Method for producing purified aqueous quaternary ammonium compound solution

Abstract

Provided is a method for producing a purified aqueous solution of a quaternary ammonium compound, the aqueous solution of the quaternary ammonium compound containing 1000 ppm or less of organic impurities having a molecular weight of 1000 g / mol or more, containing a specific quaternary ammonium ion, and containing metal impurities, the method comprising contacting a crude aqueous solution of the quaternary ammonium compound with a crosslinking degree of 6 or more and a cation exchange resin in which the counter ion is a non-metallic ion.

Description

[Technical field]

[0001] The present invention relates to a method for producing a purified aqueous solution of a quaternary ammonium compound, and more particularly to the method for reducing the content of metal impurities in an aqueous solution of a crude quaternary ammonium compound that contains the metal impurities as impurities. [Background technology]

[0002] Quaternary ammonium compounds are used in phase transfer catalysts, surfactants, disinfectants, etc. In particular, quaternary ammonium hydroxide compounds, such as tetramethylammonium hydroxide, are used as a pH adjuster, or in the form of an aqueous solution for cleaning, etching, and developing solutions during semiconductor manufacturing, as a type of organic alkali that exhibits strong basicity. In such semiconductor-related processing applications, as integration progresses, metal impurities, if remaining on the surface of electronic devices, can cause defects, so it is required to reduce them as much as possible. More specifically, it is desired to reduce the content of metal impurities such as Na, K, Li, Ca, Mg, and Sr to 100 ppt or less in terms of the total content.

[0003] In general, aqueous solutions of quaternary ammonium compounds are produced by synthesis using tertiary amines and alkyl salts, electrolysis using an electrolytic cell with an ion exchange membrane, etc. For example, aqueous solutions of quaternary ammonium hydroxide are synthesized by subjecting an aqueous solution of quaternary ammonium salt as a raw material to electrolysis, etc. In the aqueous solution of quaternary ammonium hydroxide thus synthesized (or the aqueous solution of quaternary ammonium salt, which is the raw material for obtaining it), the above-mentioned metal impurities are present at a high content level of several hundred ppt or more, which is unsatisfactory from the viewpoint of the defect prevention effect in the semiconductor application.

[0004] Filter treatment is a common method for purifying such a crude aqueous solution of quaternary ammonium compounds. Although filter treatment is effective in reducing particulate metal impurities, it has the problem that it is almost ineffective in removing dissociated ions due to the limitations of the pore size.

[0005] Adsorption treatment with a cation exchange resin is considered to be effective for removing metal ions from an aqueous solution of a quaternary ammonium compound. For example, in Patent Document 1, this treatment is performed on an aqueous solution of a quaternary ammonium hydroxide compound synthesized by the above-mentioned electrolysis method, and it is shown that metal ions such as Na ions and Ca ions are each reduced to 1 ppb or less (see Reference Example 1 in

[0016] , etc.).

[0006] It is also known that the adsorption treatment of a crude aqueous solution of a quaternary ammonium hydroxide compound (in the present invention, the crude aqueous solution of a quaternary ammonium hydroxide compound is an aqueous solution of a quaternary ammonium compound containing 1000 ppm or less of organic impurities having a molecular weight of 1000 g / mol or more and containing metal impurities) with a cation exchange resin is also applicable for the purpose of recovering the quaternary ammonium hydroxide compound component from the waste liquid when the aqueous solution of a quaternary ammonium hydroxide compound is used as a photoresist developer for semiconductor manufacturing (for example, Patent Document 2, etc.). Here, the strongly acidic cation exchange resin product used in Example 1, which is shown as a representative example of a cation exchange resin in the above Patent Document 2, is described as having a crosslinking degree of 2 to 10% in Patent Document 3 (lower right column on page 3). [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Publication No. 06-025880 [Patent Document 2] JP 2003-190949 A [Patent Document 3] Japanese Patent Application Publication No. 1-98617 Summary of the Invention [Problem to be solved by the invention]

[0008] Even in the case of the adsorption treatment of the photoresist developer waste liquid by the cation exchange resin, the reduction effect of metal ions was often not fully satisfactory. Moreover, according to the study by the present inventors, in this case, even if the selection of the cation exchange resin exerts a relatively high reduction effect of metal ions at the beginning of the treatment, the reduction effect rapidly deteriorates as the purification is continued and the amount of treatment increases. For this reason, the knowledge of metal ion removal when the developer waste liquid is the liquid to be treated cannot be taken into consideration for the purification of the aqueous quaternary ammonium compound obtained by the synthesis (in other words, in a state with a low content of organic impurities), which requires stable production for a long time. In addition, although it is known that the metal ions can be reduced from the aqueous quaternary ammonium compound solution by the cation exchange resin, there was no knowledge of achieving a reduction in metal ions of the order of several to several hundred ppt, or of using the solution for a long time.

[0009] In light of the above, an object of the present invention is to provide a method for removing metal ions from an aqueous solution of a quaternary ammonium compound having a low content of organic impurities, such as that obtained by synthesis, by which the removal effect can be maintained at a high level even when the method is continued at a predetermined treatment rate. [Means for solving the problem]

[0010] As a result of extensive research to achieve this objective, the inventors discovered that the above problem could be solved by contacting the treated liquid with a cation exchange resin having a specific degree of crosslinking, thereby completing the present invention.

[0011] That is, the present invention is a method for producing a purified aqueous solution of a quaternary ammonium compound, which comprises contacting an aqueous solution of a specific crude quaternary ammonium compound, containing 1000 ppm or less of organic impurities having a molecular weight of 1000 g / mol or more and containing metal impurities, with a cation exchange resin having a crosslinking degree of 6 or more and having a non-metal ion type counter ion. Here, in the present invention, the purified aqueous solution of a quaternary ammonium compound is an aqueous solution of a quaternary ammonium compound in which the metal ion content has been reduced by contacting an aqueous solution of a crude quaternary ammonium hydroxide compound with a cation exchange resin. Effect of the Invention

[0012] According to the present invention, metal ions contained in a crude aqueous solution of quaternary ammonium compounds having a low content of organic impurities, such as those obtained by synthesis, can be adsorbed and removed with an excellent reduction effect. This excellent reduction effect can be maintained to a high degree even when a large amount of the aqueous solution of the crude quaternary ammonium compounds is treated. Therefore, the present invention is extremely useful as an industrial method for producing an aqueous solution of a purified quaternary ammonium compound. In particular, the present invention is useful as a method for producing a quaternary ammonium compound having a specific alkyl group. [Brief description of the drawings]

[0013] [Figure 1] FIG. 1 is a schematic diagram of an electrolytic cell used in the production of quaternary ammonium compounds. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] In the present invention, the crude aqueous solution of a quaternary ammonium compound, which is the liquid to be treated and brought into contact with the cation exchange resin, has a cleanliness level of 1000 ppm or less of organic impurities with a molecular weight of 1000 g / mol or more. The above impurities are mixed in from the raw materials used in the synthesis of the quaternary ammonium compound, as well as from the reaction vessel, piping, contact members of the vessel, and the like. By using high-purity raw materials and appropriately selecting contact members, it is possible to obtain an aqueous solution of a quaternary ammonium compound that satisfies the cleanliness requirements of the above organic impurities. On the other hand, even if it is the same aqueous solution of a quaternary ammonium compound, when it becomes a waste liquid of a photoresist developer discharged during semiconductor manufacturing, this contains various organic impurities with large molecular weights (usually novolac resin derivatives and their decomposition products, etc.) derived from the photoresist, so the requirements regarding the cleanliness of the above organic impurities are not satisfied. In addition, it is possible to reduce some organic impurities with large molecular weights by neutralizing and insolubilizing the photoresist, but various other organic substances are also contained, and the requirements regarding the cleanliness of the above organic impurities are usually not satisfied.

[0015] In addition, even if the organic impurities contained in the crude quaternary ammonium compound aqueous solution have a molecular weight of less than 1000 g / mol, they have almost no effect on the metal ion removal effect of the cation exchange resin. Therefore, the crude quaternary ammonium compound aqueous solution may contain organic impurities with such a low molecular weight, but the content is preferably 3 mass% or less. Such low molecular weight organic impurities are considered to be mixed in from unreacted components or impurities of the raw materials used in the synthesis process of the quaternary ammonium compound aqueous solution, and include organic solvents such as methanol and ethanol, and surfactants.

[0016] The content of the organic impurities having a molecular weight of 1000 g / mol or more in the crude aqueous quaternary ammonium compound solution is more preferably 500 ppm or less, and particularly preferably 100 ppm or less.

[0017] The measurement of organic impurities in the crude quaternary ammonium compound aqueous solution is carried out according to the following procedure. First, a sample of the crude quaternary ammonium compound aqueous solution is injected into a gel permeation chromatography (GPC) column, and the liquid containing 1000 g / mol or more of organic impurities is separated and collected. Then, the TOC concentration of the two liquids, the collected liquid and the eluent used for separation by GPC, is obtained using a total organic carbon (TOC) meter, the TOC concentration of the eluent alone is subtracted from the TOC concentration of the collected liquid, and the value is multiplied by the dilution factor of the crude quaternary ammonium compound aqueous solution in the collected liquid, and this value is taken as the concentration of organic impurities in the crude quaternary ammonium compound aqueous solution. Note that when the amount of liquid collected after passing through the GPC column is small and measurement using a TOC meter is difficult, or when the TOC concentration is too low, it is also possible to measure the concentration of organic impurities by collecting the liquid multiple times or concentrating the liquid.

[0018] In the present invention, the quaternary ammonium compound may be any hydroxide or salt of quaternary ammonium without any restrictions. Examples of quaternary ammonium salts include halide salts such as chloride salts and bromide salts, and carbonate salts (including bicarbonate salts, carbonate salts, and mixtures thereof). The quaternary ammonium ion is represented by the following formula (1). [ka] (In the formula, R 1 , R 2 , R 3 , and R 4 are each independently an alkyl group having 1 to 16 carbon atoms, provided that R 1 , R 2 , R 3 , and R 4 Among these, at least one alkyl group has 2 to 16 carbon atoms.)

[0019] In the formula (1), R 1 , R 2 , R 3 , and R 4 may all be the same alkyl group. For example, R 1 , R2 , R 3 , and R 4 may all be ethyl, propyl, or butyl. On the other hand, in the formula (1), R 1 , R 2 , R 3 , and R 4 It is preferable that not all of are the same alkyl group. In other words, the following quaternary ammonium ions (i) to (iii) are preferable. (i)R 1 , R 2 , R 3 , and R 4 A quaternary ammonium ion in which three of the above are the same alkyl group and the remaining one is a different alkyl group. (ii)R 1 , R 2 , R 3 , and R 4 A quaternary ammonium ion in which any two of the above are the same alkyl group and the remaining two are different alkyl groups (the remaining two may be the same or different). (iii)R 1 , R 2 , R 3 , and R 4 A quaternary ammonium ion in which all of the alkyl groups are different. In the above case (i), R 1 , R 2 , R 3 , and R 4 and the remaining one is an alkyl group having 1 to 16 carbon atoms, the first three and the remaining one are different alkyl groups, and either the first three or the remaining one has a carbon number of 2 to 16. 1 , R 2 , R 3 , and R 4Among these, it is preferable that three of them are the same group and the remaining one is an alkyl group having 2 to 16 carbon atoms different from the above groups. In this case, the quaternary ammonium ion represented by formula (1) has two types of alkyl groups. In this embodiment, R 1 , R 2 , R 3 , and R 4 Preferred are quaternary ammonium ions in which any three of the above are methyl groups and the remaining alkyl group has a carbon number of 2 to 16. Among these, preferred are quaternary ammonium ions in which the remaining alkyl group has a carbon number of 2, 3 or 4. In the above case (ii), R 1 , R 2 , R 3 , and R 4 and the remaining two are alkyl groups having 1 to 16 carbon atoms different from the first two, and the remaining two are the same or different alkyl groups, and either the first two or the remaining two have a carbon number of 2 to 16. In this case, the quaternary ammonium ion represented by formula (1) has two or three types of alkyl groups. In the above case (iii), R 1 , R 2 , R 3 , and R 4 are all different alkyl groups, at least one of which has a carbon number of 2 to 16. In this case, the quaternary ammonium ion represented by formula (1) has four types of alkyl groups.

[0020] Specific examples of quaternary ammonium compounds include hydroxides such as tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, ethyltrimethylammonium hydroxide, propyltrimethylammonium hydroxide, and butyltrimethylammonium hydroxide; chloride salts such as tetraethylammonium chloride, tetrapropylammonium chloride, tetrabutylammonium chloride, ethyltrimethylammonium chloride, propyltrimethylammonium chloride, and butyltrimethylammonium chloride; bromide salts such as tetraethylammonium bromide, tetrapropylammonium bromide, tetrabutylammonium bromide, ethyltrimethylammonium bromide, propyltrimethylammonium bromide, and butyltrimethylammonium bromide; tetraethylammonium carbonate, tetrapropylammonium carbonate, tetrabutylammonium carbonate, ethyltrimethylammonium carbonate, propyltrimethylammonium carbonate, and butyltrimethylammonium carbonate. Examples of the quaternary ammonium compounds include carbonates such as ammonium hydroxide, quaternary ammonium halide, and quaternary ammonium carbonate. In particular, quaternary ammonium hydroxide, propyl trimethyl ammonium hydroxide, butyl trimethyl ammonium hydroxide, ethyl trimethyl ammonium chloride, propyl trimethyl ammonium chloride, butyl trimethyl ammonium chloride, ethyl trimethyl ammonium bromide, propyl trimethyl ammonium bromide, butyl trimethyl ammonium bromide, ethyl trimethyl ammonium carbonate, propyl trimethyl ammonium carbonate, and butyl trimethyl ammonium carbonate are preferably used, and more preferably, one or more selected from the group consisting of ethyl trimethyl ammonium hydroxide, ethyl trimethyl ammonium chloride, ethyl trimethyl ammonium bromide, and ethyl trimethyl ammonium carbonate are preferably used. These quaternary ammonium compounds may be one type or a mixture of multiple types. In the present invention, specific examples of the crude quaternary ammonium compounds are the same as those described for the quaternary ammonium compounds.

[0021] The concentration of the quaternary ammonium compound is not particularly limited, but generally, if the adsorption treatment is performed at a high concentration, the amount of liquid passing through the solution can be reduced, and concentration work is not required in the subsequent process, so that the concentration is preferably 10% by mass or more, and more preferably 20% by mass or more. On the other hand, if the concentration of the quaternary ammonium compound becomes too high, crystallization or viscosity increases, so that the concentration is preferably 70% by mass or less, and more preferably 60% by mass or less. In addition, if crystallization occurs at a high concentration, it is sufficient to carry out the treatment within a range that does not reach that concentration. In the present invention, the concentration of the quaternary ammonium compound in the aqueous solution can be measured by ion chromatography or potentiometric titration.

[0022] The water component constituting the crude aqueous solution of a quaternary ammonium compound is preferably as pure as possible, and is more preferably ultrapure water.

[0023] These aqueous solutions of crude quaternary ammonium compounds usually contain metal impurities of 1000 ppt or more, and even at the lowest, exceed 100 ppt. Even with this level of content, when these are used for the semiconductor applications, it is not satisfactory from the viewpoint of suppressing defects, and it becomes necessary to carry out the purification treatment according to the present invention.

[0024] Here, in the present invention, the metal impurities specifically refer to elements consisting of Na, K, Li, Ca, Mg, and Sr, and the content is evaluated as the total content of these elements. Note that, in the present invention, the content of the metal impurities in the aqueous solution of the quaternary ammonium compound refers to a value analyzed by an inductively coupled plasma mass meter (ICP-MS).

[0025] The crude quaternary ammonium compound aqueous solution can be applied from any origin as long as it satisfies the requirements for the content of the organic impurities and metal impurities. Usually, it is preferable to use an aqueous solution of quaternary ammonium hydroxide obtained by synthesis by electrolysis or the like, or an aqueous solution of quaternary ammonium salt that is a raw material for carrying out the synthesis. Here, for the production of an aqueous solution of quaternary ammonium hydroxide by electrolysis, an electrolytic cell is generally used in which at least one cation exchange membrane is arranged between an anode and a cathode, and which is provided with a raw material chamber for supplying an aqueous solution of quaternary ammonium salt as a raw material and a base chamber (cathode chamber) in which an aqueous solution of quaternary ammonium hydroxide is produced. In this production method, quaternary ammonium ions pass through the cation exchange membrane arranged on the cathode side, and an aqueous solution of quaternary ammonium hydroxide is produced in the base chamber. In addition, an electrolytic cell in which a plurality of cation exchange membranes, an anion exchange membrane, and a bipolar membrane (a membrane in which a cation exchange membrane and an anion exchange membrane are laminated together) are installed is proposed, and the method can be applied to any of the electrolytic cells.

[0026] In the present invention, the aqueous solution of the crude quaternary ammonium compound is brought into contact with a cation exchange resin, and the impurity metal ions are adsorbed and removed by the cation exchange resin, thereby reducing the content of metal impurities. Since the aqueous solution of the crude quaternary ammonium compound is neutral to basic, the cation exchange resin can be used well whether it is a strong acid cation exchange resin in which the cation exchange group is a sulfonic acid group, or a weak acid cation exchange resin in which the cation exchange group is a carboxyl group, a phenolic hydroxyl group, or the like.

[0027] However, since the crude aqueous solution of quaternary ammonium compounds may be acidic due to the inclusion of a trace amount of acid during the production process, it is preferable to use a strongly acidic cation exchange resin capable of exchange even in the strongly acidic range. Alternatively, the acid may be neutralized with a hydroxide having the same quaternary ammonium ion as the crude aqueous solution of quaternary ammonium compounds, and then contacted with a weakly acidic cation exchange resin.

[0028] The strongly acidic cation exchange resin generally has a structure in which a sulfonic acid group is introduced into a crosslinkable resin matrix made of a copolymer of a cation exchange group-introducing precursor monovinyl monomer and a crosslinkable monomer. Examples of the cation exchange group-introducing precursor monovinyl monomer include alkyl-substituted styrenes such as styrene, methylstyrene, and ethylstyrene, and halogen-substituted styrenes such as bromostyrene, and these may be used alone or in combination of two or more. As the monovinyl monomer, styrene or a monomer mainly composed of styrene is particularly preferred.

[0029] Examples of the crosslinkable monomer include crosslinkable monomers having multiple vinyl groups such as divinylbenzene, trivinylbenzene, divinyltoluene, divinylnaphthalene, divinylxylene, divinylbiphenyl, bis(vinylphenyl)methane, bis(vinylphenyl)ethane, bis(vinylphenyl)propane, and bis(vinylphenyl)butane, which may be used alone or in combination of two or more. Among these, divinylbenzene is particularly preferred as the crosslinkable monomer.

[0030] On the other hand, examples of the weakly acidic cation exchange resin include copolymers of a monovinyl monomer having the weakly acidic cation exchange group, such as acrylic acid or methacrylic acid, and a crosslinkable monomer. Particularly preferred are acrylic acid-divinylbenzene copolymers and methacrylic acid-divinylbenzene copolymers.

[0031] The greatest feature of the present invention is that the cation exchange resin to be contacted with the aqueous solution of the crude quaternary ammonium compound has a crosslinking degree of 6 or more and a counter ion of non-metal ion type. As a result, the effect of removing metal ions is maintained at a high level even if a large amount of the aqueous solution of the crude quaternary ammonium compound is continuously treated. Here, the crosslinking degree of the cation exchange resin is calculated as [weight of crosslinking monomer / weight of total monomer charge)×100] when the resin is produced. In the case of the strongly acidic cation exchange resin, as explained above, the crosslinking resin base is synthesized first, and the cation exchange group is often introduced in a post-treatment. In the case of the strongly acidic cation exchange resin, the crosslinking degree is calculated without considering the weight of the cation exchange group, which is often introduced in the post-treatment, and without including it in the above formula. In addition, when the crosslinking degree of the cation exchange resin to be used is unknown, the cation exchange resin may be subjected to pyrolysis gas chromatography mass spectrometry (GC / MS) to calculate the ratio of the crosslinking monomer to other monomers.

[0032] Here, the effect of maintaining the metal ion removal effect to a high degree by using a cation exchange resin with a crosslinking degree of 6 or more is an effect that is specifically manifested when a crude quaternary ammonium compound aqueous solution containing a low content of the organic impurities with large molecular weight is used. In other words, in the treatment of photoresist developer wastewater as carried out in the above Patent Document 2, the organic impurities with large molecular weight are contained in large amounts, so this effect is hardly manifested.

[0033] The reason why the effect of continuously removing metal ions is specifically exhibited only in the aqueous solution of crude quaternary ammonium compounds with a low content of organic impurities having a large molecular weight is not entirely clear, but the present inventors speculate that it may be due to the following reason: When the cation exchange resin becomes highly rigid, the polymer chains constituting the resin become more entangled, and the resin density increases, making it difficult for ions to diffuse into the inside of the ion exchange resin.

[0034] When the aqueous solution of crude quaternary ammonium compounds is contacted with a cation exchange resin, the diffusibility into the inside of the particles does not change significantly even if the resin density is increased, if the ion size of the cations is small (ionic radius 2 Å or less) such as hydrogen ions and metal ions, but on the other hand, if the ion size is large such as quaternary ammonium ions, even if they can easily diffuse into the inside of the particles when the resin density is low, as the crosslinking strength increases and the resin density increases, the internal diffusibility is gradually hindered. As a result, it is presumed that in the highly crosslinked cation exchange resin, the internal diffusion of quaternary ammonium ions is suppressed, thereby expressing the adsorption selectivity of highly diffusible metal ions. Thus, if a cation exchange resin with a crosslinking degree of 6 or more is used, metal ion impurities are adsorbed with high selectivity to quaternary ammonium ions present in a large excess in the treated liquid, making it possible to reduce the metal ion concentration. The above mechanism becomes more pronounced, especially as the number of carbon atoms in the alkyl group of the quaternary ammonium ions increases. Furthermore, when the total number of carbon atoms in each alkyl group of the quaternary ammonium ion is the same, the above mechanism tends to be more pronounced in the above ions (i), (ii), and (iii) compared to those in which all the alkyl groups are the same.

[0035] However, this selective and excellent removal action is only significantly exerted at the beginning of the purification process when the crude quaternary ammonium compound aqueous solution contains a large amount of organic impurities with a molecular weight of 1000 g / mol or more, exceeding 1000 ppm. This is because, in the crude quaternary ammonium compound aqueous solution, the long molecular chains of the organic impurities are homogeneously dispersed in the liquid until the beginning of the purification process, and have almost no effect on the adsorption properties of the cation exchange resin, but as the purification process continues, they gradually become entangled with the surface of the resin particles, and eventually cover most of the surface. In other words, when most of the particle surface of the cation exchange resin is covered with organic impurities in this way, even metal ions are strongly hindered from diffusing into the inside, and the selective removal action is not smoothly exerted.

[0036] From the viewpoint of exerting the effect of removing the metal ions to a higher degree, the crosslinking degree of the cation exchange resin is preferably 8 or more, more preferably 11 or more, and particularly preferably 16 or more. In particular, when the ratio (flow rate) of the cation exchange resin to the crude quaternary ammonium compound aqueous solution described below exceeds 200 (L / L-resin), the crosslinking degree of the cation exchange resin is preferably 8 or more. On the other hand, when the content of organic impurities having a molecular weight of 1000 g / mol or more in the crude quaternary ammonium compound aqueous solution is below 100 ppm, sufficient effect can be obtained even if the flow rate exceeds 200 (L / L-resin) and the crosslinking degree of the cation exchange resin is 6 or more. Note that if the crosslinking degree of the cation exchange resin is too large, the diffusion rate of even metal ions becomes slow, and the capture rate of metals becomes slow, so that the crosslinking degree of the cation exchange resin is preferably 30 or less, more preferably 25 or less, and particularly preferably 22 or less.

[0037] The cation exchange resin may be in any shape, such as a gel type or a macroporous type, but the larger the contact area between the ion exchange resin and the liquid, the easier it is for metal ions to diffuse into the ion exchange resin, so the macroporous type is more preferably used in the present invention.

[0038] In addition, the cation exchange resin used in the present invention preferably has a cation exchange capacity of 1.0 to 5.0 equivalents / L, more preferably 1.5 to 3.0 equivalents / L. The resin body shape of the cation exchange resin is not particularly limited and may be a membrane or the like, but is usually preferably a particulate shape.

[0039] Here, it is necessary to use a non-metal ion type counter ion for the cation exchange resin. That is, the counter ion for the cation exchange resin is usually a hydrogen ion type or a metal ion type, but the metal ion type cannot be used in the present invention because the metal ion present as the counter ion is eluted in the purification step, preventing a reduction in the metal ion concentration in the purified aqueous solution of the quaternary ammonium compound obtained. Therefore, the counter ion for the cation exchange resin should be a cation other than a metal ion, specifically, the hydrogen ion, as well as an ammonium ion (NH 4 + ) or primary to quaternary ammonium ions, etc. are used.

[0040] In the present invention, the counter ion of the cation exchange resin is preferably a mixture of quaternary ammonium ion and hydrogen ion type, which is the same as that of the crude quaternary ammonium compound, or a hydrogen ion type, and more preferably a mixture of quaternary ammonium ion and hydrogen ion type, which is the same as that of the aqueous solution of the crude quaternary ammonium compound. 4 + ) or primary to quaternary ammonium ion types, unless the cation is the same quaternary ammonium ion as in the crude aqueous solution of quaternary ammonium compound, the elution of the other cation may cause contamination of the resulting aqueous solution of the purified quaternary ammonium compound with another ammonium compound, making separation difficult.

[0041] The cation exchange resin with a crosslinking degree of 6 or more and a non-metal ion type counter ion can be obtained as a non-metal ion type by contacting it with an aqueous solution containing cations other than metal ions to remove the metal ions when only metal ion type counter ions are available or when a certain amount of metal ions is contained and the metal ion concentration is to be reduced. However, as mentioned above, in a cation exchange resin with a high crosslinking degree, since large cations such as quaternary ammonium ions are difficult to diffuse into the resin, it is considered to contact it with an aqueous solution containing small cations that can easily penetrate into the resin and be quickly exchanged with metal ions. The preferred form is an aqueous solution in which the cations are hydrogen ions, that is, contacting it with an acid.

[0042] In the present invention, the cation exchange resin has a crosslinking degree of 6 or more and has a hydrogen ion type counter ion, and is used in contact with an aqueous solution of quaternary ammonium compounds having the same quaternary ammonium ion as the aqueous solution of the crude quaternary ammonium compounds. In other words, according to this treatment, some of the counter ions of the cation exchange resin remain hydrogen ions due to the influence of the diffusibility inhibition of the quaternary ammonium ion, but a significant amount of the hydrogen ions are exchanged for the same quaternary ammonium ions as the aqueous solution of the crude quaternary ammonium compounds. Thus, the cation exchange resin obtained has a significant proportion of counter ions exchanged for the same quaternary ammonium ions as the aqueous solution of the crude quaternary ammonium compounds. If the cation exchange resin is in such a state, it is preferable to prevent the phenomenon that the quaternary ammonium ions of the treated solution are adsorbed on the cation exchange resin at the start of the purification of the aqueous solution of the crude quaternary ammonium compounds according to the present invention, and the purified aqueous solution of quaternary ammonium compounds is produced with a temporary decrease in concentration.

[0043] As described above, even after contacting the aqueous solution of a quaternary ammonium compound having the same quaternary ammonium ion as the aqueous solution of the crude quaternary ammonium compound, some hydrogen ions remain as counter ions of the highly crosslinked cation exchange resin. The suitable amount of hydrogen ions remaining is preferably at least 1 mol % in hydrogen ion form, more preferably at least 3 mol %, even more preferably at least 10 mol %, and particularly preferably at least 20 mol %. The more hydrogen ions remaining, the more preferable it is because the amount of the aqueous solution of the crude quaternary ammonium compound that can be treated can be increased. In addition, the proportion of the counter ions of the cation exchange resin that are the same quaternary ammonium ions as the aqueous solution of the crude quaternary ammonium compound is preferably 99 mol % or less of the counter ions, more preferably 97 mol % or less, even more preferably 90 mol % or less, and particularly preferably 80 mol % or less, and the remaining counter ions are hydrogen ion type.

[0044] On the other hand, the crude quaternary ammonium compound aqueous solution can also be contacted with a hydrogen ion type cation exchange resin to purify the crude quaternary ammonium compound aqueous solution without eluting metals. However, when the crude quaternary ammonium compound aqueous solution is purified with such a cation exchange resin, the quaternary ammonium ions in the treated solution are adsorbed by the cation exchange resin, and the concentration of the purified quaternary ammonium compound aqueous solution temporarily decreases. In addition, the same amount of hydrogen ions as the adsorbed amount are eluted, so that the acid concentration temporarily increases and contamination occurs. For this reason, it is preferable to contact the crude quaternary ammonium compound aqueous solution with a quaternary ammonium compound aqueous solution having the same quaternary ammonium ions as the crude quaternary ammonium compound aqueous solution before purification, and to convert the counter ions other than the hydrogen ions remaining due to diffusion inhibition into quaternary ammonium ions in advance. The ratio of quaternary ammonium ions to exchange groups that can be exchanged with the same quaternary ammonium ions as the crude quaternary ammonium compound aqueous solution in the cation exchange resin before purification is preferably 60 mol% or more, more preferably 80 mol% or more, even more preferably 95 mol% or more, and particularly preferably 99 mol% or more.

[0045] As mentioned above, the counter ions of the cation exchange resin are non-metal ions, but this does not mean that all the counter ions are completely other than metal ions, and as long as the effect is not significantly affected, it is acceptable for metal ions to be inevitably mixed in. Specifically, metal ions are acceptable within the scope of the present invention if they are contained in an amount of 3 mol % or less, preferably 0.1 mol % or less, and particularly preferably 0.001 mol % or less of the counter ions.

[0046] In the present invention, the counter ions of the cation exchange resin are brought into contact with an acid to elute metal ions and nonmetallic ions other than hydrogen ions, and each component can be quantified by ion chromatography. Hydrogen ions can be quantified by contacting the resin with a salt to elute hydrogen ions, and then performing neutralization titration.

[0047] Here, the aqueous acid solution used for contact with the cation exchange resin having a metal ion type counter ion is an aqueous inorganic acid solution such as sulfuric acid, hydrochloric acid, or nitric acid, and from the viewpoint of preventing deterioration of the resin material, it is preferable to use an aqueous hydrochloric acid solution or an aqueous sulfuric acid solution. The concentration of the acid can be used without any restrictions, but since contact with a high concentration acid may cause cracks or breakage due to the counter ion being replaced in a short time and causing a sudden change in volume, it is preferably 1 mol / L or less, more preferably 0.5 mol / L or less, and even more preferably 0.3 mol / L or less. From the viewpoint of sufficiently eluting ions other than hydrogen ions contained in the counter ion of the cation exchange resin, it is preferable to treat with an acid equivalent to 1.2 to 5 times the total amount of exchange groups of the cation exchange resin used, and more preferably 1.5 to 3.5 times the total amount of exchange groups of the cation exchange resin used.

[0048] The contact treatment may be a batch type or a liquid-passing type, but is not particularly limited. In the case of a liquid-passing type in which a resin tower is formed, either an ascending flow or a descending flow may be used, and it is preferable to pass an acid containing an amount equivalent to at least three times the amount of exchange groups of the ion exchange resin to be treated, and although there is no particular specification for the liquid passing speed, it is preferable to perform the treatment in the range of SV=1 to 20 (1 / hr) from the viewpoint of treatment time and efficiency. In addition, in the case of a batch type, it is preferable to exchange the liquid three or more times with an acid equivalent to 3 to 15 times the total amount of exchange groups of the cation exchange resin to be treated.

[0049] In addition, if the content of metal ions contained in the acid aqueous solution is high, metal ions will remain in the cation exchange resin depending on the concentration, and the amount of metal ions exchanged during purification may decrease, or in some cases, they may be released and cause contamination. For this reason, it is preferable that the total content of metal impurities consisting of Na, K, Li, Ca, Mg, and Sr contained in the acid aqueous solution is 100 ppt or less, more preferably 10 ppt or less, and even more preferably 1 ppt or less. Furthermore, it is preferable that the total content of metal impurities consisting of Fe, Ni, Cu, and Pb in the acid aqueous solution is also 100 ppt or less, more preferably 10 ppt or less, and even more preferably 1 ppt or less.

[0050] After contacting the cation exchange resin with the acid aqueous solution, it is preferable to wash the cation exchange resin with ultrapure water. This removes excess acid that has not been incorporated as a counter ion by adhering to the surface of the resin, and prevents the acid from being mixed into the subsequent steps. In particular, when the quaternary ammonium compound contained in the crude quaternary ammonium compound aqueous solution is a quaternary ammonium hydroxide, if acid remains in the cation exchange resin, a sudden heat generation occurs due to a neutralization reaction, and the resin may be destroyed due to a sudden swelling of the resin. Therefore, washing with ultrapure water is preferable.

[0051] In addition, when the cation exchange resin having a hydrogen ion counterion is contacted with the aqueous solution of a quaternary ammonium compound having the same quaternary ammonium ion as the aqueous solution of the crude quaternary ammonium compound, the aqueous solution of the quaternary ammonium compound is preferably used in the same concentration, contact method, and metal ion content as those described for the aqueous acid solution. In particular, if the aqueous solution of a quaternary ammonium compound having the same quaternary ammonium ion as the aqueous solution of the crude quaternary ammonium compound is treated with an aqueous solution of a quaternary ammonium compound having the same quaternary ammonium ion as the aqueous solution of the crude quaternary ammonium compound, which is 1.5 to 3.5 times the total amount of exchange groups of the cation exchange resin used, the ratio of the quaternary ammonium ion to the exchange groups exchangeable with the same quaternary ammonium ion as the aqueous solution of the crude quaternary ammonium compound in the cation exchange resin becomes 99 mol % or more, which is preferable. In addition, as the aqueous solution of a quaternary ammonium compound having the same quaternary ammonium ion as the aqueous solution of the crude quaternary ammonium compound, hydroxide, chloride, bromide salt, carbonate, etc. can be used, but hydroxide is preferable. In the case of hydroxide, hydrogen ions eluted from the cation exchange resin immediately form hydroxide ions and water, so that the hydrogen ion concentration in the liquid does not increase, and it is possible to efficiently proceed with the exchange to quaternary ammonium ions. Furthermore, it is also preferable to wash the cation exchange resin with ultrapure water after contacting it with the aqueous solution of the quaternary ammonium compound.

[0052] Next, in the present invention, the method of contacting the cation exchange resin with the crude aqueous solution of quaternary ammonium compound may be any type, such as a batch type or a liquid-passing type, but industrially, the liquid-passing type is preferable. In the liquid-passing type, purification is performed by passing the liquid through a resin tower. The liquid passing direction may be either an upward flow or a downward flow, and from the viewpoint of increasing purification efficiency, a downward flow is preferable. The liquid passing conditions are preferably a space velocity SV of 1 to 20 (1 / hr), more preferably 5 to 20 (1 / hr), and even more preferably 8 to 20.

[0053] The treatment amount of the crude quaternary ammonium compound aqueous solution to be contacted is generally 100 (L / L-resin) or more for efficiency. As described above, the excellent metal ion removal effect in the method of the present invention is notably exhibited when a large amount of the crude quaternary ammonium compound aqueous solution is treated, so that the treatment amount is more effective when the cation exchange resin is 2000 (L / L-resin) or more, more preferably 10,000 (L / L-resin) or more relative to the crude quaternary ammonium compound aqueous solution. However, if the treatment amount is still too large, the metal ion removal effect is reduced, so the treatment amount is generally 10 8 (L / L-resin) or less, particularly preferably 50,000 (L / L-resin) or less.

[0054] It is efficient to subject the cation exchange resin in which the metal ion removal effect has been reduced in this way to the above-mentioned acid treatment as a resin regeneration treatment, and then resume the flow of liquid and repeat purification. In addition, the liquid may be passed through two or more resin towers in succession.

[0055] On the other hand, in the batch purification, it is preferable to immerse the resin in an aqueous solution of a crude quaternary ammonium compound at 200 L / L or more in order to significantly exhibit the excellent effect of removing the metal ions. It is also preferable to repeat the batch treatment, since the metal ions can be further reduced. The number of repetitions is preferably 2 to 5 times.

[0056] In the method of the present invention, when the crude quaternary ammonium compound aqueous solution contains particulate metal impurities, it is preferable to remove them by performing a filter treatment as a pre- or post-step before contacting with a cation exchange resin. If particulate metal impurities or resin particles are contained in the crude quaternary ammonium compound aqueous solution, they may hinder the action of the cation exchange resin in removing metal ions in the present invention, or may cause clogging in the case of a flow-through type, so it is preferable to perform a filter treatment as a pre-treatment. In addition, since there is a risk that particulate metal impurities remaining after contact with the cation exchange resin and, in some cases, broken pieces of the cation exchange resin may be mixed in, it is also preferable to perform the filter treatment as a post-treatment.

[0057] The average pore size of the filter used is preferably 1 μm or less, and more preferably 0.02 to 1 μm. When the average pore size of the filter is unknown, the value measured by the bubble point method is used as the average pore size.

[0058] The inner walls of the equipment such as containers, tanks, resin towers, and piping used to carry out the production method of the present invention are desirably made of a material that is resistant to chemicals and minimizes metal contamination. Therefore, it is preferable that they are made of or lined with polyethylene, polypropylene, or fluororesin materials. In particular, fluororesin is optimal from the viewpoint of preventing metal contamination. It is preferable to clean the surfaces of these members before use, for example, by cleaning them with an aqueous solution of a quaternary ammonium hydroxide compound or an acid.

[0059] By the above method, a purified aqueous solution of quaternary ammonium compound with reduced metal ions can be effectively produced. Specifically, it is possible to obtain an aqueous solution of quaternary ammonium compound in which the total content of metal impurities consisting of Na, K, Li, Ca, Mg, and Sr is 100ppt or less, more preferably 50ppt or less, and even more preferably 20ppt or less. The aqueous solution of quaternary ammonium compound can also have the content of each of these metal elements be 30ppt or less, more preferably 10ppt or less, and even more preferably 5ppt or less.

[0060] In addition, when the quaternary ammonium compound is a hydroxide salt, the aqueous solution of the quaternary ammonium compound may take the form of anion or non-ion in some metal elements other than the above-mentioned metal elements due to its strong alkalinity, and the removal effect may be insufficient. However, when the quaternary ammonium compound is a halogenated quaternary ammonium compound or a carbonated quaternary ammonium compound other than the hydroxide, the effect of reducing the other metal elements is also high. Therefore, when the counter ion is other than the hydroxide, it is also possible to obtain an aqueous solution of the quaternary ammonium compound in which the total content of metal impurities consisting of Fe, Ni, Cu, and Pb is 100 ppt or less, more preferably 50 ppt or less, and even more preferably 20 ppt or less. EXAMPLES

[0061] Examples are given below to specifically explain the present invention, but the present invention is not limited to these. The physical properties measured in the examples and comparative examples were determined by the following methods.

[0062] 1) Content of metal impurities in aqueous solutions of quaternary ammonium compounds The concentrations of Na, K, Li, Ca, Mg, Sr, Fe, Ni, Cu, and Pb were measured using an inductively coupled plasma mass meter (ICP-MS). The lower limit of measurement was 1 ppt, and values ​​below 1 ppt were considered to be <1 ppt.

[0063] 2) The content of organic impurities with a molecular weight of 1000 g / mol or more contained in the aqueous solution of quaternary ammonium compounds A sample of the crude quaternary ammonium compound aqueous solution was injected into a GPC column, and the solution containing 1000 g / mol or more of organic impurities was separated and collected. The TOC concentration of the collected solution and the eluent used for separation by GPC were each measured using a TOC meter. The TOC concentration of the eluent was subtracted from the TOC concentration of the collected solution, and this was multiplied by the dilution factor of the crude quaternary ammonium compound aqueous solution in the collected solution to obtain the concentration of organic impurities in the crude quaternary ammonium compound aqueous solution.

[0064] 3) The ratio of quaternary ammonium ions and hydrogen ions contained in the counter ions of the cation exchange resin The cation exchange resin that had been subjected to the pretreatment shown in the Examples was contacted with sodium chloride to elute hydrogen ions, and the resulting liquid was subjected to neutralization titration with sodium hydroxide to quantify the hydrogen ions contained in the counter ions. The same cation exchange resin was also contacted with hydrochloric acid (where all counter ions were hydrogen ions), washed with ultrapure water, and contacted again with sodium chloride to quantify the hydrogen ions in the resulting liquid by neutralization titration with sodium hydroxide to determine the amount of exchange groups on the cation exchange resin. Since the counter ions of the pretreated cation exchange resin consist of quaternary ammonium ions and hydrogen ions, the amount of quaternary ammonium ions can be calculated by subtracting the amount of hydrogen ions calculated initially from the amount of exchange groups. The amount of quaternary ammonium ions and the amount of hydrogen ions were divided by the amount of exchange groups to determine the ratio.

[0065] [Quaternary ammonium compound aqueous solution] Ethyltrimethylammonium chloride (prepared from raw materials) Ethyltrimethylammonium hydroxide (prepared from the above ethyltrimethylammonium chloride) Tetramethylammonium chloride (commercially available from company A, general grade) Tetramethylammonium hydroxide (Tokuyama, 25% aqueous solution)

[0066] Ethyltrimethylammonium chloride was prepared by the following procedure: Trimethylamine and ethyl chloride were charged in a molar ratio of 1:1 into a reaction vessel containing ultrapure water, and the reaction temperature was maintained at 60°C to prepare a 60% by mass aqueous solution of ethyltrimethylammonium chloride.

[0067] Ethyltrimethylammonium hydroxide was produced by the following procedure using an electrolytic cell having a power source 3 shown in Fig. 1. A platinum-plated nickel plate was used as the cathode 2, a platinum-plated titanium plate was used as the anode 1, two Nafion N324 (manufactured by Chemours) were used as the cation exchange membrane 9, and ASE (manufactured by Astom) was used as the anion exchange membrane 8. 0.5N hydrochloric acid was circulated in the anode chamber 4, an aqueous solution of ethyltrimethylammonium chloride adjusted to 50 mass% was circulated in the raw material chamber 5 between the anion exchange membrane 8 and the cation exchange membrane 9 on the cathode side, and ultrapure water was circulated in the intermediate chamber 6 between the cathode chamber 7 and the two cation exchange membranes 9, and the current density was gradually increased until a current density of 30 A / dm was finally achieved. 2 Electrolysis was performed continuously while maintaining the temperature at 40° C. During electrolysis, an aqueous solution of ethyltrimethylammonium chloride was replenished so that the concentration of ethyltrimethylammonium chloride in the raw material chamber 5 was maintained at 40% by mass or more, and ultrapure water was added to adjust the concentration of ethyltrimethylammonium hydroxide obtained from the cathode chamber 7 to a constant value of 25% by mass. Ethyltrimethylammonium hydroxide was obtained continuously by appropriately extracting the liquid from the cathode chamber 7. Ethyltrimethylammonium hydroxide used for pretreatment of the cation exchange resin was treated with 0.3 mol / L hydrochloric acid and ultrapure water, and then passed through Amberlite 200CT Na (crosslinking degree 20, cation exchange capacity 1.7 equivalents / L, manufactured by Organo Corporation) to reduce the metal concentration.

[0068] Example 1 The content of metal impurities in the prepared 60% by mass aqueous solution of crude ethyltrimethylammonium chloride was measured, and the total content of metal impurities consisting of Na, K, Li, Ca, Mg, and Sr is shown in Table 1, and the total content of metal impurities consisting of Fe, Ni, Cu, and Pb is shown in Table 2. In addition, the content of organic impurities having a molecular weight of 1000 g / mol or more was measured and found to be 233 ppm.

[0069] Next, 50 mL of Amberlite 200CT Na (crosslinking degree 20, cation exchange capacity 1.7 equivalents / L, manufactured by Organo Corporation), a strong acid ion exchange resin, was packed into a column having a diameter of 22 mm and a length of 750 mm. 1) Ultrapure water cleaning, 2) 0.3 mol / L hydrochloric acid treatment, 3) Ultrapure water treatment, 4) Treatment with 0.3 mol / L ethyltrimethylammonium hydroxide aqueous solution 5) Ultrapure water treatment The amount of each liquid passed was 600 mL, and the space velocity was SV=5 (1 / hr).

[0070] The 0.3 mol / L hydrochloric acid and 0.3 mol / L ethyltrimethylammonium hydroxide aqueous solution each had a total content of metal impurities consisting of Na, K, Li, Ca, Mg, and Sr of 100 ppt or less, and a total content of metal impurities consisting of Fe, Ni, Cu, and Pb of 100 ppt or less. The ultrapure water used had a total content of metal impurities consisting of Na, K, Li, Ca, Mg, Sr, Fe, Ni, Cu, and Pb of 1 ppt or less. The ratios of quaternary ammonium ions and hydrogen ions contained in the counter ions of the strongly acidic ion exchange resin after the pretreatment were measured, and the ratio was 77 mol % for quaternary ammonium ions and 23 mol % for hydrogen ions.

[0071] 1050L of crude tetramethylammonium chloride aqueous solution was passed through the column under the condition of SV=20 (1 / hr). After the amount of passing liquid reached 10L (200L / L-resin), 100L (2000L / L-resin), 500L (10000L / L-resin), and 1000L (20000L / L-resin), 10L of each liquid was sampled and the content of metal impurities was measured. The results are shown in Tables 1 and 2, respectively.

[0072] Example 2 The same operation as in Example 1 was carried out except that the strongly acidic ion exchange resin used was changed to Diaion UBK16 (crosslinking degree 16, cation exchange capacity 2.3 equivalents / L, Mitsubishi Chemical Corporation). The ratio of quaternary ammonium ions contained in the counter ions of the strongly acidic ion exchange resin after pretreatment was 87 mol %, and the ratio of hydrogen ions was 13 mol %. The measurement results of the metal impurity content are shown in Tables 1 and 2, respectively.

[0073] Example 3 The same operation as in Example 1 was carried out except that the strongly acidic ion exchange resin used was changed to Diaion SK112 (crosslinking degree 12, cation exchange capacity 2.1 equivalents / L, manufactured by Mitsubishi Chemical Corporation). The ratio of quaternary ammonium ions contained in the counter ions of the strongly acidic ion exchange resin after pretreatment at this time was 95 mol %, and the ratio of hydrogen ions was 5 mol %. The measurement results of the metal impurity content are shown in Tables 1 and 2 above, respectively.

[0074] Example 4 In Example 1, the strongly acidic ion exchange resin used was changed to Diaion SK1B (crosslinking degree 8, cation exchange capacity 2.0 equivalents / L, manufactured by Mitsubishi Chemical Corporation), but the same operation as in Example 1 was performed. The ratio of quaternary ammonium ions contained in the counter ions of the strongly acidic ion exchange resin after pretreatment at this time was 97 mol %, and the ratio of hydrogen ions was 3 mol %. The measurement results of the metal impurity content are shown in Tables 1 and 2, respectively.

[0075] Example 5 The same operation as in Example 1 was carried out except that the strongly acidic ion exchange resin used in Example 1 was changed to Diaion PK212 (crosslinking degree 6, cation exchange capacity 1.5 equivalents / L, manufactured by Mitsubishi Chemical Corporation). The ratio of quaternary ammonium ions contained in the counter ions of the strongly acidic ion exchange resin after pretreatment at this time was 99 mol %, and the ratio of hydrogen ions was 1 mol %. The measurement results of the metal impurity content are shown in Tables 1 and 2 above, respectively.

[0076] [Table 1]

[0077] [Table 2]

[0078] Comparative Example 1 A 60% by mass aqueous solution of crude ethyltrimethylammonium chloride was prepared using ethyltrimethylammonium chloride prepared separately from Example 1. The total content of metal impurities Na, K, Li, Ca, Mg, and Sr in the aqueous solution of crude ethyltrimethylammonium chloride is shown in Table 3, and the total content of metal impurities Fe, Ni, Cu, and Pb is shown in Table 4. The content of organic impurities having a molecular weight of 1000 g / mol or more was measured and found to be 1721 ppm.

[0079] The thus-prepared crude tetramethylammonium chloride aqueous solution was subjected to measurement of the metal impurity content by the same operation as in Example 1. The liquid for measuring the metal impurity content was collected in an amount of 10 L (200 L / L-resin) and 100 L (2000 L / L-resin). The measurement results of the metal impurity content are shown in Tables 3 and 4, respectively.

[0080] [Table 3]

[0081] [Table 4]

[0082] Examples 6 to 10 The metal impurity content of the prepared 25% by mass aqueous crude ethyltrimethylammonium hydroxide solution was measured, and the results are shown in Tables 5 and 6. The content of organic impurities having a molecular weight of 1000 g / mol or more was also measured, and was found to be 26 ppm.

[0083] The same operations as in Examples 1 to 5 were carried out except for using the crude tetramethylammonium hydroxide aqueous solution thus prepared (Example 6 corresponds to Example 1, Example 7 corresponds to Example 2, Example 8 corresponds to Example 3, Example 9 corresponds to Example 4, and Example 10 corresponds to Example 5). The measurement results of the metal impurity contents are shown in Tables 5 and 6, respectively.

[0084] [Table 5]

[0085] [Table 6]

[0086] Comparative Example 2 A powder of synthetic tetramethylammonium chloride (commercially available from Company A, general grade) was dissolved in water and adjusted to 60% by mass to prepare a crude tetramethylammonium chloride aqueous solution. The content of metal impurities in this crude tetramethylammonium chloride aqueous solution was measured, and the total content of metal impurities consisting of Na, K, Li, Ca, Mg, and Sr is shown in Table 7, and the total content of metal impurities consisting of Fe, Ni, Cu, and Pb is shown in Table 8. The content of organic impurities with a molecular weight of 1000 g / mol or more was also measured, and was found to be 372 ppm.

[0087] Next, 50 mL of Amberlite 200CT Na (crosslinking degree 20, cation exchange capacity 1.7 equivalents / L, manufactured by Organo Corporation), a strong acid ion exchange resin, was packed into a column having a diameter of 22 mm and a length of 750 mm. 1) Ultrapure water cleaning, 2) 0.3 mol / L hydrochloric acid treatment, 3) Ultrapure water treatment, 4) Treatment with 0.3 mol / L tetramethylammonium hydroxide aqueous solution 5) Ultrapure water treatment The amount of each liquid passed was 600 mL, and the space velocity was SV=5 (1 / hr).

[0088] The 0.3 mol / L hydrochloric acid and 0.3 mol / L tetramethylammonium hydroxide aqueous solution each had a total content of metal impurities consisting of Na, K, Li, Ca, Mg, and Sr of 100 ppt or less, and a total content of metal impurities consisting of Fe, Ni, Cu, and Pb of 100 ppt or less. The ultrapure water used had a total content of metal impurities consisting of Na, K, Li, Ca, Mg, Sr, Fe, Ni, Cu, and Pb of 1 ppt or less. The ratios of quaternary ammonium ions and hydrogen ions contained in the counter ions of the strongly acidic ion exchange resin after the pretreatment were measured, and the ratio was 80 mol % for quaternary ammonium ions and 20 mol % for hydrogen ions.

[0089] A crude tetramethylammonium chloride aqueous solution was passed through the column at 1050 L under the condition of SV=20 (1 / hr). After the amount of the solution passed reached 10 L (200 L / L-resin), 100 L (2000 L / L-resin), 500 L (10000 L / L-resin), and 1000 L (20000 L / L-resin), 10 L of each solution was sampled and the content of metal impurities was measured. The results are shown in Tables 7 and 8, respectively.

[0090] Comparative Example 3 In Comparative Example 2, the strongly acidic ion exchange resin used was changed to Diaion UBK16 (crosslinking degree 16, cation exchange capacity 2.3 equivalents / L, Mitsubishi Chemical Corporation), but the same operation as in Example 1 was performed. The ratio of quaternary ammonium ions contained in the counter ions of the strongly acidic ion exchange resin after pretreatment at this time was 89 mol %, and the ratio of hydrogen ions was 11 mol %. The measurement results of the metal impurity content are shown in Tables 7 and 8, respectively.

[0091] Comparative Example 4 In Comparative Example 2, the strongly acidic ion exchange resin used was changed to Diaion SK112 (crosslinking degree 12, cation exchange capacity 2.1 equivalents / L, manufactured by Mitsubishi Chemical Corporation), but the same operation as in Example 1 was performed. The ratio of quaternary ammonium ions contained in the counter ions of the strongly acidic ion exchange resin after pretreatment at this time was 97 mol %, and the ratio of hydrogen ions was 3 mol %. The measurement results of the metal impurity content are shown in Tables 7 and 8, respectively.

[0092] Comparative Example 5 In Comparative Example 2, the strongly acidic ion exchange resin used was changed to Diaion SK1B (crosslinking degree 8, cation exchange capacity 2.0 equivalents / L, manufactured by Mitsubishi Chemical Corporation), but the same operation as in Example 1 was performed. The proportion of quaternary ammonium ions contained in the counter ions of the strongly acidic ion exchange resin after pretreatment at this time was 99 mol %, and the proportion of hydrogen ions was 1 mol %. The measurement results of the metal impurity content are shown in Tables 7 and 8, respectively.

[0093] Comparative Example 6 In Comparative Example 2, the strongly acidic ion exchange resin used was changed to Diaion PK212 (crosslinking degree 6, cation exchange capacity 1.5 equivalents / L, manufactured by Mitsubishi Chemical Corporation), but the same operation as in Example 1 was performed. The proportion of quaternary ammonium ions contained in the counter ions of the strongly acidic ion exchange resin after pretreatment at this time was 99.9 mol % or more, and the proportion of hydrogen ions was 0.1 mol %. The measurement results of the metal impurity content are shown in Tables 7 and 8, respectively.

[0094] [Table 7]

[0095] [Table 8]

[0096] Comparative Examples 7 to 11 The metal impurity content of the 25% by mass aqueous solution of crude tetramethylammonium hydroxide was measured, and the results are shown in Tables 9 and 10. The content of organic impurities having a molecular weight of 1000 g / mol or more was also measured, and was found to be 43 ppm.

[0097] The same operations as in Comparative Examples 2 to 6 were carried out except that the crude tetramethylammonium hydroxide aqueous solution thus prepared was used (Comparative Example 7 corresponds to Comparative Example 2, Comparative Example 8 corresponds to Comparative Example 3, Comparative Example 9 corresponds to Comparative Example 4, Comparative Example 10 corresponds to Comparative Example 5, and Comparative Example 11 corresponds to Comparative Example 6). The measurement results of the metal impurity contents are shown in Tables 9 and 10, respectively.

[0098] [Table 9]

[0099] [Table 10]

[0100] In Examples 1 to 10, in which a crude aqueous solution of quaternary ammonium in which the quaternary ammonium ion is ethyltrimethylammonium ion and in which the content of organic impurities having a molecular weight of 1000 g / mol or more is 1000 ppm or less is treated, excellent reduction effects of metal impurity concentration are exhibited in all cases at the beginning of treatment when the amount of liquid passing is 10 L (200 L / L-resin) by contact with a cation exchange resin in which the crosslinking degree is 6 or more and the counter ion is a non-metal ion type. Moreover, compared with Comparative Examples 2 to 11, in which a crude aqueous solution of quaternary ammonium in which the quaternary ammonium ion is tetramethylammonium ion is treated, metal impurities can be removed even in cases of lower crosslinking, and the removal effect is maintained even in cases of higher liquid passing amounts.

[0101] Furthermore, in Comparative Example 1, in which the crude aqueous quaternary ammonium solution to be treated contained a large amount of organic impurities with a molecular weight of 1000 g / mol or more exceeding 1000 ppm, metal impurities were removed to a certain extent at the beginning of treatment when the amount of liquid passed was 10 L (200 L / L-resin), but the effect rapidly decreased when the amount of liquid passed was continued to 100 L (2000 L / L-resin). [Explanation of symbols]

[0102] 1: Anode 2: Cathode 3: Power supply 4:Anode chamber 5: Raw material room 6: Intermediate chamber 7: Cathode chamber 8: Anion exchange membrane 9: Cation exchange membrane

Claims

1. A method for producing an aqueous solution of a quaternary ammonium compound, comprising the steps of: The aqueous solution of a quaternary ammonium compound contains 1000 ppm or less of organic impurities having a molecular weight of 1000 g / mol or more, and contains a quaternary ammonium ion represented by the following formula (1), and further contains a crude aqueous solution of a quaternary ammonium compound containing metal impurities. A method for producing a purified aqueous solution of a quaternary ammonium compound, comprising contacting the compound with a cation exchange resin having a crosslinking degree of 6 or more and having a non-metallic ion type counter ion. 【Chemistry 1】 (In the formula, R １ , R ２ , R ３ , and R ４ are each independently an alkyl group having 1 to 16 carbon atoms, provided that R １ , R ２ , R ３ , and R ４ Among these, at least one alkyl group has 2 to 16 carbon atoms.

2. R in the above formula (1) １ , R ２ , R ３ , and R ４ 2. The method for producing a purified aqueous solution of a quaternary ammonium compound according to claim 1, wherein not all of are the same alkyl group.

3. R in the above formula (1) １ , R ２ , R ３ , and R ４ The method for producing a purified aqueous solution of a quaternary ammonium compound according to claim 1, wherein three of the groups are the same and the remaining one is an alkyl group having 2 to 16 carbon atoms different from the groups.

4. The method for producing a purified aqueous solution of a quaternary ammonium compound according to any one of claims 1 to 3, wherein the crosslinking degree of the cation exchange resin is 8 to 30.

5. The method for producing a purified aqueous solution of a quaternary ammonium compound according to any one of claims 1 to 3, wherein the cation exchange resin is composed of a strongly acidic cation exchange resin.

6. The method for producing a purified aqueous solution of a quaternary ammonium compound according to any one of claims 1 to 3, wherein the contact of the crude aqueous solution of a quaternary ammonium compound with the cation exchange resin is carried out in a flow-through manner, and the contact is carried out under conditions of a space velocity SV of 1 to 20 (1 / hr) and a treatment amount of the crude aqueous solution of a quaternary ammonium compound with the cation exchange resin of 2000 (L / L-resin) or more.

7. The method for producing a purified aqueous solution of a quaternary ammonium compound according to any one of claims 1 to 3, wherein the cation exchange resin is obtained by contacting a cation exchange resin having a hydrogen ion type counter ion with an aqueous solution of a quaternary ammonium compound having the same quaternary ammonium ion as that of the crude aqueous solution of a quaternary ammonium compound.

8. The method for producing a purified aqueous quaternary ammonium compound solution according to any one of claims 1 to 3, wherein the crude aqueous quaternary ammonium compound solution is a crude aqueous quaternary ammonium hydroxide compound solution, a crude aqueous quaternary ammonium halide compound solution, or a crude aqueous quaternary ammonium carbonate compound solution.

Images