Hypobromous acid solution with improved stability

Abstract

To provide a stable hypobromous acid solution that can maintain a stable bactericidal effect over a long period of time, even amid annual temperature fluctuations.SOLUTION: The stable hypobromous acid solution is achieved even at elevated temperatures by using sulfonated benzimidazole compounds as bromine stabilizers.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a water treatment agent composition capable of suppressing various disorders caused by microorganisms in various water systems and process water systems, such as cooling water systems, hot and cold water systems, dust collection water systems, paper and pulp process water systems, ironmaking process water systems, and metal processing process water systems. [Background technology]

[0002] Microorganisms that grow in various process waters, such as cooling water systems, hot and cold water systems, dust collection water systems, paper pulp process water systems, steelmaking process water systems, and metal processing process water systems, proliferate within the systems and form microbial deposits called slime and biofouling, which can cause microbial problems such as reduced heat transfer efficiency in heat exchangers, blockage of flow paths, and microbial corrosion caused by anaerobic bacteria.

[0003] As a countermeasure against microbial damage, oxidizing disinfectants with oxidizing action such as chlorine-based disinfectants, bromine-based disinfectants, and hydrogen peroxides, and non-oxidizing disinfectants such as quaternary ammonium salts, glutaraldehyde, 3-isothiazolones, organic bromine compounds, and hydrazines are used. Among these, inorganic chlorine-based disinfectants that generate hypochlorous acid and hypochlorite ions have excellent disinfecting effects and are highly safe because they decompose quickly in the environment to become harmless chlorine ions, and are widely used for disinfecting drinking water and swimming pools.

[0004] When inorganic chlorine disinfectants are dissolved in water, hypochlorite ions and undissociated hypochlorous acid are generated, but the disinfecting effect is mainly due to undissociated hypochlorous acid. The ratio of hypochlorous acid and hypochlorite ions depends on pH, with the proportion of hypochlorite ions increasing in the high pH range. This is also true for inorganic bromine disinfectants that generate hypobromous acid and hypobromite ions when dissolved in water, where the ratio of hypobromous acid and hypobromite ions also depends on pH, with the proportion of hypobromite ions increasing in the high pH range, but hypobromite has a higher ratio even at high pH compared to hypochlorous acid.

[0005] Hypochlorous acid reacts easily with nitrogen compounds such as amines to produce combined chlorine. Combined chlorine has the disadvantage of being less oxidizing and less effective at killing bacteria than hypochlorous acid, but hypobromous acid is not highly reactive with nitrogen compounds and can maintain its bactericidal effect even in the presence of nitrogen compounds, so it is often used as a disinfectant for water-based systems.

[0006] When hypobromous acid is used as a water-based disinfectant, the stability of hypobromous acid itself is low, so methods of generating hypobromous acid by reacting hypochlorous acid with bromides such as sodium bromide on-site, or generating 1-bromo-3-chloro-5,5-dimethylhydantoin (BCDMH), which reacts with water to release hypochlorous acid and hypobromous acid, are used. However, the method of reacting sodium hypochlorite with bromides requires two solution tanks and chemical injection devices, and when BCDMH is used, there is a problem that the dissolution rate cannot be controlled because BCDMH is a solid.

[0007] In order to solve these problems, a technique of using a bromine stabilizer in addition to hypobromous acid has been proposed. For example, Patent Document 1 proposes a method of incorporating (A) a compound that generates hypochlorous acid and / or hypobromous acid in water, such as chlorine, chlorine dioxide, sodium hypochlorite, potassium hypochlorite, calcium hypochlorite, bromine, sodium hypobromite, potassium hypobromite, calcium hypobromite, dichloroisocyanuric acid, trichloroisocyanuric acid, and (B) one or more selected from pyrrolidones such as 2-pyrrolidone, vinylpyrrolidone, and polyvinylpyrrolidone, and butyrolactones such as γ-butyrolactone, β-butyrolactone, and α-acetyl-γ-butyrolactone, as active ingredients. However, these proposals do not provide sufficient stability for the hypobromous acid solution, and there is a problem that sufficient stability cannot be obtained, particularly in a high temperature range exceeding 40°C. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Patent Publication No. 2002-363016 Summary of the Invention [Problem to be solved by the invention]

[0009] The present invention aims to provide a stable hypobromous acid solution capable of stably maintaining its bactericidal effect for a long period of time even under the influence of annual temperature fluctuations. [Means for solving the problem]

[0010] As a result of extensive investigations, the present inventors have found that by using a sulfobenzimid compound as a bromine stabilizer, a hypobromous acid solution that is stable even at high temperatures can be obtained. That is, the invention of claim 1 is a stable hypobromous acid solution, which contains a sulfobenzimid compound as a bromine stabilizer, and is characterized in that the molar ratio of the sulfobenzimid compound to hypobromous acid is 0.2 to 10.

[0011] The invention according to claim 2 is the hypobromous acid solution according to claim 1, characterized in that the sulfobenzimidimide compound is o-sulfobenzimidimide and / or a salt thereof.

[0012] The invention according to claim 3 is the hypobromous acid solution according to claim 1 or 2, characterized in that the pH of the solution is 13 or higher. Effect of the Invention

[0013] The water treatment composition of the present invention can be used safely without any deterioration in performance even in the hot summer months because the bactericide component contained therein has excellent high-temperature stability. Therefore, by applying the water treatment composition of the present invention to various water systems, microbial damage that is a problem in water systems can be stably and effectively suppressed throughout the year. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] The present invention will be described in detail below, but the present invention is not limited thereto. There is no particular limitation on the hypobromous acid and its salts used in the present invention, but they can be obtained by reacting sodium hypochlorite or calcium hypochlorite solution with bromine compounds such as sodium bromide, potassium bromide, and lithium bromide, or by dissolving bromine gas in water. Sodium hypobromite solution is also available as a reagent from Kanto Chemical Co., Ltd. A preferred reaction ratio of a bromide ion source compound and hypochlorite is 0.4 to 1.5 moles of bromide ion per mole of hypochlorite in terms of Cl2. If this molar ratio is less than 0.4, a sufficient amount of hypobromous acid is not generated, resulting in a poor microbial inhibition effect, and even if the molar ratio exceeds 1.5, it does not contribute to the generation of hypobromous acid, resulting in a waste of costs and resources, so neither is preferable. In the present invention, hypobromous acid includes non-dissociated hypobromous acid (HOBr) and hypobromite ion (OBr-).

[0015] In the present invention, a sulfobenzimid compound is used as a stabilizer for hypobromous acid. Examples of the sulfobenzimid compound include o-sulfobenzimid, o-sulfobenzimid salts, and o-sulfobenzimid derivatives. Specifically, examples of o-sulfobenzimid and o-sulfobenzimid salts include metal salts of o-sulfobenzimid, and examples of o-sulfobenzimid derivatives include thio-o-sulfobenzimid, N-methyl-o-sulfobenzimid, o-sulfobenzimid methyl ether, N-propoxymethoxy-o-sulfobenzimid, N-propyl-o-sulfobenzimid, N-(hydroxymethyl)-o-sulfobenzimid, and N-(2-nitrophenylthio)o-sulfobenzimid. benzimide, acetyl-o-sulfobenzimide, butyryl-o-sulfobenzimide, hexanoyl-o-sulfobenzimide, octanoyl-o-sulfobenzimide, decanoyl-o-sulfobenzimide, lauroyl-o-sulfobenzimide, myristoyl-o-sulfobenzimide, palmitoyl-o-sulfobenzimide, stearoyl-o-sulfobenzimide, cinnamoyl-o-sulfobenzimide, 3,4-dimethoxycinnamoyl-o-sulfobenzimide, 3,4,5-trimethoxycinnamoyl-o-sulfobenzimide, N-vinyl-o-sulfobenzimide, and the like.

[0016] As mentioned above, hypobromous acid, which is a free halogen, has low reactivity with nitrogen-containing compounds, but reacts with toluenesulfonamide, benzenesulfonamide, and sulfamic acid, which are often used as stabilizers for hypobromous acid, to generate bound bromine, which is a bound halogen. On the other hand, although the reason is unclear, when the sulfobenzimid compound of the present invention is used, it hardly reacts with hypobromous acid and does not generate bound bromine, so that hypobromous acid, which is a free halogen and has superior bactericidal power compared to bound bromine, can be stably present, and the stability of hypobromous acid solution can be improved.

[0017] Among the sulfobenzimidimide compounds, it is preferable to use o-sulfobenzimidimide, which has the effect of significantly improving the decomposition of hypobromous acid.

[0018] In the present invention, o-sulfobenzimide can be used as it is, or in the form of an alkali metal salt such as a sodium salt or a hydrate thereof as a metal salt of o-sulfobenzimide. The use of a metal salt of o-sulfobenzimide increases the solubility. Here, lithium, sodium, potassium, calcium, magnesium, etc. can be used as the alkali metal salt.

[0019] In the present invention, the molar ratio of the sulfobenzimid compound, which is a bromine stabilizer, to hypobromous acid is preferably 0.2 to 10, more preferably 0.5 to 2.0, and even more preferably 1.0 to 1.3. If the molar ratio of the sulfobenzimid compound to hypobromous acid is less than 0.2, sufficient stability cannot be obtained, and if it exceeds 10, the stability of the solution decreases.

[0020] In the present invention, the pH of the solution is preferably at least 13, more preferably at least 13.5. If the pH is less than 13, the decomposition rate of hypobromous acid increases, and the product stability decreases.

[0021] In the present invention, in order to improve stability, it is preferred that the total halogen concentration in the solution is less than 10%. EXAMPLES

[0022] Examples will be described below, but the present invention is not limited to these examples. The compositions of Examples 1 to 6, Comparative Examples 1 to 4, and Reference Examples 1 and 2 were obtained by mixing the components (wt%) shown in Tables 1 to 3 in the order of the numbers. The formulations were prepared by adding each component in a plastic container while stirring with a stirrer. The formulations were prepared while cooling the liquid to room temperature or below.

[0023] The total halogen concentration and free halogen concentration of the composition were measured by diethyl-p-phenylenediammonium (DPD)-ammonium iron (II) sulfate titration method. Specifically, a solution obtained by diluting the composition 10,000 times with pure water was used as a sample, and DPD and a phosphate buffer solution were added, followed by titration with ammonium iron (II) sulfate solution. The point at which the red color disappeared was taken as the end point, and the free halogen concentration (in terms of Cl2) was calculated. Then, a small amount of potassium iodide was added to the same solution, and titration was again performed with ammonium iron (II) sulfate solution until the red color disappeared. The combined halogen concentration (in terms of Cl2) was calculated from the titration amount after the addition of potassium iodide. The total halogen concentration was determined by adding the free halogen concentration and the combined halogen concentration. As the halogen residual rate, the total halogen concentration was measured after one month for the composition that was left standing in a thermostatic bath at room temperature and 40°C. In addition, the stability of the product after one month was evaluated by visually checking for the presence or absence of precipitates or separation. If precipitates or separation were present, the halogen concentration was not measured.

[0024] In the examples and comparative examples, the hypobromous acid solution was obtained by reacting 12% sodium hypochlorite solution with sodium bromide of the same molar concentration. The hypobromous acid concentration (in terms of Cl2) of this reaction product was measured by adding DPD and a phosphate buffer solution, then adding a 10% glycine solution, and titrating with ammonium iron sulfate (II) solution until the red color disappeared, in a (DPD)-ammonium iron sulfate (II) titration method. As a result, the reaction rate of sodium hypochlorite and sodium bromide was 98% or more.

[0025] From Table 1, in the cases of Examples 1 to 6, the effective halogen in the composition was free halogen, and no bonded halogen was included. As described above, almost all of it was hypobromous acid. Furthermore, when the molar ratio of the sulfobenzimid compound, which is a bromine stabilizer, to hypobromous acid was 0.2 to 10, the residual halogen concentration after one month was 50% or more at 40°C, and a stable hypobromous acid solution was obtained. Furthermore, in Examples 1 to 6, there was no problem with the product stability after one month.

[0026] From Table 2, in Comparative Examples 1 and 2, when the molar ratio of the sulfobenzimid compound, which is a bromine stabilizer, to hypobromous acid is 0.1 or less or when the pH is less than 13, the halogen residual rate at 40°C was significantly reduced. Comparative Example 3 is a hypobromous acid solution not containing a sulfobenzimid compound, which is a bromine stabilizer, and the halogen residual rate at 40°C was significantly reduced compared to Examples 1 to 6, which contain a sulfobenzimid compound. As shown in Comparative Example 4, when the molar ratio of the bromine stabilizer to hypobromous acid exceeds 10, precipitation, separation, etc. occurred, and product stability was significantly deteriorated.

[0027] In addition, the results of sulfamic acid, a representative bromine stabilizer, are shown in Reference Examples 1 and 2 in Table 3. In the case of Reference Example 1, in which the molar ratio of sulfamic acid to sodium hypobromite is 0.2, free halogen and bonded halogen are generated in a ratio of 2:1, which is different in composition from the present invention, which is mainly free halogen, and the halogen residual rate after one month was slightly lower than that of Example 1. In addition, in the case of Reference Example 2, in which the concentration of sulfamic acid was increased, the generated halogen was mainly bonded halogen, which was clearly different in composition from the present invention, which is mainly free halogen with excellent bactericidal power.

[0028] [Table 1] NaOCl (sodium hypochlorite, reagent, Fujifilm Wako Pure Chemical Industries, Ltd.) NaBr (Sodium bromide, reagent, Fujifilm Wako Pure Chemical Industries, Ltd.) o-SBI (o-sulfobenzimide, reagent, Fujifilm Wako Pure Chemical Industries, Ltd.) o-SBI Na 2H2O (o-Sulfobenzimidium sodium dihydrate, reagent, Fujifilm Wako Pure Chemical Industries, Ltd.) 50% KOH (50% potassium hydroxide, prepared by diluting Fujifilm Wako Pure Chemical Co., Ltd.'s reagent with pure water)

[0029] [Table 2]

[0030] [Table 3] NaOCl (sodium hypochlorite, reagent, Fujifilm Wako Pure Chemical Industries, Ltd.) NaBr (Sodium bromide, reagent, Fujifilm Wako Pure Chemical Industries, Ltd.) Sulfamic acid (reagent, Fujifilm Wako Pure Chemical Industries, Ltd.) 50% KOH (50% potassium hydroxide, prepared by diluting Fujifilm Wako Pure Chemical Co., Ltd.'s reagent with pure water)

Claims

1. A stable hypobromous acid solution, comprising a sulfobenzimidimide compound as a bromine stabilizer, the molar ratio of the sulfobenzimidimide compound to hypobromous acid being 0.2-10.

2. 2. The hypobromous acid solution according to claim 1, wherein the sulfobenzimidimide compound is o-sulfobenzimidimide and / or a salt thereof.

3. 3. The hypobromous acid solution according to claim 1, wherein the pH of the solution is 13 or more.

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