JP2004358397A - Surfactant, production method of fluorine-containing polymer, and fluorine-containing polymer aqueous dispersion - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fluorine-containing phosphoric acid derivative in form of particles of a fluorine-containing phosphoric acid with a small particle diameter by making the polymer exist in emulsification polymerization. <P>SOLUTION: The surfactant comprises a fluorine-containing phosphoric acid derivative defined by the following formula: (i) Rf-(CH<SB>2</SB>)<SB>n</SB>-PO(OM)<SB>2</SB>wherein M represents NH<SB>4</SB>, Li, Na, K or H; n represents an integer of 1 to 3; and Rf represents an alkyl having 1 to 6 carbon atoms and one or more fluorine atoms. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【００４０】
（式中、Ｒｆ^４は炭素数１〜６のパーフルオロアルキル基；ｊは０〜５の整数）で表されるものである。
【００４１】
本発明の製造方法により好適に製造される上述の（Ｉ）非溶融加工性樹脂、（ＩＩ）溶融加工性樹脂及び（ＩＩＩ）エラストマー性重合体は、以下の態様で製造することが好ましい。
【００４２】
（Ｉ）非溶融加工性樹脂
本発明の製造方法において、ＰＴＦＥ重合体の重合は、通常、重合温度１０〜１００℃、重合圧力０．０５〜５ＭＰａＧにて行われる。
上記重合は、攪拌機を備えた耐圧の反応容器を、脱酸素後、ＴＦＥを仕込み、所定の温度にし、重合開始剤を添加して反応を開始する。反応の進行とともに圧力が低下するので、初期圧力を維持するように、追加のＴＦＥを連続的又は間欠的に追加供給する。所定量のＴＦＥを供給した時点で、供給を停止し、反応容器内のＴＦＥをパージし、温度を室温に戻して反応を終了する。
【００４３】
上記ＰＴＦＥ重合体の製造において、知られている各種変性モノマーを併用することもできる。本明細書において、ポリテトラフルオロエチレン重合体［ＰＴＦＥ重合体］は、ＴＦＥ単独重合体のみならず、ＴＦＥと変性モノマーとの共重合体であって、非溶融加工性であるもの（以下、「変性ＰＴＦＥ」という。）をも含む概念である。
上記変性モノマーとしては、例えば、ＨＦＰ、ＣＴＦＥ等のパーハロオレフィン；炭素原子１〜５個、特に炭素原子１〜３個を有するアルキル基を持つフルオロ（アルキルビニルエーテル）；フルオロジオキソール等の環式のフッ素化された単量体；パーハロアルキルエチレン；ω―ヒドロパーハロオレフィン等が挙げられる。変性モノマーの供給は、目的や、ＴＦＥの供給に応じて、初期一括添加、又は、連続的若しくは間欠的に分割添加を行うことができる。
変性ＰＴＦＥ中の変性モノマー含有率は、通常、０．００１〜２モル％の範囲である。
【００４４】
上記ＰＴＦＥ重合体の製造において、上述の本発明の界面活性剤は、上記本発明の含フッ素重合体の製造方法における使用範囲で用いることができるが、通常、水性媒体の０．０００１〜５質量％の量を添加する。上記界面活性剤の濃度は、上記範囲であれば特に限定されないが、通常、重合開始時に臨界ミセル濃度（ＣＭＣ）以下で添加される。添加量が多いとアスペクト比の大きい針状粒子が生成し、水性分散体がゲル状となり安定性が損なわれる。
【００４５】
上記ＰＴＦＥ重合体の製造において、重合開始剤としては、過硫酸塩（例えば、過硫酸アンモニウム）や、ジコハク酸パーオキシド、ジグルタル酸パーオキシド等の有機過酸化物を、単独で又はこれらの混合物の形で使用することができる。また、亜硫酸ナトリウム等の還元剤と共用し、レドックス系にして用いてもよい。更に、重合中に、ヒドロキノン、カテコール等のラジカル捕捉剤を添加したり、亜硫酸アンモニウム等のパーオキサイドの分解剤を添加し、系内のラジカル濃度を調整することもできる。
【００４６】
上記ＰＴＦＥ重合体の製造において、連鎖移動剤としては、公知のものが使用できるが、例えば、メタン、エタン、プロパン、ブタン等の飽和炭化水素、クロロメタン、ジクロロメタン、ジフルオロエタン等のハロゲン化炭化水素類、メタノール、エタノール等のアルコール類、水素等が挙げられるが、常温常圧で気体状態のものが好ましい。
上記連鎖移動剤の使用量は、通常、供給されるＴＦＥ全量に対して、１〜１０００ｐｐｍであり、好ましくは１〜５００ｐｐｍである。
【００４７】
上記ＰＴＦＥ重合体の製造において、更に、反応系の分散安定剤として、実質的に反応に不活性であって、上記反応条件で液状となる炭素数が１２以上の飽和炭化水素を、水性媒体１００質量部に対して２〜１０質量部使用することもできる。また、反応中のｐＨを調整するための緩衝剤として、炭酸アンモニウム、リン酸アンモニウム等を添加してもよい。
【００４８】
本発明によって得られるＰＴＦＥ重合体の水性分散液は、重合が終了した時点で、固形分濃度が１０〜４０質量％、平均粒子径が０．０５〜５０００μｍ、特に本発明の界面活性剤を使用することによって０．２μｍ以下の微小粒子径のＰＴＦＥ重合体からなる粒子を有する水性分散液を得ることができる。上記重合終了時のＰＴＦＥ重合体は、数平均分子量が１，０００〜１０，０００，０００のものである。
【００４９】
上記ＰＴＦＥ重合体の水性分散液は、凝析と乾燥とを経てファインパウダーとして各種用途に使用することができる。
上記ＰＴＦＥ重合体の水性分散液に対して凝析を行う場合、通常、ポリマーラテックス等の乳化重合により得た水性分散液を、水を用いて１０〜２０質量％のポリマー濃度になるように希釈し、場合によっては、ｐＨを中性又はアルカリ性に調整した後、撹拌機付きの容器中で反応中の撹拌よりも激しく撹拌して行う。上記凝析は、メタノール、アセトン等の水溶性有機化合物、硝酸カリウム、炭酸アンモニウム等の無機塩や、塩酸、硫酸、硝酸等の無機酸等を凝析剤として添加しながら撹拌を行ってもよい。上記凝析は、また、インラインミキサー等を使用して連続的に行ってもよい。
【００５０】
上記凝析前や凝析中に、着色のための顔料や機械的性質を改良するための各種充填剤を添加すれば、顔料や充填剤が均一に混合した顔料入り又は充填剤入りのＰＴＦＥ重合体ファインパウダーを得ることができる。
【００５１】
上記ＰＴＦＥ重合体の水性分散液を凝析して得られた湿潤粉末の乾燥は、通常、上記湿潤粉末をあまり流動させない状態、好ましくは静置の状態を保ちながら、真空、高周波、熱風等の手段を用いて行う。粉末同士の、特に高温での摩擦は、一般にファインパウダー型のＰＴＦＥ重合体に好ましくない影響を与える。これは、この種のＰＴＦＥ重合体からなる粒子が小さな剪断力によっても簡単にフィブリル化して、元の安定な粒子構造の状態を失う性質を持っているからである。
【００５２】
上記乾燥は、１０〜２５０℃、好ましくは１００〜２００℃の乾燥温度で行う。得られるＰＴＦＥ重合体ファインパウダーは、成形用として好ましく、好適な用途としては、航空機及び自動車等の油圧系、燃料系のチューブ等が挙げられ、薬液、蒸気等のフレキシブルホース、電線被覆用途等が挙げられる。
【００５３】
上記重合により得られたＰＴＦＥ重合体の水性分散液は、また、ノニオン性界面活性剤を加えることにより、安定化して更に濃縮し、目的に応じ、有機又は無機の充填剤を加えた組成物として各種用途に使用することも好ましい。上記組成物は、金属又はセラッミクスからなる基材上に被覆することにより、非粘着性と低摩擦係数を有し、光沢や平滑性、耐摩耗性、耐候性及び耐熱性に優れた塗膜表面とすることができ、ロールや調理器具等の塗装、ガラスクロスの含浸加工等に適している。
【００５４】
（ＩＩ）溶融加工性樹脂
（１）本発明の製造方法において、ＦＥＰ重合は、通常、重合温度６０〜１００℃、重合圧力０．７〜４．５ＭｐａＧにて行うことが好ましい。
ＦＥＰの好ましい単量体組成（質量％）は、ＴＦＥ：ＨＦＰ＝（６０〜９５）：（５〜４０）、より好ましくは（８５〜９０）：（１０〜１５）である。上記ＦＥＰとしては、また、更に第３成分としてパーフルオロ（アルキルビニルエーテル）類を用い、全単量体の０．５〜２質量％である範囲内で変性させたものであってもよい。
上記ＦＥＰの重合において、上述の本発明の界面活性剤は、本発明の製造方法における使用範囲で用いることができるが、通常、水性媒体の０．０００１〜５質量％の量を添加する。
上記ＦＥＰの重合において、連鎖移動剤としては、シクロヘキサン、メタノール、エタノール、四塩化炭素、クロロホルム、塩化メチレン、塩化メチル等を使用することが好ましく、ｐＨ緩衝剤としては、炭酸アンモニウム、燐酸水素二ナトリウム等を使用することが好ましい。
【００５５】
（２）本発明の製造方法において、ＰＦＡ、ＭＦＡ等のＴＦＥ／パーフルオロ（アルキルビニルエーテル）共重合体の重合は、通常、重合温度６０〜１００℃、重合圧力０．７〜２．５ＭｐａＧで行うことが好ましい。
ＰＦＡの好ましい単量体組成（モル％）は、ＴＦＥ：パーフルオロ（アルキルビニルエーテル）＝（９５〜９９．７）：（０．３〜５）、より好ましくは（９８〜９９．５）：（０．５〜２）である。パーフルオロ（アルキルビニルエーテル）としては、式：ＣＦ_２＝ＣＦＯＲｆ（式中、Ｒｆは炭素数１〜６のパーフルオロアルキル基）で表されるものを使用することが好ましい。
上記ＴＦＥ／パーフルオロ（アルキルビニルエーテル）共重合体の重合において、上述の本発明の界面活性剤は、本発明の製造方法における使用範囲で用いることができるが、通常、水性媒体の０．０００１〜２質量％の量で添加する。
上記ＴＦＥ／パーフルオロ（アルキルビニルエーテル）共重合体の重合において、連鎖移動剤としてシクロヘキサン、メタノール、エタノール、四塩化炭素、クロロホルム、塩化メチレン、塩化メチル、メタン、エタン等を使用することが好ましく、ｐＨ緩衝剤として、炭酸アンモニウム、燐酸水素二ナトリウム等を使用することが好ましい。
【００５６】
（３）本発明の製造方法において、ＥＴＦＥの重合は、通常、重合温度２０〜１００℃、重合圧力０．５〜０．８ＭＰａＧで行うことが好ましい。
ＥＴＦＥの好ましい単量体組成（モル％）は、ＴＦＥ：エチレン＝（５０〜９９）：（５０〜１）である。上記ＥＴＦＥとしては、また、更に第３モノマーを用い、全単量体の０〜２０質量％である範囲内で変性させたものであってもよい。好ましくは、ＴＦＥ：エチレン：第３モノマー＝（７０〜９８）：（３０〜２）：（４〜１０）である。上記第３モノマーとしては、パーフルオロブチルエチレン、２，３，３，４，４，５，５−ヘプタフルオロ−１−ペンテン（ＣＨ_２＝ＣＦＣＦ_２ＣＦ_２ＣＦ_２Ｈ）、２−トリフルオロメチル−３，３，３−トリフルオロプロペン（（ＣＦ_３）_２Ｃ＝ＣＨ_２）が好ましい。
上記ＥＴＦＥの重合において、上述の本発明の界面活性剤は、本発明の製造方法における使用範囲で用いることができるが、通常、水性媒体の０．０００１〜２質量％の量で添加する。
上記ＥＴＦＥの重合において、連鎖移動剤として、シクロヘキサン、メタノール、エタノール、四塩化炭素、クロロホルム、塩化メチレン、塩化メチル等を使用することが好ましい。
【００５７】
（ＩＩＩ）エラストマー性重合体
本発明の製造方法において、エラストマー性重合体の重合は、攪拌機を備えた耐圧の反応容器を、脱酸素後、モノマーを仕込み、所定の温度にし、重合開始剤を添加して、反応を開始する。反応の進行とともに圧力が低下するので、初期圧力を維持するように、追加のモノマーを連続的又は間欠的に追加供給する。所定量のモノマーを供給した時点で、供給を停止し、反応容器内のモノマーをパージし、温度を室温に戻して反応を終了する。乳化重合する場合、ポリマーラテックスを連続的に反応容器より取り出すことが好ましい。
特に、熱可塑性エラストマーを製造する場合、ＷＯ００／０１７４１号パンフレットに開示されているように、一旦重合体微粒子を高い界面活性剤濃度で合成してから希釈して更に重合を行うことで、通常の重合に比べて、最終的な重合速度を速くできる方法を使用することも可能である。
【００５８】
上記エラストマー性重合体の重合は、目的とするポリマーの物性、重合速度制御の観点から適宜条件を選択するが、重合温度は通常−２０〜２００℃、好ましくは５〜１５０℃、重合圧力は通常０．５〜１０ＭＰａＧ、好ましくは１〜７ＭＰａＧにて行われる。また、重合媒体中のｐＨは、公知の方法等により、後述するｐＨ調整剤等を用いて、通常２．５〜９に維持することが好ましい。
【００５９】
上記エラストマー性重合体の重合に用いる単量体としては、フッ化ビニリデンの他に、炭素原子と少なくとも同数のフッ素原子を有しフッ化ビニリデンと共重合し得る含フッ素エチレン性不飽和単量体が挙げられる。上記含フッ素エチレン性不飽和単量体としては、トリフルオロプロペン、ペンタフルオロプロペン、へキサフルオロブテン、オクタフルオロブテンが挙げられる。なかでも、へキサフルオロプロペンは、それが重合体の結晶成長を遮断した場合に得られるエラストマーの特性のために特に好適である。上記含フッ素エチレン性不飽和単量体としては、また、トリフルオロエチレン、ＴＦＥ及びＣＴＦＥ等が挙げられるし、１種若しくは２種以上の塩素及び／又は臭素置換基をもった含フッ素単量体を用いることもできる。パーフルオロ（アルキルビニルエーテル）、例えばパーフルオロ（メチルビニルエーテル）も用いることができる。ＴＦＥ及びＨＦＰは、エラストマー性重合体を製造するのに好ましい。
エラストマー性重合体の好ましい単量体組成（質量％）は、フッ化ビニリデン：ＨＦＰ：ＴＦＥ＝（２０〜７０）：（２０〜６０）：（０〜４０）である。この組成のエラストマー性重合体は、良好なエラストマー特性、耐薬品性、及び、熱的安定性を示す。
【００６０】
上記エラストマー性重合体の重合において、上述の本発明の界面活性剤は、本発明の製造方法における使用範囲で用いることができるが、通常、水性媒体に対して０．０００１〜５質量％の量で添加する。
【００６１】
上記エラストマー性重合体の重合において、重合開始剤としては、公知の無機ラジカル重合開始剤を使用することができる。上記無機ラジカル重合開始剤としては、従来公知の水溶性無機過酸化物、例えば、ナトリウム、カリウム及びアンモニウムの過硫酸塩、過リン酸塩、過硼酸塩、過炭素塩又は過マンガン酸塩が特に有用である。上記ラジカル重合開始剤は、更に、還元剤、例えば、ナトリウム、カリウム又はアンモニウムの亜硫酸塩、重亜硫酸塩、メタ重亜硫酸塩、ハイポ亜硫酸塩、チオ硫酸塩、亜リン酸塩若しくはハイポ亜リン酸塩により、又は、容易に酸化される金属化合物、例えば第一鉄塩、第一銅塩若しくは銀塩により、更に活性化することができる。好適なラジカル重合開始剤は、過硫酸アンモニウムであり、過硫酸アンモニウムと重亜硫酸ナトリウムと共にレドックス系において使用することが、より好ましい。
上記重合開始剤の添加濃度は、目的とするポリマーの分子量や、重合反応速度によって適宜決定されるが、モノマー全量の０．０００１〜１０質量％、好ましくは０．０１〜５質量％の量に設定する。
【００６２】
上記エラストマー性重合体の重合において、連鎖移動剤としては、公知のものを使用することができるが、ＰＶＤＦの重合では、炭化水素、エステル、エーテル、アルコール、ケトン、塩素化合物、カーボネート等を用いることができ、熱可塑性エラストマーでは、炭化水素、エステル、エーテル、アルコール、塩素化合物、ヨウ素化合物等を用いることができる。なかでも、ＰＶＤＦの重合では、アセトン、イソプロピルアルコールが好ましく、熱可塑性エラストマーの重合では、イソペンタン、マロン酸ジエチル及び酢酸エチルは、反応速度が低下しにくいという観点から好ましく、Ｉ（ＣＦ_２）_４Ｉ、Ｉ（ＣＦ_２）_６Ｉ、ＩＣＨ_２Ｉ等のジヨウ素化合物は、ポリマー末端のヨウ素化が可能で、反応性ポリマーとして使用できる観点から好ましい。
上記連鎖移動剤の使用量は、供給されるモノマー全量に対して、通常、通常０．５×１０^−３〜５×１０^−３モル％、好ましくは１．０×１０^−３〜３．５×１０^−３モル％である。
【００６３】
上記エラストマー性重合体の重合において、ＰＶＤＦの重合では、乳化安定剤としてパラフィンワックス等を好ましく用いることができ、熱可塑性エラストマーの重合では、ｐＨ調整剤として、リン酸塩、水酸化ナトリウム、水酸化カリウム等を好ましく用いることができる。
【００６４】
本発明によって得られるエラストマー性重合体は、固形分濃度が１０〜４０質量％、平均粒子径が０．０３〜１μｍ、好ましくは０．０５〜０．５μｍ、数平均分子量が１，０００〜２，０００，０００のものである。
【００６５】
本発明によって得られるエラストマー性重合体は、必要に応じて、炭化水素系界面活性剤等の分散安定剤の添加、濃縮等をすることにより、ゴム成形加工に適したディスパージョンにすることができる。上記ディスパージョンは、ｐＨ調節、凝固、加熱等を行い処理される。各処理は次のように行われる。
【００６６】
上記ｐＨ調節は、硝酸、硫酸、塩酸若しくはリン酸等の鉱酸、及び／又は、炭素数５以下でｐＫ＝４．２以下のカルボン酸等を加え、ｐＨを２以下とすることからなる。
上記凝固は、アルカリ土類金属塩を添加することにより行われる。上記アルカリ土類金属塩としては、カルシウム又はマグネシウムの硝酸塩、塩素酸塩及び酢酸塩が挙げられる。
上記ｐＨ調節及び上記凝固は、いずれを先に行ってもよいが、先にｐＨ調節を行うことが好ましい。
各操作の後、エラストマーと同容量の水で洗浄を行い、エラストマー内に存在する少量の緩衝液や塩等の不純物を除去し、乾燥を行う。乾燥は、通常、乾燥炉内で、高温下、空気を循環させながら、約７０〜２００℃で行われる。
【００６７】
本発明の含フッ素重合体の製造方法は、含フッ素重合体を製造するものである。上記含フッ素重合体は、通常、上記重合を行うことにより得られる水性分散液の１０〜５０質量％の濃度である。上記含フッ素重合体は、重合を上述の本発明の界面活性剤の存在下に行うので、従来の界面活性剤を用いるよりも、重合により得られる水性分散液中の含フッ素重合体からなる粒子を小粒径で得ることができる。上記水性分散液中の含フッ素重合体の濃度の好ましい下限は１０質量％、より好ましい下限は１５質量％、好ましい上限は４０質量％、より好ましい上限は３５質量％、更に好ましい上限は３０質量％である。
【００６８】
上記重合を行うことにより得られる水性分散液は、濃縮するか又は分散安定化処理してディスパージョンとしてもよいし、凝析又は凝集に供して回収し乾燥して得られる粉末その他の固形物としてもよい。本発明の含フッ素重合体の製造方法は、含フッ素重合体を製造するものであるが、製造した含フッ素重合体は、上記水性分散液中に分散されている含フッ素重合体であってもよいし、上記ディスパージョン中に分散している含フッ素重合体であってもよいし、上記粉末その他の固形物としての含フッ素重合体であってもよい。
【００６９】
上述の本発明の界面活性剤は、重合により得られた含フッ素重合体を水性媒体に分散させるための分散剤としても、好適に用いることができる。
本発明の含フッ素重合体水性分散液は、含フッ素重合体からなる粒子が上記界面活性剤の存在下に水性媒体に分散しているものである。
本発明の含フッ素重合体水性分散液は、上述した重合を行うことにより得られる水性分散液であってもよいし、この水性分散液を濃縮するか又は分散安定化処理して得られるディスパージョンであってもよいし、含フッ素重合体の粉末を本発明の界面活性剤の存在下に水性媒体に分散させたものであってもよい。
【００７０】
本発明の含フッ素重合体水性分散液における水性媒体は、水を含むものであれば特に限定されず、非フッ素含有のアルコール、エーテル、ケトン等の有機溶媒、例えば、ジメチルホルムアミド〔ＤＭＦ〕やテトラヒドロフラン〔ＴＨＦ〕等の有機溶剤、及び／又は、沸点が４０℃以下であるフッ素含有有機溶媒を含むものであってもよいし、上記有機溶剤を含まない水であってもよい。上記水性媒体は、重合における水性媒体をそのまま用いるものであってもよい。
【００７１】
本発明の含フッ素重合体水性分散液は、上述した重合を行うことにより得られる水性分散液である場合、数平均粒子径が、好ましくは約０．０５〜１μｍ、より好ましい上限は０．５μｍである含フッ素重合体からなる粒子を、好ましくは約１０〜７０質量％の濃度で含む。上記濃度のより好ましい下限は１５質量％以上、より好ましい上限は６０質量％以下である。一方、上記含フッ素重合体水性分散液は、上述のディスパージョンである場合、上記含フッ素重合体からなる粒子を、好ましくは３０〜５０質量％の濃度で含む。本明細書において、上記「数平均粒子径」は、ＰＴＦＥにおいては、得られる含フッ素重合体の固形分濃度を約０．０２質量％に希釈し、単位長さに対する５５０ｎｍの投射光の透過率と電子顕微鏡写真によって決定された平均粒子径との検量線をもとにして得られる値であり、その他の樹脂においては、電子顕微鏡写真による標準ポリスチレンに対する相対比較によって決定された平均粒子径である。
【００７２】
上述の本発明の界面活性剤は、本発明の含フッ素重合体水性分散液の０．０００１〜１５質量％であることが好ましい。０．０００１質量％未満であると、分散安定性に劣る場合があり、１５質量％を超えると、存在量に見合った分散効果がなく実用的でない。上記界面活性剤のより好ましい下限は０．０００１質量％であり、より好ましい上限は１０質量％であり、更に好ましい上限は２質量％でありある。
【００７３】
上記重合を行うことにより得られた水性分散液は、また、濃縮するか又は分散安定化処理してディスパージョンを調製することができる。
【００７４】
上記濃縮の方法としては公知の方法が採用され、用途に応じて、含フッ素重合体濃度を４０〜６０質量％に濃縮することができる。濃縮によりディスパージョンの安定性が損なわれることがあるが、その場合は更に分散安定剤を添加してもよい。上記分散安定剤としては、本発明の界面活性剤や、その他の各種の界面活性剤を添加してもよい。好ましい上記各種の分散安定剤としては、ポリオキシアルキルエーテル等の非イオン性界面活性剤、特に、ポリオキシエチレンアルキルフェニルエーテル（例えばローム＆ハース社製のトライトンＸ−１００（商品名））、ポリオキシエチレンイソトリデシルエーテル（日本油脂（株）製のディスパノールＴＯＣ（商品名））、ポリオキシエチレンプロピルトリデシルエーテル等のポリオキシエチレンエーテル類が挙げられるが、これらのみに限定されるものではない。
【００７５】
上記分散安定剤の総量は、上記ディスパージョンの固形分に対し０．５〜２０質量％であることが好ましい。０．５質量％未満であると、分散安定性に劣る場合があり、２０質量％を超えると、存在量に見合った分散効果がなく実用的でない。上記界面活性剤のより好ましい下限は２質量％であり、より好ましい上限は１２質量％である。
【００７６】
上記重合を行うことにより得られた水性分散液は、また、用途によっては濃縮せずに分散安定化処理して、ポットライフの長い含フッ素重合体水性分散液に調製することもできる。使用する分散安定剤は上記と同じものが挙げられる。
【００７７】
本発明の含フッ素重合体水性分散液の用途としては特に限定されず、水性分散液のまま適用するものとして、基材上に塗布し乾燥した後必要に応じて焼成することよりなる塗装；不織布、樹脂成形品等の多孔性支持体を含浸させ乾燥した後、好ましくは焼成することよりなる含浸；ガラス等の基材上に塗布し乾燥した後、必要に応じて水中に浸漬し、基材を剥離して薄膜を得ることよりなるキャスト製膜等が挙げられ、これら適用例としては、水性分散型塗料、電極用結着剤、電極用撥水剤等が挙げられる。
【００７８】
本発明の含フッ素重合体水性分散液は、公知の顔料、増粘剤、分散剤、消泡剤、凍結防止剤、成膜助剤等の配合剤を配合することにより、又は、更に他の高分子化合物を複合して、コーティング用水性塗料として用いることができる。
【００７９】
本発明の含フッ素重合体水性分散液の用途としては、また、含フッ素重合体水性分散液を凝析又は凝集に供して回収し、乾燥し、所望により造粒して得られる粉末を利用する用途が挙げられる。上記凝析又は凝集は、従来公知の方法をそのまま採用することができる。例えば、上記水性分散液に攪拌下で凝析剤（凝集剤）を添加して凝析（凝集）させる方法、上記水性分散液を凍結・解凍することにより凝析させる方法（凍結凝析法）、上記水性分散液を機械的に高速攪拌することのみにより凝析させる方法（機械凝析法）、細いノズルから上記水性分散液を噴出させると同時に水を蒸発させる方法（スプレー凝析法）等が好ましく採用される。要すれば、凝集助剤を添加してもよい。乾燥は室温で放置してもよいし、２５０℃までの加熱状態で乾燥させてもよい。得られる粉末は、例えば、潤滑助剤を混合しペースト押出成形等に好適な成形材料として、又は、所望により顔料を混合し粉体塗料として、用いることができる。
【００８０】
【実施例】
次に本発明を実施例に基づいて説明するが、本発明はかかる実施例のみに限定されるものではない。
【００８１】
実施例１（ＰＴＦＥラテックスの調製）
内容量３リットルの攪拌翼付きステンレススチール製オートクレーブに、脱イオン水１．５リットル、パラフィンワックスを６０ｇ（融点６０℃）、及び、Ｆ（ＣＦ_２ＣＦ_２）_２ＣＨ_２ＣＨ_２ＰＯ（ＯＮＨ_４）_２を６００ｍｇ仕込み、系内をＴＦＥで置換した。内温を７０℃にし、内圧が０．７８ＭＰａになるように、ＴＦＥを圧入し、０．６重量％の過硫酸アンモニウム（ＡＰＳ）水溶液５ｇを仕込み、反応を開始した。重合の進行に伴って重合系内の圧力が低下するので、連続的にＴＦＥを追加して、内圧を０．７８ＭＰａに保ち、反応を継続した。重合開始４時間後にＴＦＥをパージして重合を停止した。この水性分散体について以下の項目を測定した。結果を表１に示す。
【００８２】
固形分濃度：得られた水性分散液を１５０℃で１時間乾燥した時の重量減少より求めた。
標準比重（ＳＳＧ）：ＡＳＴＭ Ｄ１４５７−６９に従い測定した。
平均一次粒子径：固形分濃度を約０．０２重量％に希釈し、単位長さに対する５５０ｎｍの投射光の透過率と電子顕微鏡写真によって決定された平均粒子径との検量線をもとにして、上記透過率から間接的に求めた。
粒子形状：約０．０２重量％に希釈した水性分散液の透過型電子顕微鏡写真より、棒状粒子の生成の有無を確認した。
【００８３】
実施例２
表１に示すように、界面活性剤１（Ｆ（ＣＦ_２ＣＦ_２）_２ＣＨ_２ＣＨ_２ＰＯ（ＯＮＨ_４）_２）の添加量を変更し、実施例１と同様の測定を行った。結果を表１に示す。
【００８４】
比較例１
界面活性剤１（Ｆ（ＣＦ_２ＣＦ_２）_２ＣＨ_２ＣＨ_２ＰＯ（ＯＮＨ_４）_２）の代わりに、界面活性剤２（Ｆ（ＣＦ_２ＣＦ_２）_３ＣＦ_２ＣＯＯＮＨ_４）を使用し、反応圧力を２．７ＭＰａに変更した以外は、実施例１と同様の測定を行った。結果を表１に示す。
【００８５】
【表１】

【００８６】
表１から、Ｆ（ＣＦ_２ＣＦ_２）_２ＣＨ_２ＣＨ_２ＰＯ（ＯＮＨ_４）_２を用いた実施例１〜２では、Ｆ（ＣＦ_２ＣＦ_２）_３ＣＦ_２ＣＯＯＮＨ_４を用いた比較例１よりも一次粒子径が小さく、また、棒状粒子は得られないことが分かった。
【００８７】
【発明の効果】
本発明の界面活性剤は、水性媒体中で重合を行うことにより含フッ素重合体を得るに際して水性媒体に存在させる分散剤として好適であり、重合により得られる水性分散液中の含フッ素重合体からなる粒子を、従来の界面活性剤を用いる場合よりも小粒径で得ることができる。上記重合により得られる水性分散液は、ポリマーディスパージョンとして使用する場合、ガラスクロス等の基材に従来のポリマーディスパージョンよりも均一に含浸させることができるので、一回の工程におけるポリマー塗布量を多くすることができる点で有利である。また、上記重合により得られる水性分散液は、後処理を行い樹脂の粉末として使用する場合、成形加工における焼成時間を短くできるので有利である。本発明の界面活性剤を用いて得た含フッ素重合体からなる粒子は、真球度が高いので、分散性が高く、成形性が良好である点で有利である。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a surfactant, a method for producing a fluoropolymer, and an aqueous dispersion of a fluoropolymer.
[0002]
[Prior art]
Examples of the phosphoric acid compound having a fluorine atom include Rf (C_nH_2n) PO (OH)₂(Rf is a perfluoroalkyl group, n is an integer, and R is H or a lower alkyl group) is disclosed (for example, see Patent Document 1). This compound is used as a raw material such as a water and oil repellent and a release agent.
[0003]
Examples of the phosphoric acid compound having a fluorine atom include C_mF_{2m + 1}(CH₂)_nPO (OH)₂(Where m and n are integers) and salts thereof such as ammonia are disclosed (for example, see Patent Document 2). This compound is used as a release agent.
[0004]
Some compounds in which a lipophilic group is bonded to an acid such as a carboxylic acid have been proposed for use as an emulsifier to be added at the time of polymerization to obtain a fluoropolymer, and conventionally, ammonium perfluorooctanoate has been proposed. Has been widely used.
[0005]
As an emulsifier, Rf (OX₂)_n-P (= Q) Y₂(Rf is a perfluoroalkyl group having 6 or more carbon atoms, preferably 8 to 20, X is H or an aliphatic alkyl group, Y is OH or the like, n is 2 to 7, Q is O or S.) A salt is disclosed (for example, see Patent Document 3).
[0006]
However, since these emulsifiers have a large particle size of the fluoropolymer particles in the aqueous dispersion obtained by polymerization, the dispersion stability is poor, or the particles of the fluoropolymer are recovered and molded. There were problems such as inferior physical properties of a molded article obtained when used as a material.
[0007]
[Patent Document 1]
JP-A-58-210096 (Claim 1, page 5)
[Patent Document 2]
JP-A-58-180597 (Claim 1)
[Patent Document 3]
JP-B-43-4503 (page 1)
[0008]
[Problems to be solved by the invention]
An object of the present invention is to provide a surfactant in which particles made of a fluorinated polymer are obtained with a small particle size by being present during polymerization in view of the above situation.
[0009]
[Means for Solving the Problems]
The present invention provides the following general formula (i)
Rf- (CH₂)_n-PO (OM)₂                (I)
(Where M is NH₄, Li, Na, K or H. n represents an integer of 1 to 3. Rf represents an alkyl group having at least one fluorine atom and having 1 to 6 carbon atoms. ) Is a surfactant comprising a fluorine-containing phosphoric acid derivative represented by the formula (1).
[0010]
The present invention is a process for producing a fluoropolymer, comprising obtaining a fluoropolymer by carrying out polymerization in an aqueous medium in the presence of the surfactant.
The present invention is an aqueous dispersion of a fluoropolymer, in which particles comprising the fluoropolymer are dispersed in an aqueous medium in the presence of the surfactant.
Hereinafter, the present invention will be described in detail.
[0011]
The surfactant of the present invention is suitable as a dispersant to be present in an aqueous medium when a fluoropolymer is obtained by performing polymerization in an aqueous medium, and from a fluoropolymer in an aqueous dispersion obtained by polymerization. Can be obtained with a smaller particle size than when a conventional surfactant is used.
[0012]
In the present specification, the above-mentioned "aqueous dispersion liquid" is one in which particles made of a fluoropolymer obtained by radical polymerization are dispersed in an aqueous medium. The aqueous dispersion may be one in which the concentration of the fluoropolymer contained in the aqueous dispersion is substantially changed by, for example, performing operations such as dilution and concentration in the presence of the surfactant of the present invention. By the operation such as the concentration, the particles (primary particles) made of the fluoropolymer in the aqueous dispersion may aggregate to form particles (secondary particles) having an increased particle diameter. In the present specification, the particle size of the particles made of the fluoropolymer in the aqueous dispersion is the particle size of the primary particles.
[0013]
In the present specification, the “fluorinated polymer” is a polymer having a fluorine atom bonded to a carbon atom. In the present invention, the above-mentioned fluorine-containing polymer is obtained by polymerizing one or more kinds of fluorine-containing monomers, but also includes a non-fluorine-based monomer having no fluorine atom. It may be obtained by polymerization. The “fluorine-containing monomer” is a monomer having at least one fluorine atom bonded to a carbon atom. The above-mentioned fluoropolymer will be described later.
[0014]
Regarding the surfactant of the present invention and the method for producing a fluoropolymer of the present invention described below, the “aqueous medium” is a reaction medium for performing polymerization, and means a liquid containing water. The aqueous medium is not particularly limited as long as it contains water. Water and a fluorine-free organic solvent such as, for example, alcohols, ethers and ketones, and / or a fluorine-containing organic solvent having a boiling point of 40 ° C. or lower May be included. For example, when performing suspension polymerization, a fluorine-containing organic solvent such as C318 can be used.
[0015]
The surfactant of the present invention comprises the fluorinated phosphoric acid derivative represented by the general formula (i). By the above-mentioned fluorinated phosphoric acid derivative, particles made of a fluorinated polymer in an aqueous dispersion obtained by polymerization can be obtained with a smaller particle size than when a conventional surfactant is used.
In the above general formula (i), M is NH₄, Li, Na, K or H.
As M, NH can be easily removed from the produced fluoropolymer by heat treatment,₄Are preferable, and Li, Na, and K are preferable in terms of emulsifying power and dispersing power.
[0016]
In the above general formula (i), n represents an integer of 1 to 3. If it exceeds 3, the chain transfer property becomes high during the polymerization, and a high molecular weight fluoropolymer cannot be obtained. n is preferably an integer of 2 from the viewpoint of emulsifying power.
[0017]
In the general formula (i), Rf represents an alkyl group having 1 or more carbon atoms and having 1 to 6 carbon atoms.
The preferable upper limit of the number of carbon atoms of the alkyl group having one or more fluorine atoms is 5, the more preferable upper limit is 4, and the further preferable number of carbon atoms of the alkyl group is 4. As the alkyl group having one or more fluorine atoms, the number of fluorine atoms [n_F] And the number of hydrogen atoms [n_H] [N]_F/ (N_F+ N_H)] Is preferably 0.5 or more, more preferably 1, that is, a perfluoroalkyl group.
As the Rf, a perfluoroalkyl group having 1 to 4 carbon atoms is preferable.₄F₉-Is more preferable.
[0018]
As the above-mentioned fluorinated phosphoric acid derivative, C particles are preferred because they can easily reduce the particle size of the fluorinated polymer in the obtained aqueous dispersion.₄F₉-C₂H₄-PO (ONH₄)₂Is preferred.
[0019]
Examples of the method for producing the above fluorine-containing phosphoric acid derivative include a method described in JP-A-58-180597.
[0020]
When the fluorine-containing phosphoric acid derivative is present in the polymerization for obtaining the fluorine-containing polymer, a good balance between the affinity to the fluorine-containing polymer and the fluorine-containing monomer and the affinity to the aqueous medium is obtained. Therefore, it is possible not only to have an excellent action as a dispersant, but also to obtain particles of a fluoropolymer dispersed in an aqueous dispersant obtained by polymerization with a small particle size.
[0021]
The surfactant of the present invention may contain one or more of the above-mentioned fluorine-containing phosphoric acid derivatives.
The surfactant of the present invention is preferably one containing the above-mentioned fluorinated phosphoric acid derivative as a main component. Although it functions sufficiently as a dispersant, it may contain, if desired, a compound having another surfactant activity in addition to the above fluorine-containing phosphoric acid derivative.
[0022]
The compound having the other surfactant activity is not particularly limited, and may be, for example, any of anionic, cationic, nonionic, and betaine surfactants. System.
[0023]
The surfactant of the present invention may contain an additive in addition to the above-mentioned fluorinated phosphoric acid derivative and other optional compounds having a surfactant activity. The additives are not particularly limited, and may be, for example, those usually used for general surfactants such as stabilizers.
[0024]
The surfactant of the present invention can be suitably used as a surfactant for polymerization for obtaining a fluoropolymer, and as a dispersant for dispersing the fluoropolymer obtained by polymerization in an aqueous medium. Can also be suitably used. The surfactant of the present invention, even when used as a dispersant for dispersing the fluoropolymer in the aqueous medium, similarly to the case where the surfactant is used as the above-described polymerization surfactant, the fluorophosphate derivative Has a good balance between the affinity for the fluoropolymer and the affinity for the aqueous medium, so that excellent dispersing power can be exhibited.
[0025]
In the method for producing a fluoropolymer of the present invention, a fluoropolymer is obtained by performing polymerization in an aqueous medium in the presence of the surfactant of the present invention.
In the above fluoropolymer production method, the fluorophosphoric acid derivative functions as a dispersant.
[0026]
The method for producing a fluoropolymer of the present invention is for obtaining a fluoropolymer.
The method for polymerizing a fluorine-containing polymer of the present invention is a normal method except that the above-mentioned fluorine-containing phosphoric acid derivative is used as a dispersant for the polymerization of a fluorine-containing monomer.
In the method for producing a fluoropolymer of the present invention, polymerization is carried out by charging water, a surfactant of the present invention, a monomer, and other additives as necessary in a polymerization reactor, and charging the contents of the reactor. Stirring is performed by maintaining the reactor at a predetermined polymerization temperature and then adding a predetermined amount of a polymerization initiator to start a polymerization reaction. After the start of the polymerization reaction, a monomer, an initiator, a chain transfer agent and a surfactant may be additionally added according to the purpose.
In the above polymerization, the polymerization temperature is usually 5 to 120 ° C., and the polymerization pressure is 0.05 to 10 MPaG. The polymerization temperature and polymerization pressure are appropriately determined depending on the type of the monomer used, the molecular weight of the target polymer, and the reaction rate.
[0027]
In the method for producing a fluoropolymer of the present invention, a fluoropolymer is produced by performing polymerization in an aqueous medium in the presence of the surfactant of the present invention.
The polymerization method in the method for producing a fluoropolymer of the present invention is a normal method except that the above-mentioned surfactant of the present invention is used as a dispersant when polymerizing a fluorine-containing monomer.
In the method for producing a fluoropolymer of the present invention, polymerization is carried out in a polymerization reactor, water, a surfactant, a monomer and other additives as necessary, stirring the contents of the reactor, The reaction is carried out by maintaining the reactor at a predetermined polymerization temperature and then adding a predetermined amount of a polymerization initiator to start a polymerization reaction. After the start of the polymerization reaction, a monomer, an initiator, a chain transfer agent and a surfactant may be additionally added according to the purpose.
In the above polymerization, the polymerization temperature is usually 5 to 120 ° C., and the polymerization pressure is 0.05 to 10 MPaG. The polymerization temperature and polymerization pressure are appropriately determined depending on the type of the monomer used, the molecular weight of the target polymer, and the reaction rate.
The surfactant is preferably added in a total amount of 0.0001 to 15% by mass of the aqueous medium, more preferably 0.001% by mass and more preferably 10% by mass. Yes, and a more preferred upper limit is 1% by mass. If the amount is less than 0.0001% by mass, the dispersing power tends to be insufficient. The amount of the surfactant to be added is appropriately determined depending on the type of the monomer used, the molecular weight of the target polymer, and the like.
In the above production method, other surfactants may be used as long as the surfactant of the present invention is used.
[0028]
The polymerization initiator is not particularly limited as long as it can generate a radical in the above-mentioned polymerization temperature range, and a known oil-soluble and / or water-soluble polymerization initiator can be used. Further, the polymerization can be started as redox in combination with a reducing agent or the like. The concentration of the polymerization initiator is appropriately determined depending on the type of the monomer, the molecular weight of the target polymer, and the reaction rate.
In the above polymerization, a known chain transfer agent and a radical scavenger may be further added to adjust the polymerization rate and the molecular weight according to the purpose.
[0029]
The fluorine-containing polymer is obtained by polymerizing a fluorine-containing monomer, and a fluorine-free monomer can also be copolymerized according to the purpose.
[0030]
Examples of the fluorine-containing monomer include a fluoroolefin, preferably a fluoroolefin having 2 to 10 carbon atoms; a cyclic fluorinated monomer;₂= CYOR or CY₂= CYOR¹OR (Y is H or F, R is an alkyl group having 1 to 8 carbon atoms in which some or all of the hydrogen atoms are substituted with fluorine atoms,¹Is an alkylene group having 1 to 8 carbon atoms in which some or all of the hydrogen atoms are substituted with fluorine atoms. )) And the like.
[0031]
The fluoroolefin preferably has 2 to 6 carbon atoms. Examples of the fluoroolefin having 2 to 6 carbon atoms include, for example, tetrafluoroethylene [TFE], hexafluoropropylene [HFP], chlorotrifluoroethylene [CTFE], vinyl fluoride, vinylidene fluoride [VDF], and trifluoroethylene [VDF]. Fluoroethylene, hexafluoroisobutylene, perfluorobutylethylene, and the like. As the cyclic fluorinated monomer, preferably, perfluoro-2,2-dimethyl-1,3-dioxole [PDD], perfluoro-2-methylene-4-methyl-1,3- Dioxolane [PMD] and the like. In the above fluorinated alkyl vinyl ether, the above R is preferably one having 1 to 4 carbon atoms, more preferably one in which all of the hydrogen atoms are substituted by fluorine.¹Is preferably those having 2 to 4 carbon atoms, and more preferably all of the hydrogen atoms are replaced by fluorine atoms.
[0032]
Examples of the fluorine-free monomer include a hydrocarbon monomer having reactivity with the fluorine-containing monomer. Examples of the hydrocarbon monomer include alkenes such as ethylene, propylene, butylene and isobutylene; alkyl vinyl ethers such as ethyl vinyl ether, propyl vinyl ether, butyl vinyl ether, isobutyl vinyl ether and cyclohexyl vinyl ether; vinyl acetate and vinyl propionate , N-vinyl butyrate, vinyl isobutyrate, vinyl valerate, vinyl pivalate, vinyl caproate, vinyl caprylate, vinyl caprate, vinyl versatate, vinyl laurate, vinyl myristate, vinyl palmitate, vinyl stearate, Vinyl benzoate, vinyl para-t-butyl benzoate, vinyl cyclohexanecarboxylate, vinyl monochloroacetate, vinyl adipate, vinyl acrylate, vinyl methacrylate, croton Vinyl esters such as vinyl, vinyl sorbate, vinyl cinnamate, vinyl undecylenate, vinyl hydroxyacetate, vinyl hydroxypropioate, vinyl hydroxybutyrate, vinyl hydroxyvalerate, vinyl hydroxyisobutyrate, vinyl hydroxycyclohexanecarboxylate; Alkyl allyl ethers such as ethyl allyl ether, propyl allyl ether, butyl allyl ether, isobutyl allyl ether, cyclohexyl allyl ether; alkyl allyl esters such as ethyl allyl ester, propyl allyl ester, butyl allyl ester, isobutyl allyl ester, cyclohexyl allyl ester And the like.
[0033]
The fluorine-free monomer may also be a functional group-containing hydrocarbon monomer. Examples of the functional group-containing hydrocarbon monomer include hydroxyalkyl vinyl ethers such as hydroxyethyl vinyl ether, hydroxypropyl vinyl ether, hydroxybutyl vinyl ether, hydroxyisobutyl vinyl ether, and hydroxycyclohexyl vinyl ether; itaconic acid, succinic acid, and succinic anhydride Fluorine-free monomers having a carboxyl group such as, fumaric acid, fumaric anhydride, crotonic acid, maleic acid, maleic anhydride, perfluorobutenoic acid, etc .; fluorine-free monomers having a glycidyl group such as glycidyl vinyl ether and glycidyl allyl ether Monomer; non-fluorine-containing monomer having an amino group such as aminoalkyl vinyl ether and aminoalkyl allyl ether; (meth) acrylamide, methylolacrylamide Include fluorine-free monomer having a amide group is.
[0034]
As the fluoropolymer suitably produced by the production method of the present invention, a TFE polymer in which the monomer having the largest mole fraction of the monomer in the polymer (hereinafter, “most common monomer”) is TFE And a VDF polymer whose most monomer is VDF, and a CTFE polymer whose most monomer is CTFE.
[0035]
The TFE polymer may be preferably a TFE homopolymer, or (1) TFE, or (2) one or more fluorine-containing monomers other than one or more TFE having 2 to 8 carbon atoms. It may be a copolymer composed of a monomer, particularly HFP or CTFE, and (3) another monomer. Examples of the above (3) other monomers include, for example, fluoro (alkyl vinyl ether) having an alkyl group having 1 to 5 carbon atoms, particularly 1 to 3 carbon atoms; fluorodioxole; perfluoroalkylethylene; ω-hydroperfluoroolefin and the like.
The TFE polymer may also be a copolymer of TFE and one or more fluorine-free monomers. Examples of the fluorine-free monomer include alkenes such as ethylene and propylene; vinyl esters; and vinyl ethers. The TFE polymer also includes a copolymer of TFE, one or more fluorine-containing monomers having 2 to 8 carbon atoms, and one or more fluorine-free monomers. It may be united.
[0036]
The VDF polymer may suitably be a VDF homopolymer [PVDF], or (1) VDF, (2) one or more than two or more VDFs having 2 to 8 carbon atoms. A copolymer comprising a fluoroolefin, particularly TFE, HFP or CTFE, and (3) a perfluoro (alkyl vinyl ether) having an alkyl group having 1 to 5 carbon atoms, particularly 1 to 3 carbon atoms, and the like. Is also good.
[0037]
Preferably, the CTFE polymer may be a CTFE homopolymer, or (1) CTFE, (2) one or more fluoroolefins other than CTFE having 2 to 8 carbon atoms, In particular, it may be a copolymer of TFE or HFP and (3) a perfluoro (alkyl vinyl ether) having an alkyl group having 1 to 5 carbon atoms, particularly 1 to 3 carbon atoms.
The CTFE polymer may be a copolymer of CTFE and one or more fluorine-free monomers. Examples of the fluorine-free monomer include ethylene and propylene. Alkenes; vinyl esters; vinyl ethers.
[0038]
The fluoropolymer produced by the production method of the present invention may be glassy, plastic or elastomeric. These are amorphous or partially crystalline and can be subjected to compression firing, melt processing or non-melt processing.
In the production method of the present invention, for example, (I) a polytetrafluoroethylene polymer [PTFE polymer] as a non-melt-processable resin, and (II) an ethylene / TFE copolymer [ETFE] as a melt-processable resin. , TFE / HFP copolymer [FEP] and TFE / perfluoro (alkyl vinyl ether) copolymer [PFA, MFA, etc.] are (III) elastomeric copolymers as TFE / propylene copolymer, TFE / propylene Copolymer / third monomer copolymer (the third monomer is VDF, HFP, CTFE, perfluoro (alkyl vinyl ether), etc.), a copolymer composed of TFE and perfluoro (alkyl vinyl ether); HFP / Ethylene copolymer, HFP / ethylene / TFE copolymer; PVDF; VDF / HFP copolymer HFP / ethylene copolymer, a thermoplastic elastomer of VDF / TFE / HFP copolymers and the like; and, the fluorine-containing segmented polymer or the like can be suitably produced according to JP-B-61-49327.
The perfluoro (alkyl vinyl ether) has the formula:
[0039]
Embedded image

[0040]
(Where Rf⁴Is a perfluoroalkyl group having 1 to 6 carbon atoms; j is an integer of 0 to 5).
[0041]
The above-mentioned (I) non-melt-processable resin, (II) melt-processable resin, and (III) elastomeric polymer suitably produced by the production method of the present invention are preferably produced in the following manner.
[0042]
(I) Non-melt processable resin
In the production method of the present invention, the polymerization of the PTFE polymer is usually performed at a polymerization temperature of 10 to 100 ° C and a polymerization pressure of 0.05 to 5 MPaG.
In the above polymerization, after deoxygenating a pressure-resistant reaction vessel equipped with a stirrer, TFE is charged, the temperature is raised to a predetermined temperature, and a polymerization initiator is added to start the reaction. As the pressure decreases with the progress of the reaction, additional TFE is continuously or intermittently supplied so as to maintain the initial pressure. When a predetermined amount of TFE is supplied, the supply is stopped, TFE in the reaction vessel is purged, and the temperature is returned to room temperature to terminate the reaction.
[0043]
In the production of the PTFE polymer, various known modified monomers may be used in combination. In the present specification, the polytetrafluoroethylene polymer [PTFE polymer] is not only a TFE homopolymer but also a copolymer of TFE and a modified monomer, which is non-melt-processable (hereinafter, referred to as “ "Modified PTFE").
Examples of the modified monomer include perhaloolefins such as HFP and CTFE; fluoro (alkyl vinyl ether) having an alkyl group having 1 to 5 carbon atoms, especially 1 to 3 carbon atoms; and rings such as fluorodioxole Fluorinated monomers of the formula; perhaloalkylethylene; ω-hydroperhaloolefins and the like. Depending on the purpose and supply of TFE, the supply of the modified monomer can be carried out in an initial batch or in a continuous or intermittent manner.
The modified monomer content in the modified PTFE is usually in the range of 0.001 to 2 mol%.
[0044]
In the production of the PTFE polymer, the surfactant of the present invention described above can be used in the range of use in the method for producing the fluoropolymer of the present invention, but is usually 0.0001 to 5% by mass of the aqueous medium. Add the% amount. The concentration of the surfactant is not particularly limited as long as it is within the above range, but is usually added at the start of polymerization at a critical micelle concentration (CMC) or less. If the amount of addition is large, needle-like particles having a large aspect ratio are generated, and the aqueous dispersion becomes gel-like, thus impairing stability.
[0045]
In the production of the PTFE polymer, as a polymerization initiator, an organic peroxide such as persulfate (for example, ammonium persulfate) or disuccinic peroxide or diglutaric peroxide is used alone or in the form of a mixture thereof. can do. It may be used in combination with a reducing agent such as sodium sulfite to form a redox system. Furthermore, during polymerization, a radical scavenger such as hydroquinone or catechol or a peroxide decomposer such as ammonium sulfite may be added to adjust the radical concentration in the system.
[0046]
In the production of the PTFE polymer, known chain transfer agents can be used. Examples of the chain transfer agent include saturated hydrocarbons such as methane, ethane, propane, and butane; and halogenated hydrocarbons such as chloromethane, dichloromethane, and difluoroethane. And alcohols such as methanol and ethanol, hydrogen and the like, but those in a gaseous state at normal temperature and normal pressure are preferable.
The amount of the chain transfer agent to be used is generally 1 to 1000 ppm, preferably 1 to 500 ppm, based on the total amount of TFE to be supplied.
[0047]
In the production of the PTFE polymer, a saturated hydrocarbon having 12 or more carbon atoms, which is substantially inert to the reaction and becomes liquid under the above reaction conditions, is further added as a dispersion stabilizer of the reaction system to the aqueous medium 100. 2 to 10 parts by mass can be used per part by mass. Further, as a buffer for adjusting the pH during the reaction, ammonium carbonate, ammonium phosphate or the like may be added.
[0048]
When the polymerization is completed, the aqueous dispersion of the PTFE polymer obtained by the present invention has a solid content of 10 to 40% by mass, an average particle size of 0.05 to 5000 μm, and particularly uses the surfactant of the present invention. By doing so, an aqueous dispersion having particles made of a PTFE polymer having a fine particle diameter of 0.2 μm or less can be obtained. The PTFE polymer at the end of the polymerization has a number average molecular weight of 1,000 to 10,000,000.
[0049]
The aqueous dispersion of the PTFE polymer can be used for various applications as a fine powder after coagulation and drying.
When coagulation is performed on the aqueous dispersion of the PTFE polymer, the aqueous dispersion obtained by emulsion polymerization of a polymer latex or the like is usually diluted with water to a polymer concentration of 10 to 20% by mass. In some cases, after the pH is adjusted to neutral or alkaline, the reaction is carried out in a vessel equipped with a stirrer by stirring more vigorously than during the reaction. The coagulation may be carried out while adding a water-soluble organic compound such as methanol or acetone, an inorganic salt such as potassium nitrate or ammonium carbonate, or an inorganic acid such as hydrochloric acid, sulfuric acid or nitric acid as a coagulant. The coagulation may be continuously performed using an in-line mixer or the like.
[0050]
Before or during the coagulation, a pigment for coloring and various fillers for improving mechanical properties can be added, so that the pigment or the filler-containing PTFE layer containing the pigment or the filler is uniformly mixed. A combined fine powder can be obtained.
[0051]
Drying of the wet powder obtained by coagulation of the aqueous dispersion of the PTFE polymer is usually carried out under vacuum, high frequency, hot air or the like while keeping the wet powder in a state where it does not flow much, preferably in a stationary state. This is performed using a means. Friction between the powders, especially at high temperatures, generally has an undesirable effect on fine powder type PTFE polymers. This is because particles made of this kind of PTFE polymer have the property of easily fibrillating even with a small shear force and losing the original stable particle structure.
[0052]
The drying is performed at a drying temperature of 10 to 250C, preferably 100 to 200C. The obtained PTFE polymer fine powder is preferably used for molding, and suitable applications include hydraulic and fuel tubes for aircraft and automobiles, and flexible hoses for chemicals, steam, etc., and wire coating applications. No.
[0053]
The aqueous dispersion of the PTFE polymer obtained by the above polymerization is also stabilized by adding a nonionic surfactant, and further concentrated, and according to the purpose, as a composition to which an organic or inorganic filler is added. It is also preferable to use it for various purposes. The above composition has a non-adhesive property and a low friction coefficient by being coated on a substrate made of metal or ceramics, and has a surface of a coating film excellent in gloss, smoothness, abrasion resistance, weather resistance and heat resistance. It is suitable for coating rolls and cooking utensils, impregnating glass cloth, and the like.
[0054]
(II) Melt-processable resin
(1) In the production method of the present invention, the FEP polymerization is preferably performed usually at a polymerization temperature of 60 to 100 ° C. and a polymerization pressure of 0.7 to 4.5 MpaG.
The preferred monomer composition (% by mass) of FEP is TFE: HFP = (60-95) :( 5-40), more preferably (85-90) :( 10-15). The above-mentioned FEP may be further modified by using perfluoro (alkyl vinyl ether) s as the third component within a range of 0.5 to 2% by mass of all monomers.
In the above-mentioned polymerization of FEP, the above-mentioned surfactant of the present invention can be used within the range of use in the production method of the present invention, and usually, an amount of 0.0001 to 5% by mass of the aqueous medium is added.
In the above FEP polymerization, it is preferable to use cyclohexane, methanol, ethanol, carbon tetrachloride, chloroform, methylene chloride, methyl chloride, and the like as the chain transfer agent, and ammonium carbonate, disodium hydrogen phosphate as the pH buffer. And the like.
[0055]
(2) In the production method of the present invention, the polymerization of TFE / perfluoro (alkyl vinyl ether) copolymer such as PFA and MFA is usually performed at a polymerization temperature of 60 to 100 ° C. and a polymerization pressure of 0.7 to 2.5 MpaG. Is preferred.
The preferred monomer composition (mol%) of PFA is TFE: perfluoro (alkyl vinyl ether) = (95-99.7) :( 0.3-5), more preferably (98-99.5) :( 0.5-2). As perfluoro (alkyl vinyl ether), a compound represented by the formula: CF₂= CFORf (wherein, Rf is a perfluoroalkyl group having 1 to 6 carbon atoms) is preferably used.
In the polymerization of the TFE / perfluoro (alkyl vinyl ether) copolymer, the above-mentioned surfactant of the present invention can be used within the range of use in the production method of the present invention. It is added in an amount of 2% by weight.
In the polymerization of the TFE / perfluoro (alkyl vinyl ether) copolymer, it is preferable to use cyclohexane, methanol, ethanol, carbon tetrachloride, chloroform, methylene chloride, methyl chloride, methane, ethane or the like as a chain transfer agent. As a buffer, it is preferable to use ammonium carbonate, disodium hydrogen phosphate and the like.
[0056]
(3) In the production method of the present invention, the polymerization of ETFE is usually preferably performed at a polymerization temperature of 20 to 100 ° C. and a polymerization pressure of 0.5 to 0.8 MPaG.
The preferred monomer composition (mol%) of ETFE is TFE: ethylene = (50-99) :( 50-1). The above-mentioned ETFE may be further modified using a third monomer within a range of 0 to 20% by mass of all the monomers. Preferably, TFE: ethylene: third monomer = (70-98) :( 30-2) :( 4-10). As the third monomer, perfluorobutylethylene, 2,3,3,4,4,5,5-heptafluoro-1-pentene (CH₂= CFCF₂CF₂CF₂H), 2-trifluoromethyl-3,3,3-trifluoropropene ((CF₃)₂C = CH₂Is preferred.
In the above-mentioned polymerization of ETFE, the above-mentioned surfactant of the present invention can be used in the range of use in the production method of the present invention, but is usually added in an amount of 0.0001 to 2% by mass of the aqueous medium.
In the polymerization of ETFE, it is preferable to use cyclohexane, methanol, ethanol, carbon tetrachloride, chloroform, methylene chloride, methyl chloride and the like as a chain transfer agent.
[0057]
(III) Elastomer polymer
In the production method of the present invention, the polymerization of the elastomeric polymer is carried out by deoxidizing a pressure-resistant reaction vessel equipped with a stirrer, charging a monomer, bringing the monomer to a predetermined temperature, adding a polymerization initiator, and starting the reaction. . As the pressure decreases as the reaction proceeds, additional monomer is continuously or intermittently supplied so as to maintain the initial pressure. When a predetermined amount of monomer is supplied, the supply is stopped, the monomer in the reaction vessel is purged, and the temperature is returned to room temperature to terminate the reaction. In the case of emulsion polymerization, it is preferred that the polymer latex be continuously taken out of the reaction vessel.
In particular, when a thermoplastic elastomer is produced, as disclosed in WO 00/01741, ordinary synthesis is performed by synthesizing polymer fine particles at a high surfactant concentration and then diluting and further polymerizing. It is also possible to use a method capable of increasing the final polymerization rate as compared with the polymerization.
[0058]
The polymerization of the elastomeric polymer is appropriately selected from the viewpoints of physical properties of the target polymer and control of the polymerization rate, but the polymerization temperature is usually -20 to 200 ° C, preferably 5 to 150 ° C, and the polymerization pressure is usually The reaction is performed at 0.5 to 10 MPaG, preferably 1 to 7 MPaG. Further, it is preferable that the pH in the polymerization medium is generally maintained at 2.5 to 9 by a known method or the like using a pH adjuster described later.
[0059]
As the monomer used for the polymerization of the elastomeric polymer, in addition to vinylidene fluoride, a fluorine-containing ethylenically unsaturated monomer having at least the same number of fluorine atoms as carbon atoms and copolymerizable with vinylidene fluoride Is mentioned. Examples of the fluorine-containing ethylenically unsaturated monomer include trifluoropropene, pentafluoropropene, hexafluorobutene, and octafluorobutene. Among them, hexafluoropropene is particularly preferred because of the properties of the elastomer obtained when it blocks the crystal growth of the polymer. Examples of the fluorine-containing ethylenically unsaturated monomer include trifluoroethylene, TFE and CTFE, etc., and a fluorine-containing monomer having one or more chlorine and / or bromine substituents. Can also be used. Perfluoro (alkyl vinyl ether), such as perfluoro (methyl vinyl ether), can also be used. TFE and HFP are preferred for producing elastomeric polymers.
The preferred monomer composition (% by mass) of the elastomeric polymer is vinylidene fluoride: HFP: TFE = (20-70) :( 20-60) :( 0-40). Elastomeric polymers of this composition exhibit good elastomeric properties, chemical resistance, and thermal stability.
[0060]
In the polymerization of the elastomeric polymer, the above-mentioned surfactant of the present invention can be used within the range of use in the production method of the present invention, but is usually used in an amount of 0.0001 to 5% by mass based on the aqueous medium. Add in.
[0061]
In the polymerization of the elastomeric polymer, a known inorganic radical polymerization initiator can be used as a polymerization initiator. As the inorganic radical polymerization initiator, conventionally known water-soluble inorganic peroxides, for example, sodium, potassium and ammonium persulfates, perphosphates, perborates, percarbonates or permanganates are particularly preferred. Useful. The radical polymerization initiator may further include a reducing agent such as sodium, potassium or ammonium sulfite, bisulfite, metabisulfite, hyposulfite, thiosulfate, phosphite or hypophosphite. Or by a readily oxidizable metal compound such as a ferrous, cuprous or silver salt. A preferred radical polymerization initiator is ammonium persulfate, more preferably used in a redox system with ammonium persulfate and sodium bisulfite.
The concentration of the polymerization initiator to be added is appropriately determined depending on the molecular weight of the target polymer and the polymerization reaction rate, but is preferably 0.0001 to 10% by mass, preferably 0.01 to 5% by mass of the total amount of the monomers. Set.
[0062]
In the polymerization of the elastomeric polymer, any known chain transfer agent can be used, but in the polymerization of PVDF, hydrocarbons, esters, ethers, alcohols, ketones, chlorine compounds, carbonates, and the like are used. As the thermoplastic elastomer, hydrocarbons, esters, ethers, alcohols, chlorine compounds, iodine compounds and the like can be used. Among them, acetone and isopropyl alcohol are preferred in the polymerization of PVDF, and isopentane, diethyl malonate and ethyl acetate are preferred in the polymerization of thermoplastic elastomer from the viewpoint that the reaction rate is hardly reduced, and I (CF₂)₄I, I (CF₂)₆I, ICH₂A diiodine compound such as I is preferable from the viewpoint that a polymer terminal can be iodinated and can be used as a reactive polymer.
The amount of the chain transfer agent used is usually 0.5 × 10^-3~ 5 × 10^-3Mol%, preferably 1.0 × 10^-3~ 3.5 × 10^-3Mol%.
[0063]
In the polymerization of the elastomeric polymer, paraffin wax or the like can be preferably used as an emulsion stabilizer in the polymerization of PVDF. In the polymerization of a thermoplastic elastomer, phosphate, sodium hydroxide, or hydroxide is used as a pH adjuster. Potassium and the like can be preferably used.
[0064]
The elastomeric polymer obtained by the present invention has a solid content of 10 to 40% by mass, an average particle diameter of 0.03 to 1 μm, preferably 0.05 to 0.5 μm, and a number average molecular weight of 1,000 to 2 1,000,000.
[0065]
The elastomeric polymer obtained by the present invention can be made into a dispersion suitable for rubber molding by adding and concentrating a dispersion stabilizer such as a hydrocarbon-based surfactant, if necessary. . The dispersion is processed by adjusting pH, coagulating, heating and the like. Each process is performed as follows.
[0066]
The pH adjustment comprises adding a mineral acid such as nitric acid, sulfuric acid, hydrochloric acid, or phosphoric acid, and / or a carboxylic acid having 5 or less carbon atoms and a pK of 4.2 or less to adjust the pH to 2 or less.
The coagulation is performed by adding an alkaline earth metal salt. Examples of the alkaline earth metal salts include nitrates, chlorates and acetates of calcium or magnesium.
Either the pH adjustment or the coagulation may be performed first, but it is preferable to perform the pH adjustment first.
After each operation, washing is carried out with the same volume of water as the elastomer to remove a small amount of impurities such as buffers and salts present in the elastomer, followed by drying. Drying is usually performed in a drying oven at a high temperature of about 70 to 200 ° C. while circulating air.
[0067]
The method for producing a fluoropolymer of the present invention produces a fluoropolymer. The concentration of the above-mentioned fluoropolymer is usually 10 to 50% by mass of the aqueous dispersion obtained by carrying out the above-mentioned polymerization. Since the above-mentioned fluoropolymer performs the polymerization in the presence of the above-mentioned surfactant of the present invention, rather than using a conventional surfactant, particles comprising the fluoropolymer in an aqueous dispersion obtained by polymerization are used. Can be obtained with a small particle size. A preferable lower limit of the concentration of the fluoropolymer in the aqueous dispersion is 10% by mass, a more preferable lower limit is 15% by mass, a preferable upper limit is 40% by mass, a more preferable upper limit is 35% by mass, and a further preferable upper limit is 30% by mass. It is.
[0068]
The aqueous dispersion obtained by carrying out the above polymerization may be concentrated or subjected to a dispersion stabilization treatment to form a dispersion, or may be subjected to coagulation or aggregation to be recovered and dried to obtain a powder or other solid substance. Is also good. Although the method for producing a fluoropolymer of the present invention is for producing a fluoropolymer, the produced fluoropolymer may be a fluoropolymer dispersed in the aqueous dispersion. It may be a fluorinated polymer dispersed in the dispersion or a fluorinated polymer as the powder or other solid substance.
[0069]
The surfactant of the present invention described above can be suitably used also as a dispersant for dispersing the fluoropolymer obtained by polymerization in an aqueous medium.
The aqueous fluoropolymer dispersion of the present invention is one in which particles made of a fluoropolymer are dispersed in an aqueous medium in the presence of the surfactant.
The aqueous fluoropolymer dispersion of the present invention may be an aqueous dispersion obtained by performing the above-described polymerization, or a dispersion obtained by concentrating or dispersing the aqueous dispersion to obtain a dispersion. Or a powder obtained by dispersing a fluoropolymer powder in an aqueous medium in the presence of the surfactant of the present invention.
[0070]
The aqueous medium in the aqueous fluoropolymer dispersion of the present invention is not particularly limited as long as it contains water, and organic solvents such as non-fluorine-containing alcohols, ethers and ketones, for example, dimethylformamide [DMF] and tetrahydrofuran It may contain an organic solvent such as [THF] and / or a fluorine-containing organic solvent having a boiling point of 40 ° C. or lower, or may be water containing no organic solvent. As the aqueous medium, an aqueous medium in polymerization may be used as it is.
[0071]
When the aqueous fluoropolymer dispersion of the present invention is an aqueous dispersion obtained by performing the above-described polymerization, the number average particle diameter is preferably about 0.05 to 1 μm, and more preferably the upper limit is 0.5 μm. Is preferably contained in a concentration of about 10 to 70% by mass. A more preferred lower limit of the concentration is 15% by mass or more, and a more preferred upper limit is 60% by mass or less. On the other hand, in the case of the above-mentioned dispersion, the above-mentioned aqueous fluoropolymer dispersion contains particles made of the above-mentioned fluoropolymer at a concentration of preferably 30 to 50% by mass. In the present specification, the above “number average particle diameter” refers to a transmittance of a 550-nm projection light with respect to a unit length of a PTFE obtained by diluting a solid content concentration of a fluoropolymer to about 0.02 mass%. And the value obtained based on the calibration curve of the average particle size determined by electron micrograph, for other resins, the average particle size determined by relative comparison to standard polystyrene by electron micrograph .
[0072]
The above-mentioned surfactant of the present invention is preferably 0.0001 to 15% by mass of the aqueous fluoropolymer dispersion of the present invention. If the amount is less than 0.0001% by mass, the dispersion stability may be poor. If the amount exceeds 15% by mass, there is no dispersion effect commensurate with the abundance, and this is not practical. A more preferred lower limit of the surfactant is 0.0001% by mass, a more preferred upper limit is 10% by mass, and a still more preferred upper limit is 2% by mass.
[0073]
The aqueous dispersion obtained by carrying out the above polymerization can be concentrated or subjected to a dispersion stabilization treatment to prepare a dispersion.
[0074]
A known method is adopted as the concentration method, and the concentration of the fluoropolymer can be reduced to 40 to 60% by mass depending on the use. Concentration may impair the stability of the dispersion, in which case a dispersion stabilizer may be further added. As the dispersion stabilizer, the surfactant of the present invention and other various surfactants may be added. Preferable examples of the various dispersion stabilizers include nonionic surfactants such as polyoxyalkyl ethers, in particular, polyoxyethylene alkyl phenyl ether (for example, Triton X-100 (trade name) manufactured by Rohm & Haas Co.), Polyoxyethylene ethers such as oxyethylene isotridecyl ether (Dispanol TOC (trade name) manufactured by NOF CORPORATION) and polyoxyethylene propyl tridecyl ether include, but are not limited thereto. Absent.
[0075]
The total amount of the dispersion stabilizer is preferably 0.5 to 20% by mass based on the solid content of the dispersion. When the amount is less than 0.5% by mass, the dispersion stability may be poor. A more preferred lower limit of the surfactant is 2% by mass, and a more preferred upper limit is 12% by mass.
[0076]
The aqueous dispersion obtained by carrying out the above polymerization may be subjected to a dispersion stabilization treatment without being concentrated depending on the use to prepare a fluoropolymer aqueous dispersion having a long pot life. The same dispersion stabilizer as described above can be used.
[0077]
The use of the aqueous fluoropolymer dispersion of the present invention is not particularly limited, and is applied as it is as an aqueous dispersion, and is applied by coating on a substrate, drying and then firing if necessary; nonwoven fabric Impregnation by impregnating and drying a porous support such as a resin molded article, and preferably baking; coating and drying on a substrate such as glass, and immersing in water as necessary, And a cast film formed by peeling the film to obtain a thin film. Examples of these applications include an aqueous dispersion type paint, a binder for an electrode, and a water repellent for an electrode.
[0078]
The aqueous fluoropolymer dispersion of the present invention is a known pigment, a thickener, a dispersant, an antifoaming agent, an antifreezing agent, by blending a compounding agent such as a film-forming aid, or, further, other A polymer compound can be compounded and used as a water-based paint for coating.
[0079]
As the use of the fluoropolymer aqueous dispersion of the present invention, a powder obtained by subjecting the aqueous fluoropolymer dispersion to coagulation or coagulation, collecting, drying, and optionally granulating is used. Applications. For the coagulation or aggregation, a conventionally known method can be employed as it is. For example, a method of adding a coagulant (coagulant) to the aqueous dispersion under stirring to cause coagulation (aggregation), a method of coagulating the aqueous dispersion by freezing and thawing (freeze coagulation method) A method in which the aqueous dispersion is coagulated only by mechanically stirring at high speed (mechanical coagulation method), a method in which the aqueous dispersion is ejected from a thin nozzle and water is simultaneously evaporated (spray coagulation method), and the like Is preferably adopted. If necessary, a coagulation aid may be added. Drying may be left at room temperature, or may be performed in a heated state up to 250 ° C. The resulting powder can be used, for example, as a molding material suitable for paste extrusion or the like by mixing a lubricating aid, or as a powder coating by mixing a pigment if desired.
[0080]
【Example】
Next, the present invention will be described based on examples, but the present invention is not limited to only these examples.
[0081]
Example 1 (Preparation of PTFE latex)
1.5 liters of deionized water, 60 g of paraffin wax (melting point 60 ° C.) and F (CF₂CF₂)₂CH₂CH₂PO (ONH₄)₂Was charged, and the inside of the system was replaced with TFE. The internal temperature was set to 70 ° C., TFE was injected so that the internal pressure became 0.78 MPa, and 5 g of a 0.6% by weight aqueous solution of ammonium persulfate (APS) was charged to start the reaction. Since the pressure in the polymerization system decreased with the progress of polymerization, TFE was continuously added to keep the internal pressure at 0.78 MPa, and the reaction was continued. Four hours after the start of the polymerization, TFE was purged to terminate the polymerization. The following items were measured for this aqueous dispersion. Table 1 shows the results.
[0082]
Solid concentration: determined from the weight loss when the obtained aqueous dispersion was dried at 150 ° C. for 1 hour.
Standard specific gravity (SSG): Measured according to ASTM D1457-69.
Average primary particle diameter: A solid content concentration is diluted to about 0.02% by weight, and based on a calibration curve between the transmittance of 550 nm projection light per unit length and the average particle diameter determined by an electron micrograph. And indirectly determined from the above transmittance.
Particle shape: The presence or absence of rod-shaped particles was confirmed from a transmission electron micrograph of the aqueous dispersion diluted to about 0.02% by weight.
[0083]
Example 2
As shown in Table 1, surfactant 1 (F (CF₂CF₂)₂CH₂CH₂PO (ONH₄)₂) Was changed, and the same measurement as in Example 1 was performed. Table 1 shows the results.
[0084]
Comparative Example 1
Surfactant 1 (F (CF₂CF₂)₂CH₂CH₂PO (ONH₄)₂) Instead of Surfactant 2 (F (CF₂CF₂)₃CF₂COONH₄) And the same measurement as in Example 1 was performed except that the reaction pressure was changed to 2.7 MPa. Table 1 shows the results.
[0085]
[Table 1]

[0086]
From Table 1, F (CF₂CF₂)₂CH₂CH₂PO (ONH₄)₂In Examples 1 and 2 using the F₂CF₂)₃CF₂COONH₄It was found that the primary particle size was smaller than that of Comparative Example 1 using no.
[0087]
【The invention's effect】
The surfactant of the present invention is suitable as a dispersant to be present in an aqueous medium when a fluoropolymer is obtained by performing polymerization in an aqueous medium, and from a fluoropolymer in an aqueous dispersion obtained by polymerization. Can be obtained with a smaller particle size than when a conventional surfactant is used. When the aqueous dispersion obtained by the above polymerization is used as a polymer dispersion, a substrate such as a glass cloth can be more uniformly impregnated than a conventional polymer dispersion. This is advantageous in that it can be increased. Further, when the aqueous dispersion obtained by the above polymerization is subjected to post-treatment and used as a resin powder, it is advantageous because the firing time in the molding process can be shortened. Particles made of the fluoropolymer obtained by using the surfactant of the present invention are advantageous in that they have high sphericity and thus have high dispersibility and good moldability.

Claims (6)

The following general formula (i)
_{Rf- (CH 2) n -PO (} OM) 2 (i)
(Wherein, M represents NH ₄ , Li, Na, K or H. n represents an integer of 1 to 3. Rf represents an alkyl group having 1 or more carbon atoms and having 1 or more fluorine atoms. A surfactant comprising a fluorine-containing phosphoric acid derivative represented by the following formula: The surfactant according to claim 1, wherein Rf is a perfluoroalkyl group having 1 to 4 carbon atoms, and n is 2. Fluorinated phosphoric acid derivatives are
_{C 4 F 9 -C 2 H 4} -PO (ONH 4) 2
The surfactant according to claim 1, which is: A method for producing a fluoropolymer, comprising obtaining a fluoropolymer by performing polymerization in an aqueous medium in the presence of the surfactant according to claim 1. The method for producing a fluoropolymer according to claim 4, wherein the surfactant is added in an amount of 0.0001 to 15% by mass of the aqueous medium at the start of the polymerization. An aqueous dispersion of a fluorine-containing polymer, wherein particles comprising the fluorine-containing polymer are dispersed in an aqueous medium in the presence of the surfactant according to claim 1, 2 or 3.