Hypochlorous acid water manufacturing method and manufacturing device

Abstract

The present invention addresses the problem of providing a method and an apparatus for producing an aqueous hypochlorous acid solution having a high concentration by a simple process without generating a chlorine gas in principle. According to the present invention, an acidic aqueous solution having a pH of from 1.5 to 5 and an aqueous solution containing a hypochlorite are separately and independently prepared, and these solutions are subsequently mixed with each other, thereby obtaining an aqueous hypochlorous acid solution that has a pH of from 5 to 7.

Description

[Technical Field]

[0001] The present invention relates to a method and an apparatus for producing hypochlorous acid water. [Background technology]

[0002] Conventionally, hypochlorous acid aqueous solutions (hereinafter also referred to as hypochlorous acid water) have been used as disinfectants or sterilizers in the medical, food, agricultural, household, etc. The disinfecting or sterilizing effect of hypochlorous acid aqueous solutions depends on the oxidizing power of hypochlorous acid molecules and hypochlorite ions.

[0003] There are three ways to generate hypochlorous acid solution: the electrolysis method using electrolysis of hypochlorite, the two-liquid method using the neutralization reaction between a hypochlorite solution (such as sodium hypochlorite) and an acid solution (such as hydrochloric acid), and the buffer method using a special ion exchanger to make the solution weakly acidic through an ion exchange reaction.

[0004] For example, in food manufacturing plants and agricultural fields, it is necessary to use a large amount of hypochlorous acid water as sterilizing water, but the electrolysis method requires expensive electrolysis equipment to mass-produce hypochlorous acid water, and the amount of hypochlorous acid water produced is insufficient, making it impractical.

[0005] In the two-component method, a highly concentrated, weakly acidic hypochlorous acid solution (hypochlorous acid water) with bactericidal or disinfecting effects is produced by contacting a mixture of raw water such as tap water or well water with sodium hypochlorite and reacting it with hydrochloric acid. However, the two-component method can sometimes produce chlorine gas as a by-product.

[0006] FIG. 3 is a schematic diagram of a conventional manufacturing apparatus using a two-component method. This illustrated manufacturing apparatus is designed to use hydrochloric acid and sodium hypochlorite as raw materials. In the manufacturing apparatus shown in FIG. 3, dilution water flows from a water tap 31 through a flowmeter 32 to a flow-proportional injection pump 33. Hydrochloric acid is introduced from a hydrochloric acid tank 34 to the flow-proportional injection pump 33, where it is diluted with the dilution water and then delivered to the next flow-proportional injection pump 36. A sodium hypochlorite tank 37, separate from the hydrochloric acid tank 34, stores a sodium hypochlorite solution, which is then supplied to the flow-proportional injection pump 36. The hydrochloric acid and sodium hypochlorite solution supplied to the flow-proportional injection pump 36 are mixed in a mixer 38. As a result of the mixing, hypochlorous acid water is produced. The pH of the product is measured by a pH measuring device 39, and the resulting hypochlorous acid water is sprayed by a hypochlorous acid water sprayer 310.

[0007] As prior art for the buffer method, Patent Document 1 discloses an invention of a manufacturing apparatus that includes a container filled with a weakly acidic ion exchanger for passing a hypochlorite solution, based on the recognition that chlorine gas is not substantially generated when the pH is 3.5 or higher, and is configured so that the pH of the hypochlorite solution does not decrease below the pH at which chlorine gas is generated when the hypochlorite solution passes through the container. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Patent No. 5692657 Summary of the Invention [Problem to be solved by the invention]

[0009] An object of the present invention is to provide a method and apparatus for safely and simply producing hypochlorous acid water using a two-component method. [Means for solving the problem]

[0010] As a result of extensive research, the present inventors have completed the present invention as described below. (1) A method for producing hypochlorous acid water having a pH of 5 to 7, characterized by separately preparing an acidic aqueous solution having a pH of 1.5 to 5 and an aqueous solution containing hypochlorite, and then mixing the two aqueous solutions. (2) The method of (1), wherein the acidic aqueous solution is a hydrochloric acid aqueous solution. (3) The method of (1) or (2), wherein the hypochlorite is sodium hypochlorite. (4) The method of producing (1) to (3), wherein the hypochlorous acid concentration of the hypochlorous acid water is 2240 ppm or less. (5) An apparatus for producing hypochlorous acid water, comprising: a first container capable of holding an acidic aqueous solution; a second container separate from the first container capable of holding an aqueous solution containing hypochlorite; a mixer connected to the first and second containers via piping to mix the acidic aqueous solution and the aqueous solution containing hypochlorite; and a pH measuring device capable of measuring the pH of the hydrochloric acid supplied to the mixer, wherein the piping is configured so that the contents of the first container and the second container do not come into contact with each other before being supplied to the mixer; and wherein hypochlorous acid water is produced by mixing the acidic aqueous solution and the aqueous solution containing hypochlorite in the mixer. (6) The manufacturing apparatus of (5) is provided with a memory means for storing a pH threshold value and a signal generating means for generating a signal when the measured pH of the acidic aqueous solution is lower than the pH threshold value. (7) The manufacturing apparatus (5) or (6) further comprises a spraying device connected to the mixer, the spraying device spraying the hypochlorous acid water produced in the mixer. [Effects of the Invention]

[0011] According to the new findings of the present inventors, chlorine gas is substantially generated only when hypochlorite ions are in an environment with a pH below 1.35. Therefore, if the pH of the acidic aqueous solution is adjusted to 1.5 to 5 in advance and then contacted with hypochlorite ions, concerns about chlorine gas generation can be eliminated. Specifically, in the present invention, an aqueous solution containing hypochlorite is mixed with an acidic aqueous solution adjusted to a pH value of 1.5 or higher. In the neutralization reaction, the pH of the acidic aqueous solution before the reaction does not decrease, but rather increases, so that the pH of hypochlorite does not become lower than 1.5 during the production process. Therefore, concerns about chlorine gas generation can be eliminated throughout the entire production process. Here, "substantially not generating chlorine gas" means that chlorine gas is not substantially generated at a level that is dangerous to living organisms, that chlorine bubbles are not substantially confirmed to be generated from the solution when the pH of the hypochlorite solution is lowered, or that there is substantially no bleaching action due to chlorine when the pH of the hypochlorite solution is lowered.One indicator is a state in which the pungent odor unique to chlorine is hardly detectable even when the generated aqueous hypochlorous acid solution is placed in a cup or the like and smelled directly.

[0012] According to the device of the present invention, hypochlorous acid water can be obtained safely and simply by the above-mentioned production method. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a plot of measurement results in an embodiment of the present invention. [Figure 2] FIG. 2 is a schematic diagram of the device of the present invention. [Figure 3] FIG. 3 is a schematic diagram of a manufacturing device according to the prior art. DETAILED DESCRIPTION OF THE INVENTION

[0014] The present invention will be described in detail below. In the two-liquid method, a neutralization reaction is caused by contacting an aqueous solution of hypochlorite with an acidic aqueous solution, and hypochlorous acid is obtained from hypochlorite. In the present invention, an acidic aqueous solution and an aqueous solution containing hypochlorite are prepared separately and independently. The separate and independent preparation of the two aqueous solutions means that the two aqueous solutions are not brought into contact with each other until each aqueous solution reaches a predetermined pH and concentration. This can prevent the generation of chlorine gas caused by the contact of an aqueous solution with an undesirably low pH with hypochlorite.

[0015] As mentioned above, in the prior art, it was believed that chlorine gas would be generated if the pH was lower than 3.4. On the other hand, in the conventional production apparatus shown in Fig. 3 referred to above, commercially available concentrated hydrochloric acid (pH less than 1) was used in the hydrochloric acid tank 34. With such conventional production apparatus, chlorine was sometimes generated undesirably, and for this reason, the use of an acidic aqueous solution with a pH in the range of 1 to 3.5 had not even been considered.

[0016] In contrast, in the present invention, the lower limit of the pH of the acidic aqueous solution to be prepared is 1.5, with preferred lower limits being 1.75 and 2.0. A preferred upper limit of the pH of the acidic aqueous solution to be prepared is 2.1. When the pH is 2.1 or less, hypochlorous acid water containing a significantly higher concentration of hypochlorous acid can be obtained. To neutralize the alkaline hypochlorite aqueous solution, the pH of the acidic aqueous solution must be low. However, from the viewpoint of preventing the generation of chlorine gas, a too low pH is inappropriate. From these viewpoints, the above pH range is recommended. Within the above range, the pH of the acidic aqueous solution to be prepared can be set based on the concentration and pH of the hypochlorous acid water finally obtained, taking into account the stoichiometry of the neutralization reaction described below. Figure 1 is a plot of the amount of sodium hypochlorite added and the pH of the product in the examples described below. When setting the pH of the acidic aqueous solution to be prepared, the relationship between the amount added and pH as shown in Figure 1 can also be utilized. The specific details of Figure 1 will be described in detail in the Examples section below.

[0017] The acid in the acidic aqueous solution is not particularly limited, and examples thereof include hydrochloric acid, acetic acid, citric acid, etc. Considering the use of the hypochlorous acid water to be finally obtained, it is preferable to use hydrochloric acid or citric acid, which have less adverse effects on the human body.

[0018] The concentration of hypochlorite to be prepared can be set by considering the concentration of hypochlorous acid water to be finally obtained.Specifically, if the aqueous solution that contains 1 mol of hypochlorite ion is neutralized with acid, the aqueous solution that contains 1 mol of hypochlorous acid can be obtained.The concentration of hypochlorite can be determined by considering the stoichiometry.

[0019] There are no particular limitations on the hypochlorite salt, and typical examples include alkali metal salts, particularly sodium salts, but these are not limited thereto.

[0020] An example of a method for setting the pH and concentration of the acidic aqueous solution and the aqueous solution containing hypochlorite, which are prepared separately and independently, is as follows. The total amount of water and the amount of hypochlorite (ion) are determined from the target concentration of hypochlorous acid in the hypochlorous acid water that is finally obtained.The pH of the acidic aqueous solution that is prepared in advance is determined from the amount of acid that is required to neutralize hypochlorite into hypochlorous acid and the target pH of the hypochlorous acid water that is finally obtained.These specific numerical examples can also be referred to in the examples that will be described later.

[0021] The pH of the resulting hypochlorous acid water is preferably 5 to 7, more preferably 5.5 to 6.5. Within this pH range, the water can be safely used on foods and the like, and a suitable sterilizing and disinfecting effect can be obtained.

[0022] The concentration of hypochlorous acid in the obtained hypochlorous acid water is not particularly limited, and a preferred upper limit is 2,440 ppm, which is the upper limit of the concentration of hypochlorous acid in this production method, which in principle does not generate chlorine gas. A concentration below this upper limit can be selected as appropriate, taking into account storage and transportation costs, sterilization and disinfection effects, etc.

[0023] There are no particular limitations on the specific means for separately preparing the acidic aqueous solution and the aqueous solution containing hypochlorite, or the specific method for mixing the two aqueous solutions, and techniques in the prior art can be referenced as appropriate.

[0024] The present invention also provides a manufacturing device that can produce hypochlorous acid water by implementing the above-mentioned method. The device includes at least a first container, a second container, a mixer, piping connecting them, and a pH measuring device. Figure 2 is a schematic diagram of the device of the present invention. Figure 2 is depicted on the assumption that hydrochloric acid is used as the acidic aqueous solution and sodium hypochlorite is used as the hypochlorite. However, the present invention is not limited to such use.

[0025] The first container is for containing an acidic aqueous solution having a pH of 1.5 to 5. In FIG. 2, the mixing tank designated by the reference numeral 26 corresponds to the "first container." The first container may simply be capable of containing a liquid, or may further have a function for mixing with water for dilution, as will be described later. If the pH of the acidic aqueous solution is 1.5 to 5, chlorine gas will not be generated, and specific examples of the method for producing such an acidic aqueous solution are as described above. There are no particular limitations on the material, shape, etc. of the first container as long as it can contain the acidic aqueous solution, and examples include an acid-resistant metal container, a glass container, and an acid-resistant plastic container.

[0026] The apparatus shown in FIG. 2 is equipped with a water tap 21 as a source of water for dilution, a flow meter 22, a flow-proportional injection pump 23, a hydrochloric acid tank 24 as a container for the acid that is the raw material before dilution, and a mixer 25 for diluting the acid with water, in order to prepare the acidic aqueous solution to be contained in the first container.

[0027] The second container is for storing an aqueous solution containing hypochlorite. In FIG. 2, the sodium hypochlorite tank designated by the reference numeral 28 corresponds to the "second container." The manufacturing method and properties of the aqueous solution containing hypochlorite are as described above. The material, shape, etc. of the second container are not particularly limited as long as they can store the aqueous solution, and examples include an alkali-resistant metal container, a glass container, and an alkali-resistant plastic container. In the apparatus of FIG. 2, the second container is designated by the reference numeral 28.

[0028] The first and second containers are provided separately and independently from each other, meaning that the contents of the first and second containers are separated to such an extent that they do not mix without user interaction.

[0029] The contents of the first and second containers are mixed in a mixer 29, indicated by the reference numeral 29. In the apparatus of FIG. 2, the contents of the mixing tank 26 and the sodium hypochlorite tank 29 are mixed. 28 Contents Things The mixture is supplied to mixer 29 using flow-proportional injection pump 27. The flow paths from the two tanks 26 and 28 to mixer 29 are connected by piping, and the flow-proportional injection pump 27 constitutes all or part of the piping. The piping is configured so that the content of mixing tank 26 and the content of sodium hypochlorite tank 28 do not come into contact with each other before being supplied to mixer 29.

[0030] As mentioned above, contact between an acidic aqueous solution having a pH lower than a predetermined value and an aqueous solution containing hypochlorite increases the risk of chlorine gas generation, so the pH of the acidic aqueous solution supplied to the mixer 29 should be strictly controlled. The apparatus of the present invention is provided with a pH measuring device that measures the pH of the acidic aqueous solution before it is supplied to the mixer. In the apparatus of FIG. 2, the pH measuring device is designated by the symbol 210. A commercially available pH meter or the like can be used as the pH measuring device.

[0031] If the acidic aqueous solution in the first container has an undesirably low pH, it is desirable to prevent contact with an aqueous solution containing hypochlorite. Therefore, the pH measuring device 210 preferably includes a memory (not shown) for storing a pH threshold value and a signal generating means (not shown) for generating a signal when the measured pH of the acidic aqueous solution is lower than the pH threshold value. For example, the memory in the pH measuring device 210 that stores information such as "the pH threshold value is 1.4" corresponds to the memory generating means. Examples of signals generated by the signal generating means include a signal to stop the operation of the entire device, a buzzer (sound) or a warning light (light) to notify the user of an abnormality, and so on. When the measured pH value of the acidic aqueous solution is lower than the threshold value, the above-mentioned signal is generated, and the device is stopped automatically or by user operation, thereby preventing the generation of chlorine gas.

[0032] In the device of the present invention, hypochlorous acid water is generated by mixing an acidic aqueous solution with an aqueous solution containing hypochlorite in the mixer 29. The generated hypochlorous acid water can be used in any way. Preferably, a spraying device is connected to the mixer 29, from which the hypochlorous acid water can be sprayed. In the device of FIG. 2, the spraying device corresponds to the hypochlorous acid spraying device indicated by the reference numeral 211. A spraying device of conventionally known material and shape can be appropriately selected and used. [Example]

[0033] In the examples, the following parameters were measured as follows: pH: The pH in the reaction system was continuously measured using a portable pH meter HM-30P manufactured by Toa DKK. Hypochlorous acid concentration: The available chlorine concentration was measured using an available chlorine concentration measurement kit AQ-202P manufactured by Shibata Scientific Co., Ltd., and converted into hypochlorous acid concentration. Chlorine gas: The presence or absence of chlorine gas generation was determined by sensory testing (smell).

[0034] Example 1 First, hydrochloric acid was diluted with pure water to prepare dilute hydrochloric acid with a pH of 4.03. Separately from the dilute hydrochloric acid, a 100,000 ppm aqueous sodium hypochlorite solution was prepared. 0.2 ml of the sodium hypochlorite solution was added to 1 liter of the dilute hydrochloric acid, and the pH and hypochlorous acid concentration were measured. The amount of sodium hypochlorite solution added (referred to as "addition amount"), the pH (referred to as "pH"), and the hypochlorous acid concentration (referred to as "hypochlorous acid concentration") measured as described above are summarized below. Furthermore, the amount added was plotted on the horizontal axis and pH on the vertical axis as "A" in Figure 1. In this way, approximately 1 liter of hypochlorous acid water (pH 6.56, concentration 42 ppm) was obtained. No odor of chlorine gas was generated from the start of production to the end of production.

[0035] Amount added pH Hypochlorous acid concentration 0ml 4.03 0ppm 0.2ml 5.90 26ppm 0.4ml 6.56 42ppm

[0036] <Example 2> Approximately 1 liter of hypochlorous acid water (pH 6.77, concentration 62 ppm) was obtained by the same process as in Example 1, except that the pH of the dilute hydrochloric acid prepared initially was adjusted to 3.45 instead of 4.03. As in Example 1, the "addition amount," "pH," and "hypochlorous acid concentration" were measured. The measurement results are summarized below and are further plotted in Figure 1, "B," with the addition amount on the horizontal axis and pH on the vertical axis. No odor of chlorine gas was generated from the start of production to production and after production.

[0037] Amount added pH Hypochlorous acid concentration 0ml 3.45 0ppm 0.2ml 5.34 25ppm 0.4ml 6.23 39ppm 0.6ml 6.77 62ppm

[0038] Example 3 Approximately 1 liter of hypochlorous acid water (pH 6.68, concentration 88 ppm) was obtained by the same process as in Example 1, except that the pH of the dilute hydrochloric acid prepared initially was adjusted to 3.02 instead of 4.03. As in Example 1, the "addition amount," "pH," and "hypochlorous acid concentration" were measured. The measurement results are summarized below and are further plotted in Figure 1, "C," with the addition amount on the horizontal axis and pH on the vertical axis. No odor of chlorine gas was generated from the start of production to production and after production.

[0039] Amount added pH Hypochlorous acid concentration 0ml 3.02 0ppm 0.2ml 3.34 22ppm 0.4ml 4.92 48ppm 0.6ml 6.16 67ppm 0. 8 ml 6.68 88ppm

[0040] Example 4 First, hydrochloric acid was diluted with pure water to prepare dilute hydrochloric acid with a pH of 2.51. Separately from the dilute hydrochloric acid, a 100,000 ppm aqueous sodium hypochlorite solution was prepared. 1 ml of the sodium hypochlorite solution was added to 1 liter of the dilute hydrochloric acid, and the pH and hypochlorous acid concentration were measured. The amount of sodium hypochlorite solution added (referred to as "addition amount"), the pH (referred to as "pH"), and the hypochlorous acid concentration (referred to as "hypochlorous acid concentration") measured as described above are summarized below, and further plotted as "D" in Figure 1, with the addition amount on the horizontal axis and pH on the vertical axis. In this way, approximately 1 liter of hypochlorous acid water (pH 6.53, concentration 300 ppm) was obtained. No odor of chlorine gas was generated from the start of production to the end of production.

[0041] Amount added pH Hypochlorous acid concentration 0ml 2.51 0ppm 1ml 2.74 142ppm 2ml 3.24 218ppm 3ml 6.53 300ppm

[0042] <Example 5> Approximately 1 liter of hypochlorous acid water (pH 6.55, concentration 930 ppm) was obtained by the same process as in Example 4, except that the pH of the diluted hydrochloric acid prepared initially was adjusted to 2.02 instead of 2.51. As in Example 4, the "addition amount," "pH," and "hypochlorous acid concentration" were measured. The measurement results are summarized below and are further plotted in Figure 1, "E," with the addition amount on the horizontal axis and pH on the vertical axis. No odor of chlorine gas was generated from the start of production to production and after production.

[0043] Amount added pH Hypochlorous acid concentration 0ml 2.02 0ppm 1ml 2.10 73ppm 2ml 2.17 215ppm 3ml 2.24 327ppm 4ml 2.35 368ppm 5ml 2.49 464ppm 6ml 2.69 522ppm 7ml 3.01 585ppm 8ml 5.49 645ppm 9ml 6.55 930ppm

[0044] Example 6 Approximately 1 liter of hypochlorous acid water (pH 6.52, concentration 1150 ppm) was obtained by the same process as in Example 4, except that the pH of the diluted hydrochloric acid prepared initially was adjusted to 1.75 instead of 2.51. As in Example 4, the "addition amount," "pH," and "hypochlorous acid concentration" were measured. The measurement results are summarized below and are further plotted in Figure 1, "F," with the addition amount on the horizontal axis and pH on the vertical axis. No odor of chlorine gas was generated from the start of production to production and after production.

[0045] Amount added pH Hypochlorous acid concentration 0ml 1.75 0ppm 1ml 1.83 133ppm 2ml 1.88 254ppm 3ml 1.97 312ppm 4ml 2.05 388ppm 5ml 2.14 440ppm 6ml 2.26 468ppm 7ml 2.41 585ppm 8ml 2.64 666ppm 9ml 3.19 788ppm 10ml 6.00 844ppm 11ml 6.52 1150ppm

[0046] Example 7 Approximately 1 liter of hypochlorous acid water (pH 6.65, concentration 2240 ppm) was obtained by the same process as in Example 4, except that the pH of the dilute hydrochloric acid prepared initially was adjusted to 1.50 instead of 2.51. As in Example 4, the "addition amount," "pH," and "hypochlorous acid concentration" were measured. The measurement results are summarized below and are further plotted in Figure 1, "G," with the addition amount on the horizontal axis and pH on the vertical axis. No odor of chlorine gas was generated from the start of production to production and after production.

[0047] Amount added pH Hypochlorous acid concentration 0ml 1.50 0ppm 1ml 1.55 111pm 2ml 1.58 211pm 3ml 1.62 294pm 4ml 1.68 336pm 5ml 1.70 405pm 6ml 1.74 460pm 7ml 1.78 496pm 8ml 1.83 612pm 9ml 1.88 696pm 10ml 1.95 732pm 11ml 2.02 768pm 12ml 2.09 844pm 13ml 2.18 872pm 14ml 2.28 1056ppm 15ml 2.42 1215ppm 16ml 2.56 1386ppm 17ml 2.79 1519ppm 18ml 3.19 1544ppm 19ml 5.42 1680ppm 20ml 6.19 1850ppm 21ml 6.48 1930ppm 22ml 6.65 2240ppm

[0048] <Comparative Example 1> First, hydrochloric acid was diluted with pure water to prepare dilute hydrochloric acid with a pH of 1.35. Separately from the dilute hydrochloric acid, a 100,000 ppm aqueous sodium hypochlorite solution was prepared. 1 ml of the above aqueous sodium hypochlorite solution was added to 1 liter of the above dilute hydrochloric acid. After the addition, the reaction solution was stirred while continuously measuring the pH of the reaction solution. The pH gradually increased and eventually stabilized, but after about an hour, the odor of chlorine gas was emitted. For safety reasons, the process was terminated at this stage. As a result, in this example, hypochlorous acid water could not be obtained safely.

[0049] <Comparative Example 2> The same process as in Comparative Example 1 was attempted, except that the pH of the diluted hydrochloric acid prepared initially was adjusted to 1.30 instead of 1.35. When 1 ml of the sodium hypochlorite aqueous solution was added to 1 liter of the diluted hydrochloric acid, the reaction solution turned yellow after a few minutes and the smell of chlorine gas was emitted. For safety reasons, the process was terminated at this stage. As a result, in this example, hypochlorous acid water could not be obtained in a safe process.

[0050] <Comparative Example 3> The same process as in Comparative Example 1 was attempted, except that the pH of the diluted hydrochloric acid prepared initially was adjusted to 1.15 instead of 1.35. When 1 ml of the sodium hypochlorite aqueous solution was added to 1 liter of the diluted hydrochloric acid, the reaction solution turned yellow after a few minutes and the smell of chlorine gas was emitted. For safety reasons, the process was terminated at this stage. As a result, in this example, hypochlorous acid water could not be obtained in a safe process.

[0051] Example 8 First, citric acid was diluted with pure water to prepare a citric acid aqueous solution with a pH of 1.88. Separately from the citric acid aqueous solution, a 100,000 ppm sodium hypochlorite aqueous solution was prepared. 40 ml of the sodium hypochlorite aqueous solution was added to 50 ml of the citric acid aqueous solution. After the addition, the reaction solution was stirred while continuously measuring the pH of the reaction solution. The pH gradually increased and stabilized at 6.00. The hypochlorous acid concentration obtained by the neutralization reaction at this time was equivalent to 44,400 ppm. In this way, approximately 90 ml of hypochlorous acid water (pH 6.00) was obtained. No chlorine gas odor was generated during or after this production. Therefore, this example also constitutes an embodiment of the present invention.

[0052] Example 9 The pH of the initially prepared citric acid aqueous solution was adjusted to 2.01 instead of 1.88, and the amount of 100,000 ppm sodium hypochlorite aqueous solution added to 50 ml of this citric acid aqueous solution was changed to 11 ml, but the same process as in Example 8 was used to obtain approximately 61 ml of hypochlorous acid water. The hypochlorous acid concentration obtained by the neutralization reaction at this time corresponds to 18,000 ppm. The measured pH of this hypochlorous acid water was 6.19, and no chlorine gas odor was generated during or after the production. Therefore, this example also constitutes an embodiment of the present invention.

[0053] Example 10 The pH of the initially prepared citric acid aqueous solution was adjusted to 2.75 instead of 1.88, and the amount of 100,000 ppm sodium hypochlorite aqueous solution prepared separately was changed to 1 ml per 50 ml of this citric acid aqueous solution, but the same process as in Example 8 was used to obtain approximately 51 ml of hypochlorous acid water. The hypochlorous acid concentration obtained by the neutralization reaction at this time corresponds to 1900 ppm. The measured pH of this hypochlorous acid water was 6.04, and no chlorine gas odor was generated during or after the production. Therefore, this example also constitutes an embodiment of the present invention.

[0054] Example 11 The pH of the initially prepared citric acid aqueous solution was adjusted to 3.05 instead of 1.88, and the amount of 100,000 ppm sodium hypochlorite aqueous solution added to 50 ml of this citric acid aqueous solution was changed to 0.3 ml, but the same process as in Example 8 was used to obtain approximately 50.3 ml of hypochlorous acid water. The hypochlorous acid concentration obtained by the neutralization reaction at this time corresponds to 596 ppm. The measured pH of this hypochlorous acid water was 6.24, and no chlorine gas odor was generated during or after the production. Therefore, this example also constitutes an embodiment of the present invention.

[0055] Illustrative embodiments of the present invention have been described in detail above. Various modifications and additions may be made without departing from the spirit and scope of the present invention. Features of each of the various embodiments described above may be combined with features of other described embodiments as needed to provide a combination of features in related new embodiments. Furthermore, while the above description describes embodiments of the method and apparatus of the present invention, these are merely illustrative of the application of the principles of the present invention. [Explanation of symbols]

[0056] 21 Faucet 22 Flow meter 23 Flow proportional injection pump 24 Hydrochloric acid tank 25 Mixer 26 Mixing tank 27 Flow proportional injection pump 28 Sodium hypochlorite tank 29 Mixer 210 pH measuring device 211 Hypochlorous Acid Sprayer 31 Faucet 32 Flow meter 33 Flow proportional injection pump 34 Hydrochloric acid tank 36 Flow proportional injection pump 37 Sodium hypochlorite tank 38 Mixer 39 pH measuring device 310 Hypochlorous Acid Sprayer

Claims

1. The system comprises: a first container capable of accommodating an acidic aqueous solution; a second container separate from the first container capable of accommodating an aqueous solution containing hypochlorite; a mixer connected to the first and second containers via piping and capable of mixing the acidic aqueous solution and the aqueous solution containing hypochlorite; and a pH measuring device capable of measuring the pH of the acidic aqueous solution supplied to the mixer; The pH measuring device includes a memory means for storing a pH threshold value, and a signal generating means for generating a signal when the measured pH of the acidic aqueous solution is lower than the pH threshold value, when the actual pH value of the acidic aqueous solution measured by the pH measuring device is lower than the threshold value, the signal issuing means issues the signal, the operation of the device is automatically stopped, and generation of chlorine gas is prevented, The piping is configured so that the contents of the first container and the contents of the second container do not come into contact with each other before being fed to the mixer, and hypochlorous acid water is produced by mixing the acidic aqueous solution and the aqueous solution containing hypochlorite in the mixer. This is an apparatus for producing hypochlorous acid water.

2. The manufacturing apparatus according to claim 1, further comprising a spraying device connected to the mixer, the spraying device spraying the hypochlorous acid water produced in the mixer.

3. A method for suppressing the generation of chlorine gas when producing hypochlorous acid water having a pH of 5 to 7 by mixing an acidic aqueous solution with an aqueous solution containing hypochlorite, A method for suppressing the generation of chlorine gas, characterized by adjusting the pH of the acidic aqueous solution to 1.5 to 5.

4. 4. The method for inhibiting the generation of chlorine gas according to claim 3, wherein the acidic aqueous solution is an aqueous hydrochloric acid solution.

5. 5. The method for inhibiting the generation of chlorine gas according to claim 3, wherein the hypochlorite is sodium hypochlorite.

6. The method for suppressing the generation of chlorine gas according to any one of claims 3 to 5, wherein the hypochlorous acid concentration of the hypochlorous acid water is 2240 ppm or less.

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