JP6808201B2 - Manufacturing method of weakly acidic hypochlorous acid water - Google Patents

Description

The present invention relates to a method for producing weakly acidic hypochlorous acid water.

The form of hypochlorous acid in an aqueous solution changes depending on the pH. Specifically, most of them are present as molecular type hypochlorous acid (HClO) in a weakly acidic region having a pH of about 3 to 6, and dissociated hypochlorite ions (OCl ⁻ ) are present in a basic region having a pH of 9 or more. In the strongly acidic region (for example, less than pH 3), the generation of chlorine molecules (Cl ₂ ) becomes predominant as the pH decreases. Among these existing forms, molecular hypochlorous acid (HClO) has an extremely high bactericidal effect, and it is said that the bactericidal effect is about 80 times that of ionic hypochlorous acid (OCl ⁻ ). A weakly acidic hypochlorous acid aqueous solution having a pH of 3 to 6 containing a large amount of molecular-type hypochlorous acid having such a high bactericidal effect has relatively high safety to the human body, and thus is used in medical, dental, agricultural, food processing, etc. , Used as a disinfectant or disinfectant in various fields. In recent years, it has come to be used for public facilities such as nursing care facilities, educational facilities, commercial facilities, and for sterilization and sterilization in general households, and its consumption is increasing year by year.

As a method for producing such a weakly acidic hypochlorite aqueous solution, an electrolysis method for electrolyzing an aqueous sodium chloride solution (see Patent Document 1) and a hydrochloric acid method for adding hydrochloric acid to a basic aqueous hypochlorite solution (Patent). (Refer to Document 2) and a method of treating a raw material aqueous solution composed of an aqueous hypochlorite solution with an acidic ion exchange resin (hereinafter, also simply referred to as “ion exchange method”; Patent Documents 3 and 4) are known.

Among these methods, the ion exchange method does not require a special device such as an electrolyzer, does not easily generate dangerous chlorine gas, and is a method for easily and safely producing a weakly acidic hypochlorous acid aqueous solution. It is an excellent method.

Japanese Unexamined Patent Publication No. 2011-11186 Japanese Unexamined Patent Publication No. 2013-39553 Special Table 2011-509275 Japanese Unexamined Patent Publication No. 2013-001620

Although the ion exchange method has the above-mentioned excellent advantages, it has been found by the studies of the present inventors that there is room for improvement in terms of the utilization rate of effective chlorine. That is, the ion exchange method includes a so-called batch method in which an acidic ion exchange resin and a raw material aqueous solution are uniformly mixed and contacted, and a raw material aqueous solution is circulated and contacted with an acidic ion exchange resin immobilized in a column or the like. There is a so-called distribution method (also called column method), but in either method, a part of the produced molecular hypochlorous acid is decomposed during production, and the effective chlorine contained in the raw material aqueous solution is lost. It became clear that they were doing. Specifically, in the batch method, a decrease in the effective chlorine concentration was observed while mixing and stirring the acidic ion exchange resin and the raw material aqueous solution, and in the distribution method, at the initial stage (contact by distribution). It has been clarified that the concentration of effective chlorine contained in the flowing water (for a while after the start of) is 0 or extremely low.

Therefore, the present invention provides a method capable of reducing the loss of effective chlorine and more efficiently producing a weakly acidic hypochlorous acid aqueous solution when producing a weakly acidic hypochlorous acid aqueous solution by an ion exchange method. The purpose.

In general, molecular-type hypochlorous acid in an aqueous solution undergoes autolysis (2HClO → 2HCl + O ₂ and / or 3HClO → 2HCl + HClO ₃ ) or when it comes into contact with an organic substance, even in a weakly acidic region with a pH of about 3 to 6. It is known that it disappears due to rapid reductive decomposition [HClO → HCl + (O)].

Based on these findings, the present inventors have found that the loss of effective chlorine is a strong active point on the surface of the acidic ion exchange resin that reduces and decomposes even a low concentration of molecular hypochlorous acid. (Hereinafter, also referred to as "surface reducing active point") was considered to be due to the existence. In the distribution method, the active chlorine concentration in the effluent rises and becomes steady shortly after the start of distribution, so that the active site gradually disappears due to contact with molecular hypochlorous acid. In addition to the analogy, the analogy was further advanced, and it was considered that the above-mentioned problem could be solved by treating with an oxidizing agent in advance, and a diligent study was conducted.

As a result, the effective chlorine as described above is obtained by contacting the acidic ion exchange resin with the oxidant aqueous solution until the oxidizing agent having 0.3 mol equivalent or more and 1.0 mol equivalent or less per liter of the acidic ion exchange resin is reduced. We have found that the loss of the above can be reduced, and have completed the present invention.

That is, in the present invention, a molecular hypochlorous acid ion exchange resin and a raw material aqueous solution composed of an aqueous solution of a metal salt of hypochlorous acid are brought into contact with each other to perform ion exchange between metal ions and hydrogen ions. A method for producing a weakly acidic hypochlorous acid aqueous solution including an ion exchange step of generating chloric acid, which comprises 1 liter of an acidic ion exchange resin and an oxidant aqueous solution in which an oxidizing substance is dissolved. A pretreatment step including an oxidation treatment step of contacting the acidic ion exchange resin with the aqueous solution of the oxidizing agent is further included until the oxidizing agent having an equivalent amount of 0.3 mol or more and 1.0 mol equivalent or less is reduced. The production method is characterized in that the acidic ion exchange resin that has undergone the pretreatment step is brought into contact with the raw material aqueous solution.

In the above method, the oxidizing substance is at least one compound selected from the group consisting of molecular hypochlorous acid, chlorine dioxide, hydrogen peroxide, ozone, and organic peroxides. Preferably, the acidic ion exchange resin is a weakly acidic ion exchange resin. Further, the pretreatment step preferably further includes a washing step of washing the acidic ion exchange resin oxidized in the oxidation treatment step with ion-exchanged water or pure water.

According to the production method of the present invention, when producing a weakly acidic hypochlorous acid aqueous solution by an ion exchange method, the acidic ion exchange resin and the raw material aqueous solution are treated by treating the acidic ion exchange resin with the oxidizing agent aqueous solution in advance. It is possible to suppress the loss of molecular hypochlorous acid that occurs at the time of contact. Therefore, according to the production method of the present invention, a weakly acidic hypochlorous acid aqueous solution can be produced more efficiently.

The reduction of the loss of molecular hypochlorous acid by the pretreatment is probably due to the active points (surface reduction) present on the surface of the acidic ion exchange resin that cause a reduction reaction of molecular hypochlorous acid. This is probably because the sexual activity point) disappeared by the oxidant treatment.

In the production method of the present invention, an acidic ion exchange resin and a raw material aqueous solution composed of an aqueous solution of a metal salt of hypochlorous acid are brought into contact with each other to perform ion exchange between metal ions and hydrogen ions. A method for producing a weakly acidic hypochlorous acid aqueous solution, which comprises an ion exchange step of generating chloric acid, wherein an acidic ion exchange resin and an oxidizing agent aqueous solution in which an oxidizing substance is dissolved are used as an acidic ion exchange resin. A pretreatment step having an oxidation treatment step of contacting the acidic ion exchange resin with the oxidizing agent aqueous solution is further included until the oxidizing agent having an equivalent amount of 0.3 mol or more and 1.0 mol equivalent or less per liter is reduced, and the ion exchange The step is characterized in that the acidic ion exchange resin that has undergone the pretreatment step is brought into contact with the raw material aqueous solution.

The production method of the present invention has the greatest feature in that the acidic ion exchange resin is pretreated with an aqueous oxidizing agent before the ion step, and the ion step itself is not particularly different from the conventional method. That is, the weakly acidic aqueous solution in which the molecular hypochlorous acid is dissolved, which is the object of the production method of the present invention, is generally called a weakly acidic hypochlorous acid aqueous solution, and the ion exchange step is a conventional method. Similar to the ion exchange method, an acidic ion exchange resin and an aqueous solution of a raw material composed of an aqueous solution of a metal salt of hypochlorous acid are brought into contact with each other to exchange ions between metal ions and hydrogen ions to exchange molecular hypochlorite. It produces acids.

Therefore, as the acidic ion exchange resin and the raw material aqueous solution, those that can be used in the conventional ion exchange method can be used without particular limitation, and the ion exchange step is also conventional except that the acid ion exchange resin that has been pretreated is used. It can be carried out in the same manner as the ion exchange method. Including these, the production method of the present invention will be described in detail below.

1. 1. Pretreatment Step The pretreatment step in the production method of the present invention is not particularly limited as long as it includes an oxidation treatment step, but when a substance other than molecular hypochlorous acid is used as the oxidizing agent, the oxidation thereof. In order to prevent the agent from being mixed in the product, it is preferable to carry out water washing (washing step) after the oxidation treatment step. Hereinafter, these steps will be described.

[Oxidation process]
In the oxidation treatment step, the acidic ion exchange resin and the oxidant aqueous solution in which the oxidizing substance is dissolved are brought into contact with each other. The contact probably caused the surface-reducing active points of the acidic ion exchange resin to be oxidized and disappeared, but the decomposition of the molecular hypochlorous acid generated in the ion exchange step was suppressed and the effective chlorine loss. Can be reduced.

Used in the oxidation treatment step as is (treated as) an acidic ion exchange resin, a weakly acidic ion having a sulfonic acid group (-SO 3 _H) strongly acidic ion-exchange resin and a carboxyl group having a (-COOH) as an ion-exchange group Replacement resin is used. Such an ion exchange resin usually has a structure in which an sulfonic acid group or a carboxyl group is introduced as an ion exchange group into a resin obtained by polymerizing acrylic acid, methacrylic acid, maleic acid or the like and three-dimensionally cross-linking with divinylbenzene. In particular, a weakly acidic ion exchange resin having a carboxyl group as an ion exchange group has a buffering action and does not lower the pH of the treated aqueous solution to a value lower than about 5 even when used in a large amount. There is no danger of generating chlorine gas. Further, the weakly acidic ion exchange resin has a feature that it can be easily regenerated (the ion exchange group can be returned to the -COOH form) by treating it with a chemical such as hydrochloric acid or sulfuric acid aqueous solution after use. Therefore, it is preferable to use a weakly acidic ion exchange resin because of its safety and ease of handling.

The oxidant aqueous solution used in the oxidation treatment step consists of an aqueous solution in which an oxidizing substance is dissolved. When the oxidizing agent aqueous solution contains a large amount of metal cations, the metal cations exchange ions with H ⁺ in the ion exchange group of the acidic ion exchange resin, so that the ion exchange ability in the ion exchange step is lowered. I will end up. Therefore, the lower the metal cation concentration in the oxidant aqueous solution, the better, and it is most preferable that the metal cation concentration is completely absent. However, depending on the oxidizing substance (oxidizing agent) used, metal cations may be contained in an aqueous solution even when an oxidizing agent other than a metal salt or a metal compound is used. In such a case, in order to obtain a more efficient production method without lowering the ion exchange ability in the pretreatment step, the total valence of metal cations (eq) is set to the total amount of the ion exchange resin. It is preferably 1/5 or less, preferably 1/10 or less, and more preferably 1/15 or less with respect to the ion exchange equivalent (eq).

The oxidizing substance (oxidizing agent) dissolved in the aqueous solution of the oxidizing agent is a substance having water solubility and functioning as an oxidizing agent, and a compound containing no metal as a constituent element is used. Examples of oxidative substances that can be preferably used include molecular hypochlorous acid, chlorine dioxide, hydrogen peroxide, ozone, and organic peroxides such as methyl ethyl ketone peroxide and benzoyl peroxide. Among these, an oxidizing agent composed of an inorganic compound that does not affect the physical properties and stability even if it cannot be completely washed and remains in the washing step is preferable, and hypochlorous acid, which is the same component as the target product, is preferable. Most preferred.

The amount of the oxidizing substance (oxidizing agent) used in the oxidation treatment step may be 0.3 mol equivalent or more per liter of the acidic ion exchange resin, but in particular, 0.35 mol equivalent is required for sufficient treatment. The above is preferable, and 0.4 mol equivalent or more is most preferable. The upper limit is not particularly limited as long as the contact conditions can be controlled, but from the viewpoint of preventing overuse, 2.0 mol equivalent or less, particularly 1.5 mol equivalent or less is based on the same standard. Is preferable.

Here, the mol equivalent is a value obtained by multiplying the number of moles of atoms whose oxidation number changes in an oxidizing substance by the amount of change in the oxidation number. For example, in the case of hypochlorous acid, the atom whose oxidation number changes when hypochlorous acid is reduced is chlorine, and the number of moles of chlorine is the same as that of hypochlorous acid. Further, the change in the oxidation number of chlorine when the hypochlorous acid is reduced to chlorine ions changes from +1 to -1, so the amount of change is 2. Therefore, the mol equivalent of hypochlorous acid is the value obtained by multiplying the number of moles of hypochlorous acid by 2.
The concentration of the oxidizing substance (oxidizing agent) in the oxidizing agent aqueous solution depends on the amount of the acidic ion exchange resin to be treated, the amount of the oxidizing agent aqueous solution used, the solubility of the oxidizing substance used, and the like. It may be appropriately determined so that the total amount of the substance (oxidizing agent) is within the above range.

The method of contacting the oxidant aqueous solution and the acidic ion exchange resin is not particularly limited. For example, the acidic ion exchange resin and the oxidizing substance are placed in the same container and mixed and stirred so as to be in a uniform state. A method (batch method) or a method of flowing an oxidizing substance through a column filled with an acidic ion exchange resin {column method (also referred to as a distribution method)} can be adopted.

In the oxidation treatment step, in order to obtain the desired effect, the oxidizing substance is used with the acidic ion exchange resin until it is reduced to an amount of 0.3 mol equivalent or more and 1.0 mol equivalent or less per liter of the acidic ion exchange resin. Contact with an aqueous oxidant. If it is below the above lower limit, the decomposition of molecular hypochlorous acid in the ion exchange step cannot be sufficiently suppressed, and if it exceeds the upper limit, not only the processing time will be longer, but also the acid ion exchange will be longer. The resin deteriorates, and the efficiency decreases. From the viewpoint of effect, the reduction amount (consumption amount) of the oxidizing substance per liter of the acidic ion exchange resin should be 0.35 mol equivalent or more and 0.9 mol equivalent or less, particularly 0.4 mol equivalent or more and 0.8 mol equivalent or less. It is preferable to make the contact with. The reduction amount (consumption amount) of the oxidative substance can be grasped by analyzing the concentration of the oxidant substance in the oxidant aqueous solution after the start, but the acidic ion exchange resin and the oxidant aqueous solution actually used in advance can be grasped. The processing time under the actual contact conditions (for example, in the case of the batch processing method, the amount of both, the contact time, and the contact temperature, etc., in the case of the distribution processing method, the amount of both, the space velocity, the contact temperature, etc.) The relationship between the amount of reduction (consumption amount) of the oxidizing substance and the amount of reduction (consumption amount) of the oxidizing substance may be investigated, and the treatment may be carried out for a time that reaches a predetermined consumption amount. The concentration of the oxidizing substance in the aqueous solution of the oxidizing agent is measured by appropriately selecting from analysis methods such as liquid chromatography, gas chromatography, and ion chromatography according to the oxidizing substance, or the concentration of hydrogen peroxide. This can be done using a measuring device specialized for a specific oxidizing substance, such as a meter or an effective chlorine concentration meter. When the oxidizing substance is molecular type hypochlorous acid and / or chlorine dioxide, the consumption amount may be evaluated by the change in the effective chlorine concentration.

[Washing process]
The cleaning step is an optional process in order to prevent the oxidizing agent from being mixed in the product when a substance other than molecular hypochlorous acid is used as the oxidizing agent. Then, the acidic ion exchange resin after the oxidation treatment step is washed with ion exchange water and / or pure water (distilled water). Ion-exchanged water and / or pure water (distilled water) is used in order not to reduce the exchange capacity of the acidic ion exchange resin after the oxidation treatment step, and the ion conductivity of these waters used for cleaning is 3. It is preferable to use water of (mS / m) or less, particularly 2.5 (mS / m) or less, and most preferably water of 2 (mS / m) or less.

The amount and number of washings are not particularly limited, and it is sufficient that the excess oxidizing substances remaining after the oxidation treatment step and the treatment products produced by the reduction of the oxidizing substances are washed away. Methods for confirming whether oxidizing substances and treatment products have been washed away include methods for confirming by analysis such as gas chromatography, liquid chromatography, and ion chromatography, hydrogen peroxide concentration meters, and effective chlorine concentration. A method of confirming by measurement using a meter can be adopted. However, it is not necessary to confirm by these analyzes and measurements every time, and a preliminary experiment may be conducted in advance to confirm the conditions under which sufficient cleaning can be performed, and such conditions may be applied.

2. 2. Ion exchange step In the ion exchange step, the acidic ion exchange resin that has undergone the pretreatment step is brought into contact with a raw material aqueous solution composed of an aqueous solution of a metal salt of hypochlorous acid to exchange ions between metal ions and hydrogen ions. , Produces molecular hypochlorous acid. The ion exchange step is not particularly different from the conventional ion exchange method except that the acid ion exchange resin subjected to the pretreatment step is used, and the raw material aqueous solution, the raw material used liquid and the acidic ion exchange resin are used. As for the contact method, the raw material aqueous solution and the method used in the conventional ion exchange method can be adopted without particular limitation.

That is, as the metal salt of hypochlorous acid contained in the raw material aqueous solution, sodium hypochlorite (NaClO), potassium hypochlorite (KClO), calcium hypochlorite (Ca (ClO) ₂ ), hypochlorous acid Barium chlorite (Ba (ClO) ₂ ) or the like can be used. Further, the raw material aqueous solution may be produced by dissolving these metal salts of hypochlorous acid in water, but in the case of a sodium hypochlorite aqueous solution, it is produced by electrolyzing NaOH and Cl _2. You may. Further, the hypochlorite solution sold as a reagent or the like may be dissolved in water to prepare an aqueous solution, and the hypochlorite aqueous solution sold as a reagent or the like may be used as it is or diluted with water. May be good. As the solvent water or the diluted water, it is preferable to use ion-exchanged water and / or distilled water having a low ion conductivity as used in the washing step. Further, as a method for bringing the acidic ion exchange resin that has undergone the acid ion exchange resin pretreatment step into contact with an aqueous solution of a metal salt of hypochlorous acid, known methods such as a batch method and a distribution method (column method) are particularly suitable. Can be adopted without restrictions.

Hereinafter, suitable conditions and the like in the ion exchange method will be described.
First, the concentration of the hypochlorous acid metal salt aqueous solution in the raw material aqueous solution is usually in the range of 10 (ppm) to 50,000 (ppm) in terms of effective chlorine concentration, but is more suitable depending on the contact method. Is slightly different. That is, in the case of the distribution method (column method), when the concentration of effective chlorine contained in the raw material aqueous solution is very high, for example, 100,000 (ppm), the number of theoretical stages is increased in order to terminate the ion exchange reaction. It is necessary to increase the length, but in that case, the length of the column is increased, and the contact time of the produced HClO is increased accordingly. Even if the easily oxidizable portion of the acidic ion exchange resin is oxidized in the oxidation treatment step, it does not mean that it is not further oxidized, and the speed of oxidation is slowed down, but it is gradually oxidized. Therefore, the yield of molecular-type hypochlorous acid (molar equivalent of molecular-type hypochlorous acid remaining in the solution /) is affected by a certain amount of decomposition that occurs irreversibly when it comes into contact with HClO generated for a long time. (Corresponding to the molar equivalent of metal salt hypochlorous acid) in the raw material aqueous solution tends to be low. Therefore, from the viewpoint of efficient production, the concentration of the raw material aqueous solution in the case of the column method is 10 (ppm) to 50,000 (ppm), particularly 30 (ppm) to 10,000 (ppm). Is preferable, and 50 (ppm) to 5,000 (ppm) is most preferable in consideration of ease of handling and the like.
On the other hand, in the case of the batch method, when the effective chlorine concentration in the raw material aqueous solution is as low as less than 10 (ppm), for example, it is affected by a certain amount of decomposition that inevitably occurs as in the column method. Yields tend to be low. Further, when the effective chlorine concentration is very high, for example, 100,000 (ppm), the frequency of contact with the resin during stirring increases, and the produced HClO decomposes more, so that the yield decreases. Tend. Therefore, from the viewpoint of efficient production, the concentration of the raw material aqueous solution is preferably 500 (ppm) to 50,000 (ppm), particularly preferably 1,000 (ppm) to 50,000 (ppm). Considering ease of handling and the like, it is most preferably 5,000 (ppm) to 30,000 (ppm).

Next, regarding the ratio of the total amount of the acidic ion exchange resin to be brought into contact with the total amount of the raw material aqueous solution (also referred to as the mixing ratio), the total ion exchange equivalent of the acidic ion exchange resin is the metal ion of the metal salt of hypochlorite. It should be equal to or more than the total chemical equivalent of. However, when a weakly acidic ion exchange resin is used among the acidic ion exchange resins, the pH gradually decreases as the ion exchange reaction progresses, and the adsorption and desorption of metal ions reach equilibrium. In addition, metal ions reduce the storage stability of the generated weakly acidic hypochlorous acid water. Therefore, from the viewpoint of storage stability of the generated weakly acidic hypochlorous acid water, the mixing ratio of the ion exchange resin and the aqueous solution of the metal salt of hypochlorous acid when the weakly acidic ion exchange resin is used is weakly acidic. the total ion exchange equivalent of the ion exchange resin _{(E IE),} the total chemical equivalents of the metal ions in the feed aqueous solution _{(E MI)} and the ratio of _(E MI _/ E _IE) is 0.01 to 0.6, especially 0. It is preferably 03 to 0.55, and from the viewpoints of improving storage stability by increasing the purity, reducing the amount of weakly acidic ion exchange resin used, and reducing the manufacturing cost, 0. The amount ratio is preferably 05 to 0.5.
The total ion exchange equivalent ( _EIE ) of the weakly acidic ion exchange resin means the ion exchange capacity when all the exchange groups of the ion exchange resin act, and the unit is the equivalent (eq). For example, when a weakly acidic ion exchange resin 100 (ml) having a total ion exchange capacity of 3.9 (eq / L-resin) is used, the total ion exchange equivalent of the ion exchange resin is _EIE = 0.39 (eq). ). The total chemical equivalent ( _EMI ) of the metal ions in the raw material aqueous solution means the sum of the valences of the metal ions contained in the aqueous solution of the metal salt of hypochlorous acid, which is the raw material, and the unit is equivalent (equivalent). It is indicated by eq). For example, an aqueous solution of a metal salt of hypochlorous acid, a starting material is the NaClONa, if the effective chlorine concentration of 2000 (ppm) capacity is 1 (L), the total chemical equivalents of the metal ion of the raw material aqueous _{solution, E MI} = 0.028 (eq).

The liquid temperature in the ion exchange step, that is, the reaction temperature during the ion exchange reaction is preferably 5 ° C. or higher and 40 ° C. or lower, particularly preferably 10 ° C. or higher and 35 ° C. or lower. If the liquid temperature is within such a range, it is easy to handle and the cost required for temperature control can be kept low, as well as the reduction of metal ions in the produced weakly acidic hypochlorous acid aqueous solution and the molecular hypochlorous acid. The decomposition of chloric acid can be easily suppressed. Specifically, when the liquid temperature is less than 5 ° C., the speed of the ion exchange reaction slows down, the mixing time required for sufficient ion exchange exceeds 120 minutes, and the amount of metal ions is reduced. It becomes difficult to make it. On the other hand, when the temperature exceeds 40 ° C., the decomposition of the aqueous solution of the metal salt of the raw material hypochlorous acid and the produced molecular hypochlorous acid is promoted, and the molecular type hypochlorous acid volatilizes. Is also promoted, so that the effective chlorine concentration of the solution is significantly reduced.

The ion exchange reaction time in the ion exchange step is not particularly limited as long as the metal ions can be sufficiently adsorbed. However, when a weakly acidic ion exchange resin is used in the batch method, if the mixing time exceeds 120 minutes, the generated molecular type hypochlorous acid is gradually decomposed by contact with the ion exchange resin for a long time. To do. HCl (strong acid) generated by decomposition has the effect of desorbing metal ions adsorbed on the weakly acidic ion exchange resin, so the amount of metal ions in the solution increases and storage stability decreases. The mixing time is preferably 120 minutes or less. By note this point, a pH of 7 or less in a batch process, the ratio of the total concentration of the metal ion to the effective chlorine concentration _{(C EC) (C MI)} (C MI / C EC) is 0.5 or less Weakly acidic hypochlorous acid water can be obtained.

The weakly acidic hypochlorous acid water obtained by the method of the present invention is useful as a sterilizing agent or a sterilizing agent, and is used for various sterilizing and sterilizing applications. The usage mode is not particularly limited, and for example, a predetermined space may be sterilized or sterilized by spraying the target aqueous solution with a sprayer, or the target aqueous solution stored in a container such as a pallet is sterilized. Alternatively, tools, instruments, cloths, etc., which are objects to be sterilized, may be immersed to sterilize or sterilize them, or walls, floors, desks, chairs, etc. may be cleaned with a cloth impregnated with the target aqueous solution. You may. The weakly acidic hypochlorous acid aqueous solution obtained by the method of the present invention contains molecular hypochlorous acid having high bactericidal activity and relatively high safety to the human body, and its concentration is stable. It is suitable for simple sterilization of instruments and devices, and can also be used as a mouthwash for sterilization in the oral cavity.

The obtained weakly acidic hypochlorous acid aqueous solution can be used as it is for these purposes. However, considering the transportation cost and storage space when the obtained weakly acidic hypochlorous acid aqueous solution is used as a commercial product, a concentrated undiluted solution consisting of a target aqueous solution having a high effective chlorine concentration can be used by the user when using it. It is preferable to dilute each time with water such as tap water so as to obtain a preferable effective chlorine concentration. As described above, in the method of the present invention, the yield is high when the effective chlorine concentration of the raw material aqueous solution is several thousand to tens of thousands ppm, for example, weakly acidic hypochlorous acid having an effective chlorine concentration of about 10,000 (ppm). Since the chloric acid aqueous solution can be efficiently produced, it is effective as a method for producing a concentrated stock solution when diluted and used as described above. However, if the effective chlorine concentration is too high, care must be taken in handling, and when considering use by the general public who does not have specialized knowledge about chlorine-based bactericides, the effective chlorine concentration in the concentrated stock solution is 100 (ppm). ) Or more and 1,000 (ppm) or less, particularly preferably 300 (ppm) or more and 800 (ppm) or less.

Hereinafter, the present invention will be described with reference to Examples and Comparative Examples in order to specifically explain the present invention, but the present invention is not limited thereto.

First, an oxidizing substance, an aqueous solution of a metal salt of hypochlorous acid, an ion exchange resin, and the like used in Examples and Comparative Examples will be described.
[Oxidizing substance]
-Weakly acidic hypochlorous acid water with an effective chlorine concentration of 7500 (ppm) (metal cation concentration: 1719 mass ppm, manufactured by Tokuyama Dental Co., Ltd.)
-Hydrogen peroxide solution with a concentration of 30.0 to 35.5% (manufactured by Fuji Film Wako Pure Chemical Industries, Ltd.).

[Aqueous solution of hypochlorous acid metal salt]
-NaClO aqueous solution with an effective chlorine concentration of 12.0 (wt%) (Neolax Super: supplier Shimada Shoten).

[Acid ion exchange resin]
<Strong acid ion exchange resin>
-Amberlite IR120B (manufactured by Organo Corporation): Total ion exchange capacity 2.0 (eq / L), hereinafter abbreviated as "IR120B".
<Weakly acidic ion exchange resin>
-Amberlite IRC-76 (manufactured by Organo Corporation): Total ion exchange capacity 3.9 (eq / L), hereinafter abbreviated as "IRC76".
-Diaion WK401 (manufactured by Mitsubishi Chemical Corporation): Total ion exchange capacity 4.4 (eq / L), hereinafter abbreviated as "WK401".
-Duolite C433LF (manufactured by Sumika Chemtex Co., Ltd.): Total ion exchange capacity 4.2 (eq / L), abbreviated as "433LF".

Examples 1-11
(1) Production of weakly acidic hypochlorous acid aqueous solution (1-1) Pretreatment / oxidation treatment step of acidic ion exchange resin (1-1-1) Batch method: Examples 1 to 9
The weakly acidic hypochlorous acid water having an effective chlorine concentration of 7500 ppm and the hydrogen peroxide solution having a concentration of 30.0 to 35.5% are diluted with ion-exchanged water having an ion conductivity of 3 (mS / m) or less, respectively. An aqueous oxidizing agent solution was prepared so that the effective chlorine concentration and the hydrogen peroxide concentration were the concentrations shown in Table 1, respectively.

Next, the acidic ion exchange resin was weighed by volume as shown in Table 2, and the pretreatment agents in the amounts shown in Table 2 were added, respectively, and made of Teflon (registered trademark) fluororesin until the concentration after the reaction shown in Table 2 was reached. Mixing was performed by stirring using a stirring blade so that the acidic ion exchange resin was uniformly dispersed. After the stirring was completed, the resin was allowed to stand until it settled, and the pretreatment agent, which was the supernatant liquid, was removed by decantation.

(1-1-2) Column method: Example 10
The weakly acidic hypochlorous acid water having an effective chlorine concentration of 7500 ppm is diluted with ion-exchanged water having an ion conductivity of 3 (mS / m) or less so that the effective chlorine concentration becomes 822 ppm, and the oxidizing agent aqueous solution (metal cation). Concentration: 188 mass ppm) was prepared. Next, 100 ml of the acidic ion exchange resin was weighed and filled in the column. 3000 ml of the pretreatment agent was flowed at a flow rate of 2 ml / sec.

(1-2) Pretreatment / cleaning step (1-2-1) Batch method: Examples 1 to 9
To the acidic ion exchange resin from which the oxidizing agent aqueous solution has been removed, an amount of ion exchange water having an ion conductivity of 3 (mS / m) or less is added in an amount shown in Table 3, and the acid is acidified using a Teflon fluororesin stirring blade for 10 seconds. The mixture was stirred so that the ion exchange resin was uniformly dispersed. After the stirring was completed, the resin was allowed to stand until it settled, and the cleaning liquid, which was the supernatant liquid, was removed by decantation. The effective chlorine concentration and hydrogen peroxide concentration were measured, and washing was repeated until the concentration became 15 ppm or less.

(1-2-2) Column method: Example 10
2100 ml of ion-exchanged water having an ion conductivity of 3 (mS / m) or less was flowed through a column filled with the acid ion exchange resin after the oxidation treatment at a flow rate of 2 ml / sec. The last 30 ml of the flowed ion-exchanged water was collected, the effective chlorine concentration was measured, and it was confirmed to be 10 ppm.

(1-3) Ion exchange step (1-3-1) Batch method: Examples 1 to 9
The 12% NaClO aqueous solution was diluted with ion-exchanged water having an ion conductivity of 3 (mS / m) or less to adjust the effective chlorine concentration to the effective chlorine concentration shown in Table 4, respectively, to prepare a raw material aqueous solution. Add the amount of the raw material aqueous solution shown in Table 4 to the acidic ion exchange resin after the cleaning step, and use the Teflon fluororesin stirring blade to uniformly disperse the acidic ion exchange resin at the mixing time and temperature shown in Table 4. Was stirred and mixed. During the stirring, the pH of the mixed solution was monitored, and when the pH decreased and the change in pH within 3 minutes became ± 0.3, the stirring was stopped and the stirring time was defined as the mixing time. After the stirring was completed, the mixture was allowed to stand until the resin settled, and the aqueous solution of hypochlorous acid, which was the supernatant, was collected in a polyethylene container through a # 200 filter cloth so as not to allow the resin to enter.

(1-3-2) Column method: Example 10
The 12% NaClO aqueous solution was diluted with ion-exchanged water having an ion conductivity of 3 (mS / m) or less to prepare a raw material aqueous solution so that the effective chlorine concentration was 855 ppm. 1000 ml of the prepared raw material aqueous solution was flowed through a column filled with an acidic ion exchange resin after washing at a flow rate of 2 ml / sec, and the spilled weakly acidic hypochlorous acid water was collected in a polyethylene container.

(2) Evaluation method (2-1) Measurement of effective chlorine concentration A part of the weakly acidic hypochlorous acid aqueous solution produced in (1) is used as a sample solution, and the sample solution is diluted as follows according to the effective chlorine concentration of the raw material solution. A sample for measurement was prepared by diluting with ion-exchanged water at a magnification, and the effective chlorine concentration after dilution was measured with an effective chlorine concentration measurement kit AQ-202 (Shibata Kagaku Co., Ltd.). The effective chlorine concentration of the sample solution was determined from the measurement results and the dilution ratio.
-Effective chlorine concentration of raw material solution 301-900ppm: Dilution ratio 3 times-Effective chlorine concentration of raw material solution 901-3000ppm: Dilution ratio 10 times-Effective chlorine concentration of raw material solution 3001-15000ppm: Dilution ratio 50 times-Effectiveness of raw material solution Chlorine concentration 15001-120,000 ppm: Dilution ratio 500 times.

(2-2) pH measurement Using a pH meter F-55 (Horiba Seisakusho Co., Ltd.), a part of the weakly acidic hypochlorous acid aqueous solution produced in (1) was used as a sample solution, and the pH of the measurement sample solution was used. Was measured.

(2-3) Na ion concentration measurement A part of the weakly acidic hypochlorous acid aqueous solution produced in (1) is used as a sample solution, and the measurement sample solution is ion-exchanged at the following dilution ratio according to the sodium ion concentration of the raw material solution. A sample for measurement was prepared by diluting with water, and the Na ion concentration of the measurement sample was measured using a Na ion meter (Horiba Seisakusho Co., Ltd.). The Na ion concentration of the sample solution was determined from the measurement results and the dilution ratio.
-Na ion concentration of raw material solution 101-500 ppm: dilution ratio 5 times-Na ion concentration of raw material solution 501-5000 ppm: dilution ratio 50 times-Na ion concentration of raw material solution 5001-20000 ppm: dilution ratio 200 times.

(3) Evaluation of the obtained weakly acidic hypochlorous acid water The weakly acidic hypochlorous acid water was produced under the conditions shown in Tables 1 to 4, and the effective chlorine concentration and pH of the produced weakly acidic hypochlorous acid water were obtained. , Na ion concentration, C _MI / C _EC value, and effective chlorine residual rate are shown in Table 5. Here, the effective chlorine residual ratio is a value (%) obtained by dividing the effective chlorine concentration of the produced weakly acidic hypochlorous acid water by the effective chlorine concentration of the raw material aqueous solution, and the closer the value is to 100%, the more the product is being manufactured. It means that there is little effective chlorine that decreases.

Comparative Example 1
Using the acidic ion exchange resin shown in Table 2, the ion exchange step was performed by the batch method (Comparative Example 1-1) and the column method (Comparative Example 1-2) under the conditions shown in Table 4 without performing the pretreatment step. Then, a weakly acidic hypochlorous acid aqueous solution was produced, and the same evaluation as in Examples was performed. The results are shown in Table 5.

Examples 1 to 10 satisfied all the conditions in the production method of the present invention, and the residual effective chlorine concentration was 78% or more. On the other hand, Comparative Example 1 was a case where the pretreatment of the acidic ion exchange resin was not performed, but the residual rate was 71% in the batch method and 29% in the column method.

Claims (4)

Ions that generate molecular hypochlorous acid by contacting an acidic ion exchange resin and a raw material aqueous solution consisting of an aqueous solution of a metal salt of hypochlorous acid to exchange metal ions and hydrogen ions. A method for producing a weakly acidic hypochlorous acid aqueous solution including a replacement step.
Oxidation in which an acidic ion exchange resin and an aqueous oxidizing agent in which an oxidizing substance is dissolved are brought into contact with each other until the oxidizing substance having 0.3 mol equivalent or more and 1.0 mol equivalent or less per liter of the acidic ion exchange resin is reduced. The production method further comprises a pretreatment step including a treatment step, wherein the ion exchange step brings the acidic ion exchange resin that has undergone the pretreatment step into contact with the raw material aqueous solution. The production method according to claim 1, wherein the oxidizing substance is at least one compound selected from the group consisting of molecular hypochlorous acid, chlorine dioxide, hydrogen peroxide, ozone, and organic peroxides. The production method according to claim 1 or 2, wherein the acidic ion exchange resin is a weakly acidic ion exchange resin. The production method according to any one of claims 1 to 3, wherein the pretreatment step further includes a washing step of washing the acidic ion exchange resin oxidized in the oxidation treatment step with ion-exchanged water or pure water.