Method and apparatus for producing halogen oxygen acid solution

Abstract

To provide a manufacturing method and a manufacturing apparatus which are industrially useful in manufacturing a halogen oxyacid solution.SOLUTION: A method for manufacturing a halogen oxyacid solution includes mixing an organic alkali solution and halogen while continuously supplying both to a stationary mixer so as to continuously obtain generated halogen oxyacid.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for producing a halogen oxygen acid solution, such as a quaternary alkylammonium hypochlorite solution. More specifically, the present invention provides an apparatus and method for industrially advantageously producing a halogen oxygen acid solution, such as a quaternary alkylammonium hypochlorite solution, having excellent storage stability. [Background technology]

[0002] In recent years, the design rules for semiconductor devices have become increasingly finer, leading to stricter requirements for impurity control in the semiconductor device manufacturing process. Because the impurities generated in the semiconductor device manufacturing process differ for each manufacturing step, it is important to identify the source of contamination for each manufacturing step and to control the concentration of the impurities that cause the contamination. Furthermore, large-diameter semiconductor wafers exceeding 300 mm are being used to improve the manufacturing efficiency of semiconductor devices. Large-diameter semiconductor wafers have larger edge and back surface areas where electronic devices are not fabricated compared to small-diameter semiconductor wafers. Therefore, during processes for forming metal wiring and barrier metal, metal wiring materials and barrier metal materials (hereinafter sometimes collectively referred to as "metal materials, etc.") are more likely to adhere not only to the surface of the semiconductor wafer where semiconductor devices are formed, but also to the edge and back surfaces. As a result, the amount of excess metal materials adhering to the edge and back surfaces of large-diameter semiconductor wafers is greater than that of small-diameter wafers.

[0003] Excess metal materials adhering to the edge or backside of semiconductor wafers can contaminate the manufacturing equipment as metal or metal oxide particles during the oxygen ashing process and plasma dry etching process, which are processes that occur after the formation of metal wiring and barrier metal, and can cause cross-contamination. For this reason, metal materials adhering to the edge or backside must be removed before the wafer is brought into the next process. Among these metal materials, precious metals such as platinum and ruthenium are difficult to oxidize, dissolve, and remove in subsequent etching and cleaning processes. Therefore, it is preferable to remove these precious metals from semiconductor wafers in preference to other metal materials. In particular, ruthenium is widely used as a wiring material for semiconductor device design rules of 10 nm or less because it can reduce resistance compared to copper. Therefore, it is desirable to quickly remove ruthenium from unnecessary areas.

[0004] Generally, cleaning methods using hypochlorite, which has a high oxidizing power, as a cleaning solution for semiconductor wafers have been proposed. Specifically, a method using an aqueous solution of sodium hypochlorite has been proposed (see Patent Documents 1 and 2). However, in the method of using a sodium hypochlorite aqueous solution as a cleaning solution, the cleaning solution inevitably contains a large amount of sodium ions, which may result in the sodium ions easily adhering to semiconductor wafers and the like, thereby reducing the semiconductor production efficiency. In response to this, development has been carried out of cleaning solutions that do not contain sodium as an essential component, such as hypochlorous acid solutions (see Patent Document 3) or aqueous solutions of quaternary alkylammonium hypochlorite (see Patent Document 4). However, these cleaning solutions using hypochlorous acid (see Patent Document 3) are used to clean substrates with metal films or metal oxide films, and are not specifically intended to remove precious metals, and therefore are not suitable for cleaning metal / metal oxide films such as precious metals.

[0005] On the other hand, the cleaning solution containing tetramethylammonium hypochlorite aqueous solution described in Patent Document 4 is also a cleaning solution used for cleaning photoresist and residues, and contains ruthenium. Copper and aluminum metal coatings are not targeted for cleaning. Specific examples show that metal films are difficult to etch. Patent Document 5 shows that optimizing the pH of a quaternary alkylammonium hypochlorite solution results in etching performance with excellent storage stability. However, the production methods described in Patent Documents 4 and 5 are batch reactions in which chlorine gas is supplied to a tetramethylammonium hydroxide solution for a certain period of time to produce a tetramethylammonium hypochlorite solution. Furthermore, the production method described in Patent Document 4 discloses that, to produce 160 g of tetramethylammonium hypochlorite solution, chlorine gas is supplied for approximately 6 minutes and a 250 ml Erlenmeyer flask is used as the reactor, and as an industrial production method, there is a problem in that the production efficiency per volume is low. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-161381 [Patent Document 2] Japanese Patent Application Laid-Open No. 2009-081247 [Patent Document 3] Japanese Patent Application Laid-Open No. 2003-119494 [Patent Document 4] Japanese Patent Application Laid-Open No. 2005-227749 [Patent Document 5] International Publication No. 2019 / 225541 Summary of the Invention [Problem to be solved by the invention]

[0007] Therefore, an object of the present invention is to provide a method and apparatus for producing a halogen oxyacid solution by reacting an organic alkaline solution with a halogen, which method and apparatus increase production efficiency per reaction volume and are industrially advantageous. [Means for solving the problem]

[0008] As a result of extensive research conducted by the inventors to achieve the above object, the inventors have provided a method for producing an organic alkaline solution more efficiently than a batch reaction by continuously supplying an organic alkaline solution and a halogen to a static mixer and mixing them at least once, and continuously removing the halogen oxyacid solution produced.

[0009] That is, the present invention is configured as follows. Item 1. A method for producing a halogen oxygen acid solution, comprising continuously supplying an organic alkaline solution and a halogen to a static mixer and mixing them, and continuously obtaining the resulting halogen oxygen acid. Item 2. The method for producing a halogen oxygen acid solution according to Item 1, wherein the supply ratio of the raw materials is controlled so that the pH at 25°C of the mixture of the organic alkali solution and the halogen that has passed through the static mixer is greater than 10.5 and less than 14.1. Item 3. The method for producing a halogen oxygen acid solution according to Item 2, wherein the pH of the mixture at 25° C. is 12.0 or more and 13.8 or less. Item 4. The production method according to any one of Items 1 to 3, wherein the halogen is supplied in multiple stages. Item 5. The method for producing a halogen oxygen acid solution according to any one of Items 1 to 4, wherein the mixing is carried out in multiple stages. Item 6. The method for producing a halogen oxygen acid solution according to any one of Items 1 to 5, wherein the static mixer is an ejector, an impingement type static mixer, or a Sulzer type static mixer. Item 7. The method for producing a halogen oxygen acid solution according to any one of Items 1 to 6, wherein the halogen oxygen acid solution is taken out without being recycled in the production process. Item 8. The method for producing a halogen oxygen acid solution according to any one of Items 1 to 7, wherein the organic alkaline solution has a pH at 25° C. of 10.5 or more and 14.5 or less. Item 9: The organic alkali is onium hydroxide, and the halogen oxygen acid is a halogen oxygen acid. Item 9. A method for producing a halogen oxygen acid solution according to any one of items 1 to 8, wherein the halogen oxygen acid is an onium. Item 10. The method for producing a halogen oxygen acid solution according to Item 9, wherein the onium hydroxide is a quaternary alkylammonium hydroxide, and the onium halogen oxygen acid is a quaternary alkylammonium hypohalite. Item 11. The method for producing a halogen oxygen acid solution according to any one of Items 1 to 10, wherein the quaternary alkylammonium hydroxide is tetramethylammonium hydroxide. Item 12. The method for producing a halogen oxygen acid solution according to any one of Items 1 to 11, wherein the halogen is chlorine, bromine, hypochlorous acid, hypobromous acid, chlorous acid, bromous acid, chloric acid, bromic acid, iodine, hypoiodous acid, iodous acid, or iodic acid. Item 13. The method for producing a halogen oxygen acid solution according to any one of Items 1 to 12, wherein the halogen is chlorine. Item 14: An apparatus for producing a halogen oxygen acid solution, comprising a static mixer, an organic alkali solution supply means and a halogen supply means to the static mixer, and a reaction solution removal means for removing the reaction solution from the static mixer to the outside, An apparatus for producing a halogen oxygen acid solution, in which an organic alkaline solution and a halogen are continuously supplied to a static mixer by an organic alkaline solution supply means and a halogen supply means, respectively, and mixed together to produce a halogen oxygen acid solution as a reaction liquid, and the reaction liquid is continuously taken out by a reaction liquid take-out means. Item 15. The apparatus for producing a halogen oxygen acid solution according to Item 14, further comprising one or more additional static mixers downstream of the static mixer and upstream of the reaction solution withdrawal means, and further comprising a halogen supply means for supplying halogen to each of the additional static mixers. Item 16. The apparatus for producing a halogen oxygen acid solution according to Item 14 or 15, further comprising a heat exchanger for exchanging heat in the reaction solution. [Effects of the Invention]

[0010] The present invention provides a method and apparatus for industrially advantageously producing a halogen oxygen acid solution, which increases production efficiency per reaction volume more efficiently than a batch reaction, thereby increasing production volume. [Brief explanation of the drawings]

[0011]

Figure 1

[0012] <Method of producing halogen oxygen acid> (reaction format) Next, the greatest feature of this embodiment is that a halogen is continuously supplied to a static mixer in a flow path through which an organic alkaline solution flows, and the resulting halogen oxyacid solution is continuously withdrawn. Hereinafter, the resulting halogen oxyacid solution may be referred to as a "reaction liquid" or a "mixed liquid." By installing a static mixer in the flow path, the mixing of the organic alkaline solution and the halogen can increase the production volume per unit volume while reducing side reactions. Furthermore, it is a preferred embodiment to install a heat exchanger in the flow path to remove the heat of reaction and heat of absorption generated in the reaction between the organic alkaline solution and the halogen, thereby removing heat from the reaction liquid. In conventional batch-type reaction methods, the process involves adding halogen to an organic alkaline solution placed in a reactor, so the pH of the reaction solution tends to be high at the beginning of the reaction, and the liquid residence time in the reactor is long, making it easy for halogen oxyacids to decompose at high pH levels. Furthermore, in halogen oxyacids generated in the high pH range, decomposition products are generated by the decomposition of the halogen oxyacid, creating stability issues. On the other hand, by reacting the organic alkaline solution with the halogen in a flow path and continuously extracting the reaction solution, it is possible to shorten the liquid residence time and suppress the decomposition of halogen oxyacids. Additionally, it is possible to increase the production volume per volume. do. The pH of the reaction solution of the organic alkali and halogen supplied to the flow channel is preferably greater than 10.5 and less than 14.1, and more preferably 12.0 or greater and 13.8 or less.

[0013] For this reason, it is preferable to quickly homogenize the reaction solution in the flow path. In the present invention, as a method for homogenizing the reaction solution, an organic alkaline solution and a halogen are mixed in a static mixer. It is preferable to control the supply ratio of the raw materials so that the pH of the mixed solution (halogen oxyacid solution) that has passed through the static mixer is preferably greater than 10.5 and less than 14.1, more preferably 12.0 or greater and 13.8 or less. Note that, unless otherwise specified, the pH in the present invention is the value at 25°C. Furthermore, the pH is the value of the mixed solution immediately after passing through the static mixer, or in other words, the value at the outlet of the static mixer. Any static mixer can be used without particular limitation as long as it adjusts the pH of the mixed solution after passing through the static mixer to preferably greater than 10.5 and less than 14.1, more preferably 12.0 or greater and 13.8 or less. When chlorine gas, chlorine ions, or an oxoacid of chlorine is used as the halogen, it is important to use a static mixer to rapidly mix the organic alkaline solution and the halogen in order to increase the chlorine yield. In the production method of the present invention, the pH of the mixture that has passed through the static mixer refers to the pH of the reaction mixture withdrawn from the last static mixer that the mixture has passed through. In cases where the reaction mixture is mixed in multiple different static mixers or where the reaction mixture is circulated and mixed again in a static mixer that it has passed through once, the pH refers to the pH of the reaction mixture that has been mixed in the final static mixer. The chlorine yield was calculated from the ratio (%) of the number of moles of hypochlorite ions generated to the number of moles of chlorine molecules supplied. If all of the added chlorine reacts (no decomposition occurs), the chlorine yield is 100%. If hypochlorite ions decompose during the reaction, the chlorine yield decreases.

[0014] As the static mixer, any known commercially available mixer can be used without any limitation. Specifically, a Y-shaped tube, an ejector, a plate-shaped or cup-shaped collision type static mixer, and a Keni mixer as shown in the mixer type in the revised 6th edition of the Chemical Engineering Handbook can be used. cs (trademark) Type: Etoflo HV (trademark) Type, Sulzer SMXL (trademark) Type, Sulze r SMX (trademark) Type, Sulzer SMV (trademark) Type, T o ray Hi-mixer (trademark) Type, Bran and Lubbe N-form (trademark) Type, Komax (trademark) Mold, Lightnin In-liner (trademark) Type: Ross ISG (trademark) Type, Prematechnik PMR (trademark) Type of static Examples of suitable mixers include a stop mixer. In order to improve the mixing performance of the static mixer, it is a preferred embodiment to install the static mixer in multiple stages, which allows the reaction to be carried out in multiple stages. When static mixers are installed in two stages, for example, an embodiment can be such that the reaction liquid that has passed through the first static mixer is supplied to the second static mixer, and at the same time, halogen is also supplied to the second static mixer. The halogen supplied to the second static mixer may have the same composition as the halogen supplied to the first static mixer, or may have a different composition. The number of static mixers may not be limited to two, but may be two or more, such as three, four, or five. There is no particular upper limit, but an example would be 10 or less. When the nth static mixer is installed, a pipe is installed downstream of the (n-1)th static mixer. An example of such an embodiment is one in which the pipe is connected to an n-th static mixer, and an n-th halogen supply means is provided so as to be connected to the n-th static mixer (n is, for example, 2, 3, 4, 5, 6, 7, 8, 9, or 10). When the halogen to be supplied differs in composition from the halogen to be supplied to the first static mixer, the conditions are preferably within the range of the conditions applied to the halogen to be supplied to the first static mixer.Furthermore, the supply amount and supply flow rate (velocity) of the halogen are also preferably within the range of the conditions applied to the halogen to be supplied to the first static mixer.

[0015] In the production method of the present invention, the halogen oxygen acid solution, which is the reaction liquid, may be circulated during the production process. Circulating the reaction liquid during the production process means that the reaction liquid flowing out of the initial static mixer is supplied again to the static mixer through which it has passed once, rather than to the reaction liquid outlet pipe. By supplying the reaction liquid to the static mixer through which it has passed once and supplying new halogen, the unreacted organic alkali remaining in the reaction liquid can be reacted with the halogen. On the other hand, in the production method of the present invention, it is also possible to withdraw the halogen-oxygen acid solution, which is the reaction liquid, without circulating it during the production process. This means that the reaction liquid obtained after passing through one or more static mixers is withdrawn without being fed back to the static mixers that it has passed through once. The above-mentioned "production process" refers to the process from the initial supply of the organic alkali solution and halogen to the withdrawal of the resulting reaction liquid, and may also include any of the processes described below.

[0016] When the halogen is a gas, it disperses in the solution as fine bubbles, accelerating the dissolution of the gas in the downstream piping, and therefore a static mixer with good gas-liquid dispersion performance is preferred. Examples of such static mixers include ejectors, plate-shaped or cup-shaped collision-type static mixers, Kenics-type and Sulzer-type static mixers. Furthermore, it is preferable to select a static mixer that will easily produce a bubbly flow after mixing, and an ejector, a plate-shaped or cup-shaped collision-type static mixer, or a Sulzer-type static mixer is particularly preferable.

[0017] (organic alkaline solution) The organic alkali solution supplied to the static mixer may be either an aqueous solution in which the organic alkali is dissolved in water or a solution in which the organic alkali is dissolved in a nonaqueous solvent. The organic alkali solution can be obtained by dissolving the organic alkali in water or a nonaqueous solvent, or by diluting a commercially available organic alkali solution to the desired concentration. Examples of nonaqueous solvents include known organic solvents capable of dissolving organic alkalis. Specific examples include alcohols and glycols, with methanol and propylene glycol being particularly preferred. Among these solvents, water is preferred because it is industrially readily available and can produce a high-purity organic alkali solution. The concentration of the organic alkali solution is not particularly limited, but if the organic alkali concentration becomes high, salts will precipitate and become solids. Therefore, the concentration of the organic alkali solution is preferably 0.01% by mass or more and 30% by mass or less, more preferably 0.05% by mass or more and 27.5% by mass or less, and even more preferably 0.1% by mass or more and 25% by mass or less.

[0018] The prepared organic alkaline solution typically contains carbon dioxide derived from the atmosphere. Carbon dioxide exists in the solution as carbonate ions or bicarbonate ions. The carbon dioxide concentration is not particularly limited, but is preferably 0.001 ppm to 500 ppm (by mass) calculated as carbonate ions, more preferably 0.005 ppm to 300 ppm, and even more preferably 0.01 ppm to 100 ppm. By ensuring that the carbon dioxide concentration in the organic alkaline solution is 0.001 ppm to 500 ppm, changes in the pH of the resulting halogen-oxygen acid solution can be suppressed. As a result, the storage stability of the halogen-oxygen acid solution can be improved. Commercially available organic alkaline solutions with such carbon dioxide concentrations can be used.

[0019] When preparing a quaternary alkylammonium hydroxide solution as the organic alkaline solution to be prepared, if ammonia and / or amines are present in the solution, the hypochlorite ions generated in the reaction process will be decomposed.Generally, commercially available quaternary alkylammonium hydroxide solutions contain amines.When using such a quaternary alkylammonium hydroxide solution, the hypochlorite ions generated in the reaction process will react with amines, causing a decrease in the concentration of hypochlorite ions.Furthermore, if the amines are tertiary amines, In this case, secondary amines, primary amines, and ammonia produced by the reaction with hypochlorite ions also react with hypochlorite ions, causing a significant decrease in the concentration of hypochlorite ions. In particular, tertiary amines react rapidly with hypochlorite ions, and even a trace amount of them can cause a significant decrease in the concentration of hypochlorite ions. For example, it is known that commercially available tetramethylammonium hydroxide solutions contain tens to hundreds of ppm by mass of trimethylamine. Trimethylamine reacts with hypochlorite ions to produce dimethylamine and monomethylamine, so using such tetramethylammonium hydroxide solutions reduces the concentration of hypochlorite ions, making them unsuitable. Therefore, it is preferable that the ammonia and / or amines contained in the quaternary alkylammonium hydroxide solution be low, specifically, 20 ppm by mass or less. A concentration of 20 ppm by mass or less can minimize the decrease in hypochlorite ion concentration occurring during the reaction process, thereby improving the stability of the resulting quaternary alkylammonium hypochlorite solution. In the present invention, the amine concentration refers to the total concentration of tertiary amines, secondary amines, primary amines, and ammonia contained in the solution. Suitable examples of quaternary alkylammonium hydroxide solutions with reduced amine content include tetramethylammonium hydroxide solutions for semiconductor applications, tetramethylammonium hydroxide solutions from which ammonia and / or amines have been removed by methods such as distillation or ion exchange, and tetramethylammonium hydroxide solutions that have been subjected to reduced pressure treatment or degassing with an inert gas. Among these, tetramethylammonium hydroxide solutions for semiconductor applications are more preferred from the viewpoints of easy availability of industrial products and low amine concentrations. Furthermore, tetramethylammonium hydroxide solutions for semiconductor applications that have been subjected to distillation, ion exchange, reduced pressure treatment, and degassing are most preferred due to their low amine concentration.

[0020] The solvent for preparing the organic alkaline solution may be an aqueous solution containing only water as the solvent, or a non-aqueous solution prepared by mixing an organic solvent. The solvent may be appropriately changed depending on the application of the solution containing halogen oxygen acid and the object to be cleaned. For example, when the object to be cleaned is ruthenium, the solvent can be prepared as an organic alkaline aqueous solution, since sufficient cleaning can be achieved with water alone.

[0021] In this embodiment, the organic alkaline solution is preferably an aqueous solution of onium hydroxide, such as ammonium hydroxide, phosphonium hydroxide, sulfonium hydroxide, or iminium hydroxide or diazonium hydroxide containing multiple bonds. Among these, an aqueous solution of ammonium hydroxide, which contains many relatively stable compounds, is more preferable. The quaternary alkylammonium hydroxide solution is preferably a solution of quaternary alkylammonium hydroxide having an alkyl group with 1 to 10 carbon atoms, more preferably a solution of quaternary alkylammonium hydroxide having an alkyl group with 1 to 5 carbon atoms. Specific examples of quaternary alkylammonium hydroxide include tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrabutylammonium hydroxide, and choline. These quaternary alkylammonium hydroxides may be used alone or in combination of two or more. Furthermore, the four alkyl groups contained in the quaternary alkylammonium hydroxide may have the same or different carbon atoms.

[0022] The various conditions in the above and following explanations, such as the concentration range of the organic alkali in the organic alkali solution supplied to the static mixer, its pH range, and the concentration range of the organic alkali in the reaction liquid, its pH range, etc., are applicable to any of the above specific examples of organic alkali.

[0023] (A process for mixing an organic alkaline solution and a halogen in a static mixer to produce a reaction solution containing a halogen oxygen acid) In a process for producing a reaction solution containing a halogen oxyacid by mixing an organic alkaline solution with a halogen and reacting them in a static mixer, the pH of the reaction solution containing the halogen oxyacid produced by mixing in the static mixer tends to decrease after passing through the static mixer. In consideration of the conditions for the filtration step described below and the solubility of the organic alkali, in this embodiment, the lower limit of the pH of the organic alkaline solution used as the raw material is greater than 10.5, preferably 11.0 or greater, more preferably 11.5 or greater, and particularly preferably greater than 12.0. The upper limit of the pH of the organic alkaline solution is determined by the concentration of the organic alkali, but is preferably 14.5 or less.

[0024] The organic alkaline solution used in this embodiment may also contain metals, specifically sodium, potassium, aluminum, magnesium, iron, nickel, copper, silver, cadmium, and lead. However, it is preferable that the content of each of these metals is 0.01 ppb or more and 20 ppb or less. Of course, the metal content of the organic alkaline solution used may be less than 0.01 ppb, but it is difficult to obtain such an organic alkaline solution. Therefore, by using an organic alkaline solution whose metal content satisfies the above range, the solution itself is easily available, and the metal impurities can be easily removed or reduced by filtration during and after the production of the reaction solution containing the halogen-oxygen acid. While the reason why metal impurities can be removed or reduced by the filtration process is unclear, it is believed that the presence of a certain amount of metal impurities results in the formation of impurity particles of a certain size, rather than colloidal impurities that are difficult to remove by filtration, making them removable by filtration. Therefore, the organic alkaline solution used in this embodiment can be suitably used even if it is not an ultra-high-purity organic alkaline solution, because the pH can be lowered to remove or reduce solid metal impurities in the filtration process. To further enhance this effect, particularly to further remove or reduce alkaline ionic impurities, the metal contents of sodium, potassium, aluminum, magnesium, iron, nickel, copper, silver, cadmium, and lead contained in the organic alkaline solution are preferably 0.01 ppb or more and 5 ppb or less, and even more preferably 0.01 ppb or more and 2 ppb or less.

[0025] Commercially available organic alkaline solutions can be used as the organic alkaline solutions described above. Among these, organic alkaline solutions that have been highly purified by electrolysis and / or contact with ion exchange resins or the like and are used as photoresist developers for semiconductor devices are particularly suitable. These commercially available solutions can also be diluted with a solvent that does not contain metal impurities, such as ultrapure water, before use. The supply rate of the organic alkaline solution supplied to the static mixer varies depending on the concentration of the organic alkaline solution, but the flow rate can be, for example, from 0.01 m / s to 10 m / s, more preferably from 0.2 m / s to 3 m / s.

[0026] (Reaction that occurs when an organic alkaline solution comes into contact with a halogen) For example, when a quaternary alkylammonium hydroxide is used as the organic alkali, by contacting and reacting the solution with a halogen, the hydroxide ions of the quaternary alkylammonium hydroxide are substituted with hypohalite ions generated by the halogen, and a quaternary alkylammonium hypohalite solution is produced. In this embodiment, the halogen used is not particularly limited as long as it is a halogen element or a halogen source such as an oxoacid of a halogen element, and commercially available products can be used. Specific examples of halogen include chlorine, bromine, hypochlorous acid, hypobromous acid, chlorous acid, bromous acid, chloric acid, bromic acid, iodine, hypoiodous acid, iodous acid, and iodic acid. When chlorine or bromine is used, their gas, chlorine water, bromine water, etc. can be used. Among these, chlorine gas is preferably used. Among these, high purity materials such as those used for etching semiconductor materials and as raw materials for semiconductor materials can be used. Among the high purity materials, those with a low water content are particularly preferred. It is preferable to use chlorine gas having a moisture content of 10 ppm by volume or less (by mass). The reason for this is unclear, but the following is thought to be the case. For example, when chlorine gas is used to produce a quaternary alkylammonium hypochlorite solution, the chlorine gas is usually transported via piping. Therefore, if a large amount of water is present, hydrogen chloride is generated, corroding metal components such as piping and flow meters, and it is thought that corroded metal impurities are easily introduced into the system along with the chlorine gas. Therefore, it is preferable to use chlorine gas having a moisture content of 10 ppm by volume or less. Naturally, commercially available chlorine gas can be used as is, or the moisture content of the chlorine gas can be reduced by contacting it with a desiccant or the like just before it is introduced into the reaction system. The lower limit of the moisture content of chlorine gas is not particularly limited, but considering industrially available chlorine gas, it is 0.1 ppm by volume. Furthermore, when using chlorine gas, it is a preferred embodiment to install a device called a purifier midway through the piping to remove gaseous pollutants (metals, etc.).

[0027] In this embodiment, when chlorine gas is used as the halogen, the concentration of carbon dioxide contained in the chlorine gas is not particularly limited, but is preferably 0.001 to 80 ppm by volume, more preferably 0.005 to 50 ppm by volume, and even more preferably 0.01 to 2 ppm by volume. If the carbon dioxide concentration contained in the chlorine gas is in the range of 0.001 to 80 ppm by volume, the pH change of the resulting quaternary alkylammonium hypochlorite solution can be suppressed. As a result, the storage stability of the quaternary alkylammonium hypochlorite solution can be improved. Chlorine gas with such a carbon dioxide concentration can be commercially available. In this embodiment, the amount of halogen used (molar number of halogen used) is not particularly limited and may be appropriately determined taking into consideration the concentration and total amount of the organic alkali used, the concentration and total amount of the resulting halogen oxygen acid, and other factors. For example, when hypochlorous acid, hypobromous acid, chlorous acid, bromous acid, chloric acid, or bromic acid is used as the halogen and a quaternary alkylammonium hydroxide solution is used as the organic alkali solution, the amount of halogen used is preferably 8 μmol to 3.4 mol per liter of the quaternary alkylammonium hydroxide solution. Using halogen within this range allows for stable production of the halogen oxygen acid. Although an amount exceeding 3.4 mol per liter of the quaternary alkylammonium hydroxide solution can be used, the pH of the resulting halogen oxygen acid decreases and the halogen oxygen acid tends to decompose. On the other hand, if the amount is less than 8 μmol, the halogen oxygen acid concentration will be low, resulting in poor production efficiency. Therefore, in consideration of industrial production, the amount of halogen is preferably 8 μmol to 3.4 mol, more preferably 80 μmol to 3.2 mol, and even more preferably 800 μmol to 3.0 mol per liter of the quaternary alkylammonium hydroxide solution. However, the amount of halogen used can also be determined based on the pH of the resulting solution, i.e., the pH of the resulting quaternary alkylammonium hypochlorite solution.

[0028] Next, in this embodiment, a method of contacting a quaternary alkyl ammonium hydroxide solution with a halogen gas using a quaternary alkyl ammonium hydroxide solution as an organic alkaline solution and a chlorine gas as a halogen gas will be described as an example of an embodiment of the present invention. In the following description, unless otherwise specified, it may be assumed that a quaternary alkyl ammonium hydroxide solution is used as an organic alkaline solution and a chlorine gas is used as a halogen gas, but this is merely an example. The method for supplying chlorine gas to the flow path can be a known method. Since the chlorine gas is mixed by a static mixer installed after the chlorine gas is supplied, the method can be appropriately determined so as not to hinder the flow of the organic alkaline solution.

[0029] In addition, in order to avoid the inclusion of carbon dioxide in the reaction system, it is preferable that the reaction in the production apparatus according to the embodiment of the present invention is carried out in a closed system. In this embodiment, the amount of halogen used (total amount of chlorine gas used) is not particularly limited. In the case of chlorine gas, however, the amount of quaternary alkyl hydroxide is The amount of chlorine gas used per liter of quaternary alkylammonium hydroxide solution is preferably 0.1 mL to 37,000 mL at 0°C and 1 atm, and may be 10 mL to 1,000 mL. Using chlorine gas within this range suppresses rapid pH changes in the reaction system and facilitates the removal and reduction of metal impurities during the filtration process. Although the amount of chlorine gas used per liter of quaternary alkylammonium hydroxide solution may exceed 37,000 mL at 0°C and 1 atm, this results in a significant decrease and fluctuation in the pH of the quaternary alkylammonium hydroxide solution, and unreacted chlorine gas tends to remain. On the other hand, using less than 0.1 mL tends to result in insufficient hypochlorite ions being generated. Therefore, considering industrial production, the amount of chlorine gas used per liter of quaternary alkylammonium hydroxide solution is preferably 0.1 mL to 37,000 mL at 0°C and 1 atm. However, the amount of chlorine gas used can also be determined based on the pH of the resulting solution, i.e., the pH of the resulting quaternary alkylammonium hypochlorite solution. Furthermore, it is preferable to supply chlorine gas into the static mixer at the following rate: The supply flow rate (rate) of chlorine gas is preferably 0.45 mmol / min or more and 1380 mmol / min or less per liter of quaternary alkylammonium hydroxide solution, in order to prevent a sudden drop in pH and reduce the amount of chlorine gas not involved in the reaction. By satisfying this range, sufficient reactivity is achieved, and a quaternary alkylammonium hypochlorite solution can be produced without a sudden drop or fluctuation in pH. To maximize this effect, the supply rate of chlorine gas into the reaction system is more preferably 0.45 mmol / min or more and 1200 mmol / min or less, and even more preferably 0.90 mmol / min or more and 1000 mmol / min or less.

[0030] In this embodiment, the organic alkali may further contain a bromine salt. In the organic alkali containing the bromine salt, the halogen reacts with the organic alkali to produce, for example, a hypohalous acid and a halide. Furthermore, the hypohalous acid reacts with bromide ions, hypobromite ions, bromite ions, bromate ions, or perbromate ions contained in the bromine salt, or with bromine molecules generated from the bromine salt, to produce a new halogen oxyacid. The reaction between the hypohalous acid and the ions, or between the hypohalous acid and bromine molecules, may be any reaction that generates a new halogen oxyacid by adding a halogen to a solution containing a bromine salt and an organic alkali. For example, the reaction may be a redox reaction, a disproportionation reaction, or a radical reaction.

[0031] In the present invention, bromine salts refer to salts containing bromine atoms, such as hypobromite, bromite, bromate, perbromate, and bromide. Examples of bromides include hydrogen bromide, lithium bromide, sodium bromide, potassium bromide, rubidium bromide, cesium bromide, ammonium bromide, and onium bromide. The onium bromide referred to here is a compound formed from an onium ion and a bromide ion. The onium ion refers to cations such as imidazolium ion, pyrrolidinium ion, pyridinium ion, piperidinium ion, ammonium ion, phosphonium ion, fluoronium ion, chloronium ion, bromonium ion, iodonium ion, oxonium ion, sulfonium ion, selenonium ion, telluronium ion, arsonium ion, stibonium ion, and bismuthonium ion. Compounds that generate hypobromous acid or hypobromite ions in the treatment solution can also be used as bromine-containing compounds. Examples of such compounds include, but are not limited to, bromohydantoins, bromoisocyanuric acids, bromosulfamic acids, bromochloramines, etc. More specific examples of compounds include 1-bromo-3-chloro-5,5-dimethylhydantoin, 1,3-dibromo-5,5-dimethylhydantoin, tribromoisocyanuric acid, etc.

[0032] To be more specific, the bromine salt is tetramethylammonium bromide, and the organic ammonium salt is tetramethylammonium bromide. An example of a reaction between a bromide, an organic alkali, and a halogen when the alkali is tetramethylammonium hydroxide and the halogen is chlorine is as follows: When chlorine gas is bubbled into an aqueous solution containing tetramethylammonium bromide and tetramethylammonium hydroxide, the tetramethylammonium hydroxide reacts with chlorine to produce hypochlorous acid and chloride. Some of the hypochlorous acid reacts with bromide ions contained in the tetramethylammonium bromide in the solution, directly oxidizing the bromide ions to produce hypobromous acid. As a result, an aqueous solution containing hypochlorous acid, hypobromous acid, chloride (tetramethylammonium chloride), unreacted tetramethylammonium bromide, and tetramethylammonium hydroxide is obtained. That is, a halogen oxygen acid containing two halogen oxygen acids (hypochlorous acid and hypobromous acid) is obtained. Furthermore, when the number of moles of chlorine molecules is smaller than the number of moles of tetramethylammonium bromide in a solution containing a bromide and an organic alkali, an aqueous solution containing hypobromous acid, chloride (tetramethylammonium chloride), unreacted tetramethylammonium bromide, and tetramethylammonium hydroxide is obtained. The concentration of the bromine salt that may be added to the organic alkali is not particularly limited, and may be, for example, in the range of 0.1 μmol / L to 10 mol / L. The solution containing multiple halogen acids thus obtained can be suitably used in semiconductor manufacturing.

[0033] (Reaction temperature) The reaction temperature range in the production method of this embodiment is preferably -35°C to 45°C, more preferably -15°C to 40°C, and even more preferably -5°C to 35°C. If the reaction temperature is within the above range, the quaternary alkylammonium hydroxide solution and chlorine react sufficiently, allowing the quaternary alkylammonium hypochlorite solution to be produced with high production efficiency. If the reaction temperature is below -35°C, the quaternary alkylammonium hydroxide solution begins to solidify, and the reaction with chlorine becomes insufficient. On the other hand, if the reaction temperature exceeds 45°C, the hypochlorite ions produced in the quaternary alkylammonium hydroxide solution decompose due to heat. Particularly when the pH during the reaction is 13.8 or higher, the decomposition of hypochlorite ions becomes more pronounced as the reaction temperature increases. The production efficiency of quaternary alkylammonium hypochlorite can be evaluated by the ratio of the number of moles of hypochlorite ions produced to the number of moles of chlorine molecules supplied as raw material. As described above, according to the manufacturing method of this embodiment, it is possible to manufacture a quaternary alkyl ammonium hypochlorite solution that has excellent storage stability, for example, can maintain sufficient cleaning and removing power even after 10 days have passed since its manufacture.As is clear from this, the quaternary alkyl ammonium hypochlorite solution obtained by the manufacturing method of this embodiment has excellent storage stability and can be suitably used in the manufacturing process of semiconductor devices.

[0034] (Materials for the inner surfaces of static mixers and piping) In this embodiment, the quaternary alkylammonium hydroxide solution is contacted with the chlorine gas in a static mixer to produce a quaternary alkylammonium hypochlorite solution. At this time, a predetermined amount of the quaternary alkylammonium hydroxide solution is first introduced into a reactor, and then chlorine gas is introduced so as to contact the quaternary alkylammonium hydroxide solution. In this embodiment, the surfaces inside the static mixer and inside the piping of the manufacturing equipment that come into contact with the quaternary alkylammonium hydroxide solution are made of an organic polymer material, thereby further reducing the inclusion of impurities containing the above metals (metal impurities). In addition, it is preferable that the reaction be carried out in a light-shielded environment, and specifically, it is preferable that the static mixer be one in which the interior is light-shielded. The chlorine gas present in the static mixer may be excited by light and generate chlorine radicals. When chlorine radicals are generated, they may affect the quaternary alkyl ammonium hydroxide present in the static mixer and the quaternary alkyl ammonium hypochlorite produced by the reaction, causing decomposition. Furthermore, the quaternary alkyl ammonium hypochlorite itself may decompose due to light, so it is preferable to shield the static mixer and associated piping from light. In this embodiment, when an organic solvent is used as the solvent, it is preferable that the static mixer and piping have an explosion-proof structure. Therefore, in order to simplify the device configuration, it is preferable that the quaternary alkylammonium hydroxide solution uses water as the solvent. In this embodiment, the organic polymer material used for the inner surface of the static mixer and piping may be vinyl chloride resin (soft or hard vinyl chloride resin), nylon resin, silicone resin, polyolefin resin (polyethylene, polypropylene), fluororesin, etc. Among these, fluororesin is preferred in view of ease of molding, solvent resistance, low elution of impurities, etc. The fluororesin is not particularly limited as long as it is a resin (polymer) containing fluorine atoms, and known fluororesins can be used. Examples include polytetrafluoroethylene, polychlorotrifluoroethylene, polyvinylidene fluoride, tetrafluoroethylene-hexafluoropropylene copolymer, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, tetrafluoroethylene-ethylene copolymer, chlorotrifluoroethylene-ethylene copolymer, and cyclized polymer of perfluoro(butenyl vinyl ether). Among them, considering the availability of the reactor itself, productivity, etc., it is preferable to use tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer.

[0035] In this embodiment, methods for forming the inner surfaces of the static mixer and piping from an organic polymer material include a method for forming the entire static mixer and piping from an organic polymer material, and a method for covering only the inner surfaces of a static mixer or piping made of glass or stainless steel with an organic polymer material. Furthermore, the organic polymer material can be washed before use to prevent the elution of metal components from the material. Specifically, it is preferable to thoroughly wash the material with an acid such as high-purity nitric acid or hydrochloric acid (for example, by immersing it in a solution with an acid concentration of 1 mol / L for 12 hours), and then further wash it with ultrapure water or the like. Furthermore, to ensure a stable reaction, it is preferable to wash the inner surfaces of static mixers and piping made of the organic polymer material by the above-mentioned method before reacting the quaternary alkylammonium hydroxide solution with chlorine gas.

[0036] In this embodiment, as long as the surfaces of the static mixer and the piping that come into contact with the quaternary alkylammonium hydroxide solution are made of an organic polymer material, the other parts may be made of glass, stainless steel, or passivated stainless steel. However, since the effect is small, it is preferable, although not essential, to make them of the same organic polymer material. In this embodiment, the quaternary alkylammonium hydroxide solution may be contacted with chlorine gas in a static mixer, but it is preferable to introduce chlorine gas into the quaternary alkylammonium hydroxide solution. The reaction temperature range is not particularly limited, but it is preferably the same as the reaction temperature described above. Furthermore, the presence of carbon dioxide in the reaction system tends to lower the pH of the resulting quaternary alkylammonium hypochlorite solution. Therefore, considering stable production, it is preferable to prevent carbon dioxide from being present in the reaction system. Specifically, it is preferable to use a quaternary alkylammonium hydroxide solution, chlorine gas, or the like, with a reduced amount of carbon dioxide. Furthermore, it is preferable to carry out the reaction in the presence of an inert gas with a reduced amount of carbon dioxide (e.g., in the presence of nitrogen gas). By carrying out the reaction under these conditions, a decrease in the pH of the resulting quaternary alkylammonium hypochlorite solution can be suppressed, thereby improving storage stability.

[0037] In addition, the amine concentration in the liquid phase in the reaction step is preferably kept at 100 mass ppm or less. As described above in the section (organic alkaline solution), if the quaternary alkylammonium hydroxide solution contains amine, the concentration of hypochlorite ions generated in the reaction step will decrease. In addition, the hypochlorite ions generated by the reaction react with quaternary alkylammonium ions at high pH to produce tertiary amines, which are contained in the liquid phase as the reaction progresses. The amine concentration increases as the reaction proceeds. That is, the amine concentration contained in the liquid phase in the reaction step tends to be higher than the amine concentration before the reaction step. However, by keeping the amine concentration contained in the liquid phase in the reaction step at 100 mass ppm or less, the decrease in the concentration of hypochlorite ions can be reduced and storage stability can be improved.

[0038] <Filtration process> In the manufacturing method according to an embodiment of the present invention, when the quaternary alkylammonium hydroxide solution comes into contact with chlorine gas to produce a quaternary alkylammonium hypochlorite solution, the pH of the solution in the reaction system decreases. During this process, solid matter containing metal impurities may precipitate. To remove or reduce this, a preferred embodiment preferably further includes a filtration step. That is, it is preferable to filter the quaternary alkylammonium hypochlorite solution obtained during the reaction or by supplying chlorine gas up to a predetermined concentration. The filtration step may be performed after the storage step described below or after dilution. In the filtration step, the metal components filtered out may vary depending on the pH of the quaternary alkylammonium hypochlorite solution. Specifically, when the pH of a quaternary alkylammonium hypochlorite solution is adjusted to 13.5 or less, preferably when the pH of the solution is greater than 12.5 but less than 13.5, hydroxides of magnesium, iron, cadmium, etc., and oxides of nickel and silver solidify. These impurities can be removed or reduced by performing a filtration process. Furthermore, when the pH of a quaternary alkylammonium hypochlorite solution is adjusted to 12.5 or less, preferably when the pH of the solution is greater than 9.0 but less than 12.5, copper and lead oxides solidify in addition to the above impurities. These impurities can also be removed or reduced by performing a filtration process. The pH of the solution may vary depending on the temperature. The above pH values ​​are based on values ​​at 25°C. The actual liquid temperature during the filtration process is not limited to 25°C, but is preferably between 20°C and 28°C, and more preferably between 23°C and 25°C. These solid metal impurities are generated even when the purity of the raw quaternary alkylammonium hydroxide solution and chlorine gas is increased. In particular, solid matter may be generated when the inner surface of a static mixer is made of an organic polymer material. The reason for this is unclear, but it is presumed that metal impurities enter the reaction system from somewhere inside the reactor due to the use of chlorine gas, a highly corrosive gas.

[0039] The filtration process should be performed at a pH that solidifies the metals targeted for removal or reduction. Therefore, it can be performed once or multiple times at each pH. In this case, multiple filters with different pore sizes are prepared for each pH, ​​and filtration is performed in order of pore size, starting with the largest filter, to improve filtration efficiency. Specifically, coarse particles can be removed in the first stage and fine particles in the second stage. Note that solids containing metal components, such as simple metal impurities, metal oxides, metal hydroxides, and / or colloidal substances, with a particle size of 1 μm to 100 μm, may be referred to simply as "coarse particles" below. Meanwhile, particles with a size of 0.01 μm to 1 μm, may be referred to simply as "fine particles" below. The particle size of solids refers to the equivalent circle diameter measured by laser diffraction. The filtration step is not particularly limited, and can be carried out using a known filtration device or filter. However, in order to prevent the increase of unnecessary metal components, it is preferable that the surface of the filtration device that may come into contact with the quaternary alkylammonium hypochlorite solution is made of an organic polymer material. The organic polymer can be the same as the one exemplified above.

[0040] As a specific filtration filter, it is preferable to use a filtration filter made of an organic polymer material or an inorganic material. For example, filtration filters made of polyolefin (polypropylene, polyethylene, ultra-high molecular weight polyethylene), polysulfone, cellulose acetate, polyimide, polystyrene, the above-mentioned fluorine-based resins, and / or quartz fiber can be mentioned. In addition, the filtration filter has a positively charged membrane and a negatively charged membrane. It is preferable to use a filter in combination with a membrane containing a metal oxide or hydroxide. The reason for this is that many metal oxides and hydroxides are negatively charged in an alkaline atmosphere, and a filter that is positively charged by electrostatic adsorption can effectively remove metal components. Some metal components exist in a cationic state and are positively charged. Therefore, a negatively charged filter can effectively remove ionized metal components by electrostatic adsorption. Furthermore, filters with ion exchange or chelating ability, such as filters containing ion exchange resins or chelating exchange resins, can also be used. Multiple filters of this type may be used in combination.

[0041] The pore size of the filter is not particularly limited, but a filter with a pore size of 1 μm or more or a microfiltration filter can be used to remove coarse particles, while a microfiltration filter with a pore size of 0.01 μm or more but less than 1 μm, an ultrafiltration filter, or a nanofiltration membrane can be used to remove fine particles. The above-mentioned filters can be commercially available. Specifically, polytetrafluoroethylene filters manufactured by Entegris Japan, such as the "Fluoroguard ATX filter (pore size 0.05 μm)," "Quick Change ATE filter (pore size 0.03 μm)," "Torrent ATE filter (pore size 0.02 μm)," "Quick Change ATE filter (pore size 0.03 μm)," and "Fluoroline P-1500 (pore sizes 0.05 μm, 0.1 μm)," can be used.

[0042] The above filtration process can be carried out before adjusting the pH of the quaternary alkylammonium hypochlorite solution to a range suitable for its application. In this case, after performing the filtration process once, the solution can be mixed with chlorine gas again to adjust the quaternary alkylammonium hypochlorite solution to the desired pH. Alternatively, the quaternary alkylammonium hypochlorite solution can be adjusted to the desired pH by mixing with water, an acid such as hydrogen chloride, and / or an alkali such as a quaternary tetramethylammonium hydroxide aqueous solution. On the other hand, if the pH of the produced quaternary alkylammonium hypochlorite solution is suitable for use as a cleaning solution, the solution can be filtered and used as is as a cleaning solution for manufacturing semiconductor devices. By carrying out such a filtering process, it is possible to reduce metal components such as magnesium, iron, nickel, copper, silver, cadmium, and lead.

[0043] <Preservation process> After the manufacturing method according to an embodiment of the present invention, or after the manufacturing method further including the above-mentioned filtration step, a solution containing a halogen oxyacid (hereinafter, a quaternary alkylammonium hypochlorite solution will be described as an example) can be used as is for a specific purpose such as a cleaning solution, but is generally used after a preservation step (including storage and transportation). Quaternary alkylammonium hypochlorite solutions have poor storage stability when used alone, and the addition of a stabilizer has been required. However, stabilizers can cause organic residues, and improvements have been required. However, by further undergoing the preservation step described below, it is possible to provide a quaternary alkylammonium hypochlorite solution with improved storage stability. The method for producing quaternary alkylammonium hypochlorite solution according to one embodiment of the present invention preferably comprises a preservation step of preserving the reaction solution after the above-mentioned steps, and in this preservation step, the pH of the quaternary alkylammonium hypochlorite solution at 25 ° C is preferably adjusted to be 12.0 or more and less than 14.0, more preferably 12.0 or more and 13.8 or less.If a filtration step is included after the above-mentioned production method of the present invention, a preservation step may also be included after the filtration step.

[0044] The concentration of the quaternary alkylammonium hypochlorite solution to be stored is not particularly limited, but considering industrial production, the concentration of hypochlorite ions at a predetermined pH is preferably 0.001% by mass or more and 20% by mass or less, and the concentration of quaternary alkylammonium ions is preferably 0.001% by mass or more and 5% by mass or less. It is preferable that the quaternary alkylammonium hypochlorite solution contains 0% by mass or less of each of the quaternary alkylammonium hypochlorites. Note that the "predetermined pH" refers to a pH of 12.0 or more and less than 14.0 selected as the pH during the storage step. In addition, various additives may be added to the quaternary alkylammonium hypochlorite solution as desired depending on its intended use. For example, additives such as metal chelating agents, complexing agents, metal dissolution promoters, metal corrosion inhibitors, surfactants, acids, and alkalis can be added. Addition of these additives can be expected to promote or inhibit metal dissolution during semiconductor wafer processing, improve surface roughness, increase processing speed, and reduce particle adhesion, making cleaning solutions containing these additives suitable for use in semiconductor wafer processing. In a preferred embodiment, the storage process for the quaternary alkylammonium hypochlorite solution involves storing the quaternary alkylammonium hypochlorite solution within a limited pH range. The storage process is described in detail below.

[0045] Here, "storage" refers to the period from the start of storage of the quaternary alkylammonium hypochlorite solution at a pH of 12.0 to 14.0 at 25 ° C., or in another embodiment, 12.0 to 13.8, until the concentration and / or pH of the quaternary alkylammonium hypochlorite solution is adjusted. Note that if the pH of the solution after adjusting the pH is 12.0 to 14.0, further storage of the solution also corresponds to the storage step of this embodiment. If the pH of the quaternary alkylammonium hypochlorite solution is 12.0 to 14.0 from the beginning, it can be stored as is. If the pH is less than 12.0 or more than 14.0, it can be stored after adjusting the pH to a range of 12.0 to 14.0.

[0046] The pH of the solution may vary depending on the temperature. The pH value at 25°C is used as a guideline. The actual solution temperature for storage is not limited to 25°C. Therefore, the storage conditions are not particularly limited, but it is preferable to store the solution under general storage conditions, i.e., at temperatures between -25°C and 50°C in a known container, a canister, or a plastic storage container. It is more preferable to store the solution in a dark place at temperatures between -20°C and 40°C in a light-shielding storage container, a transport container such as a canister, or a plastic storage container filled with an inert gas. If the storage temperature exceeds the above range, hypochlorite ions may thermally decompose to form oxygen molecules during long-term storage, causing the container to expand and break.

[0047] In a preferred embodiment, the solution is stored as a quaternary alkylammonium hypochlorite solution having a pH of 12.0 to 14.0 at 25°C. Within this pH range, the hypochlorite ion concentration does not decrease, allowing for long-term storage. If the pH is less than 12.0, the disproportionation reaction of hypochlorite ions proceeds, the hypochlorite ions are decomposed, and the oxidizing power of the quaternary alkylammonium hypochlorite solution decreases. On the other hand, if the pH exceeds 14.0, it is presumed that the organic ions, which are cations, decompose. As a result, it is presumed that the disproportionation reaction of hypochlorite ions, which had been inhibited by the bulkiness of the organic ions, resumes, causing the hypochlorite ions to decompose. It is preferable to store the solution as a quaternary alkylammonium hypochlorite solution having a pH of 12.0 to 14.0 at 25°C.

[0048] The reason why the above-mentioned storage method improves storage stability is not clear, but the present inventors speculate as follows. In the quaternary alkylammonium hypochlorite solution, some of the quaternary alkylammonium hypochlorite dissociates into hypochlorite ions and organic ions, but most of the hypochlorite ions and organic ions are ionic bonds, and it is speculated that the three-dimensional bulkiness of the organic ions suppresses the disproportionation reaction of the hypochlorite ions. Therefore, it is thought that the greater the three-dimensional bulkiness of the organic ions, the more the disproportionation reaction is suppressed and the storage stability is improved. If the organic ion is a bulky quaternary alkylammonium ion, for example, a tetramethylammonium ion, it can sufficiently suppress the disproportionation reaction. After the storage step according to this embodiment, the storage period can be 30 days, preferably 60 days, or even more preferably 60 days. Preferably, even after 90 days, the oxidizing power of the quaternary alkyl ammonium hypochlorite solution during storage remains almost unchanged.Therefore, after storage, the quaternary alkyl ammonium hypochlorite solution can be used for various purposes simply by diluting it according to the conditions of use.In addition, the longer the storage period, the more the effect of improving productivity can be expected.

[0049] <Halogen oxygen acid solution manufacturing equipment> Next, an embodiment of an apparatus for producing a halogen oxyacid solution will be described. The above-mentioned production method can be carried out using the production apparatus of this embodiment. As an example of the production apparatus according to this embodiment, a case where a quaternary alkyl ammonium hydroxide solution is used as the organic alkali and chlorine gas is used as the halogen is illustrated. On the other hand, the conditions such as the type, concentration, and supply rate of the organic alkali and halogen supplied as raw materials can be the same as those described in the above-mentioned method for producing a halogen oxyacid. The production apparatus of this embodiment includes a static mixer, an organic alkaline solution supply means and a halogen supply means for supplying the static mixer with an organic alkaline solution, and a reaction liquid withdrawal means for withdrawing the reaction liquid from the static mixer to the outside. The organic alkaline solution and the halogen are continuously supplied to the static mixer by the organic alkaline solution supply means and the halogen supply means, respectively, and mixed to produce a solution containing a halogen oxyacid as the reaction liquid, and the reaction liquid is continuously withdrawn by the reaction liquid withdrawal means.

[0050] FIG. 1 shows a schematic diagram of a production apparatus. In FIG. 1, a quaternary alkylammonium hydroxide solution supply pipe 1 is provided as an organic alkali supply means, a chlorine gas supply pipe 2 is provided as the halogen supply means, and immediately thereafter a static mixer 3 and a reaction solution discharge pipe 5 are provided. The quaternary alkylammonium hydroxide solution and chlorine gas are mixed using the static mixer 3. The production apparatus according to an embodiment of the present invention may also include a heat exchanger 4 for removing reaction heat and the like. The heat exchanger 4 may be disposed downstream of the static mixer 3, but may be disposed anywhere as long as it can remove reaction heat. The quaternary alkylammonium hydroxide solution and chlorine gas are both continuously supplied, and the reaction liquid produced is continuously withdrawn from reaction liquid withdrawal pipe 5.

[0051] The static mixer provided in the production apparatus of the present invention may be any of those exemplified in the description of the production method above. Among them, preferred examples include an ejector, an impingement type static mixer, and a Sulzer type static mixer.

[0052] The production apparatus of the present invention may further include one or more additional static mixers downstream of the static mixer (first static mixer) and upstream of the reaction liquid withdrawal means, and may further include a halogen supply means for supplying a halogen to each of the additional static mixers. In the production apparatus of the present invention, when two or more static mixers are provided, an embodiment can be mentioned in which a pipe is provided downstream of a first static mixer, the pipe is connected to a second static mixer, and a halogen supply means is provided so as to be connected to the second static mixer. 1, an embodiment in which the reaction liquid withdrawal pipe 5 is connected to a second static mixer (not shown), and a second halogen supply means (not shown) is separately connected to the second static mixer can be exemplified. Similarly, when an nth static mixer is installed, an embodiment in which a pipe is provided downstream of the (n-1)th static mixer, and the pipe is connected to the nth static mixer, and an nth halogen supply means is provided so as to be connected to the nth static mixer (n is, for example, 2, 3, 4, 5, 6, 7, 8, 9, or 10). For example, when the production apparatus of the present invention further includes a third static mixer, an embodiment can be mentioned in which a pipe is provided downstream of the second static mixer, the pipe is connected to the third static mixer, and a third halogen supply means is provided so as to be connected to the third static mixer. When the production apparatus of the present invention is equipped with a plurality of static mixers, the reaction liquid does not necessarily have to flow through all of the static mixers by devising a flow path or providing valves. When the production apparatus of the present invention is equipped with multiple static mixers, new halogen can be contacted with the reaction solution that has passed through the first static mixer in multiple stages. This allows the unreacted organic alkali contained in the reaction solution to react with the new halogen, and the reaction to obtain a halogen oxyacid can be carried out in multiple stages. Examples of the production apparatus according to the present invention that is equipped with multiple static mixers include two, three, four, or five or more. There is no particular upper limit, but an example is 10 or less.

[0053] The production apparatus of the present invention, whether equipped with one static mixer or two or more, may be configured so that the reaction liquid circulates within the production apparatus by adjusting the flow path of the reaction liquid. To circulate the reaction liquid within the production apparatus, the reaction liquid outlet pipe may be branched, or the pipes between multiple static mixers may be branched, and the branched pipes may be adjusted so that they connect to a static mixer through which the reaction liquid has passed once. In this configuration, a single production apparatus can react unreacted organic alkali contained in the reaction liquid with new halogen, allowing the reaction to occur in multiple stages. On the other hand, if the production apparatus of the present invention does not have the above-mentioned configuration, or even if it does, by providing an appropriate valve at the branch point, the reaction liquid can be taken out without circulating within the production apparatus.

[0054] For the inner surface of the static mixer shown in FIG. 1, the conditions explained in the above manufacturing method can be used as they are. The liquid flow rate in the pipe for the quaternary alkylammonium hydroxide solution and the reaction liquid to be supplied is preferably 0.01 m / s or more and 10 m / s or less, more preferably 0.2 m / s or more and 3 m / s or less. The volume of the static mixer is preferably such that the residence time of the supplied quaternary alkylammonium hydroxide solution is 0.1 to 5 minutes, more preferably 0.1 to 1 minute.

[0055] The reaction between the quaternary alkylammonium hydroxide solution and chlorine gas is an exothermic reaction. In the production apparatus according to the embodiment of the present invention, heat can be removed by installing a heat exchanger 4, for example, downstream of the static mixer. The location of the heat exchanger is not limited to downstream of the static mixer. By installing the heat exchanger, the temperature of the reaction liquid can be adjusted to, for example, 23°C or higher and 27°C or lower, preferably 24°C or higher and 26°C or lower. The reaction liquid extracted through the reaction liquid extraction pipe 5 may be sent to a product preparer (not shown). In the product preparer, the concentration and pH of the reaction liquid sent from the static mixer are adjusted. The product preparer is supplied with an organic alkaline solution, for example, one or more of a quaternary alkylammonium hydroxide solution, hydrochloric acid, and water, as needed, to adjust the concentration and pH of the reaction liquid. The product preparer can be configured as a tank with a volume sufficient to supply the reaction liquid as well as one or more of the above-mentioned quaternary alkylammonium hydroxide solution, hydrochloric acid, and water.

[0056] Furthermore, the manufacturing apparatus according to an embodiment of the present invention may be provided with a filtration device upstream or downstream of the product preparation device. The filtration device may be configured to include a reaction liquid transfer pipe, a pump, a filtration filter, and a reaction liquid return pipe. Each component of these filtration devices is preferably made of the organic polymer material described above, since it comes into contact with the reaction liquid containing the quaternary alkylammonium hypochlorite. Furthermore, the filtration filter may be one of those exemplified in the filtration process described above.

[0057] The manufacturing apparatus of this embodiment may further include an organic alkaline solution preparer for preparing the organic alkaline solution to be supplied to the static mixer and the product preparer. An organic alkali solution preparation device is supplied with an organic alkali as a raw material and water. In the organic alkali solution preparation device, the concentration and pH of the organic alkali solution are adjusted. As a configuration of the organic alkali solution preparation device, a tank including a pipe for supplying the organic alkali, a pipe for supplying water, and a take-out pipe for taking out the prepared organic alkali solution can be exemplified. The organic alkali solution taken out from the take-out pipe is supplied to the above-described static mixer or product preparation device through a pipe through which the organic alkali solution flows. Further, the organic alkali preparation device may include a circulation-type temperature control means for controlling the temperature of the solution in the preparation device. As the circulation-type temperature control means, a pipe through which a part of the organic alkali solution taken out from the above-described take-out pipe flows, a heat exchanger for heat-exchanging the organic alkali solution supplied from the pipe, and a pipe for returning the organic alkali solution whose temperature has been controlled through the heat exchanger to the organic alkali solution preparation device, and a pump for circulating the organic alkali solution can be mentioned.

[0058] The organic alkali solution preparation device may include means for supplying nitrogen into the preparation device in order to adjust the concentration of the gas component in the gas phase part in the preparation device. As means for supplying nitrogen, a configuration including a pump for supplying nitrogen from the outside to the inside of the preparation device and a pipe through which nitrogen flows can be mentioned.

Example

[0059] Next, the present invention will be described in detail using examples and comparative examples, but the present invention is not limited to the examples.

[0060] <pH measurement method> 30 mL of an aqueous solution of quaternary alkylammonium hydroxide and 30 mL of an aqueous solution of quaternary alkylammonium hypochlorite were measured for pH using a desktop pH meter (LAQUA F-73, manufactured by Horiba, Ltd.). The pH measurement was carried out after stabilizing at 25°C.

[0061] <Calculation method for effective chlorine concentration and hypochlorite ion concentration> 0.5 mL of the treatment solution (quaternary alkylammonium hypochlorite solution), 2 g of potassium iodide (Fujifilm Wako Pure Chemical Industries, Ltd., special grade reagent), 8 mL of 10% by mass acetic acid, and 10 mL of ultrapure water were added to a 100 mL Erlenmeyer flask and stirred until the solid matter was dissolved, yielding a brown solution. The prepared brown solution was subjected to redox titration using 0.02 M sodium thiosulfate solution (Fujifilm Wako Pure Chemical Industries, Ltd., for volumetric analysis) until the color of the solution changed from brown to very pale yellow, and then starch solution was added to obtain a pale purple solution. To this solution, 0.02M sodium thiosulfate solution is further added, and the point at which the solution becomes colorless and transparent is used as the end point to calculate the effective chlorine concentration.In addition, the hypochlorite ion concentration is calculated from the obtained effective chlorine concentration.For example, if the effective chlorine concentration is 1 mass%, the hypochlorite ion concentration is 0.73 mass%.

[0062] <Chlorine yield> The chlorine yield was calculated from the ratio (%) of the number of moles of hypochlorite ions produced to the number of moles of chlorine molecules supplied. If all of the added chlorine reacts (no decomposition occurs), the chlorine yield is 100%. If hypochlorite ions decompose during the reaction, the chlorine yield decreases.

[0063] <Evaluation method for storage stability> The quaternary alkyl ammonium hypochlorite solution was transferred into a glove bag, and after the carbon dioxide concentration in the glove bag became 1 ppm or less, it was transferred into a PFA (perfluoroalkoxy fluororesin, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer) container and sealed. Next, after storing it in a light-shielded environment at 23 °C for 10 days, the PFA container The hypochlorite ion concentration of the quaternary alkyl ammonium hypochlorite solution in the container was measured. A hypochlorite ion concentration ratio (concentration after 10 days / initial concentration) of 60% to 100% was considered good, and less than 60% was considered bad.

[0064] Example 1 A 8.6% by mass tetramethylammonium hydroxide solution, pH 14.1, was supplied at 1 kg / min through a 6 mm diameter pipe. Chlorine gas was supplied at 0.29 mol / min along the flow path and then mixed using a static mixer. The solution was then cooled to 25°C using a 7.9 m long PFA heat exchanger manufactured by AS ONE. The reaction volume including the heat exchanger was 0.7 L. The chlorine yield was 98%, the pH was 13.6, the available chlorine concentration was 1.9% by mass, and the production rate was 1 L / min per 0.7 L. Storage stability was good.

[0065] <Example 2> In order to examine the effect of multi-stage chlorine supply, the same procedure as in Example 1 was carried out except that chlorine gas was supplied in two stages. The chlorine yield at this time was 99%, the pH was 13.6, the available chlorine concentration was 1.9 mass%, and the production rate was 1 L / min per 0.7 L. The storage stability was good.

[0066] Example 3 To examine the effect of the pH of the raw material, the same procedure as in Example 1 was carried out. A 2.9% by mass tetramethylammonium hydroxide solution, pH 13.6, was supplied at 1 kg / min through a 6 mm diameter pipe. Chlorine gas was supplied at 0.070 mol / min along the way and then mixed using a static mixer. The solution was then cooled to 25°C using a 7.9 m long PFA heat exchanger manufactured by AS ONE. The chlorine yield was 92%, the pH was 13.5, the available chlorine concentration was 0.41% by mass, and the production rate was 1 L / min per 0.7 L. Storage stability was good.

[0067] Example 4 In order to examine the effect of the pH of the raw material, the same procedure as in Example 3 was carried out except that the chlorine gas flow rate was changed to 0.15 mol / min. The chlorine yield at this time was 99%, the pH was 12.7, the available chlorine concentration was 0.83 mass%, and the production rate was 1 L / min per 0.7 L. The storage stability was good.

[0068] <Comparative Example> As a comparative example, an experimental example using a batch reaction will be shown. A cylindrical reactor with a diameter of 190 mm was charged with 10,000 ml of 8.6% by mass tetramethylammonium hydroxide solution with a pH of 14.0. The liquid in the reactor was circulated at 500 ml / min using a circulation pump attached to the reactor, while chlorine was supplied at 17.7 mmol / min. The resulting quaternary tetramethylammonium hypochlorite solution was removed after a liquid residence time in the reactor of 256 min. The reaction temperature was 25 °C. The resulting quaternary tetramethylammonium hypochlorite solution had an available chlorine concentration of 2.9 mass%, a pH of 12.9, and a chlorine yield of 91%. The storage stability was poor.

[0069] The reaction conditions and results are summarized in Tables 1 and 2. [Table 1] [Table 2]

[0070] [Explanation of symbols] 1. Quaternary alkyl ammonium hydroxide solution supply piping 2 Halogen supply piping 3Static mixer 4 heat exchanger Five-stage hypohalous acid quaternary alkyl ammonium solution extraction piping

Claims

1. a method for producing a halogen oxyacid solution, comprising continuously supplying an organic alkaline solution and a halogen to a static mixer, mixing the organic alkaline solution and the halogen, and continuously obtaining the resulting halogen oxyacid; the organic alkaline solution is supplied from an organic alkaline solution supply means to the static mixer, the halogen is supplied from a halogen supply means, and the halogen oxyacid solution resulting from the mixing in the static mixer is continuously removed from the static mixer by a halogen oxyacid solution removal means for removing the halogen oxyacid solution from the static mixer to the outside; the halogen oxyacid solution is removed without being circulated during the production process; and the supply rates of the raw materials are controlled so that the pH at 25°C of the mixture of the organic alkaline solution and the halogen that has passed through the static mixer is greater than 10.5 and less than 14.

1.

2. 2. The method for producing a halogen oxygen acid solution according to claim 1, wherein the pH of the mixture at 25°C is 12.0 or more and 13.8 or less.

3. 3. The method for producing a halogen oxygen acid solution according to claim 1, wherein the halogen is supplied in multiple stages.

4. The method for producing a halogen oxygen acid solution according to any one of claims 1 to 3, wherein the mixing is carried out in multiple stages.

5. The method for producing a halogen oxygen acid solution according to any one of claims 1 to 4, wherein the organic alkaline solution has a pH of 10.5 or more and 14.5 or less at 25°C.

6. 6. The method for producing a halogen oxyacid solution according to claim 1, wherein the organic alkali is onium hydroxide, and the halogen oxyacid is an onium halogen oxyacid.

7. 7. The method for producing a halogen oxygen acid solution according to claim 6, wherein the onium hydroxide is a quaternary alkyl ammonium hydroxide, and the onium halogen oxygen acid is a quaternary alkyl ammonium hypohalite.

8. 8. The method for producing a halogen oxygen acid solution according to claim 7, wherein the quaternary alkyl ammonium hydroxide is tetramethyl ammonium hydroxide.

9. The method for producing a halogen oxygen acid solution according to any one of claims 1 to 8, wherein the halogen is chlorine, bromine, hypochlorous acid, hypobromous acid, chlorous acid, bromous acid, chloric acid, bromic acid, iodine, hypoiodous acid, iodous acid, or iodic acid.

10. The method for producing a halogen oxygen acid solution according to any one of claims 1 to 9, wherein the halogen is chlorine.

11. 1. An apparatus for producing a halogen oxygen acid solution, comprising: a static mixer; an organic alkali solution supply means and a halogen supply means for supplying the organic alkali solution to the static mixer; and a reaction solution removal means for removing the reaction solution from the static mixer to the outside, An apparatus for producing a halogen oxygen acid solution, wherein an organic alkaline solution and a halogen are continuously supplied to a static mixer by an organic alkaline solution supply means and a halogen supply means, respectively, and mixed to produce a halogen oxygen acid solution as a reaction liquid, and the reaction liquid is continuously taken out by a reaction liquid taking-out means, and the reaction liquid does not circulate within the production apparatus, and the supply rate of raw materials is controlled so that the pH at 25°C of the mixed liquid of the organic alkaline solution and the halogen that has passed through the static mixer is greater than 10.5 and less than 14.

1.

12. 12. The apparatus for producing a halogen oxygen acid solution according to claim 11, further comprising one or more additional static mixers downstream of the static mixer and upstream of the reaction solution withdrawal means, and further comprising a halogen supply means for supplying halogen to each of the additional static mixers.

13. 13. The apparatus for producing a halogen oxygen acid solution according to claim 11 or 12, further comprising a heat exchanger for exchanging heat in the reaction solution.

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