Method for producing cation exchange resin and method for purifying organic acid solution

Abstract

Provided is a method for producing a cation exchange resin with which the content of metal impurities in the cation exchange resin is reduced and metal elution is reduced even when the cation exchange resin is used in the purification of an organic acid solution. A method for producing a cation exchange resin, the method comprising: a first regeneration step in which a cation exchange resin (B) is obtained by bringing an inorganic acid solution having a metal impurity amount of 1 mg / L or less and a concentration of 5 mass% or more into contact with a cation exchange resin (A); a purification step in which an organic acid solution having a metal impurity amount of 2 mg / L or less and a concentration of 3 mass% or more is brought into contact with the cation exchange resin (B), thereby purifying the organic acid solution; and a second regeneration step in which a cation exchange resin (C) is obtained by bringing an inorganic acid solution having a metal impurity amount of 1 mg / L or less and a concentration of 5 mass% or more into contact with the cation exchange resin (B) after the purification step.

Description

Technical Field

[0001] The present invention relates to a method for producing a cation exchange resin and a method for highly purifying an organic acid solution using the cation exchange resin. Background Art

[0002] In the semiconductor manufacturing process, various high-purity liquids are used, not limited to ultrapure water, and it is strongly necessary to reduce the metal impurities in the various liquids. The removal of metal impurities in the various liquids can use ion exchange resins (cation exchange resins, anion exchange resins, chelating resins). Therefore, it is required to reduce the dissolution from the purified ion exchange resins themselves used for various liquids.

[0003] As a method for reducing the metal impurity content of ion exchange resin, a method of contacting a high-purity inorganic acid solution having a metal impurity content of 1 mg / L or less with the ion exchange resin has been proposed (Patent Document 1). In addition, a method of refining the ion exchange resin using an inorganic acid aqueous solution containing a chelating agent such as ethylenediaminetetraacetic acid has been proposed (Patent Document 2).

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Publication No. 2007-117781

[0007] Patent Document 2: Japanese Patent Application Publication No. 2010-234339 Summary of the invention

[0008] Technical problem to be solved by the invention

[0009] In particular, when an ion exchange resin is used to purify an organic acid solution, due to the metal dissolution and extraction effect of the organic acid solution itself as the object of purification (processed liquid), there is a tendency for the amount of metal leaching from the ion exchange resin to increase. Therefore, even if the organic acid solution is purified by the ion exchange resin purified by the method described in the above patent document, there is a situation where a trace amount of metal leaching becomes a problem. In addition, in the purification of the organic acid solution, the life of the ion exchange resin used is short, and the exchange frequency of the ion exchange resin becomes high, thereby increasing the cost.

[0010] Therefore, the object of the present invention is to provide a method for producing a cation exchange resin, which reduces the metal impurity content in the cation exchange resin and reduces metal elution even when used for the purification of an organic acid solution. In addition, the object of the present invention is to provide a method for highly purifying an organic acid solution, which uses the above-mentioned cation exchange resin that can be regenerated.

[0011] Technical solutions for solving technical problems

[0012] The present invention is a method for producing a cation exchange resin, comprising: a first regeneration step, wherein a cation exchange resin (B) is obtained by contacting a cation exchange resin (A) with an inorganic acid solution having a metal impurity amount of 1 mg / L or less and a concentration of 5% by mass or more; a purification step, wherein an organic acid solution having a metal impurity amount of 2 mg / L or less and a concentration of 3% by mass or more is brought into contact with the cation exchange resin (B) to purify the organic acid solution; and a second regeneration step, wherein a cation exchange resin (C) is obtained by contacting an inorganic acid solution having a metal impurity amount of 1 mg / L or less and a concentration of 5% by mass or more with the cation exchange resin (B) after the purification step.

[0013] In addition, the present invention is a method for purifying an organic acid solution, characterized in that it comprises: a first regeneration step, in which a cation exchange resin (B) is obtained by contacting an inorganic acid solution having a metal impurity amount of 1 mg / L or less and a concentration of 5% by mass or more with a cation exchange resin (A); a purification step, in which an organic acid solution having a metal impurity amount of 2 mg / L or less and a concentration of 3% by mass or more is contacted with the cation exchange resin (B) to purify the organic acid solution, and the cation exchange resin (B) after the purification step is reused as the cation exchange resin (A) used in the first regeneration step, and the first regeneration step and the purification step are repeated one or more times.

[0014] Effects of the Invention

[0015] According to the present invention, a cation exchange resin can be obtained which reduces the metal impurity content in the cation exchange resin and has less metal elution even when used for the purification of an organic acid solution. In addition, by using the cation exchange resin, the metal impurity content in the organic acid solution can be stably reduced. Furthermore, according to the present invention, by regenerating and utilizing the cation exchange resin, a highly purified method for an organic acid solution that can suppress cost increase can be provided. DETAILED DESCRIPTION

[0016] <Method for producing cation exchange resin>

[0017] The method for producing a cation exchange resin with reduced metal elution according to the present invention comprises the following steps. A first regeneration step, wherein a cation exchange resin (B) is obtained by contacting a cation exchange resin (A) with an inorganic acid solution having a metal impurity amount of less than 1 mg / L and a concentration of more than 5% by mass. A refining step, wherein an organic acid solution having a metal impurity amount of less than 2 mg / L and a concentration of more than 3% by mass is brought into contact with the cation exchange resin (B) to purify the organic acid solution. A second regeneration step, wherein a cation exchange resin (C) is obtained by contacting an inorganic acid solution having a metal impurity amount of less than 1 mg / L and a concentration of more than 5% by mass with the cation exchange resin (B) after the refining step. Each step is described in detail below.

[0018] [First regeneration step]

[0019] In the first regeneration step, an inorganic acid solution having a metal impurity amount of 1 mg / L or less and a concentration of 5% by mass or more is brought into contact with the cation exchange resin (A) as a regeneration agent, thereby obtaining an H-type (hydrogen ion type) cation exchange resin (B). Here, "cation exchange resin (A)" refers to the cation exchange resin before purification, i.e., before regeneration, and "cation exchange resin (B)" refers to the cation exchange resin after purification, i.e., after regeneration. This step is a step of reducing the metal impurity content of the cation exchange resin used in the purification before the purification of the organic acid solution.

[0020] (Cation exchange resin (A))

[0021] As the cation exchange resin (A), any of the salt type such as Na type and K type, and H type cation exchange resin can be used. However, from the viewpoint of suppressing the cost increase caused by the increase in the required amount of the regeneration agent, it is preferred to use an H type cation exchange resin as the cation exchange resin (A). The cation exchange resin (A) is not particularly limited, and is preferably an organic polymer-based cation exchange resin with an organic polymer as the matrix. As the organic polymer that serves as the matrix, styrene-based resins and acrylic resins can be cited.

[0022] It should be noted that, in this specification, "styrene-based resin" refers to a resin obtained by homopolymerizing or copolymerizing styrene or a styrene derivative, and containing more than 50% by mass of structural units derived from styrene or a styrene derivative. Examples of styrene derivatives include α-methylstyrene, vinyltoluene, chlorostyrene, ethylstyrene, isopropylstyrene, dimethylstyrene, bromostyrene, etc. As a styrene-based resin, as long as the homopolymer or copolymer of styrene or a styrene derivative is used as the main component, it can also be a copolymer with other vinyl monomers that can be copolymerized. As such a vinyl monomer, for example, divinylbenzenes selected from o-divinylbenzene, m-divinylbenzene, p-divinylbenzene, etc.; polyfunctional monomers such as alkylene glycol di(meth)acrylates such as ethylene glycol di(meth)acrylate and polyethylene glycol di(meth)acrylate; (meth)acrylonitrile; and one or more of methyl (meth)acrylate, etc. Among them, divinylbenzene, ethylene glycol di(meth)acrylate, and polyethylene glycol di(meth)acrylate having an ethylene polymerization number of 4 to 16 are preferred, divinylbenzene and ethylene glycol di(meth)acrylate are more preferred, and divinylbenzene is particularly preferred.

[0023] In the present specification, the term "acrylic resin" refers to a resin obtained by homopolymerizing or copolymerizing one or more selected from acrylic acid, methacrylic acid, acrylic esters and methacrylic esters, and containing 50% by mass or more of a structural unit selected from a structural unit derived from acrylic acid, a structural unit derived from methacrylic acid, a structural unit derived from acrylic esters and a structural unit derived from methacrylic esters. Examples of the acrylic resin include homopolymers of acrylic acid, homopolymers of methacrylic acid, homopolymers of acrylic acid esters, homopolymers of methacrylic acid esters, copolymers of acrylic acid and other monomers (e.g., acrylic acid esters, methacrylic acid, methacrylic acid esters, α-olefins (e.g., ethylene, divinylbenzene, etc.)), copolymers of methacrylic acid and other monomers (e.g., acrylic acid, acrylic acid esters, methacrylic acid esters, α-olefins (e.g., ethylene, divinylbenzene, etc.)), copolymers of acrylic acid esters and other monomers (e.g., acrylic acid, methacrylic acid, methacrylic acid esters, α-olefins (e.g., ethylene, divinylbenzene, etc.)), and copolymers of methacrylic acid esters and other monomers (e.g., acrylic acid, acrylic acid esters, methacrylic acid, α-olefins (e.g., ethylene, divinylbenzene, etc.). Among them, methacrylic acid·divinylbenzene copolymers and acrylic acid·divinylbenzene copolymers are preferred.

[0024] The acrylic acid ester is preferably an alkyl acrylate, more preferably a linear alkyl ester or a branched alkyl ester of acrylic acid, and still more preferably a linear alkyl ester of acrylic acid. The number of carbon atoms of the alkyl group contained in the alkyl ester portion is preferably 1 to 4, and the acrylic acid ester is particularly preferably methyl acrylate or ethyl acrylate.

[0025] The methacrylate is preferably an alkyl methacrylate, more preferably a linear alkyl methacrylate or a branched alkyl methacrylate, and still more preferably a linear alkyl methacrylate. The number of carbon atoms of the alkyl group contained in the alkyl ester portion is preferably 1 to 4, and the alkyl methacrylate is particularly preferably methyl methacrylate or ethyl methacrylate.

[0026] In addition, the matrix of the cation exchange resin (A) can be any one of a gel type having small pore diameters and being transparent, a macroreticular type (MR type) having large pores with large pore diameters, or a macroporous type (also called a porous type or a highly porous type).

[0027] As the cation exchange resin (A), there can be mentioned a strong acid cation exchange resin having a sulfonic acid group and a weak acid cation exchange resin having a carboxylic acid group. As the cation exchange resin (A), any one of conventional pure water manufacturing resins (for example, Amberlite series (trade name, manufactured by DuPont)) can be used. Specifically, as the cation exchange resin (A), there can be mentioned Amberlite (registered trademark) IRN99H (gel-type strong acid cation exchange resin), IR120B, IR124, 200CT (all trade names, manufactured by DuPont); Amberjet (registered trademark) 1060H (gel-type strong acid cation exchange resin), 1020, 1024, 1220 (all trade names, manufactured by Ogano (Co., Ltd.)); Orlite (registered trademark) DS-1 (gel-type strong acid cation exchange resin), DS-4 (macroporous strong acid cation exchange resin) (all trade names, manufactured by Ogano (Co., Ltd.); D IAION (registered trademark) SK104H, SK1B, SK110, SK112, PK208, PK212L, PK216, PK218, PK220, PK228, UBK08, UBK10, UBK12 (all trade names, manufactured by Mitsubishi Chemical Corporation); C100, C100E, C120E, C100x10, C100x12, C150, C160, SGC650 (all trade names, manufactured by Purolite Corporation); MonoPlus S108H, SP112, S1668 (all trade names, manufactured by Lewatit Corporation), etc., but not limited thereto. The cation exchange resin (A) may be used alone or in combination of two or more.

[0028] It should be noted that, as a refined H-type cation exchange resin (B) obtained by contacting a mineral acid solution having a metal impurity amount of less than 1 mg / L and a concentration of more than 5% by mass with a cation exchange resin (A), a commercially available cation exchange resin refined by such a method can also be used. Specifically, among the cation exchange resins exemplified above, the Orlite series (trade name, manufactured by Ogano (Strain)) can be used directly as a cation exchange resin (B) in the next step, i.e., the refining step. That is, when such a cation exchange resin is used, the first regeneration step can be omitted. From the viewpoint of metal removal performance, the cation exchange resin is preferably a strongly acidic cation exchange resin, more preferably a strongly acidic cation exchange resin having a total exchange capacity of more than 1.9 eq / LR.

[0029] The average particle size of the cation exchange resin is not particularly limited, and may be, for example, 0.1 mm to 1.0 mm. Here, in the present specification, the average particle size refers to a harmonic mean diameter.

[0030] In this process, as described in Patent Document 1, by contacting a cation exchange resin (A) with an inorganic acid solution having a metal impurity content of 1 mg / L or less and a concentration of 5% by mass or more, the metal impurities contained in the cation exchange resin (A) are removed and reduced, thereby obtaining a purified H-type cation exchange resin (B). By contacting the cation exchange resin (A) with an inorganic acid solution having a very low metal impurity content, the metal impurities contained in the cation exchange resin (A) can be reliably and effectively reduced, and a cation exchange resin (B) having a low amount of eluted metal impurities can be obtained. It should be noted that after contacting the cation exchange resin (A) with the inorganic acid solution, the inorganic acid solution remaining in the resin is preferably washed and removed using pure water or ultrapure water.

[0031] The content of metal impurities in the inorganic acid solution used as a regeneration agent is 1 mg / L or less, preferably 0.5 mg / L or less, and more preferably 0.2 mg / L or less. In addition, the concentration of the inorganic acid solution is 5% by mass or more. When the concentration of the inorganic acid solution is less than 5% by mass, it is not possible to obtain a sufficient effect of reducing metal impurities in the cation exchange resin. The upper limit of the concentration of the inorganic acid solution is not limited, and is usually 30% by mass or less. It should be noted that the metal impurities contained in the inorganic acid solution are a concept that also includes metal impurity ions. As representative substances, sodium (Na), magnesium (Mg), calcium (Ca) and iron (Fe) can be cited, for example. As an inorganic acid solution, an aqueous solution is preferably used, for example, hydrochloric acid, sulfuric acid, nitric acid, etc. can be cited. "Contacting the inorganic acid solution with the cation exchange resin (A)" includes, in addition to passing the inorganic acid solution through the cation exchange resin (A) and passing it through the liquid, immersing the cation exchange resin (A) in the inorganic acid solution.

[0032] The total amount of metal impurities dissolved when 3% by mass hydrochloric acid is passed through the cation exchange resin (B) obtained in the first regeneration step in an amount of 25 times by volume is preferably 5 mg / LR or less, more preferably 3 mg / LR or less. It should be noted that, from the purpose of improving the analysis accuracy, the amount of metal impurities contained in the above-mentioned 3% by mass hydrochloric acid is preferably 1 mg / L or less, more preferably 0.5 mg / L or less, and further preferably 0.2 mg / L or less, but it is not limited thereto. In addition, "25 times by volume" hydrochloric acid means that a volume of hydrochloric acid 25 times the volume of the cation exchange resin (B) is passed. In addition, the unit " / LR" means "cation exchange resin in a water-wet state per 1L volume". It should be noted that the water-wet state refers to the state in which the ion exchanger is immersed in water. The volume of the water-wet state can be measured using a measuring instrument such as a measuring cylinder to measure the volume of the ion exchanger in a state immersed in water. Here, the cation exchange resin in a water-wet state is obtained by contacting the cation exchange resin with an atmosphere with a relative humidity of 100% at 25°C for more than 15 minutes.

[0033] The contents of sodium (Na), magnesium (Mg), calcium (Ca) and iron (Fe) in the above-mentioned inorganic acid solution with a concentration of 5% by mass or more used as a regeneration agent are preferably 200 μg / L or less. By bringing the inorganic acid solution with a small content of these metal impurities into contact with the cation exchange resin, the contents of Na, Mg, Ca and Fe in the cation exchange resin can be reliably and effectively reduced. Similarly, the contents of sodium (Na), magnesium (Mg), calcium (Ca) and iron (Fe) in the above-mentioned hydrochloric acid with a concentration of 3% are preferably 200 μg / L or less.

[0034] As a method for contacting the inorganic acid solution with the cation exchange resin (A), a known method can be used. For example, a method of passing the inorganic acid solution through a resin-filled container such as a column, a liquid delivery portion, and a storage tank can be cited. Here, the liquid delivery portion includes a pump for passing the inorganic acid solution, a device for squeezing compressed air or nitrogen, etc. The storage tank is a container for storing the inorganic acid solution and the treated inorganic acid solution. From the perspective of safety, the temperature of the inorganic acid solution during the liquid flow can be set to, for example, 15°C or more and 60°C or less. In addition, the SV (space velocity) of the inorganic acid solution passed through the resin-filled container is not particularly limited, and is preferably a low flow rate within the range that can be used. The SV of the inorganic acid solution can be set to, for example, 0.5 or more and 20 or less, preferably 10 or less, and more preferably 5 or less. In addition, the SV of the inorganic acid solution is preferably lower than the SV of the organic acid solution in the refining process described later. Relative to the amount of resin, the flow rate multiple of the inorganic acid solution passed through is preferably 1BV or more and 40BV or less. The above-mentioned liquid passing conditions are only examples, and the conditions can be adjusted appropriately. In addition, the larger the amount of high-purity inorganic acid solution used in the regeneration, the more the metal impurity content of the resin can be reduced.

[0035] [Refining process]

[0036] In the purification step, the organic acid solution is purified by bringing the cation exchange resin (B) obtained in the first regeneration step into contact with an organic acid solution having a metal impurity amount of 2 mg / L or less and a concentration of 3 mass % or more.

[0037] (Organic acid solution)

[0038] The organic acid solution to be purified is not particularly limited as long as it is an organic acid used in the semiconductor manufacturing process. Examples of such organic acids include, but are not limited to, water-soluble organic compounds having a carboxyl group, such as formic acid, citric acid, oxalic acid, malonic acid, tartaric acid, lactic acid, and malic acid, and phosphonic acids. As for the phosphonic acid, there is no particular limitation as long as it is an organic compound having a phosphonic acid group (-P=O(OH)2). Among them, citric acid and oxalic acid are preferred as organic acid solutions.

[0039] In the present invention, an organic acid solution having a metal impurity amount of 2 mg / L or less and a concentration of 3% by mass or more is used. As an organic acid solution, an organic acid solution having an organic acid concentration of 3% to 60% by mass is generally used. In addition, the total amount of metal impurities of Na (sodium), Mg (magnesium), Ca (calcium) and Fe (iron) in the organic acid solution before reducing the metal impurity content (the organic acid solution before refining in the refining process) is preferably 2 mg / L or less, more preferably 1 mg / L or less. It should be noted that an organic acid solution refined by a known method in such a manner that the total amount of the above-mentioned metal impurities in the organic acid solution before refining in the refining process becomes the above-mentioned range can be used. In the organic acid solution, in addition to the above, any metal impurities such as K (potassium), Al (aluminum), Ni (nickel), Cr (chromium), As (arsenic) may also be included.

[0040] As a method for contacting an organic acid solution with a cation exchange resin (B), a known method can be used, for example, the same method as the method for contacting an inorganic acid solution with the above-mentioned cation exchange resin (A) can be cited. Specifically, by passing the organic acid solution through a column filled with a cation exchange resin (B), the organic acid solution can be purified (column-type). In addition, the organic acid solution can also be contacted with the cation exchange resin (B) by an intermittent method. The temperature of the organic acid solution during the liquid flow, in the case of dissolving a solid organic acid in an aqueous solution, can be set to, for example, 15°C or more and 80°C or less, taking into account the fact that the organic acid is easily precipitated at low temperatures, the heat-resistant temperature of the cation exchange resin, etc. In addition, the SV (space velocity) of the organic acid solution passed through the resin filling container is not particularly limited, and is preferably 1 or more and 20 or less. Relative to the amount of resin, the flow rate multiple of the organic acid solution passed through is preferably 10BV or more. In addition, the upper limit of the flow rate multiple is preferably set by appropriately evaluating the flow rate multiple that meets the target in advance. In addition, as an example of the above-mentioned liquid flow conditions, each condition can be appropriately adjusted. By performing the above purification step, the amount of each metal impurity in the organic acid solution can be significantly reduced to preferably 10 μg / L or less, more preferably 5 μg / L or less.

[0041] [Second regeneration step]

[0042] In the second regeneration step, the cation exchange resin (B) used for the purification of the organic acid solution in the above-mentioned purification step is contacted again with an inorganic acid solution having a metal impurity amount of 1 mg / L or less and a concentration of 5% by mass or more. Thus, a cation exchange resin (C) that regenerates the cation exchange resin (B) is obtained. The second regeneration step is the same step as the above-mentioned first regeneration step, except that the "cation exchange resin (B)" used in the purification of the organic acid solution, that is, after contacting with the organic acid solution, is used as the "cation exchange resin (A)" in the above-mentioned first regeneration step. In addition, as shown in the embodiment, in the second regeneration step, when an inorganic acid solution having a metal impurity amount exceeding 1 mg / L is used as an inorganic acid solution having a concentration of 5% by mass or more, the concentration of calcium (Ca) in the resin increases. Therefore, it is important to use an inorganic acid solution having a metal impurity amount of 1 mg / L or less and a concentration of 5% by mass or more as a regeneration agent in the first regeneration step and the second regeneration step.

[0043] The cation exchange resin (C) is obtained by first contact with an inorganic acid aqueous solution of the cation exchange resin, contact with an organic acid solution, and second contact with an inorganic acid aqueous solution. Here, the contact between the cation exchange resin and the organic acid solution is a purification process of the organic acid solution in which the metal impurities in the organic acid solution are removed by the cation exchange resin. On the other hand, when it is described from the perspective of the cation exchange resin, it can also be called a purification process of the cation exchange resin in which impurities that cannot be completely removed by purification (regeneration) using an inorganic acid aqueous solution are removed by using an organic acid solution. That is, according to the method of the present invention, while the organic acid solution as the treated liquid is being purified, the impurities contained in the cation exchange resin used for the purification and not completely removed by the inorganic acid aqueous solution can be removed from the cation exchange resin by contact with the organic acid solution as the treated liquid. It should be noted that the amount of impurities contained in the cation exchange resin that are not completely removed by the inorganic acid aqueous solution is a trace amount (for example, a level of several μg / L or less), and it is believed that even if these small amounts of impurities are dissolved into the organic acid solution, they will not affect the high degree of purification of the organic acid solution.

[0044] When hydrochloric acid having a concentration of 3% by mass is passed through the cation exchange resin (C) obtained in the second regeneration step in an amount 25 times the volume ratio, the total amount of metal impurities dissolved is the same as that of the cation exchange resin (B) obtained in the first regeneration step, preferably 5 mg / LR or less, and more preferably 3 mg / LR or less. It should be noted that various metals such as sodium (Na), magnesium (Mg), calcium (Ca), iron (Fe), and aluminum (Al) can be cited as metal impurities contained in the cation exchange resin. In particular, according to the method of the present invention, the iron content in the cation exchange resin (C) can be made less than the iron content in the cation exchange resin (B) obtained after the first regeneration step. Specifically, it is known that the iron content in the cation exchange resin (C) can be reduced to, for example, 70% by mass or less, preferably 50% by mass or less, compared to the iron content in the cation exchange resin (B) obtained after the first regeneration step. It is known that iron forms a complex with hydrochloric acid or the like as an inorganic acid solution, and the complex is adsorbed in the cation exchange resin. However, it is presumed that by contacting with the organic acid solution, the iron adsorbed on the cation exchange resin as a complex can be removed from the cation exchange resin by the chelation action of the organic acid. It should be noted that the above-mentioned effect of reducing the iron content can also be obtained when the refining step and the second regeneration step are repeated.

[0045] It should be noted that, not limited to iron, by increasing the amount of the regenerant (inorganic acid solution) used in the second regeneration process, the metal impurity content of the cation exchange resin (C) can be further reduced. Specifically, the amount of inorganic acid solution used in the regeneration treatment (second regeneration process) of the resin after the first contact (first regeneration process) of the cation exchange resin with the inorganic acid solution and the contact with the organic acid solution is set to 1.0 times to 3.0 times the amount used in the first regeneration process. Alternatively, in the case of repeating the refining process and the second regeneration process, after the first contact with the organic acid solution, the inorganic acid solution is passed through the cation exchange resin, and the concentration of metals such as Ca and Fe in the inorganic acid solution after contact with the cation exchange resin is analyzed, and the amount of the metal concentration obtained is reduced to a certain amount or less as the required amount of the regenerant. Then, in the regeneration process after the second contact with the organic acid solution, the regeneration process is performed using a regenerant in the range of 1.0 times to 3.0 times the required amount of the regenerant specified above. Furthermore, when the metal removal performance does not satisfy the target value, for example, an operation of increasing the amount of the regeneration agent or an operation of increasing the concentration of the regeneration agent may be performed once in several times.

[0046] [Regeneration and application of cation exchange resin]

[0047] It is known that the life of the ion exchange resin is short in the refining of organic acid solutions compared to the refining of solutions near neutrality (see reference examples described later). That is, in the refining of organic acid solutions, the exchange frequency of the ion exchange resin becomes high, resulting in increased costs. Therefore, in order to reduce the actual exchange frequency of the ion exchange resin, in the method of the present invention, it is preferred to regenerate the cation exchange resin.

[0048] That is, in the method of the present invention, the cation exchange resin (C) obtained in the second regeneration step can be reused as the cation exchange resin (B) used in the refining step, and the refining step and the second regeneration step can be repeated one or more times. Thus, according to the present invention, the cation exchange resin (B) after the refining step used in the refining of the organic acid solution is regenerated and repeatedly used in the refining of the organic acid solution, which can reduce the actual exchange frequency of the ion exchange resin. That is, the refining cost of the organic acid solution can be suppressed.

[0049] It should be noted that, in the present specification, "cation exchange resin (B) after the purification step" refers to: a cation exchange resin (B) after one purification step, and a cation exchange resin (B) after multiple purification steps obtained after the second purification step when the cation exchange resin (C) obtained by regenerating the cation exchange resin (B) after one purification step is reused in the purification step. Similarly, "cation exchange resin (C) obtained in the second regeneration step" refers to a cation exchange resin (C) after one second regeneration step and a cation exchange resin (C) after multiple second regeneration steps.

[0050] When the cation exchange resin (C) obtained after the second regeneration step is reused as the cation exchange resin (B) in the refining step, the refining step and the second regeneration step can be repeated more than once, for example, more than 5 times, more than 10 times, more than 50 times, and more than 100 times. However, as in the present invention, when the cation exchange resin used in the highly refined organic acid solution after the metal concentration is at the μg / L level, it is necessary to manage the metal impurity content of the regenerating agent and the regenerated resin, and replace the deteriorated resin as needed. In particular, organic acids are prone to cause swelling and shrinkage of ion exchange resins. Therefore, it is important to regularly manage the deterioration state of the resin matrix.

[0051] Therefore, in particular, when the cation exchange resin (C) obtained after the (repeated) second regeneration step is reused as the cation exchange resin (B) in the purification step, it is preferred that the specified parameters of the cation exchange resin (C) be measured at specified intervals, and a part or all of the cation exchange resin (C) that has deviated from the specified range set in advance for each parameter be replaced with an H-type cation exchange resin that has not been used in the purification of the organic acid solution and has been obtained by contacting with an inorganic acid solution having a metal impurity amount of less than 1 mg / L and a concentration of more than 5% by mass (not a reused product, but a newly regenerated new cation exchange resin (B)).

[0052] Here, as the prescribed parameters, one or more selected from the group consisting of the metal impurity content of the cation exchange resin, the cracking condition and the non-sphericity rate of the surface of the cation exchange resin obtained by microscopic observation, and the exchange capacity of the cation exchange resin can be cited. Among them, from the aspect of being able to judge the deterioration of the resin at an early stage, it is preferred to measure one or more selected from the group consisting of the metal impurity content of the cation exchange resin, and the cracking condition and the non-sphericity rate of the surface of the cation exchange resin obtained by microscopic observation at predetermined intervals to manage the deterioration of the resin.

[0053] (Metal impurity content)

[0054] When the cation exchange resin is regenerated and reused for the purification of organic acid solution, it is believed that a small amount of residual impurities during regeneration will accumulate in the resin little by little. Therefore, it is preferred to regularly measure the metal impurity content in the resin, and when the metal impurity content exceeds a certain amount, part or all of it is exchanged for a new cation exchange resin. The determination of the metal impurity content, for example, can be determined by using hydrochloric acid to elute the metal contained in the resin (hydrochloric acid elution method). Specifically, for the regenerated cation exchange resin (C), ICP-MS is used to determine the total amount of metal impurities dissolved when hydrochloric acid with a concentration of 3% by mass is passed through 25 times the volume ratio. In addition, in the case of metals that cannot be eluted by acid in the resin, the microwave method (MW method) that decomposes the resin itself and determines the metal content can also be used. In addition to the analysis of the metal impurity content, the pore distribution, volume, water retention capacity, reaction rate, and exchange capacity described later of the ion exchange resin can also be analyzed.

[0055] The metal impurity content of the regenerated cation exchange resin (C) is preferably small, and the specific exchange standard is, for example, the moment when the metal impurity content exceeds 5 mg / LR, more preferably the moment when it exceeds 3 mg / LR. It should be noted that the prescribed range of the above exchange standard is preferably appropriately set based on the relationship between the metal impurity content in the organic acid solution and the metal impurity content in the resin after evaluation in advance.

[0056] (Cracks on the resin surface, non-sphericity ratio)

[0057] In the case of refining an organic acid solution with a concentration of 3% to 60% by mass used in the semiconductor manufacturing process, a liquid with a higher density and viscosity than water is purified. In the purification of such an organic acid solution, the pressure is likely to rise when the solution is passed through the resin, causing the swelling and shrinkage of the resin and the resin to break, so that the pressure is more likely to rise. Therefore, it is necessary not only to pay attention to the change in metal removal performance, but also to pay attention to the influence on the operating conditions centered on the pressure change during the liquid passing. As a method for measuring the surface cracking of the cation exchange resin by microscopic observation, a method (PBC: Perfect Beads Content) can be cited, which uses a microscope to visually or automatically count the proportion (%) of cation exchange resins without cracks, notches, cracks, etc. on the resin surface in any number of cation exchange resins. In addition, as a method for measuring the non-sphericity rate by microscopic observation, a method (WBC: Whole Beads Content) can be cited, which uses a microscope to visually or automatically count the proportion (%) of cation exchange resins that remain spherical in any number of cation exchange resins.

[0058] Regarding the cracking condition (PBC) of the resin surface, the specific exchange standard is the moment when it is below 70%, preferably below 80%, when the PBC of the new resin that has not been used for refining is set to 100%. In addition, regarding the non-sphericity (WBC), the specific exchange standard is the moment when the non-sphericity is below 80%, preferably below 90%. It should be noted that the specified range of the above-mentioned exchange standard is preferably appropriately set based on the relationship between the amount of metal impurities in the organic acid solution and the PBC and WBC of the resin. In the present invention, especially when each process is repeated, it is preferred to set a particle removal filter in the rear section of the container filled with the resin so that the particles of the broken ion exchange resin do not dissolve into the treated liquid.

[0059] (Switching capacity)

[0060] If the exchange capacity is reduced due to the deterioration of the resin, the treatment performance is reduced. Therefore, when the exchange capacity of the cation exchange resin is below a certain level, it is preferably exchanged for a new cation exchange resin. The exchange capacity can be measured by titration, etc. Regarding the exchange capacity, the specific exchange standard is the moment when the exchange capacity becomes less than 80% of the unused resin (new resin), preferably less than 90%. It should be noted that the specified range of the above-mentioned exchange standard is preferably appropriately set based on the relationship between the amount of metal impurities in the organic acid solution and the exchange capacity of the resin evaluated in advance.

[0061] As shown in the above description, as an example of the determination of each parameter of the resin, for the resin after regeneration, the total amount of metal impurities dissolved when the hydrochloric acid with a concentration of 3% by mass is passed through 25 times by volume can be cited using ICP-MS, or the metal impurity content, exchange capacity, and surface rupture and non-sphericity of the resin before and after regeneration (or before and after refining) are measured. In addition, by recording the obtained data as quality management data, it is possible to judge the exchange period of the resin before the resin deteriorates based on the data. It should be noted that when the deteriorated resin is exchanged for a newly regenerated resin (cation exchange resin (B)) rather than a reused product, it can be exchanged in full or in part. However, from the viewpoint of the ease of quality management, it is preferred to exchange in full.

[0062] In addition, about the timing of measuring each parameter, i.e., the prescribed time, there is no particular limitation and it can be set appropriately. For example, it can be carried out each time after the refining process, it can also be carried out each time after the second regeneration process, and it can also be carried out when the refining process and the second regeneration process are repeated 1 time, 2 times or 5 times each time. Alternatively, when the organic acid solution is refined using the method of the present invention, it can also be measured every other week, as long as the appropriate timing is set according to the timing of the actual operation. Each parameter can be confirmed by any one, or a plurality of parameters can be combined to confirm. It is also possible to use excessive inorganic acid for regeneration without confirming the parameters, but it is not preferred from the aspect of quality management.

[0063] (Storage Method of Resin)

[0064] In the method to which the present invention relates, the regenerated cation exchange resin can be used immediately for the refining of an organic acid solution, or it can be used for the refining of an organic acid solution after temporary storage. In addition, the cation exchange resin used in the refining of an organic acid solution can be regenerated immediately, or it can be regenerated after temporary storage. In addition, for example, when the refining of an organic acid solution and the regeneration of a cation exchange resin are implemented in different factories, it is necessary to transfer the cation exchange resin after the refining.

[0065] Here, when the resin is transferred in an organic acid impregnated state (the state of the cation exchange resin after purification), the following problems may occur. Organic acid has a high specific gravity, and the transportation cost becomes high. The transportation of organic acid with a concentration of % level itself may be limited. Due to the shaking and vibration caused by transportation, the organic acid contacts with places that are not usually in contact, which may cause metal dissolution. The resin swells in the organic acid impregnated state, so when it is stirred by vibration, the resin may be physically damaged. In addition, when the organic acid with a concentration of % level leaks or remains in the piping, it may crystallize during drying. In particular, in semiconductor manufacturing plants, organic acids with a concentration of about 20% by mass are used, but when the organic acid is dissolved by heating, it is possible to precipitate due to a decrease in temperature. In addition, it is believed that the transportation cost of the resin in a water-impregnated state after regeneration with an inorganic acid solution and washing with pure water or ultrapure water may increase if the amount of water is large.

[0066] Therefore, in order to transfer, etc., the organic acid remaining in the cation exchange resin after the refining process is stored, or the organic acid remaining in the cation exchange resin is temporarily stopped. That is, the method for manufacturing the cation exchange resin of the present invention preferably has between the refining process and the second regeneration process: a storage process, wherein the organic acid solution remaining in the cation exchange resin (B) after the refining process is replaced by water, and the cation exchange resin (B) after the water replacement is stored until it is used in the second regeneration process. In addition, as water, pure water or ultrapure water can be used. In addition, as shown above, even if the resin is in a water-immersed state, if the amount of water is large, it is believed that the transportation cost may increase, so after using water replacement, dehydration can be carried out by a known method as needed. It should be noted that the above-mentioned "cation exchange resin after the refining step used in the refining of the organic acid solution" may be a cation exchange resin after being used once in the refining of the organic acid solution (cation exchange resin (B) after the first refining step), or may be a cation exchange resin (B) after the refining and regeneration of the organic acid solution have been repeated multiple times.

[0067] The liquid flow conditions when the organic acid in the cation exchange resin used in the purification of the organic acid solution is replaced with water are not particularly limited, for example, preferably SV10 or less, about 2BV to 30BV. At this time, the pH of the aqueous solution at the outlet of the resin tower filled with the cation exchange resin can be confirmed, and washed with water until it shows a weak acid to neutral. It should be noted that the organic acid concentration in the cation exchange resin is diluted to a certain level and reduced to a concentration that is not easy to precipitate.

[0068] <Method for Purifying Organic Acid Solution>

[0069] The method for purifying an organic acid solution according to the present invention is a method for purifying an organic acid solution using a cation exchange resin obtained by the first regeneration step or the second regeneration step in the method for manufacturing the cation exchange resin. That is, the method for purifying an organic acid solution according to the present invention has the following steps. The first regeneration step, wherein a cation exchange resin (B) is obtained by contacting an inorganic acid solution having a metal impurity amount of less than 1 mg / L and a concentration of more than 5% by mass with a cation exchange resin (A). The purification step, wherein the organic acid solution is purified by contacting an organic acid solution having a metal impurity amount of less than 2 mg / L and a concentration of more than 3% by mass with the cation exchange resin (B). The method for purifying an organic acid solution according to the present invention is characterized in that the cation exchange resin (B) after the purification step is reused as the cation exchange resin (A) used in the first regeneration step, and the first regeneration step and the purification step are repeated more than once. According to this method, the cation exchange resin used for purification can be regenerated, so the substantial exchange frequency of the cation exchange resin can be reduced.

[0070] The first regeneration step and the refining step in the method for purifying an organic acid solution according to the present invention are respectively equivalent to the first regeneration step and the refining step in the method for producing a cation exchange resin according to the present invention, and detailed descriptions thereof are omitted. It should be noted that the first regeneration step after the second regeneration step in which the cation exchange resin (B) after the refining step is reused as the cation exchange resin (A) in the first regeneration step can also be said to be equivalent to the second regeneration step in the method for producing a cation exchange resin according to the present invention.

[0071] Furthermore, the regeneration and storage methods of the cation exchange resin described in the method for producing the cation exchange resin according to the present invention can also be appropriately applied to the method for purifying the organic acid solution according to the present invention.

[0072] By using the purification method of the present invention, for example, the organic acid solution can be purified according to the following process. As a resin filling container, for example, a container of a water purification cartridge size (hundreds of mL) to a gas cylinder size (several L to 70 L), or a column size (50 L to 100 L) is used, and the cation exchange resin (B) obtained in the first regeneration step is filled in these containers. Then, the treated liquid (organic acid solution) is passed through the container to obtain a purified treated liquid (first purification step). The cation exchange resin (B) after the purification step is washed with water and dehydrated in a state filled in the resin filling container. Then, the cation exchange resin (B) after water washing is reused as the cation exchange resin (A) and regenerated (the second first regeneration step). Based on the quality management of the regenerated resin and the results of the elution evaluation (conductivity, resistivity, TOC) from the regenerated resin, the quality management of the regenerated resin and the estimation of the exchange period of the resin are performed. Then, the organic acid solution is purified again (second purification step) using the regenerated cation exchange resin (B) (wherein a part or all of the cation exchange resin is exchanged as necessary). The above steps are repeated as appropriate.

[0073] (Application of anion exchange resin)

[0074] In the above description, the method for producing a cation exchange resin and the method for purifying an organic acid solution using the cation exchange resin are described, but the present invention can also be applied to the case where an anion exchange resin is used instead of the above cation exchange resin. In the embodiment using an anion exchange resin, as the anion exchange resin after regeneration in the first regeneration step, for example, Orlite series (trade name, manufactured by Ogano (Strain)) can be used, but it is not limited thereto.

[0075] Example

[0076] [Reference Example 1]: Purification of an organic acid solution using a high-purity purified resin

[0077] Using the H-type strongly acidic cation exchange resin (trade name: Orlite DS-1, manufactured by Ogano Co., Ltd.) that has been purified to high purity after the first regeneration step of the present invention, 30% by mass citric acid (Wako special grade, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., citric acid diluted with ultrapure water) was treated with SV5 for 6 hours to purify (total 30 BV). The metal concentration in the citric acid before and after purification was analyzed using Agilent 8900 triple quadrupole ICP-MS (trade name, manufactured by Agilent Technologies Co., Ltd.). The results are shown in Table 1.

[0078] As shown in Table 1, the metal concentration in 30 mass% citric acid before purification was high, about 800 μg / L, but it was completely reduced to 5 μg / L or less. In other words, the metal impurities were significantly reduced from sub-mg / L level to single-digit μg / L level.

[0079] [Reference Examples 2-3]: Confirmation of resin life in organic acid purification

[0080] Using the H-type strongly acidic cation exchange resin (trade name: Orlite DS-1, manufactured by Ogano Co., Ltd.) highly purified by the first regeneration step of the present invention, 30 mass% citric acid (Wako special grade, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., citric acid diluted with ultrapure water) was treated with SV5 for 12 hours to purify (total 60 BV). The metal concentration in the citric acid before and after purification was analyzed in the same manner as in Reference Example 1 (Reference Example 2).

[0081] In addition, in order to show that the life of the resin in the refining of the strongly acidic organic acid solution is short, the same H-type strongly acidic cation exchange resin is used to purify the simulated liquid containing metal impurities equal to or higher than the above-mentioned 30 mass % citric acid under the same conditions (treatment with SV5 for 12 hours, a total of 60 BV). As in Reference Example 1, the metal concentration in the simulated liquid before and after refining is analyzed (Reference Example 3). In addition, the simulated liquid is prepared by adding a mixed standard solution for ICP-MS (trade name: XSTC series, manufactured by SPEX) to pure water and diluting it with pure water.

[0082] The results of the purification tests of Reference Examples 2 and 3 are shown in Table 1 together with the result of the purification test of Reference Example 1.

[0083] [Table 1]

[0084]

[0085] As shown in Table 1, the simulated liquid before refining has a higher metal impurity concentration than the 30 mass % citric acid solution before refining, but no metal element exceeding 5 μg / L was observed at the time of 60 BV of liquid passing (Reference Example 3). On the other hand, in the refining test of 30 mass % citric acid, Na leaked 270 μg / L at the time of 60 BV of liquid passing (Reference Example 2). That is, at the time of 60 BV of liquid passing, Na in citric acid was not adsorbed by the resin and remained directly in the citric acid. In addition, although the concentration of the original solution is lower than that of Na, for As, no leakage was observed at the time of 30 BV of liquid passing. In contrast, at the time of 60 BV of liquid passing, it leaked to the same concentration as the original solution. These results confirm that in the refining of organic acid solutions, metal leakage occurs faster than the refining of pure water and solutions near neutrality, and the regeneration frequency of the resin becomes higher.

[0086] [Example 1]

[0087] (First regeneration step)

[0088] The H-type strongly acidic cation exchange resin (trade name: Orlite DS-1, manufactured by Ogano Co., Ltd., cation exchange resin (B)) of the present invention which has been subjected to the first regeneration step and uses an inorganic acid solution having a metal impurity amount of 1 mg / L or less and a concentration of 5% by mass or more is prepared. The total amount of metal impurities dissolved when 3% by mass hydrochloric acid is passed through the cation exchange resin (B) in an amount 25 times the volume ratio is analyzed using ICP-MS (hydrochloric acid elution 1), and the result is 5 mg / LR or less.

[0089] (Refining process)

[0090] The cation exchange resin (B) was filled into a column (diameter: 19 mm in diameter, height: 300 mm), and a 30% by mass citric acid simulation solution (metal impurity content was 2 mg / L or less, and the total amount of metal impurities of Na, Mg, Ca and Fe was 2 mg / L or less) was passed through the column at SV5. It should be noted that the 30% by mass citric acid simulation solution was prepared by dissolving Wako special grade citric acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) in pure water to 30% by mass, and then adding a mixed standard solution for ICP-MS (XSTC series, manufactured by SPEX). Then, ultrapure water was passed through the column at SV10 for more than 2 hours to confirm that the pH of the washing water was weakly acidic (pH 4) and the citric acid concentration was sufficiently low.

[0091] (Second regeneration step)

[0092] As a regeneration treatment, the metal impurity amount is 1mg / L or less and the concentration is 5% by mass or more of the inorganic acid solution and the cation exchange resin (B) used in the above-mentioned refining process (with a flow rate lower than the flow of the citric acid simulation solution in the above-mentioned refining process), thereby implementing the second regeneration process of the present invention. For the obtained cation exchange resin (C), the total amount of metal impurities dissolved when the hydrochloric acid of 3% by mass is passed through the cation exchange resin (B) by volume ratio 25 times is analyzed using ICP-MS (hydrochloric acid elution 2), and the result is 5mg / LR or less. Then, the ratio of each metal concentration obtained in the hydrochloric acid elution 1 before the organic acid flow and the hydrochloric acid elution 2 after the organic acid flow is obtained (metal concentration after the organic acid flow / metal concentration before the organic acid flow). The results are shown in Table 2.

[0093] [Table 2]

[0094]

[0095] As shown in Table 2, compared with the cation exchange resin (B) obtained in the first regeneration step, in the cation exchange resin (C) obtained after further regeneration using an inorganic acid after the organic acid liquid flow, a trend of a significant reduction in the content of Fe is particularly observed. It is believed that by the organic acid liquid flow, while removing the ion exchange reaction of the metal in the organic acid, the Fe contained in the ion exchange resin is reduced due to the chelation of the organic acid. In summary, by contacting an inorganic acid, an organic acid and an inorganic acid with the cation exchange resin in sequence, it is possible to reduce the metal contained in the cation exchange resin, which is difficult to remove only by an inorganic acid, and the metal that can be removed by an inorganic acid, and to obtain a highly refined cation exchange resin.

[0096] [Example 2]

[0097] The column (diameter: 19 mm, height: 300 mm) was filled with the same H-type strongly acidic cation exchange resin as in Example 1 as the cation exchange resin (B) that had undergone the first regeneration process (first regeneration process) of the present invention. The 30% by mass citric acid simulated solution (metal impurity amount of 2 mg / L or less, total amount of metal impurities of Na, Mg, Ca and Fe of 2 mg / L or less) used in Example 1 was passed through the column (flow rate of SV3), and then, as in Example 1, ultrapure water cleaning was performed (first refining process). Then, for the cation exchange resin (B) used in the refining, the second regeneration process of the present invention using an EL-grade inorganic acid solution (metal impurity amount of 1 mg / L or less and concentration of 5% by mass or more) was performed (implemented at a flow rate lower than the flow rate of the citric acid simulated solution in the above-mentioned refining process), and then, ultrapure water cleaning (second regeneration process) was performed. In this way, the inorganic acid regeneration (regeneration process) and the organic acid passing (refining process) were repeated, and the organic acid solution was purified 4 times in total. In the first to fourth purifications of each organic acid solution, the metal concentration in the organic acid solution before and after purification was measured using an Agilent 8900 triple quadrupole ICP-MS (trade name, manufactured by Agilent Technologies (Strain)) to evaluate the metal removal performance. The metal removal performance was evaluated by calculating the metal removal rate for each metal based on the following mathematical formula. The results are shown in Table 3.

[0098] Metal removal rate (%) = {(metal concentration before purification - metal concentration after purification) / (metal concentration before purification)} × 100

[0099] In addition, after the fourth refining of the organic acid solution, a regeneration treatment was further performed to analyze the amount of metal impurities (mg / LR) dissolved when hydrochloric acid with a concentration of 3% by mass was passed through the cation exchange resin after the regeneration treatment at a volume ratio of 25 times. The determination was performed using an Agilent 8900 triple quadrupole ICP-MS (trade name, manufactured by Agilent Technologies (strain)). Then, the amount of metal impurities obtained was compared with the amount of metal impurities of a new cation exchange resin (resin after the regeneration process) that was not used in the refining of the organic acid solution. For each metal, the ratio of the amount of metal impurities obtained by the amount of metal impurities of the resin after 4 times of refining / the amount of metal impurities of the new resin is shown in Table 4.

[0100] [Table 3]

[0101]

[0102] [Table 4]

[0103]

[0104] As shown in Table 3, even when the organic acid solution was purified using the resin that was repeatedly used in the purification of the organic acid solution, the metal removal rate in the organic acid solution exceeded 90%. In particular, for metals other than Ni, even the fourth purification showed a stable metal removal rate of more than 99%. Thus, according to the present invention, it can be confirmed that even a resin that is repeatedly used in the purification of the organic acid solution can be regenerated by regenerating it with an inorganic acid solution.

[0105] In addition, according to the results in Table 4, although metals such as Ca were observed to increase during repeated use, a trend of Fe decreasing by repeated purification and regeneration was confirmed. Furthermore, the total amount of metal impurities in the cation exchange resin was less than 5 mg / LR even when purification and regeneration were repeated, indicating that the resin can be further reused for purification of organic acid solutions.

[0106] [Comparative Example 1]

[0107] The column (diameter: 19 mm, height: 300 mm) was filled with a cation exchange resin purified by the same method as in Example 1. Then, a mineral acid solution with a concentration of 5 mass % or more and a metal impurity content exceeding 1 mg / L was passed through at a flow rate lower than that of the citric acid simulated solution to implement a second regeneration step. The cation exchange resin (C) obtained after regeneration was analyzed for metal impurities by the same method as in Example 1.

[0108] As a result, the amount of Ca contained in the cation exchange resin (C) after the regeneration was 5 times or more the amount of Ca contained in the cation exchange resin (C) after the second regeneration step in Example 1.

[0109] [Example 3]

[0110] 20% by mass of citric acid (Wako special grade, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., diluted with ultrapure water, metal impurity amount is less than 2 mg / L, and the total amount of metal impurities of Na, Mg, Ca and Fe is less than 2 mg / L) is injected into a 250 mL beaker. The same cation exchange resin as in Example 1 is immersed therein as the cation exchange resin (B) that has undergone the first regeneration step of the present invention, and the mixture is allowed to stand for 30 minutes (purification step). In addition, 20% by mass of citric acid is used at 5 BV relative to the cation exchange resin (B). After standing, the citric acid is removed, and the cation exchange resin (B) after contact with the citric acid is regenerated by being immersed in an inorganic acid solution having a metal impurity amount of less than 1 mg / L and a concentration of more than 5% by mass for 30 minutes (using an inorganic acid solution at 5 BV), and then washed with ultrapure water (second regeneration step). The PBC, WBC and exchange capacity of the resin sample obtained after the purification step and the second regeneration step are further repeated 10 times are measured.

[0111] It should be noted that PBC is calculated by visually counting the proportion (%) of cation exchange resins without cracks, defects, cracks, etc. on the resin surface in the cation exchange resin using a microscope (trade name: digital microscope, manufactured by KEYENCE Co., Ltd.). In addition, WBC is calculated by visually counting the proportion (%) of cation exchange resins that remain spherical in the cation exchange resin using the above-mentioned microscope. Furthermore, the exchange capacity is the number of moles of acid consumed by ion exchange by passing an acid through a cation exchange resin prepared in a salt form and determining it by neutralization titration. The results are shown in Table 5. It should be noted that in the table, the "ultrapure water" condition refers to the condition in which the above-mentioned cation exchange resin (B) is immersed in ultrapure water equal to the above-mentioned citric acid, which is equivalent to the condition of a refined new resin (resin that has undergone the first regeneration step) that has not yet been used for an organic acid solution. In addition, in Table 5, with respect to PBC, the value of PBC under each condition is shown when the PBC under ultrapure water conditions is set to 100%.

[0112] [Table 5]

[0113]

[0114] As shown in Table 5, when the purification and regeneration of the organic acid solution were repeated for a total of 11 times, although the WBC did not change, a decrease in PBC was observed. It should be noted that if the PBC is less than 90% compared with the new resin (ultrapure water conditions in Table 5), it is still at a level that can be used for repeated purification. From this result, it can be seen that as an indicator for measuring the deterioration of the resin, the use of PBC compared with WBC can grasp the damage of the resin matrix in advance. In addition, when the purification and regeneration of the organic acid solution were repeated for a total of 11 times, a decrease in PBC was confirmed, but there was no effect on the exchange capacity itself. That is, it can be seen that the repeated purification and regeneration of the organic acid solution has a greater impact on the matrix than the exchange capacity due to the rupture of the resin.

[0115] The present invention includes the following configurations.

[0116] [Composition 1]

[0117] A method for producing a cation exchange resin, characterized by comprising:

[0118] The first regeneration step comprises bringing the cation exchange resin (A) into contact with an inorganic acid solution having a metal impurity amount of 1 mg / L or less and a concentration of 5% by mass or more to obtain a cation exchange resin (B),

[0119] a purification step, wherein the organic acid solution is purified by contacting the cation exchange resin (B) with an organic acid solution having a metal impurity amount of 2 mg / L or less and a concentration of 3 mass % or more, and

[0120] In the second regeneration step, the cation exchange resin (C) is obtained by contacting the cation exchange resin (B) after the purification step with an inorganic acid solution having a metal impurity amount of 1 mg / L or less and a concentration of 5 mass % or more.

[0121] [Composition 2]

[0122] The method for producing a cation exchange resin according to configuration 1, wherein the cation exchange resin (C) obtained in the second regeneration step is reused as the cation exchange resin (B) used in the purification step, and the purification step and the second regeneration step are repeated one or more times.

[0123] [Composition 3]

[0124] The method for producing a cation exchange resin according to configuration 1 or 2, wherein the organic acid solution is selected from formic acid, citric acid, oxalic acid, malonic acid, tartaric acid, lactic acid, malic acid and phosphonic acids.

[0125] [Composition 4]

[0126] According to the method for producing a cation exchange resin as described in configuration 3, the concentration of the organic acid solution is 3% to 60% by mass, and the total amount of metal impurities such as Na (sodium), Mg (magnesium), Ca (calcium) and Fe (iron) in the organic acid solution before purification provided to the refining step is less than 2 mg / L.

[0127] [Composition 5]

[0128] A method for producing a cation exchange resin according to any one of configurations 1 to 4, wherein the total amount of metal impurities eluted when hydrochloric acid having a concentration of 3 mass % is passed through the cation exchange resin (B) obtained in the first regeneration step in an amount 25 times the volume ratio is 5 mg / LR or less, and the total amount of metal impurities eluted when hydrochloric acid having a concentration of 3 mass % is passed through the cation exchange resin (C) obtained in the second regeneration step in an amount 25 times the volume ratio is 5 mg / LR or less.

[0129] [Composition 6]

[0130] According to the method for producing a cation exchange resin according to any one of structures 1 to 5, for the cation exchange resin (C) obtained in the second regeneration step which is arbitrarily repeated, one or more parameters selected from the group consisting of the metal impurity content, the surface cracking condition and the non-sphericity rate are measured at prescribed intervals, and the cation exchange resin (C) deviating from the prescribed range pre-set for each parameter is exchanged with a cation exchange resin that has not been used in the purification of the organic acid solution and is obtained by contacting with an inorganic acid solution having a metal impurity amount of less than 1 mg / L and a concentration of more than 5% by mass.

[0131] [Composition 7]

[0132] According to the method for producing a cation exchange resin according to any one of structures 1 to 6, there is a storage step between the refining step and the second regeneration step, wherein the organic acid solution remaining in the cation exchange resin (B) after the refining step is replaced with water, and the cation exchange resin (B) replaced with water is stored until it is used in the second regeneration step.

[0133] [Composition 8]

[0134] The method for producing a cation exchange resin according to any one of Configurations 1 to 7, wherein the iron (Fe) content in the cation exchange resin (C) obtained in the second regeneration step is lower than the iron (Fe) content in the cation exchange resin (B) obtained in the first regeneration step.

[0135] [Composition 9]

[0136] A method for purifying an organic acid solution, characterized by:

[0137] The first regeneration step comprises bringing the cation exchange resin (A) into contact with an inorganic acid solution having a metal impurity amount of 1 mg / L or less and a concentration of 5% by mass or more to obtain a cation exchange resin (B),

[0138] a purification step of purifying the organic acid solution by bringing the cation exchange resin (B) into contact with an organic acid solution having a metal impurity amount of 2 mg / L or less and a concentration of 3% by mass or more,

[0139] The cation exchange resin (B) after the purification step is reused as the cation exchange resin (A) used in the first regeneration step, and the first regeneration step and the purification step are repeated one or more times.

Claims

1. A method for producing a cation exchange resin, characterized in that: have: The first regeneration step comprises bringing the cation exchange resin (A) into contact with an inorganic acid solution having a metal impurity amount of 1 mg / L or less and a concentration of 5% by mass or more to obtain a cation exchange resin (B), a purification step, wherein the organic acid solution is purified by contacting the cation exchange resin (B) with an organic acid solution having a metal impurity amount of 2 mg / L or less and a concentration of 3 mass % or more, and In the second regeneration step, the cation exchange resin (C) is obtained by contacting the cation exchange resin (B) after the purification step with an inorganic acid solution having a metal impurity amount of 1 mg / L or less and a concentration of 5 mass % or more.

2. The method for producing a cation exchange resin according to claim 1, wherein The cation exchange resin (C) obtained in the second regeneration step is reused as the cation exchange resin (B) used in the purification step, and the purification step and the second regeneration step are repeated one or more times.

3. The method for producing a cation exchange resin according to claim 1 or 2, wherein: The organic acid solution is selected from formic acid, citric acid, oxalic acid, malonic acid, tartaric acid, lactic acid, malic acid and phosphonic acid.

4. The method for producing a cation exchange resin according to claim 3, wherein The concentration of the organic acid solution is 3% to 60% by mass, and the total amount of metal impurities such as Na (sodium), Mg (magnesium), Ca (calcium) and Fe (iron) in the organic acid solution before purification in the purification step is 2 mg / L or less.

5. The method for producing a cation exchange resin according to claim 1 or 2, wherein: When hydrochloric acid with a concentration of 3 mass % is passed through the cation exchange resin (B) obtained in the first regeneration step in an amount 25 times the volume ratio, the total amount of metal impurities eluted is 5 mg / LR or less, and when hydrochloric acid with a concentration of 3 mass % is passed through the cation exchange resin (C) obtained in the second regeneration step in an amount 25 times the volume ratio, the total amount of metal impurities eluted is 5 mg / LR or less.

6. The method for producing a cation exchange resin according to claim 2, wherein: For the cation exchange resin (C) obtained in the repeated second regeneration step, at least one parameter selected from the group consisting of the metal impurity content, the surface cracking condition and the non-sphericity rate is measured at predetermined intervals, and the cation exchange resin (C) deviating from the predetermined range set in advance for each parameter is replaced with a cation exchange resin that has not been used in the purification of the organic acid solution and is obtained by contacting with an inorganic acid solution having a metal impurity amount of less than 1 mg / L and a concentration of more than 5% by mass.

7. The method for producing a cation exchange resin according to claim 1 or 2, wherein: Between the refining step and the second regeneration step, there is: A storage step of replacing the organic acid solution remaining in the cation exchange resin (B) after the purification step with water, and storing the cation exchange resin (B) after the replacement with water until it is used in the second regeneration step.

8. The method for producing a cation exchange resin according to claim 1, wherein The content of iron (Fe) in the cation exchange resin (C) obtained in the second regeneration step is smaller than the content of iron (Fe) in the cation exchange resin (B) obtained in the first regeneration step.

9. A method for purifying an organic acid solution, characterized in that: have: The first regeneration step comprises bringing the cation exchange resin (A) into contact with an inorganic acid solution having a metal impurity amount of 1 mg / L or less and a concentration of 5% by mass or more to obtain a cation exchange resin (B), a purification step, wherein the organic acid solution is purified by contacting the cation exchange resin (B) with an organic acid solution having a metal impurity amount of 2 mg / L or less and a concentration of 3% by mass or more. The cation exchange resin (B) after the purification step is reused as the cation exchange resin (A) used in the first regeneration step, and the first regeneration step and the purification step are repeated one or more times.

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