JP7656334B2 - Disinfectant and method for disinfecting water systems - Google Patents

Description

The present invention relates to a bactericide to be added to an aqueous system and a method for sterilizing an aqueous system using said bactericide, and more specifically to a bactericide that can suppress slime generation in aqueous systems such as production water in the paper and pulp industry and various industrial cooling waters, and a method for sterilizing an aqueous system using said bactericide.

It has long been known that slime caused by bacteria and fungi occurs in manufacturing process water in the paper and pulp industry and in cooling water systems in various industries, causing problems such as reduced product quality and reduced production efficiency.

Many bactericides have been used to prevent damage caused by these microorganisms. In the past, organic mercury compounds and chlorinated phenol compounds were used, but these agents are highly toxic to humans and fish and shellfish, and their use has been restricted due to environmental pollution. Recently, organic compounds with relatively low toxicity, such as organic nitrogen-sulfur compounds represented by methylene bisthiocyanate, 1,2-benzisothiazolin-3-one, and 5-chloro-2-methyl-4-isothiazolin-3-one, organic bromine compounds represented by 2,2-dibromo-2-nitroethanol, 2,2-dibromo-3-nitrilopropionamide, 1,2-bis(bromoacetoxy)ethane, 1,4-bis(bromoacetoxy)-2-butene, and bistribromomethylsulfone, and organic sulfur compounds represented by 4,5-dichloro-1,2-dithiol-3-one, have been widely used as industrial bactericides (see Non-Patent Document 1).

Slime prevention methods using inorganic compounds such as chlorine agents such as sodium hypochlorite and combined chlorine such as chloramine, as well as the combined use of these inorganic compounds with organic compounds, have also been proposed (Patent Documents 1 to 6).

Japanese Patent Application Publication No. 5-146785 JP 2000-256993 A JP 2002-336867 A JP 2003-105692 A JP 2003-306893 A JP 2008-43836 A

"Encyclopedia of Antibacterial and Antifungal Agents" published by the Japan Society of Antibacterial and Antifungal Agents on August 22, 1986, pages 24-30

However, in order to obtain final paper and pulp products of higher quality, there is a demand for a disinfectant that can further suppress slime and a disinfection method using said disinfectant.
In view of the above-mentioned conventional techniques, the present invention aims to provide a disinfectant capable of effectively suppressing the generation of slime caused by bacteria in an aqueous system such as water used in a papermaking process, and a method for sterilizing an aqueous system using the disinfectant.

The present invention relates to a disinfectant to be added to an aqueous system, characterized in that the disinfectant is produced by mixing a first composition containing an ammonium salt and an alkaline agent with a halogen-based oxidizing agent, or by mixing a second composition containing a halogen-based oxidizing agent and an alkaline agent with an ammonium salt.
The ammonium salt is preferably at least one selected from the group consisting of ammonium sulfate, ammonium nitrate, ammonium chloride, ammonium phosphate, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, ammonium bromide, and ammonium sulfamate.
The halogen-based oxidizing agent is preferably at least one selected from the group consisting of hypochlorite, chlorite, chlorate, perchlorate, and chlorine dioxide.
The molar ratio of the halogen-based oxidizing agent to the ammonium salt is preferably 1:1 to 1:2, calculated as the molar ratio of the residual chlorine amount to nitrogen.
The pH of the first composition is preferably from 4.5 to 8.5.
Incidentally, Patent Document 6 describes a method in which component (a) and component (b) are mixed with dilution water to prepare a mixed solution, and then an alkaline agent is added to adjust the pH of the mixed solution to at least 8. However, the disinfectant obtained by the method described in Patent Document 6 has a different timing of addition of the alkaline agent compared to the disinfectant of the present invention, and therefore the disinfectant obtained in Patent Document 6 is considered to have a different structure from the disinfectant of the present invention, and the disinfectant of the present invention has a superior disinfecting effect.

The present invention also relates to a method for sterilizing an aqueous system, which comprises adding the disinfectant of the present invention to the aqueous system.

The present invention provides a disinfectant that can effectively suppress the generation of slime in water systems, such as water used in papermaking processes, and a method for disinfecting water systems using the disinfectant.

The following describes an embodiment of the present invention. However, the embodiment described below is merely one representative embodiment of the present invention, and the scope of the present invention should not be interpreted narrowly.

In this specification, "X-Y" means "X or more and Y or less."

The present invention is a germicide that is added to a water system.
In this specification, "aqueous system" refers to industrial water systems such as water used in the paper pulp manufacturing process, various industrial cooling waters, seawater cooling water, etc. Water used in the paper pulp manufacturing process includes white water and pulp slurry used in the pulping process, preparation process, and papermaking process. Water used in the paper pulp manufacturing process includes water that is recycled or reused, and is water that circulates through each step in the paper pulp manufacturing process.

The disinfectant of the present invention is produced by mixing a first composition containing an ammonium salt and an alkaline agent with a halogen-based oxidizing agent, or by mixing a second composition containing a halogen-based oxidizing agent and an alkaline agent with an ammonium salt.

Monochloramine and monobrolamine, which are generally used as oxidizing agents, are mild oxidizing agents that are generated by a reaction such as OCl ⁻ (Br ⁻ ) + NH ₄ ⁺ → NH ₂ Cl (Br) + H ₂ O. For example, it is known that monochloramine can be generated by mixing sodium hypochlorite with an ammonium salt, and specific examples of the ammonium salt include ammonium sulfate, ammonium bromide, ammonium chloride, and ammonium sulfamate, which can be used alone or in combination of two or more. It is also known that monochloramine or monobrolamine is mixed with an alkaline agent for the purpose of stabilizing monochloramine and monobrolamine produced by a conventional method. It is also known that monochloramine, monobrolamine, and an alkaline agent are added separately to a target to adjust the pH of the target to which monochloramine or monobrolamine is added.

The present inventors have found that when producing monochloramine and/or monobromamine, monochloramine and/or monobromamine produced by adding an alkaline agent to an ammonium salt and controlling the pH of the ammonium salt to the alkaline side and reacting it with a halogen-based oxidizing agent has a superior bactericidal effect and can effectively suppress the generation of slime, compared to conventional monochloramine and/or monobromamine produced by reacting an ammonium salt that does not contain an alkaline agent with a halogen-based oxidizing agent, and conventional monochloramine and/or monobromamine containing an alkaline agent.
Furthermore, the present inventors have found that when producing monochloramine and/or monobromamine, monochloramine and/or monobromamine produced by reacting a halogen-based oxidizing agent containing an alkaline agent with an ammonium salt has a superior bactericidal effect and can effectively suppress the generation of slime, compared to conventional monochloramine and/or monobromamine produced by reacting a halogen-based oxidizing agent that does not contain an alkaline agent with an ammonium salt, and conventional monochloramine and/or monobromamine containing an alkaline agent.

That is, it was found that a composition produced by reacting an ammonium salt containing an alkaline agent, adjusting the pH of the ammonium salt to the alkaline side, with a halogen-based oxidizing agent, and a composition produced by reacting an ammonium salt with an alkaline agent in a halogen-based oxidizing agent have a superior bactericidal effect and an effect of suppressing the generation of slime caused by bacteria in water systems compared to conventional monochloramine and/or monobromamine, and conventional monochloramine and/or monobromamine containing an alkaline agent.

The ammonium salt used in the present invention is not particularly limited as long as it is an inorganic ammonium salt which is a reaction product of an inorganic acid and ammonia, or an organic ammonium salt which is a reaction product of an organic acid and ammonia. The inorganic ammonium salt is preferably at least one selected from the group consisting of ammonium sulfate, ammonium nitrate, ammonium chloride, ammonium phosphate, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, ammonium bromide, ammonium sulfamate, ammonium carbonate, ammonium bicarbonate, ammonium hydrogen carbonate, ammonium ferrous sulfate (III), ammonium persulfate, ammonium tungstate, ammonium metatungstate, ammonium thiocyanate, and ammonium polyphosphate. The organic ammonium salt is preferably at least one selected from the group consisting of ammonium formate, ammonium acetate, ammonium propionate, ammonium butyrate, ammonium citrate, ammonium malate, ammonium succinate, ammonium fumarate, ammonium lactate, and ammonium tartrate. Moreover, the ammonium salt is more preferably at least one selected from the group consisting of ammonium sulfate, ammonium chloride, ammonium phosphate, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, ammonium bromide, and ammonium sulfamate, and even more preferably at least one selected from the group consisting of ammonium sulfate, ammonium bromide, and ammonium sulfamate.

The halogen-based oxidizing agent used in the present invention is preferably at least one selected from the group consisting of hypochlorite, chlorite, chlorate, perchlorate, and chlorine dioxide.

The above hypochlorite salts include sodium hypochlorite, calcium hypochlorite, potassium hypochlorite, magnesium hypochlorite, etc. The above hypochlorite salts are preferably at least one selected from the group consisting of sodium hypochlorite, calcium hypochlorite, potassium hypochlorite, and magnesium hypochlorite, and more preferably at least one selected from the group consisting of sodium hypochlorite, calcium hypochlorite, and potassium hypochlorite.

The above-mentioned chlorite salts include sodium chlorite, potassium chlorite, calcium chlorite, magnesium chlorite, etc. The above-mentioned chlorite salts are preferably at least one selected from the group consisting of sodium chlorite, potassium chlorite, calcium chlorite, and magnesium chlorite.

The above-mentioned chlorate salts include potassium chlorate, sodium chlorate, calcium chlorate, barium chlorate, and magnesium chlorate. The above-mentioned chlorate salt is preferably at least one selected from the group consisting of potassium chlorate, sodium chlorate, calcium chlorate, barium chlorate, and magnesium chlorate.

The above-mentioned perchlorate salts include sodium perchlorate, potassium perchlorate, calcium perchlorate, and magnesium perchlorate. The above-mentioned perchlorate salts are preferably at least one selected from the group consisting of sodium perchlorate, potassium perchlorate, calcium perchlorate, and magnesium perchlorate.

Since chlorine dioxide is an extremely unstable chemical substance, its storage and transportation are very difficult, and therefore it is preferable to produce (generate) chlorine dioxide on-site by a known method and adjust the concentration to the desired concentration before use.
For example, chlorine dioxide can be produced by the following reaction, and a commercially available chlorine dioxide generator (apparatus) can also be used.
(1) Reaction of sodium hypochlorite, hydrochloric acid, and sodium chlorite NaOCl + 2HCl + _2NaClO2 → _2ClO2 + 3NaCl + _H2O
(2) Reaction of sodium chlorite with hydrochloric acid: _5NaClO2 + 4HCl → _4ClO2 + 5NaCl + _2H2O
( 3) Reaction with sodium chlorate, hydrogen _peroxide , and sulfuric acid _{: 2NaClO3} + _H2O2 + _H2SO4 → _2ClO2 + _Na2SO4 + _O2 + _2H2O

The halogen-based oxidizing agent used in the present invention is preferably a hypochlorite.

The alkaline agent used in the present invention is not particularly limited as long as it is an alkali metal salt or an alkaline earth metal salt that exhibits an alkaline pH when dissolved in water. The alkaline agent is preferably at least one selected from the group consisting of sodium hydroxide, potassium hydroxide, lithium hydroxide, magnesium hydroxide, calcium hydroxide, sodium carbonate, sodium bicarbonate, potassium carbonate, potassium bicarbonate, trisodium citrate, monosodium phosphate, disodium phosphate, trisodium phosphate, monopotassium phosphate, dipotassium phosphate, tripotassium phosphate, sodium malate, potassium malate, calcium malate, sodium formate, sodium acetate, sodium propionate, sodium butyrate, sodium citrate, sodium succinate, sodium fumarate, sodium lactate, and sodium tartrate. The alkaline agent used in the present invention is more preferably at least one selected from the group consisting of sodium hydroxide, potassium hydroxide, magnesium hydroxide, calcium hydroxide, sodium bicarbonate, potassium carbonate, and trisodium citrate, and even more preferably at least one selected from the group consisting of sodium hydroxide, potassium hydroxide, and trisodium citrate.

In the present invention, it is preferable that a first composition containing the ammonium salt and the alkaline agent, or a second composition containing the halogen-based oxidizing agent and the alkaline agent, is prepared before mixing the ammonium salt and the halogen-based oxidizing agent. The preparation methods of the first composition and the second composition are not particularly limited, and a general mixing method can be used.

In the present invention, the first composition preferably contains an alkaline agent so that the pH of the first composition is 1.08 times or more the pH of the ammonium salt itself. This is because the bactericide produced by reacting the ammonium salt with the above pH level with a halogen-based oxidizing agent has a sufficient bactericidal effect.

In the second composition of the present invention, it is preferable to include an alkaline agent so that the pH of the second composition is 1.05 times or more, and more preferably 1.2 times or more, of the halogen-based oxidizing agent itself. This is because the bactericide produced by reacting the halogen-based oxidizing agent with the above-mentioned pH level with an ammonium salt has a sufficient bactericidal effect.

In the present invention, the first composition preferably has a pH of 4.5 to 8.5.
Specifically, when the ammonium salt is ammonium sulfate, the pH of the first composition is preferably 4.5 to 8.5, when the ammonium salt is ammonium bromide, the pH of the first composition is preferably 7.0 to 8.5, and when the ammonium salt is ammonium sulfamate, the pH of the first composition is preferably 5.5 to 8.5.
In the present invention, the pH can be measured using a commonly used measuring device, for example, a pH meter manufactured by Horiba, Ltd.

In the present invention, it is preferable that the pH of the second composition is 10.5 to 12.5.

In the present invention, the molar ratio of the halogen-based oxidizing agent to the ammonium salt (halogen-based oxidizing agent:ammonium salt) is preferably 1:1 to 1:2, more preferably 1:1.1 to 1:2, even more preferably 1:1.2 to 1:2, and particularly preferably 1:1.2 to 1:1.6, as the molar ratio of the residual chlorine amount to nitrogen.

In the present invention, the weight ratio of the first composition to the halogen-based oxidizing agent and the weight ratio of the second composition to the ammonium salt are preferably determined so that the molar ratio of the halogen-based oxidizing agent to the ammonium salt (halogen-based oxidizing agent:ammonium salt) falls within the above range.

The concentration of the disinfectant of the present invention added to the above-mentioned aqueous system (e.g., the concentration after addition to the paper pulp manufacturing water) can be appropriately determined according to the disinfection rate of the disinfectant relative to the paper pulp manufacturing water to be treated as the total residual chlorine concentration, and is preferably, for example, 0.1 to 35 mg/L. Moreover, the residual chlorine concentration of the papermaking process water after the composition addition step is more preferably 0.5 to 30 mg/L, even more preferably 1 to 30 mg/L, and from the viewpoint of economy, is preferably 1 to 25 mg/L or 1 to 20 mg/L.
In the present invention, the term "residual chlorine concentration" means a "residual chlorine amount equivalent value" when the halogen-based oxidizing agent is not a chlorine-based oxidizing agent.

Regarding the timing for adding the fungicide of the present invention, the fungicide can be added to a storage tank such as a white water silo or white water pit, but as long as it can be added to the water in the paper pulp manufacturing process, it may be added at any point in the process, and the present invention is not limited to this.
The fungicide of the present invention may be added intermittently or continuously.

By adding the above-mentioned bactericide of the present invention to an aqueous system, the generation of slime caused by bacteria present in the aqueous system can be effectively suppressed.
Such a method for sterilizing a water system using the disinfectant of the present invention also constitutes one aspect of the present invention.

The present invention will be specifically explained below based on examples, comparative examples, and reference examples, but the present invention is not limited to these examples.

(Examples 1 to 3, Comparative Example 1)
[Raw materials]
White water was collected from the paperboard manufacturing process (machine chest) of a certain paper mill.
[Preparation of disinfectant and confirmation of disinfectant effect]
(1) 10 mL of the collected white water was dispensed into a sterilized L-shaped tube to prepare sample water.
(2) A first composition (pH 6.8) containing 3.5 mol/L of ammonium sulfate (reagent manufactured by Kishida Chemical Co., Ltd.) and 2.7×10 ⁻³ mol/L of sodium hydroxide (reagent manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was mixed with a second composition containing 1.7 mol/L of sodium hypochlorite (reagent manufactured by Kishida Chemical Co., Ltd.) to prepare a bactericide, and the resulting bactericide was added to sample water so that the total chlorine concentration was the concentration shown in Table 1 (Examples 1 to 3). The sample to which no bactericide was added was designated Comparative Example 1.
(3) Next, the sample water was shaken for 5 minutes, and the sample water according to the embodiment was brought into contact with the disinfectant for 5 minutes.
(4) A portion of the sample water according to the embodiment that had been in contact with the disinfectant for 5 minutes and a portion of the sample water according to the comparative example 1 were taken and cultured on a standard agar medium to measure the number of bacteria. The results are shown in Table 1.

(Examples 4 to 8, Comparative Example 2)
[Raw materials]
White water was collected from the paper manufacturing process (machine chest) of a certain paper mill.
[Preparation of disinfectant and confirmation of disinfectant effect]
The preparation of the disinfectant and confirmation of its disinfecting effect were carried out in the same manner as in Example 1. The results are shown in Table 2.

(Examples 9 to 10, Comparative Example 3, Reference Examples 1 to 2)
[Test for Pseudomonas aeruginosa]
[Preparation of disinfectant]
The fungicides of Examples 9 and 10 were prepared in the same manner as in Example 1.
As the disinfectant in Reference Examples 1 and 2, a reaction product obtained by mixing 3.5 mol/L of ammonium sulfate (a reagent manufactured by Kishida Chemical Co., Ltd.) and 1.7 mol/L of sodium hypochlorite (a reagent manufactured by Kishida Chemical Co., Ltd.) was used at the total chlorine concentration shown in Table 3. In addition, Comparative Example 3 was prepared by adding no disinfectant.
[Target bacteria]
Pseudomonas areruginosa (type bacterium)
[Test Method]
(1) 1 mL of the bacterial solution cultured in liquid medium was collected into microtubes, and the medium and bacteria were separated using a centrifuge.
(2) The medium separated by centrifugation was removed, and approximately 1 mL of sterile saline was added and then removed to remove the remaining medium.
(3) After removing the medium, 1 mL of a disinfectant prepared in the same manner as in Example 1, with the total chlorine concentration shown in Table 3, was added to the microtube in which only the bacteria remained.
(4) The bacteria was allowed to come into contact with the disinfectant for 5 minutes.
(5) After the contact was completed, a portion of the bacterial liquid was collected and planted in a liquid bouillon medium in an L-shaped tube.
(6) The L-shaped tube was incubated at 37° C. with shaking, and the number of bacteria was measured at 1, 3, and 5 hours. The results are shown in Table 3.

Claims (7)

A disinfectant added to a water system, comprising:
The method is produced by mixing a first composition including an ammonium salt and an alkaline agent with a halogen-based oxidizing agent ,
The first composition contains an alkaline agent so that the pH of the ammonium salt itself is 1.08 times or more, and has a pH of less than 9.
A bactericide characterized by: The disinfectant according to claim 1, wherein the ammonium salt is at least one selected from the group consisting of ammonium sulfate, ammonium nitrate, ammonium chloride, ammonium phosphate, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, ammonium bromide, and ammonium sulfamate. The disinfectant according to claim 1 or 2, wherein the halogen-based oxidizing agent is at least one selected from the group consisting of hypochlorite, chlorite, chlorate, perchlorate, and chlorine dioxide. The disinfectant according to claim 1 or 2, wherein the molar ratio of the halogen-based oxidizing agent to the ammonium salt (halogen-based oxidizing agent:ammonium salt) is 1:1 to 1:2 as the molar ratio of the residual chlorine amount to nitrogen. The disinfectant according to claim 1 or 2, wherein the pH of the first composition is 4.5 to 8.5. The disinfectant according to claim 1 or 2, which is added to an aqueous system containing Pseudomonas aeruginosa. A method for sterilizing an aqueous system, comprising adding the bactericide according to claim 1 or 2 to the aqueous system.