JP7477374B2 - Method for changing ion type of monolithic organic porous anion exchanger and method for producing monolithic organic porous anion exchanger - Google Patents

Description

The present invention relates to a method for changing the ionic form of an anion exchanger and a method for producing an anion exchanger.

Anion exchangers have traditionally been used to remove metal ions and other contaminants from ultrapure water, as well as from various chemical solutions such as alcohols and ethers.

For example, ultrapure water used in semiconductor manufacturing processes is highly purified in refining equipment called a subsystem (see, for example, Patent Document 1 (JP 2010-234356 A)), but impurities such as metal components may leach out from pipes and valves during delivery from the subsystem to each use point (wet station) where the semiconductor manufacturing process is carried out. In addition, impurities such as metal components may leach out from chemical storage tanks and delivery pipes for chemicals such as various alcohols and ethers used as cleaning agents and dissolving solvents.

For this reason, if the above impurities are anionic, it may be possible to remove the impurities by placing purification cartridges containing anion exchangers near each use point.

In addition, the ultrapure water that is supplied to the point of use in the above semiconductor manufacturing process and used for cleaning is recovered and reused as part of the raw water for producing ultrapure water.

However, in the above-mentioned semiconductor manufacturing process, it is conceivable that ionic impurities such as B elements and As elements or fine particles may be eluted from the constituent material of the workpiece (semiconductor material) into the ultrapure water, and therefore the recovered ultrapure water is likely to contain a large amount of ionic impurities or fine particles.
For this reason, when reusing the recovered ultrapure water, it is necessary to remove ionic impurities or fine particles that have been mixed into the ultrapure water in advance.

As a method for removing ionic impurities or fine particles from the recovered ultrapure water, the applicant has previously proposed a method for purifying ultrapure water using an ion exchanger-packed module packed with a monolithic organic porous anion exchanger (see International Application No. PCT/JP2019/019348).

JP 2010-234356 A

In this way, the use of anion exchangers has been proposed to remove ionic impurities or fine particles contained in ultrapure water or chemical solutions, and there is a demand for preparing anion exchangers suitable for purifying the above-mentioned ultrapure water, and for regenerating anion exchangers used in purifying the above-mentioned ultrapure water after use and reusing them again.

In anion exchangers having quaternary ammonium groups or amino groups as anion exchange groups, the ionic form (the form of the counter ion of the anion exchange group) is preferably the OH form in order to enhance the performance of removing impurity elements. Therefore, it is required to convert the ionic form to the OH form during preparation of the anion exchanger, and to regenerate the ionic form of the anion exchanger to the OH form during regeneration.
In order to change the ionic form of an anion exchanger to the OH form, the following treatments are usually carried out in the following order: (1) acid treatment, (2) water treatment, (3) hydrochloric acid treatment, (4) water treatment, (5) carbonate or bicarbonate treatment, (6) water treatment, and (7) sodium hydroxide treatment.
That is, after the anion exchanger is washed with an acid, the counter ions of the anion exchange groups are successively converted to nitrate ions, chloride ions, and carbonate ions, and then converted to hydroxide ions. By performing the processes in this order, it is believed that a high proportion of the ionic form can be changed to the OH form.

However, the above-mentioned ionic form changing method requires many processing steps, and the processing time is long and the processing is laborious, so there has been a demand for a simpler method for changing the ionic form to the OH form in a short time.
In addition, the above-mentioned ion form changing method requires a long water treatment after the above-mentioned "(7) Sodium hydroxide treatment" because various metals mixed as impurities in the carbonate or bicarbonate remain in the anion exchanger during the above-mentioned "(5) Carbonate or bicarbonate treatment" and because sodium remains in the anion exchanger during the above-mentioned "(7) Sodium hydroxide treatment". In addition, it is necessary to place an additional cation exchanger downstream of the anion exchanger during use to remove metal eluates (metal ions).

Under these circumstances, the present invention aims to provide a method for easily and quickly changing the ionic form of an anion exchanger at a high rate while suppressing the residual amount of various metals, and a method for producing an anion exchanger.

As a result of intensive research conducted by the inventors to achieve the above object, they discovered that the above technical problems can be solved by contacting an anion exchanger used in the purification of ultrapure water or chemical solutions with an aqueous solution of a quaternary ammonium hydroxide in order to change the ionic form of the anion exchanger. Based on this finding, they have completed the present invention.

（式中、Ｒ^１～Ｒ^４は、各々水酸基を有していてもよい炭素数１～４の炭化水素基であり、互いに同一であっても異なっていてもよい。）
で表される化合物から選ばれる一種以上である上記（１）に記載のアニオン交換体のイオン形変更方法、
（３）前記第四級アンモニウム水酸化物の水溶液中における第四級アンモニウム水酸化物の濃度が０．１～２．０Ｎである上記（１）または（２）に記載のアニオン交換体のイオン形変更方法、
（４）前記アニオン交換体を、鉱酸と接触し、次いで水で洗浄した後に前記第四級アンモニウム水酸化物の水溶液と接触させる上記（１）～（３）のいずれかに記載のアニオン交換体のイオン形変更方法、
（５）前記アニオン交換体を、鉱酸と接触し、次いで水で洗浄した後、さらに塩酸と接触し、次いで水で洗浄した上で、前記第四級アンモニウム水酸化物の水溶液と接触させる上記（１）～（４）のいずれかに記載のアニオン交換体のイオン形変更方法、
（６）前記アニオン交換体がモノリス状有機多孔質アニオン交換体である上記（１）～（５）のいずれかに記載のアニオン交換体のイオン形変更方法、
（７）前記モノリス状有機多孔質アニオン交換体が、全構成単位中、架橋構造単位を０．１～５．０モル％含有する芳香族ビニルポリマーからなる平均太さが乾燥状態で１～６０μｍの三次元的に連続した骨格と、その骨格間に平均直径が乾燥状態で１０～２００μｍの三次元的に連続した空孔とからなる共連続構造体であって、乾燥状態での全細孔容積が０．５～１０ｍＬ／ｇであり、アニオン交換基を有しており、水湿潤状態での体積当りのアニオン交換容量が、０．２～１．０ｍｇ当量／ｍＬ（水湿潤状態）であり、アニオン交換基が有機多孔質アニオン交換体中に均一に分布しているモノリス状有機多孔質アニオン交換体である上記（６）に記載のアニオン交換体のイオン形変更方法、
（８）前記アニオン交換体に対し、第四級アンモニウム水酸化物の水溶液を、液空間速度ＳＶが２００００ｈ^－１以下となるように通液する上記（６）または～（７）に記載のアニオン交換体のイオン形変更方法、および
（９）超純水の精製または薬液の精製に使用するアニオン交換体の製造時にイオン形を変更するために、前記アニオン交換体と第四級アンモニウム水酸化物の水溶液とを接触させることを特徴とするアニオン交換体の製造方法、
を提供するものである。 That is, the present invention provides
(1) A method for changing the ion type of an anion exchanger used in the purification of ultrapure water or chemical solutions, comprising contacting the anion exchanger with an aqueous solution of a quaternary ammonium hydroxide;
(2) The quaternary ammonium hydroxide is represented by the following general formula (I):

(In the formula, R ¹ to R ⁴ are each a hydrocarbon group having 1 to 4 carbon atoms which may have a hydroxyl group, and may be the same or different.)
The method for changing the ion type of an anion exchanger according to the above (1),
(3) The method for changing the ion form of an anion exchanger according to (1) or (2) above, wherein the concentration of the quaternary ammonium hydroxide in the aqueous solution of the quaternary ammonium hydroxide is 0.1 to 2.0 N;
(4) A method for changing the ion form of an anion exchanger according to any one of (1) to (3) above, which comprises contacting the anion exchanger with a mineral acid, washing the anion exchanger with water, and then contacting the anion exchanger with an aqueous solution of the quaternary ammonium hydroxide;
(5) A method for changing the ion form of an anion exchanger according to any one of (1) to (4) above, which comprises contacting the anion exchanger with a mineral acid, washing it with water, contacting it with hydrochloric acid, washing it with water, and then contacting it with an aqueous solution of the quaternary ammonium hydroxide;
(6) The method for changing the ionic form of an anion exchanger according to any one of (1) to (5) above, wherein the anion exchanger is a monolithic organic porous anion exchanger;
(7) The method for changing the ionic form of an anion exchanger according to (6) above, wherein the monolithic organic porous anion exchanger is a bicontinuous structure consisting of a three-dimensionally continuous skeleton having an average thickness of 1 to 60 μm in a dry state, which is made of an aromatic vinyl polymer containing 0.1 to 5.0 mol % of crosslinked structural units among all structural units, and three-dimensionally continuous pores having an average diameter of 10 to 200 μm in a dry state between the skeletons, the total pore volume in a dry state being 0.5 to 10 mL/g, the anion exchange group being present, the anion exchange capacity per volume in a water-wet state being 0.2 to 1.0 mg equivalent/mL (water-wet state), and the anion exchange group being uniformly distributed in the organic porous anion exchanger;
(8) A method for changing the ion type of an anion exchanger according to any one of (6) to (7) above, in which an aqueous solution of a quaternary ammonium hydroxide is passed through the anion exchanger so that the liquid hourly space velocity (SV) is 20,000 h ^-1 or less; and (9) a method for producing an anion exchanger, in order to change the ion type during the production of an anion exchanger used in the purification of ultrapure water or chemical solutions, the method being characterized in that the anion exchanger is brought into contact with an aqueous solution of a quaternary ammonium hydroxide.
This provides:

The present invention provides a method for easily and quickly changing the ionic form of an anion exchanger at a high rate while suppressing the residual amount of various metals, and a method for producing an anion exchanger.

1 is a SEM photograph of an example of the morphology of a monolithic organic porous anion exchanger. FIG. 1 is a schematic diagram of a bicontinuous structure of a monolithic organic porous anion exchanger. 1 is a SEM photograph of an example of the morphology of a monolithic organic porous intermediate body. FIG. 2 is a diagram for explaining an example of the contact form between an anion exchanger and an aqueous solution of a quaternary ammonium hydroxide in the present invention. FIG. 1 shows a purification apparatus U having a vessel A containing an anion exchanger and a vessel C containing a cation exchanger. FIG. 1 is a diagram showing results in an example of the present invention and a comparative example.

First, the method for changing the ion type of an anion exchanger according to the present invention will be described.
The method for changing the ion form of an anion exchanger according to the present invention is characterized in that the anion exchanger used for purifying ultrapure water or purifying chemical solutions is brought into contact with an aqueous solution of a quaternary ammonium hydroxide in order to change the ion form of the anion exchanger.

<Anion exchanger>
In the present invention, the anion exchanger used for purifying ultrapure water may be one that is incorporated into various production processes in order to purify ultrapure water used in the same production processes, or one that is used to recover and purify ultrapure water that has been used once.

In the present invention, the anion exchanger used to purify a drug solution may be one that is incorporated into the drug solution manufacturing process in order to purify the drug solution, or it may be one that is used to separately purify a drug solution that has already been manufactured.

The chemicals to be purified include hydrogen peroxide, hydrochloric acid, hydrofluoric acid, phosphoric acid, acetic acid, tetramethylammonium hydroxide, ammonium fluoride, acetone, 2-butanone, n-butyl acetate, ethanol, methanol, 2-propanol, toluene, xylene, propylene glycol methyl ether acetate, N-methyl-2-pyrrolidinone, ethyl lactate, phenolic compounds, dimethyl sulfoxide, tetrahydrofuran, gamma-butyrolactone, polyethylene glycol monomethyl ether (PGMEA), etc.

In the present invention, the anion exchanger means an ion exchanger having an anion exchange capacity. The anion exchanger can be selected from a monolithic organic porous anion exchanger, an anion exchange resin (anion exchange resin), etc., and is preferably a monolithic organic porous anion exchanger.

<Monolithic organic porous anion exchanger>
In the present invention, when the anion exchanger is a monolithic organic porous anion exchanger, the monolithic organic porous anion exchanger is not particularly limited.

The monolithic organic porous anion exchanger is a porous body in which anion exchange groups are introduced into the monolithic organic porous body. The monolithic organic porous body relating to the monolithic organic porous anion exchanger is a porous body in which the skeleton is formed from an organic polymer and has a large number of communicating holes between the skeletons that serve as flow paths for the reaction solution. The monolithic organic porous anion exchanger is a porous body in which anion exchange groups are introduced so as to be uniformly distributed in the skeleton of the monolithic organic porous body.
In this specification, a "monolithic organic porous material" is also referred to simply as a "monolith," a "monolithic organic porous anion exchanger" is also referred to simply as a "monolith anion exchanger," a "monolithic organic porous cation exchanger" is also referred to simply as a "monolith cation exchanger," and a "monolithic organic porous intermediate," which is an intermediate (precursor of a monolith) in the production of a monolith, is also referred to simply as a "monolith intermediate."

In the present invention, the monolith anion exchanger is obtained by introducing anion exchange groups into a monolith, and its structure is an organic porous body consisting of a continuous skeleton phase and a continuous pore phase, and it is preferable that the thickness of the continuous skeleton is 1 to 100 μm, the average diameter of the continuous pores is 1 to 1000 μm, and the total pore volume is 0.5 to 50 mL/g.

If the thickness of the continuous skeleton of the monolith anion exchanger is less than 1 μm, not only will the anion exchange capacity per volume decrease, but the mechanical strength will also decrease, making the monolith anion exchanger more susceptible to significant deformation, particularly when liquid is passed through it at a high flow rate, and the contact efficiency between the reaction liquid and the monolith anion exchanger will decrease, making it easier for the catalytic activity to decrease, which is undesirable.
On the other hand, if the thickness of the continuous skeleton of the monolith anion exchanger exceeds 100 μm, the skeleton becomes too thick, which takes time for the substrate to diffuse and undesirably reduces the catalytic activity.
The thickness of the continuous skeleton is determined by SEM observation.

If the average diameter of the interconnected pores of the monolith anion exchanger is less than 1 μm, the pressure loss during water flow is likely to be high, and if the average diameter of the interconnected pores of the monolith anion exchanger exceeds 1000 μm, contact between the treated liquid and the monolith anion exchanger becomes insufficient, and the removal performance is likely to decrease.
The average diameter of the continuous pores of the monolith anion exchanger in a dry state is measured by mercury intrusion porosimetry and refers to the maximum value of the pore distribution curve obtained by mercury intrusion porosimetry.

If the total pore volume of the monolith anion exchanger is less than 0.5 mL/g, the contact efficiency of the treated liquid is likely to be low, the amount of permeated liquid per unit cross-sectional area is small, and the treatment amount is likely to be reduced. If the total pore volume of the monolith anion exchanger exceeds 50 mL/g, the anion exchange capacity per volume is reduced, the removal performance is likely to be reduced, and the mechanical strength is reduced, causing the monolith anion exchanger to deform significantly, especially when liquid is passed through it at high speed, and causing a sudden increase in pressure loss during liquid passage.
The total pore volume is measured by mercury intrusion porosimetry.

Examples of such monolith anion exchanger structures include the open cell structure disclosed in JP-A-2002-306976 and JP-A-2009-62512, the bicontinuous structure disclosed in JP-A-2009-67982, the particle aggregate structure disclosed in JP-A-2009-7550, and the particle composite structure disclosed in JP-A-2009-108294.

The anion exchange capacity per volume of the monolith anion exchanger in a water-wet state is preferably 0.1 to 1.0 mg equivalent/mL (water-wet state).
If the anion exchange capacity of the monolith anion exchanger in a dry state is less than 0.1 mg equivalent/mL, the amount of water to be treated before breakthrough will be reduced, and the exchange module filled with the monolith anion exchanger will tend to need to be replaced more frequently. On the other hand, if the anion exchange capacity of the monolith anion exchanger in a dry state exceeds 1.0 mg equivalent/mL, the pressure loss during water flow will tend to increase.
The anion exchange capacity of a porous material in which anion exchange groups are introduced only on the skeleton surface cannot be determined in general terms depending on the type of porous material and anion exchange group, but is at most 500 μg equivalent/g.

The anion exchange groups introduced into the monolith anion exchanger are distributed uniformly not only on the surface of the monolith but also inside the monolith skeleton. Here, "the anion exchange groups are distributed uniformly" means that the anion exchange groups are distributed uniformly on the surface and inside the skeleton at least on the order of μm. The distribution of the anion exchange groups can be easily confirmed using EPMA. Furthermore, if the anion exchange groups are distributed uniformly not only on the surface of the monolith but also inside the skeleton of the monolith, the physical and chemical properties of the surface and inside can be made uniform, which makes it easier to improve durability against swelling and shrinkage.

Examples of anion exchange groups introduced into the monolith anion exchanger include quaternary ammonium groups such as trimethylammonium groups, triethylammonium groups, tributylammonium groups, dimethylhydroxyethylammonium groups, dimethylhydroxypropylammonium groups, and methyldihydroxyethylammonium groups, as well as tertiary sulfonium groups and phosphonium groups.

In monolithic anion exchangers, the material constituting the continuous framework is usually an organic polymer material having a cross-linked structure.
The crosslink density of the polymer material is not particularly limited, but it is preferable that the polymer material contains 0.1 to 30 mol %, and more preferably 0.1 to 20 mol %, of crosslinked structural units based on the total structural units constituting the polymer material.
If the crosslinked structural unit is less than 0.1 mol%, the mechanical strength is insufficient, which is not preferable, whereas if the crosslinked structural unit is more than 30 mol%, the introduction of anion exchange groups may be difficult, which is not preferable. The type of the polymer material is not particularly limited, and examples thereof include aromatic vinyl polymers such as polystyrene, poly(α-methylstyrene), polyvinyltoluene, polyvinylbenzyl chloride, polyvinylbiphenyl, and polyvinylnaphthalene; polyolefins such as polyethylene and polypropylene; poly(halogenated polyolefins) such as polyvinyl chloride and polytetrafluoroethylene; nitrile-based polymers such as polyacrylonitrile; and (meth)acrylic polymers such as polymethyl methacrylate, polyglycidyl methacrylate, and polyethyl acrylate. The polymer may be a polymer obtained by copolymerizing a single vinyl monomer and a crosslinking agent, or a polymer obtained by polymerizing multiple vinyl monomers and a crosslinking agent, or may be a blend of two or more polymers. Among these organic polymer materials, crosslinked polymers of aromatic vinyl polymers are preferred from the viewpoints of ease of forming a continuous structure, ease of introducing anion exchange groups, high mechanical strength, and high stability against acids or alkalis. In particular, styrene-divinylbenzene copolymers and vinylbenzyl chloride-divinylbenzene copolymers are cited as preferred materials.

<Examples of the form of monolithic organic porous anion exchanger>
As an example of the form of the monolithic organic porous anion exchanger (hereinafter, appropriately referred to as monolith anion exchanger a), a monolith anion exchanger having a bicontinuous structure consisting of a three-dimensionally continuous skeleton having an average thickness of 1 to 60 μm in a dry state, which is made of an aromatic vinyl polymer containing 0.1 to 5.0 mol% of crosslinked structural units among all constituent units, and three-dimensionally continuous pores having an average diameter of 10 to 200 μm in a dry state between the skeletons, a total pore volume in a dry state of 0.5 to 10 mL/g, anion exchange groups, an anion exchange capacity per volume in a water-wet state of 0.2 to 1.0 mg equivalent/mL (water-wet state), and anion exchange groups uniformly distributed in the organic porous anion exchanger is preferred.
Furthermore, the monolith (before the anion exchange groups are introduced) constituting the monolith anion exchanger a (hereinafter, appropriately referred to as monolith a) is preferably an organic porous body having a bicontinuous structure consisting of a three-dimensionally continuous skeleton having an average thickness of 1 to 60 μm in a dry state, which skeleton is made of an aromatic vinyl polymer containing 0.1 to 5.0 mol % of crosslinked structural units among all structural units, and three-dimensionally continuous pores having an average diameter of 10 to 200 μm in a dry state between the skeletons, and having a total pore volume in a dry state of 0.5 to 10 mL/g.

The monolith anion exchanger a is a bicontinuous structure consisting of a three-dimensionally continuous skeleton having an average thickness in a dry state of 1 to 60 μm, preferably 3 to 58 μm, and three-dimensionally continuous pores between the skeleton having an average diameter in a dry state of 10 to 200 μm, preferably 15 to 180 μm, particularly preferably 20 to 150 μm.
Fig. 1 shows an SEM photograph of an example of the form of monolith anion exchanger a, and Fig. 2 shows a schematic diagram of the cocontinuous structure of monolith anion exchanger a. As shown in the schematic diagram of Fig. 2, the cocontinuous structure is a structure 10 in which a continuous skeleton phase 1 and a continuous pore phase 2 are intertwined and are three-dimensionally continuous. These continuous pores 2 have higher pore continuity and no bias in size compared to conventional open-cell monoliths and particle-aggregation monoliths. In addition, the skeleton is thick, so the mechanical strength is high.

If the average diameter of the three-dimensionally continuous pores is less than 10 μm in a dry state, it is not preferable because the treated liquid is difficult to diffuse, and if it exceeds 200 μm, the contact between the treated liquid and the monolith anion exchanger a becomes insufficient, resulting in insufficient removal performance, which is not preferable. Also, if the average thickness of the skeleton is less than 1 μm in a dry state, it is not preferable because the anion exchange capacity is low and the mechanical strength is low. Furthermore, it is not preferable because the contact efficiency between the reaction liquid and the monolith anion exchanger a decreases, resulting in a decrease in removal performance. On the other hand, if the thickness of the skeleton exceeds 60 μm, it is not preferable because the skeleton becomes too thick and the treated liquid is diffused unevenly.

The average diameter of the openings of the monolith a in the dry state, the average diameter of the openings of the monolith anion exchanger a in the dry state, and the average diameter of the openings of the monolith intermediate in the dry state (hereinafter referred to as monolith intermediate a) obtained in step I of the production of monolith a described below are determined by mercury intrusion porosimetry and refer to the maximum value of the pore distribution curve obtained by mercury intrusion porosimetry. The average thickness of the skeleton of the monolith anion exchanger a in the dry state is determined by SEM observation of the monolith anion exchanger a in the dry state. Specifically, SEM observation of the monolith anion exchanger a in the dry state is performed at least three times, the thickness of the skeleton in the obtained image is measured, and the average value of these is taken as the average thickness. The skeleton is rod-shaped and has a circular cross-sectional shape, but may also include one with a cross-section of different diameters such as an elliptical cross-sectional shape. In this case, the thickness is the average of the minor axis and the major axis.

The total pore volume per weight of the monolith anion exchanger a in a dry state is 0.5 to 10 mL/g. If the total pore volume is less than 0.5 mL/g, the contact efficiency of the substrate and the solvent will be low, which is undesirable, and furthermore, the permeation amount per unit cross-sectional area will be small, which is undesirable, resulting in a decrease in the processing amount. On the other hand, if the total pore volume exceeds 10 mL/g, the contact efficiency between the treated liquid and the monolith anion exchanger will decrease, which is undesirable, resulting in a decrease in removal performance. If the size of the three-dimensionally continuous pores and the total pore volume are within the above ranges, the contact with the treated liquid will be extremely uniform and the contact area will be large.

In the monolith anion exchanger a, the material constituting the skeleton is an aromatic vinyl polymer containing 0.1 to 5.0 mol %, preferably 0.5 to 3.0 mol %, of crosslinked structural units in all structural units, and is hydrophobic. If the crosslinked structural units are less than 0.1 mol %, the mechanical strength is insufficient, which is not preferable, while if the crosslinked structural units exceed 5 mol %, the structure of the porous body is likely to deviate from the co-continuous structure. There is no particular restriction on the type of aromatic vinyl polymer, and examples thereof include polystyrene, poly(α-methylstyrene), polyvinyltoluene, polyvinylbenzyl chloride, polyvinylbiphenyl, and polyvinylnaphthalene. The above polymer may be a polymer obtained by copolymerizing a single vinyl monomer and a crosslinking agent, or a polymer obtained by polymerizing multiple vinyl monomers and a crosslinking agent, or may be a blend of two or more types of polymers. Among these organic polymer materials, styrene-divinylbenzene copolymers and vinylbenzyl chloride-divinylbenzene copolymers are preferred because of the ease of forming a co-continuous structure, the ease of introducing anion exchange groups, high mechanical strength, and high stability against acids or alkalis.

The anion exchange group (negative ion exchange group) introduced into the monolith anion exchanger a may be one or more selected from quaternary ammonium groups such as trimethylammonium groups, triethylammonium groups, tributylammonium groups, dimethylhydroxyethylammonium groups, dimethylhydroxypropylammonium groups, and methyldihydroxyethylammonium groups, tertiary sulfonium groups, and phosphonium groups.

The anion exchange groups introduced into the monolith anion exchanger a are distributed uniformly not only on the surface of the porous body but also inside the skeleton of the porous body.

Monolith anion exchanger a has an anion exchange capacity of 0.2 to 1.0 mg equivalent/mL (in a water-wet state) per volume when wetted with water. Monolith anion exchanger a has high continuity and uniformity of three-dimensionally connected pores, allowing the substrate and solvent to diffuse uniformly. This allows the reaction to proceed quickly. Having an anion exchange capacity in the above range results in high removal performance and a long life.

<Method of producing monolith a and monolith anion exchanger a>
Monolith a can be obtained by carrying out the following steps: Step I, in which a water-in-oil emulsion is prepared by stirring a mixture of an oil-soluble monomer not containing an ion exchange group, a surfactant, and water, and then the water-in-oil emulsion is polymerized to obtain a monolithic organic porous intermediate (monolith intermediate a) having a continuous macropore structure with a total pore volume exceeding 16 mL/g and not exceeding 30 mL/g; Step II, in which a mixture is prepared consisting of an aromatic vinyl monomer, 0.3 to 5 mol % of a crosslinking agent in all oil-soluble monomers having at least two or more vinyl groups in one molecule, an organic solvent in which the aromatic vinyl monomer and the crosslinking agent are soluble but not a polymer produced by polymerization of the aromatic vinyl monomer, and a polymerization initiator; and Step III, in which the mixture obtained in Step II is allowed to stand and is polymerized in the presence of the monolith intermediate a obtained in Step I to obtain monolith a, which is an organic porous body having a co-continuous structure.

In the above-mentioned method for producing monolith a, step I for obtaining monolith intermediate a may be carried out in accordance with the method described in JP-A-2002-306976.

That is, in step I of the manufacturing method of monolith a, examples of oil-soluble monomers that do not contain ion exchange groups include monomers that do not contain ion exchange groups such as carboxylic acid groups, sulfonic acid groups, tertiary amino groups, and quaternary ammonium groups, have low solubility in water, and are lipophilic. Specific examples of these monomers include aromatic vinyl monomers such as styrene, α-methylstyrene, vinyltoluene, vinylbenzyl chloride, vinylbiphenyl, and vinylnaphthalene; α-olefins such as ethylene, propylene, 1-butene, and isobutene; diene monomers such as butadiene, isoprene, and chloroprene; halogenated olefins such as vinyl chloride, vinyl bromide, vinylidene chloride, and tetrafluoroethylene; nitrile monomers such as acrylonitrile and methacrylonitrile; vinyl esters such as vinyl acetate and vinyl propionate; and (meth)acrylic monomers such as methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, 2-ethylhexyl methacrylate, cyclohexyl methacrylate, benzyl methacrylate, and glycidyl methacrylate. Among these monomers, preferred are aromatic vinyl monomers, such as styrene, α-methylstyrene, vinyltoluene, vinylbenzyl chloride, and divinylbenzene. These monomers can be used alone or in combination of two or more. However, it is preferable to select a crosslinkable monomer such as divinylbenzene or ethylene glycol dimethacrylate as at least one component of the oil-soluble monomer and set its content to 0.3 to 5 mol%, preferably 0.3 to 3 mol%, of the total oil-soluble monomers, because this is advantageous for the formation of a co-continuous structure.

The surfactant used in step I of the manufacturing method of monolith a is not particularly limited as long as it can form a water-in-oil (W/O) emulsion when an oil-soluble monomer not containing an anion exchange group is mixed with water. Examples of the surfactant include nonionic surfactants such as sorbitan monooleate, sorbitan monolaurate, sorbitan monopalmitate, sorbitan monostearate, sorbitan trioleate, polyoxyethylene nonylphenyl ether, polyoxyethylene stearyl ether, and polyoxyethylene sorbitan monooleate; anionic surfactants such as potassium oleate, sodium dodecylbenzenesulfonate, and dioctyl sodium sulfosuccinate; cationic surfactants such as distearyl dimethyl ammonium chloride; and amphoteric surfactants such as lauryl dimethyl betaine. These surfactants can be used alone or in combination of two or more. The water-in-oil emulsion refers to an emulsion in which the oil phase is the continuous phase and water droplets are dispersed therein. The amount of the surfactant added cannot be generalized because it varies greatly depending on the type of oil-soluble monomer and the size of the desired emulsion particles (macropores), but it can be selected in the range of about 2 to 70% of the total amount of the oil-soluble monomer and surfactant.

In step I of the manufacturing method of monolith a, a polymerization initiator may be used as necessary when forming a water-in-oil emulsion. The polymerization initiator is preferably a compound that generates radicals when exposed to heat or light. The polymerization initiator may be water-soluble or oil-soluble, and examples of the polymerization initiator include 2,2'-azobis(isobutyronitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), 2,2'-azobis(2-methylbutyronitrile), 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), 2,2'-azobisdimethylisobutyrate, 4,4'-azobis(4-cyanovaleric acid), 1,1'-azobis(cyclohexane-1-carbonitrile), benzoyl peroxide, lauroyl peroxide, potassium persulfate, ammonium persulfate, tetramethylthiuram disulfide, hydrogen peroxide-ferrous chloride, sodium persulfate-acidic sodium sulfite, etc.

In step I of the manufacturing method of monolith a, the oil-soluble monomer not containing an ion exchange group, the surfactant, water and the polymerization initiator are mixed to form a water-in-oil type emulsion. There are no particular limitations on the mixing method, and it is possible to mix each component all at once, or to dissolve the oil-soluble components, i.e., the oil-soluble monomer, the surfactant and the oil-soluble polymerization initiator, and the water-soluble components, i.e., water and the water-soluble polymerization initiator, uniformly separately and then mix each component. There are no particular limitations on the mixing device for forming the emulsion, and a normal mixer, homogenizer, high-pressure homogenizer, etc. can be used, and it is sufficient to select a device appropriate for obtaining the desired emulsion particle size. There are also no particular limitations on the mixing conditions, and the stirring speed and stirring time that can obtain the desired emulsion particle size can be set as desired.

The monolith intermediate a obtained in step I of the manufacturing method of monolith a is an organic polymer material having a crosslinked structure, preferably an aromatic vinyl polymer. The crosslink density of the polymer material is not particularly limited, but it is preferable that the polymer material contains 0.1 to 5 mol %, preferably 0.3 to 3 mol %, of crosslinked structural units relative to the total structural units constituting the polymer material. If the crosslinked structural units are less than 0.3 mol %, the mechanical strength will be insufficient, which is not preferable. On the other hand, if the crosslinked structural units exceed 5 mol %, the structure of the obtained monolith will tend to deviate from the co-continuous structure, which is not preferable. In particular, when the total pore volume is 16 to 20 ml/g, it is preferable that the crosslinked structural units are less than 3 mol % in order to form a co-continuous structure.

In step I of the method for producing monolith a, the type of polymer material of monolith intermediate a is not particularly limited, and examples thereof include various organic polymers, for example, aromatic vinyl polymers such as polystyrene, poly(α-methylstyrene), polyvinyl toluene, polyvinyl benzyl chloride, polyvinyl biphenyl, and polyvinyl naphthalene; polyolefins such as polyethylene and polypropylene; poly(halogenated polyolefins) such as polyvinyl chloride and polytetrafluoroethylene; nitrile-based polymers such as polyacrylonitrile; and (meth)acrylic polymers such as polymethyl methacrylate, polyglycidyl methacrylate, and polyethyl acrylate.
The organic polymer may be a polymer obtained by copolymerizing a single vinyl monomer and a crosslinking agent, a polymer obtained by polymerizing a plurality of vinyl monomers and a crosslinking agent, or a blend of two or more polymers. Among these organic polymer materials, crosslinked polymers of aromatic vinyl polymers are preferred in view of the ease of forming a continuous macropore structure, the ease of introducing anion exchange groups, high mechanical strength, and high stability against acids or alkalis, and in particular, styrene-divinylbenzene copolymers and vinylbenzyl chloride-divinylbenzene copolymers are cited as preferred materials.

The total pore volume per weight of the monolith intermediate a obtained in step I of the manufacturing method of monolith a in a dry state is more than 16 mL/g and 30 mL/g or less, preferably more than 16 mL/g and 25 mL/g or less. That is, although this monolith intermediate a basically has a continuous macropore structure, the openings (mesopores) where the macropores overlap are significantly larger, so that the skeleton constituting the monolith structure has a structure that is as close as possible to a one-dimensional rod-like skeleton from the two-dimensional wall surface. Figure 3 shows an SEM photograph of an example of the form of monolith intermediate a, which has a skeleton close to a rod shape. When this is allowed to coexist in a polymerization system, a porous body with a cocontinuous structure is formed using the structure of monolith intermediate a as a mold. If the total pore volume is too small, the structure of the monolith obtained after polymerization of the vinyl monomer will change from a co-continuous structure to a continuous macropore structure, which is not preferable. On the other hand, if the total pore volume is too large, the mechanical strength of the monolith obtained after polymerization of the vinyl monomer will decrease, and if an anion exchange group is introduced, the anion exchange capacity per volume will decrease, which is not preferable. In order to set the total pore volume of the monolith intermediate a within the above range, the ratio of monomer to water should be approximately 1:20 to 1:40.

In addition, the monolith intermediate a obtained in step I of the manufacturing method of the monolith a has an average diameter of the openings (mesopores) at the overlapping portions of the macropores, which is 5 to 100 μm in a dry state. If the average diameter of the openings is less than 5 μm in a dry state, the opening diameter of the monolith obtained after polymerization of the vinyl monomer becomes small, which is undesirable because the pressure loss during fluid transmission becomes large. On the other hand, if it exceeds 100 μm, the opening diameter of the monolith obtained after polymerization of the vinyl monomer becomes too large, which is undesirable because the contact between the treated liquid and the monolith anion exchanger becomes insufficient, which results in a decrease in removal performance. The monolith intermediate a is preferably one having a uniform structure with uniform macropore size and opening diameter, but is not limited thereto, and may be one having a uniform structure in which non-uniform macropores larger than the uniform macropore size are scattered.

Step II in the manufacturing method of Monolith a is a step of preparing a mixture consisting of an aromatic vinyl monomer, 0.3 to 5 mol % of a crosslinking agent in all oil-soluble monomers having at least two vinyl groups in one molecule, an organic solvent that dissolves the aromatic vinyl monomer and the crosslinking agent but not the polymer produced by polymerization of the aromatic vinyl monomer, and a polymerization initiator.
The order of steps I and II does not matter, and step II may be performed after step I, or step I may be performed after step II.

The aromatic vinyl monomer used in step II of the manufacturing method of monolith a is not particularly limited as long as it is an aromatic vinyl monomer that contains a polymerizable vinyl group in the molecule and is lipophilic and highly soluble in organic solvents, but it is preferable to select a vinyl monomer that produces the same or similar polymer material as monolith intermediate a that is coexisted in the polymerization system. Specific examples of these vinyl monomers include styrene, α-methylstyrene, vinyltoluene, vinylbenzyl chloride, vinylbiphenyl, vinylnaphthalene, etc. These monomers can be used alone or in combination of two or more. The aromatic vinyl monomers that are preferably used are styrene, vinylbenzyl chloride, etc.

The amount of aromatic vinyl monomer used in step II of the method for producing monolith a is 5 to 50 times, preferably 5 to 40 times, by weight, relative to the amount of monolith intermediate a that is allowed to coexist during polymerization. If the amount of aromatic vinyl monomer added is less than 5 times that of monolith intermediate a, the rod-shaped skeleton cannot be made thicker, and when anion exchange groups are introduced, the anion exchange capacity per volume after the introduction of the anion exchange groups becomes small, which is not preferred. On the other hand, if the amount of aromatic vinyl monomer added is more than 50 times, the diameter of the continuous pores becomes small, which is not preferred, as it increases the pressure loss during liquid passage.

The crosslinking agent used in step II of the manufacturing method of monolith a preferably contains at least two polymerizable vinyl groups in the molecule and is highly soluble in an organic solvent. Specific examples of crosslinking agents include divinylbenzene, divinylnaphthalene, divinylbiphenyl, ethylene glycol dimethacrylate, trimethylolpropane triacrylate, butanediol diacrylate, etc. These crosslinking agents can be used alone or in combination of two or more. Preferred crosslinking agents are aromatic polyvinyl compounds such as divinylbenzene, divinylnaphthalene, and divinylbiphenyl, because of their high mechanical strength and stability against hydrolysis. The amount of crosslinking agent used is 0.3 to 5 mol%, particularly 0.3 to 3 mol%, based on the total amount of vinyl monomer and crosslinking agent (total oil-soluble monomer). If the amount of crosslinking agent used is less than 0.3 mol%, the mechanical strength of the monolith will be insufficient, which is not preferable, while if the amount is too large, it is not preferable because it may be difficult to quantitatively introduce anion exchange groups when introducing anion exchange groups. It is preferable to use the crosslinking agent in an amount that is approximately equal to the crosslink density of the monolith intermediate a that is coexistent during the vinyl monomer/crosslinking agent polymerization. If the amounts of the two used are too far apart, the crosslink density distribution in the produced monolith will be biased, and if an anion exchange group is introduced, cracks will be more likely to occur during the anion exchange group introduction reaction.

The organic solvent used in step II of the manufacturing method of monolith a is an organic solvent in which aromatic vinyl monomers and crosslinking agents dissolve but not the polymer produced by polymerization of aromatic vinyl monomers, in other words, it is a poor solvent for the polymer produced by polymerization of aromatic vinyl monomers. Since the organic solvent varies greatly depending on the type of aromatic vinyl monomer, it is difficult to list general specific examples. For example, when the aromatic vinyl monomer is styrene, examples of the organic solvent include alcohols such as methanol, ethanol, propanol, butanol, hexanol, cyclohexanol, octanol, 2-ethylhexanol, decanol, dodecanol, propylene glycol, and tetramethylene glycol; linear (poly)ethers such as diethyl ether, butyl cellosolve, polyethylene glycol, polypropylene glycol, and polytetramethylene glycol; linear saturated hydrocarbons such as hexane, heptane, octane, isooctane, decane, and dodecane; and esters such as ethyl acetate, isopropyl acetate, cellosolve acetate, and ethyl propionate. In addition, even if a good solvent for polystyrene, such as dioxane, THF, or toluene, is used together with the poor solvent and in a small amount, it can be used as an organic solvent. The amount of these organic solvents used is preferably such that the concentration of the aromatic vinyl monomer is 30 to 80% by weight. If the amount of organic solvent used deviates from the above range and the aromatic vinyl monomer concentration is less than 30% by weight, this is not preferable because the polymerization rate decreases and the monolith structure after polymerization deviates from the range of monolith a. On the other hand, if the aromatic vinyl monomer concentration exceeds 80% by weight, this is not preferable because there is a risk of runaway polymerization.

The polymerization initiator used in step II of the manufacturing method of monolith a is preferably a compound that generates radicals by heat or light irradiation. It is preferable that the polymerization initiator is oil-soluble. Specific examples of polymerization initiators include 2,2'-azobis(isobutyronitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), 2,2'-azobis(2-methylbutyronitrile), 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), 2,2'-azobisisobutyric acid dimethyl, 4,4'-azobis(4-cyanovaleric acid), 1,1'-azobis(cyclohexane-1-carbonitrile), benzoyl peroxide, lauroyl peroxide, potassium persulfate, ammonium persulfate, tetramethylthiuram disulfide, etc. The amount of polymerization initiator used varies greatly depending on the type of monomer, polymerization temperature, etc., but can be used in the range of about 0.01 to 5% of the total amount of vinyl monomer and crosslinking agent.

In step III of the method for producing monolith a, the mixture obtained in step II is left to stand while being polymerized in the presence of monolith intermediate a obtained in step I, and the continuous macropore structure of monolith intermediate a is changed to a co-continuous structure to obtain monolith a, which is a co-continuous structure monolith. Monolith intermediate a used in step III plays an extremely important role in creating a monolith having the structure of the present invention. As disclosed in JP-T-7-501140 and the like, when a vinyl monomer and a crosslinking agent are polymerized in a specific organic solvent in the absence of monolith intermediate a, a particle-aggregated monolithic organic porous material is obtained. In contrast, when monolith intermediate a with a specific continuous macropore structure is present in the above polymerization system as in monolith a, the structure of the monolith after polymerization changes dramatically, the particle-aggregated structure disappears, and monolith a with the above-mentioned co-continuous structure is obtained. The reason for this has not been elucidated in detail, but in the absence of monolith intermediate a, the crosslinked polymer produced by polymerization precipitates and settles in particulate form, forming a particle aggregate structure, whereas in the presence of a porous body (intermediate) with a large total pore volume in the polymerization system, the vinyl monomer and crosslinking agent are adsorbed or distributed from the liquid phase to the skeleton of the porous body, polymerization proceeds within the porous body, and the skeleton that constitutes the monolith structure changes from a two-dimensional wall surface to a one-dimensional rod-like skeleton, forming monolith a with a co-continuous structure.

In the method for producing monolith a, the internal volume of the reaction vessel is not particularly limited as long as it is large enough to allow the monolith intermediate a to exist in the reaction vessel. When the monolith intermediate a is placed in the reaction vessel, it may be either one in which there is a gap around the monolith in a plan view, or one in which the monolith intermediate a fits into the reaction vessel without any gaps. Of these, if the thick monolith after polymerization fits into the reaction vessel without any gaps without being pressed by the inner wall of the vessel, the monolith does not become distorted and there is no waste of reaction raw materials, etc., which is efficient. Even if the internal volume of the reaction vessel is large and there are gaps around the monolith after polymerization, the vinyl monomer and crosslinking agent are adsorbed and distributed to the monolith intermediate a, so that particle aggregate structures do not form in the gaps in the reaction vessel.

In step III of the method for producing monolith a, monolith intermediate a is placed in a reaction vessel in a state of being impregnated with the mixture (solution). As described above, the mixture obtained in step II and monolith intermediate a are preferably mixed in such a ratio that the amount of vinyl monomer added is 3 to 50 times, preferably 4 to 40 times, by weight, relative to monolith intermediate a. This makes it possible to obtain monolith a having a suitable opening diameter and a thick skeleton. In the reaction vessel, the vinyl monomer and crosslinking agent in the mixture are adsorbed and distributed to the skeleton of the stationary monolith intermediate, and polymerization proceeds within the skeleton of monolith intermediate a.

In step III of the method for producing monolith a, monolith intermediate a is placed in a reaction vessel in a state of being impregnated with the mixture (solution). As described above, the mixture obtained in step II and monolith intermediate a are preferably mixed in such a ratio that the amount of aromatic vinyl monomer added is 5 to 50 times, preferably 5 to 40 times, by weight, relative to monolith intermediate a. This makes it possible to obtain monolith a with a bicontinuous structure in which pores of appropriate size are three-dimensionally continuous and a thick skeleton is three-dimensionally continuous. In the reaction vessel, the aromatic vinyl monomer and crosslinking agent in the mixture are adsorbed and distributed to the skeleton of monolith intermediate a, which is left stationary, and polymerization proceeds within the skeleton of monolith intermediate a.

The polymerization conditions for step III in the manufacturing method of monolith a are selected according to the type of monomer and the type of initiator. For example, when 2,2'-azobis(isobutyronitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), benzoyl peroxide, lauroyl peroxide, potassium persulfate, or the like is used as the initiator, the polymerization can be carried out by heating at 30 to 100°C for 1 to 48 hours in a sealed container under an inert atmosphere. By the thermal polymerization, the vinyl monomer and crosslinking agent adsorbed and distributed to the skeleton of monolith intermediate a are polymerized within the skeleton, thickening the skeleton. After the polymerization is completed, the contents are removed and extracted with a solvent such as acetone to remove the unreacted vinyl monomer and organic solvent, to obtain monolith a.

The monolith anion exchanger a can be obtained by subjecting the monolith a obtained in the step III to the step IV in which an anion exchange group is introduced.
The method for introducing anion exchange groups into the monolith a is not particularly limited, and known methods such as polymer reaction and graft polymerization can be used.
For example, examples of methods for introducing quaternary ammonium groups include, if the monolith is a styrene-divinylbenzene copolymer or the like, a method in which chloromethyl groups are introduced using chloromethyl methyl ether or the like, followed by reaction with a tertiary amine; a method in which a monolith is produced by copolymerizing chloromethylstyrene and divinylbenzene, followed by reaction with a tertiary amine; a method in which radical initiation groups or chain transfer groups are uniformly introduced into the surface and interior of the skeleton of a monolith, followed by graft polymerization of N,N,N-trimethylammonium ethyl acrylate or N,N,N-trimethylammonium propyl acrylamide; and a method in which glycidyl methacrylate is graft polymerized in a similar manner, followed by introduction of quaternary ammonium groups by functional group conversion.
Among these methods, the method of introducing quaternary ammonium groups is preferably a method of introducing chloromethyl groups into a styrene-divinylbenzene copolymer using chloromethyl methyl ether or the like, followed by reaction with a tertiary amine, or a method of producing a monolith by copolymerizing chloromethylstyrene with divinylbenzene, followed by reaction with a tertiary amine, since ion exchange groups can be introduced uniformly and quantitatively. Examples of the ion exchange groups to be introduced include quaternary ammonium groups such as trimethylammonium groups, triethylammonium groups, tributylammonium groups, dimethylhydroxyethylammonium groups, dimethylhydroxypropylammonium groups, and methyldihydroxyethylammonium groups, as well as tertiary sulfonium groups and phosphonium groups.

Although the size of the three-dimensionally continuous pores in Monolith A and Monolith Anion Exchanger A is significantly larger, they have a thick skeleton and therefore high mechanical strength. In addition, because Monolith Anion Exchanger A has a thick skeleton, it is possible to increase the cation exchange capacity per volume when wet with water, and furthermore, it is possible to pass the liquid to be treated through it at low pressure and at a large flow rate for a long period of time.

<Anion exchange resin (negative ion exchange resin)>
In the present invention, when the anion exchanger is an anion exchange resin (anion exchange resin), the anion exchange resin is not particularly limited, but is preferably an organic polymer-based resin having an organic polymer as a parent body, and examples of the parent organic polymer include a styrene-based resin and an acrylic-based resin.

In this application, styrene-based resin means a resin containing 50% by mass or more of structural units derived from styrene or a styrene derivative, either homopolymerized or copolymerized with styrene or a styrene derivative.

Examples of the styrene derivatives include α-methylstyrene, vinyltoluene, chlorostyrene, ethylstyrene, i-propylstyrene, dimethylstyrene, and bromostyrene.

As for styrene-based resins, as long as the main component is a homopolymer or copolymer of styrene or a styrene derivative, it may be a copolymer with other copolymerizable vinyl monomers. Examples of such vinyl monomers include one or more selected from polyfunctional monomers such as divinylbenzenes such as o-divinylbenzene, m-divinylbenzene, and p-divinylbenzene, alkylene glycol di(meth)acrylates such as ethylene glycol di(meth)acrylate and polyethylene glycol di(meth)acrylate, (meth)acrylonitrile, methyl (meth)acrylate, etc.

The other copolymerizable vinyl monomers are preferably ethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate having an ethylene polymerization number of 4 to 16, and divinylbenzene, more preferably divinylbenzene and ethylene glycol di(meth)acrylate, and even more preferably divinylbenzene.

In this application, acrylic resin means a resin that is homopolymerized or copolymerized with one or more selected from acrylic acid, methacrylic acid, acrylic acid esters, and methacrylic acid esters, and contains 50% by mass or more of structural units selected from structural units derived from acrylic acid, structural units derived from methacrylic acid, structural units derived from acrylic acid esters, and structural units derived from methacrylic acid esters.

More specifically, the acrylic resin may be one or more selected from the group consisting of 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.), 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.), 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.), 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 these, methacrylic acid-divinylbenzene copolymers or acrylic acid-divinylbenzene copolymers are preferred.

The acrylic acid ester is preferably an alkyl acrylate, more preferably a linear or branched alkyl ester of acrylic acid, and even more preferably a linear alkyl ester of acrylic acid.
As the acrylic ester, an alkyl acrylate having an alkyl group contained in the alkyl ester moiety having 1 to 4 carbon atoms is more preferred, methyl acrylate and ethyl acrylate are more preferred, and methyl acrylate is particularly preferred.

As the methacrylic acid ester, a methacrylic acid alkyl ester is preferable, a linear alkyl ester or a branched alkyl ester of methacrylic acid is more preferable, and a linear alkyl ester of methacrylic acid is further preferable.
As the methacrylic acid ester, a methacrylic acid alkyl ester in which the alkyl group contained in the alkyl ester moiety has 1 to 4 carbon atoms is more preferable, methyl methacrylate and ethyl methacrylate are further preferable, and methyl methacrylate is particularly preferable.

Examples of the anion exchange resin include strongly basic resins having quaternary ammonium groups as anion exchange groups, and weakly basic resins having amino groups as anion exchange groups.
In the pretreatment device for ion exchange resin according to the present invention, the ion exchange resin through which the non-aqueous solvent contained in the ion exchange resin container is passed is preferably a weakly basic ion exchange resin.

The weakly basic ion exchange groups that make up the weakly basic ion exchange resin are preferably primary to tertiary amino groups.

Such anion exchange resins may be commercially available products, for example, one or more selected from Diaion WA30 manufactured by Mitsubishi Chemical Corporation and ORLITE DS-6 manufactured by Organo Corporation.

The anion exchange resin may have a gel structure, a macroreticular (MR) structure, a macroporous (MP) structure, or a porous structure.

The size of the anion exchange resin is not particularly limited, but the harmonic mean diameter is preferably 300 to 1000 μm, more preferably 400 to 800 μm, and even more preferably 500 to 700 μm.

The anion exchange resin preferably has a total ion exchange capacity in a wet state of 0.1 to 3.0 (eq/L-R), more preferably 0.5 to 2.5 (eq/L-R), and even more preferably 1.0 to 2.0 (eq/L-R).

In the present invention, the form in which the anion exchanger is contained is not particularly limited as long as it is in a form that allows it to come into contact with an aqueous solution of a quaternary ammonium hydroxide, which will be described later.
For example, the anion exchanger may be contained in the form of a column or tank packed so that an aqueous solution of a quaternary ammonium hydroxide can pass through.
The column or tank may be equipped with a pump for passing the aqueous solution of the quaternary ammonium hydroxide through the column or tank.

<Changes in ion type of anion exchanger>
In the present invention, the anion exchanger used for purifying the above-mentioned ultrapure water or purifying the chemical solution is brought into contact with an aqueous solution of a quaternary ammonium hydroxide.
In the present invention, the anion exchanger is brought into contact with the aqueous solution of a quaternary ammonium hydroxide in the following manner (a) to (c).
(Aspect (a))
The anion exchanger is contacted with an aqueous solution of a quaternary ammonium hydroxide to change the ionic form of the anion exchanger.
(Aspect (b))
The anion exchanger is contacted with a mineral acid, then washed with water, and then contacted with an aqueous solution of a quaternary ammonium hydroxide to change the ionic form of the anion exchanger.
(Aspect (c))
An embodiment in which the anion exchanger is contacted with a mineral acid, then washed with water, then contacted with hydrochloric acid, then washed with water, and then contacted with the aqueous solution of the quaternary ammonium hydroxide.
According to any one of the above-mentioned embodiments (a) to (c), the ionic form of the anion exchanger can be effectively changed to the OH form.
In the present invention, it is preferable to change the ionic form of the anion exchanger according to embodiment (b) or embodiment (c), and it is more preferable to change the ionic form of the anion exchanger according to embodiment (c).
The following description will be given regarding matters common to aspects (a) to (c) unless otherwise specified.

（式中、Ｒ^１～Ｒ^４は、各々水酸基を有していてもよい炭素数１～４の炭化水素基であり、互いに同一であっても異なっていてもよい。）
で表される化合物から選ばれる一種以上であることが好ましい。 As exemplified in the above-mentioned embodiments (a) to (c), in the present invention, the anion exchanger is contacted with an aqueous solution of a quaternary ammonium hydroxide.
<Quaternary ammonium hydroxide>
The quaternary ammonium hydroxide may be represented by the following general formula (I):

(In the formula, R ¹ to R ⁴ are each a hydrocarbon group having 1 to 4 carbon atoms which may have a hydroxyl group, and may be the same or different.)
It is preferable that the compound is one or more selected from the compounds represented by the following formula:

Examples of R ¹ to R ⁴ include linear or branched hydrocarbon groups which may have a hydroxyl group, such as a methyl group, an ethyl group, an n-propyl group, an isopropyl group, and a butyl group.
R ¹ to R ⁴ may be the same or different.

Specific examples of the compound represented by the following general formula (I) include one or more selected from trimethylhydroxyammonium, tetramethylammonium hydroxide (TMAH), trimethylhydroxyethylammonium hydroxide (choline), methyltrihydroxyethylammonium hydroxide, dimethyldihydroxyethylammonium hydroxide, tetraethylammonium hydroxide, trimethylethylammonium hydroxide, tetrabutylammonium hydroxide (TBAH), etc.

In the present invention, the concentration of the quaternary ammonium hydroxide in the aqueous solution of the quaternary ammonium hydroxide is preferably 0.1 to 2.0N, more preferably 0.5 to 2.0N, and even more preferably 0.5 to 1.0N.
In the present invention, the concentration of metal impurities in the aqueous solution of the quaternary ammonium hydroxide is preferably 1000 ng/L or less, and more preferably 100 ng/L or less.
In the present application, the concentration of metal impurities refers to a value measured by inductively coupled plasma mass spectrometry (ICP-MS, Agilent 7500cs, manufactured by Agilent Technologies, Inc.).

In the present invention, the flow rate (liquid hourly space velocity) of the aqueous solution of quaternary ammonium hydroxide through the anion exchanger is not particularly limited as long as it is a rate at which the counter ions of the anion exchange groups constituting the anion exchanger can be converted to the OH form.

In the present invention, the aqueous solution of quaternary ammonium hydroxide is preferably passed through the anion exchanger at a liquid hourly space velocity (SV) (flow rate/anion exchanger volume ratio) of 20,000 h ^-1 or less, more preferably 10 to 4,000 h ^-1 , and even more preferably 300 to 1,000 h ^-1 .

In the present invention, the amount of the aqueous solution of quaternary ammonium hydroxide passed through the anion exchanger is preferably 5 to 100 times, more preferably 10 to 100 times, and even more preferably 15 to 75 times, by volume.

In the present invention, it is preferable to pass an aqueous solution of quaternary ammonium hydroxide through the anion exchanger contained in a container in an upward or downward flow manner to bring the two into contact with each other, and it is more preferable to pass an aqueous solution of quaternary ammonium hydroxide through the anion exchanger contained in a container in an upward flow manner to bring the two into contact with each other.

For example, as shown in FIG. 4, a liquid passing process may be used in which an aqueous solution S of quaternary ammonium hydroxide stored in a tank 4 is passed through a container 3 containing the anion exchanger in an upward flow direction from the bottom to the top using a pump P, and the discharged liquid W is then stored in a storage tank 5.

By passing the aqueous solution of quaternary ammonium hydroxide through the anion exchanger contained in the container 3 in an upward direction, even if air bubbles or the like become mixed into the anion exchanger contained in the container 3, the air bubbles in the anion exchanger can be removed by degassing the aqueous solution of quaternary ammonium hydroxide as it flows upward through the anion exchanger.
Therefore, even if air bubbles or the like are mixed into the anion exchanger, the ionic form of the anion exchanger can be changed to the OH form at a high rate, easily, and in a short time while maintaining favorable contact between the aqueous solution of the quaternary ammonium hydroxide and the anion exchanger.

In the present invention, as exemplified in the above-mentioned embodiments (b) and (c), it is preferable to contact the anion exchanger with a mineral acid prior to contacting it with the aqueous solution of a quaternary ammonium hydroxide.
The mineral acid may be one or more selected from nitric acid, hydrochloric acid, sulfuric acid, etc., and is preferably one or more selected from nitric acid and hydrochloric acid, and more preferably nitric acid.

In the present invention, the concentration of the mineral acid is preferably 0.1 to 2.0N, more preferably 0.5 to 2.0N, and even more preferably 0.5 to 1.0N.
In the present invention, the concentration of metal impurities in the mineral acid is preferably 100 ng/L or less, and more preferably 10 ng/L or less.

In the present invention, the mineral acid is preferably passed through the anion exchanger at a liquid hourly space velocity (SV) (flow rate/anion exchanger volume ratio) of 20,000 h ^-1 or less, more preferably 10 to 4,000 h ^-1 , and even more preferably 300 to 1,000 h ^-1 .

In the present invention, the amount of mineral acid passed through the anion exchanger is preferably 5 to 100 times, more preferably 10 to 100 times, and even more preferably 15 to 75 times, by volume.

In the present invention, it is preferable to pass the mineral acid through the anion exchanger contained in a container in an upward or downward flow manner to bring them into contact with each other, and it is more preferable to pass the mineral acid through the anion exchanger contained in a container in an upward flow manner to bring them into contact with each other.
In this case, specifically, a contact mode can be mentioned in which the mineral acid stored in a tank is passed in an upward flow manner from the bottom to the top of a container containing the anion exchanger by using a pump P, similar to the mode shown in FIG. 4 described above.

The anion exchanger that has been contacted with the mineral acid is then washed with water.
The above-mentioned washing treatment with water is not particularly limited in terms of the liquid passing speed or time, so long as it is possible to flush out the excess mineral acid present in the anion exchanger.

In the above-mentioned embodiment (b), the anion exchanger which has been contacted with a mineral acid by the above-mentioned method and then washed with water is contacted with an aqueous solution of a quaternary ammonium hydroxide.
The details of the method for contacting the anion exchanger with the aqueous solution of a quaternary ammonium hydroxide are the same as those described above.

In embodiment (b) of the present invention, at least a portion of the anions constituting the anion exchanger can be converted to the corresponding ionic form by contacting the anion exchanger with a mineral acid, and then, by contacting the anion exchanger with an aqueous solution of a quaternary ammonium hydroxide, a high proportion of the anions can be converted to the OH form (hydroxide ion) easily and in a short time.
For example, in embodiment (b) of the present invention, by contacting the anion exchanger with nitric acid or hydrochloric acid, at least a portion of the anions constituting the anion exchanger can be replaced with nitrate ions or chloride ions, and then by contacting the anion exchanger with an aqueous solution of a quaternary ammonium hydroxide, the nitric acid form (nitrate ions) or hydrochloric acid form (chloride ions) can be easily and quickly converted to the OH form (hydroxide ions) at a high rate.

In the present invention, as exemplified in the above-mentioned embodiment (c), it is preferable to contact the anion exchanger with a mineral acid, then wash with water, then contact with hydrochloric acid, then wash with water, and then contact with the aqueous solution of the quaternary ammonium hydroxide.

The details of the method for contacting the anion exchanger with a mineral acid and then washing with water are the same as described above.

The anion exchanger that has been contacted with the mineral acid and then washed with water is then contacted with hydrochloric acid and then washed with water.

In the present invention, the concentration of the hydrochloric acid (which is contacted with the mineral acid and then washed with water) is preferably 0.1 to 2.0N, more preferably 0.5 to 2.0N, and even more preferably 1.0 to 2.0N.
In the present invention, the content of metal impurities in the hydrochloric acid is preferably 100 ng/L or less, and more preferably 10 ng/L or less.

In the present invention, hydrochloric acid is passed through the anion exchanger at a liquid hourly space velocity (SV) (flow rate/anion exchanger volume ratio) of preferably 20,000 h ^-1 or less, more preferably 10 to 4,000 h ^-1 , and even more preferably 300 to 1,000 h ^-1 .

In the present invention, the amount of hydrochloric acid passed through the anion exchanger is preferably 5 to 100 times, more preferably 10 to 100 times, and even more preferably 15 to 75 times.

In the present invention, it is preferable to pass hydrochloric acid through the anion exchanger contained in a container in an upward or downward flow manner to bring the two into contact with each other, and it is more preferable to pass hydrochloric acid through the anion exchanger contained in a container in an upward flow manner to bring the two into contact with each other.
In this case, specifically, a contact mode can be mentioned in which hydrochloric acid stored in a tank is passed in an upward flow manner from the bottom to the top of a container containing the anion exchanger by using a pump P, similar to the mode shown in FIG. 4 described above.

The anion exchanger that has been contacted with the hydrochloric acid is then washed with water.
The above-mentioned washing treatment with water is not particularly limited in terms of the flow rate or time, so long as it is possible to flush out the excess hydrochloric acid present in the anion exchanger.

In the above-mentioned embodiment (c), the anion exchanger which has been contacted with a mineral acid by the above-mentioned method, then washed with water, and then further contacted with hydrochloric acid and then washed with water, is contacted with an aqueous solution of a quaternary ammonium hydroxide.
The details of the method for contacting the anion exchanger with the aqueous solution of a quaternary ammonium hydroxide are the same as those described above.

In embodiment (c) of the present invention, the anion exchanger is initially washed with a mineral acid, and then contacted with hydrochloric acid to reduce the metal content of the anion exchanger, and at least some of the anions constituting the anion exchanger can be replaced with chloride ions. Then, by contacting the anion exchanger with an aqueous solution of a quaternary ammonium hydroxide, the hydrochloric acid form (chloride ions) can be easily and quickly converted to the OH form (hydroxide ions) at a high rate.

Next, the mode of use of the anion exchanger regenerated by the present invention will be described.
5(a) shows a purification apparatus U which is installed downstream of any use point to which ultrapure water is supplied in various manufacturing processes and is connected so as to be capable of passing water to a container A containing an anion exchanger and a container C containing a cation exchanger. In the embodiment shown in Fig. 5(a), ultrapure water flows in from one end of the container A, flows through the containers A and C, and then flows out from the opposite end of the container C.
By loading the anion exchanger regenerated by the present invention into the above-mentioned vessel A, even if metal components remain in the anion exchanger during regeneration and such metal components flow out, they can be easily removed by the cation exchanger placed downstream of the anion exchanger.
5(b) shows a purification apparatus U in which a container C containing a cation exchanger and a container A containing an anion exchanger, which are incorporated downstream of any use point to which ultrapure water is supplied in various manufacturing processes, are connected so as to be able to pass water therethrough. In the embodiment shown in Fig. 5(b), ultrapure water flows in from one end of the container C, flows through the containers C and A, and then flows out from the opposite end of the container C.
The anion exchanger regenerated by the present invention has a highly reduced amount of residual metals at the time of regeneration, and therefore, even when a container A containing an anion exchanger regenerated by the present invention is placed downstream of a container C containing a cation exchanger, the outflow of various metals from the anion exchanger can be highly suppressed. Furthermore, even if negatively charged fine powder flows out from the cation exchanger in container C, it can be easily removed by the anion exchanger in container A placed downstream.

The present invention provides a method for easily and quickly changing the ionic form of an anion exchanger to the OH form at a high rate while suppressing the residual presence of various metals.

Next, the method for producing the anion exchanger according to the present invention will be described.
The method for producing an anion exchanger according to the present invention is characterized in that, in the production of an anion exchanger for use in the purification of ultrapure water or in the purification of chemical solutions, the anion exchanger is brought into contact with an aqueous solution of a quaternary ammonium hydroxide in order to change the ion form.

The method for producing an anion exchanger according to the present invention is to apply the method for changing the ion form of an anion exchanger according to the present invention in order to change the ion form of an anion exchanger used for purifying ultrapure water or purifying chemicals, i.e., during the preparation or regeneration of an anion exchanger used for removing anionic impurities in ultrapure water or chemicals.
In the method for producing an anion exchanger according to the present invention, the details of the anion exchanger to be produced and the method for changing the ion form are as described above in the description of the method for changing the ion form of an anion exchanger according to the present invention.

The present invention provides a method for producing an anion exchanger that can easily and quickly change the ionic form of the anion exchanger to the OH form at a high rate while suppressing the residual amount of various metals.

Next, the present invention will be explained in more detail with reference to examples, but these are merely illustrative and do not limit the present invention.

A monolithic anion exchanger and a monolithic cation exchanger were produced in the same manner as in Reference Example 17 of the Examples of the specification of JP-A-2010-234357.
(Reference Example 1)
<Production of monolithic anion exchanger and monolithic cation exchanger>
(Step I: Production of monolith intermediate)
5.4 g of styrene, 0.17 g of divinylbenzene, 1.4 g of sorbitan monooleate (hereinafter abbreviated as SMO), and 0.26 g of 2,2'-azobis(isobutyronitrile) were mixed and uniformly dissolved. Next, the styrene/divinylbenzene/SMO/2,2'-azobis(isobutyronitrile) mixture was added to 180 g of pure water, and stirred under reduced pressure at a temperature range of 5 to 20 ° C using a planetary stirring device, a vacuum stirring and degassing mixer (manufactured by EME Co., Ltd.) to obtain a water-in-oil emulsion. This emulsion was quickly transferred to a reaction vessel, sealed, and polymerized at 60 ° C for 24 hours under static conditions. After the polymerization was completed, the contents were removed, extracted with methanol, and then dried under reduced pressure to produce a monolith intermediate having a continuous macropore structure. When the internal structure of the monolith intermediate (dried body) obtained in this manner was observed using SEM images, it was found that the walls separating two adjacent macropores were extremely thin and rod-shaped but had an open-cell structure, and the average diameter of the openings (mesopores) where the macropores overlapped, as measured by mercury intrusion porosimetry, was 70 μm, and the total pore volume was 21.0 ml/g.

(Production of bicontinuous structure monolith)
Next, 76.0 g of styrene, 4.0 g of divinylbenzene, 120 g of 1-decanol, and 0.8 g of 2,2'-azobis(2,4-dimethylvaleronitrile) were mixed and dissolved uniformly (II step). Next, the monolith intermediate was cut into a disk shape with a diameter of 70 mm and a thickness of about 40 mm, and 4.1 g was taken out. The taken out monolith intermediate was placed in a reaction vessel with an inner diameter of 110 mm, immersed in the styrene/divinylbenzene/1-decanol/2,2'-azobis(2,4-dimethylvaleronitrile) mixture, degassed in a vacuum chamber, sealed the reaction vessel, and polymerized at 60°C for 24 hours under static conditions. After the polymerization was completed, the monolith-shaped contents with a thickness of about 60 mm were taken out, extracted with acetone by Soxhlet extraction, and then dried overnight at 85°C under reduced pressure (III step).

When the internal structure of the monolith (dried body) thus obtained, which contained 3.2 mol% of a crosslinking component consisting of a styrene/divinylbenzene copolymer, was observed by SEM, it was found that the monolith had a three-dimensionally continuous skeleton and pores, and had a co-continuous structure in which the two phases were entangled. The skeleton thickness measured from the SEM image was 17 μm. The size of the three-dimensionally continuous pores of the monolith measured by mercury intrusion porosimetry was 41 μm, and the total pore volume was 2.9 ml/g.

(Production of bicontinuous monolithic anion exchanger)
The monolith produced by the above method was cut into a disk shape with a diameter of 70 mm and a thickness of about 50 mm. 4700 ml of dimethoxymethane and 67 ml of tin tetrachloride were added thereto, and 1870 ml of chlorosulfuric acid was added dropwise under ice cooling. After the dropwise addition, the temperature was raised and the mixture was reacted at 35°C for 5 hours to introduce chloromethyl groups. After the reaction was completed, the mother liquor was removed by siphoning and washed with a mixed solvent of THF/water = 2/1, and then further washed with THF. 3400 ml of THF and 2000 ml of a 30% aqueous solution of trimethylamine were added to this chloromethylated monolithic organic porous material, and the mixture was reacted at 60°C for 6 hours. After the reaction was completed, the product was washed with a mixed solvent of methanol/water, and then with pure water to isolate it, and a monolithic anion exchanger a having a bicontinuous structure was obtained.

(Production of bicontinuous monolithic cation exchanger)
The monolith produced by the above method was cut into a disk shape with a diameter of 75 mm and a thickness of about 15 mm. 1500 ml of dichloromethane was added to the monolith, and the monolith was heated at 35° C. for 1 hour, cooled to 10° C. or less, and 99 g of chlorosulfuric acid was gradually added. The mixture was then heated to 35° C. and reacted for 24 hours. Methanol was then added to quench the remaining chlorosulfuric acid, and the monolith was washed with methanol to remove dichloromethane and further washed with pure water to obtain a monolith cation exchanger c having a bicontinuous structure.

(Analysis of monolith anion exchanger a)
A portion of the obtained monolith anion exchanger a was cut out and dried, and the internal structure was observed by SEM, confirming that the bicontinuous structure was maintained. The swelling ratio of the monolith anion exchanger a before and after the reaction was 1.4 times, and the anion exchange capacity per volume was 0.72 mg equivalent/ml in a water-wet state. The size of the continuous pores of the monolith in a water-wet state was estimated to be 70 μm from the value of the monolith and the swelling ratio of the cation exchanger in a water-wet state, and the skeleton diameter was 23 μm, and the total pore volume was 2.9 ml/g.

The differential pressure coefficient, which is an index of pressure loss when water is passed through, was 0.005 MPa/m·LV. Furthermore, when the ion exchange zone length for chloride ions of the monolith anion exchanger a was measured, the ion exchange zone length at LV=20 m/h was 16 mm.

Next, to confirm the distribution of quaternary ammonium groups in monolithic anion exchanger a, anion exchanger a was treated with an aqueous hydrochloric acid solution to convert it to a chloride form, and the distribution of chlorine atoms was observed using EPMA. As a result, it was observed that the quaternary ammonium groups were uniformly introduced onto the surface and inside (cross-sectional direction) of the anion exchanger's skeleton.

(Analysis of monolithic cation exchanger)
In addition, a part of the obtained monolith cation exchanger c was cut out and dried, and the internal structure was observed by SEM, confirming that the monolith cation exchanger c maintained a bicontinuous structure. In addition, the swelling ratio of the monolith cation exchanger c before and after the reaction was 1.4 times, and the cation exchange capacity per volume was 0.72 mg equivalent/ml in a water-wet state. The size of the continuous pores of the monolith in a water-wet state was estimated to be 70 μm from the value of the monolith and the swelling ratio of the cation exchanger in a water-wet state, and the diameter (average thickness) of the skeleton was 23 μm, and the total pore volume was 2.9 ml/g.

The differential pressure coefficient, which is an index of pressure loss when water is permeated, was 0.005 MPa/m·LV. Furthermore, when the ion exchange zone length for sodium ions of the monolithic cation exchanger c was measured, the ion exchange zone length at LV = 20 m/h was 16 mm, which is not only overwhelmingly shorter than the value (320 mm) of Amberlite IR120B (manufactured by Dow Chemical), a commercially available strongly acidic cation exchange resin, but also shorter than the value of a conventional monolithic porous cation exchanger having an open-cell structure.

Next, to confirm the distribution of sulfonic acid groups in monolith cation exchanger c, the distribution of sulfur atoms was observed by EPMA. As a result, it was observed that sulfonic acid groups were uniformly introduced onto the skeleton surface and inside the skeleton (cross-sectional direction) of the cation exchanger.

<Metal element analysis method>
In the following Examples and Comparative Examples, the amount of metal elements (mass ppb) in an aqueous solvent refers to a value measured using inductively coupled plasma mass spectrometry (ICP-MS, Agilent 7500cs manufactured by Agilent Technologies, Inc.).

Example 1
A portion of the synthesized monolithic anion exchanger a was packed in an amount of 3.9 mL into a PFA (tetrafluoroethylene-perfluoroalkylvinylether copolymer) column having an inner diameter of 10 mm and a height of 50 mm to prepare an anion exchanger-packed cartridge A.
The above-mentioned anion exchanger-packed cartridge A was subjected to the following treatments (1) to (3) to change the ion form.
(1) Mineral acid treatment and water washing treatment 300 mL of a 1.0 N nitric acid aqueous solution (TAMAPURE-AA-100, manufactured by Tama Chemical Industries Co., Ltd.) was passed through the anion exchanger-filled cartridge A at an SV (flow rate/monolith anion exchanger volume ratio) of 1,500 (100 ml/min), and then ultrapure water was used for washing at an SV (flow rate/monolith anion exchanger volume ratio) of 750 (50 ml/min) for 10 minutes.
(2) Hydrochloric acid treatment and water washing treatment The anion exchanger-filled cartridge A that had been subjected to the treatment in (1) above was passed through with 300 mL of a 1.0 N hydrochloric acid aqueous solution (TAMAPURE-AA-100, manufactured by Tama Chemical Industries Co., Ltd.) at an SV (flow rate/monolith anion exchanger volume ratio) of 1,500 (100 ml/min), and then washed with ultrapure water at an SV (flow rate/monolith anion exchanger volume ratio) of 750 (50 ml/min) for 10 minutes.
(3) Treatment with an aqueous solution of quaternary ammonium hydroxide To the anion exchanger-filled cartridge A that had been treated in (2) above, 300 mL of a 1.0 N aqueous solution of trimethylhydroxyammonium (TMAH) (TAMAPURE-AA TMAH, manufactured by Tama Chemical Industries Co., Ltd.) was passed through the cartridge at a SV (flow rate/monolith anion exchanger volume ratio) of 1,500 (100 ml/min), and then the cartridge was washed with ultrapure water at a SV (flow rate/monolith anion exchanger volume ratio) of 750 (50 ml/min) for 10 minutes.
The total time required for the above steps (1) to (3) was about 40 minutes.
The amount of metal elements in the discharged liquid collected at the outlet of the anion exchanger-packed cartridge A after the liquid passing treatment in the above (3) was measured. The results are shown in Table 1.

Comparative Example 1
An anion exchanger-packed cartridge was prepared by packing 3.9 mL of the same monolith anion exchanger a as the monolith anion exchanger a used in the ion form change treatment in Example 1 into a PFA (tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer) column with an inner diameter of 10 mm and a height of 50 mm.
The above-mentioned anion exchanger-filled cartridge was regenerated by carrying out the following steps (1) to (4).
(1) Mineral acid treatment and water washing treatment 300 mL of a 1.0 N nitric acid aqueous solution was passed through the anion exchanger-filled cartridge at an SV (flow rate/monolith anion exchanger volume ratio) of 1,500 (100 ml/min), and then ultrapure water was used for water washing at an SV (flow rate/monolith anion exchanger volume ratio) of 750 (50 ml/min) for 10 minutes.
(2) Hydrochloric acid treatment and water washing treatment The anion exchanger-filled cartridge subjected to the treatment in (1) above was passed through with 300 mL of a 1.0 N hydrochloric acid aqueous solution at an SV (flow rate/monolith anion exchanger volume ratio) of 1,500 (100 ml/min), and then washed with ultrapure water at an SV (flow rate/monolith anion exchanger volume ratio) of 750 (50 ml/min) for 10 minutes.
(3) Bicarbonate treatment and water washing treatment The anion exchanger-filled cartridge that had been treated in (2) above was passed through with 300 mL of a 2.0% aqueous ammonium bicarbonate solution (Kanto Chemical Co., Ltd., Kagoshima Tokkyu) at an SV (flow rate/monolith anion exchanger volume ratio) of 1,500 (100 ml/min), and then washed with ultrapure water at an SV (flow rate/monolith anion exchanger volume ratio) of 750 (50 ml/min) for 10 minutes.
(4) Sodium hydroxide treatment To the anion exchanger-filled cartridge that had been treated in (3) above, 300 mL of a 1.0 N aqueous sodium hydroxide solution (Kanto Chemical Co., Ltd., special grade) was passed through at an SV (flow rate/monolith anion exchanger volume ratio) of 1,500 (100 ml/min), and then ultrapure water was washed for 10 minutes at an SV (flow rate/monolith anion exchanger volume ratio) of 750 (50 ml/min).
The total time required for the above steps (1) to (4) was about 60 minutes.
The amount of metal elements in the discharged liquid collected at the outlet of the anion exchanger-packed cartridge after the liquid passing treatment in (4) above was measured. The results are shown in Table 1.

From the above results, it can be seen that in Example 1, since the monolith anion exchanger a is prepared by contacting it with an aqueous solution of quaternary ammonium hydroxide, the anion exchanger can be prepared easily and in a short time while suppressing the residual presence of various metals.
On the other hand, in Comparative Example 1, since the monolith anion exchanger a is prepared by contacting it with an aqueous solution of sodium hydroxide, the preparation process involves multiple steps and requires a long time, and it is clear that a certain amount of various metal elements such as Na element remain in the monolith anion exchanger a.

Example 2
As shown in FIG. 5(a), a purification apparatus U was prepared by connecting a cation exchanger-packed cartridge C prepared by packing 3.9 mL of the above-mentioned monolithic cation exchanger c in a PFA (tetrafluoroethylene-perfluoroalkylvinylether copolymer) column having an inner diameter of 10 mm and a height of 50 mm to an anion exchanger-packed cartridge A prepared in the same manner as in Example 1 in a manner allowing a liquid to pass through.
As shown in FIG. 5(a), an aqueous Na ion solution with a concentration of 1000 ng/L was passed through an inlet provided at the end of the anion exchanger-packed cartridge A of the purification apparatus U at an SV (flow rate/anion exchanger volume ratio) of 1500 (100 ml/min), and the Na ion concentration in the discharged liquid flowing out from an outlet provided at the end of the cation exchanger-packed cartridge C of the purification apparatus U was measured at regular intervals.
The results are shown in Figure 6.
In Figure 6, the removal performance of the purification device U is evaluated based on the change over time in the ratio of the Na ion concentration at the outlet of the cation exchanger-packed cartridge to the Na ion concentration at the inlet of the anion exchanger-packed cartridge (Na ion concentration at the outlet of the cation exchanger-packed cartridge/Na ion concentration at the inlet of the anion exchanger-packed cartridge).

(Comparative Example 2)
A purification apparatus was prepared by connecting a cation exchanger-packed cartridge prepared by packing 3.9 mL of the above-mentioned monolithic cation exchanger c into a PFA (tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer) column having an inner diameter of 10 mm and a height of 50 mm to an anion exchanger-packed cartridge prepared in the same manner as in Comparative Example 1 in a manner allowing liquid to pass through.
An aqueous Na ion solution with a concentration of 1000 ng/L was passed through an inlet provided at the end of the anion exchanger-packed cartridge of the purification device at an SV (flow rate/anion exchanger volume ratio) of 1500 (100 ml/min), and the Na ion concentration in the discharged liquid flowing out from an outlet provided at the end of the cation exchanger-packed cartridge of the purification device was measured at regular intervals.
The results are shown in Figure 6.

From the above results, it can be seen that in Example 2, the monolith anion exchanger is regenerated by contacting it with an aqueous solution of quaternary ammonium hydroxide, which prevents metal ions from remaining. Therefore, even if an aqueous solution of Na ions is passed through the monolith cation exchanger, Na ions can be effectively removed and their leakage can be prevented.
On the other hand, in Comparative Example 2, since the monolith anion exchanger is contacted with an aqueous solution of sodium hydroxide during regeneration, Na element remains in the monolith anion exchanger. As a result, Na ions flow out of the monolith anion exchanger when the aqueous Na ion solution is passed through it, which increases the loading of Na ions on the subsequent monolith cation exchanger and reduces the removal performance.

Example 3
A portion of the synthesized monolithic anion exchanger a was packed in an amount of 3.9 mL into a PFA (tetrafluoroethylene-perfluoroalkylvinylether copolymer) column having an inner diameter of 10 mm and a height of 50 mm to prepare an anion exchanger-packed cartridge.
The above-mentioned anion exchanger-filled cartridge was regenerated by carrying out the following steps (1) to (3).
(1) Mineral acid treatment and water washing treatment 300 mL of a 1.0 N nitric acid aqueous solution was passed through the anion exchanger-filled cartridge at an SV (flow rate/monolith anion exchanger volume ratio) of 1,500 (100 ml/min), and then ultrapure water was used for water washing at an SV (flow rate/monolith anion exchanger volume ratio) of 750 (50 ml/min) for 10 minutes.
(2) Hydrochloric acid treatment and water washing treatment 300 mL of a 1.0 N nitric acid aqueous solution was passed through the anion exchanger-filled cartridge at an SV (flow rate/monolith anion exchanger volume ratio) of 1,500 (100 ml/min), and then ultrapure water was used for water washing at an SV (flow rate/monolith anion exchanger volume ratio) of 750 (50 ml/min) for 10 minutes.
(3) Treatment with an aqueous solution of quaternary ammonium hydroxide 80 mL of an aqueous solution of trimethylhydroxyammonium (TMAH) having a concentration of 1.0 N was passed through the anion exchanger-filled cartridge at an SV (flow rate/monolith anion exchanger volume ratio) of 800 (53 ml/min).
The total time required for the above steps (1) to (3) was about 35 minutes.
The regeneration rate of the anion exchanger-packed cartridge obtained by carrying out the above treatments (1) to (3) was calculated by the following method.

<How to calculate the reproduction rate>
Regeneration rate (%) = {R-OH (meq/g) / total ion exchange capacity (meq/g)} × 100

In this application, the above R-OH means the amount of OH ions present as counter ions to the quaternary ammonium groups (R) of the anion exchanger.
In addition, in the present application, R-OH means a value measured by passing a sodium nitrate solution through an anion exchanger that has been regenerated by a predetermined method, and titrating the recovered solution with sulfuric acid.
In addition, in the present application, the total ion exchange capacity means a value obtained by passing hydrochloric acid through the anion exchanger to convert it to Cl form, passing sodium nitrate through the anion exchanger, and measuring the recovered liquid by silver nitrate titration (Mohr's method).
The results are shown in Table 2.

Example 4
The anion exchanger-filled cartridge was regenerated in the same manner as in Example 3, except that in "(3) Treatment with an aqueous solution of a quaternary ammonium hydroxide" in Example 3, the flow rate of a 1.0 N aqueous trimethylhydroxyammonium (TMAH) solution was set at SV (flow rate/monolith anion exchanger volume ratio) = 400 (25 ml/min).
The total time required for the above regeneration process was about 40 minutes.
The regeneration rate of the anion exchanger-filled cartridge obtained after the above regeneration treatment was calculated in the same manner as in Example 3. The results are shown in Table 2.

Example 5
After using the synthesized monolithic anion exchanger a in an ultrapure water production system for one month,
The cartridge packed with the anion exchanger was regenerated in the same manner as in Example 4.
The total time required for the above regeneration process was about 40 minutes.
The regeneration rate of the anion exchanger-filled cartridge obtained by the above-mentioned regeneration treatment was calculated in the same manner as in Example 3. The results are shown in Table 2.

( Reference Example 1 )
An anion exchanger-packed cartridge was prepared by packing 3.9 mL of the following anion exchange resin into a PFA (tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer) column having an inner diameter of 10 mm and a height of 50 mm.
<Anion exchange resin>
A strongly basic anion exchange resin in the Cl form (Dow Chemical Company Amberjet 4002, details below).
Base (resin material): styrene-based Ion exchange group: quaternary ammonium group Ion exchange equivalent: anion exchange group 1.2 mg equivalent/ml wet resin or more Water content in saturated equilibrium state: 40% by mass
Ionic form in saturated water-wet state: Cl form. The anion exchanger-packed cartridge was regenerated in the same manner as in Example 3, except that the above anion exchange resin was used instead of the monolithic anion exchanger a.
The total time required for the regeneration process was 35 minutes.
The regeneration rate of the anion exchanger-filled cartridge obtained by the above-mentioned regeneration treatment was calculated in the same manner as in Example 3. The results are shown in Table 2.

( Reference Example 2 )
In Reference Example 1 , the anion exchanger-filled cartridge was regenerated in the same manner as in Example 4, except that the flow rate of the 1.0 N trimethylhydroxyammonium (TMAH) aqueous solution was changed to SV (flow rate/monolith anion exchanger volume ratio) = 400.
The total time required for the above regeneration process was 40 minutes.
The regeneration rate of the anion exchanger-filled cartridge obtained after the above regeneration treatment was calculated in the same manner as in Example 3. The results are shown in Table 2.

(Comparative Example 3)
An anion exchanger-packed cartridge was prepared by packing 3.9 mL of the same anion exchange resin as that used for the regeneration treatment in Example 6 into a PFA (tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer) column having an inner diameter of 10 mm and a height of 50 mm.
The above-mentioned anion exchanger-filled cartridge was regenerated by carrying out the following steps (1) to (4).
(1) Mineral acid treatment and water washing treatment 300 mL of a 1.0 N nitric acid aqueous solution was passed through the anion exchanger-filled cartridge at an SV (flow rate/volume ratio of monolith anion exchanger) of 1,500 (100 ml/min), and then ultrapure water was washed for 10 minutes at an SV (flow rate/volume ratio of anion exchange resin) of 750 (50 ml/min).
(2) Hydrochloric acid treatment and water washing treatment 300 mL of a 1.0 N nitric acid aqueous solution was passed through the anion exchanger-filled cartridge at an SV (flow rate/volume ratio of monolith anion exchanger) of 1,500 (100 ml/min), and then ultrapure water was used for water washing treatment at an SV (flow rate/volume ratio of anion exchange resin) of 750 (50 ml/min) for 10 minutes.
(3) Bicarbonate treatment and water washing treatment 300 mL of a 2.0% aqueous ammonium bicarbonate solution (Kanto Chemical, Kagoshima Tokkyu) was passed through the anion exchanger-filled cartridge at an SV (flow rate/monolith anion exchanger volume ratio) of 1500 (100 ml/min), and then ultrapure water was washed for 10 minutes at an SV (flow rate/anion exchange resin volume ratio) of 750 (50 ml/min).
(4) Sodium Hydroxide Treatment 300 mL of a 1.0 N aqueous sodium hydroxide solution was passed through the anion exchanger-filled cartridge at an SV (flow rate/monolith anion exchanger volume ratio) of 800 (53 ml/min).
The total time required for the above regeneration processes (1) to (4) was about 60 minutes.
The regeneration rate of the anion exchanger-filled cartridge obtained by the above-mentioned regeneration treatment was calculated in the same manner as in Example 4. The results are shown in Table 2.

From the above results, it can be seen that in Examples 3 to 5 , the ionic form of the anion exchanger is changed and regenerated by contacting it with an aqueous solution of quaternary ammonium hydroxide, which makes it possible to easily and quickly change the ionic form of the anion exchanger to the OH form at a high rate while suppressing the remaining of various metals.
On the other hand, in Comparative Example 3, since the anion exchanger is regenerated by contacting it with an aqueous solution of sodium hydroxide, the regeneration process requires many steps and takes a long time, and the regeneration rate is poor.

It is possible to provide a method for easily and quickly changing the ionic form of an anion exchanger to the OH form at a high rate while suppressing the residual amount of various metals, and a method for producing an anion exchanger.

REFERENCE SIGNS LIST 1 Skeleton phase 2 Pore phase 3 Container 4 Tank 5 Storage tank 10 Structure P Pump S Aqueous solution of quaternary ammonium hydroxide W Discharge liquid A Anion exchanger C Cation exchanger U Purification device

Claims (7)

In order to change the ion form of a monolithic organic porous anion exchanger used in the purification of ultrapure water or chemical solutions,
A method for changing the ionic form of a monolithic organic porous anion exchanger , comprising contacting the monolithic organic porous anion exchanger with an aqueous solution of a quaternary ammonium hydroxide by passing the aqueous solution of the quaternary ammonium hydroxide through the monolithic organic porous anion exchanger at a liquid hourly space velocity (SV) of 300 to 4000 h ^-1 . The quaternary ammonium hydroxide is represented by the following general formula (I):

(In the formula, R ¹ to R ⁴ are each a hydrocarbon group having 1 to 4 carbon atoms which may have a hydroxyl group, and may be the same or different.)
2. The method for changing the ion type of a monolithic organic porous anion exchanger according to claim 1, wherein the anion exchanger is one or more compounds selected from the group consisting of compounds represented by the formula: The method for changing the ion type of a monolithic organic porous anion exchanger according to claim 1 or 2, wherein the concentration of the quaternary ammonium hydroxide in the aqueous solution of the quaternary ammonium hydroxide is 0.1 to 2.0N. The method for changing the ion form of a monolithic organic porous anion exchanger according to any one of claims 1 to 3, comprising contacting the monolithic organic porous anion exchanger with a mineral acid, washing the monolithic organic porous anion exchanger with water, and then contacting the monolithic organic porous anion exchanger with an aqueous solution of the quaternary ammonium hydroxide. The method for changing the ion form of a monolithic organic porous anion exchanger according to any one of claims 1 to 4, comprising contacting the monolithic organic porous anion exchanger with a mineral acid, washing the monolithic organic porous anion exchanger with water, contacting the monolithic organic porous anion exchanger with hydrochloric acid, washing the monolithic organic porous anion exchanger with water, and then contacting the monolithic organic porous anion exchanger with an aqueous solution of the quaternary ammonium hydroxide . The monolithic organic porous anion exchanger according to claim 1, wherein the monolithic organic porous anion exchanger is a bicontinuous structure consisting of a three-dimensionally continuous skeleton having an average thickness of 1 to 60 μm in a dry state, which is made of an aromatic vinyl polymer containing 0.1 to 5.0 mol% of crosslinked structural units among all structural units, and three-dimensionally continuous pores having an average diameter of 10 to 200 μm in a dry state between the skeletons, the total pore volume in a dry state is 0.5 to 10 mL/g, the anion exchange group is present, the anion exchange capacity per volume in a water-wet state is 0.2 to 1.0 mg equivalent/mL (water-wet state), and the anion exchange group is uniformly distributed in the organic porous anion exchanger . In order to change the ion form during the production of monolithic organic porous anion exchangers used in the purification of ultrapure water or chemical solutions,
A method for producing a monolithic organic porous anion exchanger , comprising contacting the monolithic organic porous anion exchanger with an aqueous solution of a quaternary ammonium hydroxide by passing the aqueous solution of the quaternary ammonium hydroxide through the monolithic organic porous anion exchanger at a liquid hourly space velocity (SV) of 300 to 4000 h ^-1 .