HIGH-PURITY CARBOXYLIC ACID ESTER AND METHOD FOR PRODUCING SAME

Abstract

The present invention makes it possible to provide a high-purity carboxylic acid ester in which the Ag, Al, Au, Ca, Cr, Cu, Fe, K, Mg, Na, Sn, and Zn contents as metal impurity contents are each less than 1 ppb and the anionic impurity content is less than 1 ppm. The present invention also makes it possible to provide a method for producing a high-purity carboxylic acid ester, the method including a step for bringing a crude carboxylic acid ester that contains anionic impurities and Ag, Al, Au, Ca, Cr, Cu, Fe, K, Mg, Na, Sn, and Zn as metal impurities into contact with a cation-exchange resin (II), followed by a step for bringing the crude carboxylic acid ester into contact with an anion-exchange resin (III).

Claims

1. A high-purity carboxylic acid ester, wherein Ag, Al, Au, Ca, Cr, Cu, Fe, K, Mg, Na, Sn and Zn contents as metal impurity contents are each less than 1 ppb, and wherein an anionic impurity content is less than 1 ppm.

2. A method for producing a high-purity carboxylic acid ester, the method comprising: bringing a crude carboxylic acid ester that contains anionic impurities and at least Ag, Al, Au, Ca, Cr, Cu, Fe, K, Mg, Na, Sn and Zn as metal impurities into contact with a cation-exchange resin (II); and subsequently bringing the crude carboxylic acid ester into contact with an anion-exchange resin (III).

3. The method for producing a high-purity carboxylic acid ester according to claim 2, which comprises bringing the crude carboxylic acid ester into contact with an anion-exchange resin (I) before bringing the crude carboxylic acid ester into contact with the cation-exchange resin (II).

4. The method for producing a high-purity carboxylic acid ester according to claim 2, wherein the carboxylic acid ester is at least one selected from the group consisting of methyl lactate, ethyl lactate, propyl lactate, methyl -hydroxyisobutyrate, ethyl -hydroxyisobutyrate, propyl -hydroxyisobutyrate, butyl -hydroxyisobutyrate, methyl -hydroxyisobutyrate, ethyl -hydroxyisobutyrate, propyl -hydroxyisobutyrate and butyl -hydroxyisobutyrate.

5. The method for producing a high-purity carboxylic acid ester according to claim 2, wherein in the obtained high-purity carboxylic acid ester, the Ag, Al, Au, Ca, Cr, Cu, Fe, K, Mg, Na, Sn and Zn contents as metal impurity contents are each less than 1 ppb and the anionic impurity content is less than 1 ppm.

6. The method for producing a high-purity carboxylic acid ester according to claim 2, wherein in the crude carboxylic acid ester, the Ag, Al, Au, Ca, Cr, Cu, Fe, K, Mg, Na, Sn and Zn contents as metal impurity contents are each 8 ppb or more and the anionic impurity content is 20 ppm or more.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0018] FIG. 1 is a schematic view showing a process of obtaining a high-purity carboxylic acid ester by flowing a carboxylic acid ester through a weakly basic anion-exchange resin (I), a strongly acidic cation-exchange resin (II) and a weakly basic anion-exchange resin (III) in this order in Examples 1 and 2.

EMBODIMENT FOR CARRYING OUT THE INVENTION

[0019] Hereinafter, the present invention will be described in detail. The present invention relates to a high-purity carboxylic acid ester in which metal impurity contents are each less than 1 ppb and the anionic impurity content is less than 1 ppm, and a method for producing the same.

[0020] The high-purity carboxylic acid ester of the present invention is produced by bringing a crude carboxylic acid ester that contains metal impurities and anionic impurities into contact with a cation-exchange resin and an anion-exchange resin to remove the metal impurities with both the cation-exchange resin and the anion-exchange resin and remove the anionic impurities with the anion-exchange resin. Examples of the anionic impurities of the present invention include a carboxylic acid, which is contained in the crude carboxylic acid ester and is generated by a hydrolysis reaction of the carboxylic acid ester.

[0021] The crude carboxylic acid ester of the present invention contains metal impurities and anionic impurities. It may also contain water as one of other components. Examples of the metal impurities include at least Ag, Al, Au, Ca, Cr, Cu, Fe, K, Mg, Na, Sn and Zn. In the crude carboxylic acid ester of the present invention, the Ag, Al, Au, Ca, Cr, Cu, Fe, K, Mg, Na, Sn and Zn contents as the contents of the metal impurities are each preferably 8 ppb or more. Further, the content of the anionic impurities is preferably 20 ppm or more. According to the present invention, it is possible to produce a high-purity carboxylic acid ester even when using such a crude carboxylic acid ester with a high impurity concentration.

[0022] As the cation-exchange resin (II) to be used in the present invention, an H-type strongly acidic cation-exchange resin and a Na-type strongly acidic cation-exchange resin are preferred, and among them, an H-type strongly acidic cation-exchange resin having a sulfonic acid group can be particularly suitably used. As the above-described cation-exchange resin, a commercially-available product can be used, and specific examples thereof include 15JS-HG DRY (manufactured by Organo Corporation).

[0023] In the present invention, as described later, there are: 1. a method of bringing a crude carboxylic acid ester into contact with a cation-exchange resin and then with an anion-exchange resin; and 2. a method of bringing a crude carboxylic acid ester into contact with an anion-exchange resin, then with a cation-exchange resin, and then with an anion-exchange resin. Hereinafter, the anion-exchange resin that is contacted after contact with the cation-exchange resin is sometimes referred to as an anion-exchange resin (III), and the anion-exchange resin that is contacted before contact with the cation-exchange resin is sometimes referred to as an anion-exchange resin (I).

[0024] Examples of the anion-exchange resins (I) and (III) to be used in the present invention include a strongly basic anion-exchange resin and a weakly basic anion-exchange resin, but a weakly basic anion-exchange resin is preferred, and a free base type weakly basic anion-exchange resin is more preferred. Among them, a weakly basic anion-exchange resin having a tertiary ammonium base can be particularly suitably used. As the above-described anion-exchange resin, a commercially-available product can be used, and specific examples thereof include B20-HG DRY (manufactured by Organo Corporation). In the present invention, the anion-exchange resin (I) and the anion-exchange resin (III) may be the same or different.

[0025] In the present invention, the method for bringing the crude carboxylic acid ester into contact with the cation-exchange resin (II) and anion-exchange resins (I) and (III) is not particularly limited, but a method for flowing the crude carboxylic acid ester through the cation-exchange resin and anion-exchange resins is generally employed. Regarding the temperature conditions at the time of contact, in consideration of durability of ion exchange resins, the temperatures of the crude carboxylic acid ester, cation-exchange resin and anion-exchange resins are preferably 100 C. or lower. Further, the production method of the present invention can be carried out by using either a batch method or a flow method, but in view of purification efficiency, the flow method in which the crude carboxylic acid ester is flowed through columns filled with ion exchange resins is preferably employed. When purification is performed using the flow method, the method of delivering a solution may be either upflow or downflow, and the space velocity of flowing through (SV: Hr.sup.1) is suitably determined depending on the type and viscosity of the solution, pressure loss of resin, etc. but is preferably 1 to 50 Hr.sup.1, and more preferably 10 to 20 Hr.sup.1. The concentration of moisture in the crude carboxylic acid ester is not defined, but when bringing a carboxylic acid ester containing moisture into contact with the cation-exchange resin and flowing it therethrough, an acid content is generated by hydrolysis. When subsequently bringing the carboxylic acid ester containing the increased acid content into contact with the anion-exchange resin and flowing it therethrough, the generated acid content is captured by the anion-exchange resin and shortens the life of the anion-exchange resin. For this reason, the concentration of moisture in the crude carboxylic acid ester is preferably 0.01% by weight or less.

[0026] As the method for producing the high-purity carboxylic acid ester of the present invention, a method in which contact with the anion-exchange resin (I) is performed before contact with the cation-exchange resin (II) is more preferred. When bringing the crude carboxylic acid ester into contact with the cation-exchange resin (II), as described above, the hydrolysis reaction between moisture contained in the crude carboxylic acid ester and the carboxylic acid ester is caused to newly generate the anionic impurities. According to the above-described method, the anionic impurities (the carboxylic acid) contained in the crude carboxylic acid ester are brought into contact with the anion-exchange resin (I) to be captured before contact with the cation-exchange resin (II), thereby reducing the load of the anionic impurities to be subsequently captured by the anion-exchange resin (III). For this reason, the life of the anion-exchange resin (III) can be improved.

EXAMPLES

[0027] Hereinafter, the present invention will be specifically described by way of working examples and comparative examples. However, the present invention is not limited to the working examples. Note that the concentrations of the metal impurities and anionic impurities in the carboxylic acid ester were analyzed as described below.

<Analysis of Concentration of Metal Impurities>

[0028] Quantitative analysis was carried out using an ICP mass spectrometer (Agilent 7900 ICP-MS manufactured by Agilent).

<Analysis of Concentration of Anionic Impurities>

[0029] Quantitative analysis was carried out using an automatic titrator (automatic titrator AT-510 manufactured by Kyoto Electronics Manufacturing Co., Ltd.) with 0.01 mol/L of sodium hydroxide. Analysis was carried out after 30 mL of methanol was added to 50 mL of carboxylic acid ester.

Example 1

[0030] As a pretreatment, each of an H-type strongly acidic cation-exchange resin (trade name: 15JS-HG DRY, manufactured by Organo Corporation) and a free base type weakly basic anion-exchange resin (trade name: B20-HG DRY, manufactured by Organo Corporation) was put into ethyl lactate separately and immersed therein for 1 hour or longer while being gently stirred suitably. After that, one FEP column having an inner diameter of 16 mm was filled with 10 ml of strongly acidic cation-exchange resin, and each of two FEP columns having an inner diameter of 16 mm was filled with 10 ml of weakly basic anion-exchange resin. After that, ethyl lactate was flowed through the weakly basic anion-exchange resin (I), the strongly acidic cation-exchange resin (II) and the weakly basic anion-exchange resin (III) in this order at 25 C. with SV=20 Hr.sup.1 as shown in FIG. 1. Respective concentrations of impurities after flowing through are shown in Table 1. From Table 1, it is understood that all the metal and anion contents described therein were highly removed.

Example 2

[0031] As a pretreatment, each of an H-type strongly acidic cation-exchange resin (trade name: 15JS-HG DRY, manufactured by Organo Corporation) and a free base type weakly basic anion-exchange resin (trade name: B20-HG DRY, manufactured by Organo Corporation) was put into methyl hydroxyisobutyrate separately and immersed therein for 1 hour or longer while being gently stirred suitably. After that, one FEP column having an inner diameter of 16 mm was filled with 10 ml of strongly acidic cation-exchange resin, and each of two FEP columns having an inner diameter of 16 mm was filled with 10 ml of weakly basic anion-exchange resin. After that, methyl hydroxyisobutyrate was flowed through the weakly basic anion-exchange resin (I), the strongly acidic cation-exchange resin (II) and the weakly basic anion-exchange resin (III) in this order at 25 C. with SV=20 Hr.sup.1 as shown in FIG. 1. Respective concentrations of impurities after flowing through are shown in Table 2. From Table 2, it is understood that all the metal and anion contents described therein were highly removed.

[0032] Further, the amount of methyl hydroxyisobutyrate flowed through was increased. The anionic impurity concentrations after flowing through are shown in Table 3. According to Table 3, the anion content was highly removed during time between when flowing through was started and when the amount was 2000 ml, but the anion content was increased after the amount reached 2500 ml.

Example 3

[0033] An H-type strongly acidic cation-exchange resin (trade name: 15JS-HG DRY, manufactured by Organo Corporation) and a free base type weakly basic anion-exchange resin (trade name: B20-HG DRY, manufactured by Organo Corporation) were pretreated with methyl hydroxyisobutyrate in a manner similar to that in Example 2. After that, one FEP column having an inner diameter of 16 mm was filled with 10 ml of strongly acidic cation-exchange resin, and another FEP column having an inner diameter of 16 mm was filled with 10 ml of weakly basic anion-exchange resin. After that, methyl hydroxyisobutyrate was flowed through the strongly acidic cation-exchange resin (II) and the weakly basic anion-exchange resin (III) in this order at 25 C. with SV=20 Hr.sup.1. Respective concentrations of impurities after flowing through are shown in Table 4. From Table 4, it is understood that all the metals described therein were highly removed. The anion content was highly removed during time between when flowing through was started and when the amount was 1500 ml, but the anion content was increased after the amount reached 1500 ml.

[0034] According to the results of Examples 2 and 3, the ability to remove the anion content can be more improved in Example 2 in which methyl hydroxyisobutyrate was flowed through the weakly basic anion-exchange resin (I) before it was flowed through the strongly acidic cation-exchange resin (II), and in addition, the life of the anion-exchange resin (III) can be improved.

Comparative Example 1

[0035] An H-type strongly acidic cation-exchange resin (trade name: 15JS-HG DRY, manufactured by Organo Corporation) was pretreated with ethyl lactate in a manner similar to that in Example 1. After that, an FEP column having an inner diameter of 16 mm was filled with 20 ml of strongly acidic cation-exchange resin, and after that, ethyl lactate was flowed therethrough at 25 C. with SV=20 Hr.sup.1. Respective concentrations of impurities after flowing through are shown in Table 5. From Table 5, it is understood that Ag, Au, Cr, Fe and Sn were hardly removed, and that it was impossible to remove the anionic impurities.

Comparative Example 2

[0036] A free base type weakly basic anion-exchange resin (trade name: B20-HG DRY, manufactured by Organo Corporation) was pretreated with ethyl lactate in a manner similar to that in Example 1. After that, an FEP column having an inner diameter of 16 mm was filled with 20 ml of free base type weakly basic anion-exchange resin, and after that, ethyl lactate was flowed therethrough at 25 C. with SV=20 Hr.sup.1. Respective concentrations of impurities after flowing through are shown in Table 6. From Table 6, it is understood that K and Na were hardly removed.

Comparative Example 3

[0037] 10 ml of an H-type strongly acidic cation-exchange resin (trade name: 15JS-HG DRY, manufactured by Organo Corporation) was mixed with 20 ml of a free base type weakly basic anion-exchange resin (trade name: B20-HG DRY, manufactured by Organo Corporation), and the mixture was pretreated with ethyl lactate in a manner similar to that in Example 1. After that, an FEP column having an inner diameter of 16 mm was filled with 30 ml of the mixture, and then ethyl lactate was flowed therethrough at 25 C. with SV=20 Hr.sup.1. Respective concentrations of impurities after flowing through are shown in Table 7. From Table 7, it is understood that Ca and Cr were insufficiently removed.

Comparative Example 4

[0038] An H-type strongly acidic cation-exchange resin (trade name: 15JS-HG DRY, manufactured by Organo Corporation) was pretreated with methyl hydroxyisobutyrate in a manner similar to that in Example 2. After that, an FEP column having an inner diameter of 16 mm was filled with 20 ml of strongly acidic cation-exchange resin, and after that, methyl hydroxyisobutyrate was flowed therethrough at 25 C. with SV=20 Respective concentrations of impurities after flowing through are shown in Table 8. From Table 8, it is understood that Ag, Au, Fe and Sn were hardly removed, and that it was impossible to remove the anionic impurities.

Comparative Example 5

[0039] A free base type weakly basic anion-exchange resin (trade name: B20-HG DRY, manufactured by Organo Corporation) was pretreated with methyl hydroxyisobutyrate in a manner similar to that in Example 2. After that, an FEP column having an inner diameter of 16 mm was filled with 20 ml of the free base type weakly basic anion-exchange resin, and after that, methyl hydroxyisobutyrate was flowed therethrough at 25 C. with SV=20 Hr.sup.1. Respective concentrations of impurities after flowing through are shown in Table 9. From Table 9, it is understood that K and Na were hardly removed.

Comparative Example 6

[0040] 10 ml of an H-type strongly acidic cation-exchange resin (trade name: 15JS-HG DRY, manufactured by Organo Corporation) was mixed with 20 ml of a free base type weakly basic anion-exchange resin (trade name: B20-HG DRY, manufactured by Organo Corporation), and the mixture was pretreated with methyl hydroxyisobutyrate in a manner similar to that in Example 2. After that, an FEP column having an inner diameter of 16 mm was filled with 30 ml of the mixture, and then methyl hydroxyisobutyrate was flowed therethrough at 25 C. with SV=20 Respective concentrations of impurities after flowing through are shown in Table 10. From Table 10, it is understood that Ca and Cr were insufficiently removed.

TABLE-US-00001 TABLE 1 Before After Metallic element flowing flowing content (unit: ppb) through through Ag 10 <1 Al 10 <1 Au 10 <1 Ca 10 <1 Cr 10 <1 Cu 10 <1 Fe 10 <1 K 10 <1 Mg 10 <1 Na 10 <1 Sn 10 <1 Zn 10 <1 Anionic impurities 30 <1 (unit: ppm)

TABLE-US-00002 TABLE 2 Before After Metallic element flowing flowing content (unit: ppb) through through Ag 10 <1 Al 10 <1 Au 10 <1 Ca 10 <1 Cr 10 <1 Cu 10 <1 Fe 10 <1 K 10 <1 Mg 10 <1 Na 10 <1 Sn 10 <1 Zn 10 <1 Anionic impurities 30 <1 (unit: ppm)

TABLE-US-00003 TABLE 3 Flow-through amount Before flowing 500 1000 1500 2000 2500 through ml ml ml ml ml Anionic impurities 30 <1 <1 <1 <1 10 (unit: ppm)

TABLE-US-00004 TABLE 4 Metallic element content (unit: ppb) Element Before flowing through After flowing through Ag 10 <1 Al 10 <1 Au 10 <1 Ca 10 <1 Cr 10 <1 Cu 10 <1 Fe 10 <1 K 10 <1 Mg 10 <1 Na 10 <1 Sn 10 <1 Zn 10 <1 Flow-through amount Before flowing 500 1000 1500 2000 2500 through ml ml ml ml ml Anionic impurities 30 <1 <1 <1 10 20 (unit: ppm) ppm ppm ppm ppm ppm ppm

TABLE-US-00005 TABLE 5 Before After Metallic element flowing flowing content (unit: ppb) through through Ag 10 10 Al 10 2 Au 10 10 Ca 10 2 Cr 10 10 Cu 10 <1 Fe 10 10 K 10 <1 Mg 10 <1 Na 10 <1 Sn 10 10 Zn 10 <1 Anionic impurities 30 110 (unit: ppm)

TABLE-US-00006 TABLE 6 Before After Metallic element flowing flowing content (unit: ppb) through through Ag 10 <1 Al 10 <1 Au 10 <1 Ca 10 <1 Cr 10 <1 Cu 10 <1 Fe 10 <1 K 10 8 Mg 10 <1 Na 10 8 Sn 10 <1 Zn 10 <1 Anionic impurities 30 <1 (unit: ppm)

TABLE-US-00007 TABLE 7 Before After Metallic element flowing flowing content (unit: ppb) through through Ag 10 <1 Al 10 <1 Au 10 <1 Ca 10 3 Cr 10 6 Cu 10 <1 Fe 10 <1 K 10 <1 Mg 10 <1 Na 10 <1 Sn 10 <1 Zn 10 <1 Anionic impurities 30 <1 (unit: ppm)

TABLE-US-00008 TABLE 8 Before After Metallic element flowing flowing content (unit: ppb) through through Ag 10 10 Al 10 2 Au 10 10 Ca 10 3 Cr 10 6 Cu 10 <1 Fe 10 10 K 10 <1 Mg 10 <1 Na 10 <1 Sn 10 10 Zn 10 <1 Anionic impurities 30 120 (unit: ppm)

TABLE-US-00009 TABLE 9 Before After Metallic element flowing flowing content (unit: ppb) through through Ag 10 <1 Al 10 <1 Au 10 <1 Ca 10 <1 Cr 10 <1 Cu 10 <1 Fe 10 <1 K 10 7 Mg 10 <1 Na 10 7 Sn 10 <1 Zn 10 <1 Anionic impurities 30 <1 (unit: ppm)

TABLE-US-00010 TABLE 10 Before After Metallic element flowing flowing content (unit: ppb) through through Ag 10 <1 Al 10 <1 Au 10 <1 Ca 10 2 Cr 10 5 Cu 10 <1 Fe 10 <1 K 10 <1 Mg 10 <1 Na 10 <1 Sn 10 <1 Zn 10 <1 Anionic impurities 30 <1 (unit: ppm)

INDUSTRIAL APPLICABILITY

[0041] In the high-purity carboxylic acid ester provided by the present invention, metal impurities and anionic impurities are highly reduced, and therefore it is industrially useful. The carboxylic acid ester is a compound useful for a wide range of applications such as synthetic raw materials, cleaning agents for electronic components and solvents for paints, adhesives and the like, or as a treatment agent for cleaning of a semiconductor substrate, etching, development of a photoresist and the like in the production of integrated circuits and large-scale integrated circuits.