JP2004211028A

JP2004211028A - Method for purifying epoxy resin and epoxy resin composition for sealing semiconductor

Info

Publication number: JP2004211028A
Application number: JP2003002524A
Authority: JP
Inventors: Yukio Nakamura; 幸夫中村; Naritsuyo Takuwa; 成剛宅和; Hideyasu Asakage; 秀安朝蔭; Keisuu Han; 慶崇潘; Akira Hiratsuka; 亮平塚
Original assignee: Tohto Kasei Co Ltd
Current assignee: Tohto Kasei Co Ltd
Priority date: 2003-01-08
Filing date: 2003-01-08
Publication date: 2004-07-29
Anticipated expiration: 2023-01-08
Also published as: JP3837667B2

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for purifying an epoxy resin becoming to have a low hydrolyzable chlorine content suitable for electric/electronic industries such as an electric insulating material, etc., to begin with mainly semiconductor sealing. <P>SOLUTION: This method for purifying the epoxy resin, capable of obtaining a high purity epoxy resin having ≤500 wt. ppm extractable chlorine ion amount by a pressure cooker test at 180°C×20 hr is provided by making ≤100 ppm inorganic chlorine ion concentration in a crude epoxy resin solution obtained by dissolving a crude epoxy resin obtained by an epoxidation reaction in an organic solvent, adjusting water content so as to make 22-32% range aqueous solution of an alkali metal hydroxide in the total resin solution, then adding 0.5-5.0 wt.% alkali metal hydroxide based on the resin amount and performing the reaction at 80-95°C. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

【０００１】
【発明の属する利用分野】
本発明は、主として半導体封止用をはじめとした電気絶縁材料等の電気電子産業用に好適な低加水分解性塩素分となるエポキシ樹脂の精製方法及び、該精製エポキシ樹脂を使用した半導体封止用エポキシ樹脂組成物に関する。
【０００２】
【従来の技術】
多価フェノール類とエピハロヒドリンとをアルカリ金属水酸化物の存在下で反応させてグリシジルエーテル化して製造されたエポキシ樹脂は、硬化剤により架橋させた場合、大きな架橋密度を有する硬化樹脂となり、優れた特性を示すものである。特にノボラック型エポキシ樹脂は１分子中に２〜８個のフェノール核を持ったノボラック樹脂が使用されており、分子中に平均２〜８個のグリシジル基を有しており、ビスフェノールＡ型エポキシ樹脂に比べてより大きな架橋密度を与える硬化樹脂となり、優れた耐薬品性、耐湿性、耐熱性を有するものであり、これらの特性により様々な分野で多く使用されている。
【０００３】
エポキシ樹脂には無機ハロゲンイオンや分子中に存在する加水分解性ハロゲン化物が含まれる。それらの不純物ハロゲン化物の内、無機ハロゲンイオンと一部の易加水分解性ハロゲンは従来の技術で容易に低減する事が出来るが、その他の難加水分解性有機ハロゲンを低減させる事は非常に困難であった。特に電気・電子産業分野で使用されるエポキシ樹脂硬化物は高温・多湿下等の過酷な条件に曝されるとハロゲンイオンとして塩素イオンが遊離生成される。この遊離生成する塩素イオンの量は、プレッシャークッカーテストによる抽出塩素イオン濃度と関係するものであり、エポキシ樹脂の加水分解性塩素分に由来するものである。（以後、プレッシャークッカーテストをＰＣＴという。）半導体封止材に使用する高純度エポキシ樹脂は、加水分解性塩素分が４２０ｐｐｍ以下である事と全塩素分が１０００ｐｐｍ以下である事が望まれており、更には、ＰＣＴによる抽出塩素イオン量が５００ｐｐｍ以下となることが強く望まれていた。
【０００４】
この様な背景から、加水分解性塩素を低減するために様々な製造方法が提案されている。例えば、特許第３０４４４１２号公報では多価フェノールとエピクロルヒドリン及び、直鎖状エーテル化合物と固形アルカリ水酸化物を一括投入し系内水分を０．１％〜４．０％の範囲で反応する第１工程とエピクロルヒドリンの存在下副生アルカリ金属ハロゲン化物を水洗または、濾過により除去したのち、エピクロルヒドリンを回収し粗エポキシ樹脂を得る第２工程と第２工程で得られた粗エポキシ樹脂中の加水分解性塩素分に対して１．０〜４．０モル倍量のアルカリ金属水酸化物を２０％水溶液以下で１００℃以下で再反応精製する第３工程を経て高純度エポキシ樹脂を得る方法が開示されている。
【０００５】
しかしながら、第３工程での精製反応において前述の加水分解性塩素分が４２０ｐｐｍ以下に低下せず、逆に上昇してしまう結果をもたらす事があった。これは、第２工程で得られた樹脂の加水分解性塩素分が安定しない事と、第３工程のアルカリ金属水酸化物の水溶液濃度が低いため脱ハロゲン化が進まない為と考えられた。
【０００６】
また、多価フェノールをエピハロヒドリンと直鎖エーテルの存在下においてアルカリ金属水酸化物水溶液で製造した粗エポキシ樹脂をケトン類等の溶媒に溶解した後、副生アルカリ金属ハロゲン化物を水洗により除去し、再反応精製する方法においてもこの加水分解性塩素分が前述の４２０ｐｐｍ以下で安定して得られなかった。また、４２０ｐｐｍ以下となった場合はエポキシ当量の増大と樹脂の高分子化重合が起きてしまう事が避けられなかった。
【０００７】
【発明が解決しようとする課題】
本発明は、加水分解性塩素分が４２０ｐｐｍ以下であるようなエポキシ樹脂を安定して得られるような精製方法について種々検討した。即ち、本発明者らはｏ−クレゾールのボラック樹脂をエピクロルヒドリンと直鎖状エーテル化合物とアルカリ金属水酸化物とで製造された粗エポキシ樹脂の再反応精製条件の追及において選択的に加水分解性塩素分とＰＣＴによる抽出塩素イオン濃度を下げる条件として、アルカリ金属水酸化物の種類と樹脂溶液中のアルカリ金属水溶液濃度に着目し、これらを適切な組合せにより安定的に加水分解性塩素分が４２０ｐｐｍ以下であり、かつＰＣＴによる抽出塩素イオン濃度が５００ｐｐｍ以下であるような精製方法を見出し、本発明を完成したもので、本発明の目的は、加水分解性塩素分が安定的に４２０ｐｐｍ以下であり、ＰＣＴの抽出水中のハロゲンイオン不純物が安定的に５００ｐｐｍ以下となるエポキシ樹脂の精製方法であり、更には、１８０℃×２０時間のＰＣＴによる抽出塩素イオン量が５００重量ｐｐｍ以下である高純度エポキシ樹脂を提供するものである。
【０００８】
【課題を解決するための手段】
本発明の要旨は、エポキシ化反応によって得られたエポキシ樹脂を有機溶剤に溶解せしめた粗エポキシ樹脂溶液中の無機塩素イオン濃度を１００ｐｐｍ以下とし、該樹脂溶液全体中のアルカリ金属水酸化物の水溶液を２２〜３２％の範囲になるように水を添加もしくは脱水により水分量を調整した後、樹脂量に対して０．５〜５．０重量％のアルカリ金属水酸化物を添加し、８０〜９５℃で反応せしめて、１８０℃×２０時間のプレッシャークッカーテストによる抽出塩素イオン量が５００重量ｐｐｍ以下である高純度エポキシ樹脂を得ることを特徴とするエポキシ樹脂の精製方法である。
【０００９】
そして、粗エポキシ樹脂中の加水分解性塩素は６００〜７，０００ｐｐｍ、好ましくは６００〜１，０００ｐｐｍ含有する。
本発明における加水分解性塩素分とは、エポキシ樹脂をジオキサンに溶解し、１Ｎ−水酸化カリウムのエタノール溶液を添加して１２０℃の油浴で３０分間還流反応させ、遊離した塩素量を酢酸酸性下で０．０１Ｎ−硝酸銀溶液で電位差滴定装置により測定し、これを試料重量で除した値である。また、本発明のプレッシャークッカーテストによる抽出塩素イオン濃度とは、エポキシ樹脂と純水をそれぞれ精秤してテフロン製の容器に採り、そのテフロン容器を金属製の外容器の中に入れ密封し１８０℃×２０時間かけて加熱加圧抽出し室温まで放置した後に、抽出水中の塩素イオン濃度（重量ｐｐｍ）をイオンクロマトグラフィーにより測定するものである。
【００１０】
すなわち、本発明は、多価フェノール類から選択された一種の化合物とエピクロルヒドリンをアルカリ金属水酸化物の存在下に反応させてエピクロルヒドリンを回収分離した後の粗エポキシ樹脂をケトン類に溶解せしめ濾過または、水洗してアルカリ金属塩素化物を除去し、更にもう一度水洗をし、樹脂溶液中の無機塩素イオン濃度を１００ｐｐｍ以下とせしめ、樹脂溶液全体中のアルカリ金属水酸化物の水溶液濃度を２２％〜３２％の範囲になるように水分量を調整した後、樹脂量に対して０．５重量％〜５．０重量％のアルカリ金属水酸化物を添加し反応温度を８０℃〜９５℃の範囲で反応することにより、加水分解性塩素分が安定的に４２０ｐｐｍ以下であり、かつ、ＰＣＴによる抽出塩素イオン分が５００ｐｐｍ以下であるエポキシ樹脂を得る事ができるものである。この場合に、アルカリ金属水酸化物は固形の状態および水溶液の状態のいずれも用いることができる。
【００１１】
そして、本発明は次のエポキシ樹脂の精製工程を含むものである。
多価フェノール類から選択された一種の化合物とエピクロルヒドリン及び、直鎖エーテル化合物の存在下、アルカリ金属水酸化物により還流脱水で反応させた後、エピクロルヒドリンおよび直鎖エーテル化合物を回収分離した後の粗エポキシ樹脂をケトン類に溶解せしめ乾式濾過または、水洗でアルカリ金属塩素化物を除去し、更に水洗し水溶性不純物を除去し、樹脂溶液中の無機塩素イオン濃度を１００ｐｐｍ以下として、樹脂溶液中のアルカリ水溶液濃度として２２％〜３２％の範囲に入るように水を添加もしくは脱水により水分量を調整した後、樹脂に対して０．５重量％〜５重量％の固形アルカリ金属水酸化物またはアルカリ金属水酸化物水溶液を投入し常圧下で８０〜９５℃の範囲で所定時間、精製処理をおこなう工程。
上記、精製処理を行った後、水洗し、更に過剰なアルカリ金属水酸化物をリン酸、リン酸一ナトリウム、シュウ酸等で中和処理し、再水洗分液後濾過し、温度が１５０℃〜２００℃で減圧度が１０ｔｏｒｒ以下で溶媒を除去して低加水分解性塩素含有量のエポキシ樹脂を得る工程。
【００１２】
【発明の実施の形態】
本発明における粗エポキシ樹脂は多価フェノール類とエピクロルヒドリンと直鎖状エーテル化合物とアルカリ金属水酸化物でエポキシ化反応して得られる。この多価フェノール類としては、例えばビスフェノールＡ、ビスフェノールＦ等の２官能フェーノール類、フェノールノボラック、ｏ−クレゾールノボラック等のノボラック樹脂類が挙げられるが、特にｏ−クレゾールノボラックが好ましい。
【００１３】
本発明に使用されるエピハロヒドリンとしてはエピクロルヒドリンが好ましい。また、直鎖状エーテル類としては、エチレングリコールジメチルエーテル、ジエチレングリコールジメチルエーテル、エチレングリコールジエチルエーテル、ジエチレングリコールジエチルエーテル、エチレングリコールジプロピルエーテル、ジエチレングリコールジプロピルエーテル、エチレングリコールジブチルエーテル、ジエチレングリコールジブチルエーテル、等が挙げられるが、工業的にエチレングリコールジメチルエーテル及び、ジエチレングリコールジメチルエーテルが特に好ましい。
【００１４】
本発明に使用されるアルカリ金属水酸化物としては、例えば水酸化ナトリウム、水酸化カリウム、水酸化カルシウム等が挙げられるが、特に水酸化ナトリウムと水酸化カリウムが好ましく、これらのアルカリ金属水酸化物は、固形ないし水溶液濃度２２％以上の範囲で使用され、アルカリ金属水酸化物を併用することができ、また、単独で使用しても良い。
【００１５】
粗エポキシ樹脂を得る為に、原料ノボラック樹脂をエピクロルヒドリンと直鎖状エーテルを混合した溶液に溶解するが、この時のエピクロルヒドリンは原料ノボラックのフェノール性水酸基１モルに対して２〜１０倍モル量の範囲で使用される。１０倍量を越えて使用する事は該エピクロルヒドリンの過度の損失と直鎖状エーテルの損失を招く為好ましくない。直鎖状エーテルの量はエピクロルヒドリンに対して５重量部〜４０重量部の範囲で使用される。
【００１６】
この様にして原料ノボラック樹脂を溶解した溶液にアルカリ金属水酸化物を常圧若しくは減圧下で添加してエポキシ化反応を実施する。この時のアルカリ金属水酸化物は原料ノボラックのフェノール性水酸基に対して０．９０〜１．１０モルの範囲で使用される。固形アルカリ金属水酸化物を使用する場合は、常圧で添加し、アルカリ金属水酸化物水溶液で使用する場合は、減圧下添加する。反応は３０℃から７０℃の範囲で行われ、アルカリ金属水酸化物水溶液を滴下中にはエピクロルヒドリンと水とを蒸発凝縮し、分離槽を通して水分は系外へ取り出し、エビクロルヒドリンは反応系内に戻される。反応終了後、該反応液からエピクロルヒドリンと直鎖状エーテルを蒸留により取り出し次の反応に使用される。蒸留後の反応液を樹脂濃度として２０％〜６０％になる量の有機溶剤に溶解し、粗エポキシ樹脂溶液を得る。粗エポキシ樹脂の加水分解性ハロゲンは６００〜７，０００重量ｐｐｍが好ましく、より好ましくは６００から１，０００ｐｐｍである。
【００１７】
精製反応に用いる有機溶剤としては特にメチルイソブチルケトンが好ましい。この粗エポキシ樹脂溶液には、粗エポキシ樹脂とアルカリ金属ハロゲン化物が存在する。このアルカリ金属ハロゲン化物は濾過若しくは水洗により除去する。この時に濾過だけではエピクロルヒドリンの誘導体であるグリセリン等の有機物が残存するため水洗がより好ましい。この様にして得られた粗エポキシ樹脂の溶液（以下、樹脂溶液とする。）を更に樹脂溶液中の塩素イオン濃度が１００ｐｐｍ以下となる様に水洗を実施するが５０ｐｐｍ以下がより好ましい。次にこの樹脂溶液中のアルカリ金属水酸化物水溶液濃度が２２％〜３２％になる様に、水の添加もしくは脱水により調整を行う。脱水条件は常圧下で８５℃〜１０５℃の範囲で行う。脱水が終了後、８０℃〜９０℃に冷却し、固形アルカリ金属水酸化物または、アルカリ金属水酸化物水溶液を粗エポキシ樹脂に対して０．５ｗｔ％〜５ｗｔ％の範囲で添加して常圧下８０℃〜９５℃で再反応精製処理をする。この時の粗エポキシ樹脂に対するアルカリ金属水酸化物の量が０．５ｗｔ％以下では再反応精製処理が十分でなく加水分解性塩素分の低減が少なく、また、５ｗｔ％以上で有れば樹脂の高分子化が起こり、樹脂の粘度の増大とエポキシ当量の増大を招き、目的とする品質が得られなくなる。
【００１８】
アルカリ金属水酸化物の種類として、特に水酸化カリウムが特に好ましく、再反応精製処理時間は、前述の条件で１時間〜３時間の間で行われる。水酸化カリウムは一括または分割で投入することができ、また連続的に分割投入することができる。その後水洗処理により、余剰の水酸化カリウムを除去するが、樹脂溶液のｐＨが６〜４になるようにリン酸、リン酸ナトリウム、シュウ酸、酢酸、炭酸等を添加して中和を行い更に水洗を繰り返した後、濾過してケトン溶媒を減圧蒸留により回収し、目的とした高純度エポキシ樹脂が得られる。
【００１９】
本願発明の高純度エポキシ樹脂は、加水分解性塩素分が４２０ｐｐｍ以下であり、かつ１８０℃×２０時間のＰＣＴの抽出塩素イオン濃度が５００ｐｐｍ以下に低減されたものであり電気及び電子産業用の封止材に好適に使用される。
【００２０】
【実施例】
以下、本発明を実施例をもって詳細に説明するが、これらに限定されるものではない。尚、以下の説明においてのエポキシ当量、加水分解性塩素分及び、ＰＣＴによる抽出塩素イオン濃度はそれぞれ以下の方法で測定した。
【００２１】
エポキシ当量
所定量の試料を所定量のジオキサンに溶解し０．２Ｎ−塩酸のジオキサン溶液を加えて１５分間撹拌反応させた後、クレゾール・レッドを指示薬として０．１Ｎ−水酸化ナトリウムのメタノール溶液で滴定してブランクとの滴定量の差から塩酸と反応したエポキシ当量を求め、これで試料量を除した値をエポキシ当量（ｇ／ｅｑ）とした。
【００２２】
加水分解性塩素分
所定量の試料を所定量のジオキサンに溶解し、１Ｎ−水酸化カリウムのエタノール溶液を添加し１２０℃のオイルバス中で３０分間還流反応させ、生成した塩化カリウムを酢酸酸性下で０．０１Ｎ−硝酸銀溶液で電位差滴定装置により測定し、これを試料量で除した塩素分換算値を加水分解性塩素分（ｐｐｍ）とした。
【００２３】
プレッシャークッカーテストによる抽出塩素イオン濃度
試料約５ｇと純水約５０ｇをそれぞれ精秤してテフロン製の所定の容器に採り、そのテフロン容器を金属製の外容器の中に入れ密封し１８０℃×２０時間かけて加熱抽出し、室温まで下げてから抽出水をイオンクロマトグラフにかけて、抽出水中の塩素イオン濃度（重量ｐｐｍ）を測定し、これを樹脂当たりの塩素イオンとして算出する。
【００２４】
以下本発明を実施例を挙げて詳細に説明する。
実施例１
四つ口セパラブルフラスコに軟化点が９８℃でフェノール性水酸基当量が１２０ｇ／ｅｑのｏ−クレゾールノボラックを１６０重量部、エピクロルヒドリン５５５重量部とジエチレングリコールジメチルエーテル１４０重量部を反応容器に入れ、撹拌溶解させた。均一に溶解後８０ｍｍＨｇの減圧下５４℃に保ち、４８．５％水酸化ナトリウム水溶液１０８重量部を４時間かけて滴下し、この滴下中に還流留出した水とエピクロルヒドリンを分離槽で分離しエピクロルヒドリンは反応容器へ戻し、水は系外に除いて反応した。
【００２５】
反応終了後、反応液からエピクロルヒドリンとジエチレングリコールジメチルエーテルを減圧下で蒸留により留去させて粗エポキシ樹脂と塩化ナトリウムの混合物を得た。次いでこの一部をサンプリングしメチルイソブチルケトンに溶解し、濾過により塩化ナトリウムを除去しメチルイソブチルケトンを蒸留により除去した。得られた粗エポキシ樹脂のエポキシ当量は、１９７ｇ／ｅｑ、加水分解性塩素分は、６１０ｐｐｍであった。
【００２６】
次に、粗エポキシ樹脂混合物３００重量部をメチルイソブチルケトン５３０重量部に溶解し、ついで塩化ナトリウムが２５重量％になる量の温水を加え分液により、塩化ナトリウムと不溶解ポリマーを除去した。分液後の樹脂溶液層に６８重量部の温水を加えて水洗した。水洗分液後の樹脂溶液中の塩素イオン濃度は１７ｐｐｍであった。この樹脂溶液を加熱昇温し還流脱水により、共沸で留出してくる水を系外に除いて９５℃迄昇温した後、８５℃迄冷却し、固形ＫＯＨ（純度９５．５％）を４．０重量部投入して再反応精製処理を２時間実施した。この時のＫＯＨ水溶液としての濃度は、２６．３％であった。再反応精製処理後の樹脂溶液に６８重量部の温水を加えて水洗した。水洗分液後１０％リン酸ソーダ水を３重量部と温水６８重量部を加えて中和し、静置分液した。中和分液水のｐＨが６〜７であることを確認し、更に樹脂溶液を温水６８重量部で水洗し、水洗分液水のｐＨが６〜７であることを確認した。分液後の樹脂溶液を濾過してメチルイソブチルケトンを蒸留により留去してｏ−クレゾールノボラックエポキシ樹脂を得た。得られた樹脂のエポキシ当量は、１９８ｇ／ｅｑで有り、加水分解性塩素分は３６０ｐｐｍで有り、ＰＣＴによる抽出塩素イオン濃度は４３０ｐｐｍであった。
【００２７】
実施例２〜４及び、比較例１〜３
再反応精製処理を表１に示す条件で行った他は、実施例１と同様にしてｏ−クレゾールノボラックエポキシ樹脂を得た。得られた樹脂のエポキシ当量、加水分解性塩素分及び、ＰＣＴによる抽出塩素イオン濃度を表１に併せて記載する。
【００２８】
【表１】

【００２９】
実施例５
軟化点が９８℃でフェノール性水酸基当量が１２０ｇ／ｅｑのｏ−クレゾールノボラックを０重量部、エピクロルヒドリン５５５重量部とジエチレングリコールジメチルエーテル１４０重量部を反応容器に入れ、撹拌溶解させた。均一に溶解後、固形ＫＯＨを３０重量部添加した後、８０ｍｍＨｇの減圧下５４℃に保ち３時間反応させた。次いで４８．５％水酸化ナトリウム水溶液６４重量部を４時間かけて滴下し、この滴下中にエピクロルヒドリンと水の共沸により還流留出した水とエピクロルヒドリンを分離槽で分離しエピクロルヒドリンは反応容器へ戻し、水は系外に除いて反応した。反応終了後、反応液からエピクロルヒドリンとジエチレングリコールジメチルエーテルを減圧下で蒸留により留去させて粗エポキシ樹脂と塩化アルカリ金属の混合物を得た。
【００３０】
この一部をサンプリングし、メチルイソブチルケトンに溶解し、濾過により塩化アルカリ金属を除去しメチルイソブチルケトンを蒸留により除去した。得られた粗エポキシ樹脂のエポキシ当量は、１９７ｇ／ｅｑ、加水分解性塩素分は、８１０ｐｐｍであった。この粗エポキシ樹脂混合物を実施例１と同様の再反応精製処理を行って得られたエポキシ樹脂のエポキシ当量は１９８ｇ／ｅｑ、加水分解性塩素分は４０５ｐｐｍであり、ＰＣＴによる抽出塩素イオン濃度は４１０ｐｐｍであった。
【００３１】
実施例６〜７及び、比較例４〜６
実施例５と同様の主反応条件で得た粗エポキシ樹脂を用いて、再反応精製処理を表２に示す条件で行った他は、実施例１と同様にしてｏ−クレゾールノボラックエポキシ樹脂を得た。得られた樹脂のエポキシ当量、加水分解性塩素分及び、ＰＣＴによる抽出塩素イオン濃度を実施例５とともに表２に併せて記載する。
【００３２】
【表２】

【００３３】
【発明の効果】
上記の表１及び２の結果から明らかなように、本発明のエポキシ樹脂の精製方法により、ＰＣＴ塩素イオン濃度が５００ｐｐｍ、エポキシ当量が２００ｇ／ｅｑ未満であり、加水分解性塩素分が４２０ｐｐｍ以下とすることが可能となった。[0001]
FIELD OF THE INVENTION
The present invention relates to a method for purifying an epoxy resin having a low hydrolyzable chlorine content suitable for use in the electric and electronic industries such as an electric insulating material mainly for semiconductor encapsulation, and a semiconductor encapsulation using the purified epoxy resin. The present invention relates to an epoxy resin composition for use.
[0002]
[Prior art]
Epoxy resins produced by reacting polyhydric phenols with epihalohydrin in the presence of an alkali metal hydroxide and glycidyl etherifying, when crosslinked with a curing agent, become a cured resin having a large crosslink density, and have excellent properties. It shows the characteristics. In particular, a novolak type epoxy resin uses a novolak resin having 2 to 8 phenol nuclei in one molecule, and has an average of 2 to 8 glycidyl groups in the molecule, and is a bisphenol A type epoxy resin. It is a cured resin that gives a higher crosslinking density than that of, and has excellent chemical resistance, moisture resistance, and heat resistance. Due to these properties, it is widely used in various fields.
[0003]
Epoxy resins include inorganic halide ions and hydrolyzable halides present in the molecule. Among these impurity halides, inorganic halogen ions and some easily hydrolyzable halogens can be easily reduced by conventional techniques, but it is very difficult to reduce other hardly hydrolyzable organic halogens. Met. In particular, when a cured epoxy resin used in the electric and electronic industries is exposed to severe conditions such as high temperature and high humidity, chlorine ions are liberated as halogen ions. The amount of the chloride ion liberated is related to the concentration of the extracted chloride ion in the pressure cooker test, and is derived from the hydrolyzable chlorine content of the epoxy resin. (The pressure cooker test is hereinafter referred to as PCT.) It is desired that the high-purity epoxy resin used for the semiconductor encapsulant has a hydrolyzable chlorine content of 420 ppm or less and a total chlorine content of 1000 ppm or less. Further, it has been strongly desired that the amount of chloride ions extracted by PCT be 500 ppm or less.
[0004]
Against this background, various production methods have been proposed to reduce hydrolyzable chlorine. For example, in Japanese Patent No. 3044412, a polyhydric phenol and epichlorohydrin, and a linear ether compound and a solid alkali hydroxide are added all at once, and the water content in the system is reacted in a range of 0.1% to 4.0%. After the step and the by-produced alkali metal halide are removed by washing or filtration in the presence of epichlorohydrin, the epichlorohydrin is recovered to obtain a crude epoxy resin. The second step and the hydrolyzability in the crude epoxy resin obtained in the second step There is disclosed a method of obtaining a high-purity epoxy resin through a third step of re-refining an alkali metal hydroxide in an amount of 1.0 to 4.0 mole times the amount of chlorine with a 20% aqueous solution or less at 100 ° C. or less. ing.
[0005]
However, in the purification reaction in the third step, the above-mentioned hydrolyzable chlorine content may not be reduced to 420 ppm or less, but may be increased. This was considered to be because the hydrolyzable chlorine content of the resin obtained in the second step was not stable and the dehalogenation did not proceed because the concentration of the aqueous alkali metal hydroxide solution in the third step was low.
[0006]
Further, after dissolving a crude epoxy resin produced with an aqueous alkali metal hydroxide solution in the presence of epihalohydrin and linear ether in a polyhydric phenol in a solvent such as a ketone, the by-product alkali metal halide is removed by washing with water, Even in the method of re-reaction purification, the hydrolyzable chlorine content was not stably obtained at the above 420 ppm or less. In addition, when the concentration is 420 ppm or less, it is inevitable that the epoxy equivalent is increased and the polymerization of the resin is caused to occur.
[0007]
[Problems to be solved by the invention]
The present invention has variously studied a purification method for stably obtaining an epoxy resin having a hydrolyzable chlorine content of 420 ppm or less. That is, the present inventors selectively used o-cresol volak resin in purifying re-reaction and purification conditions of a crude epoxy resin produced from epichlorohydrin, a linear ether compound and an alkali metal hydroxide. As a condition for lowering the concentration of chloride ion extracted by PCT and PCT, pay attention to the type of alkali metal hydroxide and the concentration of alkali metal aqueous solution in the resin solution. And a purification method in which the concentration of chloride ions extracted by PCT is 500 ppm or less, and the present invention has been completed.The object of the present invention is to stably provide a hydrolyzable chlorine content of 420 ppm or less, A method for purifying an epoxy resin in which halogen ion impurities in PCT extraction water are stably 500 ppm or less. Are those extracted chlorine ion content in PCT of 180 ° C. × 20 hours to provide a high-purity epoxy resin which is 500 ppm by weight or less.
[0008]
[Means for Solving the Problems]
The gist of the present invention is to make the concentration of inorganic chloride ions in a crude epoxy resin solution obtained by dissolving an epoxy resin obtained by an epoxidation reaction in an organic solvent 100 ppm or less, and an aqueous solution of an alkali metal hydroxide in the entire resin solution. After adding water or adjusting the water content by dehydration so as to be in the range of 22 to 32%, an alkali metal hydroxide of 0.5 to 5.0% by weight based on the resin amount is added, and This is a method for purifying an epoxy resin, which comprises reacting at 95 ° C to obtain a high-purity epoxy resin having an extracted chloride ion amount of 500 ppm by weight or less by a pressure cooker test at 180 ° C for 20 hours.
[0009]
And the hydrolyzable chlorine in the crude epoxy resin is contained at 600 to 7,000 ppm, preferably 600 to 1,000 ppm.
The hydrolyzable chlorine content in the present invention means that an epoxy resin is dissolved in dioxane, an ethanol solution of 1N-potassium hydroxide is added, and a reflux reaction is performed for 30 minutes in an oil bath at 120 ° C. It was measured with a potentiometric titrator using a 0.01N-silver nitrate solution below, and this was divided by the sample weight. Further, the extracted chloride ion concentration by the pressure cooker test of the present invention means that an epoxy resin and pure water are each precisely weighed and taken in a Teflon container, and the Teflon container is put in a metal outer container and sealed. After extracting by heating and pressurizing at 20 ° C. × 20 hours and allowing the mixture to stand at room temperature, the chloride ion concentration (ppm by weight) in the extraction water is measured by ion chromatography.
[0010]
That is, the present invention provides a compound selected from polyhydric phenols and epichlorohydrin reacted in the presence of an alkali metal hydroxide to recover and separate epichlorohydrin. And rinsing with water to remove the alkali metal chlorinated product, and then again with water to reduce the concentration of inorganic chloride ions in the resin solution to 100 ppm or less, and to reduce the concentration of the aqueous alkali metal hydroxide solution in the entire resin solution from 22% to 32%. % After adjusting the water content so as to be in the range of 0.5% by weight to 5.0% by weight based on the amount of the resin, and adjusting the reaction temperature in the range of 80 ° C. to 95 ° C. By reacting, an epoxy having a hydrolyzable chlorine content of 420 ppm or less stably and a chloride ion content extracted by PCT of 500 ppm or less. One in which it is possible to obtain the fat. In this case, the alkali metal hydroxide can be used in either a solid state or an aqueous state.
[0011]
The present invention includes the following epoxy resin refining step.
After reacting with a compound selected from polyhydric phenols and epichlorohydrin and reflux dehydration with an alkali metal hydroxide in the presence of a linear ether compound, the crude product after the epichlorohydrin and the linear ether compound are recovered and separated Dissolve the epoxy resin in ketones, dry filter or wash with water to remove the alkali metal chlorinated product, further wash with water to remove water-soluble impurities, reduce the inorganic chloride ion concentration in the resin solution to 100 ppm or less, and remove the alkali in the resin solution. After adding water or adjusting the water content by dehydration so that the concentration of the aqueous solution falls within the range of 22% to 32%, 0.5 to 5% by weight of the solid alkali metal hydroxide or alkali metal with respect to the resin is used. A step of charging an aqueous hydroxide solution and performing a purification treatment at 80 to 95 ° C. for a predetermined time under normal pressure.
After performing the above purification treatment, washing with water, further neutralizing excess alkali metal hydroxide with phosphoric acid, monosodium phosphate, oxalic acid, etc., re-watering, separating and filtering, the temperature was 150 ° C. A step of removing the solvent at a reduced pressure of 10 torr or less at ~ 200 ° C to obtain an epoxy resin having a low hydrolyzable chlorine content.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
The crude epoxy resin in the present invention is obtained by an epoxidation reaction with a polyhydric phenol, epichlorohydrin, a linear ether compound and an alkali metal hydroxide. Examples of the polyhydric phenols include bifunctional phenols such as bisphenol A and bisphenol F, and novolak resins such as phenol novolak and o-cresol novolak, with o-cresol novolak being particularly preferred.
[0013]
As the epihalohydrin used in the present invention, epichlorohydrin is preferable. Examples of the linear ethers include ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol diethyl ether, ethylene glycol dipropyl ether, diethylene glycol dipropyl ether, ethylene glycol dibutyl ether, diethylene glycol dibutyl ether, and the like. However, industrially, ethylene glycol dimethyl ether and diethylene glycol dimethyl ether are particularly preferred.
[0014]
Examples of the alkali metal hydroxide used in the present invention include, for example, sodium hydroxide, potassium hydroxide, calcium hydroxide, and the like. Particularly, sodium hydroxide and potassium hydroxide are preferable, and these alkali metal hydroxides are preferable. Is used in a solid or aqueous solution concentration range of 22% or more, and may be used in combination with an alkali metal hydroxide, or may be used alone.
[0015]
In order to obtain a crude epoxy resin, the raw material novolak resin is dissolved in a solution in which epichlorohydrin and a linear ether are mixed. At this time, epichlorohydrin is used in an amount of 2 to 10 times the molar amount of 1 mol of the phenolic hydroxyl group of the raw material novolak. Used in range. It is not preferable to use more than 10 times of the amount because it causes excessive loss of the epichlorohydrin and loss of the linear ether. The amount of the linear ether is used in the range of 5 to 40 parts by weight based on epichlorohydrin.
[0016]
The epoxidation reaction is carried out by adding the alkali metal hydroxide to the solution in which the raw material novolak resin is dissolved in the above manner at normal pressure or reduced pressure. At this time, the alkali metal hydroxide is used in an amount of 0.90 to 1.10 mol based on the phenolic hydroxyl group of the raw material novolak. When a solid alkali metal hydroxide is used, it is added at normal pressure, and when it is used as an alkali metal hydroxide aqueous solution, it is added under reduced pressure. The reaction is carried out at a temperature in the range of 30 ° C. to 70 ° C. During the dropwise addition of the aqueous alkali metal hydroxide solution, epichlorohydrin and water are evaporated and condensed, water is taken out of the system through the separation tank, and ebichlorohydrin is added to the reaction system. Will be returned within. After completion of the reaction, epichlorohydrin and linear ether are removed from the reaction solution by distillation and used for the next reaction. The reaction solution after the distillation is dissolved in an organic solvent in an amount of 20% to 60% as a resin concentration to obtain a crude epoxy resin solution. The hydrolyzable halogen of the crude epoxy resin is preferably from 600 to 7,000 ppm by weight, more preferably from 600 to 1,000 ppm.
[0017]
As the organic solvent used in the purification reaction, methyl isobutyl ketone is particularly preferred. The crude epoxy resin solution contains the crude epoxy resin and the alkali metal halide. The alkali metal halide is removed by filtration or washing with water. At this time, if only filtration is performed, organic substances such as glycerin, which is a derivative of epichlorohydrin, remain, so that washing with water is more preferable. The solution of the crude epoxy resin thus obtained (hereinafter referred to as “resin solution”) is further washed with water so that the chloride ion concentration in the resin solution becomes 100 ppm or less, but 50 ppm or less is more preferable. Next, adjustment is performed by adding or dehydrating water so that the concentration of the aqueous alkali metal hydroxide solution in the resin solution becomes 22% to 32%. The dehydration is performed at a temperature of 85 ° C to 105 ° C under normal pressure. After the dehydration is completed, the mixture is cooled to 80 ° C to 90 ° C, and a solid alkali metal hydroxide or an aqueous solution of an alkali metal hydroxide is added to the crude epoxy resin in a range of 0.5 wt% to 5 wt%, and the mixture is subjected to normal pressure. The re-reaction purification treatment is performed at 80 ° C to 95 ° C. At this time, if the amount of the alkali metal hydroxide relative to the crude epoxy resin is 0.5 wt% or less, the re-reaction purification treatment is not sufficient, and the reduction of the hydrolyzable chlorine content is small. Polymerization occurs, resulting in an increase in the viscosity of the resin and an increase in the epoxy equivalent, and the desired quality cannot be obtained.
[0018]
As the kind of the alkali metal hydroxide, potassium hydroxide is particularly preferred, and the re-reaction and purification treatment time is 1 hour to 3 hours under the above-described conditions. Potassium hydroxide can be charged all at once or dividedly, and can be dividedly charged continuously. After that, excess potassium hydroxide is removed by washing with water, but neutralization is performed by adding phosphoric acid, sodium phosphate, oxalic acid, acetic acid, carbonic acid or the like so that the pH of the resin solution becomes 6 to 4. After repeated washing with water, the ketone solvent is recovered by filtration under reduced pressure by filtration, and the desired high-purity epoxy resin is obtained.
[0019]
The high-purity epoxy resin of the present invention has a hydrolyzable chlorine content of 420 ppm or less and a PCT extraction chloride ion concentration of 180 ° C. × 20 hours reduced to 500 ppm or less. It is suitably used as a stop material.
[0020]
【Example】
Hereinafter, the present invention will be described in detail with reference to Examples, but it should not be construed that the invention is limited thereto. In the following description, the epoxy equivalent, the hydrolyzable chlorine content, and the concentration of chloride ion extracted by PCT were measured by the following methods.
[0021]
Epoxy equivalent A predetermined amount of a sample was dissolved in a predetermined amount of dioxane, a 0.2N-hydrochloric acid dioxane solution was added, and the mixture was stirred and reacted for 15 minutes. Then, using cresol red as an indicator, a 0.1N-sodium hydroxide methanol solution was used. The epoxy equivalent reacted with hydrochloric acid was determined from the difference in titer from the blank by titration, and the value obtained by dividing the sample amount by this was defined as the epoxy equivalent (g / eq).
[0022]
A sample of a predetermined amount of hydrolyzable chlorine is dissolved in a predetermined amount of dioxane, an ethanol solution of 1N-potassium hydroxide is added, and a reflux reaction is performed in an oil bath at 120 ° C. for 30 minutes. Was measured with a 0.01N-silver nitrate solution using a potentiometric titrator, and the resulting value was divided by the amount of sample to obtain a chlorine-converted value, which was defined as hydrolyzable chlorine (ppm).
[0023]
About 5 g of the extracted chlorine ion concentration sample and about 50 g of pure water obtained by the pressure cooker test were precisely weighed and placed in a predetermined Teflon container, and the Teflon container was placed in a metal outer container, sealed, and sealed at 180 ° C. × 20. The extract is heated and extracted over a period of time, cooled to room temperature, and the extracted water is subjected to ion chromatography to measure the chloride ion concentration (ppm by weight) in the extract water, which is calculated as chloride ion per resin.
[0024]
Hereinafter, the present invention will be described in detail with reference to examples.
Example 1
160 parts by weight of o-cresol novolac having a softening point of 98 ° C. and a phenolic hydroxyl equivalent of 120 g / eq, 555 parts by weight of epichlorohydrin and 140 parts by weight of diethylene glycol dimethyl ether are put into a four-neck separable flask and stirred and dissolved. Was. After uniformly dissolving, 108 parts by weight of a 48.5% aqueous sodium hydroxide solution was added dropwise over 4 hours while maintaining the pressure at 54 ° C. under a reduced pressure of 80 mmHg. During this addition, water and epichlorohydrin refluxed and distilled were separated in a separation tank, and epichlorohydrin was separated. Was returned to the reaction vessel, and water was removed from the system to react.
[0025]
After completion of the reaction, epichlorohydrin and diethylene glycol dimethyl ether were distilled off from the reaction solution under reduced pressure to obtain a mixture of a crude epoxy resin and sodium chloride. Next, a part of this was sampled and dissolved in methyl isobutyl ketone, and sodium chloride was removed by filtration, and methyl isobutyl ketone was removed by distillation. The resulting crude epoxy resin had an epoxy equivalent of 197 g / eq and a hydrolyzable chlorine content of 610 ppm.
[0026]
Next, 300 parts by weight of the crude epoxy resin mixture was dissolved in 530 parts by weight of methyl isobutyl ketone. Then, sodium chloride and insoluble polymer were removed by adding hot water in an amount of 25% by weight of sodium chloride and separating the mixture. 68 parts by weight of warm water was added to the resin solution layer after the liquid separation, followed by washing with water. The chloride ion concentration in the resin solution after the water separation was 17 ppm. The temperature of the resin solution was increased by heating and reflux dehydration to remove water azeotropically distilled out of the system, and the temperature was raised to 95 ° C., and then cooled to 85 ° C. to remove solid KOH (purity 95.5%). 4.0 parts by weight were added, and the re-reaction purification treatment was performed for 2 hours. At this time, the concentration as a KOH aqueous solution was 26.3%. 68 parts by weight of warm water was added to the resin solution after the re-reaction purification treatment, and the resin solution was washed with water. After washing and separation, 3 parts by weight of 10% sodium phosphate water and 68 parts by weight of warm water were added to neutralize the mixture, and the mixture was allowed to stand and separated. The pH of the neutralized separated water was confirmed to be 6 to 7, and the resin solution was further washed with 68 parts by weight of warm water, and the pH of the washed separated water was confirmed to be 6 to 7. The resin solution after liquid separation was filtered and methyl isobutyl ketone was distilled off by distillation to obtain an o-cresol novolak epoxy resin. The epoxy equivalent of the obtained resin was 198 g / eq, the hydrolyzable chlorine content was 360 ppm, and the chloride ion concentration extracted by PCT was 430 ppm.
[0027]
Examples 2 to 4 and Comparative Examples 1 to 3
An o-cresol novolak epoxy resin was obtained in the same manner as in Example 1, except that the rereaction purification treatment was performed under the conditions shown in Table 1. The epoxy equivalent of the obtained resin, the hydrolyzable chlorine content, and the concentration of chloride ion extracted by PCT are also shown in Table 1.
[0028]
[Table 1]

[0029]
Example 5
0 parts by weight of o-cresol novolac having a softening point of 98 ° C. and a phenolic hydroxyl equivalent of 120 g / eq, 555 parts by weight of epichlorohydrin, and 140 parts by weight of diethylene glycol dimethyl ether were placed in a reaction vessel and stirred and dissolved. After homogeneous dissolution, 30 parts by weight of solid KOH was added, and the mixture was reacted at 54 ° C. under a reduced pressure of 80 mmHg for 3 hours. Next, 64 parts by weight of a 48.5% aqueous sodium hydroxide solution were added dropwise over 4 hours, and during this addition, epichlorohydrin and water distilled off by azeotropic distillation were separated from epichlorohydrin in a separation tank, and epichlorohydrin was returned to the reaction vessel. Water was removed from the system and reacted. After completion of the reaction, epichlorohydrin and diethylene glycol dimethyl ether were distilled off from the reaction solution under reduced pressure to obtain a mixture of a crude epoxy resin and an alkali metal chloride.
[0030]
A part of this was sampled, dissolved in methyl isobutyl ketone, the alkali metal chloride was removed by filtration, and methyl isobutyl ketone was removed by distillation. The epoxy equivalent of the obtained crude epoxy resin was 197 g / eq, and the hydrolyzable chlorine content was 810 ppm. This crude epoxy resin mixture was subjected to the same reaction and purification treatment as in Example 1 to obtain an epoxy resin having an epoxy equivalent of 198 g / eq, a hydrolyzable chlorine content of 405 ppm, and a chloride ion concentration extracted by PCT of 410 ppm. Met.
[0031]
Examples 6 to 7 and Comparative Examples 4 to 6
An o-cresol novolak epoxy resin was obtained in the same manner as in Example 1 except that the crude epoxy resin obtained under the same main reaction conditions as in Example 5 was used and the re-reaction purification treatment was performed under the conditions shown in Table 2. Was. The epoxy equivalent of the obtained resin, the hydrolyzable chlorine content, and the concentration of chloride ion extracted by PCT are shown in Table 2 together with Example 5.
[0032]
[Table 2]

[0033]
【The invention's effect】
As is clear from the results of Tables 1 and 2, the method for purifying the epoxy resin of the present invention has a PCT chloride ion concentration of 500 ppm, an epoxy equivalent of less than 200 g / eq, and a hydrolyzable chlorine content of 420 ppm or less. It became possible to do.

Claims

The concentration of inorganic chloride ions in the crude epoxy resin solution obtained by dissolving the epoxy resin obtained by the epoxidation reaction in an organic solvent is 100 ppm or less, and the concentration of the aqueous alkali metal hydroxide solution in the entire resin solution is 22 to 32. After adjusting the amount of water so as to be in the range of 0.5% by weight, an alkali metal hydroxide of 0.5 to 5.0% by weight based on the amount of the resin was added and reacted at 80 to 95 ° C. under normal pressure. A method for purifying an epoxy resin, comprising obtaining a high-purity epoxy resin having an extracted chlorine ion content of 500 ppm by weight or less by a pressure cooker test at 180 ° C. for 20 hours.

The method for purifying an epoxy resin according to claim 1, wherein the alkali metal hydroxide according to claim 1 is potassium hydroxide.

3. The purification method according to claim 1, wherein the crude epoxy resin according to claim 1 has a hydrolyzable chlorine content of 600 to 7,000 ppm by weight.

4. The method according to claim 1, wherein the organic solvent is methyl isobutyl ketone or toluene.

The said high purity epoxy resin is an o-cresol novolak epoxy resin, epoxy equivalent is less than 200 g / eq, and hydrolyzable chlorine is 420 ppm or less, The Claims any one of Claims 1-4 characterized by the above-mentioned. Purification method.

An epoxy resin composition for semiconductor encapsulation using a high-purity epoxy resin obtained by the purification method according to any one of claims 1 to 5, and a semiconductor device.