High-purity carboxylic acid ester and method for producing same

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−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−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−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.