JP3699819B2 - Polyarylene sulfide and method for producing the same - Google Patents

Description

【００１２】
（式中、η_L は直鎖ＰＡＳの溶融粘度、η_m はＮ値を求めようとしている分岐ＰＡＳの溶融粘度、γは剪断速度を表す。∂ｌｏｇη／∂ｌｏｇγ｜γ₌₂₀₀とは、ｌｏｇγによるｌｏｇηの偏微分∂ｌｏｇη／∂ｌｏｇγにおいて、γ＝２００（ｓｅｃ^-1）における偏微分値を表す。）
式（５）における、直鎖ＰＡＳとは、Ｎ値を求めようとしている分岐ＰＡＳと同じ繰り返し単位からなり、さらに共重合体の場合は同じ構成モノマー比率であり、且つ、ある剪断速度（本願の場合は、２００／ｓ）で、Ｎ値を求める分岐ＰＡＳと同じ溶融粘度を持つ直鎖ＰＡＳを指す。
【００１３】
なお、ｌｏｇηをｌｏｇγの関数としてｌｏｇη＝ｆ（ｌｏｇγ）で表すにあたっては、以下の関係式から、ある剪断速度における溶融粘度値を数点求め、その数点について、最小自乗法等の数学的処理をすることにより関数化することができる。
即ち、剪断速度及び剪断応力は、一定のシリンダー及びオリフィスを有するキャピラリーレオメーターを用いることにより、試料をある一定の押出速度で押し出すのに要する荷重から以下の計算式に基づいて得られる値である。
【００１４】
・剪断速度（ｓｅｃ^-1）
＝｛４・（ＳＲ）² ・押出速度（ｍｍ／分）｝／（１０×６０×Ｒ³ ）
・剪断応力（ｄｙｎｅ／ｃｍ² ）
＝｛荷重（ｋｇ）・９８０・１０³ ｝／｛π・（ＳＲ）・２・Ｌ｝
これらにおいて、ＳＲはシリンダー半径、Ｒはオリフィス半径、Ｌはオリフィス長さである。このとき、溶融粘度は、次式により求められる。
【００１５】
・溶融粘度（ｐｏｉｓｅ）
＝剪断応力（ｄｙｎｅ／ｃｍ² ）／剪断速度（ｓｅｃ^-1）
【００１６】
【発明の実施の形態】
以下、本発明のＰＡＳ及びその製造方法について具体的に説明する。
１．本発明のＰＡＳの特徴
本発明のＰＡＳは、−Ａｒ−Ｓ−（但しＡｒはアリール基）で表される繰り返し単位を７０モル％以上含有している。代表的なものは、下記構造式（Ｉ）
【００１７】
【化１】

【００１８】
（式中、Ｒ¹は炭素数６以下のアルキル基及びアルコキシ基、フェニル基、カルボン酸及びその金属塩、アミノ基、ニトロ基、並びにフッ素，塩素，臭素等のハロゲン原子からなる群から選ばれる置換基であり、ｍは０〜４の整数である。）で示される繰り返し単位を７０モル％以上有するＰＡＳであり、溶液粘度（ウベローデ粘度計を用い、測定溶媒がα−クロロナフタレン，測定濃度０.4ｇ／ｄｌ、測定温度２０６℃で測定した値）が、０．１３〜０．５０ｄｌ／ｇ、好ましくは０．１５〜０．４５ｄｌ／ｇ、特に好ましくは０．２０〜０．３５ｄｌ／ｇである。又、本発明のＰＡＳは構造式（Ｉ）以外に共重合構成単位として、メタフェニレンスルフィド単位、オルソフェニレンスルフィド単位、ｐ，ｐ’−ジフェニレンケトンスルフィド単位、ｐ，ｐ’−ジフェニレンスルホンスルフィド単位、ｐ，ｐ’−ビフェニレンスルフィド単位、ｐ，ｐ’−ジフェニレンエーテルスルフィド単位、ｐ，ｐ’−ジフェニレンメチレンスルフィド単位、ｐ，ｐ’−ジフェニレンクメニルスルフィド単位、ナフチルスルフィド単位などを３０モル％未満含んでいても良い。
【００１９】
本発明ＰＡＳの特徴の一つは、溶融粘度η_m とＮ値の関係式、
Ｎ≧0.3 log₁₀（η_m )+ 0.5・・・（１），Ｎ≧１．１０・・・（２）
を満たすことであり、更に好ましくは、
Ｎ≧0.3 log₁₀（η_m )+0.55・・・（６），Ｎ≧１．1 ０・・・（２）
より好ましくは、
Ｎ≧0.3 log₁₀（η_m )+0.６ ・・（７），Ｎ≧１．１０・・・（２）
を満たすことである。
【００２０】
一般にＮ値が大きい程バリが少ないが、前記関係式を満たす本発明のＰＡＳは、従来の分岐ＰＡＳに比べ、同じ溶融粘度におけるＮ値が大きく、バリ抑制性能に優れている。従来の分岐ＰＡＳは、Ｎ値を大きくすると、溶融粘度も増大し、結果として成形性悪化、特に射出成形性が悪くなり、実用面で不利であった。本発明のＰＡＳは、実用的な成形性を持つ溶融粘度領域において、従来の分岐ＰＡＳに比べ、優れたバリ抑制性能を示す。
【００２１】
本発明のＰＡＳにおいては、Ｎ値が１．１０以上、好ましくは１．１０〜１．５０、更に好ましくは１．２０〜１．４５である。１．１０未満だと成形時のバリの低減が十分でなく、１．５０を超えると機械的強度、特に靱性が低下するおそれがあるうえ、溶融粘度が高すぎて成形条件が厳しくなるおそれもある。
また、溶融粘度η_m は、射出、押出、ゲル成形法等公知の成形法で成形可能な限り特に制限はないが、好ましくは２０〜１５００Ｐａ・ｓ、更に好ましくは６０〜１０００Ｐａ・ｓ、特に好ましくは８０〜８００Ｐａ・ｓである。２０Ｐａ・ｓ未満の場合、成形が困難、又は成形できても機械的物性、耐熱性等、ＰＡＳの良好な特性が十分に発現されない恐れがあり、１５００Ｐａ・ｓを越えると成形が困難、又は成形方法、成形条件の選択幅が非常に狭くなる恐れがある。
【００２２】
本発明のＰＡＳは、前記式（１）及び（２）、好ましくは（６）及び（２）、特に好ましくは（７）及び（２）を満たすうえに、更に下記
Ｆ≧５７ｌｏｇ₁₀（η_m ）−６０・・（３）、Ｆ≧４０・・（４）
好ましくは、
Ｆ≧５７ｌｏｇ₁₀（η_m ）−５５・・（８）、Ｆ≧４０・・（４）
より好ましくは、
Ｆ≧５７ｌｏｇ₁₀（η_m ）−５０・・（９）、Ｆ≧４０・・（４）
を満たすものである。
【００２３】
このような本発明のＰＡＳは、従来の熱架橋ＰＡＳ等に比べ、同じ溶融粘度においてより大きな曲げ強度を示す。
本発明のＰＡＳにおいて、曲げ強度は４０ＭＰａ以上、好ましくは５０ＭＰａ以上、特に好ましくは６０ＭＰａ以上である。曲げ強度が４０ＭＰａ未満の場合、実用上使用できる用途が著しく狭くなる。
２．ＰＡＳの製造方法
上述した本発明のＰＡＳは、本発明の方法により以下のように製造することができる。
【００２４】
すなわち、本発明は、溶液粘度が０．０５〜０．２５ｄｌ／ｇであるＰＡＳのプレポリマー、該プレポリマーが溶解している溶液又はスラリーのいずれかに分岐剤を添加して、更に必要に応じて重合溶媒及び硫黄源を添加して、２３０〜２９０℃で縮重合させること、及び重合時の重合溶液が相分離していないことを特徴とするＰＡＳの製造方法を提供するものである。
【００２５】
プレポリマーは、溶液粘度が０．０５〜０．２５ｄｌ／ｇ、好ましくは０．０７〜０．２０ｄｌ／ｇであり、分岐していないことを除けば、前記本発明ＰＡＳと同じ組成を有する。
プレポリマーの溶液粘度が０．０５ｄｌ／ｇ未満の場合、低分子量のＰＡＳも生成するため分子量分布が広くなり、その結果、成形時にガスが発生したり、成形品の耐熱性が低下する恐れがある。プレポリマーの溶融粘度が０．２５ｄｌ／ｇを超えると、ＰＡＳの高分子量化は進むが、その割りにはＮ値や強度が向上しないため、本発明のＰＡＳが得られない。
【００２６】
プレポリマーの製造方法は、例えば本願比較例３の様な公知の直鎖ＰＡＳの製造方法に準じて良く、任意の溶液粘度のプレポリマーを得るために、重合時間等を適宜設定すれば良い。
重合時間は重合助剤や水の有無等により変動するが、通常０．１〜４時間、好ましくは０．１〜２時間である。０．１時間より短いとプレポリマーの溶液粘度が０．０５ｄｌ／ｇ未満になることがあり、４時間を超えると溶液粘度が０．２５ｄｌ／ｇを超えることがある。
【００２７】
なお、本発明のプレポリマーは、本発明の製造方法において分岐剤を添加して重合する前に反応系に存在するＰＡＳを意味しており、低分子量のいわゆるオリゴマーに限定されるものではなく、通常ポリマーと見なされる程度の分子量を有するものでもあり得る。
前記分岐剤は公知の分岐剤を使用して良く、例えば特開昭５６−２８２１７号公報に記載されている、トリクロロベンゼン、トリブロモベンゼン、テトラクロロナフタレン等の３個以上のハロゲン置換基を持つポリハロ芳香族化合物や、ジハロゲン化アニリン、ジハロゲン化ニトロベンゼンが挙げられる。その中でも特に１，２，４−トリクロロベンゼン、１，３，５−トリクロロベンゼンが好ましい。
【００２８】
プレポリマーの繰り返し単位のモル数に対する分岐剤の添加割合は、求める分岐度に合わせて定められるが、通常ば０．１〜１．５ｍｏｌ％、好ましくは０．３〜１．２ｍｏｌ％、更に好ましくは０．５〜１．０ｍｏｌ％である。分岐剤の添加割合が必要以上に多いと、分岐度が必要以上に大きくなりすぎて、成形性悪化、強度低下が起こることもあり、必要以上に少ないと分岐度が小さく、成形時のバリ抑制性能が劣る。
【００２９】
重合溶媒は、ＰＡＳの重合に使用できる公知の溶媒を使用して良く、例えば特開昭５６−２８２１７号公報に記載されて有機アミド溶媒が挙げられる。その中でもＮ−メチル−２−ピロリドンが好ましい。
重合に際し、重合溶媒が状況に応じて追加される。例えば、プレポリマーが固体状の場合は、重合を実行できるに足る量、添加すべきであり、溶媒に溶解している場合、若しくはスラリー状の場合は必ずしも重合溶媒を添加する必要はない。
【００３０】
本発明では、重合溶液中における重合溶媒の存在量は、プレポリマーの繰り返し単位のモル数に対し、モル比で２〜２０が好ましく、更に好ましくは３〜１５である。
前記硫黄源も公知のものが使用でき、例えば特開昭５５−２８２１７号公報に記載されているアルカリ金属スルフィドや、アルカリ土類金属スルフィドが挙げられる。その中でも硫化リチウム，硫化ナトリウムが好ましい。
【００３１】
重合溶液中に含まれる硫黄源の存在量は、プレポリマーの繰り返し単位のモル数に対し通常、０〜１０モル％、好ましくは０．９〜６モル％である。１０モル％を超えると、解重合等の分解反応が進むことがある。
更に必要なら水酸化リチウムを、プレポリマーの繰り返し単位のモル数に対しモル比で、０〜１０、好ましくは１〜５添加しても良い。
【００３２】
重合温度は、重合時の重合溶液が相分離せず、均一相を保つように、２３０〜２９０℃、好ましくは２４０〜２８０℃、特に好ましくは２５０℃〜２７５℃とする。プレポリマー及び重合中に生成するＰＡＳが溶媒に溶解して相分離しない範囲で多段階に変化させても良い。
重合時間は特に制限はないが、通常、０．１〜２４時間、好ましくは０．５〜１０時間、特に好ましくは０．５〜２時間である。重合時間は、重合温度、触媒等により影響されるが、必要以上に長過ぎても、得られるＰＡＳの強度が低下したり、一部ＰＡＳが分解して低分子量成分が増えたＰＡＳが得られることもあり、経済的にも物性面でも不利になる恐れがある。
【００３３】
本発明の重合方法において、重合時の重合溶液の相分離を防ぎ、均一相を保持する方法としては、重合温度を適切に設定する以外に、重合溶液中の重合副成塩を減らすか、水分量を適切に設定することが挙げられる。
重合副成塩を減らす方法としては、例えば、水、ＮＭＰ等の重合溶媒で洗浄したプレポリマーを用いることが挙げられる。
【００３４】
重合溶液中の水分量は、本発明の効果を阻害しない限り特に制限されないが、反応溶液の重量を１００％として１０％以内、特に５％以内であるのが好ましい。水分量が１０％を越えると、重合溶液が相分離するおそれがある。
また、プレポリマーに分岐剤等を添加した直後の重合溶液中に含まれるジハロ芳香族化合物は、プレポリマーの繰り返しモル数とジハロ芳香族化合物のモル数の総和に対し、３０モル％以下であることが好ましく、より好ましくは２０モル％以下、特に好ましくは１０モル％以下である。
【００３５】
重合溶液中にジハロ芳香族化合物が多いと、最終的に得られるＰＡＳの分子量分布が広くなり、ＰＡＳの耐熱性が低下したり、重合副生塩が多く発生し、重合溶液が相分離する恐れがある。
ジハロ芳香族化合物の存在量が少ない重合溶液を得るためには、プレポリマーを合成する際、ジハロ芳香族化合物の転化率が、好ましくは７０モル％以上、より好ましくは８０モル％以上、特に好ましくは９０モル％より大きくなるまで反応させるか、プレポリマ−を含む溶液から、プレポリマ−を析出させた後、水やＮＭＰ等の重合溶媒や塩化メチレン、アセトン等の有機溶媒で十分に洗浄すれば良い。
【００３６】
重合後が終了した後の反応溶液から、本発明のＰＡＳを取り出す方法は公知の方法で良い。例えば水等の相分離剤を添加して冷却させることで、顆粒及び／又は粉末状ＰＡＳとして取り出す方法、水等の相分離剤を添加し、かつＰＡＳが析出しない温度に保持して相分離剤させ、反応槽の下部からＰＡＳ相（液相）で取り出す方法が挙げられる。
【００３７】
取り出したＰＡＳは水、ＮＭＰ等の有機溶媒で洗浄した後、フラッシュ法で洗浄液を除去する等、公知の方法で精製することができる。
〔実施例〕
以下、本発明を実施例によってさらに具体的に説明する。
なお、評価は次の方法で行なった。
(1) 溶融粘度（η_m ）
キャピラリーレオメーター（東洋精機社製、キャピログラフＩ型相当）を用いて、樹脂温度３００℃、オリフィス半径１ｍｍ，オリフィス長さ４０ｍｍの条件下で前述の算出方法により求めた。
(2) 分岐度指数（Ｎ値）
各剪断速度における溶融粘度の値を５点以上求め、各々のｌｏｇ値について最小自乗法によりｌｏｇηをｌｏｇγの関数としてｌｏｇη＝ｆ（ｌｏｇγ）を求め、前述の方法により分岐度指数Ｎ値を算出した。
(3) 曲げ強度（Ｆ）
試料を３２０℃、５０ｋｇｆ／ｃｍ² で長さ５０ｍｍ×２ｍｍにプレス成形し、２２０℃、２時間アニ−ルしたものを、スパン４０ｍｍ，テストスピ−ド１．０ｍｍ／分で測定した値。（島津製作所株式会社，精密万能試験機：島津オ−トグラフＩＳ−５０００Ｂを使用）
［実施例１］
ステンレス製１０リットルオートクレーブに、硫化リチウム５４０．８ｇ、ＮＭＰ５．１リットル、パラジクロロベンゼン（ＰＤＣＢ）１６９５．７ｇ、水酸化リチウム５．３ｇ、水３１８．１ｇを仕込み、窒素雰囲気下、２６０℃まで昇温し、０．５時間反応させ、プレポリマ−を合成した。
【００３８】
プレポリマ−を反応液から分離し、ＮＭＰ次いで水、アセトンを用いて洗浄し、１２０℃、８時間減圧乾燥した。得られたプレポリマ−の溶液粘度は０．１４ｄｌ／ｇであった。
次いで１リットルオートクレーブに、プレポリマ−５１．８４ｇ、硫化リチウム０．５５ｇ，トリクロロベンゼン（ＴＣＢ）０．７３ｇ，水酸化リチウム０．６ｇ、水８．６５ｇ、ＮＭＰ２１６．３２ｇを仕込み、窒素雰囲気下、２６０℃で１時間反応させ（本重合）、ポリマーを合成した。仕込んだ重合成分が重合溶媒に溶解してから重合終了時まで、重合溶液は相分離しなかった。
【００３９】
重合溶液を冷却して、ポリマーを析出させたのち、遠心分離機で重合溶媒を分離した。得られた重合体をＮＭＰ次いで水、アセトンを用いて洗浄し、１２０℃、８時間減圧乾燥した。得られたポリマ−の溶融粘度は３６４Ｐａ・ｓ、Ｎ値は１．４９、Ｆは１２４ＭＰａであった。
［実施例２］
プレポリマーに添加する硫化リチウムの量を０．４８ｇ、ＴＣＢの量を０．６４ｇに変えた以外は、実施例１と同様に操作し、ポリマーを合成した。得られたポリマ−の溶融粘度は１２７Ｐａ・ｓ、Ｎ値は１．２３、Ｆは８０ＭＰａであった。
［実施例３］
プレポリマーの合成時間を１ｈｒとして溶液粘度０．１７ｄｌ／ｇのプレポリマーを合成し、次の重合に用いたこと、硫化リチウムの量を０．３４ｇ、ＴＣＢの量を０．４５ｇに変えた以外は、実施例１と同様に操作し、ポリマーを合成した。得られたポリマ−の溶融粘度は２４３Ｐａ・ｓ、Ｎ値は１．３０、Ｆは１０２ＭＰａであった。
［実施例４］
プレポリマーの合成時間を０.1ｈｒとして溶液粘度０．１１ｄｌ／ｇのプレポリマーを合成し、次の重合に用いたこと、硫化リチウムの量を０.7５ｇ、ＴＣＢの量を０．９１ｇに変えた以外は、実施例１と同様に操作し、ポリマーを合成した。得られたポリマ−の溶融粘度は１３５Ｐａ・ｓ、Ｎ値は１.3３、Ｆは７６ＭＰａであった。
［実施例５］
プレポリマーに添加するＴＣＢの量を０．５４ｇに変えた以外は、実施例１と同様に操作し、ポリマーを合成した。得られたポリマーの溶融粘度は６７Ｐａ・ｓ、Ｎ値は１．１１、Ｆは４５ＭＰａであった。
［実施例６］
プレポリマーに、更にチオフェノール０．８３ｇを加えた以外は、実施例１と同様に操作し、ポリマーを合成した。得られたポリマ−の溶融粘度は１１１Ｐａ・ｓ、Ｎ値は１．１８、Ｆは８２ＭＰａであった。
［実施例７］
本重合時間を０．５時間にした以外は、実施例１と同様に操作しポリマーを合成した。得られたポリマ−の溶融粘度は１３５Ｐａ・ｓ、Ｎ値は１.3３、Ｆは７６ＭＰａであった。
［実施例８］
プレポリマーに添加するＴＣＢの量を０．４５ｇに変えて、本重合時間を２時間に変えた以外は、実施例１と同様に操作しポリマーを合成した。得られたポリマ−の溶融粘度は３６４Ｐａ・ｓ、Ｎ値は１.3２、Ｆは７２ＭＰａであった。
［実施例９］
プレポリマーに添加する水酸化リチウムを０．２４ｇに変えた以外は、実施例１と同様に操作しポリマーを合成した。得られたポリマ−の溶融粘度は２３６Ｐａ・ｓ、Ｎ値は１.3８、Ｆは１０４ＭＰａであった。
［実施例１０］
実施例３で得られたプレポリマーに添加するＴＣＢの量を０．５４ｇに変えた以外は、実施例１と同様に操作しポリマーを合成した。得られたポリマ−の溶融粘度は６９６Ｐａ・ｓ、Ｎ値は１.4４、Ｆは１１８ＭＰａであった。
［比較例１］
１リットルオートクレーブに、ＰＤＣＢ１１０．２６ｇ、硫化リチウム３４．４６ｇ、ＴＣＢ１．６３ｇ、水２４．５３ｇ、ＮＭＰ３３４．２１ｇを仕込み、窒素雰囲気下、２６０℃、３時間反応し、ポリマーを合成した。
【００４０】
ポリマーを反応液から分離し、ＮＭＰ次いで水、アセトンを用いて洗浄し、１２０℃、８時間減圧乾燥した。得られたポリマ−の溶融粘度は１７９Ｐａ・ｓ、Ｎ値は１．４０、Ｆは４１ＭＰａであった。
［比較例２］
ＴＣＢの量を０．６９ｇ、水の量を１０．０９ｇに変えた以外は、比較例１と同様の操作を行なった。得られたポリマ−の溶融粘度は２４５Ｐａ・ｓ、Ｎ値は１．３０、Ｆは５８ＭＰａであった。
［比較例３］
ＴＣＢを添加せず、水の量を１０．０９ｇに変えた以外は、比較例１と同様の操作を行なった。得られたポリマ−の溶融粘度は１００Ｐａ・ｓ、Ｎ値は１．０１、Ｆは１１２ＭＰａであった。
［比較例４］
２６０℃で１時間経た後に、ＴＣＢを１．６３ｇ添加し、更に１時間反応を続けた以外は比較例１と同様に行なった。得られたポリマ−の溶融粘度は１８９Ｐａ・ｓ、Ｎ値は１．３４，Ｆは５５ＭＰａであった。
【００４１】
以上の結果を表１、図１及び図２に記す。
【００４２】
【表１】

【００４３】
【図１】
【００４４】
【図２】
図１，図２の◆（実施例）及び△、×（比較例）の添字は、各々実施例、比較例のＮｏを意味する。△は分岐剤を仕込み時に添加した比較例、×は重合の途中で分岐剤を添加した比較例である。
図１において、実施例３と比較例４は共に式（１）を満たし、かつ溶融粘度とＮ値がほぼ同じ分岐ＰＡＳである。公知技術からは両方の分岐ＰＡＳは同等の曲げ強度を持つと予測されるが、実際は図２の示すごとく、比較例４は実施例３に比べ著しく低い曲げ強度しか示せない。
【００４５】
又、図１において、実施例９と比較例１は共に式（１）を満たし、Ｎ値は同程度、溶融粘度は実施例９が大きい。公知の傾向からも実施例９の曲げ強度が比較例１よりある程度は大きいことが予測される。しかし実際は図２の示す如く、実施例９は、比較例１の約２．５倍の曲げ強度を示し、予測できない値である。
【００４６】
【発明の効果】
以上説明したように本発明のＰＡＳは、機械的強度に優れるうえ、成形時のバリ発生量が極めて少なく、流動特性に優れることから、種々の成形及び用途、とりわけ射出成形法による精密成形品の成形材料として用いることができる。
【図面の簡単な説明】
【図１】ＰＡＳの溶融粘度とＮ値の関係を示すグラフである。
【図２】ＰＡＳの溶液粘度と曲げ強度の関係を示すグラフである。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing polyarylene sulfide (hereinafter sometimes abbreviated as PAS), and a PAS obtained thereby. More specifically, the present invention relates to a PAS production method in which a branching agent or the like is added to a prepolymer and repolymerized, and the PAS obtained thereby.
[0002]
[Prior art]
PAS is known as an engineering plastic excellent in mechanical strength, heat resistance, chemical resistance and the like, and its molded product is used in various applications.
However, it has been pointed out that the PAS molding has a disadvantage that burrs are generated.
[0003]
Various methods have been proposed as a method for reducing the amount of burrs. For example, there is a method in which a lot of branches are introduced by thermal crosslinking. In this case, although the amount of burrs is reduced, there is a possibility that mechanical properties are lowered and decomposition gas is generated (Japanese Patent Laid-Open No. 64-9266). Publication).
In order to compensate for the drawbacks of thermally crosslinked PAS, a branched PAS obtained by polycondensation after adding a branching agent such as trichlorobenzene to the reaction system was proposed (JP-A-51-144497, etc.). Although its strength is improved as compared with heat-crosslinked PAS, it is inferior to that of linear PAS, and its use in a field requiring low burr properties and high strength is sometimes discouraged.
[0004]
Furthermore, a branched PAS (JP-A-55-28217) obtained by adding a branching agent and performing polycondensation until about 75 minutes until the condensation polymerization of PAS is completed has been proposed. There was a problem similar to the above.
In addition, it is compounded with other resins (JP-A-4-213357, etc.), copolymerized (JP-A-8-134352, etc.), or polyarylene sulfide is modified (JP-A-5-170908). However, these techniques cannot be said to satisfy the low burr and high strength sufficiently.
[0005]
[Problems to be solved by the invention]
The present invention has been made in view of the above-mentioned problems. In addition to excellent mechanical strength, the amount of burrs generated at the time of molding is extremely small, and since it is excellent in fluid moldability, polyarylene sulfide that can be variously molded and its production It aims to provide a method.
[0006]
[Means for Solving the Problems]
As a result of intensive studies on the above problems, the present inventors have added a branching agent to the prepolymer, and if necessary, added a polymerization solvent and a sulfur source for repolymerization, so that the degree of branching is high, that is, low burrability is achieved. And found that a high-strength PAS can be obtained, and the present invention has been completed based on such findings.
[0007]
That is, this invention provides the manufacturing method of the following PAS.
1. A prepolymer of polyarylene sulfide having a solution viscosity of 0.05 to 0.25 dl / g, a solution in which the prepolymer is dissolved, or a slurry containing the prepolymer, a branching agent, and optionally a polymerization solvent and / or Alternatively, a polyarylene obtained by polymerizing at a temperature of 230 to 290 ° C. in a state where the polymerization solution is not phase-separated by adding a sulfur source to obtain a PAS satisfying the following formulas (1) to (4): A method for producing sulfide.
N ≧ 0.3 × log ₁₀ (η _m ) +0.55 (1)
N ≧ 1.10 (2)
F ≧ 57 × log ₁₀ (η _m ) −60 (3)
F ≧ 40 (4)
[In the above formulas, F is the bending strength (unit: MPa), N is the branching index, and η _m is the melt viscosity (unit: Pa · s). ]
2. 2. The method for producing PAS as described in 1 above, wherein the amount of the dihaloaromatic compound in the polymerization solution is 30 mol% or less based on the total number of moles of the prepolymer and the dihaloaromatic compound.
3. 3. The process for producing a PAS according to 1 or 2 above, wherein the melt viscosity η _{m of the} PAS is 20 to 1500 Pa · s.
[0008]
The definitions of the bending strength F, melt viscosity η _m , solution viscosity, and branching index N (hereinafter also referred to as N value) are as follows.
Bending strength F was measured at a span of 40 mm and a test speed of 1.0 mm / min after press-molding PAS at 320 ° C. and 50 kgf / cm ² to a length of 50 mm × 2 mm and annealing at 220 ° C. for 2 hours. Bending strength.
[0009]
The melt viscosity η _m was determined using a capillograph using a resin temperature of 300 ° C. and a shear rate of 200 / sec. Viscosity measured with an orifice radius of 1 mm and an orifice length of 40 mm.
The solution viscosity is a viscosity measured using an Ubbelohde viscometer at a measurement solvent of α-chloronaphthalene, a measurement concentration of 0.4 g / dl, and a measurement temperature of 206 ° C.
[0010]
The N value of the degree of branching index is the following when the melt viscosity η (unit: poise) and the shear rate γ (unit: sec ⁻¹ ) of the resin is expressed as log η = f (log γ) as a function of log γ. It is a value represented by an expression.
[0011]
[Expression 1]

[0012]
(Where η _L is the melt viscosity of linear PAS, η _m is the melt viscosity of the branched PAS whose N value is to be obtained, and γ is the shear rate. ∂log η / ∂log γ | γ _{= 200} is log γ (The partial differential value of logη by ∂logη / ∂logγ is represented by a partial differential value at γ = 200 (sec ⁻¹ ).)
In the formula (5), the linear PAS is composed of the same repeating unit as the branched PAS for which the N value is to be obtained, and in the case of a copolymer, has the same constituent monomer ratio, and has a certain shear rate (of the present application). In the case of 200 / s), it refers to a linear PAS having the same melt viscosity as the branched PAS for which the N value is obtained.
[0013]
In expressing log η as a function of log γ by log η = f (log γ), several points of melt viscosity values at a certain shear rate are obtained from the following relational expression, and mathematical processing such as a least square method is performed on the several points. Can be made into a function.
That is, the shear rate and the shear stress are values obtained from the load required to extrude a sample at a certain extrusion speed by using a capillary rheometer having a certain cylinder and orifice based on the following calculation formula. .
[0014]
・ Shear rate (sec ^-1 )
= {4 · (SR) ² · Extrusion speed (mm / min)} / (10 × 60 × R ³ )
・ Shear stress (dyne / cm ² )
= {Load (kg) · 980 · 10 ³ } / {π · (SR) · 2 · L}
In these, SR is a cylinder radius, R is an orifice radius, and L is an orifice length. At this time, melt viscosity is calculated | required by following Formula.
[0015]
-Melt viscosity (poise)
= Shear stress (dyne / cm ² ) / shear rate (sec ⁻¹ )
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the PAS of the present invention and the production method thereof will be specifically described.
1. Features of PAS of the Present Invention The PAS of the present invention contains 70 mol% or more of a repeating unit represented by —Ar—S— (wherein Ar is an aryl group). A typical one is represented by the following structural formula (I)
[0017]
[Chemical 1]

[0018]
(In the formula, R ¹ is selected from the group consisting of alkyl groups and alkoxy groups having 6 or less carbon atoms, phenyl groups, carboxylic acids and their metal salts, amino groups, nitro groups, and halogen atoms such as fluorine, chlorine and bromine. It is a substituent and m is an integer of 0 to 4. The PAS has a repeating unit represented by 70 mol% or more. Solution viscosity (using Ubbelohde viscometer, measurement solvent is α-chloronaphthalene, measurement concentration 0.4 g / dl, measured at a measurement temperature of 206 ° C.) is 0.13 to 0.50 dl / g, preferably 0.15 to 0.45 dl / g, particularly preferably 0.20 to 0.35 dl / g. g. In addition to the structural formula (I), the PAS of the present invention includes a metaphenylene sulfide unit, an orthophenylene sulfide unit, a p, p′-diphenylene ketone sulfide unit, and a p, p′-diphenylenesulfone sulfide as copolymerization structural units. Units, p, p'-biphenylene sulfide units, p, p'-diphenylene ether sulfide units, p, p'-diphenylenemethylene sulfide units, p, p'-diphenylenecumenyl sulfide units, naphthyl sulfide units, etc. You may contain less than 30 mol%.
[0019]
One of the features of the present invention PAS is a relational expression between melt viscosity η _m and N value,
N ≧ 0.3 log ₁₀ (η _m ) + 0.5 (1), N ≧ 1.10 (2)
More preferably,
N ≧ 0.3 log ₁₀ (η _m ) +0.55 (6), N ≧ 1.10 (2)
More preferably,
N ≧ 0.3 log ₁₀ (η _m ) +0.6 (7), N ≧ 1.10 (2)
Is to satisfy.
[0020]
In general, the larger the N value, the smaller the burr, but the PAS of the present invention that satisfies the above relational formula has a larger N value at the same melt viscosity and is superior in burr suppression performance compared to the conventional branched PAS. The conventional branched PAS has a disadvantage in practical use because the melt viscosity also increases when the N value is increased, and as a result, the moldability deteriorates, particularly the injection moldability deteriorates. The PAS of the present invention exhibits an excellent burr suppression performance as compared with a conventional branched PAS in a melt viscosity region having practical moldability.
[0021]
In the PAS of the present invention, the N value is 1.10 or more, preferably 1.10 to 1.50, more preferably 1.20 to 1.45. If it is less than 1.10, burr reduction at the time of molding is not sufficient, and if it exceeds 1.50, the mechanical strength, particularly toughness, may be lowered, and the melt viscosity may be too high, resulting in severe molding conditions. is there.
The melt viscosity η _m is not particularly limited as long as it can be molded by a known molding method such as injection, extrusion, or gel molding, but is preferably 20 to 1500 Pa · s, more preferably 60 to 1000 Pa · s, particularly preferably. Is 80 to 800 Pa · s. If it is less than 20 Pa · s, molding may be difficult, or even if it can be molded, good properties of PAS such as mechanical properties and heat resistance may not be sufficiently developed. If it exceeds 1500 Pa · s, molding is difficult, or molding There is a possibility that the selection range of the method and molding conditions may be very narrow.
[0022]
The PAS of the present invention satisfies the following formulas (1) and (2), preferably (6) and (2), particularly preferably (7) and (2), and the following F ≧ 57 log ₁₀ (η _m ) -60 (3), F ≧ 40 (4)
Preferably,
F ≧ 57 log ₁₀ (η _m ) −55 (8), F ≧ 40 (4)
More preferably,
F ≧ 57log ₁₀ (η _m ) −50 (9), F ≧ 40 (4)
It satisfies.
[0023]
Such a PAS of the present invention exhibits a higher bending strength at the same melt viscosity as compared with a conventional thermally crosslinked PAS or the like.
In the PAS of the present invention, the bending strength is 40 MPa or more, preferably 50 MPa or more, particularly preferably 60 MPa or more. When the bending strength is less than 40 MPa, practically usable applications are remarkably narrowed.
2. PAS Manufacturing Method The PAS of the present invention described above can be manufactured as follows by the method of the present invention.
[0024]
That is, the present invention further adds a branching agent to a prepolymer of PAS having a solution viscosity of 0.05 to 0.25 dl / g, a solution or slurry in which the prepolymer is dissolved, and further required. Accordingly, the present invention provides a method for producing PAS, characterized in that a polymerization solvent and a sulfur source are added to cause condensation polymerization at 230 to 290 ° C., and that a polymerization solution at the time of polymerization is not phase-separated.
[0025]
The prepolymer has a solution viscosity of 0.05 to 0.25 dl / g, preferably 0.07 to 0.20 dl / g, and has the same composition as the PAS of the present invention except that it is not branched.
When the solution viscosity of the prepolymer is less than 0.05 dl / g, low molecular weight PAS is also generated, resulting in a broad molecular weight distribution. As a result, gas may be generated during molding, and the heat resistance of the molded product may be reduced. is there. When the melt viscosity of the prepolymer exceeds 0.25 dl / g, the PAS increases in molecular weight, but the N value and strength do not improve for that, so the PAS of the present invention cannot be obtained.
[0026]
The production method of the prepolymer may be in accordance with, for example, a known production method of linear PAS as in Comparative Example 3 of the present application, and a polymerization time and the like may be appropriately set in order to obtain a prepolymer having an arbitrary solution viscosity.
The polymerization time varies depending on the presence or absence of a polymerization aid and water, but is usually 0.1 to 4 hours, preferably 0.1 to 2 hours. If it is shorter than 0.1 hour, the solution viscosity of the prepolymer may be less than 0.05 dl / g, and if it exceeds 4 hours, the solution viscosity may exceed 0.25 dl / g.
[0027]
The prepolymer of the present invention means PAS present in the reaction system before adding and polymerizing the branching agent in the production method of the present invention, and is not limited to a so-called oligomer having a low molecular weight, It may also have a molecular weight that is normally considered a polymer.
As the branching agent, a known branching agent may be used, which has, for example, three or more halogen substituents such as trichlorobenzene, tribromobenzene and tetrachloronaphthalene described in JP-A-56-28217. Examples include polyhaloaromatic compounds, dihalogenated anilines, and dihalogenated nitrobenzenes. Of these, 1,2,4-trichlorobenzene and 1,3,5-trichlorobenzene are particularly preferable.
[0028]
The addition ratio of the branching agent to the number of moles of the repeating unit of the prepolymer is determined according to the degree of branching to be obtained, but is usually 0.1 to 1.5 mol%, preferably 0.3 to 1.2 mol%, more preferably Is 0.5 to 1.0 mol%. If the branching agent is added more than necessary, the degree of branching may become excessively large, resulting in deterioration of moldability and strength reduction. If it is less than necessary, the degree of branching will be small and burr suppression during molding will be suppressed. The performance is inferior.
[0029]
As the polymerization solvent, a known solvent that can be used for the polymerization of PAS may be used, and examples thereof include organic amide solvents described in JP-A-56-28217. Of these, N-methyl-2-pyrrolidone is preferred.
In the polymerization, a polymerization solvent is added depending on the situation. For example, when the prepolymer is in a solid state, it should be added in an amount sufficient to carry out the polymerization, and when it is dissolved in a solvent or in a slurry state, it is not always necessary to add a polymerization solvent.
[0030]
In the present invention, the amount of the polymerization solvent in the polymerization solution is preferably 2 to 20, more preferably 3 to 15 in terms of molar ratio with respect to the number of moles of the repeating unit of the prepolymer.
Known sulfur sources can be used, and examples thereof include alkali metal sulfides and alkaline earth metal sulfides described in JP-A No. 55-28217. Of these, lithium sulfide and sodium sulfide are preferable.
[0031]
The abundance of the sulfur source contained in the polymerization solution is usually 0 to 10 mol%, preferably 0.9 to 6 mol%, based on the number of moles of the repeating unit of the prepolymer. If it exceeds 10 mol%, a decomposition reaction such as depolymerization may proceed.
Further, if necessary, lithium hydroxide may be added in a molar ratio of 0 to 10, preferably 1 to 5, with respect to the number of moles of the repeating unit of the prepolymer.
[0032]
The polymerization temperature is 230 to 290 ° C., preferably 240 to 280 ° C., particularly preferably 250 to 275 ° C. so that the polymerization solution during polymerization does not phase separate and maintains a uniform phase. The prepolymer and the PAS produced during the polymerization may be changed in multiple stages as long as they are dissolved in the solvent and do not undergo phase separation.
The polymerization time is not particularly limited, but is usually 0.1 to 24 hours, preferably 0.5 to 10 hours, particularly preferably 0.5 to 2 hours. The polymerization time is affected by the polymerization temperature, catalyst, etc., but if it is longer than necessary, the strength of the obtained PAS is reduced, or a PAS in which the low molecular weight component is increased due to partial decomposition of the PAS is obtained. In some cases, it may be disadvantageous both economically and in physical properties.
[0033]
In the polymerization method of the present invention, as a method for preventing the phase separation of the polymerization solution at the time of polymerization and maintaining a uniform phase, in addition to setting the polymerization temperature appropriately, the polymerization by-product salt in the polymerization solution is reduced, or moisture It is mentioned to set the amount appropriately.
As a method for reducing the polymerization byproduct salt, for example, a prepolymer washed with a polymerization solvent such as water or NMP can be used.
[0034]
The amount of water in the polymerization solution is not particularly limited as long as the effects of the present invention are not impaired, but it is preferably within 10%, particularly within 5%, assuming that the weight of the reaction solution is 100%. If the water content exceeds 10%, the polymerization solution may phase separate.
Further, the dihaloaromatic compound contained in the polymerization solution immediately after adding the branching agent or the like to the prepolymer is 30 mol% or less based on the total number of moles of the prepolymer and the dihaloaromatic compound. More preferably, it is 20 mol% or less, and particularly preferably 10 mol% or less.
[0035]
If there are many dihaloaromatic compounds in the polymerization solution, the molecular weight distribution of the final PAS will be widened, the heat resistance of the PAS will decrease, and a large amount of polymerization by-product salts may be generated, causing the polymerization solution to phase separate. There is.
In order to obtain a polymerization solution with a small amount of dihaloaromatic compound, when synthesizing the prepolymer, the conversion rate of the dihaloaromatic compound is preferably 70 mol% or more, more preferably 80 mol% or more, particularly preferably. May be reacted until it exceeds 90 mol%, or after prepolymer is precipitated from a solution containing the prepolymer, it may be sufficiently washed with a polymerization solvent such as water or NMP, or an organic solvent such as methylene chloride or acetone. .
[0036]
The method for extracting the PAS of the present invention from the reaction solution after completion of the polymerization may be a known method. For example, a phase separation agent such as water is added and cooled to take out as granular and / or powdered PAS, a phase separation agent such as water is added, and the phase separation agent is maintained at a temperature at which PAS does not precipitate. And a method of taking out in the PAS phase (liquid phase) from the lower part of the reaction vessel.
[0037]
The extracted PAS can be purified by a known method such as washing with an organic solvent such as water or NMP and then removing the washing solution by a flash method.
〔Example〕
Hereinafter, the present invention will be described more specifically with reference to examples.
The evaluation was performed by the following method.
(1) Melt viscosity (η _m )
Using a capillary rheometer (Equivalent to Capillograph type I, manufactured by Toyo Seiki Co., Ltd.), the above calculation method was used under the conditions of a resin temperature of 300 ° C., an orifice radius of 1 mm, and an orifice length of 40 mm.
(2) Branching degree index (N value)
The value of the melt viscosity at each shear rate was determined at 5 points or more, and log η = f (log γ) was determined as a function of log γ by the least square method for each log value, and the branching index N value was calculated by the method described above. .
(3) Bending strength (F)
A value obtained by pressing a sample at 320 ° C. and 50 kgf / cm ^{2 into} a length of 50 mm × 2 mm, and annealing at 220 ° C. for 2 hours, measured at a span of 40 mm and a test speed of 1.0 mm / min. (Shimadzu Corporation, precision universal testing machine: Shimadzu Autograph IS-5000B used)
[Example 1]
A stainless steel 10 liter autoclave was charged with 540.8 g of lithium sulfide, 5.1 liter of NMP, 1695.7 g of paradichlorobenzene (PDCB), 5.3 g of lithium hydroxide, and 318.1 g of water, and the temperature was raised to 260 ° C. in a nitrogen atmosphere. And reacted for 0.5 hour to synthesize a prepolymer.
[0038]
The prepolymer was separated from the reaction solution, washed with NMP, then water and acetone, and dried under reduced pressure at 120 ° C. for 8 hours. The solution viscosity of the obtained prepolymer was 0.14 dl / g.
Subsequently, 51.84 g of prepolymer, 0.55 g of lithium sulfide, 0.73 g of trichlorobenzene (TCB), 0.6 g of lithium hydroxide, 8.65 g of water, and 216.32 g of NMP were charged in a 1 liter autoclave. The polymer was synthesized by reacting at 1 ° C. for 1 hour (main polymerization). From the time when the charged polymerization components were dissolved in the polymerization solvent until the end of the polymerization, the polymerization solution did not phase separate.
[0039]
After the polymerization solution was cooled to precipitate the polymer, the polymerization solvent was separated using a centrifuge. The obtained polymer was washed with NMP, then water and acetone, and dried under reduced pressure at 120 ° C. for 8 hours. The obtained polymer had a melt viscosity of 364 Pa · s, an N value of 1.49, and F of 124 MPa.
[Example 2]
A polymer was synthesized in the same manner as in Example 1 except that the amount of lithium sulfide added to the prepolymer was changed to 0.48 g and the amount of TCB was changed to 0.64 g. The obtained polymer had a melt viscosity of 127 Pa · s, an N value of 1.23, and F of 80 MPa.
[Example 3]
A prepolymer with a solution viscosity of 0.17 dl / g was synthesized with a prepolymer synthesis time of 1 hr and used for the next polymerization, except that the amount of lithium sulfide was changed to 0.34 g and the amount of TCB was changed to 0.45 g. Were operated in the same manner as in Example 1 to synthesize a polymer. The obtained polymer had a melt viscosity of 243 Pa · s, an N value of 1.30, and F of 102 MPa.
[Example 4]
The prepolymer synthesis time was 0.1 hr and a prepolymer with a solution viscosity of 0.11 dl / g was synthesized and used for the next polymerization. The amount of lithium sulfide was changed to 0.75 g and the amount of TCB was changed to 0.91 g. A polymer was synthesized in the same manner as in Example 1 except that. The obtained polymer had a melt viscosity of 135 Pa · s, an N value of 1.33, and F of 76 MPa.
[Example 5]
A polymer was synthesized in the same manner as in Example 1 except that the amount of TCB added to the prepolymer was changed to 0.54 g. The obtained polymer had a melt viscosity of 67 Pa · s, an N value of 1.11 and F of 45 MPa.
[Example 6]
A polymer was synthesized in the same manner as in Example 1 except that 0.83 g of thiophenol was further added to the prepolymer. The obtained polymer had a melt viscosity of 111 Pa · s, an N value of 1.18, and F of 82 MPa.
[Example 7]
A polymer was synthesized in the same manner as in Example 1 except that the main polymerization time was 0.5 hour. The obtained polymer had a melt viscosity of 135 Pa · s, an N value of 1.33, and F of 76 MPa.
[Example 8]
A polymer was synthesized in the same manner as in Example 1 except that the amount of TCB added to the prepolymer was changed to 0.45 g and the main polymerization time was changed to 2 hours. The obtained polymer had a melt viscosity of 364 Pa · s, an N value of 1.32, and F of 72 MPa.
[Example 9]
A polymer was synthesized in the same manner as in Example 1 except that lithium hydroxide added to the prepolymer was changed to 0.24 g. The obtained polymer had a melt viscosity of 236 Pa · s, an N value of 1.38, and F of 104 MPa.
[Example 10]
A polymer was synthesized in the same manner as in Example 1 except that the amount of TCB added to the prepolymer obtained in Example 3 was changed to 0.54 g. The obtained polymer had a melt viscosity of 696 Pa · s, an N value of 1.44, and F of 118 MPa.
[Comparative Example 1]
A 1 liter autoclave was charged with 110.26 g of PDCB, 34.46 g of lithium sulfide, 1.63 g of TCB, 24.53 g of water, and 334.21 g of NMP, and reacted at 260 ° C. for 3 hours in a nitrogen atmosphere to synthesize a polymer.
[0040]
The polymer was separated from the reaction solution, washed with NMP, then water and acetone, and dried under reduced pressure at 120 ° C. for 8 hours. The obtained polymer had a melt viscosity of 179 Pa · s, an N value of 1.40, and F of 41 MPa.
[Comparative Example 2]
The same operation as in Comparative Example 1 was performed except that the amount of TCB was changed to 0.69 g and the amount of water was changed to 10.09 g. The obtained polymer had a melt viscosity of 245 Pa · s, an N value of 1.30, and F of 58 MPa.
[Comparative Example 3]
The same operation as in Comparative Example 1 was performed except that TCB was not added and the amount of water was changed to 10.09 g. The polymer obtained had a melt viscosity of 100 Pa · s, an N value of 1.01, and F of 112 MPa.
[Comparative Example 4]
After 1 hour at 260 ° C., the same procedure as in Comparative Example 1 was conducted except that 1.63 g of TCB was added and the reaction was continued for another hour. The obtained polymer had a melt viscosity of 189 Pa · s, an N value of 1.34 and F of 55 MPa.
[0041]
The above results are shown in Table 1, FIG. 1 and FIG.
[0042]
[Table 1]

[0043]
[Figure 1]
[0044]
[Figure 2]
In FIG. 1 and FIG. 2, the suffixes ◆ (example) and Δ, × (comparative example) mean No of the example and comparative example, respectively. Δ is a comparative example in which a branching agent is added at the time of charging, and x is a comparative example in which a branching agent is added during the polymerization.
In FIG. 1, both Example 3 and Comparative Example 4 are branched PASs that satisfy the formula (1), and have substantially the same melt viscosity and N value. Although it is predicted from the prior art that both branched PASs have the same bending strength, in fact, as shown in FIG. 2, Comparative Example 4 shows a significantly lower bending strength than Example 3.
[0045]
In FIG. 1, Example 9 and Comparative Example 1 both satisfy the formula (1), the N value is about the same, and the melt viscosity is higher in Example 9. From the known tendency, it is predicted that the bending strength of Example 9 is somewhat higher than that of Comparative Example 1. However, actually, as shown in FIG. 2, Example 9 shows a bending strength about 2.5 times that of Comparative Example 1, and is an unpredictable value.
[0046]
【The invention's effect】
As described above, the PAS of the present invention is excellent in mechanical strength, has a very small amount of burrs during molding, and has excellent flow characteristics. It can be used as a molding material.
[Brief description of the drawings]
FIG. 1 is a graph showing the relationship between melt viscosity and N value of PAS.
FIG. 2 is a graph showing the relationship between PAS solution viscosity and bending strength.

Claims (3)

A prepolymer of polyarylene sulfide having a solution viscosity of 0.05 to 0.25 dl / g, a solution in which the prepolymer is dissolved, or a slurry containing the prepolymer, a branching agent, and optionally a polymerization solvent and / or Alternatively, a sulfur source is added, and polymerization is performed at a temperature of 230 to 290 ° C. in a state where the polymerization solution is not phase-separated to obtain polyarylene sulfide satisfying the following formulas (1) to (4). A method for producing polyarylene sulfide.
N ≧ 0.3 × log ₁₀ (η _m ) +0.55 (1)
N ≧ 1.10 (2)
F ≧ 57 × log ₁₀ (η _m ) −60 (3)
F ≧ 40 (4)
[In the above formulas, F is bending strength (unit: MPa), N is branching index, and η _m is melt viscosity (unit: Pa · s). ]   The method for producing a polyarylene sulfide according to claim 1, wherein the amount of the dihaloaromatic compound in the polymerization solution is 30 mol% or less based on the total number of moles of the prepolymer and the dihaloaromatic compound. The method for producing a polyarylene sulfide according to claim 1 or 2, wherein the polyarylene sulfide has a melt viscosity η _m of 20 to 1500 Pa · s.

Images