JP7160292B2 - Chlorine dioxide gas sustained release agent and its package, chlorine dioxide gas sustained release method and chlorine dioxide gas sustained release device - Google Patents

Description

TECHNICAL FIELD The present invention relates to a chlorine dioxide gas sustained release agent and its package, a chlorine dioxide gas sustained release method, and a chlorine dioxide gas sustained release device.

In this specification, inorganic molecular species containing a chlorine atom, such as chlorine dioxide (ClO ₂ ) and chlorine (Cl ₂ ), which are gaseous at normal temperature and pressure, and chlorine oxoacids such as chloric acid (HClO ₃ ). Steam is generically referred to as "chlorine-based gas".

Chlorine dioxide (ClO ₂ ) has a pungent odor similar to chlorine and exists as a gas heavier than air at room temperature. Moreover, since it is a kind of radical, it has a strong oxidizing power. Focusing on this strong oxidizing action and its lower environmental impact than chlorine gas, the paper industry uses chlorine dioxide for bleaching paper pulp. In addition, chlorine dioxide denatures amino acid residues of proteins that constitute viruses, bacteria, and fungi, and is known to have effects such as disinfection, deodorization, and antifungal effects. For this reason, chlorine dioxide is also used for disinfection and sterilization in medical settings and small living spaces. Furthermore, unlike chlorine, chlorine dioxide has the advantage that it does not produce trihalomethanes by reaction with organic matter in water, so it is also used as a disinfectant in swimming pools, water purification plants, and the like.

There are various methods for generating chlorine dioxide, from large-scale generation using a reaction tank to small-scale and simple methods such as opening a small container containing a drug or gelling agent and mixing. It is known and used properly according to the usage amount and usage scene.

As described above, chlorine dioxide gas is generated by various methods in various situations for industrial use, medical use, and more recently, consumer use, and used for bleaching and disinfection purposes. However, since chlorine dioxide gas is a type of chlorine-based gas, there is concern about its adverse effects on living organisms. At present, there is no concentration standard value for chlorine dioxide gas in the environment, and it is the TLV-TWA value for occupational exposure to chlorine dioxide gas announced by ACGIH (American Conference of Professionals on Industrial Hygiene). A certain 0.1 ppm is often used as a reference. Here, the TLV-TWA is the time-weighted average concentration at which the majority of workers are exposed to the concentration for 8 hours a day, 40 hours a week without adverse health effects. In addition, TLV-STEL, which is the permissible limit concentration for short-term exposure, is set at 0.3 ppm. On the other hand, for chlorine (Cl ₂ ), which is known as a toxic gas, TLV-TWA is 0.5 ppm and TLV-STEL is 1.0 ppm. Since the permissible limit concentration is lower than that of chlorine, chlorine dioxide gas can be said to be a highly dangerous gas.

Therefore, when using chlorine dioxide gas, it is most important to control the concentration of the generated gas, and if a large amount of gas is generated in a state where the control of the concentration is insufficient, there is a high possibility of causing problems. In particular, the release of high-concentration gas at the beginning of use (initial high _- concentration release) is also a safety problem. It is necessary to secure time to create an enclosed space to prevent human exposure. For this reason, materials used to generate ClO ₂ are required to be capable of suppressing the initial high-concentration release. Moreover, it is preferable that the material does not damage the skin or the like even if it accidentally comes into contact with the material during handling. Furthermore, it is more preferable that the material has a high density (concentration) of the ClO ₂ source while maintaining the aforementioned properties for weight reduction.

In order to suppress the release of high-concentration ClO ₂ at the beginning of use, for example, in a simple generation method, the raw material solution (solution mainly containing sodium chlorite) is gelled to delay diffusion. A contrivance has been made (Patent Document 1). However, since it involves reaction in a solution state and gelation of the solution, it is necessary to devise ways to prevent leakage of the raw material solution, and since the materials used are in a solution or gel state, there remains a problem in terms of weight reduction. As a material that is not bulky, maintains a sufficient ClO ₂ concentration in a small amount, and releases ClO ₂ slowly, a material in a solid state is conceivable. As a solid material, a porous inorganic material such as silica gel or zeolite to which ClO ₂ is adsorbed is considered (Patent Document 2). However, in the mechanism of desorbing the adsorbed chlorine dioxide, it is difficult to avoid the initial high-concentration release because the ClO ₂ concentration exhibits a simple decay curve with respect to time.

Japanese Unexamined Patent Application Publication No. 2007-1807 JP-A-6-233985

If a solid material that is easy to handle, does not require the addition of acid or complicated operations to generate chlorine dioxide, and is small and lightweight, and releases chlorine dioxide slowly, it will be possible to use it in aqueous systems such as aqueous solutions and hydrogels. It is expected to be applied to sterilization and disinfection applications in various fields including research and medical sites as a method of supplying chlorine dioxide gas in place of methods using chemical reactions. However, the initial high-concentration release of chlorine dioxide is suppressed, and it has the property of being able to continuously release low-concentration chlorine dioxide in the atmosphere at room temperature, and can be handled safely, and yet has a high concentration of chlorine dioxide. Solid materials containing chlorine sources have not been previously reported.

Therefore, in the present invention, by using a layered double hydroxide as a solid material, a chlorine dioxide gas sustained-release agent, its package, a chlorine dioxide gas sustained-release method using the same, and a chlorine dioxide gas sustained-release method are provided. An object is to provide an apparatus.

The present inventor focused on layered double hydroxide (LDH), in which a chlorine dioxide gas source is enclosed between layers, as a candidate for an inorganic solid material capable of releasing chlorine dioxide gas. "Inclusion" is a technical term used for a layered compound to mean that an ion or molecule is sandwiched between layers.

The anionic species chlorate ion (ClO ₃ ⁻ ) can be considered as a source of chlorine dioxide gas. Solid materials containing such anionic species include various chlorates, but they are water-soluble and deleterious, which poses safety problems. Therefore, an anion-exchanging solid material that can contain this anion species in its structure is considered as a candidate for a highly safe material. Among them, layered compounds are considered to be particularly promising, but since many inorganic layered compounds are cation-exchangeable, there are very few applicable solid materials. In layered double hydroxides (LDH), unlike many other inorganic layered compounds, layers composed of metal hydroxides have a positive charge, so that anions can be included between the layers. In addition, it is easy to obtain and synthesize, and is excellent in safety as described later.

However, even if a layered double hydroxide that clathrates chlorate ions is obtained, this does not immediately lead to the generation of chlorine dioxide gas. This is because the oxidation number of chlorine is +5 for chlorate ion (ClO ₃ ⁻ ), while it is +4 for chlorine dioxide (ClO ₂ ). However, it was thought that if a reducing agent were to act on chlorate ions in some way, the oxidation number of chlorine would change and chlorine dioxide gas could be obtained.

Also, N. Iyi et al. , Applied Clay Science 2012, Vol. 65-66, 121-127, when carbonate-type layered double hydroxide (LDH) is mixed with a solid salt, depending on the type of anion, an anion exchange reaction proceeds between solid phases, resulting in LDH. Anions from the solid salt are intercalated between the layers, while anions between the LDH layers are reported to be released into the solid salt outside the LDH. Diffusion between the solid phase and the solid phase is slower than that in solutions, so it is possible to control the concentration and release time of the released gas by using such anion exchange reaction between the solid phase and the solid phase. Conceivable. It has also been pointed out that this solid-solid phase anion exchange reaction is accelerated by increasing the relative humidity in the atmosphere, and can be considered as a response to water vapor in the atmosphere.

The LDH enclosing the anion species of the chlorine dioxide gas source releases the anion species by the solid phase-solid phase anion exchange reaction as described above, and the anion species is a reaction reagent (for example, a reducing agent) external to the LDH. Composite materials can be designed to slowly release chlorine dioxide gas upon contact with a gas containing water vapor. In this case, control of the sustained release concentration and the sustained release time can be expected by adjusting the amount of water vapor contained in the gas in contact with the LDH. If a solid phase-solid phase anion exchange system using layered double hydroxide (LDH) can be formed in this way, it is highly likely that the problems that have been encountered so far can be solved.

Therefore, the inventors synthesized an LDH having chlorate ions (ClO ₃ ⁻ ) between the layers (hereinafter sometimes referred to as “chlorate ion-containing LDH”), and used it as a powdery solid reactant (sugar It was found that chlorine dioxide was generated in the air when it was brought into contact with an acid).

The chlorine dioxide gas sustained-release agent in the present invention contains chlorate ion-containing LDH and a solid reactant, and water vapor contained in the atmosphere promotes a solid-solid anion exchange reaction to release chlorine-based gas. Since it has properties, it is preferably provided as a package that is hermetically housed in a packaging material for the purpose of blocking contact with the atmosphere before use. In this case, in order to suppress gas release in the packaging material, it is more preferable to make the inside of the packaging material a vacuum, a reduced volume state, an inert gas atmosphere, or a dry atmosphere.

Further, the chlorine dioxide gas sustained release agent in the present invention has the property of reacting with water vapor contained in the atmosphere to release chlorine dioxide gas, and the generated chlorine dioxide diffuses naturally. Therefore, it is possible to use a method of simply bringing the sustained-release agent into contact with the atmosphere without requiring a special device for generating chlorine dioxide. However, by combining with a device (manual or electric) that introduces water vapor mixed into the atmosphere or any gas into the chlorine dioxide gas sustained release agent, the generation and diffusion of chlorine dioxide can be further promoted and can be made uniform.

Based on the above, the inventors created the following inventions.
In the layered double hydroxide of the present invention, chlorate ions (ClO ₃ ⁻ ) are included between layers, thereby solving the above problems.
The layered double hydroxide may be represented by the following general formula (1).
Q _x R(OH) _2(x+1) {(ClO ₃ ⁻ ) _g Z _j }.nH ₂ O
... (1)
In formula (1), Q is a divalent metal ion, R is a trivalent metal ion, and Z is an anion other than ClO ₃ ^— . Further, x, g, and j in formula (1) are numbers satisfying 1.8 ≤ x ≤ 4.2, 0.01 ≤ g ≤ 1.0, 0 ≤ j < 1.0, and n is a number that changes with the humidity of the environment.
In the general formula (1), the Q is one or more selected from the group consisting of Mg ²⁺ , Mn ²⁺ , Fe ²⁺ , Co ²⁺ , Ni ²⁺ , Cu ²⁺ , Zn ²⁺ and Ca ²⁺ , and the R is , Al ³⁺ , Ga ³⁺ , Cr ³⁺ , Mn ³⁺ , Fe ³⁺ , Co ³⁺ and Ni ³⁺ .
In the general formula (1), Q may be Mg ²⁺ and R may be Al ³⁺ .
In the general formula (1), Z is OH ⁻ , Cl ⁻ , Br ⁻ , I ⁻ , F ⁻ , NO ₃ ⁻ , ClO ₄ ⁻ , SO ₄ ²⁻ , CO ₃ ²⁻ , acetate anion (CH ₃ COO ⁻ ), propionate anion (CH ₃ CH ₂ COO ⁻ ), lactate anion (CH ₃ —CH(OH)—COO ⁻ ), and isethionate anion (HOC ₂ H ₄ SO ₃ ⁻ ). may be one or more.
A sustained-release agent for slowly releasing chlorine dioxide gas according to the present invention comprises the above-described layered double hydroxide and a solid reactant, thereby solving the above problems.
The layered double hydroxide and the solid reactant may be mixed.
The solid reactant is a reducing solid and may contain a compound composed of an anion and a cation.
The solid reactant includes oxalic acid, ascorbic acid, hydroquinone and salts thereof, salts containing divalent iron ions and/or divalent tin ions, and at least one of zinc, magnesium and reducing sugar, and an ionic solid. mixtures with and at least one substance selected from the group consisting of
The solid reactant may contain at least oxalic acid or a salt thereof.
The solid reactant may satisfy a molar ratio of 0.01 to 500 with respect to the layered double hydroxide.
The method for sustained release of chlorine dioxide gas of the present invention uses any of the sustained release agents described above to solve the above problems.
The method for sustained release of chlorine dioxide gas may include the step of contacting the sustained release agent with a gas containing water vapor.
A package of the present invention includes the aforementioned sustained-release agent and a packaging material for hermetically housing the sustained-release agent, thereby solving the above problems.
The inside of the packaging material may be in a state selected from at least one of the group consisting of a vacuum, an inert gas atmosphere, a dry atmosphere, and a reduced volume state.
An apparatus for slowly releasing chlorine dioxide gas of the present invention comprises an atmospheric gas supply unit for supplying an atmospheric gas, and a chlorine dioxide gas slow release unit for slowly releasing chlorine dioxide gas from the atmospheric gas supplied from the atmospheric gas supply unit. and the chlorine dioxide gas sustained release part comprises the above sustained release agent, thereby solving the above problems.
The atmospheric gas supply unit may supply a gas containing water vapor.
The apparatus for slowly releasing chlorine dioxide gas may further include an impurity removing section for removing impurity components from the chlorine dioxide gas released by the chlorine dioxide slowly releasing section.
The impurity removal section may include an adsorbent that adsorbs chlorine (Cl ₂ ) mixed as an impurity.
The adsorbent may be an organic solid having an amino group.
The impurity removal section may include an adsorbent that adsorbs an acid component mixed as an impurity.
The adsorbent that adsorbs the acid component includes magnesium hydroxide (Mg(OH) ₂ ), calcium hydroxide, sodium hydroxide, sodium hydrogen carbonate, layered double hydroxide in which carbonate ions are enclosed between layers, slaked lime, It may contain at least one material selected from the group consisting of quicklime, soda lime, polyvinylpyridine, an organic compound having an amino group, and silica gel modified with an amino group.

The layered double hydroxide (LDH) according to the present invention includes chlorate ions (ClO ₃ ⁻ ) between layers. The LDH of the present invention gradually releases chlorine dioxide gas by bringing it into contact with a water vapor-containing gas while in contact with an anion-containing reducing solid (solid reactant). Therefore, the LDH of the present invention can function as a chlorine dioxide sustained release agent in combination with a solid reactant. The LDH of the present invention has no deliquescence, is excellent in safety, and is easy to handle. In addition, the chlorine dioxide release mechanism in the chlorine dioxide sustained-release agent using the LDH is different from the release from the adsorbed solid and the reaction, but is due to the diffusion of the components in the atmosphere between the LDH layers and the reaction between the layers. Therefore, the chlorine dioxide sustained-release agent of the present invention is a material whose initial release concentration is suppressed and release continues for a long period of time.

A package in which the chlorine dioxide sustained-release agent is hermetically housed in a packaging material is excellent in long-term storage stability and stability. In addition, the package can release chlorine dioxide slowly only by removing the sustained-release chlorine dioxide from the packaging material and bringing it into contact with a gas containing water vapor. It can provide antiseptic action.

The method for sustained release of chlorine dioxide gas of the present invention uses the sustained release agent described above, and is simple because the sustained release agent only needs to be brought into contact with a gas containing water vapor. In addition, since chemical reactions using dangerous reagents such as acids and reactions in water systems, which are difficult to handle, are not required, the method is excellent in safety and allows downsizing of equipment to be used.

The apparatus for slowly releasing chlorine dioxide gas of the present invention comprises an ambient gas supply section, a chlorine dioxide gas slowly releasing section, and, if necessary, an impurity component removing section. Here, the chlorine dioxide gas sustained release part includes the aforementioned chlorine dioxide sustained release agent according to the present invention. The sustained-release device of the present invention can release chlorine dioxide gas slowly without using a power source such as a battery.

Schematic diagram showing the structure of the layered double hydroxide according to the present invention Schematic diagram showing an example of a synthesis scheme of chlorate ion-containing LDH Schematic diagram showing the mechanism of sustained release of chlorine dioxide gas from a chlorine dioxide gas sustained release agent comprising chlorate ion-containing LDH and a solid reactant Schematic diagram showing a package according to the present invention Schematic diagram showing a sustained-release device for slowly releasing chlorine dioxide gas Schematic diagram showing the apparatus and experimental system used in Example 1 FIG. 2 is a graph showing changes in ClO ₂ concentration over time in Example 1. FIG. FIG. 10 shows changes in ClO ₂ concentration over time in Example 3.

Hereinafter, a layered double hydroxide according to one embodiment of the present invention (hereinafter referred to as "this embodiment"), a chlorine dioxide gas sustained-release agent and its package, and chlorine dioxide gas using the sustained-release agent A sustained release method and a sustained release device will be described with reference to the accompanying drawings.

(Embodiment 1)
As Embodiment 1, a layered double hydroxide (LDH) in which chlorate ions are included between layers and a method for producing the same will be described in detail.

The present inventor has developed a layered double hydroxide in which chlorate ions (ClO ₃ ⁻ ) are clathrated between layers as a new layered double hydroxide.
FIG. 1 is a schematic diagram showing the structure of the layered double hydroxide according to this embodiment.

A layered double hydroxide (LDH) 100 according to this embodiment is composed of layers 110 and anions 120 enclosed between the layers. Layer 110 is a metal hydroxide with a brucite structure. The layered double hydroxide 100 according to the present embodiment contains at least chlorate ions (ClO ₃ ⁻ ) as anions 120, but may contain other anions together with chlorate ions (ClO ₃ ⁻ ). Hereinafter, "chlorate ion-containing LDH" is used as a generic term for layered double hydroxides containing such other anions.

Chlorate ion-containing LDH is represented by the following general formula (1).
Q _x R(OH) _2(x+1) {(ClO ₃ ⁻ ) _g Z _j }.nH ₂ O (1)

In formula (1), Q is a divalent metal ion, R is a trivalent metal ion, and Z is an anion other than chlorate ion. Further, x, g, and j in formula (1) are numbers satisfying 1.8 ≤ x ≤ 4.2, 0.01 ≤ g ≤ 1.0, 0 ≤ j < 1.0, and n is a number that changes with the humidity of the environment. nH ₂ O is called interlayer water and exists between LDH layers. n is illustratively 0 or more and 4 or less. The above range of x (1.8 ≤ x ≤ 4.2) is a general value for crystalline layered double hydroxides. This does not deny the possibility that x may be less than 1.8 or greater than 4.2 in the case of containing a large amount of oxides or in the layered double hydroxide obtained by a special synthesis method.

"Z" in the formula (1) is an anion derived from the raw material or solvent used in the production of the chlorate ion-containing LDH, or the atmosphere during the production or storage of the LDH, specifically OH ^- , Cl ⁻ , Br ⁻ , I ⁻ , F ⁻ , NO ₃ ⁻ , ClO ₄ ⁻ , SO ₄ ²⁻ , CO ₃ ²⁻ , acetate anion (CH ₃ COO ⁻ ), propionate anion (CH ₃ CH ₂ COO ⁻ ), Examples include lactate anion (CH ₃ —CH(OH)—COO ⁻ ) and isethionate anion (HOC ₂ H ₄ SO ₃ ⁻ ).

Q in formula (1) is preferably one or more selected from the group consisting of Mg ²⁺ , Mn ²⁺ , Fe ²⁺ , Co ²⁺ , Ni ²⁺ , Cu ²⁺ , Zn ²⁺ and Ca ²⁺ , and R is Preferably, one or more selected from the group consisting of Al ³⁺ , Ga ³⁺ , Cr ³⁺ , Mn ³⁺ , Fe ³⁺ , Co ³⁺ and Ni ³⁺ , Q is more preferably Mg ²⁺ , R is more Al ³⁺ is preferred.

MgAl-type layered double hydroxides containing Mg and Al as constituent elements, which are most commonly used in layered double hydroxides, are industrially produced and sold at low prices (for example, Kyowa Kagaku Co., Ltd. industrial "synthetic hydrotalcite"), which can be used as a starting material for the synthesis of chlorate ion-containing LDH, as described below.

Regarding the safety of the above-mentioned MgAl-type layered double hydroxide containing Mg and Al as constituent elements, there is no problem even if it adheres to the skin, etc., and it is used for gastrointestinal drugs (antacids) and drug delivery. As a carrier of the system (DDS), research is conducted from a medical point of view and applied to living organisms. Considering these facts, it is expected that LDH having a basic structure of MgAl-type layered double hydroxide and containing chlorate ions between layers is safe even if it adheres to the skin or the like.

As will be described later, the chlorate ion-containing LDH according to this embodiment can function as a chlorine dioxide sustained release agent together with the solid reactant. Like other layered double hydroxides, this chlorate ion-containing LDH is also a solid material that is easy to handle, safe and compact.

When the chlorate ion-containing LDH according to the present embodiment is used in a chlorine dioxide gas sustained-release agent described later, the total amount of chlorine dioxide released from the sustained-release agent is the chlorine occupying the anion sites between the layers in the chlorate ion-containing LDH. It is almost proportional to the ratio of acid ions (value of g in general formula (1)). This ratio can be adjusted, for example, when synthesizing by the ion exchange method described later, by changing the ratio of the number of moles of chlorate ions in the solution to be brought into contact with the LDH to the number of moles of the easily anion-exchangeable LDH. can. Thus, by adjusting the composition of LDH, the sustained release concentration and sustained release time of chlorine dioxide gas can be controlled. The composition of LDH can be adjusted by changing Q, R, Z, x, g, and j in formula (1), and any LDH composition that can be normally conceived by those skilled in the art can be applied.

Next, an exemplary method for synthesizing chlorate ion-containing LDH according to this embodiment will be described.

For the synthesis of chlorate ion-containing LDH according to the present embodiment, three general methods for synthesizing LDH, that is, an ion exchange method, a reconstitution method, and a coprecipitation method, are applied.

In the synthesis, the criterion for the generation of chlorate ion-containing LDH is that at least the diffraction corresponding to the base spacing (interlayer spacing) is detected in the powder X-ray structure analysis, and the desired anion is detected in the composition analysis. It is confirmed that it contains the constituent elements of

[Ion exchange method]
The chlorate ion-containing LDH according to the present embodiment is prepared by preparing a layered double hydroxide in which a monovalent anion other than chlorate ions is included between the layers and a solvent, and adding chlorate ions to the solvent. contacting a layered double hydroxide in which a monovalent anion other than the chlorate ion is included between the layers with the solution; and a solid of chlorate ion-containing LDH produced by the contact It is synthesized by separating the substance from the solution, washing and drying it. The reason why the layered double hydroxide to be brought into contact with the solution is one in which a monovalent anion is included between the layers is that in the layered double hydroxide, the monovalent anion is easily anion-exchanged. This is because it is known that Therefore, if there is a polyvalent anion that can be easily exchanged with an anion, it does not exclude a layered double hydroxide in which it is clathrated.

As a layered double hydroxide (hereinafter referred to as "raw material LDH") in which a monovalent anion other than chlorate ion is included between layers, which is used as a starting material, the anion is desorbed by ion exchange or the like. It is not limited as long as it can be made. One example is represented by the following general formula (1)′.
Q _x R(OH) _2(x+1) {(CO ₃ ²⁻ ) _0.5−a/2 (X) _a }·nH ₂ O
(1)'

In formula (1)′, Q is a divalent metal ion, R is a trivalent metal ion, X is chloride ion (Cl ⁻ ), bromide ion (Br ⁻ ), nitrate ion (NO ₃ ⁻ ), perchlorine acid anion (ClO ₄ ⁻ ), acetate anion (CH ₃ COO ⁻ ), propionate anion (CH ₃ CH ₂ COO ⁻ ), lactate anion (CH ₃ —CH(OH)—COO ⁻ ), and isethionate anion (HOC ₂ H ₄ SO ₃ ⁻ ), and at least one selected from anions with high ion exchange properties. Also, x and a in the formula (1)′ are numbers satisfying 1.8≦x≦4.2 and 0≦a≦1, respectively, and n is a number that varies depending on the humidity of the environment.

The solvent to be used is not limited as long as it can stably dissolve and disperse chlorate ions and supply the anions between the layers of the layered double hydroxide. Examples include deionized water, methanol and ethanol. These solvents are preferably degassed to reduce the concentration of dissolved oxygen and carbon dioxide by using nitrogen gas or rare gas bubbling, ultrasonic waves, heating, or the like. Also in each of the synthesis methods described below, ion-exchanged water and the like used in the reaction are preferably used after degassing.

Incorporating chlorate ions into the solvent is accomplished by adding a substance that dissolves in the solvent to generate the ions. From the viewpoint of improving the quality of the chlorate ion in the solvent and the chlorate ion-containing LDH to be produced and ensuring the constancy of the quality, the above operation is preferably carried out in an inert gas atmosphere. A production method in an inert gas atmosphere includes use of a glove box or the like filled with the gas. In addition, even without using a glove box or the like, it is possible to perform the operation of adding chlorate ions to the solvent under an inert gas atmosphere by a method using a vacuum line or Schlenk tube. Of the operations described below, operations performed under an inert gas atmosphere are not mentioned, but can be performed in a similar manner. The inert gas atmosphere will be described in detail later, but specifically, it is an inert gas atmosphere such as nitrogen or argon that is commonly used in scientific experiments.

Substances added to the solvent are not limited as long as they generate chlorate ions in the solvent, but representative substances include those represented by the following general formula (2).
MH _p (ClO ₃ ) _q ·mH ₂ O (2)

In formula (2), M is an alkali metal or alkaline earth metal. In formula (2), p is 0 or 1, q is 1 or 2, and m is a number that varies depending on the manufacturing method of the reagent and environmental humidity. Examples include sodium chlorate (NaClO ₃ ).

The contact method between the raw material LDH and the solution containing chlorate ions is not particularly limited as long as the two are brought into sufficient contact with each other and chlorate ions are supplied between the layers of the raw material LDH. As an example, pouring the solution into a container containing the raw material LDH, charging the raw material LDH into the container containing the solution, and continuously charging the raw material LDH into a channel through which the solution flows. etc. When the two are brought into contact with each other in a vessel, it is preferable to stir the mixture in the vessel in order to promote the supply of chlorate ions between the layers of the raw material LDH.

As the raw material LDH, the value of a in the general formula (1)′ described above is small (exemplarily in the range of 0≦a≦0.4), that is, carbonate ions (CO ₃ ²⁻ ) occupying the anions between the layers. (hereinafter referred to as "carbonate-type LDH") is used, since carbonate ions are difficult to separate from the layers, the following treatment is performed prior to direct anion exchange to remove carbonate. It is preferable to remove at least part of the ions from the interlayer and convert them to easily exchangeable anions.

The method for releasing carbonate ions from the interlayer is to contact carbonate-type LDH with an acidic compound containing monovalent anions (Cl ⁻ , NO ₃ ⁻ , etc.) in alcohol according to the method described in Japanese Patent No. 5867831. in which the anion is converted into a readily anion-exchangeable LDH in which the anion is intercalated (decarboxylation). The readily anion-exchangeable LDH obtained by the treatment is brought into contact with a solution containing chlorate ions (ion exchange) to exchange anions in a solvent.

FIG. 2 is a schematic diagram showing an example of a synthesis scheme of chlorate ion-containing LDH via easily anion-exchangeable LDH.

The part indicated by (a) in FIG. 2 shows the reaction in which easily anion-exchangeable LDH is produced from carbonate-type LDH, and the part indicated by (b) in FIG. It shows a reaction that produces acid ion-containing LDH. In the figure, as the easily anion-exchangeable LDH, the case of passing through an LDH (Cl-type LDH) in which chloride ions are clathrated between layers is shown. A similar reaction occurs. The readily anion-exchangeable LDH obtained by completely removing (decarboxylating) carbonate ions from carbonate-type LDH is represented by the following general formula (3).
QxR(OH) ₂ ( _{x +1)} X.nH2O (3)

In formula (3), Q is a divalent metal ion, R is a trivalent metal ion, and X is a monovalent anion. Also, x in the formula (3) is a number that satisfies 1.8≦x≦4.2, and n is a number that varies depending on the humidity of the environment.

By contacting the readily anion-exchangeable LDH thus obtained with a solvent containing chlorate ions, anions between the layers are exchanged with chlorate ions as shown in FIG. 2(b), Chlorate ion-containing LDH200 is obtained.

[Reconstruction method]
When LDH containing a large proportion of carbonate ions (CO ₃ ²⁻ ) in the inclusion anions (hereinafter sometimes referred to as “carbonate-type LDH”) is used as the raw material LDH, a method other than the decarboxylation method described above is used. Alternatively, the “reconstruction method” may be employed. This is done by heat-treating the carbonate-type LDH at 400° C. to 600° C. to decarboxylate and destroy the layered structure, followed by a solution containing the anion to be clathrated (chlorate ion in this case). It is a method of contacting and maturing.

By contacting with the solution, the layered structure is reconstructed and at the same time anions in the solution are introduced between the layers. Therefore, by using a solution containing chlorate ions as the contacting solution, chlorate ion-containing LDH can be obtained. will be Aging is an operation to improve the crystallinity by storing the reaction solution for an appropriate period of time while standing still or stirring. In the synthesis of LDH, the aging temperature and time are often increased in order to increase the crystallinity of the product.

[Coprecipitation method]
In addition, as another method for producing chlorate ion-containing LDH, an aqueous solution containing a plurality of types of metal ions forming a cation layer and an aqueous solution containing chlorate ions and adjusted to be alkaline are mixed to form precipitates. - A method of aging the sediment can also be adopted. This is called a "coprecipitation method", and utilizes the phenomenon that the anion component in the alkaline aqueous solution used is included between the layers during the construction of the LDH structure by coprecipitation and aging. The coprecipitation method is a widely used method for synthesizing LDH. Also in the coprecipitation method, the aging temperature and time are often increased in order to increase the crystallinity of the product.

As described above, the synthesis of chlorate ion-containing LDH is mainly applied by three synthesis methods, namely ion exchange method, reconstruction method, and coprecipitation method. Needless to say, a method for synthesizing LDH (for example, a special method for aggregating LDH by adding a solution containing a predetermined anion to swollen or nanosheeted LDH) is applicable.

In any of the above synthesis methods, it is necessary to separate the chlorate ion-containing LDH, which is a solid substance produced in the solution, from the solution. method can be adopted.

The separated solid is washed with a clean solvent, then the solvent is removed and dried. It is preferable that the clean solvent used for washing is preliminarily reduced in concentration of dissolved oxygen and carbon dioxide by the same degassing treatment as in the synthesis.

As a method for drying the solid matter after washing, general methods such as heat drying or reduced pressure/vacuum drying can be adopted. In order to prevent deterioration of the product, reduced pressure/vacuum drying is preferred.

(Embodiment 2)
As Embodiment 2, the chlorine dioxide sustained-release agent containing the chlorate ion-containing LDH described in Embodiment 1 will be described in detail. The present inventors have found that the chlorate ion-containing LDH according to Embodiment 1 and the solid reactant are in contact with each other, and by bringing this into contact with a gas containing water vapor, chlorine dioxide is slowly released at room temperature in the atmosphere. I found letting go.

The chlorine dioxide gas sustained release agent according to the present embodiment essentially requires the above-described chlorate ion-containing LDH and solid reactant. The chlorate ion-containing LDH is the same as described in Embodiment 1, so its description is omitted.

The chlorate ion-containing LDH and the solid reactant are preferably mixed. As a result, the solid phase-solid phase anion exchange reaction described later, that is, the reaction in which the anion derived from the solid salt is inserted between the LDH layers, while the anion between the LDH layers is released outside the layers, is more likely to occur. It can promote the release of chlorine dioxide gas.

The solid reactant is a solid that causes a solid phase-solid phase anion exchange reaction with LDH containing chlorate ions and reduces chlorate ions. There is no particular limitation as long as it is a solid having such properties, but examples thereof include (ionic) compounds composed of an anion and a cation and having reducing properties. More specifically, it is at least one substance selected from the group consisting of oxalic acid, ascorbic acid, hydroquinone, salts thereof, and salts containing divalent iron ions and/or divalent tin ions. Among them, substances containing oxalic acid or salts thereof are preferable. The ionic compound may be carried on a carrier such as silica gel, silica or alumina that does not participate in the reduction reaction.

Alternatively, the solid reactant may be a mixture of a non-ionic (non-ionic) compound having reducing properties and an ionic solid having no reducing properties. Examples of such mixtures include mixtures of non-ionic solids such as metals such as zinc and magnesium and reducing organic compounds such as reducing sugars with non-reducing ionic solids such as magnesium sulfate and sodium sulfate. be done.

Moreover, since the chlorine dioxide sustained-release agent according to the present embodiment is used in the atmosphere, the solid reactant is preferably non-deliquescent. Additionally, solid reactants are preferably in powder form. Such solid reactants may be supported on inorganic solid materials such as zeolites, silica gels, activated carbon, and the like.

Although the amount of the solid reactant is not particularly limited, it preferably satisfies a molar ratio of 0.01 to 500 with respect to chlorate ion-containing LDH.

The chlorine dioxide gas sustained-release agent according to the present embodiment contains the above-described chlorate ion-containing LDH and solid reactant as essential components. It may contain various additives such as rate adjusting components, diluents, surface coating agents, dehydrating agents, decarbonizing agents, oxygen scavengers, and components that react with chlorine dioxide gas to produce other compounds. .

The chlorine dioxide gas sustained release agent according to this embodiment does not interfere with physical processing such as wrapping with a cover tape that restricts ventilation. This makes it possible to suppress the initial concentration and improve the sustained release property.

The chlorine dioxide gas sustained release agent according to the present embodiment develops chlorine dioxide gas sustained release properties by direct contact between the chlorate ion-containing LDH and the solid reactant described above. Contacting is preferably performed just prior to the sustained release of gas. From this point of view, the chlorate ion-containing LDH and the solid reactant are separated and stored in a closed container, and the atmosphere in the closed container is a reduced volume state, a vacuum, an inert gas atmosphere, or a dry atmosphere. may be Separation means that the chlorate ion-containing LDH and the adsorbent are accommodated in the same container with a partition or the like therebetween. Thus, the chlorine dioxide gas sustained-release agent according to the present embodiment includes one in which the chlorate ion-containing LDH and the solid reactant are provided in a state before contact.

The method of contacting the chlorate ion-containing LDH and the solid reactant includes a method of bringing them into contact by removing a movable partition provided between them, and a method of mechanically pulverizing and mixing them with a small manual mill. , any contact method that can be normally conceived by those skilled in the art can be selected.

Here, release of chlorine dioxide gas herein means that an increase in chlorine dioxide concentration is detected by some qualitative or quantitative method, and release of chlorine dioxide gas means that the release occurs. Nature. A material using such a releasing material or a composite material thereof is referred to as a chlorine dioxide gas releasing agent. On the other hand, the sustained release property of chlorine dioxide gas in the present specification refers to the property of continuously detecting chlorine dioxide gas at a concentration of 1/100 or more of the maximum value for 30 minutes or more in the release experiment described later. Sustained-release agents refer to those using a material having the sustained-release property or a composite material thereof.

In addition, the latency in the present specification means the time until the released chlorine dioxide gas concentration reaches 1/10 of the maximum concentration after the chlorine dioxide gas releasing agent is placed under conditions for releasing chlorine dioxide gas. means If the latency is 10 minutes or more, it can be said that the latency is sufficient.

FIG. 3 is a schematic diagram showing a mechanism of sustained release of chlorine dioxide gas from a chlorine dioxide gas sustained release agent comprising chlorate ion-containing LDH and a solid reactant.

Referring to FIG. 3, a chlorine dioxide gas sustained release agent 300 comprising a chlorate ion-containing LDH 310 and a solid reactant 320 in direct contact therewith will be described. FIG. 3 shows, as an example, the case where the solid reactant 320 is oxalic acid (C ₂ O ₄ H ₂ ). The figure shows the concept of the reaction, and the number of molecules in the figure does not guarantee strictness.

As described above, when LDH comes into contact with a solid salt, a solid-solid anion exchange reaction proceeds and anions derived from the solid salt are inserted between the LDH layers, while the anions between the LDH layers are transferred to the outer solid salt. There have been reports of the release of Anion exchange between "solid phases" also involves diffusion of anions in the LDH layer, so anion exchange proceeds over a certain period of time, which is useful for realizing sustained release of chlorine dioxide gas. It is believed that there is. There is no known precedent in which the anion exchange reaction between "solid phase-solid phase" in chlorate ion-containing LDH310 as shown in FIG. 3 is applied to sustained gas release.

When the chlorate ion-containing LDH 310 is brought into contact with a gas containing water vapor while being in contact with oxalic acid, which is the solid reactant 320, oxalate ions and ClO ₃ ⁻ undergo anion exchange between the “solid phase and solid phase”. Then, ClO ₃ ⁻ that appears in the solid phase of oxalic acid is reduced by oxalic acid to become chlorine dioxide, which is released as gas. Here, oxalic acid is a solid salt having an oxalate anion (C ₂ O ₄ ²⁻ ) and also acts as a reducing agent. Such a composite material containing chlorate ion-containing LDH and a solid reactant (eg, oxalic acid) functions as a chlorine dioxide sustained release agent.

At this time, by controlling the relative humidity in the gas containing water vapor, the timing of starting the sustained release of the chlorine dioxide gas and the rate of progress of the sustained release can be controlled.

The reaction of this slow release of chlorine dioxide gas is represented by a reaction formula as follows.
[2ClO ₃ ⁻ ] _LDH + 2H ₂ C ₂ O ₄ →[C ₂ O ₄ ²⁻ ] _LDH + 2CO ₂
+2H ₂ O+2ClO ₂ ↑ (4)
Here, [ ] _LDH indicates an anion existing between LDH layers.

LDH containing chlorate ions is a conjugate base of chloric acid, in which the clathrate chlorate ions are a strong acid. Therefore, in terms of equilibrium, chloric acid and chlorine-based gas are generated by reaction with water vapor and carbon dioxide in the gas. never do. Therefore, it is stable even in the atmosphere and can be stored. Due to the above-mentioned anion exchange reaction between the solid phase and the solid phase, the chlorate ions contained in the chlorate ion-containing LDH diffuse and come into contact with the solid reactant outside the LDH. Reduced to chlorine gas.

Water vapor in the gas acts as a diffusion promoter and proton donor for anions. Here, oxalic acid, which is the aforementioned solid reactant, has protons in its molecule and also acts as a proton donor. Therefore, in the chlorine dioxide sustained-release agent using oxalic acid as a solid reactant, water vapor is a factor that mainly affects anion diffusion. On the other hand, when a salt such as an oxalate is used as the solid reactant, water vapor acts as a proton donor as well as a diffusion promoter for anions.

(Embodiment 3)
Since the chlorine dioxide sustained-release agent according to the present embodiment utilizes the principle of reacting with the water vapor component in the air, it is preferably in the shape of a package to avoid contact with the air until use. Below, as Embodiment 3, a package using the chlorine dioxide gas-based sustained-release agent according to Embodiment 2 will be described.

FIG. 4 is a schematic diagram showing a package according to this embodiment.

In the package 400 according to the present embodiment, the chlorate ion-containing LDH 410 and the solid reactant 420, which constitute the chlorine dioxide gas sustained release agent, are separated by a partition 430 and hermetically housed in a package 440. be. Here, the chlorine dioxide gas sustained release agents (410 and 420) are the chlorine dioxide gas sustained release agents described in the second embodiment. The chlorine dioxide gas sustained release agent may be used as it is, or may be used after being processed or covered by wrapping or the like.

As described in detail in Embodiment 2, the chlorine dioxide gas sustained-release agent according to this embodiment releases chlorine dioxide gas slowly by reacting with water vapor in the atmosphere. Thus, contact with atmospheric water vapor can be avoided until immediately before use. Moreover, by using the chlorine dioxide gas sustained-release agent as the package 400, it is possible to prevent the solid reactant 420, which is a component of the package 400, from deteriorating due to contact with carbon dioxide, water, and oxygen in the atmosphere.

The material of the packaging material 440 should not react with each component of the chlorine dioxide gas sustained-release agent, have gas barrier properties to prevent permeation of carbon dioxide, water, oxygen, etc., and should not be destroyed by normal storage methods. is not limited. Examples thereof include a sealed bag in which the periphery of an aluminum laminate film is fusion-sealed, a glass container sealed with a packaging material, and a polyethylene container. In FIG. 4, the packaging material 440 is a sealed bag (with the opening already fused). It is not limited as long as it has a gas barrier property that can hold for a predetermined period of time.

As described in Embodiment 2, the chlorine dioxide gas sustained release agent comprises the chlorate ion-containing LDH 410 and the solid reactant 420. A package is preferred. FIG. 4 shows that the chlorate ion-containing LDH 410 and the solid reactant 420 are housed in the same packaging material 440. If necessary, the chlorate ion-containing LDH 410 and the solid reactant 420 are It goes without saying that a method of storing in a separate packaging material and opening and contacting it before use is also possible.

In the packaging body 400, the inside of the packaging material 440 is in a state selected from at least one of the group consisting of a vacuum, an inert gas atmosphere, a dry atmosphere containing no water, and a reduced solubility state. It is preferable in terms of improving the storage stability of.

In this specification, the term "reduced volume" refers to the volume of a flexible packaging material that is reduced to half of the volume when fully filled by discharging gas from the packaging material using a suction device or a decompression device. means a reduced state of: On the other hand, "vacuum" means a state of reduced pressure from atmospheric pressure (lower pressure than atmospheric pressure) for non-flexible packaging materials. The term "inert gas atmosphere" means an atmosphere containing less oxygen gas and carbon dioxide gas than the air, and the term "dry atmosphere" means an atmosphere with a relative humidity of 50% or less. Examples of the inert gas atmosphere include a nitrogen gas atmosphere having a higher nitrogen gas content than air, a rare gas atmosphere having a higher rare gas content than air, and the like.

An exemplary method of manufacturing the package 400 will now be described.
For example, in an inert gas atmosphere, the chlorate ion-containing LDH 410 as a chlorine dioxide gas sustained release agent and the solid reactant 420 are placed in a packaging material 440 having an opening through a partition 430, and the opening is closed by fusion bonding or the like. A method of forming the package 400 by a sealing method can be adopted. Alternatively, for example, a chlorine dioxide gas sustained release agent is placed in a packaging material 440 having an opening, the packaging material 440 is decompressed to create a vacuum state, and then the opening is sealed by fusion bonding or the like. can also be employed. It should be noted that the method of creating a vacuum, an inert gas atmosphere, or a dry atmosphere in the packaging material 440 is not limited to this, and any method conceivable by those skilled in the art can be adopted.

The package 400 obtained in this way can be stored in the atmosphere at normal room temperature, but this does not preclude storage in a refrigerator or freezer.

(Embodiment 4)
As Embodiment 4, a method for gradually releasing chlorine dioxide gas using the chlorine dioxide gas sustained release agent according to Embodiment 2 or the package according to Embodiment 3 will be described.

A chlorine dioxide gas sustained release method using a chlorine dioxide gas sustained release agent includes the step of contacting the sustained release agent with a gas containing water vapor. This is for causing a "solid-solid anion exchange reaction" between the solid reactant and chlorate ion-containing LDH via the water vapor component in the atmosphere, as described above.

Since the anion exchange reaction between solid phases involves the diffusion of ions and gas molecules within the layer, chlorine dioxide gas can be continuously released over a long period of time.

Here, when the chlorine dioxide gas sustained release agent housed in the package 400 according to Embodiment 3 is employed, the package 400 is opened immediately before the sustained release is started, and the separated chlorine gas is released. After the LDH containing acid ions and the solid reactant are brought into contact with each other, they may be brought into contact with a gas containing water vapor.

When the chlorate ion-containing LDH and the solid reactant are mixed prior to the step of contacting the chlorine dioxide gas sustained-release agent with the gas containing water vapor, the chlorate ion-containing LDH and the solid reactant are mixed in the packaging material. Any mixing method that can be imagined by those skilled in the art, such as removing the partition between them and shaking them, mechanically stirring the two after opening the packaging material, pulverizing and mixing with a device such as a pepper mill, etc. is applicable.

Any method can be applied to the contact of the chlorine dioxide gas sustained-release agent with the gas containing water vapor as long as contact between the two can be guaranteed. As an example, a chlorine dioxide gas sustained release agent is placed in a glass vial bottle or a glass cylinder, and water vapor is generated by a manual air pump such as a double ball rubber, an air pump combined with a cylinder, a humidifier, etc. A method of supplying a gas containing

Following the step of contacting the gas containing water vapor with the chlorine dioxide gas sustained release agent, a step of contacting the generated gas with an adsorption/removal agent or the like (hereinafter referred to as an adsorbent) to adsorb impurities may be performed.

In the method for generating chlorine dioxide gas according to the present embodiment, side reactions occur, and impurity components (derived from the chlorate used for synthesis) taken in between the layers of the chlorate ion-containing LDH are released, It is assumed that unintended impurities such as Cl ₂ may be mixed. Even in this case, impurity components can be removed by bringing the generated gas into contact with the adsorbent.

Adsorbents include glycine, which is an amine compound that reacts with chlorine, GABA (γ-aminobutyric acid), organic solid materials having amino groups such as taurine, and layered double hydroxides and chlorites containing chlorite ions. Inorganic solid materials may also be used. A carrier such as silica gel supported with a drug that acts as an adsorbent may also be used. For example, if the impurity component is _Cl2 , it can be removed by passing it through powdered glycine _{( H2NCH2COOH} ). If the adsorbent is a solid material, it preferably has low hygroscopicity, no deliquescence and no volatility. The above-mentioned "layered double hydroxide containing chlorite ions" is obtained, for example, by adding chlorite ions instead of the solution containing chlorate ions in the method for producing chlorate ion-containing LDH described above. can be manufactured using the above solution.

After the package 400 described in Embodiment 3 is opened and the chlorate ion-containing LDH and the solid reactant are brought into contact with each other to form a chlorine dioxide gas sustained release agent, the adsorbent is further used as a chlorine dioxide gas sustained release agent. may be placed in the latter stage to remove the impurity component.

(Embodiment 5)
Since the chlorine dioxide gas sustained-release agent according to the present embodiment generates chlorine dioxide upon contact with a gas containing water vapor, the method of unsealing the package 400 and allowing it to stand still, as exemplified in the fourth embodiment. Chlorine dioxide gradually diffuses into the atmosphere even in the is preferred.

Therefore, as Embodiment 5, an apparatus for slowly releasing chlorine dioxide gas using the chlorine dioxide gas sustained release agent according to Embodiment 2 will be described.
FIG. 5 is a schematic diagram showing a sustained release device for slowly releasing chlorine dioxide gas.

The sustained release device 500 according to the present embodiment includes at least an atmospheric gas supply unit 510 that supplies an atmospheric gas, and a chlorine dioxide gas sustained release unit that slowly releases chlorine dioxide gas from the atmospheric gas supplied from the atmospheric gas supply unit 510. 520. The sustained release device 500 shown in FIG. 5 further includes an impurity removal section 530 for removing impurity components that may be contained in the chlorine dioxide gas sustainedly released from the chlorine dioxide gas sustained release section 520. This is It is used as needed.

The ambient gas supply unit 510 can employ any means capable of supplying a gas containing water vapor. Illustrative examples include a manual air pump such as a twin ball rubber, a cylinder, and the like. If there is a power supply such as a battery, an electric air pump can also be used, and when an air pump is employed, it may be combined with a humidifier or the like. The atmospheric gas supply unit 510 may supply carbon dioxide in addition to the gas containing water vapor.

Chlorine dioxide gas sustained release unit 520 includes at least the chlorine dioxide gas sustained release agent according to the second embodiment. The chlorine dioxide gas sustained release section 520 is connected with a tube or the like so that the atmospheric gas supplied from the atmospheric gas supply section 510 is in contact with the chlorine dioxide gas sustained release agent. Chlorine dioxide gas sustained release unit 520 may be configured such that the package according to Embodiment 3 is opened immediately before the sustained release starts, and the taken out chlorine dioxide gas sustained release agent is placed therein.

Impurity removal section 530 has arbitrary means for adsorbing and removing unnecessary components (impurity components) from the gas generated in chlorine dioxide gas sustained release section 520 . Such means include, for example, an adsorbent packed in a column or the like.

Chlorine and acid components can be considered as impurity components. Since the chlorine adsorbent is as described above, the description is omitted here. If there is an acid component mixed, magnesium hydroxide (Mg(OH) ₂ ), calcium hydroxide, sodium hydroxide, sodium hydrogen carbonate, carbonate-type LDH, slaked lime, quicklime, soda lime, polyvinylpyridine, amino group An adsorbent containing at least one material selected from the group consisting of an organic compound having an amino group and silica gel modified with an amino group is used.

The operation of the chlorine dioxide gas sustained release device 500 according to this embodiment will be described.
Atmospheric gas supply unit 510 supplies gas containing water vapor to chlorine dioxide gas slow release unit 520 . In the chlorine dioxide gas sustained release section 520, a “solid phase-solid phase anion exchange reaction” occurs between the chlorate ion-containing LDH and the solid reactant via the supplied water vapor component, and chloric acid is released. The reduction of chloric acid with the reducing agent results in the release of chlorine dioxide gas.

In the impurity removal section 530, the gas is supplied from the chlorine dioxide gas sustained release section 520, and chlorine and acid components, which are impurity components in the gas, are removed by the adsorbent. As a result, purified chlorine dioxide gas is gradually released from the sustained release device 500 .

EXAMPLES The present invention will now be described more specifically based on examples. However, these examples are shown as an aid for facilitating understanding of the present invention, and are not intended to limit the present invention in any way.

[Method for measuring concentration of chlorine-based gas component]
Prior to the examples, a method for measuring the concentration of slowly released chlorine dioxide gas will be described.

When measuring changes in the chlorine dioxide gas concentration over time, it is convenient to use a detector tube or gas sensor. However, since the detector tube and gas sensor also react to chlorine (Cl ₂ ), which may be mixed as an impurity component, it is necessary to determine whether the released gas is chlorine dioxide, chlorine, or a mixture thereof. It cannot be separated and measured immediately. Therefore, usually, it is necessary to collect the gas using a collection liquid and perform a time-consuming and time-consuming measurement such as performing an analysis by ion chromatography, which makes rapid measurement difficult.

This problem can be solved if a method of pretreating the released gas with an adsorbent that only absorbs chlorine can be applied. In other words, we thought that it would be possible to separate and measure the concentration of chlorine dioxide only by installing an appropriate adsorbent as an adsorption tube in front of the detector tube or gas sensor.

However, such an adsorbent has not been known so far, much less its application has been reported. In the DPD (diethyl paraphenylenediamine) method used for water quality testing, the present inventor added glycine to the test water in advance when analyzing chlorine dioxide in the test water, and converted the contained chlorine into bound chlorine. By changing the concentration, it becomes possible to analyze only chlorine dioxide, excluding chlorine. . Therefore, in order to confirm this, the following experiment was conducted.

First, a glass tube (5.6 mmφ in inner diameter) was filled with about 1 cm of powdered glycine (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., reagent special grade), and a column (hereinafter referred to as a glycine tube) was pressed on both sides with absorbent cotton. and connected to the gas inlet side of the detector tube while keeping airtightness. Next, 7 mg of sodium hypochlorite pentahydrate (NaClO.5H ₂ O, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., reagent first grade) was placed in a 13.5 mL glass bottle, and nitrogen with a relative humidity of 50% was added at a flow rate of 100 mL. /min and the exiting gas was collected with a Tedlar® bag. Then, this gas was introduced into two types of detector tubes, a normal detector tube and a detector tube with a glycine tube added to the gas introduction side, and measured.

The detector tube used was for Cl ₂ (manufactured by Gastech, 8La) for measuring chlorine (Cl ₂ ) concentration. It also reacts with chlorine. As a result of the measurement, the concentration of Cl ₂ in the collected gas was 1.1 ppm when measured only with the detector tube (8La), but was not detected at all with the glycine tube. It was determined that this was because chlorine chemically adsorbed to glycine and the concentration was below the detection limit (0.05 ppm). Furthermore, even when the Cl ₂ concentration in the gas was increased to 4.0 ppm, no Cl ₂ was detected in the one equipped with the glycine tube. From this result, it can be seen that chlorine gas with a concentration of up to about 4 ppm can be adsorbed and removed by the glycine tube with the above specifications.

On the other hand, a gas containing ClO ₂ was prepared and analyzed in a similar manner to examine the effect of the glycine tube.

The gas containing ClO ₂ was prepared by adding 19 mg of oxalic acid (manufactured by Fuji Film Wako Pure Chemical Industries, Ltd., reagent special grade) to 15 mg of potassium chlorate (KClO ₃ , manufactured by Fuji Film Wako Pure Chemical Industries, Ltd., reagent special grade), and adding distilled water. A drop of the mixture was placed on a hotplate heated to 70° C. and flushed with nitrogen at 50% relative humidity at a flow rate of 100 mL/min, and the emerging gas was bubbled further into the NaClO ₂ solution (2 g/15 mL). After passing through, it was obtained by collecting with a Tedlar bag. This method is known as a method of obtaining highly pure ClO2, and bubbling with _NaClO2 solution is for converting _Cl2 that may be produced by _side reactions into _ClO2 .

Measurement was performed by introducing the obtained gas twice in an amount of 100 mL into each of two types of detector tubes, a normal detector tube and a detector tube with a glycine tube added to the gas inlet side. The detector tube used this time was for ClO ₂ (23M, manufactured by Gastech), and the component was 3,3′,5,5′-tetramethylbenzidine, the same as the detector tube (8La) mentioned above. , also reacts with chlorine.

As a result, the concentration of the gas was 1.3 ppm for the tube-only measurement and 1.1 ppm for the one with glycine. The value was about 15% lower when using the glycine tube, but this is because _ClO2 was physically adsorbed on the surface of the glycine powder, or because _ClO2 was dissolved in the water adsorbed on the surface of the glycine powder. Seem.

From the above, it can be seen that the actual concentration of ClO ₂ can be estimated by dividing the measured value by the correction value of 0.85 with the adsorption tube of the above specifications. Thus, the use of the glycine tube made it possible to measure ClO ₂ separately from Cl ₂ . In this experiment, nitrogen with a relative humidity of 50% was used as the gas to flow when obtaining the gas containing ClO ₂ , but similar results were obtained when air with a relative humidity of 50% was used. Got. Measurements using the method of flowing air containing water vapor were carried out in Example 2.

(Example 1)
As the carbonate-type LDH, the divalent metal ions are Mg ions and the trivalent metal ions are Al ions, and are represented by the general formula Mg ₃ Al(OH) ₈ (CO ₃ ²⁻ ) _0.5 ·2H ₂ O. A commercially available carbonate-type layered double hydroxide (DHT-6, manufactured by Kyowa Chemical Industry Co., Ltd., particle size distribution: about 0.1 to 1 μm, Mg/Al molar ratio: 2.99 (±0.06)) was used. Hereinafter, this LDH will be referred to as CO ₃ ^2- MgAl-LDH3.

First, by the method described in Japanese Patent No. 5867831, carbonate-type LDH was converted to Cl-type LDH. The synthesis procedure will be described in detail below. 250 mg of CO ₃ ^2- MgAl-LDH3 was weighed and placed in a three-necked flask, and 37.5 mL of ethanol was added. While stirring this suspension with a magnetic stirrer under nitrogen flow (500 mL/min), 12.5 mL of hydrochloric alcohol solution (0.1 mol/L) was added dropwise, and the mixture was stirred at 25°C for 1 hour. I reacted while doing it. After that, it was filtered using a membrane filter with a pore size of 0.2 μm in a nitrogen flow, and the filtrate (residue) was thoroughly washed with methanol. The filtered material (residue) was immediately evacuated together with the filter, dried under vacuum for 1 hour or more, and then scraped from the filter to obtain a white powder.

When the infrared absorption spectrum (FTIR spectrum) of the obtained white powder was measured using a Fourier transform infrared spectrophotometer (Perkin ^- Elmer Spectrum One, ATR attachment), carbonate ion (CO ₃ ^{2 −} ) showed no absorption. Further, a profile similar to that described in Japanese Patent No. 5867831 was obtained by measurement with a powder X-ray diffractometer (Rigaku, RINT2200). Furthermore, analysis by SEM-EDS (JEOL, JSM6010LA) showed that the ratio of Cl, Mg, and Al was almost the same as the expected value (1:3:1). Based on these facts, it was determined that Cl 2 ^-type LDH was obtained by replacing carbonate ions with chloride ions. Hereinafter, this LDH will be referred to as Cl ^- MgAl-LDH3.

Next, a chlorate ion-containing LDH was produced from Cl ^- MgAl-LDH3. In a glove box with a nitrogen atmosphere, 25 mL of degassed ion-exchanged water was added to 980 mg of KClO ₃ (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., reagent special grade) and dissolved to prepare a KClO ₃ solution. The degassed ion-exchanged water was obtained by boiling the ion-exchanged water and then cooling it to room temperature while bubbling nitrogen gas. are using.

In a glove box in a nitrogen atmosphere, the above KClO ₃ solution was added to 122.8 mg of Cl ⁻ MgAl-LDH3 in a 40 mL glass vial, sealed, shaken well, and dispersed by ultrasonic waves. After storing in a nitrogen atmosphere for 2 days with the glass vial sealed, it was filtered using a membrane filter with a pore size of 0.2 μm in the glove box described above, and the filtered material (residue) was removed with degassed ion-exchanged water. washed. After that, the membrane filter with the sample attached is folded in half with the side with the filter material (residue) attached inside, and the filter is decompressed and dried under vacuum for 60 minutes or more, then scraped from the membrane filter, A white powdery sample was obtained.

FTIR spectral measurements were performed on the white powdery sample. As a result, absorption due to chlorate ions (ClO ₃ ⁻ ) at 925 and 970 cm ⁻¹ was observed. However, from the FTIR profile, it was also confirmed that several percent of CO ₃ ²⁻ presumed to have been taken in during operations such as ion exchange existed. Also, the X-ray diffraction pattern of the white powdery sample was characteristic of layered double hydroxide. Furthermore, in SEM-EDS analysis, the molar ratio of Mg:Al:Cl was 3.1:1.0:0.97, which was in good agreement with the composition of ClO ₃ ^-LDH3 (chlorate ion-containing LDH). . Combined with the FTIR results, the Cl component is believed to be derived from ClO ₃ ^— . Therefore, it was determined that anion exchange proceeded without destroying the layer structure, and ClO ₃ ⁻ LDH3 (chlorate ion-containing LDH) satisfying the general formula (1) was produced.

Next, a predetermined amount of oxalic acid (C ₂ O ₄ H ₂ ) was added to and mixed with the obtained LDH containing chlorate ions, and a ClO ₂ release experiment was performed using the apparatus shown in FIG.

6 is a schematic diagram showing the apparatus and experimental system used in Example 1. FIG.

A powdery sample (20 mg) of chlorate ion-containing LDH was placed in a glass container 660 , oxalic acid (30 mg) was added thereto, and the mixture was thoroughly mixed by grinding with a spatula to obtain a mixed sample 650 . Oxalic acid in the mixed sample had a molar ratio of 5.9 to ClO ₃ ^-LDH3 . As shown in FIG. 6, a glass container 660 containing a mixed sample 650 is set with a septum having two air inlet tubes 670 and an air outlet tube 680 .

Next, as shown in FIG. 6, the air sent from the compressor (or air pump) 610 is introduced into the relative humidity adjustment device 620 to adjust the relative humidity, and the flow rate is adjusted by the valve 630 while being monitored by the flow meter 640. was adjusted to a flow rate of 100 mL/min.

Next, the gas discharged from the discharge tube 680 is introduced into a chlorine dioxide sensor (ToxiRAE Pro manufactured by RAE System (detection range 0.0-1.0 ppm, resolution 0.03 ppm)) as the concentration sensor 690. Chlorine dioxide concentrations were measured. The measurement interval was adjusted between every 5 minutes and 10 minutes, and changes in concentration over time were measured. The relative humidity of the air was 50% relative humidity for the first hour, then increased to 80-90%. The results are shown in FIG.

FIG. 7 is a graph showing changes in ClO ₂ concentration over time in Example 1. FIG.

FIG. 7(a) shows the time course of the ClO ₂ concentration from the start of the measurement to the end of the measurement (120 hours). According to FIG. 7(a), it was found that the mixed sample 650 satisfies the sustained release properties defined herein. FIG. 7(b) is an enlarged view of the results from the start of measurement to 12 hours in FIG. 7(a). According to FIG. 7(b), release of chlorine dioxide was not detected immediately after coming into contact with air, but was detected by the chlorine dioxide monitor after 2 hours and 25 minutes. The release continued for several days, and the time to reach 1/10 (0.039 ppm) of the maximum concentration (0.39 ppm), that is, the latency was about 2 hours and 40 minutes.

As described above, the chlorate ion-containing LDH obtained in Example 1 is brought into contact with a gas containing carbon dioxide and water vapor together with a solid reactant (oxalic acid in this case), thereby gradually releasing chlorine dioxide. It was shown to function as an agent. It was also found to function as a sustained-release agent with sufficient latency. Furthermore, the experimental system shown in FIG. 6 demonstrated that the sustained release device described with reference to FIG. 5 functions effectively.

(Example 2)
A chlorine dioxide release experiment was conducted on a mixed sample of chlorate ion-containing LDH and oxalic acid obtained in the same manner as in Example 1, and the ratio of ClO ₂ components in the resulting gas was investigated. In the apparatus shown in FIG. 6, the discharged gas is collected by a Tedlar bag installed instead of the chlorine dioxide sensor 690, the chlorine dioxide concentration in this gas is measured with a detector tube, and an attempt is made to separate it from chlorine. rice field.

A glass vessel 660 containing a mixed sample 650 was capped with a septum having an inlet tube 670 and an outlet tube 680, and air conditioned at 90% relative humidity was passed through it. After confirming with a gas monitor that ₂ was contained, exhaust gas was collected using a Tedlar bag at a flow rate of 20 mL/min for 20 minutes.

This gas was measured using a detector tube for ClO ₂ (manufactured by Gastech, 23L). This detector tube contains 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) as a coloring component and reacts to Cl ₂ as well. In addition to the measurement using this detector tube, measurements were also performed using a detector tube equipped with a glycine tube on the gas inlet side. As a result of introducing 100 mL of the exhaust gas into each of the detection tubes once, the concentration of the gas was 0.55 ppm when measured only by the detection tube, and 0.45 ppm when the glycine tube was provided. Indicated. The latter is 0.53 ppm when corrected by dividing by the correction factor of 0.85 for the glycine tube, which is almost equal to the value measured by the detector tube alone.

From the above results, it was found that the released gas contained almost no Cl ₂ and was mainly composed of ClO ₂ .

(Example 3)
An example in which nitrogen was used as the atmospheric gas in the release experiment is shown.

Chlorate ion-containing LDH synthesized in the same manner as in Example 1 was used. A mixed sample of chlorate ion-containing LDH (36 mg) and oxalic acid (54 mg) was subjected to a ClO ₂ release experiment using nitrogen adjusted to a relative humidity of 90% as the atmospheric gas. Oxalic acid in the mixed sample had a molar ratio of 5.9 to ClO ₃ ^-LDH3 .

As for the device configuration and gas generation and measurement conditions, the compressor 610 of the device shown in FIG. Chlorine dioxide concentration was measured in the same manner as in Example 1, except for the adjustment. The results are shown in FIG.

FIG. 8 is a diagram showing changes in ClO ₂ concentration over time in Example 3. FIG.

No release of chlorine dioxide was detected immediately after coming into contact with nitrogen gas, but after about two hours it became detectable with a chlorine dioxide monitor, and release was detected for about a week. From this result, it can be said that chlorine dioxide gas is released even when CO ₂ is not contained in the ambient gas.

From the above, it is shown that a chlorine dioxide sustained-release agent containing LDH containing chlorate ions and a solid reactant (oxalic acid in this case) gradually releases chlorine dioxide upon contact with a gas containing water vapor. rice field.

(Comparative example 1)
A method of generating ClO ₂ by mixing KClO ₃ and oxalic acid, adding water and heating at 60-70° C. is well known. The presence or absence of ClO ₂ evolution under the conditions was unknown. For comparison, it was confirmed whether ClO ₂ was released under the same experimental conditions as in Example 1 using each of the above reagents. As KClO ₃ , KClO ₃ containing the same number of moles of ClO ₃ ⁻ as ClO ₃ ⁻ LDH3 in Example 1 was weighed and used.

Specifically, 6.9 mg of KClO ₃ was weighed and placed in a 13.5 mL glass bottle, 30 mg of oxalic acid was added, and the mixed sample 650 was thoroughly mixed by grinding and placed in a glass container 660. The concentration of chlorine dioxide was measured using the device shown in . The gas generation and measurement conditions were the same as in Example 1 except that air adjusted to a relative humidity of 85-90% was introduced into the glass container 660, the measurement interval was every 2-5 minutes, and the measurement was performed for 19 hours. did.

As a result, after 19 hours of measurement, the concentration sensor 690 remained at 0.00 ppm, and unlike Example 1, ClO ₂ was not detected. From this, it is a peculiar phenomenon that the sustained-release agent in which the chlorate ion-containing LDH of the present invention and the solid reactant are mixed releases chlorine dioxide under normal conditions without heating or the like. , which was newly discovered by the present inventors.

INDUSTRIAL APPLICABILITY According to the present invention, a novel layered double hydroxide can be provided as an inorganic solid material that slowly releases chlorine dioxide gas at room temperature in the atmosphere. The layered double hydroxide of the present invention is easy to handle and can function as a safe and compact chlorine dioxide gas sustained release agent by using it with a solid reactant. The layered double hydroxide of the present invention can be obtained safely.

The chlorine dioxide sustained-release agent of the present invention has the characteristics of generating chlorine dioxide gas upon contact with a water vapor-containing gas, exhibiting sustained release properties, and suppressing the initial release concentration. In addition, since the concentration of the released gas is approximately proportional to the ratio of the chlorine dioxide gas source enclosed between the layers, it is easy to control the chlorine dioxide gas concentration. Due to these properties, it is expected to be a chlorine dioxide gas supply source for medical disinfection and sterilization applications such as long-term exposure to low-concentration chlorine dioxide.

100, 200, 310, 410 Layered double hydroxide (LDH) or chlorate ion-containing LDH of the present invention
110 layer 120 anion (chlorate ion)
300 Chlorine dioxide sustained release agent 320, 420 Solid reactant 400 Package 430 Partition 440 Packaging material 500 Slow release device 510 Atmospheric gas supply unit 520 Chlorine dioxide gas sustained release unit 530 Impurity removal unit 610 Compressor or air pump 620 Relative humidity adjuster 630 control valve 640 flow meter 650 mixed sample 660 glass container 670 inlet tube 680 outlet tube 690 concentration sensor

Claims (21)

A sustained-release agent for slowly releasing chlorine dioxide gas, comprising a layered double hydroxide in which chlorate ions (ClO ₃ ⁻ ) are enclosed between layers, and a solid reactant. The sustained-release agent according to claim 1 , wherein the layered double hydroxide is represented by the following general formula (1).
Q _x R(OH) _2(x+1) {(ClO ₃ ⁻ ) _g Z ^j }.nH ₂ O
... (1)
In formula (1), Q is a divalent metal ion, R is a trivalent metal ion, and Z is an anion other than ClO ₃ ^— . Further, x, g, and j in formula (1) are numbers satisfying 1.8 ≤ x ≤ 4.2, 0.01 ≤ g ≤ 1.0, 0 ≤ j < 1.0, and n is a number that changes with the humidity of the environment. In the general formula (1),
Q is one or more selected from the group consisting of Mg ²⁺ , Mn ²⁺ , Fe ²⁺ , Co ²⁺ , Ni ²⁺ , Cu ²⁺ , Zn ²⁺ and Ca ²⁺ ,
The R is one or more selected from the group consisting of Al ³⁺ , Ga ³⁺ , Cr ³⁺ , Mn ³⁺ , Fe ³⁺ , Co ³⁺ and Ni ³⁺ ,
The sustained-release preparation according to claim 2. The sustained-release agent according to claim 3, wherein in the general formula (1), the Q is Mg2 ⁺ and the R is Al3 ⁺ . In the general formula (1), Z is OH ⁻ , Cl ⁻ , Br ⁻ , I ⁻ , F ⁻ , NO ₃ ⁻ , ClO ₄ ⁻ , SO ₄ ²⁻ , CO ₃ ²⁻ , acetate anion (CH ₃ COO ⁻ ), propionate anion (CH ₃ CH ₂ COO ⁻ ), lactate anion (CH ₃ —CH(OH)—COO ⁻ ), and isethionate anion (HOC2H ₄ SO ₃ ⁻ ). 5. The sustained release agent according to any one of claims 2 to 4, which is the above. The sustained release agent according to any one of claims 1 to 5, wherein the layered double hydroxide and the solid reactant are mixed. The sustained release agent according to any one of claims 1 to 6, wherein the solid reactant is a reducing solid and contains a compound consisting of an anion and a cation. The solid reactant includes oxalic acid, ascorbic acid, hydroquinone and salts thereof, salts containing divalent iron ions and/or divalent tin ions, and at least one of zinc, magnesium and reducing sugar, and an ionic solid. The sustained release formulation according to any one of claims 1 to 7 , containing at least one selected from the group consisting of a mixture with The sustained-release preparation according to any one of claims 1 to 8, wherein the solid reactant contains at least oxalic acid or a salt thereof. The sustained release agent according to any one of claims 1 to 9 , wherein the solid reactant satisfies a molar ratio of 0.01 to 500 with respect to the layered double hydroxide. A method for sustained release of chlorine dioxide gas using the sustained release agent according to any one of claims 1 to 10 . 12. The sustained release method of claim 11, comprising contacting the sustained release agent with a gas containing water vapor. A package comprising the sustained-release agent according to any one of claims 1 to 10 and a packaging material for hermetically housing the sustained-release agent. 14. The package according to claim 13, wherein the inside of said packaging material is in a state selected from at least one of the group consisting of a vacuum, an inert gas atmosphere, a dry atmosphere and a reduced volume state. A device for slowly releasing chlorine dioxide gas,
an atmospheric gas supply unit for supplying atmospheric gas;
a chlorine dioxide gas slow release unit for slowly releasing chlorine dioxide gas by the atmospheric gas supplied from the atmospheric gas supply unit;
A device, wherein the chlorine dioxide gas sustained release unit comprises the sustained release agent according to any one of claims 1 to 10 . 16. The apparatus according to claim 15, wherein said atmospheric gas supply unit supplies a gas containing water vapor. 17. The device according to claim 15 or 16 , further comprising an impurity removal section for removing impurity components from the chlorine dioxide gas released by said chlorine dioxide gas slow release section. 18. The device according to claim 17, wherein the impurity removal section includes an adsorbent that adsorbs chlorine ( _Cl2 ) mixed as an impurity. 19. The apparatus of claim 18, wherein said adsorbent is an organic solid having amino groups. 18. The device according to claim 17, wherein said impurity removal section comprises an adsorbent that adsorbs acid components mixed as impurities. The adsorbent includes magnesium hydroxide (Mg(OH) ₂ ), calcium hydroxide, sodium hydroxide, sodium hydrogen carbonate, layered double hydroxide in which carbonate ions are enclosed between layers, slaked lime, quicklime, soda lime, 21. The device according to claim 20, containing at least one material selected from the group consisting of polyvinylpyridine, an organic compound having an amino group, and silica gel modified with an amino group.

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