JP2008303200A - Method for distilling readily polymerizable compound-containing liquid - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a batch-type simple distillation method for a liquid containing a readily polymerizable compound such as (meth)acrylic acid, while preventing a polymerization inside the distillation apparatus and reducing the amount of liquid residues to be discarded as waste oil. <P>SOLUTION: The batch-type simple distillation method for a liquid containing a readily polymerizable compound such as (meth)acrylic acid is provided, comprising the following process: at a point when the amount of distillate comes to 70 mass% or more of that of a liquid initially charged into the distillation apparatus, a distillation residue liquid is introduced into a simple distillation-type distillation unit 1, and a distillation operation is continued. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

The present invention relates to a distillation method for an easily polymerizable compound-containing liquid. Specifically, it relates to a method of distilling a liquid containing an easily polymerizable compound such as (meth) acrylic acid or (meth) acrylic acid ester, and more specifically, like (meth) acrylic acid or (meth) acrylic acid ester. When a readily polymerizable compound-containing liquid is batch-distilled, the distillation residue can be recycled by distilling a part of the liquid into the distillation apparatus without discarding the distillation residue remaining in the distillation apparatus after the distillation. The present invention relates to a distillation method that effectively utilizes a polymerization inhibitor contained in a liquid.

Distilling and purifying easily polymerizable compounds such as (meth) acrylic acid and (meth) acrylic acid esters are industrially widespread, depending on the production volume, continuous distillation or batch type Distillation is selected.

As a specific example of continuous distillation, for example, in Patent Document 1, in a continuous process of (meth) acrylic acid ester, a polymerization inhibitor contained in a bottom of a distillation column is reused and A technique for recovering residual (meth) acrylic acid esters is disclosed.

Patent Document 2 uses a distillation apparatus having an empty portion and a thin-film distillation apparatus in a continuous purification process of hydroxyalkyl (meth) acrylate obtained by reacting (meth) acrylic acid and alkylene oxide. And a technique for purification.

As shown in these patent documents, in the continuous distillation process, a polymerization prevention method and a technique for obtaining a product with high purity are presented.

On the other hand, in the case of batch distillation, since the amount of liquid held in the distillation apparatus decreases with the lapse of the distillation time, the temperature in the distillation apparatus rises due to the concentration of high-boiling substances, and polymerization occurs in the distillation apparatus such as in a reboiler tube. There is a risk that things will be generated. Furthermore, there is a risk that the circulating pump may cause cavitation due to a decrease in the amount of liquid retained. Although these various problems can be solved by taking measures to reduce the distillate ratio, in that case, a new problem arises in that the amount discarded as waste oil increases and loss increases. Further, in order to improve the yield by increasing the proportion of distillation, it is necessary to arrange packings and trays in the distillation apparatus and bring them into gas-liquid contact to increase the distillation efficiency. However, in that case, it is necessary to introduce a complicated polymerization prevention system in order to suppress the generation of a polymer in the distillation apparatus, which is economically disadvantageous.

JP 2001-181233 A Japanese Patent No. 3592970

Therefore, the object of the present invention is to perform simple polymerization in order to prevent polymerization inside the distillation apparatus when batch-distilling liquids containing easily polymerizable compounds such as (meth) acrylic acid and (meth) acrylic acid esters. An object of the present invention is to provide a batch-type simple distillation method for easily polymerizable compound-containing liquids, which selects a simple distillation format that enables a prevention system and reduces the amount of distillation residue liquid discarded as waste oil.

In order to solve the above-mentioned problems, the present inventors have intensively studied. As a result, a specific amount of the distillation residue liquid discharged after the batch-type simple distillation of the easily polymerizable compound-containing liquid is recycled into the distillation apparatus from the specific time during the next batch-type simple distillation. Thus, it was found that polymerization in the distillation apparatus can be prevented, and the present invention was completed.

That is, in the present invention, when the easily polymerizable compound-containing liquid is simply distilled using a batch type simple distillation type distillation apparatus, when at least 70% by mass of the initially charged raw material is distilled, the previous batch type simple distillation is performed. Distillation residue liquid obtained by distilling off the easily polymerizable compound obtained by distillation is supplied to the batch type simple distillation type distillation apparatus, and the simple distillation is continued. It is a distillation method of the containing liquid.

According to the distillation method of the present invention, a purified easily polymerizable compound can be obtained with a simple polymerization prevention system using an existing batch type simple distillation apparatus. For example, in the simple distillation according to the conventional method in which the distillation residue liquid is not recycled, a polymer is generated in the distillation apparatus in a relatively short period of time, whereas according to the distillation method of the present invention, the distillation residue liquid is placed in the distillation apparatus. It can be operated stably for a long time by recycling. However, simply recycling the distillation residue liquid into the distillation apparatus will affect the product purity of the resulting easily polymerizable compound, so that a specific amount is recycled into the distillation apparatus from the specific time point disclosed by the present invention. There is a need.

According to the distillation method of the present invention, the amount of distillation residue liquid discarded as waste oil can be reduced, and further, polymerization in the distillation apparatus can be suppressed without requiring a special polymerization prevention system.

Hereinafter, although the distillation method of the easily polymerizable compound-containing liquid according to the embodiment of the present invention will be described in detail, the scope of the present invention is not limited to these descriptions, and the gist of the present invention other than the following examples Can be appropriately changed and implemented within a range not impairing the above. In the present specification, “X to Y” indicating a range indicates X or more and Y or less.

In the distillation method of the easily polymerizable compound-containing liquid according to the embodiment of the present invention, when at least 70% by mass of the initially charged raw material is distilled, the distillation residue liquid is supplied into a batch type simple distillation type distillation apparatus. And continue the distillation.

The said distillation residue liquid means the liquid which remains in a distillation apparatus after batch type simple distillation is complete | finished. After the distillation residue liquid is transferred to a waste oil storage tank, a part thereof is supplied (recycled) to the next batch type simple distillation, and the remaining part is discharged out of the system as waste oil. Furthermore, the distillation residue liquid after the completion of the next batch type simple distillation is transferred to the same waste oil storage tank, a part of which is supplied (recycled) to the next batch type simple distillation, and the remaining part is used as waste oil outside the system. To be released. Thereafter, this operation is repeated.

The easily polymerizable compound to which the distillation method according to the embodiment of the present invention can be applied is usually a liquid that contains impurities and is easily polymerized when a distillation step is performed to remove such impurities. For example, acrylic acid, methacrylic acid, maleic anhydride, acrylonitrile, or an ester or derivative thereof may be mentioned. Examples of the acrylate ester include methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, and the like. , Methyl methacrylate, butyl methacrylate, t-butyl methacrylate, isobutyl methacrylate, cyclohexyl methacrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, and the like.

Further, the easily polymerizable compound-containing liquid may further be a mixture containing a high-boiling substance, a solvent, and a by-product at the time of generating the easily polymerizable substance.

The easily polymerizable compound is acrylic acid, methacrylic acid or an ester thereof, and examples of the easily polymerizable compound-containing liquid include those containing a solvent and other impurities. As such impurities, when the easily polymerizable compound is acrylic acid and acrylic acid ester, acetic acid, propionic acid, acrolein, maleic acid, water, by-product when acrylic acid is obtained by catalytic gas phase oxidation reaction, Formalin can be mentioned. In the case where the easily polymerizable compound is methacrylic acid or a methacrylic acid ester, methacrolein, acrylic acid, acetic acid, etc. which are by-produced when methacrylic acid is obtained by a catalytic gas phase oxidation reaction can be mentioned as impurities. Moreover, the impurity produced | generated by the esterification process of acrylic acid and methacrylic acid, and the impurity produced | generated by the refinement | purification process of acrylic acid, methacrylic acid, or these ester bodies can be mentioned.

In the distillation method according to the embodiment of the present invention, in order to prevent polymerization of a polymerizable substance such as (meth) acrylic acid, it is generally known as a polymerization inhibitor for easily polymerizable compounds such as (meth) acrylic acid. Compounds may be added.

Examples of such polymerization inhibitors include phenol compounds, amine compounds, copper salt compounds, manganese salt compounds, N-oxyl compounds, N-hydroxy-2,2,6,6-tetramethylpiperidine compounds. 2,2,6,6-tetramethylpiperidine compounds, nitroso compounds, and their decomposition products. These polymerization inhibitors may be used alone or in combination of two or more.

Although it does not specifically limit as said phenolic compounds, For example, hydroquinone, methyl hydroquinone, tert-butyl hydroquinone, 2,6-di-tert-butyl hydroquinone, 2,5-di-tert-butyl hydroquinone, 2,4- Examples thereof include dimethyl-6-tert-butylphenol and p-methoxyphenol. Among these, p-methoxyphenol is preferable because it has a better polymerization preventing effect than hydroquinone when used in combination with N-oxyl compounds and amine compounds. Two or more of these phenol compounds may be used in combination.

The amine compounds are not particularly limited, and examples thereof include phenothiazine, bis- (1-methylbenzene) phenothiazine, 3,7-dioctylphenothiazine, bis- (1-dimethylbenzyl) phenothiazine, thiodiphenylamine and the like. it can.

The copper salt compounds are not particularly limited, and any of inorganic salts and organic salts may be used. Examples thereof include copper dialkyldithiocarbamate, copper acetate, copper naphthenate, copper acrylate, copper sulfate, copper nitrate, copper chloride and the like. These copper salt compounds can be either monovalent or divalent. Among the copper salt compounds, copper dialkyldithiocarbamate is preferred from the standpoint of effects.

The copper dialkyldithiocarbamate is not particularly limited, for example, copper dimethyldithiocarbamate, copper diethyldithiocarbamate, copper dipropyldithiocarbamate, copper dibutyldithiocarbamate, copper dipentyldithiocarbamate, copper dihexyldithiocarbamate, copper diphenyldithiocarbamate, Copper methylethyldithiocarbamate, copper methylpropyldithiocarbamate, copper methylbutyldithiocarbamate, copper methylpentyldithiocarbamate, copper methylhexyldithiocarbamate, copper methylphenyldithiocarbamate, copper ethylpropyldithiocarbamate, copper ethylbutyldithiocarbamate, ethylpentyl Copper dithiocarbamate, copper ethylhexyl dithiocarbamate, ethylphenyldithiocarbamate Copper nitrate, propylbutyl thiocarbamate, propylpentyldithiocarbamate, propylhexyldithiocarbamate, propylphenyldithiocarbamate, butylpentyldithiocarbamate, butylhexyldithiocarbamate, butylphenyldithiocarbamate, pentylhexyl Examples include copper dithiocarbamate, copper pentylphenyldithiocarbamate, copper hexylphenyldithiocarbamate, and the like. These copper dialkyldithiocarbamates may be monovalent copper salts or divalent copper salts. Of these, copper dimethyldithiocarbamate, copper diethyldithiocarbamate and copper dibutyldithiocarbamate are preferred, and copper dibutyldithiocarbamate is particularly preferred from the standpoints of effects and availability.

The manganese salt compounds are not particularly limited. For example, manganese dialkyldithiocarbamate (the alkyl group may be methyl, ethyl, propyl, or butyl, which may be the same or different), manganese diphenyldithiocarbamate , Manganese formate, manganese acetate, manganese octoate, manganese naphthenate, manganese salts of ethylenediaminetetraacetic acid, and the like, and one or more of these can be used.

The N-oxyl compounds are not particularly limited, and any N-oxyl compounds that are generally known as polymerization inhibitors for vinyl compounds can be used. Among these, 2,2,6,6-tetramethylpiperidinooxyls represented by the following formula (1):

(Wherein R ¹ represents CHOH, CHCH ₂ OH, CHCH ₂ CH ₂ OH, CHOCH ₂ OH, CHOCH ₂ CH ₂ OH, CHCOOH, or C═O, and R ² represents H or CH ₂ OH. ) Is preferably used. Any N-oxyl compound can be used without particular limitation, but 2,2,6,6-tetramethylpiperidinooxyl, 4-hydroxy-2,2, which can give a good polymerization preventing effect. 6,6-tetramethylpiperidinooxyl, 4,4′-bis- (2,2,6,6-tetramethylpiperidinooxyl) sebacate, 4,4 ′, 4 ″ -tris- (2, It is preferable to use one or more of 2,6,6-tetramethylpiperidinooxyl) phosphite.

Representative examples of N-hydroxy-2,2,6,6-tetramethylpiperidine compounds include 1,4-dihydroxy-2,2,6,6-tetramethylpiperidine, 1-hydroxy-2,2,6 , 6-tetramethylpiperidine and the like. These N-hydroxy-2,2,6,6-tetramethylpiperidine compounds can be used alone or in admixture of two or more.

Specific examples of 2,2,6,6-tetramethylpiperidine compounds include 2,2,6,6-tetramethylpiperidine, 4-hydroxy-2,2,6,6-tetramethylpiperidine and the like. One or more of these can be used. N-hydroxy-2,2,6,6-tetramethylpiperidine compounds and 2,2,6,6-tetramethylpiperidine compounds are contained as impurities in commercially available N-oxyl compound products. In such a case, by using a commercially available N-oxyl compound, N-hydroxy-2,2,6,6-tetramethylpiperidine compound or 2,2,6,6-tetramethyl may be used together. The piperidine compound was used in combination.

The nitroso compounds are not particularly limited, and examples thereof include p-nitrosophenol, nitrosobenzene, N-nitrosodiphenylamine, isononyl nitrite, N-nitrosocyclohexylhydroxylamine, N-nitrosophenylhydroxylamine and ammonium salts thereof. One or more of these can be used.

When using the polymerization inhibitor, the amount added is appropriately adjusted according to the operating conditions and the like, and is not particularly limited, but is 0.0001 to 1% by mass relative to the initial charge per batch. Preferably, it is 0.001 to 0.5% by mass.

The method for adding the polymerization inhibitor is not particularly limited, and when the polymerization inhibitor is solid, it is preferably added in a solid (powder) or a state dissolved in a liquid (mother liquor). Gas can also be introduced. When the polymerization inhibitor is a liquid, it is preferably added as it is or dissolved in a liquid (mother liquor). When the polymerization inhibitor is a gas, it is preferably added in a gas state. .

Further, the addition timing of the polymerization inhibitor is not particularly limited, and can be added at any time during the distillation process. However, when the polymerization inhibitor is solid, the distillation apparatus is initially introduced together with the components to be initially charged. It is better to add it inside.

In the distillation method according to the embodiment of the present invention, molecular oxygen can be used in combination with the above-described polymerization inhibitor as necessary.

In the distillation method according to the embodiment of the present invention, an acid can be used in combination with the above polymerization inhibitor in order to enhance the polymerization prevention effect. Examples of acids include, but are not limited to, for example, oxalic acid, oxalic anhydride, malonic acid, succinic acid, succinic anhydride, fumaric acid, maleic acid, maleic anhydride, octanoic acid, adipic acid, sebacic acid, tetradecanedicarboxylic acid 1,2,4-butanetricarboxylic acid, 1,3,6-hexatricarboxylic acid, 1,2,3,4-butanetetracarboxylic acid, 1,2,3,4-pentanetetracarboxylic acid, 1,6 , 7,12-dodecanetetracarboxylic acid, benzoic acid, orthotoluic acid, metatoluic acid, p-toluic acid, phthalic acid, phthalic anhydride, isophthalic acid, terephthalic acid, 2,6-naphthalenedicarboxylic acid, pyromellitic acid, pyromellitic anhydride Acid, 1,2,4-benzenetricarboxylic acid, 1,4,5,8-naphthalenetetracarboxylic acid, 1,3,5, - naphthalene tetracarboxylic acid, salicylic acid, carboxylic acids and carboxylic acid anhydrides such as acetic acid. These may be used alone or in combination of two or more.

When the above acids are used, the amount added is appropriately adjusted according to the type of polymerization inhibitor used, the amount added, etc., and is not particularly limited, but the total amount of acids added to the initial charge per batch Is preferably 0.0001 to 1% by mass, more preferably 0.001 to 0.5% by mass. When the amount is less than 0.0001% by mass, a sufficient polymerization preventing effect cannot be obtained, which is not preferable. Moreover, when more than 1 mass% or more, the property deterioration of a distillation residue liquid will occur easily and it is unpreferable.

Further, the method for adding the acids is not particularly limited, and may be added (added) in a lump or divided into two or more.

The distillation according to the embodiment of the present invention is performed under vacuum, and the degree of vacuum is preferably, for example, 0.66 hPa to 1000 hPa, and preferably 1.33 hPa to 666 hPa. If it is less than 0.66 hPa, it is not preferable in that it is difficult to condense and recover the vapor of the easily polymerizable compound, and if it is more than 1000 hPa, the operation temperature becomes high and polymerization occurs in the distillation apparatus. It is not preferable.

A distillation method according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a system diagram showing the distillation method of the present invention. However, the present invention is not limited to this, and can be appropriately modified and implemented without departing from the spirit of the present invention.

In FIG. 1, an easily polymerizable compound-containing liquid, for example, a crude liquid containing (meth) acrylic acid or (meth) acrylic acid ester (hereinafter, this easily polymerizable compound-containing liquid may be referred to as an “initial charge liquid”. ) Is charged into a batch-type simple distillation apparatus (hereinafter sometimes simply referred to as “distillation apparatus”) 1 from the line 9, and the single-distillation of the easily polymerizable compound-containing liquid is performed batchwise here. At the bottom of the distillation apparatus 1, a pump 5 for extracting and circulating the liquid in the distillation apparatus and a reboiler 4 as a heating source are connected via a circulation line 6, and a heat medium such as steam is introduced into the reboiler 4. The charged solution is heated and distilled.

The distilled distillate is sent to the product storage tank 2 via the distillation line 8. When batch-type simple distillation is completed, a distillation residue liquid (hereinafter sometimes referred to as “distillation bottom liquid”) remaining in the distillation apparatus is passed through a circulation line 6 and a distillation bottom liquid feed line 10 to be a waste oil storage tank 3. And store it here. Although not shown in FIG. 1, the waste oil storage tank 3 is provided with a cooling device so that even if a distillation bottom liquid having a high temperature after the distillation is mixed, it is immediately cooled and stored at a low temperature. It has become.

In the distillation method according to the embodiment of the present invention, first, the easily polymerizable compound-containing liquid is charged into the distillation apparatus 1, where the initial charge liquid is distilled batchwise, and the distillate is stored in the product storage tank 2. In addition, the distillation bottom liquid after completion of distillation is sent to the waste oil storage tank 3 and then cooled and stored in the waste oil storage tank 3. Here, let V be the initial charge amount before the start of distillation.

Next, a new charge liquid is charged into the distillation apparatus 1 and batch-type simple distillation is started. At that time, when the liquid amount of the distillate becomes 0.7 × V or more, at least a part of the distillation bottom liquid in the waste oil storage tank 3 passes through the waste oil supply pump 11 and the waste oil recycle line 7 to the distillation apparatus 1. And continue the distillation. Here, in FIG. 1, the supply is made from the suction side of the circulation pump 5, but the supply is not limited to this, and the supply may be directly made to the distillation apparatus 1. After the distillation, the distillation bottom liquid is sent to the waste oil storage tank 3 and then mixed with the liquid stored in the waste oil storage tank 3, and then cooled and stored.

Thereafter, the above operation is repeated.

In the batch type simple distillation according to the embodiment of the present invention, the supply of the distillation bottom liquid is preferably started from the time when the liquid amount of the distillate becomes 0.7 × V to 0.95 × V. 75 * V-0.9 * V is more preferable. Start of supply at a stage earlier than 0.7 × V is not preferable because the purity of the purified easily polymerizable compound obtained is lowered. In addition, when the supply is started at a stage slower than 0.95 × V, the amount of liquid held in the distillation apparatus 1 is reduced and the liquid level is lower than that of the reboiler tube plate, so that a polymer is generated in the distillation apparatus 1. In addition to the fear, there is a risk that the circulation pump 5 that circulates the distilled bottom liquid may cause cavitation.

In the batch type simple distillation according to the embodiment of the present invention, the supply amount of the distillation bottom liquid is preferably 3% by mass to 20% by mass of the initial charge liquid, and more preferably 5% by mass to 15% by mass. When the amount is less than 3% by mass, the polymerization inhibitor brought in from the distillation bottom liquid is small, and a sufficient polymerization preventing effect cannot be obtained. On the other hand, an amount of more than 20% by mass is not preferable because the purity of the purified easily polymerizable compound obtained is lowered. The supply of the distillation bottom liquid according to the embodiment of the present invention only needs to be able to put the distillation bottom liquid into the distillation apparatus,
Although it does not specifically limit, For example, the liquid feeding pump and pressure feeding normally used can be used. The supply of the distillation bottom liquid may be either continuous charging or intermittent charging, and is not particularly limited. Note that the continuous charging means a mode in which charging is performed continuously little by little, and the intermittent charging means a mode in which charging is performed in an arbitrary number of times in a pulsed manner or intermittently.

The waste oil storage tank 3 according to the embodiment of the present invention is not particularly limited as long as it can store the distillation bottom liquid, and its shape and the like are not particularly limited. In order to suppress deterioration of the polymerization inhibitor contained in the distillation bottom liquid, the distillation bottom liquid is used. It is preferable to provide a cooling device for cooling. The cooling method is not particularly limited, and a generally performed method can be employed. As the cooling temperature, it is preferable to cool to 50 ° C. or less within a range of 0.5 hour or more and 1.0 hour or less starting from the time when the transfer of the distillation bottom liquid is completed, and more preferably 35 ° C. or less, 20 A temperature of not higher than ° C is particularly preferred. Moreover, it is preferable to store at the same temperature as the temperature after cooling. A cooling temperature of 50 ° C. or higher is not preferable because the polymerization inhibitor contained in the waste oil is altered and the polymerization prevention effect is lost.

The reboiler 4 according to the embodiment of the present invention is not particularly limited as long as the charged liquid can be efficiently heated. For example, a forced circulation multitubular reboiler, a natural circulation multitubular reboiler, or the like can be used. In addition to the reboiler, a coil, a jacket, or the like can be used as the heating source.

The present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of the claims. That is, embodiments obtained by combining technical means appropriately changed within the scope of the claims are also included in the technical scope of the present invention.

EXAMPLES Hereinafter, although a production example, an Example, and a comparative example demonstrate this invention further in detail, this invention is not limited to these Examples. (Manufacturing example) The internal pressure of the SUS316 distillation apparatus (single distillation type. A multi-tube reboiler was installed as a heating source and forcedly circulated using a circulation pump) was evacuated to 5.33 hPa. Thereafter, 1150 kg of a hydroxyethyl methacrylate (hereinafter referred to as “HEMA”)-containing liquid obtained by reacting methacrylic acid and ethylene oxide, 0.12 kg of p-methoxyphenol and 0.20 kg of phenothiazine as a polymerization inhibitor. The distillation of the HEMA-containing liquid was started by charging the reboiler with steam. Distillation started when the liquid temperature reached 70 ° C., and then became constant at 85 ° C. When the distillate amount reached 980 kg (85.2% by mass of the initially charged liquid), the distillation was terminated to obtain a distilled bottom liquid of 170 kg. Thereafter, the entire amount of the obtained distillation bottom liquid was transferred to a waste oil storage tank and cooled until the liquid temperature reached 48 ° C. In addition, although the temperature in a waste oil storage tank immediately after the completion of liquid feeding of the distillation bottom liquid rose to 75 ° C., it reached 48 ° C. in 30 minutes. Example 1 (Initial Distillation) 1150 kg of HEMA-containing liquid obtained by reacting methacrylic acid and ethylene oxide in the same distillation apparatus as in the production example, and 0.12 kg of p-methoxyphenol and phenothiazine 0 as a polymerization inhibitor 20 kg was charged and distillation was started.

From the time when the amount of the distillate reached 810 kg (70.4% by mass of the initial charged solution), 62 kg (5.4% by mass of the initial charged solution) of the distillation bottom liquid obtained in the production example was supplied to the feed pump. Used to feed distillation apparatus and continued distillation. After 3.5 hours from the start of distillation, the amount of the distillate was 1100 kg (95.7% by mass of the initial charge), so distillation was stopped.

After completion of the distillation, 112 kg of the distillation bottom liquid remaining in the distillation apparatus was transferred to the same waste oil storage tank as in the production example, and cooled until the liquid temperature reached 18 ° C. In addition, although the waste oil storage tank temperature immediately after the completion of liquid feeding of the distillation bottom liquid rose to 70 ° C., it reached 18 ° C. in 40 minutes. Thereafter, 50 kg of the liquid retained in the waste oil storage tank was discharged out of the system as waste oil. (Second and subsequent distillations) In the same distillation apparatus as the first distillation, 1150 kg of HEMA-containing liquid and 0.12 kg of p-methoxyphenol and 0.20 kg of phenothiazine were charged as polymerization inhibitors, and distillation was started.

When the distillate becomes 810 kg (70.4% by mass of the initial charge), the distillation bottom liquid 62 kg (5.4% by mass of the initial charge) held in the waste oil storage tank Was fed to a distillation apparatus and distillation continued. After 3.5 hours from the start of distillation, the amount of the distillate was 1100 kg (95.7% by mass of the initial charge), so distillation was stopped.

After completion of distillation, 112 kg of the distillation bottom liquid remaining in the distillation apparatus was transferred to a waste oil storage tank and cooled until the liquid temperature reached 18 ° C. Thereafter, 50 kg of waste oil storage tank liquid was discharged out of the system as waste oil.

Thereafter, this operation was repeated, and a total of 150 batches were carried out. However, there was no generation of a polymer in the distillation apparatus, and the operation was stable.

Further, the purity of the product HEMA obtained at this time was 97.8% by mass. (Example 2) The same operation as in Example 1 was performed except that the distillation bottom liquid supplied from the middle of distillation was 210 kg (18.3 mass% of the initial charge liquid).

A total of 150 batches were carried out, but there was no generation of polymer in the distillation apparatus, and the operation was stable.

Moreover, the purity of the product HEMA obtained at this time was 97.3% by mass. (Example 3) The same operation as in Example 1 was performed except that the distillation bottom liquid was supplied at a time when the amount of the distillate became 1050 kg (91.3 mass% of the initial charge liquid).

A total of 150 batches were carried out, but there was no generation of polymer in the distillation apparatus, and the operation was stable.

Moreover, the purity of the product HEMA obtained at this time was 97.4% by mass. (Comparative example 1) The same operation as Example 1 was performed except not having supplied distillation bottom liquid.

When 30 batches had elapsed, polymerization was observed in the distillation apparatus, so distillation was stopped. (Comparative example 2) Operation similar to Example 1 was performed except having supplied the distillation bottom liquid simultaneously with the preparation time of the HEMA containing liquid.

Even after 150 batches, no generation of polymer was observed in the distillation apparatus, but the purity of the product HEMA obtained at this time was lowered to 95.4% by mass. (Comparative example 3) The same operation as Example 1 was performed except having started the supply of the distillation bottom liquid from the time of the amount of distillate becoming 690 kg (60.0 mass% of an initial preparation liquid).

Even after 150 batches, no generation of polymer was observed in the distillation apparatus, but the purity of the product HEMA obtained at this time was reduced to 95.8% by mass.

It is a systematic diagram which shows one aspect | mode of the distillation method of this invention.

Explanation of symbols

1: Batch type simple distillation device 2: Product storage tank 3: Waste oil storage tank 4: Reboiler 5: Circulation pump 6: Circulation line 7: Waste oil supply line 8: Distillation line 9: Liquid feed line containing easily polymerizable compound 10: Distillation bottom liquid transfer line 11: Waste oil supply pump

Claims (5)

When the easily polymerizable compound-containing liquid was simply distilled using a batch type simple distillation apparatus, when at least 70% by mass of the initially charged raw material was distilled, the batch type simple distillation was obtained by the previous batch simple distillation. A distillation method of a liquid containing an easily polymerizable compound, characterized in that the distillation residue liquid after distilling off the easily polymerizable compound is supplied to the batch type simple distillation apparatus and the simple distillation is continued. When 70% by mass or more and 95% by mass or less of the initially charged raw materials are distilled, the distillation residue obtained by distilling off the easily polymerizable compound obtained by the previous batch type simple distillation is the batch type simple distillation. The method for distilling an easily polymerizable compound-containing liquid according to claim 1, which is supplied to a distillation apparatus of the type. The distillation method of the easily polymerizable compound-containing liquid according to claim 1 or 2, wherein the distillation residue liquid is stored at a temperature of 50 ° C or lower. The easily polymerizable compound according to any one of claims 1 to 3, wherein the distillation residue liquid supplied to the batch type simple distillation type distillation apparatus is 3% by mass or more and 20% by mass or less with respect to the initial charged raw material. Distillation method of liquid containing. The distillation method of the easily polymerizable compound containing liquid in any one of Claims 1-4 whose said easily polymerizable compound is (meth) acrylic acid and / or (meth) acrylic acid ester.

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