TWI909025B - Method for refining hydrolyzable organic solvent, and method for producing resin for refining hydrolyzable organic solvent - Google Patents

Abstract

The invention provides a method for refining a hydrolyzable organic solvent that suppresses the production of acid while enabling a reduction in the metal impurity concentration within the hydrolyzable organic solvent. The method for refining a hydrolyzable organic solvent has a refining step of bringing the hydrolyzable organic solvent into contact with a cation exchange resin optionally mixed with a chelating resin, wherein the volume fraction of the cation exchange resin relative within the total volume of the cation exchange resin and the optional chelating resin is within a range from 10 to 100%.

Description

Methods for refining hydrolyzable organic solvents and methods for manufacturing resins used in the refining of hydrolyzable organic solvents.

This invention relates to a method for refining hydrolyzable organic solvents and a method for manufacturing resins used in the refining of hydrolyzable organic solvents.

Semiconductors are manufactured through hundreds of complex steps. The linewidth of a semiconductor is determined by the photoresist process. The photoresist process includes: coating photoresist onto a silicon wafer, exposure by passing short-wavelength light through a photomask from a light source, developing the photomask, etching the areas without photoresist, and peeling off the photoresist. The photoresist coated on the wafer is a solution made by dissolving an acid generator, resin solution, and additives in an organic solvent. This organic solvent uses ester-based organic solvents such as PGMEA (propylene glycol monomethyl ether acetate) and ethyl lactate, as well as PGME (propylene glycol monomethyl ether) and cyclohexanone as main components.

In recent years, the processing dimensions of semiconductor linewidths have become increasingly smaller. This miniaturization of semiconductor linewidths has driven the miniaturization and high-performance technologies of IT equipment. As semiconductor linewidths decrease, the light sources used in the exposure process have expanded from gamma rays and i-rays to include shorter wavelengths such as ArF, EUV, and X-rays. The impurity levels in the organic solvents used around the photoresist coating are also being reduced. Among the impurities contained in organic solvents, especially the presence of large amounts of residual metal elements, these metal elements can adhere to the wafer, leading to a decrease in semiconductor performance. Therefore, metal elements must be included in the reduction list.

On the other hand, it is known that ester-based organic solvents such as PGMEA used in semiconductor manufacturing undergo hydrolysis upon contact with water, acids, and alkalis, thereby generating acids. Therefore, some researchers have proposed using distillation and chelation resins in the refining of ester-based organic solvents as methods to remove metallic impurities without generating acids.

Patent 1 describes a method in which chelated resin is cleaned with deionized water, an inorganic acid solution, and optionally with ammonium hydroxide solution, followed by cleaning with an organic solvent. The resulting mixture is then heated and filtered to reduce metal ions in the photoresist. However, this method is particularly ineffective at removing Fe.

Patent document 2 describes a method in which the flow rate (SV value) is reduced to below 10 ^h⁻¹ , allowing a photoresist film to be formed by passing a resin solution through a filter substrate on which ion exchange groups and/or chelating groups are fixed to a polyolefin-based nonwoven fabric. However, patent document 2 only describes Na concentration as an impurity concentration. According to the inventor's research, the removal of heavy metals such as Fe and Cr is poor compared to the use of chelating resins.

Patent 3 describes a method for removing metallic impurities from treatment solutions such as PGMEA using chelating resins that have already reduced metallic impurity content with inorganic acid solutions. However, further research by the inventors of this patent has revealed that, depending on the type of treatment solution being refined, it may sometimes be impossible to completely remove heavy metals such as Fe and Cr. [Prior Art Documents] [Patent Documents]

Patent Document 1: Japanese Patent Application Publication No. 2000-501201 Patent Document 2: Japanese Patent Application Publication No. 2013-061426 Patent Document 3: Japanese Patent Application Publication No. 2019-141800

[The problem the invention aims to solve]

Therefore, the purpose of this invention is to provide a method for manufacturing a resin for refining hydrolyzable organic solvents, which can inhibit acid formation and reduce the concentration of metallic impurities in the hydrolyzable organic solvent; and to provide a method for refining hydrolyzable organic solvents using this resin. [Means for Solving the Problem]

In view of the above problems, the inventors of this case have conducted detailed research and found that by using cationic exchange resins that are arbitrarily mixed with chelating resins, it is possible to inhibit the production of acid by hydrolytic organic solvents and reduce the amount of metals that cannot be adequately removed by chelating resins alone, thereby completing this invention.

That is, the method for refining the hydrolyzable organic solvent of the present invention is characterized by having: a refining step in which a cationic exchange resin, which is arbitrarily mixed with chelating resin, is brought into contact with the hydrolyzable organic solvent for refining; the volume ratio of the cationic exchange resin is 10 to 100% relative to the total amount of the cationic exchange resin and any chelating resin.

Furthermore, the method for manufacturing the resin for refining hydrolyzable organic solvents of this invention is characterized by the step of randomly mixing a chelating resin into a cation exchange resin; the volume percentage of the cation exchange resin relative to the total amount of the cation exchange resin and any amount of the chelating resin is 10-100%. [Effects of the Invention]

According to the present invention, a method for manufacturing a resin for refining hydrolyzable organic solvents is provided, which can inhibit acid formation and reduce the concentration of metallic impurities in the hydrolyzable organic solvent; and a method for refining hydrolyzable organic solvents using the resin is provided.

The method for manufacturing a resin for refining a hydrolyzable organic solvent of the present invention includes a step of arbitrarily mixing a chelating resin into a cation exchange resin. Furthermore, in the case where only the cation exchange resin is used without using a chelating resin, this step can also be considered a step for preparing the cation exchange resin. Additionally, the method for refining a hydrolyzable organic solvent of the present invention includes a refining step in which the cation exchange resin, in which chelating resin is arbitrarily mixed, is contacted with a hydrolyzable organic solvent for refining. The volume percentage of the cation exchange resin is 10-100% relative to the total amount of the cation exchange resin and any chelate resin.

(Hydrolyzable Organic Solvents) The hydrolyzable organic solvent used as the refining target solution in this invention is an ester-based organic solvent that produces acid upon hydrolysis. Alternatively, the refining target solution in this invention can also be a mixed solvent composed of at least two organic solvents containing ester-based organic solvents. The refining target solution is not particularly limited, but examples include: ester-based organic solvents such as PGMEA (propylene glycol monomethyl ether acetate), ethylene glycol monoethyl ether acetate, ethyl-3-ethoxypropyl acetate, ethyl lactate, butyl lactate, butyl acetate, and isoamyl acetate; and mixed solvents of these ester-based organic solvents with PGME (propylene glycol monomethyl ether), cyclohexanone, etc. Among these, PGMEA or a PGMEA/PGME mixed solvent is preferred. The proportion of PGMEA in the solvent mixture of PGMEA/PGME is not particularly limited and can be adjusted appropriately according to the purpose.

From the perspective of inhibiting hydrolysis and ensuring the stability of metal refining performance, the moisture concentration of the hydrolyzable organic solvent (before purification) used in this invention should preferably be 20~10000 mg/L. The upper limit of this moisture concentration should preferably be low, more preferably 5000 mg/L, and even more preferably 1000 mg/L. Furthermore, the moisture concentration can be measured, for example, using a Carrfeldt-Jackson volumetric moisture meter (trade name: Aquacounter AQ-2200, manufactured by Hiranuma Sangyo Co., Ltd.) using the Carrfeldt-Jackson method.

(Cat exchange resins) Cationic exchange resins are, for example, copolymers with a three-dimensional network structure obtained by introducing functional groups into styrene and divinylbenzene (DVB) in the presence of a catalyst and a dispersant. Examples of cationic exchange resins used in this invention include strongly acidic cationic exchange resins with sulfonic acid groups ( _-SO₃H ) and weakly acidic cationic exchange resins with carboxylic acid groups (-COOH). Furthermore, cation exchange resins can be gel-type resins with small, transparent pore diameters, or macroreticular (MR) or macroporous (also known as porous or high-porous) types with large pore diameters and wide gaps. In this invention, from the viewpoint of metal removal, a strongly acidic cation exchange resin is preferable. Among these, from the viewpoint of balancing acid formation inhibition and metal removal performance, an MR-type strongly acidic cation exchange resin is preferable. Moreover, from the viewpoint of more effectively inhibiting acid formation, a highly cross-linked gel-type strongly acidic cation exchange resin is preferable. In addition, the so-called highly crosslinked gel-type strong acid cation exchange resin specifically refers to gel-type strong acid cation exchange resin with a crosslinking degree of 16% to 24%.

The volume percentage of the cation exchange resin relative to the total amount of the cation exchange resin and any chelating resins described below is 10-100%, preferably 20-100%. Here, 100% means using only the cation exchange resin. According to the purification method of this invention, even when using only the cation exchange resin, acid formation can be suppressed and metallic impurities in the purified solution can be reduced. From the viewpoint of more effectively suppressing acid formation, it is preferable to use the cation exchange resin and chelating resin in a mixed bed or a combined bed. In this case, the volume ratio of cation exchange resin should be 10% to 50%, more preferably 10% to 33%, relative to the total amount of cation exchange resin and chelate resin.

Examples of cation exchange resins used in this invention include: AMBERLITE IRN99H (a gel-type, strongly acidic cation exchange resin, trade name, manufactured by DuPont), AMBERLITE CR99 K/350, TAPTEC HCRS Na (both gel-type, strongly acidic cation exchange resins, trade name, manufactured by DuPont), AMBERJET 1060H (a gel-type, strongly acidic cation exchange resin, trade name, manufactured by Orlucan), and ORLITE (registered trademark). Examples of cation exchange resins include DS-1 (gel-type strong acid cation exchange resin, trade name, manufactured by Orlucano Co., Ltd.), ORLITE (registered trademark), and DS-4 (MR type strong acid cation exchange resin, trade name, manufactured by Orlucano Co., Ltd.), but are not limited to these. From the perspective of metal removal, the ionic form of the cation exchange resin should preferably be hydrogen ion (H-form). Furthermore, when using other ionic forms (e.g., sodium ion, potassium ion, etc.), it is advisable to convert them to H-form beforehand using conventional methods.

(Chelating Resin) In this invention, chelating resins can be arbitrarily mixed into the cation exchange resin. When mixing chelating resins, the cation exchange resin and the chelating resin can be in a mixed bed or a multi-bed. The effects of this invention can be achieved in either case. A chelating resin is a resin having a functional group (chelating group) capable of forming a chelate (wedge) with metal ions. This functional group is not particularly limited; it is only necessary to have a functional group capable of forming a chelate (wedge) with metal ions. Examples of such functional groups include: aminomethyl phosphate, iminodiacetic acid, thiol, and polyamine. From the perspective of selectivity for various metal species, chelating resins preferably possess aminomethylphosphate or iminodiacetic acid groups as functional groups.

The ionic form of chelating resins should preferably be H-shaped. Examples of chelating resins include: AMBERSEP (registered trademark) IRC747UPS (trade name, manufactured by DuPont, chelating group: aminomethyl phosphate), AMBERSEP (registered trademark) IRC748 (trade name, manufactured by DuPont, chelating group: iminodiacetic acid), ORLITE (registered trademark) DS-21 (trade name, manufactured by Orlucano Corporation, chelating group: aminomethyl phosphate), ORLITE (registered trademark) DS-22 (trade name, manufactured by Orlucano Corporation, chelating group: iminodiacetic acid), and DIAION (registered trademark). CR11 (trade name, manufactured by Mitsubishi Chemical Co., Ltd., chelating group: iminodiacetic acid group), S930 (trade name, manufactured by Purolite Co., Ltd., chelating group: iminodiacetic acid group), S950 (trade name, manufactured by Purolite Co., Ltd., chelating group: aminophosphate group), etc., but not limited to these. Furthermore, if the ionic form of the above resin is sodium ion (Na form), conventional methods can be used to convert the ionic form from Na form to H form before use.

The chelating resin used in this invention is in hydrogen ion form, and the total metallic impurities dissolved when hydrochloric acid at a concentration of 3% by mass is passed through the chelating resin in a volume ratio of 25 times is preferably less than 5 μg/mL-R. Commercially available products can also be used as the chelating resin. Here, "volume ratio of 25 times" refers to passing hydrochloric acid in a volume 25 times the volume of the chelating resin. The unit "/mL-R" refers to "the volume of the chelating resin in a saturated equilibrium state per 1 mL". Furthermore, the so-called saturated equilibrium state refers to the state in which the chelating resin is exposed to an atmosphere at 25°C and 100% relative humidity for more than 30 minutes, thereby reaching a saturated state. The phrase "passing hydrochloric acid through" includes not only passing hydrochloric acid through the chelating resin but also impregnating the chelating resin with hydrochloric acid. The total metallic impurities (μg/mL-R) per 1 mL of chelating resin can be calculated from the total dissolved metallic impurities (μg/L), the volume of the dissolution solution (L), and the volume of the chelating resin (mL) using the following formula: Total metallic impurities (μg/mL-R) = (Total metallic impurities (μg/L) × Volume of dissolution solution (L)) / Volume of chelating resin (mL)

Furthermore, chelated resins with a total metal impurity content of 5 μg/mL-R or less can be obtained, for example, by the method described in Patent 3. That is, a method for purifying the chelated resin by contacting it with an inorganic acid solution containing metal impurities of 1 mg/L or less and a concentration of 5% by mass or more. This reduces the total metal impurities (especially Na, Ca, Mg, Fe, etc.) dissolved when hydrochloric acid at a concentration of 3% by mass is passed through the chelated resin in a volume ratio of 25:1 to below 5 μg/mL-R. By using chelated resins with reduced metal impurity content for the purification of hydrolyzable organic solvents, high-purity hydrolyzable organic solvents containing even fewer metal impurities can be obtained. The inorganic acid solution can be hydrochloric acid, sulfuric acid, nitric acid, etc. Alternatively, when using a Na-form chelating resin for the above purification process, the ionic form is converted to the H-form.

(Anion Exchange Resin) As described above, in this invention, cation exchange resins and chelating resins can be mixed arbitrarily for use, and anion exchange resins can also be further combined. By using anion exchange resins, acid formation can be reliably suppressed. Therefore, even when only cation exchange resins are used, or in cases where there is concern about the formation of other acids, acid formation can be further suppressed by combining anion exchange resins. When using anion exchange resins, the amount of the anion exchange resin used, relative to the total amount of the cation exchange resin and any chelating resin, can be, for example, 0.1 to 100% by volume.

Examples of anion exchange resins include: strongly basic anion exchange resins having fourth-order ammonium groups and weakly basic anion exchange resins having first- to third-order amino groups. Examples of anion exchange resins include, for example, ORLITE (registered trademark) DS-2 (gel-type strongly basic anion exchange resin, trade name, manufactured by ORLITE Co., Ltd.), DS-5 (MR-type strongly basic anion exchange resin, trade name, manufactured by ORLITE Co., Ltd.), and DS-6 (MR-type weakly basic anion exchange resin, trade name, manufactured by ORLITE Co., Ltd.), but are not limited to these. Among these, MR-type anion exchange resins are preferred.

Before being used to purify hydrolyzable organic solvents, the cation exchange resins, any chelate resins, and any anion exchange resins (hereinafter collectively referred to as "ion exchange resins") may be subjected to a pretreatment to inhibit the leaching of water from the resins, depending on the requirements. That is, in the purification method of the present invention, a pretreatment step may be included before the purification step, which is a pretreatment of the cation exchange resins, any chelate resins, and any anion exchange resins to inhibit the leaching of water from the resins.

Pretreatment methods include, for example, contacting the hydrolyzable organic solvent of the purified object with an ion exchange resin, or contacting the ion exchange resin with a pretreatment organic solvent whose relative permittivity at 25°C is greater than that of the hydrolyzable organic solvent of the purified object. Specifically, a method can be described as follows: In a column filled with ion exchange resin used prior to purification, the hydrolyzable organic solvent of the purified object is introduced and continuously passed through until the water concentration in the solvent is equal at the inlet and outlet of the column. Another method is to pass a pretreatment organic solvent (with a relative permittivity greater than that of the target substance at 25°C) through a column filled with an ion-exchange resin used for refining, and continue passing the solvent until the water concentration in the solvent is the same at the inlet and outlet of the column. Alternatively, after passing the pretreatment organic solvent, the hydrolyzable organic solvent of the target substance can be passed through until the water concentration in the solvent is the same at the inlet and outlet of the column. The pretreatment organic solvent should preferably be an alcohol such as methanol or ethanol with a relative permittivity of 20 or higher at 25°C.

Furthermore, other pretreatment methods to suppress the leaching of moisture from the resin include: placing a heat-resistant container filled with ion-exchange resin inside a dryer and subjecting it to heating (drying) for several hours. The drying conditions can be set appropriately between 50°C and 120°C, and between 1 hour and 24 hours, depending on the type of ion-exchange resin. By performing this treatment, the moisture content in the ion-exchange resin can be reduced to below 10% by mass. The drying method can be any of atmospheric pressure, reduced pressure, or vacuum drying; reduced pressure or vacuum drying is preferred from the viewpoint of short drying time and high efficiency. Additionally, the moisture content of the ion-exchange resin can be calculated using the following formula. Moisture content (mass %) = ((mass of resin treated with heat in a dryer (g) - mass of resin completely dried using a heat-drying moisture meter (g)) / mass of resin treated with heat in a dryer (g)) × 100

Here, in the above formula, the resin that has undergone heat treatment in a dryer can be obtained by heat treatment of the resin as described above (moisture content less than 10% by mass). Then, before measuring the resin that has undergone heat treatment in a dryer using a heated drying moisture meter, it should be stored and moved in a manner that prevents moisture from the air from contaminating it. Then, the resin is placed on the heated drying moisture meter and further dried completely at 105°C for several minutes to several tens of minutes, thereby obtaining resin completely dried by the heated drying moisture meter. For example, an A&D MX-50 (trade name) heated drying moisture meter can be used. Furthermore, to improve the accuracy of the measurement, at least 5g of the undried resin should be used for measurement.

There are no particular limitations on the method of contacting the hydrolyzable organic solvent with the ion exchange resin; examples include batch processing methods and continuous flow processing methods using a column. From the perspective of operability and efficiency, continuous flow processing methods are preferable.

In continuous flow processing methods, ion exchange resin is packed into a purification column such as a tubular column. The height of the resin packing layer in the purification column is not particularly limited, and can be, for example, 100~1500 mm. Then, a hydrolyzable organic solvent of 2~100 BV is introduced, for example, at a space velocity ( ^SV ) of 2~20. Here, BV (Bed volume) represents the flow rate multiple of the introduced solvent relative to the amount of resin. From the viewpoint of metal removal, the hydrolyzable organic solvent flow is preferably carried out at SV2~20, and more preferably at SV5~10. The flow direction can be either downward or upward. By carrying out the flow in this way, metallic impurities in the hydrolyzable organic solvent can be adsorbed onto the ion exchange resin and removed.

Next, the batch processing method will be explained. First, fill the reaction tank equipped with a mixer with ion exchange resin. Then, fill the reaction tank with hydrolyzable organic solvent. The volume ratio is not particularly limited, but it is advisable to use 2 to 200 parts organic solvent per 1 part resin. After that, let it stand for, for example, about 0.5 to 24 hours. After standing, run the mixer to mix the resin and organic solvent evenly. The stirring speed and stirring time can be appropriately determined according to the size of the reaction tank and the throughput. After stirring, perform filtration to separate the resin from the hydrolyzable organic solvent, thereby removing metallic impurities and obtaining a refined hydrolyzable organic solvent.

In addition, regarding ion exchange resins, if the above-mentioned pretreatment to inhibit the leaching of water from the resin is performed before refining hydrolyzable organic solvents, the process of contacting the ion exchange resin with the hydrolyzable organic solvent for refining can be carried out directly using containers such as columns used in the pretreatment.

The purification method of this invention mainly involves continuous operation for the purification of hydrolyzable organic solvents. That is, during the purification step, the liquid flow is continuously maintained from the start of the purification process (liquid flow) until the end of the purification process. However, the purification of hydrolyzable organic solvents can also be carried out intermittently. In the case of intermittent operation for the purification of hydrolyzable organic solvents, within the experimental system, the organic solvent may undergo hydrolysis due to external moisture or functional groups from the resin, resulting in the production of water and acid. Therefore, in the case of intermittent operation, the refining method of the present invention should have a discharge step, which involves, after the start of the refining step, discharging the hydrolyzable organic solvent dissolved from the outlet of the refining tower filled with cation exchange resin, any chelate resin and any anion exchange resin at fixed intervals to a storage tank for storing the refined hydrolyzable organic solvent. For example, if the hydrolyzable organic solvent is stopped for more than 30 minutes after the start of the refining step, a discharge step can be performed to discharge at least 0.5 BV of the hydrolyzable organic solvent dissolved from the outlet of the refining tower into a storage tank. This discharge is done before the refining step resumes. By implementing a discharge step, the amount of water and acid generated during the shutdown process can be reduced. The discharge amount (the amount of hydrolyzable organic solvent discharged outside the system) in the discharge step can also be preset based on the shutdown time, the water content, acid concentration, and resistivity of the hydrolyzable organic solvent at the outlet of the refining tower. Alternatively, it can be set up online to automatically stop the emission step and switch to the refining step when the preset resistivity is reached. In addition, the above emission step can also be implemented as needed when refining hydrolyzable organic solvents in continuous operation.

According to the purification method of this invention, by suppressing the formation of acid from the hydrolyzable organic solvent, the pH of the hydrolyzable organic solvent after the purification step can be maintained near neutral. Specifically, the pH of the hydrolyzable organic solvent after the purification step can be 5 to 7. However, depending on the type of hydrolyzable organic solvent, there are also cases where the pH is, for example, below 4.

According to the refining method of this invention, the concentration of each metal in the hydrolyzable organic solvent can be reduced by 70% by mass or more, preferably 80% by mass or more, during the refining step. Furthermore, metallic impurities contained in the hydrolyzable organic solvent can be listed as, for example: Li, Na, Mg, Al, K, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Sr, Ag, Cd, Sn, Ba, Pb, etc.

The present invention is illustrated below by way of examples, but the present invention is not limited to these examples. [Examples]

The methods for measuring metal concentration, acetic acid concentration, and moisture concentration are as follows.

(Metal Concentration) Metal concentration (ng/L) was measured using an Agilent 8900 three-stage quadrupole ICP-MS (trade name, manufactured by Agilent Technologies, Inc.).

(Acetic Acid Concentration) Acetic acid concentration (ppm) was measured using a capillary electrophoresis system (trade name: Agilent 7100, manufactured by Otsuka Electronics Co., Ltd.).

(Moisture Concentration) Moisture concentration was measured using a Carrfeldt-Jackson volumetric moisture meter (trade name: Aquacounter AQ-2200, manufactured by Hiranuma Sangyo Co., Ltd.) according to the Carrfeldt-Jackson method.

(Ion Exchange Resins) Details of the various ion exchange resins used in the following examples are as follows. • ORLITE (Registered Trademark) DS-21 (Trade Name, manufactured by ORLITE AG): Chelating resin, Chelating group: Aminomethylphosphate group • ORLITE (Registered Trademark) DS-4 (Trade Name, manufactured by ORLITE AG): MR type strong acidic cation exchange resin, Ion exchange group: Sulfonic acid group • ORLITE (Registered Trademark) DS-1 (Trade Name, manufactured by ORLITE AG): Gel type strong acidic cation exchange resin, Ion exchange group: Sulfonic acid group, Crosslinking degree: Standard • AMBERLITE (Registered Trademark) CR99 K/350 (trade name, manufactured by DuPont): Gel-type strong acid cation exchange resin, crosslinking degree: low • AMBERLITE (registered trademark) IRN99H (trade name, manufactured by DuPont): Gel-type strong acid cation exchange resin, crosslinking degree: high • ORLITE (registered trademark) DS-6 (trade name, manufactured by Orlucan Corporation): MR-type weakly basic anion exchange resin

[Comparative Example 1, Examples 1-5: Comparison of Mixed Bed Ratios] (PGA Refining) In a PFA resin column (inner diameter: 16 mm, height: 300 mm), the mixed bed ratios (volume ratios) of the cation exchange resins shown in Table 1 were used to fill a total of 36 mL of ORLITE (registered trademark) DS-21 (a chelating resin) and ORLITE (registered trademark) DS-4 (an MR-type strong acid cation exchange resin). Furthermore, it was confirmed that when 3% by mass hydrochloric acid was passed through the above chelating resins at a volume ratio of 25:1, the total dissolved metallic impurities were 5 μg/mL-R or less. As a pretreatment, PGMEA (trade name: PM Thinner, manufactured by Tokyo Ohka Kogyo Co., Ltd.) was introduced through SV5 until the moisture concentration in the PGMEA was the same at the column inlet and outlet, thus removing moisture from the resin. It was also confirmed that introducing methanol, which has a higher relative permittivity than PGMEA at 25°C, instead of PGMEA in the above pretreatment process could remove moisture from the resin. Then, 20 BV of PGMEA was introduced through SV5 into the pretreated resin for a purification step. The unrefined PGMEA (stock solution) and the refined PGMEA from the column outlet were collected, and the Cr, acetic acid, and moisture concentrations were measured. The results are shown in Table 1. Furthermore, regarding the acetic acid produced, levels up to 5 mg/L (absolute value) were within the measurement error range, meaning that acetic acid was essentially not produced. Also, the concentrations of Cr and acetic acid in the stock solutions varied in each example; this is due to differences in the batch numbers of the stock solutions.

[Table 1] Comparative example 1 Implementation Example 1 Implementation Example 2 Implementation Example 3 Implementation Example 4 Implementation Example 5 Mixed bed ratio of cation exchange resins 0% 10% 20% 25% 33% 100% Cr Concentration of stock solution (ng/L) 40 89 43 59 70 65 Refined concentration (ng/L) 18.0 14.4 4.6 4.7 3.9 2.0 Removal rate (%) 55 84 89 92 94 98 Acetic acid Concentration of stock solution (mg/L) 37 20 20 15 13 12 Refined concentration (mg/L) 34 twenty one twenty two 19 18 twenty two Acetic acid produced (mg/L) without 1 2 4 5 10 Moisture Concentration of stock solution (mg/L) 37 79 43 55 55 55 Refined concentration (mg/L) 47 74 33 56 47 76

As shown in Table 1, in Examples 1-5 where the mixed bed ratio of cation exchange resins was 10%~100%, the Cr concentration in the refined PGMEA was less than 15 ng/L, which suppressed the formation of acetic acid and removed metals with good efficiency. In particular, in Examples 1-4 where chelating resins and cation exchange resins were used in a mixed bed, the formation of acetic acid was largely suppressed. On the other hand, in Comparative Example 1 where the mixed bed ratio of cation exchange resins was 0%, i.e., only chelating resins were used, the Cr removal rate in the refined PGMEA was 55%, indicating that the metals were not sufficiently removed.

[Examples 6-7: Comparison of Cr removal performance based on the type of strongly acidic cationic exchange resin] As a strongly acidic cationic exchange resin mixed with chelating resin (mixed bed ratio: 25 volume%), ORLITE (registered trademark) DS-1 (gel-type strongly acidic cationic exchange resin, crosslinking degree: standard) and AMBERLITE (registered trademark) CR99 K/350 (gel-type strongly acidic cationic exchange resin, crosslinking degree: low, formed by converting K form to H form) were used respectively. Otherwise, PGMEA was purified using the same method as in Example 3. Samples of PGMEA (stock solution) before purification and PGMEA at the column outlet after purification were taken, and Cr and moisture concentrations were measured. The results are shown in Table 2, along with those of Example 3.

[Table 2] Implementation Example 3 Implementation Example 6 Implementation Example 7 Strongly acidic cation exchange resin DS-4 (MR type) DS-1 (Gel Type) CR99 K/350 (Gel Type) Cr Concentration of stock solution (ng/L) 59 65 59 Refined concentration (ng/L) 4.7 12.6 14.5 Removal rate (%) 92 81 75 Moisture Concentration of stock solution (mg/L) 55 59 59 Refined concentration (mg/L) 56 71 58

As shown in Table 2, it can be seen that DS-4, a strong acidic cation exchange resin of the MR type, has particularly good metal removal performance compared to DS-1, a gel-type strong acidic cation exchange resin, and CR99 K/350, a gel-type small particle size strong acidic cation exchange resin.

[Examples 8-10: Comparison of Acetic Acid Production Based on Different Crosslinking Degrees] As a gel-type strongly acidic cation exchange resin (mixed bed ratio: 25 volume%) mixed with chelating resins, AMBERLITE (registered trademark) IRN99H (high crosslinking degree), ORLITE (registered trademark) DS-1 (standard crosslinking degree), and AMBERLITE (registered trademark) CR99 K/350 (low crosslinking degree, K-form converted to H-form) were used. Otherwise, PGMEA was purified using the same method as in Example 3. Samples of PGMEA (stock solution) before purification and PGMEA at the column outlet after purification were taken, and the acetic acid and moisture concentrations were measured. The results are shown in Table 3.

[Table 3] Implementation Example 8 Implementation Example 9 Implementation Example 10 Gel-type strongly acidic cationic exchange resin IRN99H (Cross-connectivity: High) DS-1 (Interconnection Degree: Standard) CR99 K/350 (Cross-linkage: Low) Acetic acid Concentration of stock solution (mg/L) 15 13 18 Refined concentration (mg/L) 14 twenty three 29 Acetic acid produced (mg/L) without 10 11 Moisture Concentration of stock solution (mg/L) 58 59 59 Refined concentration (mg/L) 83 71 58

As shown in Table 3, it can be seen that the use of highly crosslinked resins in gel-type strongly acidic cationic exchange resins can effectively inhibit the production of acetic acid.

[Reference Example 1: Reducing Acetic Acidity Using Anion Exchange Resins] As the resin, only ORLITE (registered trademark) DS-6, a weakly basic anion exchange resin of the MR type, was used. Otherwise, PGMEA was purified using the same method as in Example 3. Samples of PGMEA (stock solution) before purification and PGMEA at the column outlet after purification were taken, and the acetic acid concentration was measured. The results are shown in Table 4.

[Table 4] Reference Example 1 Cationic exchange resin DS-6 (weakly alkaline) Acetic acid Concentration of stock solution (mg/L) 15 Refined concentration (mg/L) <5 Acetic acid produced (mg/L) without

As shown in Table 4, it is evident that acetic acid contained in the original solution can be removed by using anion exchange resin. Therefore, it is understood that by further combining the cation exchange resin of the present invention with any chelating resin and using anion exchange resin, the purification of hydrolytic organic solvents that effectively inhibit the production of acetic acid can be achieved.

Claims (10)

A method for refining a hydrolyzable organic solvent includes a refining step in which a cationic exchange resin, which is randomly mixed with a chelating resin, is contacted with a hydrolyzable organic solvent for refining; the volume ratio of the cationic exchange resin is 10-50% relative to the total amount of the cationic exchange resin and any amount of the chelating resin. For example, the purification method of the hydrolyzable organic solvent in claim 1, wherein the water concentration in the hydrolyzable organic solvent before purification is 20~10000 mg/L. The method for refining the hydrolyzable organic solvent as claimed in claim 1 or 2, wherein prior to the refining step, there is a pretreatment step, which is a pretreatment of the cation exchange resin and any chelate resin to inhibit the leaching of water from the resin; the pretreatment is a method of making the relative permittivity of the cation exchange resin and any chelate resin at 25°C greater than that of the organic solvent used for pretreatment of the hydrolyzable organic solvent, or a method of reducing the moisture content of the cation exchange resin and any chelate resin to less than 10% by mass using a dryer. The method for refining the hydrolyzable organic solvent as claimed in claim 1 or 2, wherein an anion exchange resin is used in further combination with the cation exchange resin and any of the chelate resin. The method for refining hydrolyzable organic solvents as claimed in claim 1 or 2, wherein the cation exchange resin is a strongly acidic cation exchange resin. For example, the method for refining hydrolyzable organic solvents in claim 5, wherein the strong acid cation exchange resin is an MR type strong acid cation exchange resin. For example, the method for refining hydrolyzable organic solvents in claim 5, wherein the strong acid cation exchange resin is a gel-type strong acid cation exchange resin with a crosslinking degree of 16% to 24%. For example, the purification method of the hydrolyzable organic solvent in claim 1 or 2, wherein in the purification step, the concentration of each metal in the hydrolyzable organic solvent is reduced by more than 80% by mass. The purification method for the hydrolyzable organic solvent as described in claim 1 or 2 includes a discharge step in which, after the purification step begins, the hydrolyzable organic solvent dissolved from the outlet of the purification tower filled with the cation exchange resin, any of the chelate resin and any of the anion exchange resin is discharged at fixed intervals to a storage tank for storing the purified hydrolyzable organic solvent. A method for manufacturing a resin for refining hydrolyzable organic solvents, characterized by comprising a step of arbitrarily mixing a cation exchange resin and a chelate resin, wherein the volume ratio of the cation exchange resin is 10-50% relative to the total amount of the cation exchange resin and the chelate resin.