WO2007074750A1 - Process for producing (meth)acrylic ester - Google Patents

Abstract

A process for (meth)acrylic ester production which comprises: an esterification step in which the dehydrating esterification of (meth)acrylic acid with an alcohol or the transesterification of a (meth)acrylic ester with an alcohol is conducted to obtain a reaction product containing a (meth)acrylic ester; a neutralization/water washing step in which the reaction product is subjected to liquid-liquid separation with a detergent to separate the product into an organic layer containing the (meth)acrylic ester and an aqueous layer containing a water-soluble ingredient; a product purification step in which the (meth)acrylic ester is taken out of the organic layer; a wastewater storage step in which the aqueous layer is stored as wastewater in a wastewater storage tank; and a wastewater treatment step in which the wastewater contained in the wastewater storage tank is subjected to a wastewater treatment. In the process for producing a (meth)acrylic ester, the wastewater contained in the wastewater storage tank is kept having a polymerization inhibitor concentration of 0.005 mass% or higher.

Description

 Specification

 Method for producing (meth) acrylic acid ester

 Technical field

 The present invention relates to a method for producing acrylic acid or methacrylic acid (hereinafter referred to as (meth) acrylic acid) ester having a wastewater treatment step.

 Background art

 In general, in addition to these raw materials, a strong acid catalyst and a polymerization inhibitor are used for the esterification reaction in which (meth) acrylic acid and alcohol are used as raw materials and a dehydration reaction is applied to these raw materials to produce esters. Further, an anti-coloring agent is added. In general, an excessive amount of (meth) acrylic acid is added to the amount of raw material alcohol for the purpose of reducing reaction time and improving selectivity.

[0003] In the process of producing (meth) acrylic acid ester by the transesterification method in which methyl (meth) acrylate is reacted with alcohol, generally, a catalyst such as lithium-based, magnesium-based or titanium-based is used during the reaction. Etc. are added.

 [0004] In these ester production methods, if the molecular weight of the produced ester is relatively large, it may be difficult to purify the produced ester by distillation. In such a case, after completion of the esterification reaction utilizing the dehydration reaction or after completion of the transesterification reaction, the resulting reaction mixture is subjected to a neutralization / water washing step.

 [0005] In the neutralization / water washing step, the reaction mixture is washed with a cleaning agent such as water, alkaline water (for example, caustic soda aqueous solution, caustic potassium aqueous solution, ammonia water), saturated saline, and the catalyst added during the reaction. Water-soluble compounds such as polymerization inhibitors and unreacted raw materials are extracted into the aqueous layer and removed.

[0006] The neutralization 'water washing step using these detergents is usually performed once or more. In the neutralization process, particularly in the neutralization process using alkaline water such as caustic soda as a cleaning agent, waste water containing catalyst and unreacted (meth) acrylic acid is generated. This wastewater often has a high COD and cannot be discharged directly into the environment. For this reason, wastewater biodegradation treatment and wastewater combustion treatment are performed to reduce COD in wastewater. More Various wastewater treatment such as recovery of valuable materials such as catalyst and (meth) acrylic acid contained in wastewater is performed.

 [0007] In order to smoothly perform the above wastewater treatment while appropriately dealing with fluctuations in production conditions, etc., it is preferable that the wastewater is stored once before the wastewater treatment. However, the wastewater contains high concentrations of (meth) acrylic acid and its salts, which often cause polymerization during storage.

 [0008] (Meth) acrylic acid esters and some by-products are also contained in the wastewater. As a result, the ease of these polymerizations in the wastewater varies depending on the type of (meth) acrylic ester to be produced. Regardless of which (meth) acrylic acid ester is produced, and when wastewater gelation occurs due to polymerization, the piping is blocked or the combustion furnace nozzle is blocked when wastewater is subjected to combustion treatment. Or wastewater treatment is hindered. As a result, it is difficult to stably produce (meth) acrylic acid itself.

 [0009] Note that there is Patent Document 1 as a document relating to a combustion furnace.

 Patent Document 1: JP 2002-233862 A (Claim 1)

 Disclosure of the invention

 Problems to be solved by the invention

[0010] As a result of various investigations to solve the above problems, the present inventors have added a polymerization inhibitor to wastewater generated in the neutralization / washing step in the production of (meth) acrylic acid ester. The inventors have found that these problems can be solved, and have completed the present invention.

Accordingly, an object of the present invention is to provide a method for producing a (meth) acrylic acid ester that can smoothly treat wastewater generated in the production of a (meth) acrylic acid ester. .

 Means for solving the problem

[0012] The present invention for achieving the above object is described below.

[1] Esters for obtaining reaction products containing (meth) acrylic acid ester by dehydration reaction between (meth) acrylic acid and alcohol or transesterification reaction between (meth) acrylic acid ester and alcohol And an organic layer containing (meth) acrylic acid ester by liquid-liquid separation of the reaction product obtained in the esterification reaction step using a detergent. A neutralization / water washing process that separates into an aqueous layer containing a water-soluble component, a product purification process that extracts an organic layer strength (meth) acrylate ester separated in the neutralization / water washing process, and a neutralization and water washing process. Production of (meth) acrylate ester having at least a storage step of storing the separated water layer as waste water in a waste water storage tank and a waste water treatment step of treating waste water in the waste water storage tank stored in the waste water storage process A polymerization inhibitor is added to the aqueous layer separated in the neutralization and water washing step, whereby the concentration of the polymerization inhibitor in wastewater stored in the wastewater storage tank is 0.005% by mass or more. A method for producing a (meth) acrylic acid ester, characterized by

 [2] The method for producing a (meth) acrylic acid ester according to [1], wherein the internal space of the wastewater storage tank is maintained in an oxygen-containing atmosphere.

 [0015] [3] The method for producing a (meth) acrylic acid ester according to [1], wherein the temperature of the wastewater in the wastewater storage tank is maintained at 0 to 50 ° C.

 [0016] [4] The wastewater treatment step involves directly treating the wastewater in the wastewater storage tank to treat the wastewater, or combusting the wastewater after recovering the wastewater power (meth) acrylic acid in the storage tank. The method for producing a (meth) acrylic acid ester according to [1], wherein the wastewater treatment is performed by

[5] The method for producing a (meth) acrylic acid ester according to [1], wherein the alcohol to be reacted by dehydration esterification reaction or transesterification reaction is a polyhydric alcohol.

[0018] [6] The method for producing a (meth) acrylic acid ester according to [1], wherein the polymerization inhibitor is an aromatic derivative or a quinone derivative having two or more hydroxyl groups.

[7] The pH of the aqueous layer is 7 to 14, the total concentration of alkali components is 0.1 to 50% by mass, and the total concentration of (meth) acrylic acid and its salt is ^ to 50% by mass. The method for producing a (meth) acrylic acid ester according to [1].

 The invention's effect

[0020] In the present invention, during the production of (meth) acrylic acid ester, it is polymerized into wastewater generated during the neutralization / washing process, particularly wastewater generated during the neutralization process using an alkali or the like. Since the inhibitor is added, it is possible to suppress clogging of the wastewater piping and gelation of the wastewater in the wastewater storage tank. As a result, wastewater treatment and (meth) acrylic acid recovery are adversely affected. The possibility of drastically decreasing, and smooth wastewater treatment becomes possible. As a result, (meth) acrylic acid ester can be produced stably. In addition, depending on the type of (meth) acrylic acid ester to be produced and the type of polymerization inhibitor to be added, a polymerization inhibitor is added to the wastewater, and diluted oxygen gas or oxygen gas is blown into the wastewater to keep it in an aerobic atmosphere. Thus, the polymerization prevention effect can be further enhanced.

 Brief Description of Drawings

 FIG. 1 is a flowchart showing an example of a method for producing a (meth) acrylic acid ester of the present invention.

 Explanation of symbols

 2 Conformity layer

 4 Reaction raw materials

 6 Catalyst

 8 Solvent

 10 Additives

 12 Neutralization and washing process

 16 Wastewater storage tank

 18 Polymerization inhibitor tank

 20 Wastewater treatment process

 22 Purification process

 24 products (meth) acrylic acid esters

 30 Recovery of (meth) acrylic acid

 BEST MODE FOR CARRYING OUT THE INVENTION

 Hereinafter, the present invention will be described in detail with reference to the drawings.

 [0024] Fig. 1 is a flowchart showing a process for producing a (meth) acrylic acid ester by dehydration ester-acid reaction. In FIG. 1, 2 is an esterification reaction process, in which an esterification reaction is performed using a reaction tank (not shown). The reaction vessel is equipped with a heating device, a stirring device and the like. The reaction raw material 4 (meth) acrylic acid and alcohol are supplied to this reaction tank.

[0025] When the (meth) acrylic acid ester is produced by the transesterification method, (meth) acrylic acid ester and alcohol are supplied as the reaction raw material 4 to the reaction vessel. [0026] Further, the esterification reaction catalyst 6, the solvent 8, various additives 10, and the like are supplied to the reaction tank. In this state, the mixture is heated with normal stirring, and a dehydrating esterification reaction is performed.

 [0027] Examples of the raw material alcohol include monovalent aliphatic alcohols such as methanol, ethanol, propanol, butanol, and 2-ethylhexisanol; ethylene glycol, propylene glycol, polyethylene glycol, polypropylene glycol, glycerin, and diglycerin. , Pentaerythritol, dipentaerythritol, trimethylolpropane, ditrimethylolpropane, tris (2-hydroxyethyl) isocyanurate, alkylene oxide modified ditrimethylolpropane, alkylene oxide modified pentaerythritol, tricyclodecane dimethylol, etc. A polyhydric aliphatic alcohol; an alkylene oxide adduct of the mono- or polyhydric aliphatic alcohol; an alkylene oxide-modified phenol, an alkylene Monovalent aromatic alcohols such as oxide modified norphenol and alkylene oxide modified paracumyl phenol; Polyvalent aromatic alcohols such as alkylene oxide modified bisphenol A and alkylene oxide modified bisphenol F; Polyester polyol and epoxy resin Examples thereof include oligomers such as diglycidyl ether. Examples of the alkylene oxide include ethylene oxide and propylene oxide.

 [0028] The blending amount of (meth) acrylic acid and alcohol is determined in consideration of the valence of alcohol, selectivity of the ester to be produced, reaction rate, and the like. Usually 0.5 1.5 equivalents of (meth) acrylic acid is added per OH— group of alcohol. Considering the reaction rate, the amount of (meth) acrylic acid is preferably slightly more than 1 equivalent per OH group of the alcohol.

 The esterification reaction catalyst 6 is preferably an organic strong acid such as trifluoroacetic acid or paratoluenesulfonic acid, or an inorganic strong acid such as sulfuric acid or hydrochloric acid. A solid strong acid such as a cation exchange resin is also preferred. The blending amount of the ester ester reaction catalyst is preferably 0.2 to 30% by mass based on (meth) acrylic acid.

[0030] The solvent 8 is preferably a solvent that is insoluble or hardly soluble in water and forms an azeotrope with water. For example, hydrocarbon solvents such as benzene, xylene, cyclohexane, n-xane, n-heptane, and trichloroethane, tetrachloroethylene, methyl chloroform, etc. Examples thereof include an ether solvent such as a rogen solvent and diisopropyl ether. The amount of the solvent is not particularly limited, but it is preferable that the concentration of (meth) acrylic acid is 10% by mass or more.

 [0031] Examples of various additives 10 include polymerization inhibitors.

 [0032] As a general polymerization inhibitor, as an inorganic polymerization inhibitor, there are salted iron (III), salted cupric, activated alumina, sodium thiocyanate and the like. Examples of organic polymerization inhibitors include benzoquinone, 2-t-butylhydroquinone, 1,4 naphthoquinone, 1,4 naphthoquinone 2-sulfonate, 4-t-butylcatechol, bis (3,5 dimethyl-4-hydroxyl Sifenyl) sulfone, phenol, hydroquinone, methylhydroquinone, hydrated quinone monomethyl ether, di-t-butylhydroxytoluene, 6-hydroxy-2,5,7,8-tetramethylchroman 2-strong rubonic acid, para-t-butylphenol, Noranitrofe Noreno, Power Teconole, Lesono Resinole, Honoret Crezonole, 1 Naftonore, Nitrobenzene, Aryl Chloride, 1-Heptene, N Nitrosodimethylamamine, 4-Oxydiphenylamine, Jetyldithiocarbamine Acid salt, 2, 2, 6, 6-tetramethylbiperidine, Xia Njiamido, hexamethylene tetramine, Jifueniruamin, methylene blue, Kuropen, p twelve Toro Seo diphenyl § Min, phenothiazine, chloranil, Ru 1 Nafuchiruamin Nadogaa.

 [0033] Among these polymerization inhibitors, 2 t-butyl hydroquinone having 2 hydroxyl groups, methyl hydroquinone, catechol, hydroquinone, 4-tert-butylinole strength Teconole, benzoquinone having a quinone structure, 1,4 naphthoquinone 2 —Sulfonates are particularly preferred. These polymerization inhibitors may be used alone or in combination.

 [0034] The blending amount of the polymerization inhibitor is preferably 0.002 to 10 mass% based on (meth) acrylic acid.

 [0035] The polymerization inhibitory effect varies depending on the type of the polymerization inhibitor and the like, but the polymerization inhibitory ability of the polymerization inhibitor can be further enhanced by introducing diluted oxygen gas or the like into the reaction system. The oxygen concentration of the diluted oxygen gas is not particularly specified, but is preferably 1 to 20% by volume. The diluent gas is preferably an inert gas such as nitrogen gas, helium gas, or argon gas.

[0036] As described above, (meth) acrylic acid and alcohol are heated in the presence of a catalyst in the reaction vessel 2. The This heating causes a dehydration condensation reaction to produce (meth) acrylic acid ester. Water produced as a by-product of the condensation reaction between (meth) acrylic acid and alcohol is azeotroped with the solvent (for example, toluene) and discharged outside the upper force of the reaction vessel. In addition, the azeotropic gas taken out azeotropically is condensed and only the solvent is refluxed to the reaction vessel.

 [0037] The reaction temperature is preferably 40 to 140 ° C, and the reaction time is preferably 0.5 to 50 hours. In addition

The esterification reaction conditions are well known.

[0038] After the esterification reaction is completed, the reaction product containing the (meth) acrylic acid ester in the reaction tank is sent to the neutralization / water washing step 12. Neutralization · In washing process 12, use detergent.

V. The reaction product is neutralized and washed with water.

[0039] In the present invention, the cleaning agent means an aqueous agent used in the step of neutralizing and washing the reaction mixture, and includes an alkaline aqueous solution used in the neutralization treatment, water used in the washing treatment, saturated saline, and the like. means.

 [0040] The neutralization treatment may be carried out according to a conventional method. For example, an aqueous alkaline solution such as sodium hydroxide, potassium hydroxide, or ammonia is added to the reaction product mixture as an alkaline component and stirred. The method of mixing etc. is mentioned.

 [0041] After the neutralization treatment, liquid-liquid separation is performed to separate an organic layer containing (meth) acrylic acid ester and an aqueous layer.

 [0042] The separated organic layer is further subjected to a water washing step. The water washing step is a step of washing the organic layer with a cleaning agent. If necessary, the reaction product can be washed with water before neutralization.

 [0043] After the water washing treatment, liquid-liquid separation is performed to separate an organic layer and an aqueous layer.

[0044] Neutralization · The water washing step can be carried out a plurality of times.

 [0045] Waste water (water layer) generated as a result of the neutralization and washing treatment is sent to the waste water storage tank 16 and temporarily stored therein as waste water.

[0046] The stored wastewater has a pH of approximately 7 to 14 and a total concentration of alkali components of 0.1.

~ 50 mass%, the total concentration of (meth) acrylic acid and its salt is about 1-50 mass%.

[0047] The wastewater generated in the neutralization 'water washing step contains a large amount of (meth) acrylic acid (salt), and when stored as it is, it gels in a short time. [0048] 18 is a polymerization inhibitor tank, and the polymerization inhibitor filled therein is sent to the wastewater storage tank 16. With this polymerization inhibitor sent, polymerization of (meth) acrylic acid in the wastewater stored in the wastewater storage tank 16 is suppressed, and gelling of the wastewater is prevented.

 [0049] In the present invention, the waste water has a pH of 7 to 14, a total concentration of alkali components of 0.1 to 50% by mass, and a total concentration power of (meth) acrylic acid and its salt ^ to 50% by mass. Can be preferably applied.

 [0050] The amount of the polymerization inhibitor added to the wastewater varies depending on the concentration of (meth) acrylic acid and salts thereof contained in the wastewater, the number of days to store, the type of polymerization inhibitor to be added, and the like. Generally, it is preferable to add the polymerization inhibitor so that the concentration in the waste water is 0.005% by mass or more, more preferably 0.01 to 10% by mass.

 [0051] The amount of the polymerization inhibitor added to the wastewater varies depending on the concentration of (meth) acrylic acid and salts thereof contained in the wastewater, the number of days to store, the type of polymerization inhibitor to be added, and the like.

[0052] In the present invention, the addition amount of the polymerization inhibitor, the concentration in the waste water was added to a above 005 wt% 0., 0.01 to 10 weight _^0/0 are preferred.

 [0053] Examples of inorganic polymerization inhibitors include copper chloride, salted iron (III), activated alumina, sodium thiocyanate, and the like.

 [0054] Organic polymerization inhibitors include benzoquinone, 2-t-butylhydroquinone, 1,4-naphthoquine, 1,4 naphthoquinone 2-sulfonate, 4-t-butylcatechol, bis (3,5- Dimethyl-4-hydroxyphenol) sulfone, phenol, hydroquinone, methyl hydroquinone, hydroquinone monomethyl ether, di-t-butylhydroxytoluene, 6-hydroxy 2, 5, 7, 8-tetramethylchroman 2-force rubonic acid, para-t Butylphenol, paranitrophenol, catechol, resorcinol, orthocresol, 1 naphthol, nitrobenzene, allyl chloride, 1 heptene, N ditrosodimethylamine, 4-oxydiphenylamine, jetyldithiocarnomate, 2, 2, 6, 6-tetramethylbiperidine, dicyandia Amide, hexamethylenetetramine, diphenylamine, methylene blue, clopene, p-trosodiphenylamine, phenothiazine, chloranil, 1-naphthylamine and the like.

[0055] Of these, aromatic derivatives having two or more hydroxyl groups are preferred. 3 or more hydroxyl groups Pyrogallol, hydroxynol, phloroglycine, trihydroxynaphthalene, gallic alcohol and the like can be given as derivatives having the above.

 [0056] Examples of aromatic derivatives having two hydroxyl groups include catechol, 4 t-butyl catechol, hydroquinone, 2-t butyl hydroquinone, methyl hydroquinone, and the like.

 [0057] Examples of the quinone derivative include quinone, benzoquinone, 1,4 naphthoquinone, 1,4 anthraquinone, 4-naphthoquinone mono-2-sulfonate, and the like. These may be used alone or in combination. In particular, rho, idroquinone, 2-t-butylnodroquinone and 1,4 naphthoquinone are preferred.

 [0058] By adding the polymerization inhibitor to the wastewater and introducing the diluted oxygen gas into the wastewater storage tank 16, the polymerization inhibitory ability of the polymerization inhibitor can be further enhanced. The oxygen concentration of the diluted oxygen gas is not particularly specified, but is preferably 1 to 20% by volume.

 [0059] Further, the waste water temperature in the waste water storage tank is preferably maintained at 50 ° C or lower in order to further improve the ability to prevent polymerization, and more preferably 0 to 50 ° C.

 [0060] The wastewater stored in the wastewater storage tank 16 is sequentially sent to the wastewater treatment step 20 for wastewater treatment. Examples of the wastewater treatment method include biological treatment methods and combustion methods in which the entire amount of wastewater is burned using a burner.

 [0061] The waste water stored in the waste water storage tank 16 may be directly sent to the waste water treatment step as described above. Alternatively, after the (meth) acrylic acid in the wastewater has been collected in advance, it may be sent to the wastewater treatment process 20 to be treated with wastewater! ヽ ((Meth) ataryl acid shown by the dotted line in Fig. 1 Recovery 30).

 [0062] The organic layer containing (meth) acrylic acid ester obtained by the liquid separation treatment in the neutralization and water washing step 12 is further sent to the purification step 22. In the purification step, the organic layer is purified by a known purification method such as solvent removal treatment, filtration treatment, adsorption treatment, or extraction treatment, if necessary, to obtain the product (meth) acrylate ester 24.

[0063] Examples of the (meth) acrylic acid ester produced by the above method include (meth) acrylic acid methyl, (meth) acrylic acid ethyl, (meth) acrylic acid butyl, and alkylene oxide-modified phenol ( (Meth) acrylic acid esters, (meth) acrylic acid esters of alkylene oxide modified norphenol, (meth) acrylic acid (meth) acrylic acid esters, (poly) alkylene glycols, al (Meth) acrylic ester of xylene oxide modified bisphenol A, (meth) acrylic ester of alkylene oxide modified paracumylphenol, alkylene oxide modified (meth) acrylic ester of 2-ethylhexyl, alkylene oxide modified bisphenol F (meth) acrylic acid ester, tricyclodecane dimethylol acrylic acid ester, alkylene oxide modified (di) glycerin acrylic acid ester, (di) pentaerythritol acrylic acid ester, (di) trimethylolpropane Acrylic acid ester, alkylene oxide modified (di) trimethylolpropane acrylic acid ester, alkylene oxide modified pentaerythritol acrylic acid ester, polyester acrylate, epoxy There is Shiatarireto like.

 [0064] The method for producing the (meth) acrylate ester is particularly useful as a method for producing a (meth) acrylate ester using a polyhydric alcohol having two or more hydroxyl groups as a raw material.

 [0065] In the above description, the dehydration reaction using (meth) acrylic acid and alcohol as reaction raw materials has been described as an example. However, the production method of the present invention is not limited to this.

It can also be applied to the case where (meth) acrylic acid ester is produced by a transesterification reaction using (meth) acrylic acid ester and alcohol as reaction raw materials. In this case, the transesterification reaction itself is known and conventionally known reaction conditions can be used as they are.

 Further, in the above description, the polymerization inhibitor was supplied to the waste water storage tank 16. However, the present invention is not limited to this, and the polymerization inhibitor may be supplied to the wastewater at an arbitrary position after the neutralization and water washing step 12.

 Example

[0067] Example 1

 <Reaction process>

 A reactor equipped with a stirrer and a thermometer was charged with 240 g of dipentaerythritol, 485 g of acrylic acid, 400 g of toluene, 1.15 g of secondary salty copper and 11.5 g of 78% sulfuric acid, and under a pressure of 53.2 kPa, The jacket temperature was kept at 102 ° C. to initiate dehydration ester reaction.

[0068] The reaction proceeded while water produced during the reaction was azeotroped with toluene and discharged out of the system.

After 17 hours, the esterification reaction was stopped. The mass of the reaction product (solution) is 1,050 g. As a result, the acid value after the reaction was 1.65 meqZg. After cooling the reaction solution, 580 g of toluene was added to the reaction product and diluted.

 [0069] <Washing process>

 This washing step is a step in which cupric chloride used as a polymerization inhibitor during synthesis is extracted and removed with pure water. To the reaction product solution diluted with toluene, 55 g of pure water was added and stirred for 15 minutes. Thereafter, the mixture was allowed to stand for 1 hour to separate into an upper layer (organic layer, 1,620 g) and a lower layer (aqueous layer, 65 g). The acid value of the organic layer was measured and found to be 0.91 meqZg.

 [0070] <First neutralization step>

 The first neutralization step is a step of extracting and removing the esterification reaction catalyst and the remaining acrylic acid in the organic layer from the organic layer using a sodium hydroxide aqueous solution. To the organic layer obtained in the water washing step, 295 g of a 20% aqueous sodium hydroxide solution was added and stirred for 15 minutes. Then, let stand for 1 hour and separate it into upper layer (organic layer, 1,500 g) and lower layer (aqueous layer, 415 g).

 [0071] <Second neutralization step>

 To the organic layer separated in the first neutralization step, 490 g of a 20% sodium hydroxide aqueous solution was added and stirred at 30 ° C. for 1 hour. Thereafter, the mixture was allowed to stand for 1 hour and separated into an upper layer (organic layer, 1,430 g) and a lower layer (aqueous layer, 560 g).

 [0072] <Method for evaluating the stability of wastewater>

 The stability of the water layer (waste water) generated in the first and second neutralization steps was evaluated under the following conditions.

 [0073] (1) The waste water was placed in a test bottle, and a polymerization inhibitor was added to a predetermined concentration.

 [0074] The wastewater to which the polymerization inhibitor is added is subjected to an aerobic atmosphere or an anaerobic atmosphere.

Stored at 0 ° C for 14 days. Then, the presence or absence of the generation | occurrence | production of the gel in waste_water | drain was confirmed visually.

[0075] In an aerobic atmosphere, 5% oxygen gas (the rest is nitrogen gas) was blown into the test bottle for 15 minutes.

After completion of blowing, it was formed by sealing. The anaerobic atmosphere was formed by blowing nitrogen gas into the test bottle for 15 minutes, and sealing the bottle after completion of the blowing.

[0076] (2) The evaluation of the difficulty of Gelui was expressed by the number of days from the start of storage to the generation of a force gel under the above conditions. [0077] (3) After the storage for 14 days, if a gel was generated, the state of the gel was observed.

 [0078] <Evaluation result>

 1,4-Naphthoquinone was added to the wastewaters of the first neutralization step and the second neutralization step so as to be 2000 ppm, respectively, and stored at 40 ° C. in an aerobic atmosphere. The wastewater from the first neutralization process generated a gel on the 12th day from the start of storage. After 14 days, the wastewater was in a viscous state.

 [0079] The wastewater in the second neutralization step was strongly affected by gel generation. The results are shown in Table 1.

[0080] Comparative Example 1

 Waste water from the first neutralization step and the second neutralization step was obtained in the same manner as in Example 1.

[0081] <Evaluation result>

 A polymerization inhibitor was not added to the waste water in the first neutralization step and the second neutralization step, and an aerobic atmosphere was prepared in the same manner as in Example 1 and then stored at 40 ° C. The wastewater from the first neutralization process was gelled on the second day from the start of storage and the wastewater from the second neutralization process was gelled on the fourth day. All wastewater after 14 days had solidified.

[0082] Example 2

 Waste water from the first neutralization step and the second neutralization step was obtained in the same manner as in Example 1.

[0083] <Evaluation result>

 1,4-Naphthoquinone 2000ppm was added to the wastewaters of the first neutralization step and the second neutralization step, respectively, and stored at 40 ° C in an anaerobic atmosphere. The first neutralization process wastewater generated gel on the 11th day from the start of storage, and the second neutralization process wastewater generated on the 14th day. The wastewater after 14 days was in a viscous state.

[0084] Example 3

 Waste water from the first neutralization step and the second neutralization step was obtained in the same manner as in Example 1.

[0085] <Evaluation result>

1,4-Naphthoquinone lOOOOppm was added to the wastewaters of the first neutralization step and the second neutralization step, respectively, and stored at 40 ° C. in an aerobic atmosphere. Gel was generated in the wastewater from the first neutralization process on the 9th day from the start of storage and in the wastewater from the second neutralization process on the 14th day. The wastewater after 14 days was in a viscous state. [0086] Example 4

 Waste water from the first neutralization step and the second neutralization step was obtained in the same manner as in Example 1.

[0087] <Evaluation result>

 1,4-Naphthoquinone 50ppm was added to the waste water from the first and second neutralization steps, respectively, and stored at 40 ° C in an aerobic atmosphere. Gel was generated in the wastewater of the first neutralization process on the third day from the start of storage and in the wastewater of the second neutralization process on the seventh day. After 14 days, the wastewater from the first neutralization process was solidified and the wastewater from the second neutralization process was viscous.

[0088] Example 5

 Waste water from the first neutralization step and the second neutralization step was obtained in the same manner as in Example 1.

[0089] <Evaluation results>

 1,4-Naphthoquinone (2000 ppm) was added to the wastewater from the first neutralization step and the second neutralization step, respectively, and stored at 60 ° C. in an aerobic atmosphere. Gel was generated in the wastewater from the first neutralization process on the fifth day from the start of storage, and the wastewater in the second neutralization process on the sixth day. The wastewater after 14 days had solidified.

[0090] Example 6

 Waste water from the first neutralization step and the second neutralization step was obtained in the same manner as in Example 1.

[0091] <Evaluation result>

 The waste water from the first neutralization step and the second neutralization step was each added with 2000 ppm hydroquinone and stored at 40 ° C in an aerobic atmosphere. Gel was generated on the 8th day from the start of storage in the wastewater of the first neutralization process. No gel was generated in the wastewater from the second neutralization step. The wastewater from the first neutralization process after 14 days was in a viscous state.

[0092] Example 7

 Waste water from the first neutralization step and the second neutralization step was obtained in the same manner as in Example 1.

[0093] <Evaluation result>

Hydroquinone (2000 ppm) was added to the wastewater from the first neutralization step and the second neutralization step, respectively, and stored at 40 ° C in an anaerobic atmosphere. In the wastewater from the first neutralization process, gelation occurred on the 4th day, and on the 11th day, the wastewater from the second neutralization process. After 14 days The wastewater from the first neutralization process was solidified and the wastewater from the second neutralization process was viscous.

 [0094] Example 8

 Waste water from the first neutralization step and the second neutralization step was obtained in the same manner as in Example 1.

[0095] <Evaluation result>

 The waste water from the first neutralization step and the second neutralization step was respectively supplemented with 2000 ppm hydroquinone monomethyl ether and stored at 40 ° C. in an aerobic atmosphere. As a result, the first neutralization process wastewater generated gel on the third day from the start of storage, and the second neutralization process wastewater generated on the seventh day. After 14 days, the wastewater from the first and second neutralization steps was solidified.

 Example 9 Waste water from the first neutralization step and the second neutralization step was obtained in the same manner as in Example 1.

[0097] <Evaluation result>

 Methylene blue (2000 ppm) was added to the wastewater from the first neutralization step and the second neutralization step, respectively, and stored at 40 ° C. in an aerobic atmosphere. Gel was generated in the wastewater of the first neutralization process on the third day from the start of storage and on the fifth day in the wastewater of the second neutralization process. After 14 days, the wastewater in the first and second neutralization steps was solidified.

 [0098] From the above results, any of Examples 1 to 9 has a longer gel generation period than Comparative Example 1.

[0099] [Table 1]

[]

table 1

In a reactor equipped with a stirrer and a thermometer, polyethylene glycol # 200 (average molecular weight 200 ゝ 4 to 5) 460 g, attalinoleic acid 395 g, tonolene 380 g, secondary salt 匕 copper 0.25 g, nora toluenesulfonic acid 25 . 3g was charged. The dehydration esterification reaction was started at a pressure of 54.5 kPa in the reactor and a jacket temperature of 110 ° C. The water produced during the reaction was azeotroped with toluene and allowed to react outside the system. The reaction was stopped after 11 hours of reaction initiation. The mass of the reaction solution at this time was 1,180 g, and the acid value of the reaction solution was 1.03 meqZg. After cooling the reaction solution, 420 g of toluene was added to the reaction solution and diluted.

[0101] <Neutralization process>

 To the solution diluted with toluene, 300 g of a 20% aqueous sodium hydroxide solution was added and stirred for 5 minutes. The mixture was allowed to stand for 1 hour, and the upper layer (organic layer; 1,420 g) and the lower layer (aqueous layer; 480 g) were separated.

[0102] <Stability evaluation of wastewater>

 The evaluation method was performed in the same manner as in Example 1.

[0103] <Evaluation result>

 1,4-Naphthoquinone 2000ppm was added to the water layer (waste water) in the neutralization process obtained by the above method, and kept at 40 ° C and stored in an aerobic atmosphere. The wastewater from the neutralization process was not able to gel during the 14-day test period.

[0104] Example 11

 Waste water was obtained in the same manner as in Example 10.

[0105] <Evaluation result>

 The wastewater from the neutralization process was supplemented with 2000 ppm hydroquinone and stored at 40 ° C in an aerobic atmosphere. As a result, the wastewater from the neutralization process gelled on the 14th day from the start of storage. Wastewater was viscous.

[0106] Comparative Example 2

 Wastewater for the neutralization step was obtained in the same manner as in Example 10.

[0107] <Evaluation result>

No polymerization inhibitor was added to the wastewater in the neutralization process, and it was stored at 40 ° C in an aerobic atmosphere. As a result, the wastewater from the neutralization process gelled within 24 hours from the start of storage. 14 The wastewater after the lapse of days was solidified.

 [0108] Example 12

 Wastewater for the neutralization step was obtained in the same manner as in Example 10.

[0109] <Evaluation result>

 The wastewater from the neutralization process was supplemented with 2000 ppm of hydroquinone monomethyl ether and stored at 40 ° C in an aerobic atmosphere. The wastewater from the neutralization process was gelled 28 hours after the start of storage. The wastewater after 14 days was solidified.

[0110] Example 13

 <Reaction process>

 A reactor equipped with a stirrer and a thermometer was charged with 150 g of tetrahydrophthalic anhydride, 265 g of trimethylo-lep p-non, 285 g of acrinole, 660 g of 卜 nolene, 0.03 g of phenothiazine, and 25.7 g of norenoleene sulfonic acid. . The inside of the reactor was brought to normal pressure, the reactor jacket temperature was set to 105 ° C, and the dehydrating ester reaction was started. The water produced during the reaction was azeotroped with toluene, and the reaction proceeded while being discharged out of the system. The esterification reaction was stopped 11 hours after the start of the reaction. The mass of the reaction solution at this time was 1,305 g, and the acid value of the reaction solution was 0.54 meqZg. After cooling the reaction solution, the reaction solution was diluted with 290 g of toluene.

[0111] Neutralization Process>

 To the reaction solution diluted with toluene, 220 g of 5% aqueous ammonia was added and stirred for 20 seconds. The mixture was allowed to stand for 1 hour and separated into an upper layer (organic layer; 1,585 g) and a lower layer (aqueous layer; 230 g).

[0112] <Evaluation of stability of wastewater>

 The method for evaluating the stability of wastewater was carried out by the method shown in Example 1.

[0113] <Evaluation result>

 10-OOppm of 2-t-butylhydroquinone was added to the lower layer (waste water) of the neutralization step obtained by the above method, and the mixture was stored at 40 ° C in a 5% oxygen atmosphere. As a result, the wastewater from the neutralization process did not gel during the test period.

[0114] Example 14

Waste water for the neutralization step was obtained in the same manner as in Example 13. [0115] <Evaluation result>

 2-t-Butylhydroquinone was added to lOOOppm of the wastewater obtained in the neutralization step and stored at 40 ° C in an anaerobic atmosphere. As a result, the wastewater from the neutralization process was not able to gel during the test.

[0116] Comparative Example 3

 Waste water for the neutralization step was obtained in the same manner as in Example 13.

[0117] <Evaluation result>

 The resulting neutralization process wastewater was stored without being added with a polymerization inhibitor and kept at 40 ° C. in an aerobic atmosphere. As a result, the wastewater from the neutralization process was gelled within 24 hours after the start of storage. The wastewater after 14 days was solidified.

[0118] As described above, in any of Examples 10 to 14, the gel generation date is longer than those of Comparative Examples 2 and 3.

[0119] [Table 2]

Lulu of the day after departure

 Size Waste Waste Concentration Neutralization Water Neutralization Process

 ) (曰 p p m

 It is not alive, but it is a natural example.

 Viscous aerobic

 Comparison of time-to-shape aerobic comparison 20

 An aerobic example between time-treatment shapes

 〇 〇

 Dimension Dimension Dimension Chimetenore / No Yes

 2 tons of quinolone and quinolone do not live and tempered and tidy tongue and 2 ton of quinone

〇 〇

 Comparison between temperament and temperament temperament comparison ratio 3 24 π

 Noisy 1

 W

〇 inch

[0120] Examples 15 to 20, Comparative Examples 4 and 5

 The wastewater from the neutralization process obtained in Examples 1, 10, and 13 was mixed at the ratio shown in Table 3.

[0121] <Evaluation result> 1,4 naphthoquinone, hydroquinone, and 2 t-butylhydroquinone were added to the wastewater mixed at the ratio shown in Table 3 to a predetermined concentration and stored at 40 ° C in an anaerobic atmosphere. The presence or absence of gel generation and the state of the gel are shown in Table 3.

 [0122] It can be seen that any of Examples 10 to 14 has a longer gel generation date than Comparative Examples 4 and 5 to which no polymerization inhibitor was added.

[0123] [Table 3]

Table 3

Claims

The scope of the claims  [1] An esterification reaction step of obtaining a reaction product containing (meth) acrylic acid ester by dehydration esterification reaction of (meth) acrylic acid and alcohol or transesterification reaction of (meth) acrylic acid ester and alcohol; The reaction product obtained in the esterification reaction step is separated into a liquid layer containing a (meth) acrylic acid ester and a water layer containing a water-soluble component by liquid-liquid separation using a detergent. And a product refining process for extracting (meth) acrylic acid esters from the organic layer separated in the neutralization / water washing process, and a storage for storing the water layer separated in the neutralization / water washing process as waste water in a waste water storage tank. And a wastewater treatment step of treating the wastewater in the wastewater storage tank stored in the wastewater storage step as a wastewater treatment step, the method for producing a (meth) acrylate ester, wherein the neutralization step (Meth) acrylic is characterized in that the concentration of polymerization inhibitor in wastewater stored in the wastewater storage tank is maintained at 0.005% by mass or more by adding a polymerization inhibitor to the water layer separated in the washing step. A method for producing acid esters.  [2] The method for producing a (meth) acrylic acid ester according to claim 1, wherein the internal space of the wastewater storage tank is maintained in an oxygen-containing atmosphere.  [3] The process for producing a (meth) acrylate according to claim 1, wherein the temperature of the waste water in the waste water storage tank is maintained at 0 to 50 ° C.  [4] Wastewater treatment process: wastewater treatment by directly combusting wastewater in the wastewater storage tank, or wastewater treatment by burning wastewater after collecting the wastewater power (meth) acrylic acid in the storage tank The method for producing a (meth) acrylic acid ester according to claim 1, wherein the method is a step of performing the step.  [5] The process for producing a (meth) acrylic acid ester according to claim 1, wherein the alcohol to be reacted by dehydration esterification reaction or transesterification reaction is a polyhydric alcohol.  [6] The process for producing a (meth) acrylic acid ester according to claim 1, wherein the polymerization inhibitor is an aromatic derivative or a quinone derivative having two or more hydroxyl groups. [7] The pH of the aqueous layer is 7 to 14, the total concentration of alkali components is 0.1 to 50% by mass, and the total concentration of (meth) acrylic acid and its salt is 1 to 50% by mass. A method for producing the (meth) acrylic acid ester according to the item.