JP7560705B2 - Water treatment agent and method for stabilizing water treatment agent - Google Patents

Description

The present invention relates to a water treatment agent and a method for stabilizing the water treatment agent.

The metal materials (copper, iron, mild steel, cast iron, etc.) used in heat exchangers, piping, and various equipment that make up industrial cooling water systems are in constant contact with water, making the surfaces of the metal materials susceptible to problems such as corrosion. To prevent such problems from occurring, water treatment agents containing azole-based compounds as metal corrosion inhibitors are known (see, for example, Patent Document 1).

However, when water treatment agents containing azole compounds are combined with other ingredients, the concentration of the azole compounds can drop significantly, making it difficult to stably exert the functions of the azole compounds over a long period of time, or causing problems such as the formation of precipitates in the water treatment agent that can clog the injection pump and prevent the water treatment agent from functioning as a whole.

JP 2010-173994 A

The object of the present invention is to provide a water treatment agent that can stably exert the functions of an azole-based compound over a long period of time, and to provide a method for stabilizing a water treatment agent that can stably exert the functions of an azole-based compound over a long period of time.

These objects can be achieved by the present invention described in (1) to ( 6 ) below.
(1) An antibacterial composition comprising an azole compound , an amino acid having a molecular weight of 75 to 500 , and bronopol ,
A water treatment agent characterized in that , when the content of the amino acid is X2 [mol %] and the content of the bronopol is X3 [mol %], the relationship of 1≦X3/X2≦12000 is satisfied .

(2) The water treatment agent according to (1) above, wherein the amino acid is an acidic amino acid or a neutral amino acid.

(3) The water treatment agent according to (1) above, wherein the amino acid is at least one selected from the group consisting of glycine, glutamic acid, glutamine, alanine, arginine, aspartic acid, and salts thereof.

(4) A water treatment agent according to any one of (1) to (3) above, which satisfies the relationship 0.0008≦X2/X1≦30, where X1 [mol %] is the content of the azole compound in the water treatment agent, and X2 [mol %] is the content of the amino acid in the water treatment agent.

( 5 ) The water treatment agent according to any one of the above (1) to ( 4 ), wherein the azole compound is benzotriazole.

( 6 ) A water treatment agent containing an azole compound is made to contain an amino acid having a molecular weight of 75 to 500 and bronopol ,
A method for stabilizing a water treatment agent, comprising: satisfying a relationship of 1≦X3/X2≦12000, where X2 is the content of the amino acid in the water treatment agent (mol%) and X3 is the content of the bronopol in the water treatment agent (mol%) .

The present invention provides a water treatment agent that can stably exert the functions of an azole-based compound over a long period of time, and also provides a method for stabilizing a water treatment agent that can stably exert the functions of an azole-based compound over a long period of time.

Preferred embodiments of the present invention will now be described in detail.
[1] Water Treatment Agent First, the water treatment agent of the present invention will be described.

The water treatment agent of the present invention contains an azole compound that functions as an anticorrosive agent. The water treatment agent of the present invention is characterized by containing an amino acid in addition to the azole compound.

This improves the stability of the azole compound in the water treatment agent, and effectively prevents, for example, a decrease in the concentration of the azole compound due to the influence of other components in the water treatment agent. As a result, the water treatment agent is able to stably exert the functions (anticorrosion properties, etc.) of the azole compound over a long period of time.

In the present invention, the water treatment agent refers to a substance used by mixing with a liquid whose main component is water (e.g., a liquid whose water content is 50% by mass or more). In other words, the object to be treated with the water treatment agent of the present invention is a liquid whose main component is water (e.g., a liquid whose water content is 50% by mass or more).
Examples of liquids to which the water treatment agent can be applied (liquids mainly composed of water) include industrial water, industrial cooling water, plant water, wastewater, and the like.

The liquid to which the water treatment agent is applied (liquid mainly composed of water) may be seawater collected from the ocean, fresh water, brackish water, groundwater, rainwater, etc. collected from rivers, lakes, ponds, swamps, etc., collected from nature, or it may be tap water.

[1-1] Azole Compound As described above, the water treatment agent of the present invention contains an azole compound.
The azole compound is a component that exhibits anticorrosive properties in water treatment agents.

An azole compound is a heterocyclic compound having one or more nitrogen atoms in a five-membered heterocyclic ring structure. In other words, an azole compound is a compound having a five-membered heterocyclic ring, and at least one of the five elements constituting the five-membered heterocyclic ring is a nitrogen atom.

Examples of azole compounds include compounds having one nitrogen atom in a five-membered heterocyclic ring such as pyrrole (azole in the narrow sense), compounds having two nitrogen atoms in a five-membered heterocyclic ring such as pyrazole (1,2-diazole) and imidazole (1,3-diazole) (diazole), compounds having three nitrogen atoms in a five-membered heterocyclic ring such as 1,2,3-triazole and 1,2,4-triazole (triazole), compounds having four nitrogen atoms in a five-membered heterocyclic ring (tetrazole), compounds containing other heteroatoms in addition to the nitrogen atom in the five-membered heterocyclic ring such as thiazole, isothiazole, oxazole, isoxazole, and furazan, and compounds having a structure in which at least one of the hydrogen atoms of these compounds is replaced with another atom or atomic group. However, as an azole compound, a compound in which the only heteroatom contained in the five-membered heterocyclic ring structure is a nitrogen atom is preferred.

This makes it possible to improve the corrosion prevention properties of the water treatment agent. In addition, the synergistic effect of using it in combination with amino acids can be more pronounced.

Of these, the azole compound is preferably benzotriazole.
This makes the above-mentioned effects even more pronounced.

[1-2] Amino Acids As described above, the water treatment agent of the present invention contains amino acids.

Amino acids are components that contribute to improving the stability of azole compounds in water treatment agents. By including such amino acids together with the azole compounds, for example, it is possible to effectively prevent a decrease in the concentration of the azole compounds due to the influence of other components in the water treatment agent, and it is possible to stably exert the functions (anticorrosion properties, etc.) of the azole compounds over a long period of time.

The amino acid may be a compound having an amino group and a carboxyl group in the molecule, and at least one of the amino group and the carboxyl group may be in the form of a salt.

The amino acids may be α-amino acids, β-amino acids, γ-amino acids, δ-amino acids, etc., in addition to α-amino acids. However, α-amino acids are preferred from the viewpoints of cost and availability.
The α-amino acids may be of either the D- or L-form.

Specific examples of α-amino acids include alanine, arginine, asparagine, aspartic acid, cysteine, glutamine, glutamic acid, glycine, histidine, isoleucine, leucine, lysine, methionine, phenylalanine, proline, serine, threonine, tryptophan, tyrosine, and valine.

Specific examples of other amino acids include cystine, hydroxyproline, hydroxylysine, thyroxine, phosphoserine, desmosine, β-alanine, sarcosine, ornithine, citrulline, creatine, γ-aminobutyric acid, opine, trimethylglycine, theanine, tricolominic acid, and kainic acid.

The water treatment agent of the present invention may contain at least one of the above amino acids, but may also contain two or more amino acids.

The amino acid is preferably an acidic or neutral amino acid.
This makes it possible to improve the solubility of the amino acid in the water treatment agent and the storage stability of the water treatment agent. In particular, when the water treatment agent has a pH as described below, the above-mentioned effects are more pronounced.

Examples of acidic amino acids include aspartic acid and glutamic acid.
Examples of neutral amino acids include glycine, alanine, valine, leucine, isoleucine, serine, threonine, cysteine, methionine, asparagine, glutamine, proline, phenylalanine, tyrosine, and tryptophan.

The molecular weight of the amino acid is preferably 75 to 500, more preferably 75 to 250, and even more preferably 75 to 200.

The water treatment agent of the present invention preferably contains, as the amino acid, at least one selected from the group consisting of glycine, glutamic acid, glutamine, alanine, arginine, aspartic acid, and salts thereof.
This makes it possible to improve the solubility of the amino acid in the water treatment agent and the storage stability of the water treatment agent. In particular, when the water treatment agent has a pH as described below, the above-mentioned effects are more pronounced.

The proportion of the amino acids in the above group in the total amino acids contained in the water treatment agent is preferably 50 mol % or more, more preferably 70 mol % or more, and even more preferably 90 mol % or more.
This makes the above-mentioned effects more pronounced.

When the content of the azole compound in the water treatment agent is X1 [mol %] and the content of the amino acid in the water treatment agent is X2 [mol %], it is preferable that the relationship 0.0008≦X2/X1≦30 is satisfied, it is more preferable that the relationship 0.001≦X2/X1≦20 is satisfied, and it is even more preferable that the relationship 0.01≦X2/X1≦10 is satisfied.

This makes it possible to reduce the amount of azole compounds and amino acids used while achieving a higher level of both corrosion prevention at the initial stage (immediately after the water treatment agent is manufactured) and the stability of the azole compounds in the water treatment agent.

When the water treatment agent contains multiple types of compounds as azole compounds, the sum of their contents is X1. When the water treatment agent contains multiple types of compounds as amino acids, the sum of their contents is X2.

[1-3] Liquid medium The water treatment agent of the present invention may contain the above-mentioned azole compound and amino acid, but it is preferable that the water treatment agent further contains a liquid medium in which these are dissolved or dispersed, in other words, a liquid component that functions as a solvent or dispersion medium.

This improves ease of handling of the water treatment agent and ease of mixing the water treatment agent of the present invention with the material to be treated.

Examples of liquid media include water; ketone compounds such as methyl ethyl ketone (MEK), acetone, diethyl ketone, methyl isobutyl ketone (MIBK), methyl isopropyl ketone (MIPK), cyclohexanone, 3-heptanone, and 4-heptanone; monohydric alcohols such as methanol, ethanol, n-propanol, isopropanol, n-butanol, i-butanol, t-butanol, 3-methyl-1-butanol, 1-pentanol, 2-pentanol, n-hexanol, cyclohexanol, 1-heptanol, 1-octanol, 2-octanol, 2-methoxyethanol, allyl alcohol, furfuryl alcohol, and phenol; ethylene glycol, propylene glycol, and butyl alcohol. alcohol-based compounds such as polyhydric alcohols such as ethylene glycol and glycerin; diethyl ether, dipropyl ether, diisopropyl ether, dibutyl ether, 1,2-dimethoxyethane (DME), 1,4-dioxane, tetrahydrofuran (THF), tetrahydropyran (THP), anisole, diethylene glycol dimethyl ether (diglyme), 2-methoxyethanol, condensates of the above polyhydric alcohols (polyhydric alcohol ethers), alkyl ethers of the above polyhydric alcohols or the above polyhydric alcohol ethers (for example, methyl ether, ethyl ether, butyl ether, hexyl ether, etc.); methyl cellosolve, ethyl cellosolve, phenyl cellosolve, etc. aliphatic hydrocarbon compounds such as hexane, pentane, heptane, cyclohexane, methylcyclohexane, octane, didecane, methylcyclohexene, and isoprene; aromatic hydrocarbon compounds such as toluene, xylene, benzene, ethylbenzene, and naphthalene; aromatic heterocyclic compounds such as pyridine, pyrazine, furan, pyrrole, thiophene, 2-methylpyridine, 3-methylpyridine, 4-methylpyridine, and furfuryl alcohol; amide compounds such as N,N-dimethylformamide (DMF) and N,N-dimethylacetamide (DMA); halogen compounds such as dichloromethane, chloroform, 1,2-dichloroethane, trichloroethylene, and chlorobenzene; Examples of the compounds include ester compounds such as cetylacetone, ethyl acetate, methyl acetate, isopropyl acetate, isobutyl acetate, isopentyl acetate, ethyl chloroacetate, butyl chloroacetate, isobutyl chloroacetate, ethyl formate, isobutyl formate, ethyl acrylate, methyl methacrylate, and ethyl benzoate; amine compounds such as trimethylamine, hexylamine, triethylamine, and aniline; nitrile compounds such as acrylonitrile and acetonitrile; nitro compounds such as nitromethane and nitroethane; and aldehyde compounds such as acetaldehyde, propionaldehyde, butyraldehyde, pentanal, and acrylaldehyde. One or more of these compounds may be used in combination.

In particular, it is more preferable that the water treatment agent contains water as the liquid medium.
This allows the water treatment agent to have better diffusibility in the liquid (liquid mainly composed of water) to which it is applied, and allows the constituent components of the water treatment agent (e.g., azole-based compounds, etc.) to more suitably exhibit their functions when applied to the liquid. In addition, even if the liquid to which the water treatment agent is applied is released into the natural environment, adverse effects on the environment can be suppressed. This is also preferable from the viewpoint of reducing the manufacturing cost of the water treatment agent.

When the liquid medium constituting the water treatment agent contains water, the proportion of water to the entire liquid medium contained in the water treatment agent of the present invention is preferably 50 mass% or more, more preferably 80 mass% or more, and even more preferably 90 mass% or more.
This makes the above-mentioned effects more pronounced.

[1-4] Bronopol The water treatment agent may further contain bronopol.

This makes it possible to suitably impart bactericidal properties to the water treatment agent. The inventors have also found that there is a problem in that the coexistence of bronopol with an azole compound in the water treatment agent promotes a decrease in the concentration of the azole compound. In contrast, the present invention contains an amino acid, so that a decrease in the concentration of the azole compound can be effectively prevented even when bronopol and the azole compound coexist. In other words, the effects of the present invention are more pronounced when the water treatment agent contains bronopol as well as an azole compound.

When the content of the azole compound in the water treatment agent is X1 [mol %] and the content of bronopol in the water treatment agent is X3 [mol %], it is preferable that the relationship 0.5≦X3/X1≦60 is satisfied, it is more preferable that the relationship 1≦X3/X1≦50 is satisfied, and it is even more preferable that the relationship 2≦X3/X1≦40 is satisfied.

This allows the amount of azole compounds and bronopol used to be reduced while still achieving a higher level of disinfection and anticorrosion properties in the water treatment agent.

When the content of amino acids in the water treatment agent is X2 [mol %] and the content of bronopol in the water treatment agent is X3 [mol %], it is preferable to satisfy the relationship 0.5≦X3/X2≦12000, it is more preferable to satisfy the relationship 1≦X3/X2≦6000, and it is even more preferable to satisfy the relationship 2≦X3/X2≦1200.

This allows the amount of azole compounds, bronopol, and amino acids used to be reduced, while still achieving higher levels of bactericidal properties of the water treatment agent, anticorrosive properties at the initial stage (immediately after the water treatment agent is manufactured), and stability of the azole compounds in the water treatment agent.

[1-5] Thiazoline Compound The water treatment agent may further contain a thiazoline compound.

This makes it possible to favorably impart bactericidal properties to the water treatment agent. In particular, by containing a thiazoline-based compound together with the above-mentioned bronopol, the bactericidal spectrum of the water treatment agent can be made more favorable. In other words, when the water treatment agent contains a thiazoline-based compound together with an azole-based compound, the effect of the present invention is more pronounced.

Thiazoline compounds are heterocyclic compounds that contain one nitrogen atom and one sulfur atom in a five-membered heterocyclic ring structure. In other words, thiazoline compounds are compounds that have a five-membered heterocyclic ring, and one of the five elements that make up the ring is a nitrogen atom and the other is a sulfur atom.

Examples of thiazoline compounds include 2-thiazoline, 3-thiazoline, 4-thiazoline, thiazole, thiazolidine, isothiazolinone, methylisothiazolinone, chloromethylisothiazolinone, octylisothiazolinone, dichlorooctylisothiazolinone, benzisothiazolinone, 2-aminothiazoline-4-carboxylic acid, luciferin, and compounds in which at least one of the hydrogen atoms in these compounds is replaced with another atom or atomic group.

Among them, the thiazoline compound is preferably at least one selected from the group consisting of methylisothiazolinone, chloromethylisothiazolinone and octylisothiazolinone.
This makes the above-mentioned effects more pronounced.

When the content of the azole compound in the water treatment agent is X1 [mol %] and the content of the thiazoline compound in the water treatment agent is X4 [mol %], it is preferable that the relationship 0.1≦X4/X1≦50 is satisfied, it is more preferable that the relationship 0.5≦X4/X1≦40 is satisfied, and it is even more preferable that the relationship 1≦X4/X1≦30 is satisfied.

This allows the amount of azole and thiazoline compounds used to be reduced while still achieving a higher level of bactericidal and anticorrosive properties in the water treatment agent.

When the water treatment agent contains multiple types of compounds as azole compounds, the sum of their contents is X1. When the water treatment agent contains multiple types of compounds as thiazoline compounds, the sum of their contents is X4.

When the content of amino acids in the water treatment agent is X2 [mol %] and the content of thiazoline compounds in the water treatment agent is X4 [mol %], it is preferable to satisfy the relationship 0.05≦X4/X2≦6000, it is more preferable to satisfy the relationship 0.1≦X4/X2≦2000, and it is even more preferable to satisfy the relationship 0.5≦X4/X2≦600.

This allows the use of reduced amounts of azole compounds, thiazoline compounds, and amino acids while achieving higher levels of bactericidal properties of the water treatment agent, anticorrosive properties at the initial stage (immediately after the water treatment agent is manufactured), and stability of the azole compounds in the water treatment agent.

When the content of bronopol in the water treatment agent is X3 [mol %] and the content of thiazoline-based compounds in the water treatment agent is X4 [mol %], it is preferable that the relationship 0.01≦X4/X3≦30 is satisfied, it is more preferable that the relationship 0.05≦X4/X3≦20 is satisfied, and it is even more preferable that the relationship 0.1≦X4/X3≦10 is satisfied.

This allows the amount of bronopol and thiazoline compounds used to be reduced while still improving the bactericidal properties of the water treatment agent.

[1-6] Scale inhibitor The water treatment agent may further contain a scale inhibitor.
Examples of the scale inhibitor include acrylic acid, phosphonic acid, and maleic acid compounds.

As maleic acid-based compounds, for example, polymers having maleic acid or its derivatives as monomer units, and salts thereof can be suitably used.

Examples of derivatives of maleic acid include maleic anhydride and (N-hydroxyphenyl)maleimide. The polymer may be a homopolymer of maleic acid or its derivatives, or a copolymer with a monomer that can be copolymerized therewith. Examples of copolymerizable monomers include acrylic acid, methacrylic acid, isobutylene, amylene, acrylamidomethylpropanol sulfonic acid, and allylsulfonic acid.

The content of the scale inhibitor in the water treatment agent is preferably 0.5% by mass or more and 60% by mass or less, more preferably 1.0% by mass or more and 55% by mass or less, and even more preferably 1.5% by mass or more and 50% by mass or less.

[1-7] Other components The water treatment agent may contain components other than those described above (hereinafter also referred to as "other components"). Examples of such components include bactericides other than thiazoline compounds and bronopol, anticorrosive agents other than azole compounds, pH adjusters, tracer substances, antioxidants, excipients, thickeners, gelling agents, colorants, fillers, binders, coagulants, lubricants, lubricants, solubilizers, preservatives, surfactants, emulsifiers, dispersants, opacifiers, suspending agents, fragrances, flavorings, coating agents, etc.

Examples of anticorrosive agents other than azole compounds include zinc compounds, phosphate compounds, metal acids of Group 6 elements, and their salts.

Examples of the phosphoric acid compound include condensed phosphoric acid, orthophosphoric acid, and phosphonic acid, and more specifically, polyphosphoric acid, trimetaphosphoric acid, tetrametaphosphoric acid, hexametaphosphoric acid, and ultrametaphosphoric acid.

Examples of metal acids of Group 6 elements include chromic acid, molybdic acid, and tungstic acid.

Examples of phosphate compounds and salts of metal acids of Group 6 elements include alkali metal salts such as lithium salts, potassium salts, and sodium salts, and ammonium salts.

However, the content of other components in the water treatment agent is preferably 10% by mass or less, more preferably 5% by mass or less, and even more preferably 3% by mass or less.

[1-8] Physical properties and characteristics of the water treatment agent as a whole The water treatment agent of the present invention preferably satisfies the following conditions.

That is, the pH of the water treatment agent at 23°C is preferably 0.0 or more and less than 3.0, more preferably 0.0 or more and less than 2.8, and even more preferably 0.0 or more and less than 2.7.

This allows for a higher level of stability for each component in the water treatment agent.

In addition, when the water treatment agent of the present invention is left to stand for 14 days under sealed conditions at 50°C, the remaining rate of the azole compound is preferably 70% or more, more preferably 80% or more, and even more preferably 90% or more.

This allows the azole compounds to stably exert their functions for a longer period of time.

The water treatment agent of the present invention may be in any form, and examples of the form of the water treatment agent of the present invention include tablet, powder (including granules), gel, liquid, paste, etc.

[2] Method for stabilizing a water treatment agent Next, the method for stabilizing a water treatment agent of the present invention will be described.

The method for stabilizing a water treatment agent of the present invention is characterized in that an amino acid is added to a water treatment agent containing an azole compound.

This provides a method for stabilizing water treatment agents that allows azole compounds to stably exert their functions over a long period of time.

The final water treatment agent obtained after the incorporation of the amino acid preferably satisfies the conditions detailed in [1] above.
This provides the above-mentioned effects.

The above describes preferred embodiments of the present invention, but the present invention is not limited to these.

The present invention will be explained in more detail below with specific examples, but the present invention is not limited to the following examples. In the following explanation, treatments for which no particular temperature or humidity conditions are specified were performed at room temperature (23°C) and a relative humidity of 50%. In addition, for various measurement conditions, values for which no particular temperature or humidity conditions are specified are those at room temperature (23°C) and a relative humidity of 50%.

[3] Production of water treatment agent (Example 1)
A water treatment agent having the composition shown in Table 1 was produced by mixing the azole compound, amino acid, and other components in a given ratio.

(Examples 2 to 18)
Water treatment agents were produced in the same manner as in Example 1, except that the types and contents of the constituent components were changed to those shown in Table 1. In Examples 8, 9, 12, and 13, hydrochloric acid or sodium hydroxide was also mixed to obtain the specified pH shown in Table 1.

(Comparative Examples 1 to 4)
Water treatment agents were produced in the same manner as in Example 1, except that no amino acid was used and the types and contents of the constituent components were changed to those shown in Table 1. In addition, for Comparative Examples 2 to 4, hydrochloric acid or sodium hydroxide was also mixed in to obtain the specified pH shown in Table 1.

The composition of the water treatment agents of the above-mentioned Examples and Comparative Examples is summarized in Table 1. Table 1 also shows the ratios (X2/X1, X3/X1, X3/X2, X4/X1, X4/X2, X4/X3) of the azole compound content in the water treatment agent (X1 [mol %)), the amino acid content in the water treatment agent (X2 [mol %)), the bronopol content in the water treatment agent (X3 [mol %)), and the thiazoline compound content in the water treatment agent (total value when multiple types are included) (X4 [mol %)) and the pH value of the water treatment agent at 23°C. In Table 1, benzotriazole is represented as "BTA", glycine (neutral amino acid) as "Gly", L-sodium glutamate (acidic amino acid) as "GluNa", L-glutamic acid (acidic amino acid) as "GluAcid", L-glutamine (neutral amino acid) as "Glu", L-alanine (neutral amino acid) as "Ala", L-arginine (basic amino acid) as "Arg", L-aspartic acid (acidic amino acid) as "AspAcid", bronopol as "BNP", 5-chloro-2-methyl-4-isothiazolin-3-one as "CMIT", 2-methyl-4-isothiazolin-3-one as "MIT", and sodium salt of isobutylene-maleic acid copolymer as "PIBMNa".

[4] Evaluation The water treatment agents of each of the Examples and Comparative Examples were allowed to stand for 14 days under light-shielded conditions at 50°C, and then the contents in the water treatment agents immediately after production were measured using high performance liquid chromatography to compare them with the contents in the water treatment agents immediately after production. From the results, the residual rates of the azole compound and bronopol were determined and evaluated according to the following criteria.

A: Residual rate is 90% or more.
B: Residual rate is 70% or more and less than 90%.
C: Residual rate is 50% or more and less than 70%.
D: Residual rate is 30% or more and less than 50%.
E: Residual rate is less than 30%.
These results are summarized in Table 2.

As is clear from Table 2, the water treatment agent of the present invention provided excellent results, whereas the comparative examples did not provide satisfactory results.

Furthermore, when the disinfecting power of the water treatment agents of Examples 2 and 4 and Comparative Example 1 was evaluated, no decrease in disinfecting power due to the inclusion of amino acids was observed.
The disinfection ability was evaluated as follows.

That is, first, a test strain of Pseudomonas fluorescens (NBRC-3081) was prepared.
The test strain was cultured in Mueller Hinton Agar (Kanto Chemical Co., Ltd.) at 30°C ± 1°C for 18 to 24 hours, and then in order to isolate Pseudomonas bacteria, one platinum loop was inoculated into Mueller Hinton Broth (Becton Dickinson Co., Ltd.), and the OD value was measured after culturing at 30°C ± 1°C for 18 to 24 hours. One platinum loop was inoculated into Mueller Hinton Broth again from the first generation cultured bacterial solution after isolation with an OD value closest to 0.5, and cultured at 30°C ± 1°C for 18 to 24 hours, and the OD value was measured, and the second generation cultured bacterial solution after isolation with an OD value closest to 0.5 was used as the test bacterial solution.

The water treatment agents of each of the above examples and comparative examples were diluted to 10 times the concentration to be added using sterilized distilled water, and 1 ml of each diluted solution thus obtained was inoculated into a platinum loop of second generation cultured bacteria solution of Mueller Hinton Broth, and the OD value was measured after culturing at 30°C ± 1°C for 18 to 24 hours.

Claims (6)

The present invention comprises an azole compound , an amino acid having a molecular weight of 75 to 500 , and bronopol ,
A water treatment agent characterized in that , when the content of the amino acid is X2 [mol %] and the content of the bronopol is X3 [mol %], the relationship of 1≦X3/X2≦12000 is satisfied . The water treatment agent according to claim 1, wherein the amino acid is an acidic amino acid or a neutral amino acid. The water treatment agent according to claim 1, wherein the amino acid is at least one selected from the group consisting of glycine, glutamic acid, glutamine, alanine, arginine, aspartic acid, and salts thereof. The water treatment agent according to any one of claims 1 to 3, which satisfies the relationship 0.0008≦X2/X1≦30, where X1 [mol %] is the content of the azole compound in the water treatment agent, and X2 [mol %] is the content of the amino acid in the water treatment agent. The water treatment agent according to any one of claims 1 to 4 , wherein the azole compound is benzotriazole. A water treatment agent containing an azole compound is made to contain an amino acid having a molecular weight of 75 to 500 and bronopol ,
A method for stabilizing a water treatment agent, comprising: satisfying a relationship of 1≦X3/X2≦12000, where X2 is the content of the amino acid in the water treatment agent (mol%) and X3 is the content of the bronopol in the water treatment agent (mol%) .