JP4137228B2 - Method for producing cyclohexyl methacrylate - Google Patents
Method for producing cyclohexyl methacrylate Download PDFInfo
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- JP4137228B2 JP4137228B2 JP11642398A JP11642398A JP4137228B2 JP 4137228 B2 JP4137228 B2 JP 4137228B2 JP 11642398 A JP11642398 A JP 11642398A JP 11642398 A JP11642398 A JP 11642398A JP 4137228 B2 JP4137228 B2 JP 4137228B2
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- cyclohexyl methacrylate
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P20/00—Technologies relating to chemical industry
- Y02P20/50—Improvements relating to the production of bulk chemicals
- Y02P20/52—Improvements relating to the production of bulk chemicals using catalysts, e.g. selective catalysts
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Description
【０００１】
【発明の属する技術分野】
本発明はメタクリル酸シクロヘキシルの製造方法に関するものである。具体的には、メタクリル酸エステルとシクロヘキサノールからエステル交換反応によりメタクリル酸シクロヘキシルを工業的に製造する方法において、特別な操作を必要とせず合成から蒸留まで一貫してプロセス上実質的な重合を起こさないメタクリル酸シクロヘキシルの工業的な製造方法に関するものである。
【０００２】
【従来の技術】
メタクリル酸エステルは単独または他の重合性モノマーやオリゴマーと混合して、重合開始剤の存在下容易に重合し、機械的特性、耐熱性、耐候性等に優れたポリマーを生成する。なかでもメタクリル酸シクロヘキシルを含むポリマーは、自動車や建築外装塗料などの高耐候性を要求される分野に使用されており、今後の成長が期待されている。
【０００３】
メタクリル酸エステルを製造する場合、触媒として酸やアルカリを用いてメタクリル酸とアルコールを反応させるエステル化反応や、メタクリル酸エステルそのもののエステル部位を他のアルコールで置換するエステル交換反応によりエステルを得る方法が知られている。しかしながら、メタクリル酸エステルはその高い反応性故に重合しやすく、製造工程、貯蔵及び輸送中に熱、光等によりしばしば意図しない重合を起こすことが知られている。
【０００４】
この為、メタクリル酸エステルの製造の各工程及び運搬や貯蔵において、通常重合防止剤が添加されている。使用される重合防止剤としては、例えばハイドロキノン、ハイドロキノンモノメチルエーテル、カテコール等のフェノール性の化合物、ｐ−フェニレンジアミン、フェノチアジン等のアミン化合物等多数の物質が知られている。
【０００５】
しかしながら、これらの重合防止剤はメタクリル酸エステルの蒸留時における重合の防止にはほとんど効果がなく、蒸留の際に釜液の粘度上昇や蒸留塔でポップコーンポリマーが発生してしまうため、蒸留塔が閉塞し蒸留の継続が不可能となってしまう。ここでいうポップコーンポリマーとは、蒸留時にモノマーが３次元的に架橋してできる溶解性、融解性共に低いポリマーの総称である。
【０００６】
メタクリル酸エステルの蒸留精製時の重合防止剤としては、別途、種々のピペリジン化合物が提案されている。特公昭５８−４６４９６ではα，β−不飽和カルボン酸エステルの重合防止剤として２，２，６，６−テトラメチルピペリジン−１−オキシルや、２，２，６，６−テトラメチル−４−アセトキシピペリジン−１−オキシル等のＮ−オキシル化合物が提案されており、特開平６−３４５６８１ではＮ−オキシル化合物とハイドロキノン及びフェノチアジンの組み合わせ、特開平８−４８６５０ではＮ−オキシル化合物とＭｎ塩や銅塩との組み合わせの効果について開示されている。
【０００７】
一般に、メタクリル酸エステルはそのエステル部位が大きくなるほど重合性は低くなるといわれているが、驚くべきことに、一般的に用いられているメタクリル酸メチルとメタクリル酸シクロヘキシルを比較した場合、液体状態での加熱撹拌テストではメタクリル酸メチルの方が重合しやすいが、加熱還流条件や蒸留条件、即ち、気体状態ではメタクリル酸シクロヘキシルの方が圧倒的に重合しやすく、しばしばポップコーンポリマーを発生してしまうことを本発明者らは初めて見出した。つまり、メタクリル酸シクロヘキシルの製造においては、蒸留行程での重合を如何に防止するかが最も重要であるといえる。
【０００８】
一方、エステル交換反応でメタクリル酸エステルを得る場合には、蒸留工程に触媒が残存し、蒸留工程に上記の重合防止剤を用いた場合であっても、残存触媒が重合防止剤の重合防止効果を低下させてしまうことが知られている。残存触媒の影響を除くために、一般には重合防止剤の添加量を増加させる方法がとられているが、この方法では製品の着色等の問題が生じる。また、アルカリ触媒を使用した場合には、触媒を完全に除去するために酸で中和する方法もあるが、中和操作によってメタクリル酸エステルの重合を招く恐れもあるため現実的ではない。
【０００９】
よって、エステル交換反応によるメタクリル酸エステル、特に、メタクリル酸シクロヘキシルを工業的に製造する場合、蒸留工程における残存触媒の影響を最小限に抑え、メタクリル酸シクロヘキシルの重合を防止することのできる簡便な方法が求められている。しかし、上記の先行文献には、対象となるα，β−不飽和カルボン酸エステルとしてメタクリル酸シクロヘキシルが挙げられてはいるものの、触媒が存在しない条件、即ち、メタクリル酸エステル単体に対する効果あるいは接触気相反応で得られた成分に対する効果が示されているのみであり、触媒の存在する系における問題点の解決方法に関する記載は全くない。
【００１０】
【発明が解決しようとする課題】
本発明は、エステル交換反応によってメタクリル酸シクロヘキシルを工業的に製造する方法において、前述した特別な操作を必要とせず、合成から蒸留まで一貫してプロセス上実質的な重合を起こさないメタクリル酸シクロヘキシルの工業的な製造方法を提供することを目的とするものである。
【００１１】
【課題を解決するための手段】
本発明者らは、エステル交換反応によるメタクリル酸シクロヘキシルの工業的な製造方法について検討したところ、ある特定の重合防止剤を蒸留工程で用いた場合、上述した特別な触媒除去操作を行うことなく、蒸留工程でのメタクリル酸シクロヘキシルの重合を防止できることを見出した。
【００１２】
即ち、本発明は、触媒であるアルカリ金属化合物の存在下、メタクリル酸エステルとシクロヘキサノールのエステル交換反応によってメタクリル酸シクロヘキシルを製造する方法において、該エステル交換反応によって得られる粗メタクリル酸シクロヘキシルを下記一般式（１）のピペリジン化合物
【００１３】
【化２】
（Ａは−ＣＨ２−，−ＣＯ−，−ＣＨ（ＯＨ）−基を表す）の存在下、該触媒がアルカリ金属として５〜１５００ｐｐｍ残存する条件下で蒸留・精製してメタクリル酸シクロヘキシルを得ることを特徴とするメタクリル酸シクロヘキシルの製造方法に関する。
本発明で重合防止剤として用いられるピペリジン化合物は、上記一般式（１）で表されるものであればよい。具体的には２，２，６，６−テトラメチル−１−ピペリジノオキシル、４−オキソ−２，２，６，６−テトラメチル−１−ピペリジノオキシル、４−ヒドロキシ−２，２，６，６−テトラメチル−１−ピペリジノオキシル及びそれらの混合物であり、中でもＡが−ＣＯ−，−ＣＨ（ＯＨ）−基であるものが好ましい。一般式（１）で表される重合防止剤以外の重合防止剤を用いた場合は、以下に示す残存触媒量を満たす場合であっても、蒸留時のメタクリル酸シクロヘキシルの重合を抑えることができない。
【００１５】
ピペリジン化合物の使用量は効果を得られる範囲であればいくらでもよいが、使用量が多すぎると製品の着色等の問題が生じる可能性もあるので、１０〜１０００ｐｐｍが好ましい。
エステル交換反応に用いる触媒はアルカリ金属化合物で活性を有する物であれば何でもよいが、例えばアルカリ金属の酸化物、水酸化物、炭酸塩、燐酸塩及びアルコキシド等があげられる。具体的には酸化リチウム、酸化ナトリウム、酸化カリウム、水酸化リチウム、水酸化ナトリウム、水酸化カリウム、炭酸リチウム、炭酸水素リチウム、炭酸ナトリウム、炭酸水素ナトリウム、炭酸カリウム、炭酸水素カリウム、燐酸リチウム、燐酸ナトリウム、燐酸カリウム、リチウムメトキシド、ナトリウムメトキシド、カリウムメトキシド、リチウムブトキシド、ナトリウムブトキシド、カリウムブトキシド等があげられる。これらは単独で用いても、複数を組み合わせて用いてもよい。なかでも取り扱いの容易性や工業的な入手性からアルカリ金属の水酸化物及び炭酸塩が好適に用いられる。なかでもその反応性の高さから水酸化リチウムが最も好ましい。
【００１６】
触媒の使用量としては、エステル交換反応が十分な速度で進行する量であればいくらでもよいが、好ましくは０．０１％から２％である。使用量が多すぎると原料及び生成物であるメタクリル酸エステルの２重結合への付加等の副反応が促進されるため好ましくない。
本発明の特徴は、蒸留工程で重合防止剤として一般式（１）で表されるピペリジン化合物を用い、且つ、残存する触媒量を５〜１５００ｐｐｍにすることにある。蒸留時に残存している触媒量が多すぎると、重合防止剤の重合防止効果に多大な影響を与え、場合によってはその重合防止効果を無くしてしまう。また、残存触媒量は少なければ少ないほどよいが、触媒を完全に除去することはプロセス上に困難であるため、残存する触媒量としては上述の範囲が求められる。一般式（１）で表されるピペリジン化合物を用いることによって、従来の特別な触媒除去操作で完全な触媒除去を行わなくても、上記の残存触媒量を満たすことによって蒸留工程におけるメタクリル酸シクロヘキシルの重合を充分に抑えることができる。
【００１７】
メタクリル酸エステルとシクロヘキサノールのエステル交換反応で得られる粗メタクリル酸シクロヘキシル中に含まれる触媒量が上記の範囲内である場合は、そのまま蒸留工程に供給することができるが、上記範囲を超える場合は、フィルター等による簡易的な濾過操作で触媒の残存量を上記範囲に調整すればよい。
また、残存している触媒の形態については、反応液に懸濁した状態でも溶解した状態でもよいしまたその混合物であってもよい。
【００１８】
エステル交換反応の実施形態は反応蒸留方式が望ましい。反応中に発生する低級アルコールを、原料であるメタクリル酸エステルとの共沸混合物を形成させ反応蒸留で除く方法をとることにより、平衡反応である本反応を効率的に進行させることができる。低級アルコールを反応系から除かない場合、平衡転化率に達した段階で本反応は見かけ上停止してしまい、二重結合へのアルコールの付加等の副反応だけが進行してしまう。反応蒸留方式を達成するためには、共沸混合物が蒸留塔から抜けていくように反応を設計する必要があり、反応温度や系内圧力及びシクロヘキサノールとメタクリル酸エステルの比はこの観点から決定される。具体的には、反応温度は４０〜１００℃程度で系内圧力は１００ｍｍＨｇ〜７６０ｍｍＨｇの範囲が好ましい。反応温度が低いと反応の進行が遅く、逆にあまり上げすぎると重合の恐れが高くなる。また、系内圧力を常圧以上にするのは実際的ではないし、下げすぎると各成分の沸点が近づくため共沸混合物のみを系外に抜き出すことが困難となる。
【００１９】
用いられるメタクリル酸エステルとしては、メタクリル酸メチル、メタクリル酸エチル、メタクリル酸ブチル及びそれらの混合物があげられる。なかでも入手の容易性の観点からメタクリル酸メチルが望ましい。
メタクリル酸エステルとシクロヘキサノールのモル比は１：１〜１：５の範囲が好ましく、１：２〜１：４の範囲がさらに好ましい。
【００２０】
反応中には重合防止剤を添加するのが好ましい。反応の際の重合防止剤としては一般に使われている重合防止剤でよく、ハイドロキノン、ハイドロキノンモノメチルエーテル、カテコール等のフェノール性の化合物、ｐ−フェニレンジアミン、フェノチアジン等のアミン化合物等があげられる。なかでも原料のメタクリル酸メチル中に安定剤として含まれているハイドロキノンモノメチルエーテルが好ましい。もちろん本発明のピペリジン化合物を用いてもよく、この場合、反応生成物の粗メタクリル酸シクロヘキシルを蒸留する際、重合防止剤の添加を省略できる場合がある。
【００２１】
エステル交換反応で得られたメタクリル酸シクロヘキシルを含む反応混合物の精製方法としては、蒸留による分離が好ましく、なかでも減圧蒸留が好ましい。重合を防ぐために、蒸留温度は１００℃以下が好ましいため、これを達成できる減圧条件にする。具体的には１０ｍｍＨｇ以下にするのが好ましい。また、反応混合物中に残存しているメタクリル酸メチル及び低沸成分を予備的な蒸留で除くとよい。すなわち、比較的緩やかな条件でメタクリル酸メチル及び低沸成分を除いた後、メタクリル酸シクロヘキシルが留出する条件にして蒸留を継続する方法を用いるとよい。もちろん、蒸留条件を何段階にも分けて蒸留する方法や、連続的に蒸留条件を変えながら蒸留する方法を用いることもできる。
【００２２】
蒸留時の重合防止剤の添加方法は反応混合物と一緒に釜中に添加する方法が簡便であるが、蒸留中に蒸留塔の途中から重合防止剤を連続あるいは間欠的に添加する方法も一般的に用いられており、この方法で行うこともできる。この際、他の重合防止剤と併用してもよい。
【００２３】
【発明の実施の形態】
以下、本発明の方法を合成例及び実施例でさらに具体的に説明する。なお、ここで用いるメタクリル酸シクロヘキシルを含む反応混合物は、以下の合成例１、２、３及び４で得た物を使用した。
重合の確認方法は釜内部や蒸留塔内部の目視及び釜液の粘度上昇で確認した。
【００２４】
【合成例１】
温度計、蒸留塔、及び撹拌器を備えた３００ｍｌの３口フラスコにシクロヘキサノール５０ｇとメタクリル酸メチル１５０ｇ、触媒として水酸化リチウム０．２ｇ（仕込みＬｉ量として２９０ｐｐｍに相当）、重合防止剤としてハイドロキノンモノメチルエーテル０．１ｇを仕込み、系内の圧力を３４０ｍｍＨｇとし撹拌しながらオイルバスで加熱した。オイルバス温度を９５℃一定でコントロールしたところ釜液の温度は初期に８０℃、反応終了時には８５℃となった。反応に伴い副生したメタノールは、メタノール−メタクリル酸メチル共沸物として蒸留塔トップより間欠的に留出させた。この間、重合の発生は認められなかった。反応は６時間で終了し、メタクリル酸シクロヘキシル約４２％を含む反応混合物１７４ｇを得た。
【００２５】
【合成例２】
触媒として水酸化リチウム２ｇ（仕込みＬｉ量として２９００ｐｐｍに相当）を用い、メタノール−メタクリル酸メチル共沸物の留出を連続的に行った他は、合成例１と同様の方法で反応を行った。この間、重合の発生は認められなかった。反応は１時間で終了し、メタクリル酸シクロヘキシル約４０％を含む反応混合物１７５ｇを得た。
【００２６】
【合成例３】
触媒として水酸化リチウム１ｇ（仕込みＬｉ量として１４５０ｐｐｍに相当）を用い、メタノール−メタクリル酸メチル共沸物の留出を連続的に行った他は、合成例１と同様の方法で反応を行った。この間、重合の発生は認められなかった。反応は２時間で終了し、メタクリル酸シクロヘキシル約４１％を含む反応混合物１７４ｇを得た。
【００２７】
【合成例４】
重合防止剤としてハイドロキノンモノメチルエーテル０．１ｇの他に４−オキソ−２，２，６，６−テトラメチル−１−ピペリジノオキシル０．１ｇを仕込んだ以外は合成例１と同様の方法で反応を行った。この間、重合の発生は認められなかった。反応は６時間で終了し、メタクリル酸シクロヘキシル約４２％を含む反応混合物１７４ｇを得た。
【００２８】
【実施例１】
合成例１で得た反応混合物１７４ｇを５Ｃのフィルターで濾過してメタクリル酸シクロヘキシル約４３重量％を含む反応濾過物１７１ｇを得た。この反応濾過物をＩＣＰ発光分析装置（理学製、ＪＹ−１３８、以降ＩＣＰと省略）で分析した結果、Ｌｉは３２ｐｐｍ含まれていた。このうち１４０ｇを温度計、蒸留塔、及び撹拌器を備えた３００ｍｌの３口フラスコに入れ、重合防止剤として４−オキソ−２，２，６，６−テトラメチル−１−ピペリジノオキシル０．０３ｇを仕込み、圧力を４０ｍｍＨｇとしてメタクリル酸メチルを１時間で留出せしめ、さらに圧力を１０ｍｍＨｇ、分留塔塔頂温度８３〜８８℃でメタクリル酸シクロヘキシルを８時間で留出させた。この間重合の発生は認められなかった。得られたメタクリル酸シクロヘキシルは５５ｇで、純度は９９．７％であった。
【００２９】
【実施例２】
合成例１の反応混合物を濾過せずにそのまま仕込んだ他は実施例１と同様の方法で蒸留した。仕込みのＬｉが全量残っているためＬｉの残存量は２９０ｐｐｍに相当する。蒸留中重合物の発生は認められず、得られたメタクリル酸シクロヘキシルは５３ｇで、純度は９９．６％であった。
【００３０】
【実施例３】
合成例２で得た反応混合物１７５ｇを５Ｃのフィルターで濾過してメタクリル酸シクロヘキシル約４３重量％を含む反応濾過物１７０ｇを得た。この反応濾過物をＩＣＰで分析した結果、Ｌｉは１８２ｐｐｍ含まれていた。このうち１４０ｇを実施例１と同様の方法で蒸留した。蒸留中重合物の発生は認められず、得られたメタクリル酸シクロヘキシルは５２ｇで、純度は９９．５％であった。
【００３１】
【実施例４】
合成例３の反応混合物を濾過せずにそのまま仕込み、実施例１と同様の方法で蒸留した。仕込みのＬｉが全量残っているためＬｉの残存量は１４５０ｐｐｍに相当する。蒸留中重合物の発生は認められず、得られたメタクリル酸シクロヘキシルは５０ｇで、純度は９９．５％であった。
【００３２】
【実施例５】
合成例４の反応混合物を濾過せずにそのまま仕込み、蒸留時に重合防止剤を追加しなかった他は実施例１と同様の方法で蒸留した。仕込みのＬｉが全量残っているためＬｉの残存量は２９０ｐｐｍに相当する。蒸留中重合物の発生は認められず、得られたメタクリル酸シクロヘキシルは５４ｇで、純度は９９．６％であった。
【００３３】
【実施例６】
重合防止剤である４−オキソ−２，２，６，６−テトラメチル−１−ピペリジノオキシルを釜中に０．０１５ｇ仕込み、さらに蒸留塔中段より０．０１５ｇをメタクリル酸シクロヘキシル９ｇに溶解した物を１時間に一回１ｇづつ９回に分けて導入した他は、実施例１と同様の方法で蒸留した。Ｌｉの残存量は３２ｐｐｍである。蒸留中重合物の発生は認められず、得られたメタクリル酸シクロヘキシルは６２ｇ（導入したメタクリル酸シクロヘキシルを含む）で、純度は９９．６％であった。
【００３４】
【比較例１】
合成例２の反応混合物を濾過せずにそのまま仕込んだ他は実施例１と同様の方法で蒸留をスタートしたが、メタクリル酸シクロヘキシルを留出開始後約３時間で蒸留塔内でメタクリル酸シクロヘキシルがポップコーン重合し蒸留塔を閉塞させたため、蒸留を継続することができなくなった。仕込みのＬｉが全量残っているためＬｉの残存量は２９００ｐｐｍに相当する。
【００３５】
【比較例２】
重合防止剤をハイドロキノンモノメチルエーテルとした他は実施例１と同様の方法で蒸留をスタートしたが、メタクリル酸メチルを留出させている段階でフラスコの粘度が上がり、蒸留を継続することができなくなった。Ｌｉの残存量は３２ｐｐｍである。
【００３６】
【比較例３】
重合防止剤をフェノチアジンとした他は実施例１と同様の方法で蒸留をスタートしたが、メタクリル酸シクロヘキシルを留出開始後約４時間で蒸留塔内でメタクリル酸シクロヘキシルがポップコーン重合し蒸留塔を閉塞させたため、蒸留を継続することができなくなった。Ｌｉの残存量は３２ｐｐｍである。
【００３７】
【発明の効果】
本発明の方法により、エステル交換反応によるメタクリル酸シクロヘキシルの工業的な製造において、特別な操作を必要とせず合成から蒸留まで一貫してプロセス上実質的な重合を起こさないメタクリル酸シクロヘキシルの工業的な製造方法を提供することができる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing cyclohexyl methacrylate. Specifically, in a process for industrially producing cyclohexyl methacrylate by transesterification from methacrylic acid ester and cyclohexanol, a substantial polymerization was caused consistently from synthesis to distillation without requiring any special operation. The present invention relates to an industrial process for producing cyclohexyl methacrylate.
[0002]
[Prior art]
The methacrylic acid ester alone or mixed with other polymerizable monomers and oligomers is easily polymerized in the presence of a polymerization initiator to produce a polymer having excellent mechanical properties, heat resistance, weather resistance and the like. Among them, a polymer containing cyclohexyl methacrylate is used in fields requiring high weather resistance such as automobiles and building exterior paints, and is expected to grow in the future.
[0003]
When producing a methacrylic acid ester, a method of obtaining an ester by an esterification reaction in which methacrylic acid and an alcohol are reacted using an acid or an alkali as a catalyst, or an ester exchange reaction in which the ester site of the methacrylic acid ester itself is substituted with another alcohol It has been known. However, it is known that methacrylic acid esters are easily polymerized due to their high reactivity and often cause unintended polymerization due to heat, light, etc. during the manufacturing process, storage and transportation.
[0004]
For this reason, a polymerization inhibitor is usually added in each step of production of the methacrylic acid ester, transportation and storage. As the polymerization inhibitor to be used, a large number of substances such as phenolic compounds such as hydroquinone, hydroquinone monomethyl ether and catechol, and amine compounds such as p-phenylenediamine and phenothiazine are known.
[0005]
However, these polymerization inhibitors are hardly effective in preventing polymerization during distillation of the methacrylic acid ester, and during the distillation, the viscosity of the kettle is increased and popcorn polymer is generated in the distillation tower. It clogs and it is impossible to continue distillation. The term “popcorn polymer” as used herein is a general term for polymers having low solubility and low melting property formed by three-dimensional crosslinking of monomers during distillation.
[0006]
Various piperidine compounds have been proposed as polymerization inhibitors for distillation purification of methacrylic acid esters. Japanese Patent Publication No. 58-46496 discloses 2,2,6,6-tetramethylpiperidine-1-oxyl and 2,2,6,6-tetramethyl-4-oxyl as polymerization inhibitors for α, β-unsaturated carboxylic acid esters. N-oxyl compounds such as acetoxypiperidine-1-oxyl have been proposed. JP-A-6-345681 discloses a combination of an N-oxyl compound, hydroquinone and phenothiazine, and JP-A-8-48650 discloses an N-oxyl compound and an Mn salt or copper. The effect of combination with salt is disclosed.
[0007]
In general, methacrylic acid esters are said to be less polymerizable as the ester moiety becomes larger, but surprisingly, when comparing commonly used methyl methacrylate and cyclohexyl methacrylate, it is in a liquid state. In the heating and stirring test, methyl methacrylate is easier to polymerize, but under heating and reflux conditions or distillation conditions, that is, in the gaseous state, cyclohexyl methacrylate is overwhelmingly more likely to polymerize, often generating popcorn polymers. The present inventors have found for the first time. That is, in the production of cyclohexyl methacrylate, it can be said that the most important thing is how to prevent polymerization in the distillation process.
[0008]
On the other hand, when a methacrylic ester is obtained by a transesterification reaction, the catalyst remains in the distillation step, and even when the above polymerization inhibitor is used in the distillation step, the residual catalyst is a polymerization inhibitory effect of the polymerization inhibitor. It is known that it lowers. In order to eliminate the influence of the residual catalyst, a method of increasing the amount of the polymerization inhibitor is generally taken, but this method causes problems such as product coloring. Further, when an alkali catalyst is used, there is a method of neutralizing with an acid in order to completely remove the catalyst, but this is not practical because there is a possibility that polymerization of the methacrylic acid ester is caused by the neutralization operation.
[0009]
Therefore, when industrially producing methacrylic acid esters by transesterification, especially cyclohexyl methacrylate, it is possible to minimize the influence of residual catalyst in the distillation step and to prevent polymerization of cyclohexyl methacrylate. Is required. However, although the above-mentioned prior literature mentions cyclohexyl methacrylate as the target α, β-unsaturated carboxylic acid ester, it is effective under conditions where no catalyst exists, that is, the effect on the methacrylic acid ester alone or contact gas. The effect on the components obtained by the phase reaction is only shown, and there is no description on how to solve the problem in the system where the catalyst exists.
[0010]
[Problems to be solved by the invention]
The present invention is a method for industrially producing cyclohexyl methacrylate by transesterification, which does not require the special operation described above, and does not cause substantial polymerization in the process from synthesis to distillation. The object is to provide an industrial production method.
[0011]
[Means for Solving the Problems]
When the present inventors examined the industrial manufacturing method of cyclohexyl methacrylate by transesterification, when using a specific polymerization inhibitor in a distillation process, without performing the special catalyst removal operation mentioned above, It has been found that the polymerization of cyclohexyl methacrylate in the distillation process can be prevented.
[0012]
That is, the present invention relates to a method for producing cyclohexyl methacrylate by transesterification of a methacrylic ester and cyclohexanol in the presence of an alkali metal compound as a catalyst. Piperidine compounds of formula (1)
[Chemical 2]
In the presence of (A represents —CH 2 —, —CO—, —CH (OH) — group), cyclohexyl methacrylate is obtained by distillation and purification under the condition that the catalyst remains 5 to 1500 ppm as an alkali metal. The present invention relates to a method for producing cyclohexyl methacrylate.
The piperidine compound used as a polymerization inhibitor in the present invention may be any compound represented by the above general formula (1). Specifically, 2,2,6,6-tetramethyl-1-piperidinooxyl, 4-oxo-2,2,6,6-tetramethyl-1-piperidinooxyl, 4-hydroxy-2, 2,6,6-Tetramethyl-1-piperidinooxyl and mixtures thereof, among which A is preferably a —CO—, —CH (OH) — group. When a polymerization inhibitor other than the polymerization inhibitor represented by the general formula (1) is used, the polymerization of cyclohexyl methacrylate during distillation cannot be suppressed even if the residual catalyst amount shown below is satisfied. .
[0015]
The amount of the piperidine compound used is not particularly limited as long as the effect can be obtained. However, if the amount used is too large, problems such as coloring of the product may occur, so 10 to 1000 ppm is preferable.
The catalyst used in the transesterification reaction may be anything as long as it is an alkali metal compound and has activity, and examples thereof include alkali metal oxides, hydroxides, carbonates, phosphates, and alkoxides. Specifically, lithium oxide, sodium oxide, potassium oxide, lithium hydroxide, sodium hydroxide, potassium hydroxide, lithium carbonate, lithium hydrogen carbonate, sodium carbonate, sodium hydrogen carbonate, potassium carbonate, potassium hydrogen carbonate, lithium phosphate, phosphoric acid Examples thereof include sodium, potassium phosphate, lithium methoxide, sodium methoxide, potassium methoxide, lithium butoxide, sodium butoxide, potassium butoxide and the like. These may be used alone or in combination. Of these, alkali metal hydroxides and carbonates are preferably used because of easy handling and industrial availability. Of these, lithium hydroxide is most preferred because of its high reactivity.
[0016]
The amount of the catalyst used may be any amount as long as the transesterification proceeds at a sufficient rate, but is preferably 0.01% to 2%. If the amount used is too large, side reactions such as addition of the raw material and the product methacrylic acid ester to the double bond are promoted, such being undesirable.
The feature of the present invention is that a piperidine compound represented by the general formula (1) is used as a polymerization inhibitor in the distillation step, and the remaining catalyst amount is 5 to 1500 ppm. If the amount of the catalyst remaining at the time of distillation is too large, the polymerization preventing effect of the polymerization inhibitor is greatly affected, and in some cases, the polymerization preventing effect is lost. Further, the smaller the amount of remaining catalyst is, the better. However, since it is difficult in the process to completely remove the catalyst, the above-mentioned range is required as the amount of remaining catalyst. By using the piperidine compound represented by the general formula (1), the cyclohexyl methacrylate in the distillation step can be obtained by satisfying the above residual catalyst amount without performing complete catalyst removal by a conventional special catalyst removal operation. Polymerization can be sufficiently suppressed.
[0017]
If the amount of catalyst contained in the crude cyclohexyl methacrylate obtained by transesterification of methacrylic acid ester and cyclohexanol is within the above range, it can be supplied to the distillation step as it is, but if it exceeds the above range, The remaining amount of the catalyst may be adjusted to the above range by a simple filtration operation using a filter or the like.
The remaining catalyst may be suspended in the reaction solution, dissolved, or a mixture thereof.
[0018]
The embodiment of the transesterification reaction is preferably a reactive distillation system. By adopting a method in which the lower alcohol generated during the reaction is removed by reactive distillation by forming an azeotrope with the methacrylic acid ester as a raw material, this reaction, which is an equilibrium reaction, can proceed efficiently. If the lower alcohol is not removed from the reaction system, the reaction apparently stops when the equilibrium conversion rate is reached, and only side reactions such as addition of alcohol to the double bond proceed. In order to achieve the reactive distillation system, it is necessary to design the reaction so that the azeotrope escapes from the distillation column, and the reaction temperature, system pressure, and the ratio of cyclohexanol to methacrylate are determined from this viewpoint. Is done. Specifically, the reaction temperature is preferably about 40 to 100 ° C., and the internal pressure is preferably in the range of 100 mmHg to 760 mmHg. If the reaction temperature is low, the progress of the reaction is slow. Conversely, if the reaction temperature is too high, the risk of polymerization increases. In addition, it is not practical to set the internal pressure to be equal to or higher than normal pressure. If the internal pressure is too low, the boiling point of each component approaches, making it difficult to extract only the azeotropic mixture out of the system.
[0019]
Examples of the methacrylic acid ester used include methyl methacrylate, ethyl methacrylate, butyl methacrylate, and mixtures thereof. Of these, methyl methacrylate is desirable from the viewpoint of availability.
The molar ratio of methacrylic acid ester to cyclohexanol is preferably in the range of 1: 1 to 1: 5, more preferably in the range of 1: 2 to 1: 4.
[0020]
It is preferable to add a polymerization inhibitor during the reaction. The polymerization inhibitor used in the reaction may be a commonly used polymerization inhibitor, and examples thereof include phenolic compounds such as hydroquinone, hydroquinone monomethyl ether, and catechol, and amine compounds such as p-phenylenediamine and phenothiazine. Of these, hydroquinone monomethyl ether contained as a stabilizer in methyl methacrylate as a raw material is preferable. Of course, the piperidine compound of the present invention may be used. In this case, when the reaction product crude cyclohexyl methacrylate is distilled, the addition of a polymerization inhibitor may be omitted in some cases.
[0021]
As a purification method of the reaction mixture containing cyclohexyl methacrylate obtained by the transesterification reaction, separation by distillation is preferable, and vacuum distillation is particularly preferable. In order to prevent polymerization, the distillation temperature is preferably 100 ° C. or lower, so that the pressure is reduced to achieve this. Specifically, it is preferably 10 mmHg or less. Also, methyl methacrylate and low boiling components remaining in the reaction mixture may be removed by preliminary distillation. That is, it is preferable to use a method in which distillation is continued under conditions where methacrylic acid cyclohexyl is distilled after removing methyl methacrylate and low-boiling components under relatively mild conditions. Of course, it is also possible to use a method in which distillation conditions are divided into several stages or a method in which distillation is performed while continuously changing the distillation conditions.
[0022]
The method of adding a polymerization inhibitor during distillation is simple to add to the kettle together with the reaction mixture, but a method of adding a polymerization inhibitor continuously or intermittently from the middle of the distillation column during distillation is also common. This method can also be used. At this time, you may use together with another polymerization inhibitor.
[0023]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the method of the present invention will be described in more detail with reference to synthesis examples and examples. In addition, the thing obtained in the following synthesis examples 1, 2, 3, and 4 was used for the reaction mixture containing cyclohexyl methacrylate used here.
The confirmation method of superposition | polymerization was confirmed by the visual observation inside the kettle and the inside of a distillation tower, and the viscosity rise of the kettle liquid.
[0024]
[Synthesis Example 1]
In a 300 ml three-necked flask equipped with a thermometer, distillation column, and stirrer, 50 g of cyclohexanol and 150 g of methyl methacrylate, 0.2 g of lithium hydroxide as a catalyst (corresponding to 290 ppm as the amount of charged Li), hydroquinone as a polymerization inhibitor 0.1 g of monomethyl ether was charged, the pressure in the system was set to 340 mmHg, and the mixture was heated with an oil bath while stirring. When the oil bath temperature was controlled at a constant 95 ° C., the temperature of the kettle liquid was 80 ° C. at the beginning and 85 ° C. at the end of the reaction. Methanol produced as a by-product of the reaction was intermittently distilled from the top of the distillation column as a methanol-methyl methacrylate azeotrope. During this time, no occurrence of polymerization was observed. The reaction was completed in 6 hours to obtain 174 g of a reaction mixture containing about 42% of cyclohexyl methacrylate.
[0025]
[Synthesis Example 2]
The reaction was conducted in the same manner as in Synthesis Example 1 except that 2 g of lithium hydroxide (corresponding to 2900 ppm as the amount of charged Li) was used as a catalyst and methanol-methyl methacrylate azeotrope was continuously distilled. . During this time, no occurrence of polymerization was observed. The reaction was completed in 1 hour to obtain 175 g of a reaction mixture containing about 40% of cyclohexyl methacrylate.
[0026]
[Synthesis Example 3]
The reaction was conducted in the same manner as in Synthesis Example 1 except that 1 g of lithium hydroxide (corresponding to 1450 ppm as the amount of charged Li) was used as a catalyst and the methanol-methyl methacrylate azeotrope was continuously distilled. . During this time, no occurrence of polymerization was observed. The reaction was completed in 2 hours to obtain 174 g of a reaction mixture containing about 41% of cyclohexyl methacrylate.
[0027]
[Synthesis Example 4]
In the same manner as in Synthesis Example 1, except that 0.1 g of 4-oxo-2,2,6,6-tetramethyl-1-piperidinooxyl was added as a polymerization inhibitor in addition to 0.1 g of hydroquinone monomethyl ether. Reaction was performed. During this time, no occurrence of polymerization was observed. The reaction was completed in 6 hours to obtain 174 g of a reaction mixture containing about 42% of cyclohexyl methacrylate.
[0028]
[Example 1]
174 g of the reaction mixture obtained in Synthesis Example 1 was filtered through a 5C filter to obtain 171 g of a reaction filtrate containing about 43% by weight of cyclohexyl methacrylate. As a result of analyzing this reaction filtrate with an ICP emission spectrometer (manufactured by Rigaku Corporation, JY-138, hereinafter abbreviated as ICP), Li was contained at 32 ppm. 140 g of this was put into a 300 ml three-necked flask equipped with a thermometer, distillation column and stirrer, and 4-oxo-2,2,6,6-tetramethyl-1-piperidinooxyl 0 as a polymerization inhibitor. 0.03 g was charged, the pressure was set to 40 mmHg, and methyl methacrylate was distilled in 1 hour. Further, the pressure was 10 mmHg, the fractionation tower top temperature was 83 to 88 ° C., and cyclohexyl methacrylate was distilled in 8 hours. During this time, no polymerization was observed. The obtained cyclohexyl methacrylate was 55 g and the purity was 99.7%.
[0029]
[Example 2]
Distillation was performed in the same manner as in Example 1 except that the reaction mixture of Synthesis Example 1 was charged as it was without filtration. Since all of the charged Li remains, the remaining amount of Li corresponds to 290 ppm. Generation | occurrence | production of the polymer was not recognized during distillation, and the obtained cyclohexyl methacrylate was 53g and the purity was 99.6%.
[0030]
[Example 3]
175 g of the reaction mixture obtained in Synthesis Example 2 was filtered through a 5C filter to obtain 170 g of a reaction filtrate containing about 43% by weight of cyclohexyl methacrylate. As a result of analyzing the reaction filtrate by ICP, 182 ppm of Li was contained. 140 g of this was distilled by the same method as in Example 1. Generation | occurrence | production of the polymer was not recognized during distillation, and the obtained cyclohexyl methacrylate was 52g, and the purity was 99.5%.
[0031]
[Example 4]
As it viewed charged reaction mixture in Synthesis Example 3 without filtration and distilled in real Example 1 and the same method. Since all of the charged Li remains, the remaining amount of Li corresponds to 1450 ppm. Generation | occurrence | production of the polymer was not recognized during distillation, and the obtained cyclohexyl methacrylate was 50g, and the purity was 99.5%.
[0032]
[Example 5]
The reaction mixture of Synthesis Example 4 was charged as it was without filtration, and distilled in the same manner as in Example 1 except that no polymerization inhibitor was added during distillation. Since all of the charged Li remains, the remaining amount of Li corresponds to 290 ppm. Generation | occurrence | production of the polymer was not recognized during distillation, and the obtained cyclohexyl methacrylate was 54g and the purity was 99.6%.
[0033]
[Example 6]
0.015 g of 4-oxo-2,2,6,6-tetramethyl-1-piperidinooxyl, which is a polymerization inhibitor, is charged into a kettle, and 0.015 g is dissolved in 9 g of cyclohexyl methacrylate from the middle stage of the distillation column. The product was distilled in the same manner as in Example 1, except that 1 g per hour was introduced in 9 portions. The remaining amount of Li is 32 ppm. Generation | occurrence | production of the polymer was not recognized during distillation, and the obtained cyclohexyl methacrylate was 62g (including the introduce | transduced cyclohexyl methacrylate), and the purity was 99.6%.
[0034]
[Comparative Example 1]
Distillation was started in the same manner as in Example 1 except that the reaction mixture of Synthesis Example 2 was charged as it was without being filtered, but cyclohexyl methacrylate was found in the distillation column about 3 hours after the start of distillation of cyclohexyl methacrylate. Distillation could not be continued because the distillation column was blocked by popcorn polymerization. Since all of the charged Li remains, the remaining amount of Li corresponds to 2900 ppm.
[0035]
[Comparative Example 2]
Distillation was started in the same manner as in Example 1 except that the polymerization inhibitor was hydroquinone monomethyl ether, but the viscosity of the flask increased at the stage of distilling methyl methacrylate, making it impossible to continue distillation. It was. The remaining amount of Li is 32 ppm.
[0036]
[Comparative Example 3]
Distillation was started in the same manner as in Example 1 except that the polymerization inhibitor was phenothiazine, but cyclohexyl methacrylate was popcorn polymerized in the distillation column in about 4 hours after the start of distillation of cyclohexyl methacrylate, and the distillation column was blocked. As a result, the distillation could not be continued. The remaining amount of Li is 32 ppm.
[0037]
【The invention's effect】
According to the method of the present invention, in the industrial production of cyclohexyl methacrylate by transesterification, the industrial production of cyclohexyl methacrylate does not require any special operation and does not cause substantial polymerization in the process from synthesis to distillation. A manufacturing method can be provided.
Claims (3)
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP11642398A JP4137228B2 (en) | 1998-04-27 | 1998-04-27 | Method for producing cyclohexyl methacrylate |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP11642398A JP4137228B2 (en) | 1998-04-27 | 1998-04-27 | Method for producing cyclohexyl methacrylate |
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| Publication Number | Publication Date |
|---|---|
| JPH11302223A JPH11302223A (en) | 1999-11-02 |
| JP4137228B2 true JP4137228B2 (en) | 2008-08-20 |
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| Application Number | Title | Priority Date | Filing Date |
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| JP11642398A Expired - Lifetime JP4137228B2 (en) | 1998-04-27 | 1998-04-27 | Method for producing cyclohexyl methacrylate |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| JP2000072718A (en) * | 1998-09-01 | 2000-03-07 | Mitsubishi Rayon Co Ltd | Polymerization inhibitor for (meth)acrylate ester comprising (meth)acrylate priperidine-1-oxyl ester derivative and its production |
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| DE2744641B2 (en) * | 1977-10-04 | 1979-08-02 | Deutsche Gold- Und Silber-Scheideanstalt Vormals Roessler, 6000 Frankfurt | Process for the preparation of esters of methacrylic acid |
| JPS5846496B2 (en) * | 1979-09-07 | 1983-10-17 | 大阪有機化学工業株式会社 | Method for preventing popcorn polymerization of α,β-unsaturated carboxylic acid esters |
| JPH02101043A (en) * | 1988-10-06 | 1990-04-12 | Hitachi Chem Co Ltd | Production of methacrylic acid ester |
| JPH03106847A (en) * | 1989-09-20 | 1991-05-07 | Hitachi Chem Co Ltd | Production of methacrylic acid ester |
| JP2725593B2 (en) * | 1993-04-15 | 1998-03-11 | 株式会社日本触媒 | Method for preventing polymerization of (meth) acrylic acid and its ester |
| JP2725638B2 (en) * | 1994-06-02 | 1998-03-11 | 株式会社日本触媒 | Method for preventing polymerization of (meth) acrylic acid and its ester |
| AU743962B2 (en) * | 1997-08-29 | 2002-02-14 | Rohm And Haas Company | Transesterification process |
| JP2949150B1 (en) * | 1998-02-27 | 1999-09-13 | 日精化学工業株式会社 | Method for producing cyclohexyl methacrylate |
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