JP3929188B2 - Method for producing polycarbonate resin granules - Google Patents

Description

【００１２】
[式中Ｗは炭素数１〜９の置換若しくは非置換アルキレン基、アルキリデン基、シクロアルキリデン基、単結合、−Ｓ−、−ＳＯ−、−ＳＯ₂−、−Ｏ−又は−ＣＯ−であり、Ｘ_１及びＸ_２は独立して炭素数１〜３のアルキル基又はハロゲン原子であり、ｍ及びｎは独立して０，１又は２である。]で表される二価フェノールより選ばれる一種又は二種以上の二価フェノールであり、特に２，２−ビス（４−ヒドロキシフェニル）プロパン（通称ビスフェノールA）が好ましく使用される。その他の二価フェノールとしては、例えばビス（４−ヒドロキシフェニル）メタン、１，１−ビス（４−ヒドロキシフェニル）エタン、１，１−ビス（４−ヒドロキシフェニル）シクロヘキサン、２，２−ビス（４−ヒドロキシ−３−メチルフェニル）プロパン、ビス（４−ヒドロキシフェニル）スルホン、ビス（４−ヒドロキシフェニル）エーテル、４，４−ジヒドロキシジフェニル等があげられ、更には２，２−ビス（３，５−ジブロモ−４−ヒドロキシフェニル）プロパンの如きハロゲン化ビスフェノール類等があげられる。カーボネート前駆体としてはカルボニルハライド、ジアリールカーボネート、ハロホルメート等があげられ、具体的にはホスゲン、ジフェニルカーボネート、二価フェノールのジハロホルメート等があげられる。
【００１３】
上記二価フェノールとカーボネート前駆体を反応させて芳香族ポリカーボネート樹脂を製造するに当たっては、必要に応じて触媒、分子量調整剤、酸化防止剤等を使用してもよく、また芳香族ポリカーボネート樹脂は例えば三官能以上の多官能性芳香族化合物を共重合した分岐ポリカーボネート樹脂であっても、二種以上の芳香族ポリカーボネート樹脂の混合物であってもよい。芳香族ポリカーボネート樹脂の分子量については任意のものを用いることができ、例えば二価フェノールとしてビスフェノールＡ、カーボネート前駆体としてホスゲンを用いて芳香族ポリカーボネート樹脂を得た場合、濃度０．７ｇ／ｄＬ塩化メチレン溶液により温度２０℃で測定した比粘度（η_sp）が０．０１５〜３．０のものが好ましく、０．１９〜１．５のものが特に好ましい。
【００１４】
本発明の芳香族ポリカーボネート樹脂粉粒体の製造方法は、有機溶媒を使用する溶液法によって得られた芳香族ポリカーボネート樹脂を使用するのに極めて適している。すなわち、本発明は、二価フェノールとホスゲンとを有機溶媒中で反応させて得られた芳香族ポリカーボネート樹脂からその粉粒体を得るのに適している。この際使用される有機溶媒は芳香族ポリカーボネート樹脂の良溶媒であって、水と非混和性の溶媒である。
【００１５】
本発明でいう有機溶媒とは、少なくとも１種の良溶媒を主たる溶媒とし、これに貧溶媒及び／又は非溶媒が一部混和されていてもよい。ここでいう良溶媒、貧溶媒及び非溶媒とは、W.F.CHRISTOPHER, D.W.FOX著「ポリカーボネート」、１９６２年、３２〜３３頁の表３−１における分類中の”Good Solvent”及び”Fair Solvent”に該当する溶媒が良溶媒であり、”Poor Solvent”、”Very Poor Solvent”及び”Weak Solvent”に該当する溶媒が貧溶媒であり、”Nonsolvent”に該当する溶媒が非溶媒である。良溶媒の代表的な例としては塩化メチレン、テトラクロロエタン等のハロゲン化炭化水素があげられ、貧溶媒の代表的な例としてはベンゼン、トルエン、アセトン等があげられ、非溶媒の代表的な例としてはヘキサン、ヘプタン等があげられる。かかる貧溶媒及び／又は非溶媒は単独で用いても、二種以上併用してもよい。
【００１６】
本発明のポリカーボネート樹脂粉粒体の製造方法においては、まず、ポリカーボネート樹脂と有機溶媒との割合が重量比で９０：１０〜３５：６５であり、且つポリカーボネート樹脂と水との割合がポリカーボネート樹脂１００重量部に対して水５重量部以上である、ポリカーボネート樹脂、有機溶媒及び水を含有するスラリー又は湿潤ペーストを調整する。ここでいう有機溶媒とは、前述したようにポリカーボネート樹脂の良溶媒を意味する。またスラリーとはポリカーボネート樹脂粒子が有機溶媒及び水よりなる混合媒体中に懸濁した流動性を有する状態のものであり、湿潤ペーストとはこのスラリーよりも混合媒体の量が少なく、流動しないか或いは流動性が低い状態のものをいう。以下本明細書中で、この”スラリー又は湿潤ペースト”を総称として”出発混合物”と略称することがある。
【００１７】
この出発混合物に含有される有機溶媒量は、ポリカーボネート樹脂と有機溶媒との割合が重量比で９０：１０〜３５：６５、好ましくは８５：１５〜６０：４０の範囲である。この有機溶媒の含有量が１０重量％未満の場合、押出機の負荷が大きくなって微粉砕が困難になり、目的とする大きさの微粉体が得られ難くなり、その結果として有機溶媒の含有量が極めて少ないポリカーボネート樹脂粉粒体が得られなくなる。一方有機溶媒の含有量が６５重量％を超えると、ポリカーボネート樹脂を粒子として取り扱うこと自体が困難となるので望ましくない。出発混合物を調製する際、ポリカーボネート樹脂粒子含有混合物(予備混合物)中の有機溶媒の含有量が適当な範囲でない場合は、有機溶媒の添加或いは除去によって前記の適当な範囲に調製すればよい。有機溶媒含有量が少ない場合、所定量となる量の有機溶媒或いはポリカーボネート樹脂溶液を前記予備混合物中に添加すればよい。一方予備混合物中の有機溶媒量が多過ぎる場合、ポリカーボネート樹脂粒子又は有機溶媒含有量の少ないスラリー或いは湿潤ペーストを予備混合物へ添加してもよい。また、有機溶媒含有量の多いスラリーを加熱して余分の有機溶媒を除去してもよい。
【００１８】
出発混合物中の水の含有量は、ポリカーボネート樹脂１００重量部に対して水５重量部以上である。この水の含有量は５〜２０００重量部の範囲が好ましく、７〜１０００重量部の範囲が特に好ましい。出発混合物中の水の含有量が５重量部よりも少ないと、ポリカーボネート樹脂の微粉砕が難しくなり、結果的に残留有機溶媒量の低い粉粒体が得られなくなる。水量の上限は微粉砕装置により異なり一概に制限できないが、極端に多くなると微粉砕し難くなることがあり、また、コスト上不利になる。従って水の含有割合は、押出機の運転操作性並びに微粉砕された樹脂微粉体の接着性の点を考慮して決定することが望ましく、通常ポリカーボネート樹脂に対して５〜２０００重量部の範囲が好ましく、７〜１０００重量部の範囲が特に好ましい。水量が不足したときは、水又は水量の多い樹脂スラリーを加えればよく、微粉砕時に加えてもよい。前記範囲において、水が多い場合は、概して出発混合物はスラリーの形態であり、一方水が少ない場合は、湿潤ペーストの形態を呈する。
【００１９】
この出発混合物中のポリカーボネート樹脂粒子の大きさ及び粒度分布は特に制限されるわけではなく、微粉砕工程に供給できるものであればよい。供給し難いときは粉砕すればよい。例えば溶液法によって得られた反応混合物から形成されたスラリーは、そのまま使用することができる。一般に出発混合物中の樹脂粒子の大きさは０．１〜５０ｍｍ程度が適当である。
【００２０】
上記のように調製された出発混合物は、押出機に連続的に供給され、押出機内で微粉砕化される（微粉砕工程）。この微粉砕工程は、出発混合物であるスラリーまたは湿潤ペースト中のポリカーボネート樹脂粒子を粒径が５０μｍ以下の微粉体になるように、主としてシェアーをかけて粉砕する工程であって、その操作は微粉砕化する機能を備えた押出機を使用して実施される。その押出機としては、得られる微粉体の９０％以上、特に９５％以上が５０μｍ以下の粒径、好ましくは４０μｍ以下の粒径、特に好ましくは３０μｍ以下の粒径となるように粉砕する機能を有するものが好ましい。粉砕された微粒子の下限は制限されないが、一般的には約０．３μｍである。押出機の形式としては、例えば単軸若しくは多軸のスクリュ式押出機、プランジャー式押出機及びインナースクリュを有する射出成形機の如き機能を有する押出機が挙げられる。
【００２１】
これらの押出機の中で、二軸のスクリュ式押出機を使用するのが好ましい。また、ベント型押出機の使用は、ベント口から水を供給することにより、押出機内での出発混合物の調製及び微粉砕を同時に実施することが可能になる。押出機によりポリカーボネート樹脂の微粉砕を実施する際、ポリカーボネート樹脂の濃度及び操作条件によっては、シリンダーの内温の上昇による内圧の上昇によって、樹脂の溶解や溶融などのトラブルが生じることがある。かかるトラブルを避けるために温度調節機能を有するジャケット付きシリンダー及び／又はスクリュを使用するのが好ましい。又、押出機には圧縮部付きスクリュも設けてもよい。
【００２２】
更に押出機のシリンダーの全域或いは一部にパンチプレート又はスリットを設けて排水しうるようにすることもでき、またグランド側に排水しうる機構を設けても良い。出発混合物中の水量が大過剰にあるときは、その大部分は押出し方向と反対側に分離されるか、前記パンチプレート又はスリットにより分離される。その際グランド及びパンチプレートの目開きやスリットのクリアランスは特に制限されるものではないが、樹脂粒径によって適宜選択すればよい。
【００２３】
本発明において、前記微粉砕工程において微粉砕されたポリカーボネート樹脂の微粉体は、さらに押出機内で加圧されて押出される。押出された粉粒体は微粉体の凝集体である（以下、この粉粒体を凝集体といい、この工程を凝集体形成工程という）。この凝集体形成工程は微粉体が凝集体となるような圧力に加圧され、且つポリカーボネート樹脂と有機溶媒との割合が重量比で９５：５〜３５：６５、好ましくは８５：１５〜６０：４０の範囲に調製し、その上ポリカーボネート樹脂と水との割合がポリカーボネート樹脂１００重量部に対して水５〜１２０重量部、好ましくは７〜７０重量部の範囲に調製することにより実施される。この凝集体形成工程における圧力は、微粉体が部分的に結合して凝集体のブロックが形成されるような圧力であり、この凝集体を形成する微粉体の大きさは、その折った断面を電子顕微鏡による写真を撮った場合、約１０００倍の拡大写真を目視により容易に確認できるものである。
【００２４】
凝集体形成工程において、ポリカーボネート樹脂微粉体の９０％以上が５０μｍ以下の粒径を保持しうる温度で実施することが好ましい。この温度は圧力、有機溶媒量により変化し一概に決められないが、高温になると微粉体の膨潤、溶解或いは軟化、溶融によりその９０％以上が５０μｍ以下の粒径を保持できず、微粉体が相互に密着し連続層となり、残留有機溶媒の極めて少ないポリカーボネート樹脂粉粒体が得られなくなることがある。
【００２５】
この凝集体形成工程における加圧手段は、微粉砕工程に引き続いて押出機内で連続して実施される。特に、押出機の出口手前にシールリングを設けた押出機を使用し、押出機内で微粉砕された微粉体がシールリングを通過する際に、加圧されて凝集体を形成し、押出機出口より押出される方法を採用するのが好ましい。また、押出機の出口に細孔又はスリットを有するダイを設けた押出機を使用し、押出機内で微粉砕された微粉体が押出機の出口に移動するに従い、次第に加圧され凝集体を形成し、凝集体は細孔又はスリットから押出される方法を採用することもできる。
【００２６】
凝集体形成工程において有機溶媒の含有割合は特に調整する必要はなく、微粉砕工程から得られた微粉体中の有機溶媒含有量であって差し支えない。すなわち、有機溶媒の含有量は、ポリカーボネート樹脂と有機溶媒との割合が重量比で９５：５〜３５：６５、好ましくは９０：１０〜６０：４０の範囲であり、かかる量を保持することによって得られる凝集体は適度な形状保持性を有する。５重量％未満になると凝集体がもろくなり、６５重量％より多くなると目的とする微粉体を保持できなくなる。
【００２７】
また、凝集体形成工程における水の含有割合は、ポリカーボネート樹脂１００重量部に対して水５〜１２０重量部、好ましくは７〜７０重量部の範囲であり、５重量部より少ないと押出時に微粉体の形状が破壊され凝集体が得られなくなり、１２０重量部より多くなると凝集体がもろくなる。
【００２８】
押出機によりポリカーボネート樹脂の微粉体及び凝集体の形成を実施する際、シリンダーの内圧はシェアーのかかる部分及び加圧する部分が特に高くなるが、この背圧によって出発混合物を充分に輸送できなくなることがある。このとき、吐出量の減少、更には前記排水機構を有する押出機を使用した場合は、排水機構であるパンチプレート又はスリット等からポリカーボネート樹脂が水と同時に排出されてしまうというトラブルが生じることがある。かかるトラブルを避けるためには出発混合物を輸送するためのスクリュ表面の十点平均粗さで表した表面粗度が３μｍ以下、好ましくは０．０１〜３μｍ、より好ましくは０．１〜３μｍ、さらに好ましくは１〜３μｍであることが必要である。表面粗度が３μｍを超えると、押出機の処理能力が安定化せず好ましくない。かかるスクリュの素材としては、ステンレス、窒化鋼が好ましく使用される。また、表面粗度が３μｍを超えるスクリュを研磨などを行ない上記範囲に調整して使用することもできる。
【００２９】
本発明において前記凝集体形成工程で得られた凝集体は、粉砕又は切断され、乾燥される。この実施される順序は任意でよいが、一般的には粉砕又は切断の後に乾燥するのが望ましい。この工程における乾燥は、凝集体に含まれる有機溶媒及び水の両者を脱離することを意味する。
【００３０】
この工程について説明すると、押出機より押出されたポリカーボネート樹脂粉粒体の凝集体は任意の方法で切断され、特に押出機直後に設けたスクリーン付ハンマーミルにより粉砕することによって粒径の揃ったポリカーボネート樹脂粉粒体を得る方法は好ましい例である。この際、ポリカーボネート樹脂粉粒体の粒径はスクリーン付ハンマーミルのスクリーンの目開きを調整することにより調整可能である。また、押出機出口に細孔又はスリットを有するダイを付設し、押出されたストランド状又はリボン状の凝集体をダイ面に対して平行になるように取付けたプロペラを回転させることなどの方法により切断してもよい。凝集体の長さはプロペラの取付け位置や回転速度等で調整可能である。
【００３１】
得られたポリカーボネート樹脂凝集体は、脱液する必要はなく連続的及び／又は回分的に乾燥することが可能である。乾燥は乾燥工程のみによって行なってもよく、必要に応じて残留有機溶媒の沸点以上の液体等と混合し蒸留する方法及び水蒸気と接触させる方法等任意の脱有機溶媒処理を行なった後乾燥してもよい。かかる水蒸気と接触させる方法により最終的に残留する有機溶媒量を更に低下させることができる。得られたポリカーボネート樹脂凝集体の残留有機溶媒量が多く凝集体が崩れ易い場合はシェアーのかからない装置、例えば熱風循環型乾燥機やスチームチューブドライヤー、パウヒーター、ホッパードライヤー、タワードライヤー等を用いて乾燥するか又はこれらの装置で予め乾燥した後更にパドルドライヤー、マルチフィンドライヤー等の乾燥装置を用いて乾燥するのが好ましい。特にガラス転移温度（Ｔｇ）以上の温度で凝集体を乾燥する時は、シェアーのかからない装置が好ましい。これらの乾燥機は単独で用いても各々組合わせて用いてもよい。かくして得られたポリカーボネート樹脂粉粒体には必要に応じて任意の安定剤、添加剤、充填剤等を加えてもよい。
【００３２】
【実施例】
以下に本発明の実施例を示して更に説明する。なお、実施例中における％は重量％であり、塩化メチレン含有量は塩素含有量を全有機ハロゲン分析装置［三菱化成（株）製 ＴＯＸ］により分析して求め、塩化メチレン量に換算した。また、表面粗度はスクリュの溝の部分を二次元・三次元表面粗さ測定器［（株）小坂研究所製 ＳＵＲＦＣＯＲＤＥＲ］を用いて十点平均粗さを求めた。
【００３３】
［実施例１］
（Ａ）ビスフェノールＡとホスゲンから常法によって得た比粘度０．４２６のポリカーボネート樹脂の２０％塩化メチレン溶液を、４２℃に保持した温水を仕込んだニーダーに投入して塩化メチレンを除去した後、粉砕して液温が３８℃のスラリーを得た。このスラリー中のポリカーボネート樹脂粉粒体と塩化メチレンとの割合は７５：２５であり、ポリカーボネート樹脂粉粒体１００部に対して水１００部であった。
【００３４】
（Ｂ）先端から全長の１／３の部分に、直交ニーディングディスク、逆ニーディングディスクとシールリングを各１組取り付けた径が６５ｍｍ、Ｌ／Ｄが１４、溝深さが１２．５ｍｍ、表面粗度が２．６μｍである窒化鋼製のスクリュを有し、シリンダーに分離水排出スリットと温度調節用ジャケットを設けた二軸押出機を、スクリュ回転数を１５６ｒｐｍに設定して運転した。実施例１（Ａ）で得たスラリーを押出機に連続的に供給して脱液、微粉砕し、押出してポリカーボネート樹脂微粉体の凝集体を得た。この凝集体は、凝集体と塩化メチレンとの割合が８９：１１であり、凝集体１００部に対して水１３部であった。また、押出における最大吐出量は４００ｋｇ／時、押出機比電力は０．０５９ｋＷ時／ｋｇであった。この凝集体を熱風循環型乾燥機により１４５℃で６時間乾燥して、残留塩化メチレン量が４ｐｐｍの樹脂粉粒体を得た。
【００３５】
［比較例１］
先端から全長の１／３の部分に、直交ニーディングディスク、逆ニーディングディスクとシールリングを各１組取り付けた径が６５ｍｍ、Ｌ／Ｄが１４、溝深さが１２．５ｍｍ、表面粗度が３．１μｍである窒化鋼製のスクリュを有し、シリンダーに分離水排出スリットと温度調節用ジャケットを設けた二軸押出機を、スクリュ回転数を１５６ｒｐｍに設定して運転した。実施例１（Ａ）で得たスラリーを押出機に連続的に供給して脱液、微粉砕し、押出してポリカーボネート樹脂微粉体の凝集体を得た。この凝集体は、凝集体と塩化メチレンとの割合が９０：１０であり、凝集体１００部に対して水１２部であった。また、押出における最大吐出量は３４０ｋｇ/時、押出機比電力は０．０７８ｋＷ時／ｋｇであった。この際、分離水排出スリットより樹脂が洩れ出し、運転が困難となった。この凝集体を熱風循環型乾燥機により１４５℃で６時間乾燥して、残留塩化メチレン量が１３ｐｐｍの樹脂粉粒体を得た。
【００３６】
【発明の効果】
本発明によれば、通常の乾燥により残留溶媒が極めて少なく、且つ粒径が揃っていて取り扱い易い極めて優れたポリカーボネート樹脂粉粒体を安定して生産性良く製造でき、その奏する工業的効果は格別なものである。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing a polycarbonate resin granular material. More specifically, the present invention relates to a method for producing a polycarbonate resin particle having a very small amount of residual organic solvent and having a uniform particle size stably and with high productivity.
[0002]
[Prior art]
Polycarbonate resins are usually produced by a so-called solution method in which an alkaline aqueous solution of a dihydric phenol and phosgene are reacted in the presence of an organic solvent such as methylene chloride, and an organic solvent solution of the resulting polycarbonate resin (hereinafter referred to as a polycarbonate resin solution) is used for After passing through the granulation process which removes a solvent and makes it a granule, it is used for a drying process. As a method of obtaining a granular material by removing an organic solvent from a polycarbonate resin solution, for example, a method of bringing a polycarbonate resin solution into contact with hot water or water vapor to form flakes or granulate (Japanese Patent Publication No. 36-11231, Japanese Patent Publication No. 36-11231). Japanese Patent Publication No. 40-9843, Japanese Patent Publication No. 45-9875, Japanese Patent Publication No. 48-43752, Japanese Patent Publication No. 54-122393, a method of gelling by concentration or cooling (Japanese Patent Publication No. 36-36). No. 21033, Japanese Patent Publication No. 38-22497, Japanese Patent Publication No. 40-12379, Japanese Patent Publication No. 45-9875, Japanese Patent Publication No. 47-41421, Japanese Patent Publication No. 51-41048, etc.) Yes. However, many organic solvents still remain in the granular material (including flakes) obtained by these methods, and it is difficult to sufficiently remove the residual organic solvent by ordinary drying.
[0003]
As a method for removing the residual organic solvent, a method of mixing and distilling with warm water having a boiling point equal to or higher than the boiling point of the residual organic solvent has been proposed. However, this method heats not only the organic solvent but also warm water, which increases the energy cost. Moreover, several hundred to several thousand ppm of the organic solvent still remains in the granular material obtained by this method. In order to further reduce this residual organic solvent, it must be dried at a high temperature for a long time or pelletized with an extruder equipped with a vacuum vent, and still tens to hundreds of ppm of organic solvent remains and is obtained. The product is not immune to adverse effects on heat resistance, hue, and physical properties.
[0004]
Furthermore, as a method for producing a polycarbonate resin granule having a small amount of residual organic solvent, a method of adding a non-solvent or a poor solvent to a polycarbonate resin slurry obtained by the reaction or a polycarbonate resin slurry in which the organic solvent remains, or an organic solvent is used. A method for extracting the remaining polycarbonate resin granules with a poor solvent (Japanese Patent Publication No. 55-1298, Japanese Patent Publication No. 63-278929, Japanese Patent Publication No. 64-6020, Japanese Patent Publication No. 5-12371), etc. Has been proposed. In these methods, although the organic solvent is sufficiently removed, a large amount of non-solvent or poor solvent remains, and this residual non-solvent or poor solvent is dried at a high temperature for a long time as well as normal drying. However, it is difficult to remove them sufficiently. Moreover, if the drying is strengthened in this manner, not only the operation becomes complicated, but also the molecular weight of the polycarbonate resin is lowered, the hue is deteriorated, and foreign matters are mixed.
[0005]
Further, as a method for producing a granular polycarbonate resin particle having a large bulk density and a uniform particle size, a method of extruding an undried solid polycarbonate resin with an extruder provided with a die having a large number of pores (Japanese Patent Application Laid-Open No. 2005-318707) No. 62-169605) has been proposed. However, this method has a problem that some of the obtained polycarbonate resin particles cannot sufficiently remove the residual solvent and the amount of residual solvent varies.
[0006]
As a method for improving these, the present applicant has proposed a solid polycarbonate containing an organic solvent and water as a method for producing a granular polycarbonate resin granule having a small amount of residual organic solvent and a large bulk density and a uniform particle size. An aqueous slurry or wet paste of resin is continuously supplied to the extruder, and liquid aggregates, fine pulverization, and pressurization are performed in the extruder to form aggregates of the polycarbonate resin fine powder. A method was proposed in which the aggregates were pulverized or cut and dried in any order (WO95 / 08585). The amount of the organic solvent remaining in the granular material obtained by this method is as low as several tens of ppm or less, and the resulting product is stable and good in heat resistance, hue, physical properties and the like. However, when this process is operated for a long period of time, the resin may leak from the slit for discharging the separated water, the processing amount (discharge amount) may be reduced, or the transportation failure with the extruder screw may occur depending on the conditions. In that case, since the load on the extruder increases and it becomes impossible to operate continuously, there is a demand for a method with higher productivity and a stable discharge amount.
[0007]
[Problems to be solved by the invention]
An object of the present invention is to provide a method for producing a polycarbonate resin granule having a very small residual organic solvent and having a uniform particle diameter in a stable and high productivity.
[0008]
As a result of earnest research to achieve the above-mentioned object, the present inventor continuously supplied an aqueous slurry or wet paste of a solid polycarbonate resin containing an organic solvent and water to the extruder, and devolatilized the liquid in the extruder. In the method of forming an aggregate of polycarbonate fine powder by pulverization and further pressurization, it was found that the processing capability of the extruder can be stabilized by adjusting the surface roughness of the extruder screw, and the present invention has been achieved. .
[0009]
[Means for Solving the Problems]
That is, according to the present invention, the ratio between the polycarbonate resin and the organic solvent is 90:10 to 35:65 by weight, and the ratio between the polycarbonate resin and water is 5 wt. The slurry or wet paste containing polycarbonate resin that is at least a part is continuously fed to the extruder, and the slurry or wet paste is sheared in the extruder to form a fine powder of the polycarbonate resin, and then obtained. The polycarbonate resin fine powder was pressed, the ratio of the polycarbonate resin to the organic solvent was 95: 5 to 35:65 by weight, and the ratio of the polycarbonate resin to water was 100 parts by weight of the polycarbonate resin. A method of forming an aggregate of polycarbonate resin fine powder having 5 to 120 parts by weight of water In method for producing a polycarbonate resin powder or granular material is surface roughness, expressed in ten-point average roughness is characterized by using the following extruder screw 3μm is provided.
[0010]
The polycarbonate resin used in the present invention is a resin usually used as an engineering resin, and is an aromatic polycarbonate resin obtained by reacting a dihydric phenol and a carbonate precursor. The dihydric phenol used here is represented by the following general formula (1)
[0011]
[Chemical 1]

[0012]
[W is a substituted or unsubstituted alkylene group having 1 to 9 carbon atoms, an alkylidene group, a cycloalkylidene group, a single bond, -S-, -SO-, -SO. ₂ -, -O- or -CO-, and X ₁ And X ₂ Is independently an alkyl group having 1 to 3 carbon atoms or a halogen atom, and m and n are independently 0, 1 or 2. ] One or two or more dihydric phenols selected from dihydric phenols represented by the formula: 2,2-bis (4-hydroxyphenyl) propane (commonly called bisphenol A) is preferably used. Examples of other dihydric phenols include bis (4-hydroxyphenyl) methane, 1,1-bis (4-hydroxyphenyl) ethane, 1,1-bis (4-hydroxyphenyl) cyclohexane, 2,2-bis ( 4-hydroxy-3-methylphenyl) propane, bis (4-hydroxyphenyl) sulfone, bis (4-hydroxyphenyl) ether, 4,4-dihydroxydiphenyl, and the like. And halogenated bisphenols such as 5-dibromo-4-hydroxyphenyl) propane. Examples of the carbonate precursor include carbonyl halide, diaryl carbonate, haloformate, and the like, and specifically, phosgene, diphenyl carbonate, dihaloformate of dihydric phenol, and the like.
[0013]
In producing the aromatic polycarbonate resin by reacting the dihydric phenol and the carbonate precursor, a catalyst, a molecular weight adjusting agent, an antioxidant or the like may be used as necessary. It may be a branched polycarbonate resin copolymerized with a trifunctional or higher polyfunctional aromatic compound, or a mixture of two or more aromatic polycarbonate resins. Any molecular weight of the aromatic polycarbonate resin can be used. For example, when the aromatic polycarbonate resin is obtained using bisphenol A as the dihydric phenol and phosgene as the carbonate precursor, the concentration is 0.7 g / dL of methylene chloride. Specific viscosity (η measured by solution at a temperature of 20 ° C. _sp ) Is preferably 0.015 to 3.0, particularly preferably 0.19 to 1.5.
[0014]
The method for producing an aromatic polycarbonate resin granule of the present invention is extremely suitable for using an aromatic polycarbonate resin obtained by a solution method using an organic solvent. That is, this invention is suitable for obtaining the granular material from the aromatic polycarbonate resin obtained by making bihydric phenol and phosgene react in an organic solvent. The organic solvent used at this time is a good solvent for the aromatic polycarbonate resin and is a solvent immiscible with water.
[0015]
The organic solvent referred to in the present invention includes at least one good solvent as a main solvent, and a poor solvent and / or a non-solvent may be partially mixed therewith. The good solvent, the poor solvent and the non-solvent here correspond to “Good Solvent” and “Fair Solvent” in the classification in Table 3-1 of WFCHRISTOPHER, DWFOX, 1962, pages 32 to 33. The solvent is a good solvent, the solvent corresponding to “Poor Solvent”, “Very Poor Solvent” and “Weak Solvent” is a poor solvent, and the solvent corresponding to “Nonsolvent” is a non-solvent. Typical examples of good solvents include halogenated hydrocarbons such as methylene chloride and tetrachloroethane, and typical examples of poor solvents include benzene, toluene, acetone, etc., and typical examples of non-solvents. Examples thereof include hexane and heptane. Such poor solvents and / or non-solvents may be used alone or in combination of two or more.
[0016]
In the method for producing a polycarbonate resin particle according to the present invention, first, the weight ratio of the polycarbonate resin to the organic solvent is 90:10 to 35:65, and the ratio of the polycarbonate resin to water is the polycarbonate resin 100. A slurry or wet paste containing 5 parts by weight or more of water and containing polycarbonate resin, an organic solvent and water is prepared. The organic solvent here means a good solvent for the polycarbonate resin as described above. The slurry is a state in which the polycarbonate resin particles have a fluidity suspended in a mixed medium composed of an organic solvent and water, and the wet paste has a smaller amount of mixed medium than the slurry and does not flow. A thing with low fluidity. Hereinafter, in the present specification, this “slurry or wet paste” may be abbreviated as “starting mixture”.
[0017]
The amount of the organic solvent contained in the starting mixture is such that the ratio of the polycarbonate resin and the organic solvent is 90:10 to 35:65, preferably 85:15 to 60:40, in weight ratio. When the content of the organic solvent is less than 10% by weight, the load on the extruder is increased and it becomes difficult to finely pulverize, and it becomes difficult to obtain a fine powder having a desired size. A polycarbonate resin powder having an extremely small amount cannot be obtained. On the other hand, when the content of the organic solvent exceeds 65% by weight, it is difficult to handle the polycarbonate resin as particles, which is not desirable. When preparing the starting mixture, if the content of the organic solvent in the polycarbonate resin particle-containing mixture (preliminary mixture) is not in an appropriate range, it may be adjusted to the appropriate range by adding or removing the organic solvent. When the organic solvent content is low, an amount of an organic solvent or a polycarbonate resin solution to be a predetermined amount may be added to the preliminary mixture. On the other hand, when the amount of the organic solvent in the premix is too large, polycarbonate resin particles or a slurry or wet paste with a low content of the organic solvent may be added to the premix. In addition, the excess organic solvent may be removed by heating a slurry having a high organic solvent content.
[0018]
The content of water in the starting mixture is 5 parts by weight or more with respect to 100 parts by weight of the polycarbonate resin. The water content is preferably in the range of 5 to 2000 parts by weight, particularly preferably in the range of 7 to 1000 parts by weight. When the water content in the starting mixture is less than 5 parts by weight, it becomes difficult to finely pulverize the polycarbonate resin, and as a result, a granular material having a low residual organic solvent amount cannot be obtained. The upper limit of the amount of water differs depending on the pulverizing apparatus and cannot be generally limited. Therefore, it is desirable to determine the content of water in consideration of the operation operability of the extruder and the adhesiveness of the finely pulverized resin fine powder, and usually the range of 5 to 2000 parts by weight with respect to the polycarbonate resin. The range of 7 to 1000 parts by weight is particularly preferable. When the amount of water is insufficient, water or a resin slurry having a large amount of water may be added, or may be added during fine pulverization. Within the above range, when there is a lot of water, the starting mixture is generally in the form of a slurry, while when it is low, it takes the form of a wet paste.
[0019]
The size and particle size distribution of the polycarbonate resin particles in the starting mixture are not particularly limited, and any material that can be supplied to the fine pulverization step may be used. If it is difficult to supply, it may be crushed. For example, a slurry formed from a reaction mixture obtained by a solution method can be used as it is. In general, the size of the resin particles in the starting mixture is suitably about 0.1 to 50 mm.
[0020]
The starting mixture prepared as described above is continuously fed to an extruder and pulverized in the extruder (a pulverization step). This pulverization step is a step in which the polycarbonate resin particles in the slurry or wet paste as the starting mixture are pulverized mainly by shearing so as to become a fine powder having a particle size of 50 μm or less. It is carried out using an extruder equipped with a function to convert. The extruder has a function of pulverizing so that 90% or more, particularly 95% or more of the obtained fine powder has a particle diameter of 50 μm or less, preferably 40 μm or less, particularly preferably 30 μm or less. What has is preferable. The lower limit of the pulverized fine particles is not limited, but is generally about 0.3 μm. Examples of the type of the extruder include an extruder having functions such as a single-screw or multi-screw extruder, a plunger extruder, and an injection molding machine having an inner screw.
[0021]
Among these extruders, it is preferable to use a twin screw type extruder. In addition, the use of the vent type extruder makes it possible to simultaneously prepare and finely grind the starting mixture in the extruder by supplying water from the vent port. When the polycarbonate resin is finely pulverized by an extruder, troubles such as melting and melting of the resin may occur due to an increase in internal pressure due to an increase in the internal temperature of the cylinder depending on the concentration of the polycarbonate resin and operation conditions. In order to avoid such trouble, it is preferable to use a jacketed cylinder and / or screw having a temperature control function. Moreover, you may provide a screw with a compression part in an extruder.
[0022]
Further, a punch plate or a slit may be provided in the whole or a part of the cylinder of the extruder so as to allow drainage, or a mechanism capable of draining may be provided on the ground side. When there is a large excess of water in the starting mixture, most of it is separated on the opposite side of the extrusion direction or by the punch plate or slit. At that time, the opening of the gland and the punch plate and the clearance of the slit are not particularly limited, but may be appropriately selected depending on the resin particle diameter.
[0023]
In the present invention, the fine powder of the polycarbonate resin finely pulverized in the fine pulverization step is further pressurized and extruded in an extruder. The extruded granular material is an aggregate of fine powder (hereinafter, this granular material is referred to as an aggregate, and this process is referred to as an aggregate formation process). In this agglomerate forming step, the pressure is increased so that the fine powder becomes an agglomerate, and the ratio of the polycarbonate resin to the organic solvent is 95: 5 to 35:65, preferably 85:15 to 60: by weight. It is carried out by adjusting the ratio of the polycarbonate resin to water in the range of 40 to 50 to 120 parts by weight, preferably 7 to 70 parts by weight with respect to 100 parts by weight of the polycarbonate resin. The pressure in this agglomerate forming step is such that the fine powder is partially bonded to form an aggregate block, and the size of the fine powder forming this agglomerate is the folded cross section. When a photograph is taken with an electron microscope, an enlarged photograph of about 1000 times can be easily confirmed visually.
[0024]
In the agglomerate forming step, it is preferable to carry out at a temperature at which 90% or more of the polycarbonate resin fine powder can maintain a particle size of 50 μm or less. This temperature varies depending on the pressure and the amount of the organic solvent and cannot be generally determined. However, when the temperature becomes high, 90% or more of the fine powder cannot retain a particle size of 50 μm or less due to swelling, dissolution or softening, and melting. In some cases, they adhere to each other to form a continuous layer, making it impossible to obtain a polycarbonate resin powder having very little residual organic solvent.
[0025]
The pressurizing means in this agglomerate forming step is carried out continuously in the extruder following the pulverization step. In particular, an extruder provided with a seal ring in front of the exit of the extruder is used, and when fine powder pulverized in the extruder passes through the seal ring, it is pressurized to form an aggregate, and the exit of the extruder It is preferable to employ a more extruded method. Also, using an extruder provided with a die having pores or slits at the exit of the extruder, as the fine powder pulverized in the extruder moves to the exit of the extruder, it is gradually pressurized to form aggregates The agglomerates may be extruded from pores or slits.
[0026]
In the agglomerate forming step, the content ratio of the organic solvent does not need to be particularly adjusted, and may be the content of the organic solvent in the fine powder obtained from the fine pulverization step. That is, the content of the organic solvent is such that the ratio of the polycarbonate resin and the organic solvent is 95: 5 to 35:65, preferably 90:10 to 60:40 by weight, and by maintaining such an amount, The resulting agglomerates have moderate shape retention. When the amount is less than 5% by weight, the aggregate becomes brittle, and when the amount exceeds 65% by weight, the intended fine powder cannot be retained.
[0027]
The water content in the agglomerate forming step is in the range of 5 to 120 parts by weight, preferably 7 to 70 parts by weight of water with respect to 100 parts by weight of the polycarbonate resin. The shape is destroyed and aggregates cannot be obtained. When the amount exceeds 120 parts by weight, the aggregates become brittle.
[0028]
When forming polycarbonate resin fine powders and aggregates with an extruder, the internal pressure of the cylinder is particularly high in the areas where the shear is applied and the areas where pressure is applied, but this back pressure may not sufficiently transport the starting mixture. is there. At this time, when the discharge amount is reduced and the extruder having the drainage mechanism is used, there may be a problem that the polycarbonate resin is discharged simultaneously with the water from the punch plate or the slit which is the drainage mechanism. . In order to avoid such trouble, the surface roughness expressed by the ten-point average roughness of the screw surface for transporting the starting mixture is 3 μm or less, preferably 0.01 to 3 μm, more preferably 0.1 to 3 μm, Preferably it is 1-3 micrometers. When the surface roughness exceeds 3 μm, the processing capability of the extruder is not stabilized, which is not preferable. As a material for such a screw, stainless steel or nitrided steel is preferably used. Further, a screw having a surface roughness exceeding 3 μm can be used after being adjusted to the above range by polishing or the like.
[0029]
In the present invention, the aggregate obtained in the aggregate forming step is pulverized or cut and dried. The order in which this is performed may be arbitrary, but it is generally desirable to dry after grinding or cutting. Drying in this step means removing both the organic solvent and water contained in the aggregate.
[0030]
Explaining this process, the aggregate of the polycarbonate resin particles extruded from the extruder is cut by an arbitrary method, and in particular, a polycarbonate having a uniform particle size by grinding with a hammer mill with a screen provided immediately after the extruder. A method for obtaining resin particles is a preferred example. At this time, the particle size of the polycarbonate resin granular material can be adjusted by adjusting the opening of the screen of the hammer mill with a screen. Also, by attaching a die having pores or slits at the exit of the extruder and rotating a propeller on which the extruded strand-like or ribbon-like aggregates are attached so as to be parallel to the die surface It may be cut. The length of the agglomerates can be adjusted by the propeller mounting position, rotation speed, and the like.
[0031]
The obtained polycarbonate resin agglomerates do not need to be drained and can be dried continuously and / or batchwise. Drying may be performed only by the drying step, and if necessary, after performing a deorganic solvent treatment such as a method of mixing with a liquid having a boiling point of the residual organic solvent or more and a method of bringing it into contact with water vapor, and drying. Also good. The amount of the organic solvent finally remaining can be further reduced by the method of contacting with water vapor. When the amount of residual organic solvent in the obtained polycarbonate resin aggregate is large and the aggregate is easy to collapse, it is dried using a device that does not take a share, such as a hot air circulation dryer, steam tube dryer, pow heater, hopper dryer, tower dryer, etc. Alternatively, after drying in advance with these apparatuses, it is preferable to further dry using a drying apparatus such as a paddle dryer or a multi-fin dryer. In particular, when the aggregate is dried at a temperature equal to or higher than the glass transition temperature (Tg), an apparatus that does not take a share is preferable. These dryers may be used alone or in combination. Arbitrary stabilizers, additives, fillers and the like may be added to the polycarbonate resin granules thus obtained as necessary.
[0032]
【Example】
Examples of the present invention will be described below for further description. In the examples,% is% by weight, and the methylene chloride content was determined by analyzing the chlorine content with a total organic halogen analyzer [TOX manufactured by Mitsubishi Kasei Co., Ltd.] and converted to the amount of methylene chloride. Further, the surface roughness was determined by calculating the ten-point average roughness of the groove portion of the screw using a two-dimensional / three-dimensional surface roughness measuring instrument [SURFCORDER manufactured by Kosaka Laboratory Ltd.].
[0033]
[Example 1]
(A) A 20% methylene chloride solution of polycarbonate resin having a specific viscosity of 0.426 obtained from bisphenol A and phosgene by a conventional method was put into a kneader charged with warm water maintained at 42 ° C., and methylene chloride was removed. A slurry having a liquid temperature of 38 ° C. was obtained by pulverization. The ratio of the polycarbonate resin granules and methylene chloride in the slurry was 75:25, and 100 parts of water with respect to 100 parts of the polycarbonate resin granules.
[0034]
(B) A diameter of 65 mm, L / D of 14, and a groove depth of 12.5 mm, each having a pair of an orthogonal kneading disk, a reverse kneading disk and a seal ring attached to one third of the entire length from the tip. A twin-screw extruder having a screw made of nitrided steel having a surface roughness of 2.6 μm and a cylinder provided with a separation water discharge slit and a temperature adjusting jacket was operated with the screw rotation speed set to 156 rpm. The slurry obtained in Example 1 (A) was continuously supplied to an extruder to remove liquid, finely pulverize, and extruded to obtain an aggregate of polycarbonate resin fine powder. This agglomerate had an agglomerate to methylene chloride ratio of 89:11 and 13 parts water to 100 parts agglomerates. Moreover, the maximum discharge amount in extrusion was 400 kg / hour, and the extruder specific power was 0.059 kWh / kg. This agglomerate was dried at 145 ° C. for 6 hours by a hot air circulation dryer to obtain a resin powder having a residual methylene chloride content of 4 ppm.
[0035]
[Comparative Example 1]
1/3 each of a pair of orthogonal kneading disc, reverse kneading disc and seal ring is attached to 1/3 of the total length from the tip, the diameter is 65mm, L / D is 14, groove depth is 12.5mm, surface roughness A twin-screw extruder having a screw made of nitrided steel having a diameter of 3.1 μm and a cylinder provided with a separation water discharge slit and a temperature adjusting jacket was operated with the screw rotation speed set to 156 rpm. The slurry obtained in Example 1 (A) was continuously supplied to an extruder to remove liquid, finely pulverize, and extruded to obtain an aggregate of polycarbonate resin fine powder. In this aggregate, the ratio of aggregate to methylene chloride was 90:10, and 12 parts of water relative to 100 parts of the aggregate. Moreover, the maximum discharge amount in extrusion was 340 kg / hour, and the specific power of the extruder was 0.078 kW hour / kg. At this time, the resin leaked out from the separation water discharge slit, making operation difficult. This agglomerate was dried at 145 ° C. for 6 hours by a hot air circulation dryer to obtain a resin powder having a residual methylene chloride content of 13 ppm.
[0036]
【The invention's effect】
According to the present invention, it is possible to stably produce a highly excellent polycarbonate resin granule that is very easy to handle with a very small residual solvent and uniform particle size by ordinary drying. It is a thing.

Claims (1)

A polycarbonate resin in which the ratio of the polycarbonate resin to the organic solvent is 90:10 to 35:65 by weight, and the ratio of the polycarbonate resin to water is 5 parts by weight or more with respect to 100 parts by weight of the polycarbonate resin. The slurry or wet paste contained therein is continuously supplied to the extruder, and the slurry or wet paste is sheared in the extruder to form a polycarbonate resin fine powder, and then the obtained polycarbonate resin fine powder is added. The ratio of the polycarbonate resin to the organic solvent is 95: 5 to 35:65 by weight, and the ratio of the polycarbonate resin to water is 5 to 120 parts by weight with respect to 100 parts by weight of the polycarbonate resin. In the method of forming an aggregate of polycarbonate resin fine powder, Method for producing a polycarbonate resin powder or granular material to the surface roughness is characterized by using the following extruder screw 3 [mu] m.