにしてフッ化ピッチを添加したフッ素樹脂の分散液に繊維を浸すか、あるいはこの分散液を繊維に塗布することにより行われる。繊維材料として用いられるものは上記の通りであるが、１５０℃以上の耐熱性を有する繊維であって従来の繊維強化プラスチックにおいて用いられる全ての繊維を用いることができる。１５０℃以上の耐熱性が必要な理由は、フッ化ピッチとフッ素樹脂を反応させる際に行う熱処理によって繊維の強度が低下するのを防ぐためである。
【００１５】
フッ素樹脂を金属部材の表面にコーティングする工程は、フッ化ピッチを添加したフッ素樹脂の分散液を金属部材の表面に塗布するか、あるいは均一にスプレーすることなどにより行われる。金属部材として用いられるものは上記の通りであるが、１５０℃以上の融点を有する全ての金属を用いることができる。
【００１６】
かくして混合分散溶液を風乾あるいは熱風乾燥することによって分散媒を除去したもの、またはフッ素樹脂とフッ化ピッチを混合した粉体、またはフッ素樹脂と繊維の混合体のいずれかを任意の形状に成形したもの、あるいはフッ素樹脂を金属部材の表面にコーティングしたものを１２０〜４００℃、好ましくはフッ化ピッチの軟化点以上である２７０〜３６０℃の温度範囲で加熱処理する。これによって、フッ素樹脂が架橋するとともにフッ化ピッチとフッ素樹脂も熱化学反応して架橋する。すなわち、フッ素樹脂中に均一に分散したフッ化ピッチがフッ素樹脂と共有結合によって結びつけられるとともに、フッ素樹脂自体もフッ化ピッチによって誘起されたラジカルを介して共有結合により結合した状態になる。従って、分子複合的に橋かけした網目構造を有する複合材料、あるいはこの複合材料と金属部材が強固に接着した複合部材が得られる。加熱温度が４００℃を超えるとフッ素樹脂の熱分解が進行するため好ましくない。また加熱温度が１２０℃未満ではフッ化ピッチの分解が起きず、フッ素樹脂との間で反応が起きない。加熱手段としては、通常の気体循環式の恒温槽、赤外線ヒーター、パネルヒーターなどの間接的または直接的な熱源を用いることができる。あるいは熱プレス成形機のようなもので成形と加熱処理を同時に実施してもよい。
【００１７】
また上記の成形体を０〜２００torrの酸素濃度の雰囲気中で室温から４００℃の温度範囲、好ましくはフッ化ピッチの軟化点以上である２７０〜３６０℃の温度範囲に保ちながら放射線を０.１kGy〜１０MGyの照射線量で照射することによって、上記と同様の網目構造を有する複合材料あるいは複合部材が得られる。この方法によれば、より高い網目密度が得られる。０〜２００torrの酸素濃度の雰囲気とは、真空の他、ヘリウムや窒素などの不活性ガスで大気中の酸素を置き換えることによって酸素濃度を２００torr以下に制御した雰囲気をいう。このような雰囲気を用いることによって、照射中にフッ素樹脂の架橋反応が抑制されることなくフッ素樹脂の酸化分解が起こることが防がれる。酸素濃度が２００torrを超えると放射線によって誘起されたラジカルが酸素と優先的に結合し、架橋反応が著しく抑制されてしまう。照射線量が０.１kGy未満であると反応に寄与するラジカルの濃度が希薄となり、得られる複合材料の特性が十分に改善されない。一方、１０MGyを超えると架橋密度が大きくなり、硬くなるとともに脆くなり、フッ素樹脂として好ましい材料特性が失われる。放射線としては、電子線、Ｘ線、中性子線、高エネルギーイオンなどの電離性放射線を用い、これらのいずれかを単独で、あるいは混合して用いる。温度制御のための加熱手段としては、通常の気体循環式の恒温槽、赤外線ヒーター、パネルヒーターなどの間接的または直接的な熱源を用いることができる。あるいは、電子加速器またはイオン加速器から発生させる放射線のエネルギーを制御することによって発生する熱をそのまま熱源として利用してもよい。
【００１８】
かくして得られる複合材料または複合部材における架橋フッ素樹脂の網目密度は、フッ化ピッチの添加量、加熱温度、あるいは放射線照射線量を制御することによって任意に調整することができる。
【００１９】
本発明のフッ素樹脂複合材料においては、従来のフッ素樹脂よりも靭性、摺動環境下での摩耗やクリープ変形、耐放射線性などが著しく改善されている。その理由は次のように考えられる。
耐放射線性について：フッ化ピッチとフッ素樹脂が化学反応によって橋かけして分子複合化することにより分子内の架橋点でのイオン化ポテンシャルが低下し、架橋部位で放射線のエネルギー吸収が緩和される。従って、放射線に対する耐性が向上する。特にフッ化ピッチは分子中に芳香環を有していて、この芳香環を有する材料とフッ素樹脂が化学結合して網目構造が形成されるため、耐放射線性が向上しやすい。
靭性について：フッ素樹脂、特にポリテトラフルオロエチレンは剛直な分子であり、分子鎖間での相互作用性が低い。このためフッ素樹脂単体での架橋によっては、その剛直性や分子鎖間での相互作用性の低さがあだとなり、橋かけしても割れやすい、裂けやすいといった特徴が現れてしまう。本発明によれば、フッ化ピッチとフッ素樹脂が分子複合化することによって、フッ素樹脂における前記の欠点が構造的に緩和され、非常に粘り強い材料に変化する。
摩耗性について：フッ素樹脂は分子鎖間での相互作用性が低いため分子鎖集団が容易に脱離してしまうが、網目構造が形成されることによって分子鎖間での相互作用性が高められ、摩擦による分子鎖集団の脱離が防がれ、摩耗し難くなる。
クリープ変形について：網目構造が形成されることによって、分子鎖間での相互作用性の低さに起因する分子鎖間での滑りが抑制され、耐クリープ変形性が向上する。
【００２０】
【実施例】
以下に例を挙げて本発明を具体的に説明する。もっとも本発明はこれらの実施例に限定されず、当業者が容易に想到し得る種々の変更、改良、組み合わせ等も本発明の範囲内である。
【００２１】
実施例１
水と乳化剤からなる分散媒１００部（重量部、以下同様）に対して平均粒径０.２５μｍのポリテトラフルオロエチレン（以下ではＰＴＦＥという）のファインパウダー６０部およびフッ化ピッチ粉体（大阪ガスケミカル（株）製、リノベスＰ、以下ではＦＰという）５部を均一に分散させた液体を調製した。この液体を乾燥させて得たＰＴＦＥ/ＦＰブレンド体をＰＴＦＥの結晶融点以上の３５０℃において窒素気流中で１５分間焼成して、厚さ０.２mmのシート状に成形した。この成形シートおよび市販のＰＴＦＥシート（（株）ニチアス製、厚さ０.２mm）の熱特性を示差走査熱量分析装置（ＤＳＣ）を用いて分析した。得られた結果は表１の通りであり、ブレンド成形シートにおいては市販のＰＴＦＥシートに比べて結晶化温度の低下および結晶融点の低下が観測された。
【００２２】
【表１】
実施例２
実施例１のＰＴＦＥ/ＦＰブレンド成形シートおよび市販のＰＴＦＥシートについて、引き裂き試験を実施した。この引き裂き試験は、短辺４cm×長辺１０cmのシートの短辺の中央に縁から２cmの切り込みを入れて、切り込みの両側をチャックでつかみ、クロスヘッドスピード１００cm/分で引き裂くことによって、シートの強度を求めたものである。得られた結果は表２の通りであり、ブレンド成形シートの引き裂き強度は市販のＰＴＦＥシートよりも著しく高い。
【００２４】
【表２】
実施例３
実施例１のＰＴＦＥ/ＦＰブレンド成形シートおよび市販のＰＴＦＥシートについて、摩擦係数と摩耗係数の測定を行った。試験にはスラスト型摩擦摩耗試験装置を使用し、ＪＩＳ Ｋ7218に準じ、Ｓ４５Ｃ製の円筒状リング（外径２５.６mm、内径２０.６mm）を被試験体シートに２０kgf/cm2の圧力で押し付け、リングを１０m/minの速度で回転させた。得られた結果は表３の通りであり、ブレンド成形シートは良好な潤滑性を裏付ける低い摩擦係数を示し、かつ優れた耐摩耗性を有している。
【００２６】
【表３】
実施例４
実施例１のＰＴＦＥ/ＦＰブレンド成形シートおよび市販のＰＴＦＥシートをアルゴン気流中で３４０℃に加熱し、２MeVの電子線を３００kGyおよび５００kGy照射して架橋させた。それぞれについてＤＳＣを用いて熱特性を分析した。得られた結果は表４の通りであり、市販のＰＴＦＥシートと比較してブレンド成形シートにおいては融解温度および結晶化温度の低下、および結晶化熱量の低下の促進が観測された。
【００２８】
【表４】
実施例５
実施例４で３００kGy照射して架橋させたＰＴＦＥ/ＦＰブレンド成形シートおよび市販のＰＴＦＥシートについて、実施例２と同様の引き裂き試験を実施した。得られた結果は表５の通りであり、ブレンド成形シートの引き裂き強度は市販のＰＴＦＥシートよりも著しく高い。
【００３０】
【表５】
実施例６
水と乳化剤からなる分散媒１００部に対して平均粒径０.５μｍのＰＴＦＥファインパウダー５５部およびＦＰ１５部を均一に分散させた液体を調製した。この液体を乾燥させて得たＰＴＦＥ/ＦＰブレンド体をＰＴＦＥの結晶融点以上の３００℃において窒素気流中で３０分間焼成して、厚さ０.３mmのシート状に成形した。この成形シートおよび市販のＰＴＦＥシート（旭硝子（株）製、フロロポリマーズ（登録商標）、厚さ０.３mm）の熱特性をＤＳＣを用いて分析した。得られた結果は表６の通りであり、ブレンド成形シートにおいては市販のＰＴＦＥシートに比べて結晶化熱量の低下および結晶融点の低下が観測された。
【００３２】
【表６】
実施例７
実施例６のＰＴＦＥ/ＦＰブレンド成形シートおよび市販のＰＴＦＥシートについて、実施例３と同様の摩擦係数と摩耗係数の測定を行った。得られた結果は表７の通りであり、ブレンド成形シートは良好な潤滑性を裏付ける低い摩擦係数を示し、かつ優れた耐摩耗性を有している。
【００３４】
【表７】
実施例８
実施例６のＰＴＦＥ/ＦＰブレンド成形シートおよび市販のＰＴＦＥシートをヘリウム気流中で３４０℃に加熱し、２MeVの電子線を１００kGyおよび３００kGy照射して架橋させた。それぞれについてＤＳＣを用いて熱特性を分析した。得られた結果は表８の通りであり、市販のＰＴＦＥシートと比較してブレンド成形シートにおいては融解温度および結晶化温度の低下、および結晶化熱量の低下の促進が観測された。
【００３６】
【表８】
実施例９
水と乳化剤からなる分散媒１００部に対して平均粒径０.２μｍのＰＴＦＥのファインパウダー５０部およびＦＰ１０部を均一に分散させた液体を調製した。この液体に炭素繊維織布（東レ（株）製、トレカＴ-３００（登録商標））１枚を浸しては乾燥する操作を６回繰り返し、炭素繊維織布１００部に対してＰＴＦＥ/ＦＰブレンドパウダー１００部を含浸させたシートを調製した。このシートを６枚積層して、ＰＴＦＥの結晶融点以上の３４０℃において窒素気流中で１５分間焼成して板状（厚さ１.４mm）に成形した。比較のために、炭素繊維織布とＰＴＦＥファインパウダーのみからなる積層体も同じ製造条件で成形した。両者の成形板について、支点間距離５０mm、クロスヘッドスピード１mm/分で三点曲げ試験を実施した。得られた結果は表９の通りであり、炭素繊維強化ＰＴＦＥ/ＦＰ複合シートにおいては炭素繊維強化ＰＴＦＥシートに比べて著しく高い強度が示された。
【００３８】
【表９】
実施例１０
実施例１０の炭素繊維強化ＰＴＦＥ/ＦＰ複合シートおよび炭素繊維強化ＰＴＦＥシートのそれぞれを３４０℃に加熱した窒素雰囲気の照射容器に移し、２MeVの電子線を５００kGy照射して架橋させた。それぞれのシートについて実施例９と同様の三点曲げ試験を実施した。得られた結果は表１０の通りであり、炭素繊維強化ＰＴＦＥ/ＦＰ複合シートにおいて高い強度が示された。
【００４０】
【表１０】
実施例１１
水と乳化剤からなる分散媒１００部に対して平均粒径０.２５μｍのＰＴＦＥファインパウダー６０部およびＦＰ５部を均一に分散させた液体を調製した。この液体を１０cm四方で厚さ２mmのステンレススチール（SUS304）の表面に塗布し、５０℃で風乾した後、ＰＴＦＥの結晶融点以上の３３０℃において空気中で１０分間焼成し、これによって２０μｍの厚さのコーティングを施した。比較のために、ＰＴＦＥファインパウダーのみをコーティングしたコート材も同じ製造条件で作製した。それぞれのコート材について剥離試験を実施した。この剥離試験は、１０cm四方のコーティング面にカッターナイフで１cm間隔で縦横に線を入れて１００個の升目を作り、０℃の冷水に５分間浸した後、および１００℃の沸騰水に５分間浸した後、室温で粘着テープを用いて１００個の升目のうちいくつが剥離するかを試験したものである。得られた結果は表１１の通りであり、ＰＴＦＥ/ＦＰブレンド体コート材における剥離強度は著しく高かった。
【００４２】
【表１１】
実施例１２
実施例１１のＰＴＦＥ/ＦＰブレンド体コート材とＰＴＦＥコート材のそれぞれを３４０℃に加熱した窒素雰囲気の照射容器に移し、２５０keVの電子線を1００kGy照射して架橋させた。それぞれのコート材について実施例１１と同様の剥離試験を実施した。得られた結果は表１２の通りであり、ブレンド体コート材において高い強度が示された。
【００４４】
【表１２】
【発明の効果】
以上説明した通り、本発明に係る架橋フッ素樹脂複合材料は、従来のフッ素樹脂の特徴である高い耐熱性、耐薬品性、撥水性、防汚性、潤滑性などを備えているのみならず、耐放射線性、耐摩耗性、さらには引き裂き強度や曲げ強度において優れた材料である。従って、フッ素樹脂の用途を大幅に拡大させるものである。また、この架橋フッ素樹脂複合材料をコーティングした複合部材においては基材とコーティングの接着強度が極めて高く、上記の特性を備えた信頼性の高い複合部材である。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a cross-linked fluororesin composite material having improved toughness, sliding characteristics, heat resistance and the like by subjecting the fluororesin to heat treatment or radiation treatment.
[0002]
[Prior art]
Fluoropolymers such as polytetrafluoroethylene are plastics with excellent heat resistance, chemical resistance, water repellency, antifouling properties, lubricity, and friction resistance. As a material for packing, gaskets, tubes, insulating tapes, bearings, etc., the use is expanding. However, polytetrafluoroethylene is highly sensitive to radiation, and if the irradiation dose exceeds 1 kGy, the mechanical properties deteriorate, so it cannot be used in a radiation environment at a nuclear facility or the like. Further, it may not be used in a sliding environment due to wear and creep deformation. In addition, polytetrafluoroethylene has low toughness, and when a stress is applied in a state where the material has defects such as very few scratches, it immediately breaks down.
[0003]
In order to overcome these drawbacks, measures such as modification of fluororesin by radiation crosslinking or addition of fillers and additives are taken. However, although the problem of wear and creep deformation in a sliding environment can be improved by radiation crosslinking, toughness is not improved. In addition, when a filler or additive is added to improve toughness, the filler or additive does not chemically react with the fluororesin due to the excellent heat resistance and chemical resistance of the fluororesin, The original excellent characteristics of the fluororesin, that is, heat resistance, chemical resistance, water repellency, antifouling property, lubricity, mechanical properties and the like are deteriorated.
[0004]
[Problems to be solved by the invention]
In view of the above-mentioned problems, the object of the present invention is to reduce the conventional characteristics of fluororesins without deteriorating the excellent characteristics of fluororesins, such as heat resistance, chemical resistance, water repellency, antifouling properties, and lubricity. Resolving problems such as low toughness, wear and creep deformation in sliding environments, and low radiation resistance all at once, so that they can be used in industrial fields where the use of fluoropolymers is limited That is.
[0005]
[Means for Solving the Problems]
In order to solve the above problems, according to the present invention, a fluororesin composite material in which a fluororesin is crosslinked by applying heat treatment and / or radiation irradiation treatment to a fluororesin to which a powder of fluorinated pitch is added, There is provided a cross-linked fluororesin composite material characterized by having a network structure in which fluorinated pitch chemically reacts with a fluororesin to form a molecular composite. As the fluororesin, it is preferable to use polytetrafluoroethylene resin or tetrafluoroethylene copolymer resin. The addition amount of the fluorinated pitch powder is preferably 0.05 to 50% by weight with respect to the amount of the fluororesin.
[0006]
Moreover, according to this invention, the composite material by which said fluororesin is mixed with a continuous fiber material or a short fiber material, and is fiber-reinforced is provided. As the continuous fiber material or the short fiber material, one or more selected from PTFE fiber, glass fiber, carbon fiber, silicon carbide fiber, silicon nitride fiber, aramid fiber, PBO fiber, and metal fiber are used. preferable.
[0007]
Further, according to the present invention, a heat treatment and / or a radiation irradiation treatment is performed on a composite member in which the surface of the metal member is coated with the above-mentioned crosslinked fluororesin composite material, that is, a fluororesin having a powder of fluoride pitch added thereto. The surface of the metal member is coated with a fluororesin composite material in which the fluororesin is cross-linked and having a network structure in which the fluoride pitch chemically reacts with the fluororesin to form a molecular structure. A composite member is provided. As the metal member, for example, a plate material or a cylindrical member made of aluminum, stainless steel, copper, or the like is used.
[0008]
According to the present invention, there is also provided a method for producing the above-mentioned crosslinked fluororesin composite material, wherein the fluororesin is crosslinked by subjecting the fluororesin to which the powder of the fluorinated pitch has been subjected to heat treatment and / or radiation irradiation treatment. And a manufacturing method characterized by chemically reacting the fluorinated pitch and the fluororesin. The heat treatment is preferably performed in a temperature range of 120 to 400 ° C. Further, the radiation irradiation treatment is performed in a temperature range of room temperature to 400 ° C. in an atmosphere having an oxygen concentration of 0 to 200 torr, and the radiation irradiation dose is preferably 0.1 kGy to 10 MGy.
[0009]
Further, according to the present invention, a continuous resin material or a short fiber material is impregnated with a fluororesin to which a powder of fluorinated pitch is added, and the mixture is subjected to a heat treatment and / or a radiation irradiation treatment to obtain a fluororesin. Provided is a method for producing a crosslinked fluororesin composite material, characterized in that the fluorinated pitch and the fluororesin are chemically reacted while being crosslinked.
[0010]
Further, according to the present invention, the surface of the metal member is coated with a fluororesin to which powder of fluorinated pitch is added, and then the fluororesin is crosslinked by subjecting the fluororesin to heat treatment and / or radiation irradiation treatment. At the same time, there is provided a method for producing a composite member characterized in that a fluorinated pitch and a fluororesin are chemically reacted and at the same time, a fluororesin coating and a metal member are firmly bonded.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, specific modes of the cross-linked fluororesin composite material, the composite member, and the manufacturing method thereof according to the present invention will be described.
[0012]
The step of adding a fluorinated pitch to a fluororesin such as polytetrafluoroethylene resin or tetrafluoroethylene copolymer resin is performed by adding the fluorinated pitch powder to a dispersion in which the fluororesin powder is uniformly dispersed. This is done by mixing. Liquids or dispersion media for efficiently dispersing powder are water and emulsifiers, water and alcohol, water and acetone, or a mixed solvent of water, alcohol and acetone. Can be prepared. Alternatively, without using a dispersion, a fine powder of fluororesin may be added to a fine powder of fluororesin and mixed. The addition amount of the powder of fluorinated pitch is preferably 0.05 to 50% by weight with respect to the amount of the fluororesin. If it is less than 0.05% by weight, the crosslink density of the network structure in which the fluorinated pitch and the fluororesin react to form a molecular composite is lowered, and the low toughness, creep characteristics, wear characteristics, etc. that are the disadvantages of the fluororesin are sufficiently Not improved. On the other hand, if it exceeds 50% by weight, the crosslink density increases and becomes brittle and brittle, so that the original characteristics of the fluororesin are lost.
[0013]
The powder of fluorinated pitch used in the present invention has an average molecular weight of about 2000 to 3000 and an average particle size of about 1.2 microns. Its softening temperature is about 270 ° C., and it begins to decompose at 300 ° C. or higher. The fluorinated pitch is obtained by replacing hydrogen in coal tar with fluorine in fluorine gas. Such a powder of fluorinated pitch is commercially available from Osaka Gas Chemical Co., Ltd. under the trade name Rinoves P (registered trademark).
[0014]
The step of impregnating the fluororesin into the continuous fiber material or the short fiber material is performed by immersing the fiber in the fluororesin dispersion added with fluorinated pitch as described above or by applying the dispersion to the fiber. Is called. Although what is used as a fiber material is as above-mentioned, it is a fiber which has the heat resistance of 150 degreeC or more, Comprising: All the fibers used in the conventional fiber reinforced plastic can be used. The reason why heat resistance of 150 ° C. or higher is necessary is to prevent the strength of the fibers from being lowered by the heat treatment performed when the fluorinated pitch and the fluororesin are reacted.
[0015]
The step of coating the surface of the metal member with the fluororesin is performed by applying a dispersion of the fluororesin to which the fluorinated pitch is added to the surface of the metal member or spraying it uniformly. Although what is used as a metal member is as above-mentioned, all the metals which have melting | fusing point of 150 degreeC or more can be used.
[0016]
In this way, either the dispersion medium is removed by air-drying or hot-air drying of the mixed dispersion solution, or a powder obtained by mixing fluororesin and fluoride pitch, or a mixture of fluororesin and fiber is formed into an arbitrary shape. Or a metal member coated with a fluororesin is heat-treated at a temperature of 120 to 400 ° C., preferably 270 to 360 ° C. which is higher than the softening point of the fluorinated pitch. As a result, the fluororesin is cross-linked and the fluorinated pitch and the fluororesin are cross-linked by thermochemical reaction. That is, the fluorinated pitch uniformly dispersed in the fluororesin is bound to the fluororesin by a covalent bond, and the fluororesin itself is also bound by a covalent bond via a radical induced by the fluorinated pitch. Accordingly, it is possible to obtain a composite material having a network structure that is molecularly crosslinked or a composite member in which this composite material and a metal member are firmly bonded. A heating temperature exceeding 400 ° C. is not preferable because thermal decomposition of the fluororesin proceeds. If the heating temperature is less than 120 ° C., the fluorinated pitch does not decompose and no reaction occurs with the fluororesin. As the heating means, an indirect or direct heat source such as a normal gas circulation thermostat, an infrared heater, or a panel heater can be used. Or you may implement shaping | molding and heat processing simultaneously with things like a hot press molding machine.
[0017]
In addition, the above-mentioned molded body is kept in a temperature range of room temperature to 400 ° C. in an atmosphere having an oxygen concentration of 0 to 200 torr, preferably 0.1 kGy while maintaining a temperature range of 270 to 360 ° C. which is higher than the softening point of the fluoride pitch. By irradiating with an irradiation dose of -10 MGy, a composite material or composite member having a network structure similar to the above can be obtained. According to this method, a higher mesh density can be obtained. The atmosphere having an oxygen concentration of 0 to 200 torr refers to an atmosphere in which the oxygen concentration is controlled to 200 torr or less by replacing oxygen in the air with an inert gas such as helium or nitrogen in addition to vacuum. By using such an atmosphere, it is possible to prevent the oxidative decomposition of the fluororesin from occurring without suppressing the cross-linking reaction of the fluororesin during irradiation. When the oxygen concentration exceeds 200 torr, radicals induced by radiation are preferentially bonded to oxygen and the crosslinking reaction is remarkably suppressed. If the irradiation dose is less than 0.1 kGy, the concentration of radicals contributing to the reaction becomes dilute, and the properties of the resulting composite material are not sufficiently improved. On the other hand, if it exceeds 10 MGy, the crosslink density increases, and it becomes hard and brittle, and the material properties preferable as a fluororesin are lost. As the radiation, ionizing radiation such as electron beam, X-ray, neutron beam, high energy ion, etc. is used, and any one of them is used alone or in combination. As a heating means for temperature control, an indirect or direct heat source such as a normal gas circulation thermostat, an infrared heater, or a panel heater can be used. Alternatively, the heat generated by controlling the energy of the radiation generated from the electron accelerator or ion accelerator may be used as it is as a heat source.
[0018]
The network density of the crosslinked fluororesin in the composite material or composite member thus obtained can be arbitrarily adjusted by controlling the addition amount of the fluorinated pitch, the heating temperature, or the radiation irradiation dose.
[0019]
In the fluororesin composite material of the present invention, toughness, wear and creep deformation in a sliding environment, radiation resistance, etc. are remarkably improved as compared with conventional fluororesins. The reason is considered as follows.
Radiation resistance: Fluorinated pitch and fluororesin are cross-linked by chemical reaction to form a molecular complex, whereby the ionization potential at the cross-linking point in the molecule is lowered, and the energy absorption of radiation is mitigated at the cross-linking site. Therefore, resistance to radiation is improved. In particular, the fluorinated pitch has an aromatic ring in the molecule, and the material having the aromatic ring and the fluororesin are chemically bonded to form a network structure, so that the radiation resistance is easily improved.
About toughness: Fluororesin, especially polytetrafluoroethylene, is a rigid molecule and has low interaction between molecular chains. For this reason, depending on the cross-linking with the fluororesin alone, its rigidity and low interaction between the molecular chains are undesired, and the characteristics that it is easy to break and torn even when bridged appear. According to the present invention, when the fluorinated pitch and the fluororesin are made into a molecular complex, the above-mentioned drawbacks in the fluororesin are structurally relaxed and changed to a very tenacious material.
Abrasion: Fluororesin has low interaction between molecular chains, so the molecular chain population is easily detached, but the formation of a network structure increases the interaction between the molecular chains. Detachment of molecular chain population due to friction is prevented, and wear becomes difficult.
About creep deformation: By forming a network structure, slippage between molecular chains due to low interaction between molecular chains is suppressed, and creep deformation resistance is improved.
[0020]
【Example】
Hereinafter, the present invention will be specifically described with reference to examples. However, the present invention is not limited to these examples, and various modifications, improvements, combinations, and the like that can be easily conceived by those skilled in the art are within the scope of the present invention.
[0021]
Example 1
60 parts of fine powder of polytetrafluoroethylene (hereinafter referred to as PTFE) having an average particle diameter of 0.25 μm and fluorinated pitch powder (Osaka Gas) with respect to 100 parts (parts by weight, hereinafter the same) of a dispersion medium comprising water and an emulsifier. A liquid in which 5 parts of Chemical Co., Ltd. (Renoves P, hereinafter referred to as FP) were uniformly dispersed was prepared. The PTFE / FP blend obtained by drying this liquid was baked for 15 minutes in a nitrogen stream at 350 ° C., which is higher than the crystalline melting point of PTFE, to form a sheet having a thickness of 0.2 mm. The thermal characteristics of this molded sheet and a commercially available PTFE sheet (manufactured by NICHIAS CORPORATION, thickness 0.2 mm) were analyzed using a differential scanning calorimeter (DSC). The obtained results are as shown in Table 1. In the blend molded sheet, a decrease in the crystallization temperature and a decrease in the crystal melting point were observed as compared with a commercially available PTFE sheet.
[0022]
[Table 1]
Example 2
A tear test was performed on the PTFE / FP blend molded sheet of Example 1 and a commercially available PTFE sheet. This tear test is performed by making a 2 cm incision from the edge in the center of the short side of a sheet with a short side of 4 cm and a long side of 10 cm. The strength is obtained. The obtained results are as shown in Table 2, and the tear strength of the blend molded sheet is significantly higher than that of the commercially available PTFE sheet.
[0024]
[Table 2]
Example 3
The friction coefficient and the wear coefficient were measured for the PTFE / FP blend molded sheet of Example 1 and the commercially available PTFE sheet. A thrust type friction and wear test device is used for the test, and a S45C cylindrical ring (outer diameter 25.6 mm, inner diameter 20.6 mm) is pressed against the sheet under test at a pressure of 20 kgf / cm 2 in accordance with JIS K7218. The ring was rotated at a speed of 10 m / min. The obtained results are shown in Table 3. The blend molded sheet exhibits a low coefficient of friction that supports good lubricity, and has excellent wear resistance.
[0026]
[Table 3]
Example 4
The PTFE / FP blend molded sheet of Example 1 and a commercially available PTFE sheet were heated to 340 ° C. in an argon stream and crosslinked by irradiation with 2 MeV electron beams at 300 kGy and 500 kGy. Each was analyzed for thermal properties using DSC. The obtained results are as shown in Table 4. In the blend molded sheet, a decrease in melting temperature and crystallization temperature and an increase in crystallization heat amount were observed as compared with a commercially available PTFE sheet.
[0028]
[Table 4]
Example 5
The tear test similar to Example 2 was implemented about the PTFE / FP blend molded sheet | seat and the commercially available PTFE sheet which were bridge | crosslinked by irradiation of 300 kGy in Example 4. FIG. The obtained results are as shown in Table 5, and the tear strength of the blend molded sheet is significantly higher than that of the commercially available PTFE sheet.
[0030]
[Table 5]
Example 6
A liquid was prepared in which 55 parts of PTFE fine powder and 15 parts of FP having an average particle size of 0.5 μm were uniformly dispersed in 100 parts of a dispersion medium comprising water and an emulsifier. The PTFE / FP blend obtained by drying this liquid was baked for 30 minutes in a nitrogen stream at 300 ° C., which is higher than the crystalline melting point of PTFE, to form a sheet having a thickness of 0.3 mm. The thermal characteristics of this molded sheet and a commercially available PTFE sheet (Asahi Glass Co., Ltd., Fluoropolymers (registered trademark), thickness 0.3 mm) were analyzed using DSC. The obtained results are as shown in Table 6. In the blend molded sheet, a decrease in the amount of crystallization heat and a decrease in the crystal melting point were observed as compared with the commercially available PTFE sheet.
[0032]
[Table 6]
Example 7
For the PTFE / FP blend molded sheet of Example 6 and the commercially available PTFE sheet, the same friction coefficient and wear coefficient as those of Example 3 were measured. The obtained results are shown in Table 7. The blend molded sheet exhibits a low coefficient of friction that supports good lubricity and has excellent wear resistance.
[0034]
[Table 7]
Example 8
The PTFE / FP blend molded sheet of Example 6 and a commercially available PTFE sheet were heated to 340 ° C. in a helium stream and crosslinked by irradiation with 2 MeV electron beams at 100 kGy and 300 kGy. Each was analyzed for thermal properties using DSC. The obtained results are as shown in Table 8. In the blend molded sheet, a decrease in the melting temperature and the crystallization temperature and an acceleration in the decrease in the amount of crystallization heat were observed as compared with the commercially available PTFE sheet.
[0036]
[Table 8]
Example 9
A liquid was prepared in which 50 parts of PTFE fine powder having an average particle size of 0.2 μm and 10 parts of FP were uniformly dispersed in 100 parts of a dispersion medium comprising water and an emulsifier. Dipping one piece of carbon fiber woven fabric (Torayca T-300 (registered trademark)) in this liquid and drying is repeated 6 times, and PTFE / FP blend is performed on 100 parts of carbon fiber woven fabric. A sheet impregnated with 100 parts of powder was prepared. Six sheets were laminated and fired in a nitrogen stream for 15 minutes at 340 ° C., which is equal to or higher than the crystalline melting point of PTFE, to form a plate (thickness: 1.4 mm). For comparison, a laminate composed only of a carbon fiber woven fabric and PTFE fine powder was also molded under the same production conditions. A three-point bending test was performed on both molded plates at a fulcrum distance of 50 mm and a crosshead speed of 1 mm / min. The obtained results are as shown in Table 9, and the carbon fiber reinforced PTFE / FP composite sheet showed significantly higher strength than the carbon fiber reinforced PTFE sheet.
[0038]
[Table 9]
Example 10
Each of the carbon fiber reinforced PTFE / FP composite sheet and the carbon fiber reinforced PTFE sheet of Example 10 was transferred to an irradiation container in a nitrogen atmosphere heated to 340 ° C., and crosslinked by irradiation with an electron beam of 2 MeV at 500 kGy. The same three-point bending test as in Example 9 was performed on each sheet. The obtained results are as shown in Table 10, and high strength was shown in the carbon fiber reinforced PTFE / FP composite sheet.
[0040]
[Table 10]
Example 11
A liquid was prepared by uniformly dispersing 60 parts of PTFE fine powder having an average particle size of 0.25 μm and 5 parts of FP with respect to 100 parts of a dispersion medium comprising water and an emulsifier. This liquid was applied to the surface of 10 mm square and 2 mm thick stainless steel (SUS304), air-dried at 50 ° C., and then baked in air at 330 ° C. above the crystalline melting point of PTFE for 10 minutes. The coating was applied. For comparison, a coating material coated only with PTFE fine powder was also produced under the same production conditions. A peel test was performed on each coating material. In this peel test, 100 squares were made on a 10 cm square coated surface with a cutter knife at 1 cm intervals to make 100 squares, immersed in cold water at 0 ° C. for 5 minutes, and then in boiling water at 100 ° C. for 5 minutes. After immersion, it was tested how many of 100 squares peeled off using an adhesive tape at room temperature. The obtained results are as shown in Table 11, and the peel strength in the PTFE / FP blend coating material was remarkably high.
[0042]
[Table 11]
Example 12
Each of the PTFE / FP blend coating material and the PTFE coating material of Example 11 was transferred to an irradiation container in a nitrogen atmosphere heated to 340 ° C., and crosslinked by irradiation with 100 kGy of a 250 keV electron beam. The same peel test as in Example 11 was performed on each coating material. The obtained results are as shown in Table 12, and high strength was shown in the blend coating material.
[0044]
[Table 12]
【The invention's effect】
As described above, the cross-linked fluororesin composite material according to the present invention not only has high heat resistance, chemical resistance, water repellency, antifouling property, lubricity, etc., which are the characteristics of conventional fluororesins, It is a material excellent in radiation resistance, wear resistance, tear strength and bending strength. Therefore, the use of fluororesin is greatly expanded. Moreover, the composite member coated with the cross-linked fluororesin composite material has a very high adhesive strength between the base material and the coating, and is a highly reliable composite member having the above-mentioned characteristics.
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| EP2527397A1 (en) | 2005-10-31 | 2012-11-28 | Daikin Industries, Ltd. | Method for molding polytetrafluoroethylene, polytetrafluoroethylene molded body, crosslinkable polytetrafluoroethylene, powdered polytetrafluoroethylene crosslinked body, resin blend composition of matter and resin blend molded body |
| JP5472689B2 (en) * | 2009-06-18 | 2014-04-16 | 日立金属株式会社 | Modified fluororesin composition and molded body |
| JP5663218B2 (en) * | 2010-07-09 | 2015-02-04 | オリンパス株式会社 | Thermoplastic resin composition and method for producing the same |
| EP3103830A4 (en) | 2014-02-03 | 2017-11-08 | NTN Corporation | Sliding member, rolling axle bearing, and holder |
| JP6577193B2 (en) * | 2014-03-24 | 2019-09-18 | Ntn株式会社 | Roller bearing cage and rolling bearing |
| JP6452134B2 (en) * | 2014-06-13 | 2019-01-16 | ダイキン工業株式会社 | Aquatic organism adhesion prevention material |
| JP2016089731A (en) * | 2014-11-05 | 2016-05-23 | 大豊工業株式会社 | Bearing housing of turbocharger |
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