WO2006126479A1 - Method for producing acrylic ester - Google Patents

Abstract

[PROBLEMS] To provide a method for producing a high boiling acrylic ester having a reduced discoloration without employing distillation in the purification process. [MEANS FOR SOLVING PROBLEMS] A method for producing a high boiling acrylic ester having an APHA of 100 or less, characteristic in that, in the production of a high boiling acrylic ester by the esterification reaction of an acrylic acid and an alcohol, the acrylic acid contains an aldehyde in an amount of 100 ppm by weight or less and the resulting acrylic ester is not distilled in a purification process. The aldehyde is preferably furfural contained in an amount of 45 ppm or less, more preferably, in an amount of 10 ppm or less.

Description

 Specification

 Method for producing acrylic ester

 Technical field

 TECHNICAL FIELD [0001] The present invention relates to a method for producing a high-boiling acrylate ester without purification by distillation, represented by an acrylate ester, in particular, an acrylate ester of pentaerythritol or polyalkyleneoxide-modified phenol. .

 Background art

 [0002] Distillation is not usually carried out as a purification means for the production of acrylic esters because of high boiling point and easy distillation. High boiling acrylic acid esters are usually produced by direct esterification of atalic acid and alcohol in an organic solvent. In this direct esterification, it is not preferable that unreacted alcohol having a high boiling point and difficult to be removed by distillation becomes an impurity and remains in the final product. Therefore, excess acrylic acid is used with respect to the alcohol. As a result, the reaction product liquid contains a large amount of attalic acid in addition to the acrylate ester. Such excess acrylic acid is removed by washing the reaction solution with alkaline water. Then, the organic solvent is removed by distillation, whereby the high-boiling acrylic ester that is the final product can be obtained.

 [0003] As described above, the production of high boiling point acrylic acid ester cannot be purified by distillation, and requires steps such as alkaline cleaning and solvent removal. Therefore, acrylic acid obtained by the quality of attalinoleic acid is required. The quality of the ester was also affected, and in particular, the acrylic ester was colored.

 [0004] Generally, acrylic acid is produced by a gas phase oxidation reaction of propylene, and therefore contains aldehydes as impurities.

In Patent Document 1, acrylates such as furfural and benzaldehyde, maleic anhydride, j8- are used in the production of acrylate esters by esterification reaction of acrylic acid and alcohol obtained by propylene gas-phase acid-acid reaction. It is described that the use of acrylic acid containing a specific amount of ataloxypropionic acid, etc. causes blockage of equipment such as piping due to the polymer, a decrease in the main raw material unit, and a change in the polymerization behavior of the product. However, specifically exemplified in Patent Document 1 is an acrylic acid ester of a low-boiling alcohol that can be distilled as a purification process, and a specific description of an acrylate ester of a high-boiling alcohol. Flower ,.

 Furthermore, as a result of the study by the present inventors, it was found that when used in a high boiling acrylic acid ester, the coloration of the product cannot be solved only by using acrylic acid described in Patent Document 1.

 Patent Document 1: Japanese Patent Application Laid-Open No. 2003-171347

 Disclosure of the invention

 Problems to be solved by the invention

[0006] The present invention seeks to provide a high-boiling acrylate ester having low coloration and excellent quality by controlling specific aldehydes in acrylic acid.

 Means for solving the problem

[0007] As a result of intensive studies to solve the above problems, the present inventor has completed the present invention.

 That is, the present invention uses acrylic acid containing 100 ppm by weight or less of aldehydes when producing high boiling acrylic acid ester by esterification reaction of acrylic acid and high boiling point alcohol, and acrylic acid as a purification step. APHA is 100 or less acrylic ester production method characterized by not using ester distillation.

 The invention's effect

 [0008] According to the present invention, a high-boiling acrylic ester with little coloring can be easily produced. In addition, a composition containing such an acrylate ester can be suitably used in fields requiring high colorless transparency such as optical materials.

 BEST MODE FOR CARRYING OUT THE INVENTION

[0009] The acrylic acid of the present invention needs to contain aldehydes in an amount of lOOppm or less. If it exceeds ΙΟΟρρ m, it cannot be used for applications such as optical members where the final product is highly colored. The preferred amount of aldehydes is 45 ppm or less. Examples of aldehydes include acrolein, furfural, and benzaldehyde. Particularly, furfural affects coloring. Give a sound. Therefore, when the aldehyde is only furfural, lOppm or less is preferable, and 5ppm or less is particularly preferable. When it contains furfural, even if all aldehydes are lOOppm, it is preferable that furfural is 5 ppm or less, and 2.5 ppm or less is particularly preferable. Unless otherwise specified, ppm in the present invention indicates ppm by weight.

 Furfural is not so large in boiling point with acrylic acid, so it is mixed in acrylic acid. This contamination is not preferable for the production of high boiling acrylic acid esters without purification by distillation. Therefore, it is necessary to use acrylic acid as the raw material that does not contain furfural at first.

 [0010] Although the reason why aldehydes cause coloration is not clear, furfural has a property of becoming greased through yellowish yellow when exposed to light in the air. It may be colored by heating or the like during removal.

 [0011] The acrylic acid in the present invention is an acrylic acid produced by a gas-phase acid reaction of propylene.

 As the acrylic acid used in the present invention, those obtained by any production method can be used as long as they contain aldehydes in an amount of lOOppm or less. For example, a method of distilling the crude acrylic acid obtained after reacting propylene with a gas phase acid can be mentioned.

 In the present invention, as a preferred method for producing acrylic acid so that the aldehyde is reduced to lOOppm or less, propylene is subjected to a gas phase oxidation reaction according to a conventional method, and then the obtained crude attalic acid is converted into hydrazine water. Examples include distillation in the presence of a hydrate (hydraulic hydrazine). The ratio of hydrazine hydrate to crude acrylic acid in this case is preferably 0.01 to 5% by mass.

As distillation conditions in this case, it is preferable to distill at a lower temperature in order to suppress decomposition of the compound in which aldehydes are captured with hydrazine hydrate. Specifically, it is preferable to distill under reduced pressure. As the pressure in this case, 5 ~ 50torr is preferred as the temperature is 70 ~: LOO ^Q C force S preferred ヽ.

Hydrazine hydrate can be added before or during distillation. [0012] The high-boiling acrylic ester produced in the present invention preferably has a boiling point of 100 ° C or higher under the pressure of lOtorr. Examples of powerful esters include acrylic acid esters of alkylene oxide modified phenols, acrylic acid esters of alkylene oxide modified norphenols, acrylic esters of (poly) alkylene glycols, acrylic esters of alkylene oxide modified bisphenol A, and alkylene oxide modified. P-cumylphenol acrylate ester, alkylene oxide modified 2-ethylhexyl acrylate ester, alkylene oxide modified bisphenol F acrylate ester, tricyclodecane dimethylol acrylate ester, alkylene oxide modified (di) Glycerin (Di) pentaerythritol acrylate, (di) trimethylolpropane acrylate, alkylene Examples thereof include acrylic acid esters of xoxide-modified (di) trimethylolpropane and acrylic acid esters of alkylene oxide-modified pentaerythritol.

 [0013] As the raw material alcohol, an alcohol corresponding to the high boiling acrylic acid ester may be used. Monovalent, divalent, and polyvalent alcohols can be used as the alcohol.

 [0014] The acrylic ester is produced by an esterification reaction of acrylic acid and alcohol.

 The esterification reaction may be carried out in accordance with a conventional method, for example, a method in which acrylic acid and alcohol are heated and stirred in an organic solvent in the presence of an acid catalyst.

 The reaction ratio of acrylic acid (COOH) to alcohol (OH) is preferably such that the molar ratio of atalic acid to alcohol is 1.1 to 1.5 times.

 Preferred acid catalysts include sulfuric acid, paratoluenesulfonic acid, methanesulfonic acid and the like. The preferred use amount of the acid catalyst is about 0.01 to 0.20 times that of acrylic acid.

 Furthermore, as the organic solvent, benzene, toluene, n-hexane, cyclohexane, methylcyclohexane and water which are azeotropic with water are preferable because water generated in the esterification reaction can be efficiently removed. Examples include diisopropyl ether, and toluene is preferred. The amount of the organic solvent used relative to the acid or alcohol is preferably such that the concentration of the resulting ester is 30 to 80% by mass.

In the reaction, hydroquinone (hereinafter referred to as HQ) is contained in the reaction solution to prevent polymerization. It is preferable to add one or more polymerization inhibitors such as hydroquinone monomethyl ether (hereinafter referred to as MEHQ), phenothiazine, copper sulfate and copper chloride. Preferably, the amount used is 100 to 5000 ppm with respect to the total liquid volume.

[0015] The esterification reaction can be carried out at a temperature of 80 to 120 ° C for 5 to 20 hours. The reaction is carried out while supplying a mixed gas of oxygen and nitrogen with an oxygen concentration of 3% to 10%.

 [0016] After the ester reaction is completed, it is preferable to neutralize the reaction solution using an alkaline aqueous solution for the purpose of removing unreacted acrylic acid and acid catalyst. By washing the reaction solution with an alkaline aqueous solution, unreacted acrylic acid can be transferred to the aqueous alkaline solution side as a water-soluble salt.

 As the alkaline aqueous solution, a sodium hydroxide aqueous solution or the like is preferable. The concentration of the aqueous alkal solution is preferably about 10-30% by mass. If it exceeds 30% by mass, a precipitate may be generated in the aqueous phase from which the acid has been extracted. If it is less than 10% by mass, the amount of use increases and the time for liquid-liquid separation between the organic phase and the aqueous phase increases. become longer. The amount of alkali used is preferably 1.0 times or more, specifically about 1.1 to 2.0 times the acid value of the reaction solution. A solvent may be added to accelerate the liquid-liquid separation between the organic and aqueous phases.

 [0017] An acrylic ester can be obtained by removing the solvent after washing the organic phase with water. As the additional solvent used for washing with water, a compound having a boiling point lower than that of acrylic acid is preferable. Examples thereof include benzene, toluene, diisopropyl ether, dibutyl ether, ethyl acetate, isopropyl acetate and butyl acetate.

 In the ester synthesis reaction, toluene is preferably used, and toluene is more preferable as an additional solvent.

Next, the solvent is removed from the organic phase by distillation. Distillation may be a shift of notch distillation or continuous distillation. The distillation conditions for solvent cutting may be known conditions depending on the type of solvent. For distilling off the solvent, a pressure of 5 to 50 torr and a can liquid temperature of 50 to: LOO ° C are preferred. When the temperature of the can exceeds 100 ° C, polymerization of the acrylate ester tends to occur during distillation. Distillation is preferably carried out until the solvent content is 1% by weight or less. At the time of distillation, it is preferable to pass a mixed gas containing oxygen gas through the can liquid to prevent polymerization.

 Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples.

[0020] Example 1

 Acrylic acid was obtained by distilling crude acrylic acid obtained from propylene gas phase acid in the presence of hydrazine hydrate.

 A 1 L flask is charged with 240 g of atanolenolic acid containing 0.8 ppm funolefuranore, 120 g of dipentaerythritol, 370 g of toluene, 5 g of sulfuric acid as an acid catalyst, HQ lg as a polymerization inhibitor, a pressure of 60 kPa, and an oil bath temperature of 120 g. The reaction was stopped for 10 hours while removing water by azeotropy with toluene at ° C.

 200 g of toluene was added to the reaction solution, 250 g of 20% NaOH aqueous solution was added and mixed, followed by standing separation, and the upper and lower layers were separated. Next, lOOg of ion-exchanged water was added to the upper layer, mixed and left to stand, and the upper and lower layers were separated. The upper layer after washing with water was placed in a 2 L flask, and toluene was distilled off under reduced pressure while heating at 80 ° C. When toluene reached 0.5%, the procedure was terminated. Thus, 253 g of ester was obtained. The obtained ester was a high boiling point compound having a boiling point of 100 ° C or higher under the pressure of lOtorr, and the color tone was 40 (APHA).

[0021] Example 2

 Acrylic acid was obtained by distilling crude acrylic acid obtained from propylene gas phase acid in the presence of hydrazine hydrate.

 In a 1 L flask, 80 g of acrylic acid containing 1.9 ppm of furfural, EO adduct of norphenol (addition number 4) 350 g, 250 g of toluene, 5 g of sulfuric acid as the acid catalyst, 3 g of MQO. As the polymerization inhibitor, pressure At 80 kPa and oil bath temperature of 120 ° C, the reaction was stopped for 8 hours while removing water azeotropically with toluene.

200 g of toluene was added to the reaction solution, 50 g of 20% NaOH aqueous solution was added and mixed, followed by standing separation, and the upper and lower layers were separated. Next, lOOg of ion-exchanged water was added to the upper layer, mixed and left to stand, and the upper and lower layers were separated. The upper layer after washing with water was placed in a 2 L flask, and toluene was distilled off under reduced pressure while heating at 80 ° C. End when toluene reached 0.5% By the above operation, 390 g of ester was obtained. The obtained ester was a high boiling point compound having a boiling point of 100 ° C or higher under the pressure of lOtorr, and the color tone was 50 (APHA).

[0022] Example 3

 The synthesis was carried out in the same manner as in Example 1 except that acrylic acid containing 5 ppm of furfural was used. The color tone of the obtained ester was 60 (APHA).

[0023] Example 4

 The synthesis was carried out in the same manner as in Example 1 except that acrylic acid containing 1.5 ppm of furfural was used in which the total amount of aldehydes such as acetoaldehyde, benzaldehyde, and furfural was 25 ppm. The color tone of the obtained ester was 60 (APHA).

[0024] 〇 Comparative Example 1

 The synthesis was performed in the same manner as in Example 1 except that acrylic acid containing 28 lppm of furfural was used. The color tone of the obtained ester was 200 (APHA).

[0025] 〇 Comparative Example 2

 The synthesis was performed in the same manner as in Example 2 except that acrylic acid containing 281 ppm of furfural was used. The resulting ester had a color tone of 150 (APHA)

 Industrial applicability

[0026] The production method of the present invention can be applied to any kind as long as it is a high boiling acrylic acid ester. According to the present invention, the coloration of the acrylic ester can be greatly reduced.

Claims

The scope of the claims  [1] When producing high-boiling acrylates by esterification reaction of acrylic acid and alcohol, use acrylic acid containing 100 wt ppm or less of aldehydes, and do not use distillation of acrylate esters as a purification process. A method for producing a high boiling point acrylic ester having a characteristic APHA of 100 or less.  [2] The method for producing a high boiling acrylic acid ester according to [1], wherein the high boiling acrylic acid ester lOtorr has a boiling point of 100 ° C or higher under pressure.  [3] The method for producing a high boiling acrylic acid ester according to claim 1 or 2, wherein the aldehyde is furfural.  [4] The method for producing a high boiling acrylic acid ester according to claim 3, wherein the content of furfural is 45 ppm by weight or less.  [5] The method for producing a high boiling acrylic acid ester according to claim 4, wherein the content of furfural is 10 ppm by weight or less.  [6] The method for producing a high-boiling acrylate ester according to claim 1 or 2, wherein the aldehyde contains 5 wt ppm or less of furfural. [7] Acrylic acid power According to any one of claims 1 to 6, which is obtained by distilling crude acrylic acid obtained from propylene gas phase acid in the presence of hydrazine hydrate. A high boiling point acrylic ester production method.