JP2016183133A - Method for preventing polymerization of acrylic acid and ester thereof - Google Patents
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本発明は、アクリル酸及びそのエステルの重合防止方法に関する。 The present invention relates to a method for preventing polymerization of acrylic acid and esters thereof.
アクリル酸及びそのエステルは有機高分子材料や各種有機素材の原料として広く利用されており、近年その利用分野が拡大するに伴い、より純度の高い製品が求められるようになってきている。ところで、アクリル酸及びそのエステルは光や熱によって自然重合し易い性質を持っているため、その保存中や製造時、特に精製を目的とした蒸留操作において重合の抑制が不可欠である。そのため、これまでに重合を防止するための種々重合防止剤の使用について検討がなされている。 Acrylic acid and its esters are widely used as raw materials for organic polymer materials and various organic materials, and in recent years, as the field of use expands, products with higher purity have been demanded. By the way, since acrylic acid and its ester have the property of being easily polymerized by light and heat, it is indispensable to suppress polymerization during the storage and production, particularly in the distillation operation for the purpose of purification. Therefore, the use of various polymerization inhibitors for preventing polymerization has been studied so far.
古くから知られている重合防止剤としてはハイドロキノン、メトキノン（ｐ−メトキシフェノール）、ジアルキルジチオカルバミン酸銅等が挙げられる。特許文献１には、アクリル酸またはアクリル酸エステルの重合防止剤としてフェノール化合物及び／又はアミン化合物と銅塩化合物とを組合せることが開示されている。特許文献２には、α、β不飽和カルボン酸の重合防止剤として、マンガン塩と、ハイドロキノンおよび／またはメトキノンを併せて用いる方法が開示されている。特許文献３には、ビニル化合物の重合防止剤としてジチオカルバミン酸マンガン塩又はチウラム類を用いる方法が開示されている。 Examples of polymerization inhibitors that have been known for a long time include hydroquinone, methoquinone (p-methoxyphenol), copper dialkyldithiocarbamate, and the like. Patent Document 1 discloses that a phenol compound and / or an amine compound and a copper salt compound are combined as a polymerization inhibitor for acrylic acid or an acrylate ester. Patent Document 2 discloses a method in which a manganese salt and hydroquinone and / or methoquinone are used in combination as a polymerization inhibitor for α and β unsaturated carboxylic acids. Patent Document 3 discloses a method using manganese dithiocarbamate or thiuram as a polymerization inhibitor for vinyl compounds.
また、特許文献４には、アクリル酸の安定化剤として置換基を有するニトロキシドが開示されている。特許文献５では、（メタ）アクリル酸およびそのエステルの重合防止剤として特定のＮ−オキシル化合物とフェノール化合物とフェノチアジン化合物を併用することが記載されている。特許文献６では、Ｎ−オキシル化合物と、マンガン塩化合物、銅塩化合物、２，２，６，６−テトラメチルピペリジン化合物及びニトロソ化合物よりなる群より選択される１種以上を併用することが開示されている。 Patent Document 4 discloses a nitroxide having a substituent as a stabilizer for acrylic acid. Patent Document 5 describes that a specific N-oxyl compound, a phenol compound, and a phenothiazine compound are used in combination as a polymerization inhibitor for (meth) acrylic acid and its ester. Patent Document 6 discloses that N-oxyl compounds are used in combination with one or more selected from the group consisting of manganese salt compounds, copper salt compounds, 2,2,6,6-tetramethylpiperidine compounds and nitroso compounds. Has been.
しかしながら、従来技術により得られる重合防止方法としては、例えば、フェノール化合物又はアミン化合物とＮ−オキシル化合物を併用しており、重合防止効果は有するものの、重合防止効果にバラツキがあり、加えて長期間重合防止効果が継続しないものであった。
特に連続的にアクリル酸及び／又はそのエステルを製造する製造工程において重合防止効果の変動や低下があった場合、例えそれが短期間であっても、製造機器中に重合物を析出させる可能性があり、該重合物から更に重合が進行し、製造機器の閉塞等による製造圧力の上昇を引き起こし、連続製造が困難となる可能性がある。上記に対して、重合防止剤量を増量する方法が考えられるが、経済的に満足できるものではない。
However, as a polymerization prevention method obtained by the prior art, for example, a phenol compound or an amine compound and an N-oxyl compound are used in combination, and although there is a polymerization prevention effect, there is a variation in the polymerization prevention effect, and in addition, for a long period of time. The effect of preventing polymerization was not continued.
In particular, when there is a fluctuation or decrease in the polymerization prevention effect in the production process for continuously producing acrylic acid and / or its ester, there is a possibility of depositing a polymer in production equipment even if it is a short period of time. There is a possibility that the polymerization further proceeds from the polymer, causing an increase in production pressure due to blockage of production equipment and the like, making continuous production difficult. In contrast to the above, a method of increasing the amount of the polymerization inhibitor can be considered, but it is not economically satisfactory.
本発明は上記事情に鑑みてなされたものであり、アクリル酸及び／又はそのエステルを含有する溶液が重合しやすい条件下、例えば、アクリル酸及び／又はそのエステルの製造におけるアクリル酸及び／又はそのエステルを含有する溶液を蒸留するような高温状態であっても、長期間、安定的に重合防止性能を維持し続ける重合防止方法とすることを目的とする。 The present invention has been made in view of the above circumstances. For example, acrylic acid and / or its ester in the production of acrylic acid and / or its ester can be polymerized under a condition in which a solution containing acrylic acid and / or its ester is easily polymerized. It is an object of the present invention to provide a polymerization prevention method that maintains a polymerization prevention performance stably for a long period of time even in a high temperature state where a solution containing an ester is distilled.
本発明者らは、研究を重ねた結果、Ｎ-オキシル化合物は、フェノール化合物やアミン
化合物等の重合防止剤とは異なり、重合防止剤溶液調製時の操作・手順により重合防止効果に違いが生じることを見出した。すなわち、Ｎ−オキシル化合物と特定の重合防止剤とを含む重合防止剤をアクリル酸及び／又はそのエステルを含有する溶液に添加する際に特定の手順で行うことにより、前記課題を解決したのである。
すなわち、本発明の要旨は下記［１］〜［５］に存する。
［１］重合防止剤溶液をアクリル酸及び／又はそのエステルを含有する溶液に添加する重合防止方法において、
下記一般式（１）で表されるＮ−オキシル化合物と、アミン化合物、フェノール化合物及び銅塩化合物からなる群より選ばれた少なくとも１種の化合物とを溶媒に溶解し、溶存酸素の飽和率が０．１％〜２０％である重合防止剤溶液を調製し、
調製した該重合防止剤溶液を２時間〜３０時間の範囲内で保持した後に、アクリル酸及び／又はそのエステルを含有する溶液に添加する重合防止方法。
As a result of repeated research, the present inventors have found that N-oxyl compounds differ from polymerization inhibitors such as phenol compounds and amine compounds in that the polymerization prevention effect differs depending on the procedure and procedure during the preparation of the polymerization inhibitor solution. I found out. That is, when the polymerization inhibitor containing an N-oxyl compound and a specific polymerization inhibitor is added to a solution containing acrylic acid and / or its ester, the above-mentioned problem is solved. .
That is, the gist of the present invention resides in the following [1] to [5].
[1] In a polymerization prevention method of adding a polymerization inhibitor solution to a solution containing acrylic acid and / or an ester thereof,
An N-oxyl compound represented by the following general formula (1) and at least one compound selected from the group consisting of an amine compound, a phenol compound and a copper salt compound are dissolved in a solvent, and the saturation rate of dissolved oxygen is Preparing a polymerization inhibitor solution of 0.1% to 20%,
A polymerization prevention method comprising adding the prepared polymerization inhibitor solution to a solution containing acrylic acid and / or an ester thereof after holding the solution within a range of 2 hours to 30 hours.
（式中Ａは、ＣＨ２、ＣＨＯＨ、Ｃ＝Ｏ、ＣＨＯＣＯＣＨ３又はＣＨＮＨＣＯＣＨ３を示す）
［２］前記アミン化合物、フェノール化合物及び銅塩化合物からなる群より選ばれた少なくとも１種の化合物がアミン化合物である［１］に記載の重合防止方法。
［３］前記重合防止剤溶液における、前記一般式（１）で表されるＮ−オキシル化合物量に対するアミン化合物、フェノール化合物及び銅塩化合物からなる群より選ばれた少なくとも１種の化合物量が１ｗｔ％以上である［１］又は［２］に記載の重合防止方法。
［４］前記重合防止剤溶液を調製する温度が４０℃以下である［１］乃至［３］のいずれかに記載の重合防止方法。
［５］前記重合防止剤溶液を保持する温度が４０℃以下である［１］乃至［４］のいずれかに記載の重合防止方法。
(In the formula, A represents CH 2 , CHOH, C═O, CHOCOCH 3 or CHNHCOCH 3 )
[2] The polymerization prevention method according to [1], wherein at least one compound selected from the group consisting of the amine compound, the phenol compound, and the copper salt compound is an amine compound.
[3] The amount of at least one compound selected from the group consisting of an amine compound, a phenol compound, and a copper salt compound with respect to the amount of the N-oxyl compound represented by the general formula (1) in the polymerization inhibitor solution is 1 wt. % Of polymerization prevention method according to [1] or [2].
[4] The polymerization prevention method according to any one of [1] to [3], wherein the temperature for preparing the polymerization inhibitor solution is 40 ° C. or lower.
[5] The polymerization prevention method according to any one of [1] to [4], wherein the temperature for holding the polymerization inhibitor solution is 40 ° C. or lower.
本発明の重合防止方法によれば、該重合防止方法により得られたアクリル酸及び／又はそのエステルを含有する溶液は、例えばアクリル酸製造工程の蒸留のような重合しやすい条件下であったとしても、重合防止性能を長期間安定して発現させることが可能となり、重合防止効果を常に高く維持し、長期にわたって安定的にアクリル酸及び／又はそのエステルの製造等に寄与することができる。 According to the polymerization preventing method of the present invention, the solution containing acrylic acid and / or ester thereof obtained by the polymerization preventing method is assumed to be under conditions that facilitate polymerization, such as distillation in an acrylic acid production process. In addition, it is possible to stably exhibit the polymerization preventing performance for a long period of time, maintain the polymerization preventing effect at a high level, and contribute to the production of acrylic acid and / or its ester stably over a long period of time.
以下、本発明の実施の態様について詳細に説明する。
本発明方法により重合防止する対象はアクリル酸及び／又はそのエステルであるが、そのアクリル酸エステルとしては、アクリル酸のメチル、エチル、プロピル、ブチル、２−エチルヘキシルエステル等のアルキルエステルが挙げられ、２−ヒドロキシエチル、２−ヒドロキシプロピル等の置換アルキルエステルであってもよい。
Hereinafter, embodiments of the present invention will be described in detail.
The target to be polymerized by the method of the present invention is acrylic acid and / or its ester. Examples of the acrylic ester include alkyl esters such as methyl, ethyl, propyl, butyl, 2-ethylhexyl ester of acrylic acid, A substituted alkyl ester such as 2-hydroxyethyl and 2-hydroxypropyl may be used.
（重合防止剤）
本発明の重合防止方法における重合防止剤の一つであるＮ−オキシル化合物は下記一般式（１）で表される化合物である。
(Polymerization inhibitor)
The N-oxyl compound which is one of the polymerization inhibitors in the polymerization prevention method of the present invention is a compound represented by the following general formula (1).
（式中Ａは、ＣＨ２、ＣＨＯＨ、Ｃ＝Ｏ、ＣＨＯＣＯＣＨ３又はＣＨＮＨＣＯＣＨ３を示す）
上記一般式（１）で表される化合物の中でも２，２，６，６−テトラメチルピペリジン−１−オキシル、２，２，６，６−テトラメチル−４−ヒドロキシピペリジン−１−オキシル、２，２，６，６，−テトラメチル−４−オキソピペリジン−１−オキシルが好ましい。これらの化合物は単独でも、或いは少なくとも２種組み合わせて使用することができる。上記一般式（１）で表されるＮ−オキシル化合物（以下、「Ｎ−オキシル化合物」と称する場合がある。）のアクリル酸及び／又はそのエステルを含有する溶液への添加量は、当該Ｎ−オキシル化合物の種類、アクリル酸及び／又はそのエステルの種類、或いはアクリル酸及び／又はそのエステルを含有する溶液が受ける温度等の適用条件によっても異なるが、アクリル酸及び／又はそのエステルの総量に対して、通常、１〜３００００重量ｐｐｍ、好ましくは、１０〜１０００重量ｐｐｍ、さらに好ましくは、３０〜３００重量ｐｐｍの範囲である。前記範囲とすることにより低コストで十分な重合防止効果を発現することができる可能性がある。
(In the formula, A represents CH 2 , CHOH, C═O, CHOCOCH 3 or CHNHCOCH 3 )
Among the compounds represented by the general formula (1), 2,2,6,6-tetramethylpiperidine-1-oxyl, 2,2,6,6-tetramethyl-4-hydroxypiperidine-1-oxyl, , 2,6,6, -tetramethyl-4-oxopiperidine-1-oxyl is preferred. These compounds can be used alone or in combination of at least two kinds. The amount of N-oxyl compound represented by the general formula (1) (hereinafter sometimes referred to as “N-oxyl compound”) to the solution containing acrylic acid and / or its ester is N -Depending on the application conditions such as the type of oxyl compound, the type of acrylic acid and / or its ester, or the temperature experienced by the solution containing the acrylic acid and / or its ester, the total amount of acrylic acid and / or its ester On the other hand, it is usually in the range of 1 to 30000 ppm by weight, preferably 10 to 1000 ppm by weight, and more preferably 30 to 300 ppm by weight. By setting it in the above range, there is a possibility that a sufficient polymerization preventing effect can be exhibited at low cost.
尚、該Ｎ−オキシル化合物は対応するピペリジン化合物を原料として製造される（例えば、２，２，６，６−テトラメチル−４− ヒドロキシピペリジンを原料として２，２，
６，６−テトラメチル−４−ヒドロキシピペリジン−１− オキシルが製造される）が、
本発明の重合防止方法における重合防止剤溶液には該ピペリジン化合物を含有していてもよい。該ピペリジン化合物の有無、又その濃度に関わらず、本発明の効果が影響を受ける可能性はない。
The N-oxyl compound is produced from the corresponding piperidine compound as a raw material (for example, 2,2,6,6-tetramethyl-4-hydroxypiperidine as a raw material, 2,2,
6,6-tetramethyl-4-hydroxypiperidine-1-oxyl is produced)
The piperidine compound may be contained in the polymerization inhibitor solution in the polymerization prevention method of the present invention. Regardless of the presence or absence of the piperidine compound and its concentration, the effects of the present invention are not likely to be affected.
本発明の重合防止方法における重合防止剤は更にアミン化合物、フェノール化合物及び銅塩化合物からなる群より選ばれた少なくとも１種の化合物（以下「他の重合防止剤」と称する場合がある。）を含む。
アミン化合物としては、ジフェニルアミン、フェニレンジアミン、フェノチアジン等が挙げられ、フェノール化合物としては、ハイドロキノン、メトキシキノン等が挙げられ、
銅塩化合物としては酢酸銅、炭酸銅、アクリル酸銅、ジアルキルジチオカルバミン酸銅塩等が挙げられる。他の重合防止剤の中でもアミン化合物及び銅塩化合物からなる群より選ばれた少なくとも１種の化合物であることが好ましく、フェノチアジン、酢酸銅、炭酸銅及びアクリル酸銅からなる群より選ばれた少なくとも１種の化合物がより好ましく、フェノチアジンであることがさらに好ましい。
また、前記以外の重合防止剤として、例えば、マンガン塩等の金属塩やチウラム類を該重合防止剤溶液に溶解しても良い。
The polymerization inhibitor in the polymerization prevention method of the present invention is at least one compound selected from the group consisting of an amine compound, a phenol compound and a copper salt compound (hereinafter sometimes referred to as “other polymerization inhibitor”). Including.
Examples of the amine compound include diphenylamine, phenylenediamine, and phenothiazine. Examples of the phenol compound include hydroquinone and methoxyquinone.
Examples of the copper salt compound include copper acetate, copper carbonate, copper acrylate, and dialkyldithiocarbamic acid copper salt. Among other polymerization inhibitors, it is preferably at least one compound selected from the group consisting of amine compounds and copper salt compounds, and at least selected from the group consisting of phenothiazine, copper acetate, copper carbonate and copper acrylate. One compound is more preferred, and phenothiazine is even more preferred.
Further, as a polymerization inhibitor other than the above, for example, a metal salt such as a manganese salt or thiuram may be dissolved in the polymerization inhibitor solution.
（重合防止剤溶液の調製）
本発明の重合防止方法では当該Ｎ−オキシル化合物と他の重合防止剤を溶媒に溶解し、溶存酸素の飽和率が特定範囲である重合防止剤溶液とする。溶媒とは、当該Ｎ−オキシル化合物と他の重合防止剤を溶解するものであれば、公知の溶媒を用いることができるが、主成分が有機化合物である溶媒か、主成分が水である溶媒が好ましい。有機化合物としてはヘキサン、ヘプタンなどの脂肪族炭化水素、トルエン、キシレンなどの芳香族炭化水素、ジブチルエーテル等のエーテル類、メチルイソブチルケトン、メチルｔｅｒｔ−ブチルケトン等のケトン類、酢酸イソプロピル、アクリル酸ブチル等のエステル類、エタノール、ブタノール等のアルコール類、等が挙げられ、中でも芳香族炭化水素、エステル類、アルコール類が好ましい。主成分が有機化合物である溶媒とすることにより重合防止剤が親油性を有する場合に、容易に重合防止剤溶液とすることができる。又、主成分が水である溶媒とすることにより重合防止剤が親水性を有する場合に、容易に重合防止剤溶液とすることが可能となる。尚、ここでいう主成分とは溶媒全量中、含有量が最も多い成分であることをいう。
(Preparation of polymerization inhibitor solution)
In the polymerization prevention method of the present invention, the N-oxyl compound and other polymerization inhibitors are dissolved in a solvent to obtain a polymerization inhibitor solution having a specific oxygen saturation rate. As the solvent, a known solvent can be used as long as it dissolves the N-oxyl compound and other polymerization inhibitor, but a solvent whose main component is an organic compound or a solvent whose main component is water. Is preferred. Organic compounds include aliphatic hydrocarbons such as hexane and heptane, aromatic hydrocarbons such as toluene and xylene, ethers such as dibutyl ether, ketones such as methyl isobutyl ketone and methyl tert-butyl ketone, isopropyl acetate, and butyl acrylate. And esters such as ethanol, butanols such as ethanol and butanol. Aromatic hydrocarbons, esters and alcohols are preferred. By using a solvent whose main component is an organic compound, a polymerization inhibitor solution can be easily formed when the polymerization inhibitor has lipophilicity. Further, when the polymerization inhibitor is hydrophilic by using a solvent whose main component is water, a polymerization inhibitor solution can be easily formed. The main component here means a component having the largest content in the total amount of the solvent.
前記重合防止剤溶液は溶存酸素の飽和率が特定範囲内である。主成分が有機化合物である溶媒の場合、重合防止剤溶液の溶存酸素の飽和率が０．１％〜２０％であり、０．５％〜１５％が好ましく、１％〜１０％がより好ましい。
主成分が水である溶媒の場合、重合防止剤溶液の溶存酸素の飽和率は０．１％〜２０％であり、０．５％〜１５％が好ましく、１％〜１０％がより好ましい。
The polymerization inhibitor solution has a saturation rate of dissolved oxygen within a specific range. In the case of a solvent whose main component is an organic compound, the saturation rate of dissolved oxygen in the polymerization inhibitor solution is 0.1% to 20%, preferably 0.5% to 15%, more preferably 1% to 10%. .
In the case of a solvent whose main component is water, the saturation rate of dissolved oxygen in the polymerization inhibitor solution is 0.1% to 20%, preferably 0.5% to 15%, more preferably 1% to 10%.
尚、溶存酸素の飽和率とは、酸素分圧１気圧における、飽和状態で溶解している溶液中の酸素量に対する、対象溶液中の酸素量を指し、溶存酸素濃度計により測定することができる。
重合防止剤溶液の溶存酸素の飽和率を特定範囲とする方法は例えば、酸素含有ガス雰囲気下で当該Ｎ−オキシル化合物を溶媒に溶解させる方法、溶媒に溶存酸素を含有させた後に、当該Ｎ−オキシル化合物を溶解する方法等が挙げられる。尚、使用する酸素含有ガスとしては、純酸素ガスをそのまま使用してもよいが、重合防止剤溶液調製時の気相部が爆発範囲内となることを防ぐため、又、溶存酸素の飽和率が上限を超えることを防ぐため、窒素等の不活性ガスで希釈する方法が挙げられ、経済的には空気あるいは不活性ガスによる希釈空気を用いるのが好ましい。酸素含有ガスの供給方法については特に制限されず、ノズル等を用いてバブリングなどにより溶媒あるいは重合防止剤溶液に直接混入させてもよいし、溶解装置の気相部に酸素含有ガスを置換、密閉し或いは他の溶媒に酸素を溶解した状態で間接的に供給することも出来る。該バブリングの効率を高める為、ノズル先端に焼結金属等を設けることも出来る。
The saturation rate of dissolved oxygen refers to the amount of oxygen in the target solution with respect to the amount of oxygen in the solution dissolved in a saturated state at an oxygen partial pressure of 1 atm, and can be measured with a dissolved oxygen concentration meter. .
Examples of the method for setting the saturation rate of dissolved oxygen in the polymerization inhibitor solution to a specific range include, for example, a method of dissolving the N-oxyl compound in a solvent under an oxygen-containing gas atmosphere, Examples include a method for dissolving an oxyl compound. As the oxygen-containing gas to be used, pure oxygen gas may be used as it is, but in order to prevent the gas phase part at the time of preparing the polymerization inhibitor solution from being in the explosion range, the saturation rate of dissolved oxygen In order to prevent this from exceeding the upper limit, a method of diluting with an inert gas such as nitrogen can be mentioned, and it is preferable to use air or diluted air with an inert gas from the economical viewpoint. The method for supplying the oxygen-containing gas is not particularly limited, and may be directly mixed into the solvent or the polymerization inhibitor solution by bubbling using a nozzle or the like, or the oxygen-containing gas is replaced and sealed in the gas phase portion of the dissolution apparatus. Alternatively, it can be indirectly supplied in a state where oxygen is dissolved in another solvent. In order to increase the efficiency of the bubbling, a sintered metal or the like can be provided at the nozzle tip.
調製される重合防止剤溶液中の重合防止剤濃度が高いほど、重合防止剤の溶解や該重合防止剤溶液のアクリル酸及び／又はそのエステルを含有する溶液への添加に要する機器が小さくて済み、又同じ大きさの槽であれば、より大量のアクリル酸及び／又はそのエステルを含有する溶液に対する重合防止剤溶液を調製できる為、液温の変動による重合防止剤の析出等を考慮した上で、溶解度の高い溶媒を選択し、高濃度で調製するのが一般的である。 The higher the concentration of the polymerization inhibitor in the prepared polymerization inhibitor solution, the smaller the equipment required for dissolving the polymerization inhibitor and adding the polymerization inhibitor solution to the solution containing acrylic acid and / or its ester. In addition, since the polymerization inhibitor solution for a solution containing a larger amount of acrylic acid and / or its ester can be prepared if the tanks are the same size, the precipitation of the polymerization inhibitor due to fluctuations in the liquid temperature is taken into consideration. In general, a solvent having high solubility is selected and prepared at a high concentration.
一つの調製槽により、複数種の重合防止剤を溶解し、重合防止剤溶液とする場合、各々の重合防止剤に適した溶媒を選択することが出来ず、調製が困難となる。又、一度に重合防止剤の添加比率が異なる複数ヶ所に重合防止剤溶液を添加する場合にも、一つの調製槽では限界が生じる。
上記の様な場合には、各重合防止剤に応じて調製槽を設ける、添加箇所に応じて調製槽を設けることが好ましい。
When a plurality of types of polymerization inhibitors are dissolved in one preparation tank to form a polymerization inhibitor solution, a solvent suitable for each polymerization inhibitor cannot be selected, making preparation difficult. Even when the polymerization inhibitor solution is added to a plurality of locations where the addition ratio of the polymerization inhibitor is different at one time, there is a limit in one preparation tank.
In such a case, it is preferable to provide a preparation tank according to each polymerization inhibitor, and to provide a preparation tank according to an addition location.
当該Ｎ−オキシル化合物と他の重合防止剤を溶媒に溶解して重合防止剤溶液とする方法は、例えば、以下の４方法が挙げられる。
（１）一つの調製槽に当該Ｎ−オキシル化合物と他の重合防止剤を投入して溶解し、重合防止剤溶液とする方法
（２）一つの調製槽に当該Ｎ−オキシル化合物の溶液を調製し、別の調製槽に他の重合防止剤の溶液を調製し、前記二つの溶液を混合し、重合防止剤溶液とする方法
（３）一つの調製槽に当該Ｎ−オキシル化合物の溶液を調製し、該溶液に他の重合防止剤を投入、溶解し重合防止剤溶液とする方法
（４）一つの調製槽に他の重合防止剤の溶液を調製し、該溶液に当該Ｎ−オキシル化合物を投入、溶解し重合防止剤溶液とする方法
上記の中でも（２）の方法のように各重合防止剤毎に溶液を調製するのが設備面で効率的である。
Examples of the method for dissolving the N-oxyl compound and other polymerization inhibitor in a solvent to form a polymerization inhibitor solution include the following four methods.
(1) A method in which the N-oxyl compound and another polymerization inhibitor are put into one preparation tank and dissolved to form a polymerization inhibitor solution. (2) A solution of the N-oxyl compound is prepared in one preparation tank. A method of preparing another polymerization inhibitor solution in another preparation tank and mixing the two solutions to obtain a polymerization inhibitor solution (3) Preparing a solution of the N-oxyl compound in one preparation tank (4) A solution of another polymerization inhibitor is prepared in one preparation tank, and the N-oxyl compound is added to the solution. Method of charging and dissolving to form a polymerization inhibitor solution Among the above, it is efficient in terms of equipment to prepare a solution for each polymerization inhibitor as in the method (2).
調製槽は特に制限はなく、従来の一般的な調製槽を用いればよい。固体の当該Ｎ−オキシル化合物や他の重合防止剤を溶媒に溶解させるため、攪拌翼を備えているもの、または配管等により溶液を強制循環かけられるものが好ましい。
又、調製槽への重合防止剤の投入方法は、当該Ｎ−オキシル化合物や他の重合防止剤を調製槽内に直接投入しても良いし、調製槽内に網かごを設置しておいてその中に投入し、網かご内で溶解させても良い。調製槽は単純な１槽タイプでも、中に仕切りがある２槽タイプでもよい。２槽タイプを用いた場合、例えば、１槽目で他の重合防止剤の溶液を調製し、該溶液を２槽目に送り、２槽目において当該Ｎ−オキシル化合物を投入、溶解し重合防止剤溶液とする、又は１槽目で他の重合防止剤の溶液を調製し、該溶液を２槽目に送り、２槽目で、別の溶解装置で調製した当該Ｎ−オキシル化合物の溶液と混合し重合防止剤溶液とすることができる。また、２槽タイプを用いた場合、１槽目で溶解させた重合防止剤含有液を２槽目に送り、２槽目は製造工程に液を送液する供給槽として用いながら同時に、１槽目で再び重合防止剤の溶解を実施することもできる。
The preparation tank is not particularly limited, and a conventional general preparation tank may be used. In order to dissolve the solid N-oxyl compound and other polymerization inhibitors in a solvent, those equipped with a stirring blade or those capable of forcibly circulating the solution through piping or the like are preferable.
In addition, as for the method of charging the polymerization inhibitor into the preparation tank, the N-oxyl compound or other polymerization inhibitor may be directly charged into the preparation tank, or a net cage is installed in the preparation tank. It may be put into it and dissolved in a mesh basket. The preparation tank may be a simple one tank type or a two tank type with a partition inside. In the case of using the two tank type, for example, a solution of another polymerization inhibitor is prepared in the first tank, the solution is sent to the second tank, and the N-oxyl compound is charged and dissolved in the second tank to prevent polymerization. The solution of the other polymerization inhibitor is prepared in the first tank, the solution is sent to the second tank, and the solution of the N-oxyl compound prepared in a second dissolution apparatus is prepared in the second tank. It can mix and it can be set as a polymerization inhibitor solution. In addition, when the two tank type is used, the polymerization inhibitor-containing liquid dissolved in the first tank is sent to the second tank, while the second tank is used as a supply tank for sending the liquid to the manufacturing process, while simultaneously using one tank. The polymerization inhibitor can also be dissolved again by the eye.
該重合防止剤溶液における当該Ｎ−オキシル化合物量に対する他の重合防止剤量は１ｗｔ％以上が好ましく、１０ｗｔ％以上がより好ましい。前記範囲とすることによりＮ−オキシル化合物の安定性が向上し、重合防止剤溶液として長時間重合防止性能を維持する場合がある。
尚、上限は経済的見地より１０００ｗｔ％である。
The amount of the other polymerization inhibitor relative to the amount of the N-oxyl compound in the polymerization inhibitor solution is preferably 1 wt% or more, and more preferably 10 wt% or more. By setting it as the above range, the stability of the N-oxyl compound is improved, and the polymerization inhibitor performance may be maintained for a long time as a polymerization inhibitor solution.
The upper limit is 1000 wt% from an economic point of view.
重合防止剤溶液を調製する温度は４０℃以下が好ましく、３０℃以下がより好ましい。温度が高すぎるとＮ−オキシル化合物の安定性が低下し、重合防止溶液として長時間重合防止性能を維持できなくなる可能性がある。
前記のように調製した重合防止剤溶液は調製後２時間〜３０時間保持した後に、アクリル酸及び／又はそのエステルを含有する溶液に添加する。保持する時間は２〜３０時間であり、好ましくは２時間〜２４時間であり、より好ましくは２時間〜１８時間である。保持する時間が短すぎても長すぎてもＮ−オキシル化合物の安定性は低下し、重合防止剤溶液として長時間重合防止性能を維持することができなくなる可能性がある。適度な保持する時間があることにより、当該Ｎ−オキシル化合物と他の重合防止剤とにより安定化状態
を形成することができ、長時間、重合防止性能を維持できる可能性がある。
The temperature for preparing the polymerization inhibitor solution is preferably 40 ° C. or lower, and more preferably 30 ° C. or lower. If the temperature is too high, the stability of the N-oxyl compound is lowered, and there is a possibility that the polymerization preventing performance cannot be maintained for a long time as a polymerization preventing solution.
The polymerization inhibitor solution prepared as described above is maintained for 2 to 30 hours after preparation, and then added to a solution containing acrylic acid and / or its ester. The holding time is 2 to 30 hours, preferably 2 to 24 hours, and more preferably 2 to 18 hours. If the holding time is too short or too long, the stability of the N-oxyl compound is lowered, and there is a possibility that the polymerization inhibitor performance cannot be maintained for a long time as a polymerization inhibitor solution. When there is an appropriate holding time, a stable state can be formed by the N-oxyl compound and another polymerization inhibitor, and there is a possibility that the polymerization prevention performance can be maintained for a long time.
尚、重合防止剤溶液を調製槽内に静置しても、調製槽に付帯する循環ラインで調製槽内を液循環させても、調製槽内に具備された撹拌翼で混合操作をされていても「保持」の範囲内である。更に、重合防止剤溶液を調製槽とは別の槽に移送して保持してもよい。
本発明の重合防止方法における重合防止剤溶液は一つの重合防止剤溶液である必要はなく、複数の重合防止剤溶液として、アクリル酸及び／又はそのエステルを含有する溶液へ添加することができる。
Even if the polymerization inhibitor solution is allowed to stand in the preparation tank or is circulated in the preparation tank through a circulation line attached to the preparation tank, the mixing operation is performed with the stirring blade provided in the preparation tank. Even within the range of “hold”. Furthermore, the polymerization inhibitor solution may be transferred to and held in a tank different from the preparation tank.
The polymerization inhibitor solution in the polymerization prevention method of the present invention does not need to be a single polymerization inhibitor solution, and can be added as a plurality of polymerization inhibitor solutions to a solution containing acrylic acid and / or its ester.
複数の重合防止剤溶液とすることにより、例えば、アクリル酸及び／又はそのエステルを含有する溶液へ複数の箇所より添加する場合に効果的である。更に、Ｎ−オキシル化合物量に対する他の重合防止剤量比を変更して複数の溶液とする場合、他の重合防止剤を変更して複数の溶液とする場合、重合防止剤の溶解性等に応じ溶媒を変更し複数の溶液とする場合等に適用できる。尚、複数の重合防止剤溶液との調製については、複数の場合でも前記した調製方法を適用することが好ましい。複数の重合防止剤溶液で添加する場合には、別々の調合槽で重合防止剤溶液を調製した後に、各重合防止剤溶液を個別にアクリル酸及び／又はそのエステルを含有する溶液へ添加してもよいし、各重合防止剤溶液を混合し、一つの重合防止剤溶液として添加してもよい。 By using a plurality of polymerization inhibitor solutions, for example, it is effective when added to a solution containing acrylic acid and / or its ester from a plurality of locations. Furthermore, when changing the other polymerization inhibitor amount ratio with respect to the amount of N-oxyl compound to make a plurality of solutions, when changing another polymerization inhibitor to make a plurality of solutions, the solubility of the polymerization inhibitor etc. Accordingly, the present invention can be applied to a case where the solvent is changed to obtain a plurality of solutions. In addition, about the preparation with a several polymerization inhibitor solution, it is preferable to apply the above-mentioned preparation method even in the case of multiple. When adding a plurality of polymerization inhibitor solutions, after preparing the polymerization inhibitor solution in separate preparation tanks, add each polymerization inhibitor solution individually to a solution containing acrylic acid and / or its ester. Alternatively, each polymerization inhibitor solution may be mixed and added as one polymerization inhibitor solution.
アクリル酸及び／又はそのエステルを含有する溶液へは本発明の重合防止方法における重合防止剤溶液とは別の重合防止剤を添加してもよい。該別の重合防止剤としては、他の重合防止剤、マンガン塩等の金属塩やチウラム類等が挙げられる。別の重合防止剤は溶媒に溶解し、溶液の状態で添加しても、固体の状態で添加してもよい。
本発明による重合防止方法はアクリル酸及び／又はそのエステルを含有する溶液の貯蔵或いは移送する際にも適用されるが、特に高い温度下に付される場合、例えばアクリル酸又はそのエステルの製造において適用されることが好ましい。
A polymerization inhibitor other than the polymerization inhibitor solution in the polymerization prevention method of the present invention may be added to the solution containing acrylic acid and / or its ester. Examples of the other polymerization inhibitor include other polymerization inhibitors, metal salts such as manganese salts, and thiurams. Another polymerization inhibitor is dissolved in a solvent and may be added in a solution state or in a solid state.
The polymerization-preventing method according to the present invention is also applied when storing or transporting a solution containing acrylic acid and / or its ester, but when subjected to a particularly high temperature, for example, in the production of acrylic acid or its ester. Preferably applied.
例えば、アクリル酸の製造は通常、原料である酸素含有ガスとプロピレン等により粗アクリル酸水溶液とし、該粗アクリル酸水溶液を粗アクリル酸と軽沸物に分離する蒸留工程、該粗アクリル酸を更に蒸留精製し、アクリル酸と重質物とに分離する精製工程、更には該重質物を分解する分解工程からなるが、該蒸留工程、該精製工程、該分解工程それぞれに本発明の重合防止方法を適用することにより各工程における重合を長期的、安定的に阻止することができる。 For example, acrylic acid is usually produced by using a raw material oxygen-containing gas and propylene as a crude acrylic acid aqueous solution, a distillation step for separating the crude acrylic acid aqueous solution into crude acrylic acid and a light boiling product, The method comprises a purification step for purification by distillation and separation into acrylic acid and a heavy product, and further a decomposition step for decomposing the heavy product. The polymerization prevention method of the present invention is applied to each of the distillation step, the purification step, and the decomposition step. By applying, polymerization in each step can be stably prevented for a long time.
該蒸留工程、該精製工程では一般的に蒸留塔が使用される。該蒸留工程、該精製工程における重合防止剤溶液の添加は蒸留塔に送液される粗アクリル酸水溶液や粗アクリル酸に添加混合する方法、蒸留塔内の還流液に添加する方法又は蒸留塔の気相部に添加する方法、供給段と塔頂の間に供給口を設け添加する方法等が挙げられる。
該分解工程では一般的に完全混合槽型・循環型完全混合槽型・空洞型等の反応器や、上部に蒸留塔や凝縮器を接続もしくはこれらが一体化されたものが使用される。該分解工程における重合防止剤溶液の添加は該反応器に送液される重質物に添加混合する方法、該反応器内に添加する方法、蒸留塔内の還流液に添加する方法又は蒸留塔の気相部に添加する方法、蒸留塔の供給段と塔頂の間に供給口を設け添加する方法等が挙げられる。上記各工程において重合防止剤溶液を添加する方法は、重合防止剤溶液の持続的な重合防止性能がより発現できる観点で選択されることが好ましい。
In the distillation step and the purification step, a distillation column is generally used. The addition of the polymerization inhibitor solution in the distillation step and the purification step is a method of adding to and mixing with a crude acrylic acid aqueous solution or crude acrylic acid sent to the distillation column, a method of adding to the reflux liquid in the distillation column, or a distillation column Examples thereof include a method of adding to the gas phase part, a method of adding a supply port between the supply stage and the top of the column, and the like.
In the decomposition step, a reactor of a complete mixing tank type, a circulation type complete mixing tank type, a hollow type or the like, or a distillation column or condenser connected to the upper part or an integrated unit is used. In the decomposition step, the polymerization inhibitor solution is added to and mixed with the heavy material sent to the reactor, added to the reactor, added to the reflux liquid in the distillation column, or added to the distillation column. Examples thereof include a method of adding to the gas phase part, a method of adding a supply port between the supply stage of the distillation column and the top of the column, and the like. The method of adding the polymerization inhibitor solution in each of the above steps is preferably selected from the viewpoint that the continuous polymerization prevention performance of the polymerization inhibitor solution can be expressed more.
次いでアクリル酸エステルの製造は通常、アクリル酸とアルコールとを触媒の存在下反応し、アクリル酸エステル反応液とする反応工程、該アクリル酸エステル反応液中の触媒を水で抽出して回収する抽出工程、該アクリル酸エステル反応液からアクリル酸エステルと軽沸分、重質分に分離する精製工程、更には該重質分を分解する分解工程からなるが、
該反応工程、該精製工程、該分解工程それぞれに本発明の重合防止方法を適用することにより各工程における重合を長期的、安定的に阻止することができる。
Next, the production of acrylic ester is usually a reaction step in which acrylic acid and alcohol are reacted in the presence of a catalyst to obtain an acrylic ester reaction liquid, and extraction in which the catalyst in the acrylic ester reaction liquid is extracted and recovered The step, a purification step of separating the acrylate ester reaction solution from the acrylate ester and light boiling and heavy components, and further a decomposition step of decomposing the heavy components,
By applying the polymerization prevention method of the present invention to each of the reaction step, the purification step, and the decomposition step, the polymerization in each step can be stably prevented for a long time.
該反応工程における重合防止剤溶液の添加は、例えば、反応装置に送液される原料に重合防止剤溶液を添加混合する方法、反応装置内に添加する方法又は、蒸留塔を具備した反応装置であれば、該蒸留塔内や該蒸留塔からの還流液に添加する方法が挙げられる。
該精製工程では一般的に蒸留塔が使用される。重合防止剤溶液の添加は蒸留塔に送液される該アクリル酸エステル反応液に添加混合する方法、蒸留塔内の還流液に添加する方法又は蒸留塔頂の気相部に添加する方法、供給段と塔頂の間に供給口を設け添加する方法等が挙げられる。
The addition of the polymerization inhibitor solution in the reaction step is, for example, a method of adding and mixing the polymerization inhibitor solution to the raw material sent to the reaction apparatus, a method of adding the polymerization inhibitor solution to the reaction apparatus, or a reaction apparatus equipped with a distillation column. If there is, there can be mentioned a method of adding to the reflux liquid from the distillation column or from the distillation column.
In the purification step, a distillation column is generally used. The polymerization inhibitor solution is added to and mixed with the acrylate reaction liquid sent to the distillation tower, added to the reflux liquid in the distillation tower, or added to the gas phase at the top of the distillation tower, and supplied. Examples thereof include a method in which a supply port is provided between the stage and the top of the column and added.
該分解工程では一般的に完全混合槽型・循環型完全混合槽型・空洞型等の反応器や、上部に蒸留塔や凝縮器を接続もしくはこれらが一体化されたものが使用される。該分解工程における重合防止剤溶液の添加は該反応器に送液される重質物に添加混合する方法、該反応器内に添加する方法、蒸留塔内の還流液に添加する方法又は蒸留塔の気相部に添加する方法、蒸留塔の供給段と塔頂の間に供給口を設け添加する方法等が挙げられる。上記各工程において重合防止剤溶液を添加する方法は、重合防止剤溶液の持続的な重合防止性能がより発現できる観点で選択されることが好ましい。 In the decomposition step, a reactor of a complete mixing tank type, a circulation type complete mixing tank type, a hollow type or the like, or a distillation column or condenser connected to the upper part or an integrated unit is used. In the decomposition step, the polymerization inhibitor solution is added to and mixed with the heavy material sent to the reactor, added to the reactor, added to the reflux liquid in the distillation column, or added to the distillation column. Examples thereof include a method of adding to the gas phase part, a method of adding a supply port between the supply stage of the distillation column and the top of the column, and the like. The method of adding the polymerization inhibitor solution in each of the above steps is preferably selected from the viewpoint that the continuous polymerization prevention performance of the polymerization inhibitor solution can be expressed more.
前記アクリル酸の製造や前記アクリル酸エステルの製造において、上流工程に比し下流工程におけるアクリル酸及び／又はそのエステルを含有する溶液中の重合防止剤濃度が高くなる傾向にある。例えば、アクリル酸の製造を例にとると、該蒸留工程で粗アクリル酸水溶液に重合防止剤溶液を供給し、蒸留した場合、粗アクリル酸中の重合防止剤濃度は粗アクリル酸水溶液中よりも高くなる。同様に、重質物中の重合防止剤濃度は粗アクリル酸よりも高くなり、重質分解装置出口液中の重合防止剤濃度は重質物よりも高くなる。例えば、重質物中の重合防止剤濃度は粗アクリル酸中に比し３〜１２０倍である。重質分解装置出口液中の重合防止剤濃度は、重質物中の１．５〜１５倍である。但し、該重合防止剤濃度と重合防止効果は必ずしも一致するとは限らない。とりわけ、Ｎ−オキシル化合物は経時的に、特に高温度条件下では重合防止効果の減衰が著しいことより、アクリル酸の製造においては、前記したように工程ごとに重合防止剤溶液を添加することが必要になるのである。 In the production of the acrylic acid and the production of the acrylic ester, the concentration of the polymerization inhibitor in the solution containing acrylic acid and / or its ester in the downstream process tends to be higher than that in the upstream process. For example, taking the production of acrylic acid as an example, when the polymerization inhibitor solution is supplied to the crude acrylic acid aqueous solution in the distillation step and distilled, the concentration of the polymerization inhibitor in the crude acrylic acid is higher than that in the crude acrylic acid aqueous solution. Get higher. Similarly, the concentration of the polymerization inhibitor in the heavy material is higher than that of the crude acrylic acid, and the concentration of the polymerization inhibitor in the heavy decomposition apparatus outlet liquid is higher than that of the heavy material. For example, the concentration of the polymerization inhibitor in the heavy material is 3 to 120 times that in crude acrylic acid. The concentration of the polymerization inhibitor in the heavy cracker outlet liquid is 1.5 to 15 times that in the heavy material. However, the polymerization inhibitor concentration and the polymerization prevention effect do not always coincide. In particular, since the N-oxyl compound has a significant decrease in the polymerization preventing effect over time, particularly under high temperature conditions, in the production of acrylic acid, it is possible to add a polymerization inhibitor solution for each step as described above. It is necessary.
本発明の重合防止方法において、アクリル酸及び／又はそのエステルを含有する溶液に対して重合防止剤溶液の添加に加えて、分子状酸素を添加することが更に重合防止効果を持続することが可能となり、好ましい。分子状酸素の添加はアクリル酸及び／又はそのエステルを含有する溶液に分子状酸素を直接混入する方法、他の溶媒に分子状酸素を溶解し、アクリル酸及び／又はそのエステルを含有する溶液に混入する方法が挙げられるが、経済性の観点より直接混入する方法が好ましい。 In the polymerization prevention method of the present invention, in addition to the addition of the polymerization inhibitor solution to the solution containing acrylic acid and / or its ester, addition of molecular oxygen can further maintain the polymerization prevention effect. It is preferable. Addition of molecular oxygen is a method in which molecular oxygen is directly mixed into a solution containing acrylic acid and / or its ester, or a solution containing acrylic acid and / or its ester is dissolved by dissolving molecular oxygen in another solvent. Although the method of mixing is mentioned, The method of mixing directly from a viewpoint of economical efficiency is preferable.
分子状酸素の添加は、例えば、蒸留塔の場合、蒸留塔の塔底より行う、又は、リボイラーを具備した蒸留塔であれば、リボイラーより添加する方法が挙げられる。
分子状酸素は純酸素ガスを使用する方法、純酸素ガスを窒素等の不活性ガスで希釈して使用する方法、空気を使用する方法等が挙げられるが、経済的観点より空気を使用する方法が好ましい。
For example, in the case of a distillation column, molecular oxygen is added from the bottom of the distillation column, or in the case of a distillation column equipped with a reboiler, a method of adding from a reboiler can be used.
Examples of molecular oxygen include a method using pure oxygen gas, a method using pure oxygen gas diluted with an inert gas such as nitrogen, a method using air, etc., but a method using air from an economic viewpoint. Is preferred.
分子状酸素はアクリル酸及び／又はアクリル酸エステルの蒸留蒸気量に対して０．０５〜１容量％程度供給するのが好ましい。尚、蒸留蒸気量とは蒸留塔のリボイラーから加えられた熱量に相当して、塔底から蒸発するアクリル酸等の蒸気の総量を意味する。 It is preferable to supply about 0.05 to 1% by volume of molecular oxygen with respect to the distillation vapor amount of acrylic acid and / or acrylic ester. The amount of distilled steam corresponds to the amount of heat applied from the reboiler of the distillation column, and means the total amount of vapor such as acrylic acid that evaporates from the bottom of the column.
以下に実施例を挙げて本発明をより具体的に説明するが、本発明はその要旨を超えない限り、以下の実施例により限定されるものではない。
＜溶存酸素の飽和率の測定方法＞
溶存酸素濃度が既知である水で溶存酸素濃度計の更正を実施した後に、重合防止剤溶液の酸素濃度を測定し、下記式により溶存酸素の飽和率を算出した。
溶存酸素の飽和率＝（重合防止剤溶液の酸素濃度／水の飽和溶存酸素濃度）×１００
（実施例１）
塔底部が５００ｍＬガラス製フラスコであり、塔頂部に留出管を備え、中央部に原料供給管を備えた充填塔を用いてアクリル酸水溶液の共沸分離を行った。プロピレンの気相接触酸化反応によって得られた粗製アクリル酸を水で吸収したものにトルエンを加え、モデル的に調製したアクリル酸水溶液を共沸分離の原料（以下「原料（１）」と称する場合がある。）として用いた。原料（１）の組成はアクリル酸６３重量％、トルエン１０重量％、酢酸＝４重量％、水＝２３．０重量％であった。
EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples unless it exceeds the gist.
<Measurement method of saturation rate of dissolved oxygen>
After correcting the dissolved oxygen concentration meter with water having a known dissolved oxygen concentration, the oxygen concentration of the polymerization inhibitor solution was measured, and the saturation rate of dissolved oxygen was calculated by the following formula.
Saturation rate of dissolved oxygen = (oxygen concentration of polymerization inhibitor solution / saturated dissolved oxygen concentration of water) × 100
Example 1
The bottom of the tower was a 500 mL glass flask, a distillation tower was provided at the top of the tower, and an aqueous acrylic acid solution was azeotropically separated using a packed tower provided with a raw material supply pipe at the center. Toluene is added to water obtained by absorbing crude acrylic acid obtained by vapor-phase catalytic oxidation of propylene with water, and a model prepared acrylic acid aqueous solution is referred to as a raw material for azeotropic separation (hereinafter referred to as “raw material (1)”) Used.) The composition of the raw material (1) was 63% by weight of acrylic acid, 10% by weight of toluene, 4% by weight of acetic acid, and 23.0% by weight of water.
原料管にトルエンを仕込み、空気を窒素ガスで体積比１／２に希釈したガスをテフロン（登録商標）チューブにより原料管に吹き込んで３０分ガス置換した後、室温（２３℃）下でフェノチアジンを３０００重量ｐｐｍ加え溶解し、溶液とした(以下「防止剤（１）
」と称する場合がある。)。
Toluene was charged into the raw material tube, and the gas diluted with nitrogen gas to 1/2 the volume ratio was blown into the raw material tube with a Teflon (registered trademark) tube and replaced with gas for 30 minutes. 3000 ppm by weight was added and dissolved to obtain a solution (hereinafter referred to as “inhibitor (1)
May be called. ).
別の原料管にトルエンを仕込み、空気を窒素ガスで体積比１／２に希釈したガスをテフロン（登録商標）チューブにより別の原料管に吹き込んで３０分ガス置換した後、室温（２３℃）下で防止剤（１）を供給して重量比１/２に希釈し、さらに４−ヒドロキシ−２
，２，６，６−テトラメチルピペリジン−１−オキシルを１５００重量ｐｐｍ添加・溶解した(以下「防止剤（２）」と称する場合がある。)。防止剤（２）の溶存酸素の飽和率は１０％だった。尚４−ヒドロキシ−２，２，６，６−テトラメチルピペリジン−１−オキシルは純度９９．７ｗｔ％である。防止剤（２）を調製して２３℃で６時間保持した後、原料（１）を２７０ｍＬ／時の供給速度で原料供給管を介して充填塔へ供給すると共に、防止剤（２）を３０ｍｌ／時の供給速度で原料供給管流路内において原料（１）と合流させて充填塔へ供給し、蒸留実験を開始した。また、トルエンは共沸剤として用い、塔頂で全還流させながら蒸留を行った。操作条件は、フラスコ内温度＝９０℃、塔頂温度＝５０℃、塔頂圧力＝１６０Ｔｏｒｒで行った。定常状態で塔底部よりサンプリングした塔底液の組成は、アクリル酸＝８３重量％、酢酸＝３重量％、トルエン＝１４重量％であった。６時間の蒸留実験を継続したが塔内にはポリマーは全く確認されなかった。
Toluene was charged into another raw material pipe, and the gas diluted with nitrogen gas to a volume ratio of 1/2 was blown into the other raw material pipe with a Teflon (registered trademark) tube and replaced with gas for 30 minutes, and then room temperature (23 ° C.) The inhibitor (1) is supplied below to dilute to a weight ratio of 1/2, and 4-hydroxy-2
1,2,6,6-tetramethylpiperidine-1-oxyl was added and dissolved at 1500 ppm by weight (hereinafter sometimes referred to as “inhibitor (2)”). The saturation rate of dissolved oxygen in the inhibitor (2) was 10%. 4-Hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl has a purity of 99.7 wt%. After preparing the inhibitor (2) and holding at 23 ° C. for 6 hours, the raw material (1) is supplied to the packed tower through the raw material supply pipe at a supply rate of 270 mL / hour, and 30 ml of the inhibitor (2) is supplied. The raw material (1) was merged in the raw material supply pipe flow path at a supply speed of / hour and supplied to the packed tower to start a distillation experiment. Further, toluene was used as an azeotropic agent, and distillation was performed while fully refluxing at the top of the column. The operating conditions were as follows: flask temperature = 90 ° C., column top temperature = 50 ° C., column top pressure = 160 Torr. The composition of the bottom liquid sampled from the bottom of the tower in a steady state was acrylic acid = 83 wt%, acetic acid = 3% wt, and toluene = 14 wt%. Although the distillation experiment for 6 hours was continued, no polymer was confirmed in the column.
（実施例２）
防止剤（１）及び防止剤（２）に吹き込む気体として、空気を窒素ガスで体積比１/１
０に希釈したガスとした以外は実施例１と同様に実験を行った。防止剤（２）の溶存酸素の飽和率は１％だった。その結果、６時間の運転時間において塔内でポリマーは全く確認されなかった。
(Example 2)
As a gas blown into the inhibitor (1) and the inhibitor (2), air is nitrogen gas and the volume ratio is 1/1.
The experiment was conducted in the same manner as in Example 1 except that the gas diluted to 0 was used. The saturation rate of dissolved oxygen in the inhibitor (2) was 1%. As a result, no polymer was observed in the tower at the operation time of 6 hours.
（実施例３）
防止剤（１）及び防止液（２）の調合時の温度を４０℃とし、防止液（２）の保持する温度を４０℃としたこと以外は実施例１と同様に実験を行った。その結果、６時間の運転時間において塔内でポリマーは全く確認されなかった。
Example 3
The experiment was performed in the same manner as in Example 1 except that the temperature at the preparation of the inhibitor (1) and the inhibitor liquid (2) was 40 ° C., and the temperature retained by the inhibitor liquid (2) was 40 ° C. As a result, no polymer was observed in the tower at the operation time of 6 hours.
（比較例１）
原料管にトルエンを仕込み、空気を窒素ガスで体積比１／２に希釈したガスをテフロン（登録商標）チューブにより原料管に吹き込んで３０分ガス置換した後、室温（２３℃）下でフェノチアジンを３０００重量ｐｐｍ加え溶解し防止剤（３）とした。
(Comparative Example 1)
Toluene was charged into the raw material tube, and the gas diluted with nitrogen gas to 1/2 the volume ratio was blown into the raw material tube with a Teflon (registered trademark) tube and replaced with gas for 30 minutes. It was dissolved by adding 3000 ppm by weight to obtain an inhibitor (3).
別の原料管にトルエンを仕込み、空気を窒素ガスで体積比１／２に希釈したガスをテフロン（登録商標）チューブにより別の原料管に吹き込んで３０分ガス置換した後、室温（２３℃）下で４−ヒドロキシ−２，２，６，６−テトラメチルピペリジン−１−オキシルを３０００重量ｐｐｍ添加・溶解させたものを防止剤（４）とした。蒸留試験開始時、これら防止剤（３），防止剤（４）を１５ｍｌ／時ずつ別々に原料供給管より供給して原料（１）と流路内で合流させ、供給した以外は実施例１と同様に実験を行った。その結果、６時間の運転終了時塔内で目立った重合物の生成は確認されなかったが、その後の解体洗浄時に充填物同士の固着が確認された。 Toluene was charged into another raw material pipe, and the gas diluted with nitrogen gas to a volume ratio of 1/2 was blown into the other raw material pipe with a Teflon (registered trademark) tube and replaced with gas for 30 minutes, and then room temperature (23 ° C.) The inhibitor (4) was prepared by adding and dissolving 3000 ppm by weight of 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl. Example 1 except that at the start of the distillation test, these inhibitor (3) and inhibitor (4) were supplied separately from the raw material supply pipe at 15 ml / hour, merged with the raw material (1) in the flow path, and supplied. The experiment was conducted in the same manner as above. As a result, the formation of a conspicuous polymer in the tower was not confirmed at the end of the 6-hour operation, but sticking between the packings was confirmed during the subsequent disassembly cleaning.
（比較例２）
防止剤（２）を調製して０．５時間保持した後に蒸留試験を開始して、原料（１）、防止剤（２）を原料供給管を介して充填塔に供給したこと以外は実施例１と同様に実験を行った。その結果、６時間の運転終了時塔内で目立った重合物の生成は確認されなかったが、その後の解体洗浄時に充填物同士の固着が確認された。
(Comparative Example 2)
Example 1 The distillation test was started after the inhibitor (2) was prepared and held for 0.5 hour, and the raw materials (1) and (2) were supplied to the packed tower via the raw material supply pipe. The experiment was conducted in the same manner as in 1. As a result, the formation of a conspicuous polymer in the tower was not confirmed at the end of the 6-hour operation, but sticking between the packings was confirmed during the subsequent disassembly cleaning.
（比較例３）
防止剤（２）を調製して７２時間保持した後に蒸留試験を開始して、原料（１）、防止剤（２）を原料供給管を介して充填塔に供給したこと以外は実施例１と同様に実験を行った。その結果、６時間の運転終了時塔内に白い塊状の重合物が確認され、充填物が固着していた。
(Comparative Example 3)
The distillation test was started after preparing the inhibitor (2) and maintained for 72 hours, and Example 1 except that the raw material (1) and the inhibitor (2) were supplied to the packed tower via the raw material supply pipe. The experiment was conducted in the same manner. As a result, a white lump polymer was confirmed in the tower at the end of 6 hours of operation, and the packing was fixed.
（比較例４）
防止剤（１）及び防止剤（２）に吹き込む気体を窒素ガスとしたこと以外は実施例１と同様に実験を行った。防止剤（２）の溶存酸素の飽和率は０％だった。その結果、６時間の運転終了時塔内に白い塊状の重合物が確認され、充填物が固着していた。また、フラスコ内の液も重合物の発生により白く濁っていた。
(Comparative Example 4)
The experiment was performed in the same manner as in Example 1 except that the gas blown into the inhibitor (1) and the inhibitor (2) was nitrogen gas. The saturation rate of dissolved oxygen in the inhibitor (2) was 0%. As a result, a white lump polymer was confirmed in the tower at the end of 6 hours of operation, and the packing was fixed. The liquid in the flask was also cloudy white due to the generation of polymer.
（比較例５）
防止剤（１）及び防止剤（２）に吹き込む気体を純酸素としたこと以外は実施例１と同様に実験を行った。防止剤（２）の溶存酸素の飽和率は１００％だった。その結果、６時間の運転終了時塔内に白い塊状の重合物が確認され、充填物が固着していた。
(Comparative Example 5)
The experiment was performed in the same manner as in Example 1 except that the gas blown into the inhibitor (1) and the inhibitor (2) was pure oxygen. The saturation rate of dissolved oxygen in the inhibitor (2) was 100%. As a result, a white lump polymer was confirmed in the tower at the end of 6 hours of operation, and the packing was fixed.
（比較例６）
原料管にトルエンを仕込み、空気を窒素ガスで体積比１／２に希釈したガスをテフロン（登録商標）チューブにより原料管に吹き込んで３０分ガス置換した後、室温（２３℃）下でフェノチアジンを３０００重量ｐｐｍ加え溶解させたものを防止剤（５）とし、防止剤（５）のみを３０ｍｌ／時で原料供給管より供給して原料（１）と流路内で合流させ、充填塔に供給した以外は実施例１と同様に実験を行った。その結果、６時間の運転終了時塔内に白い塊状の重合物が確認され、充填物が固着していた。
(Comparative Example 6)
Toluene was charged into the raw material tube, and the gas diluted with nitrogen gas to 1/2 the volume ratio was blown into the raw material tube with a Teflon (registered trademark) tube and replaced with gas for 30 minutes. Dissolved by adding 3000 ppm by weight to make the inhibitor (5), only the inhibitor (5) is supplied from the raw material supply pipe at 30 ml / hour, merged with the raw material (1) in the flow path, and supplied to the packed tower The experiment was performed in the same manner as in Example 1 except that. As a result, a white lump polymer was confirmed in the tower at the end of 6 hours of operation, and the packing was fixed.
（比較例７）
原料管にトルエンを仕込み、空気を窒素ガスで体積比１／２に希釈したガスをテフロン（登録商標）チューブにより原料管に吹き込んで３０分ガス置換した後、室温（２３℃）下で４−ヒドロキシ−２，２，６，６−テトラメチルピペリジン−１−オキシルを３０００重量ｐｐｍ加え溶解させたものを防止剤（６）とし、防止剤（６）のみを３０ｍｌ／時で原料供給管より供給して原料（１）と流路内で合流させ、充填塔に供給した以外は実施例１と同様に実験を行った。その結果、６時間の運転終了時塔内に白い塊状の重合物が確認され、充填物が固着していた。
(Comparative Example 7)
Toluene was charged into the raw material pipe, and a gas diluted with air to a volume ratio of 1/2 with nitrogen gas was blown into the raw material pipe with a Teflon (registered trademark) tube to replace the gas for 30 minutes, and then at room temperature (23 ° C.), 4- Dissolved by adding 3000 ppm by weight of hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl as an inhibitor (6), and only the inhibitor (6) was supplied from the raw material supply pipe at 30 ml / hour Then, the experiment was conducted in the same manner as in Example 1 except that the raw material (1) was merged in the flow path and supplied to the packed tower. As a result, a white lump polymer was confirmed in the tower at the end of 6 hours of operation, and the packing was fixed.
本発明の重合防止方法はアクリル酸の蒸留条件のようなアクリル酸が重合しやすい過酷な条件下においても、重合防止性能を長時間安定して発現させているのであるから、アクリル酸及び／又はそのエステルを工業的に長期間安定的に製造する製造プラントに適用する方法として有用である。 Since the polymerization preventing method of the present invention stably exhibits the polymerization preventing performance for a long time even under severe conditions where acrylic acid is easily polymerized, such as distillation conditions of acrylic acid, acrylic acid and / or The ester is useful as a method applied to a production plant for industrially producing the ester stably for a long period of time.
Claims (5)
下記一般式（１）で表されるＮ−オキシル化合物と、アミン化合物、フェノール化合物及び銅塩化合物からなる群より選ばれた少なくとも１種の化合物とを溶媒に溶解し、溶存酸素の飽和率が０．１％〜２０％である重合防止剤溶液を調製し、
調製した該重合防止剤溶液を２時間〜３０時間の範囲内で保持した後に、アクリル酸及び／又はそのエステルを含有する溶液に添加する重合防止方法。
An N-oxyl compound represented by the following general formula (1) and at least one compound selected from the group consisting of an amine compound, a phenol compound and a copper salt compound are dissolved in a solvent, and the saturation rate of dissolved oxygen is Preparing a polymerization inhibitor solution of 0.1% to 20%,
A polymerization prevention method comprising adding the prepared polymerization inhibitor solution to a solution containing acrylic acid and / or an ester thereof after holding the solution within a range of 2 hours to 30 hours.
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