Water treatment composition and water treatment method

Abstract

To provide a water treatment composition and a water treatment method capable of suppressing metal corrosion in a water system that requires the addition of an oxidizing agent, without minimizing the reduction of the efficacy of the oxidizing agent and without increasing the amount of metal corrosion inhibitor.SOLUTION: The present invention provides a water treatment composition for addition to a water system in contact with metal, the water treatment composition comprising an oxidizing agent and a nonionic surfactant as a corrosion rate reducing agent.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a water treatment composition and a water treatment method. [Background technology]

[0002] Conventionally, in aqueous systems into which an aqueous medium is introduced or passes, such as various cooling systems and heat exchange systems in petrochemical, synthetic chemical, food chemical, iron and steel, paper, textile plants, power generation, geothermal utilization, mechanical industries, etc., various metals come into contact with water in the aqueous systems, and corrosion of these metals occurs easily, so that various metal corrosion inhibitors and corrosion prevention methods have been proposed. For example, metal corrosion inhibitors such as phosphates, phosphonates, polyphosphates, zinc salts, molybdates, and tungstates are used, but the amount of these metal corrosion inhibitors to be used tends to be limited due to wastewater regulations for phosphorus, heavy metals, etc. In particular, in recent years, from the standpoint of the safety of the water system to be treated and maintaining the working environment, it is desired to provide a water treatment chemical and a water treatment method that are highly safe while reducing the amount of metal corrosion inhibitors containing phosphorus and heavy metals added.

[0003] Furthermore, when the metal members used in the aqueous system are copper-based, water treatment is carried out by adding an azole-based copper corrosion inhibitor such as benzotriazole, tolyltriazole, or mercaptobenzothiazole to the aqueous system in order to inhibit corrosion of the copper-based members (e.g., Patent Documents 1 and 2). These azole-based copper corrosion inhibitors are excellent in inhibiting the metal elution reaction (anodic reaction) in the corrosion reaction, and are widely used because adding these azole-based copper corrosion inhibitors to aqueous systems such as cooling water systems exhibits an excellent corrosion inhibition effect on copper-based members in contact with the aqueous system.

[0004] In general, the corrosion reaction (wet corrosion) of metals in water proceeds through electrochemical reactions. The oxidation reaction (anodic reaction) in which electrons of the metal are released into the water and the dissolved oxygen and H +The reduction reaction (cathode reaction) in which the oxidizer accepts electrons proceeds in pairs. For example, in an environment where an oxidizer is added to a water system to prevent slime damage, such as when slime damage occurs in the water system to be treated, the presence of highly oxidizing residual chlorine in the system tends to increase metal corrosion. For this reason, depending on the water system, the effect of existing metal corrosion inhibitors is not fully achieved, causing corrosion of metal parts in contact with the water system and shortening the service life of the equipment. Therefore, there is a demand for water treatment agents and water treatment methods that can provide sufficient metal corrosion prevention effects even when the water quality of the water system to be treated is in an environment prone to metal corrosion, for example, due to the presence of highly oxidizing residual chlorine.

[0005] For example, JP 2012-056874 A (Patent Document 3) proposes a cooling water system treatment method characterized by including a chlorine-based oxidizing agent in the cooling water system in the first stage and including a surfactant-based chemical in the cooling water system in the second stage, for the purpose of obtaining slime removal effects and microbial sterilization effects in the cooling water system. The treatment method described in Patent Document 3 is described as a slime removal and sterilization method that is not only slime removal and microbial sterilization effects, but also has low corrosiveness, high safety, low chemical usage, and high workability, but does not use existing metal corrosion inhibitors, and metal corrosion has been insufficiently examined.

[0006] Therefore, for aqueous systems that require the addition of oxidizing agents to prevent slime problems, fouling problems, and the like, there is room for further study of water treatment chemicals and water treatment methods that can suppress metal corrosion in aqueous systems without significantly reducing the effectiveness of the oxidizing agent against these problems and without increasing the amount of existing metal corrosion inhibitors added. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Publication No. 5-222555 [Patent Document 2] Japanese Patent Application Publication No. 6-212459 [Patent Document 3] JP 2012-056874 A Summary of the Invention [Problem to be solved by the invention]

[0008] The present invention has been made in consideration of the above problems, and aims to provide a water treatment composition and a water treatment method that suppress metal corrosion in an aqueous system that requires the addition of an oxidizer, without reducing the effectiveness of the oxidizer as much as possible and without increasing the amount of metal corrosion inhibitor added. [Means for solving the problem]

[0009] In order to solve the above problems, the present inventors have conducted extensive research into a water treatment composition and a water treatment method that suppress metal corrosion in an aqueous system to which an oxidizing agent is added without decreasing the effectiveness of the oxidizing agent as much as possible and without increasing the amount of metal corrosion inhibitor added. As a result, the present inventors have found that the rate at which metal corrosion caused by the oxidizing agent progresses can be reduced by adding a nonionic surfactant together with the oxidizing agent added to the aqueous system, and have completed the present invention.

[0010] That is, the present invention relates to the following water treatment composition and water treatment method, although the present invention is not limited thereto. [1] A water treatment composition to be added to an aqueous system in contact with a metal, the water treatment composition comprising an oxidizing agent and a nonionic surfactant as a corrosion rate reducer. [2] The water treatment composition according to the above [1], wherein the nonionic surfactant has an HLB value of 8 to 16. [3] The water treatment composition according to the above [1] or [2], wherein the nonionic surfactant contains ethylene oxide and / or propylene oxide, an alkyl group, and an ether bond. [4] The water treatment composition according to any one of the above [1] to [3], wherein the nonionic surfactant is a polyoxyalkylene alkyl ether. [5] The composition for water treatment according to any one of the above [1] to [4], wherein the aqueous system contains a metal corrosion inhibitor. [6] The water treatment composition according to any one of the above [1] to [5], wherein the metal is copper or mild steel. [7] A water treatment method comprising adding an oxidizing agent and a nonionic surfactant as a corrosion rate reducer to an aqueous system in contact with a metal such that the oxidizing agent and the nonionic surfactant are mixed in the aqueous system. [8] The water treatment method according to the above [7], wherein the nonionic surfactant has an HLB value of 8 to 16. [9] The water treatment method according to the above [7] or [8], wherein the nonionic surfactant contains ethylene oxide and / or propylene oxide, an alkyl group, and an ether bond.

[10] The water treatment method according to any one of the above [7] to [9], wherein the nonionic surfactant is a polyoxyalkylene alkyl ether.

[11] The water treatment method according to any one of [7] to

[10] above, wherein the nonionic surfactant is added to the aqueous system so that the concentration of the nonionic surfactant in the aqueous system is 0.1 to 400 mg / L.

[12] The water treatment method according to any one of the above [7] to

[11] , wherein the aqueous system contains a metal corrosion inhibitor.

[13] The water treatment method according to any one of the above [7] to

[12] , wherein the metal is copper or mild steel. Effect of the Invention

[0011] According to the present invention, in an aqueous system that requires the addition of an oxidizing agent, metal corrosion in the aqueous system can be suppressed without reducing the effectiveness of the oxidizing agent as much as possible and without increasing the amount of metal corrosion inhibitor added. [Brief description of the drawings]

[0012] [Figure 1] FIG. 2 is a schematic diagram of a cooling water system used in the evaluation of metal corrosion damage in the examples. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] The present invention will be described in detail below.

[0014] The water treatment composition of the present invention is added to an aqueous system that comes into contact with metals, and contains an oxidizing agent and a nonionic surfactant as a corrosion rate reducer. The present inventors have found that when an oxidizing agent and a nonionic surfactant are added to an aqueous system, the metal corrosion rate (MDD) is significantly reduced compared to the metal corrosion rate (MDD) of an aqueous system to which only an oxidizing agent is added, and have completed the present invention. Here, as described above, when an oxidizing agent is added to an aqueous system, the presence of highly oxidizing residual chlorine in the system tends to increase metal corrosion. Therefore, in a system to which an oxidizing agent is added, the metal corrosion rate (MDD) increases, and even if a known metal corrosion inhibitor is used, its effect is insufficient. Although the detailed mechanism of the reduction of the corrosion rate increased by the addition of an oxidizing agent by the nonionic surfactant added to the aqueous system is not clear, the nonionic surfactant specified in the present invention can reduce the progress of metal corrosion caused by the oxidizing agent without reducing the effectiveness of the oxidizing agent in the aqueous system (for example, slime damage prevention effect, fouling prevention effect, etc.). Therefore, according to the present invention, it is possible to minimize the amount of oxidizing agent required to maintain the residual halogen concentration in the aqueous system, and it is believed that the effect of suppressing metal corrosion can be obtained even by reducing the amount of oxidizing agent used. Note that the present invention is not limited to the above mechanism.

[0015] The oxidizing agent used in the present invention can be one that is generally used for antibacterial, sterilizing, anti-slime treatment, etc. in the aqueous system by adding it to the aqueous system, and is not particularly limited as long as it generates residual halogen in the aqueous system. Examples of such oxidizing agents include hypochlorites such as chlorine, sodium hypochlorite, potassium hypochlorite, and calcium hypochlorite, chlorites such as sodium chlorite and potassium chlorite, chlorates such as sodium chlorate, potassium chlorate, and calcium chlorate, and perchlorates such as sodium perchlorate and calcium perchlorate. Examples of other oxidizing agents include hypobromites such as bromine, sodium hypobromites, potassium hypobromites, and calcium hypobromites, bromites such as sodium bromite and potassium bromite, bromates such as sodium bromate, potassium bromate, and calcium bromate, and perbromates such as sodium perbromate and calcium perbromate. Also usable are stabilized chlorine and stabilized bromine such as N-chlorosulfamate and N-bromosulfamate, chlorine dioxide, and bromine dioxide. Among these, hypochlorite and hypobromite have appropriate oxidizing properties and can be preferably used. As the oxidizing agent, one of known oxidizing agents or the above-mentioned suitable oxidizing agents can be used alone or in combination of two or more.

[0016] In the present invention, the nonionic surfactant as the corrosion rate reducer preferably has an HLB of 8 to 16. From the viewpoint of further improving the stability of the composition, the HLB of the nonionic surfactant as the corrosion rate reducer is more preferably 10 to 16, and even more preferably 12 to 16. If the HLB is 8 or less, the solubility in water is low, and if the HLB is more than 16, the surface tension reducing ability is low, and there is a possibility that the function expected as a surfactant is not fully exhibited. In addition, from the viewpoint of the mixability of the oxidizing agent and the nonionic surfactant as the corrosion rate reducer in the water system, the HLB of the nonionic surfactant is preferably 8 or more, and more preferably 10 or more. In addition, the upper limit of the HLB is more preferably 15.8, and even more preferably 15.5 or less.

[0017] In one or more embodiments, the "HLB (hydrophilic lipophilic balance)" in the present disclosure can be calculated using the following Griffin formula. HLB = 20 x (sum of hydrophilic moieties formula weights / molecular weight) However, with regard to the method of calculating HLB in this disclosure, when the structure of the hydrophilic portion of the nonionic surfactant contains propylene oxide and / or butylene oxide in addition to ethylene oxide, the sum of the formula weights of the hydrophilic portions is calculated from ethylene oxide only, and the molecular weight is calculated based on the molecular weight excluding propylene oxide and / or butylene oxide.

[0018] The nonionic surfactant as a corrosion rate reducer preferably contains ethylene oxide and / or propylene oxide, an alkyl group, and an ether bond. In one or a plurality of embodiments, examples of the nonionic surfactant containing ethylene oxide and / or propylene oxide, an alkyl group, and an ether bond include polyoxyethylene isodecyl ether (isodecyl ether EO), polyoxyethylene octylphenyl ether (octylphenyl ether EO), polyoxyethylene nonylphenyl ether (nonylphenyl ether EO), polyoxyethylene lauryl ether (lauryl ether EO), polyoxyethylene tridecyl ether (tridecyl ether EO), polyoxyethylene oxypropylene lauryl ether (lauryl ether EO / PO), polyoxyethylene oxypropylene tridecyl ether (tridecyl ether EO / PO), polyoxyethylene polyoxypropylene decyl ether (decyl ether EO / PO), polyoxyethylene cetyl ether, and polyoxyethylene stearyl ether. Furthermore, the nonionic surfactant serving as the corrosion rate reducer may be one whose hydrophilic portion contains ethylene oxide and / or polypropylene oxide, and may further contain butylene oxide. The nonionic surfactant serving as the corrosion rate reducer is preferably a polyoxyalkylene alkyl ether in which the hydrophilic portion contains ethylene oxide or a polyoxyalkylene chain containing ethylene oxide and the hydrophobic portion contains an alkyl group and an ether bond. Furthermore, the nonionic surfactant serving as the corrosion rate reducer is preferably polyoxyethylene octylphenyl ether (octylphenyl ether EO) and / or polyoxyethylene polyoxypropylene decyl ether (decyl ether EO / PO) among polyoxyalkylene alkyl ethers.

[0019] In addition, the water treatment composition of the present invention may be one in which the content of the oxidizing agent and the nonionic surfactant as a corrosion rate reducer is determined according to the water quality of the water system to which the composition for water treatment of the present invention is added. That is, the chlorine concentration required in the water system to which the composition for water treatment of the present invention is added is determined, and based on this, the content (parts by weight) of the oxidizing agent and the content (parts by weight) of the nonionic surfactant as a corrosion rate reducer can be determined relative to 100 parts by weight of the composition for water treatment of the present invention. This is because if the chlorine concentration required in the water system differs depending on the water quality of the water system to be treated, the required amount of the oxidizing agent to be added and the required amount of the nonionic surfactant as a corrosion rate reducer to be added also differ.

[0020] In the water treatment composition of the present invention, the blending ratio of the oxidizing agent to the nonionic surfactant as a corrosion rate reducer is preferably 1:1000 to 1000:1 in weight ratio (chlorine-equivalent weight of the oxidizing agent: weight of the corrosion rate reducer), more preferably 1:600 ​​to 600:1, even more preferably 200:1 to 1:200, and still more preferably 200:1 to 1:1. The chlorine-equivalent weight of the oxidizing agent is the weight calculated from the chlorine concentration or chlorine-equivalent concentration of the oxidizing agent added to the water system. In addition, the water treatment composition of the present invention may be determined by the blending weight ratio of the oxidizing agent and the nonionic surfactant as a corrosion rate reducer according to the water quality of the water system to which it is added. That is, the chlorine concentration required in the water system to which it is added is determined, and the blending weight ratio of the oxidizing agent and the nonionic surfactant as a corrosion rate reducer in the water treatment composition of the present invention can be determined based on this. This is because if the concentration of the oxidizing agent required in the water system to be treated differs depending on the water quality of the water system to be treated, the required amount of the nonionic surfactant as a corrosion rate reducer to be added also differs.

[0021] The aqueous system to which the water treatment composition of the present invention is added is in contact with a metal, and preferably contains a metal corrosion inhibitor. The metal may be at least one selected from the group consisting of iron, copper, and mild steel, and is preferably copper or mild steel, and more preferably copper.

[0022] The metal corrosion inhibitor contained in the water system to which the water treatment composition of the present invention is added, or contained or added to the water system in the water treatment method, may be a known metal corrosion inhibitor, and is not particularly limited. For example, metal corrosion inhibitors such as phosphates, phosphonates, polyphosphates, zinc salts, molybdates, and tungstates, as well as azole-based metal corrosion inhibitors such as benzotriazole, tolyltriazole, and mercaptobenzothiazole can be used, but are not limited thereto. Among them, in the present invention, it is preferable to use at least one selected from the group consisting of phosphates, phosphonates such as phosphonobutane tricarboxylates, and benzotriazole as the metal corrosion inhibitor. In addition, the metal corrosion inhibitor may be one of known metal corrosion agents or the above-mentioned suitable metal corrosion agents, either alone or in combination of two or more.

[0023] The water treatment composition of the present invention may contain agents having other functions, for example, scale inhibitors, dispersants, stripping agents, defoamers, chelating agents, etc., as long as the effects of the present invention are not impaired. In the water treatment composition of the present invention, one of these other blending components may be used alone, or two or more of them may be used in combination.

[0024] The water system in which the water treatment composition and the water treatment method of the present invention are used is preferably one that requires antibacterial treatment, sterilization treatment, and slime prevention treatment with an oxidizing agent.

[0025] Moreover, the water system in which the water treatment composition and water treatment method of the present invention are used is preferably one in which a high level of metal corrosion prevention is required, and is preferably one in which the metal corrosion rate (MDD) is 100 mdd or less, more preferably one in which the metal corrosion rate (MDD) is 50 mdd or less, even more preferably one in which the metal corrosion rate (MDD) is 22 mdd or less, and even more preferably one in which the metal corrosion rate (MDD) is 5 mdd or less. The water treatment composition and water treatment method of the present invention are preferably used for water systems in which a known metal corrosion inhibitor is already used, but the effect of the metal corrosion inhibitor has become insufficient due to the addition of an oxidizing agent, because such water systems have a low metal corrosion rate (MDD) due to the use of a metal corrosion inhibitor.

[0026] The present invention is also a water treatment method characterized in that an oxidizing agent and a nonionic surfactant as a corrosion rate reducer are added to an aqueous system in contact with a metal so that the oxidizing agent and the nonionic surfactant are mixed in the aqueous system. By adding the oxidizing agent and the nonionic surfactant to the aqueous system so that they are mixed, the progress of metal corrosion caused by the oxidizing agent can be reduced without reducing the effectiveness of the oxidizing agent in the aqueous system (e.g., slime damage prevention effect, fouling prevention effect, etc.). Therefore, according to the present invention, the amount of oxidizing agent required to maintain the residual chlorine concentration in the aqueous system can be minimized, and it is believed that the effect of suppressing metal corrosion can be obtained even by reducing the amount of oxidizing agent used. The present invention also includes a water treatment method in which the above-mentioned water treatment composition of the present invention is added to an aqueous system in contact with a metal.

[0027] The oxidizing agent and the nonionic surfactant as the corrosion rate reducer used in the water treatment method of the present invention, and their preferred embodiments are the same as those of the water treatment composition of the present invention described above. In addition, the preferred embodiments of the water system targeted by the water treatment method of the present invention are also the same as those of the water system to which the water treatment composition of the present invention is applied.

[0028] In the water treatment method of the present invention, it is preferable to add the nonionic surfactant to the water system so that the concentration of the nonionic surfactant in the water system is 0.01 to 400 mg / L. It is also preferable to add the water treatment composition of the present invention to the water system so that the concentration of the nonionic surfactant in the water system is 0.01 to 400 mg / L. If the concentration of the nonionic surfactant in the water system exceeds 400 mg / L, the action of the metal corrosion inhibitor added to the water system may be inhibited, and if the concentration of the nonionic surfactant in the water system is less than 0.01 mg / L, the corrosion rate reducing effect of the nonionic surfactant may not be sufficiently obtained. In the water treatment method of the present invention, it is more preferable to add the nonionic surfactant as a corrosion rate reducer or the water treatment composition of the present invention to the water system so that the concentration of the nonionic surfactant in the water system is 0.01 to 100 mg / L, and it is even more preferable to add the nonionic surfactant as a corrosion rate reducer or the water treatment composition of the present invention to the water system so that the concentration of the nonionic surfactant in the water system is 0.1 to 20 mg / L.

[0029] In the water treatment method of the present invention, it is preferable to add the above-mentioned oxidizing agent or the water treatment composition of the present invention to the water system so that the residual chlorine concentration in the water system is 0.01 to 10 mg / L. This is because the water treatment method of the present invention suppresses metal corrosion in the water system without reducing the effect of the oxidizing agent on the water system, i.e., the bactericidal, antibacterial, and antislime effects as much as possible. In the water treatment method of the present invention, it is preferable to add the oxidizing agent or the water treatment composition of the present invention to the water system so that the residual chlorine concentration in the water system is preferably 0.01 to 5 mg / L, more preferably 0.05 to 1 mg / L, even more preferably 0.1 to 1 mg / L, and even more preferably 0.1 to 0.5 mg / L. In the present disclosure, the residual chlorine concentration can be read as a residual chlorine equivalent concentration. The residual chlorine equivalent concentration is a value obtained by converting the residual chlorine concentration in an oxidizing agent having a halogen.

[0030] In the water treatment method of the present invention, a one-liquid preparation containing an oxidizing agent and a nonionic surfactant as a corrosion rate reducer (i.e., the water treatment composition of the present invention) may be added to the target water system, or a single preparation containing an oxidizing agent or a single preparation containing a nonionic surfactant as a corrosion rate reducer may be added separately. When the oxidizing agent and the nonionic surfactant as a corrosion rate reducer are added separately to the water system, the order and position of addition are not particularly limited as long as the oxidizing agent and the nonionic surfactant are added so as to be mixed in the water system.

[0031] In the water treatment method of the present invention, when an oxidizing agent is added to the upstream side of a water system and a nonionic surfactant is added to the downstream side as a corrosion rate reducer, the nonionic surfactant is preferably added to a water system having a residual chlorine concentration of 0.01 to 10 mg / L. It is also preferable to add the nonionic surfactant to the water system so that the concentration of the nonionic surfactant in the water system having a residual chlorine concentration of 0.01 to 10 mg / L is 0.01 to 400 mg / L. In this case, the mode of addition of the oxidizing agent to the upstream side of the water system is not limited, and may be continuous addition or single addition, and it is preferable that the residual chlorine concentration at the position where the nonionic surfactant is added to the water system as a corrosion rate reducer is in the above range. In the water treatment method of the present invention, when an oxidizing agent is added to the upstream side of a water system and a nonionic surfactant is added to the downstream side as a corrosion rate reducer, the residual chlorine concentration in the water system to which the nonionic surfactant is added and the concentration of the nonionic surfactant added to the water system can be suitably combined to obtain a suitable embodiment by appropriately combining the suitable range of the residual chlorine concentration and the suitable range of the nonionic surfactant concentration in the water system in the water treatment method of the present invention described above.

[0032] In the water treatment method of the present invention, when a nonionic surfactant is added as a corrosion rate reducer on the upstream side of the water system and an oxidizing agent is added on the downstream side, the oxidizing agent is preferably added to a water system in which the concentration of the nonionic surfactant is 0.01 to 400 mg / L. It is also preferable to add the oxidizing agent to the water system so that the residual chlorine concentration of the oxidizing agent in the water system in which the concentration of the nonionic surfactant is 0.01 to 400 mg / L is 0.01 to 10 mg / L. In this case, the addition mode of the nonionic surfactant as a corrosion rate reducer on the upstream side of the water system is not limited, and may be continuous addition or single addition, and it is preferable that the concentration of the nonionic surfactant at the position where the oxidizing agent is added to the water system is in the above range. In the water treatment method of the present invention, when a nonionic surfactant is added as a corrosion rate reducer to the upstream side of the water system and an oxidizing agent is added to the downstream side, the concentration of the nonionic surfactant in the water system to which the oxidizing agent is added and the concentration of the oxidizing agent added to the water system can be suitably combined to a suitable embodiment by appropriately combining the suitable range of residual chlorine concentration and the suitable range of nonionic surfactant concentration in the water system in the water treatment method of the present invention described above.

[0033] In the water treatment method of the present invention, the manner of addition and the method of management of the oxidizing agent added to the water system are not particularly limited. For example, the manner of addition of the oxidizing agent may be continuous addition as described above, or single addition (intermittent addition or batch addition). In addition, the method of managing the addition of the oxidizing agent may be by measuring the residual chlorine concentration and the redox potential. In this case, the residual chlorine concentration can be measured by a known method, for example, the DPD method or a residual chlorine meter can be used. In addition, the redox potential can also be measured by a known method, for example, a redox potentiometer can be used. In addition, the manner of addition and the method of management of the nonionic surfactant added to the aqueous system are not particularly limited. For example, the manner of addition of the nonionic surfactant may be continuous addition as described above, or single addition (intermittent addition or batch addition). In addition, the method of managing the addition of the nonionic surfactant can be such that the concentration of the nonionic surfactant in the aqueous system is within the above-mentioned preferred range.

[0034] In the water treatment method of the present invention, the water system preferably contains a metal corrosion inhibitor. The position where the metal corrosion inhibitor is added to the water system is not particularly limited, and the metal corrosion inhibitor may be added upstream of or at the same location as the location where the oxidizing agent and the nonionic surfactant as a corrosion inhibitor are added to the water system so as to be mixed. The metal oxidizing agent and preferred embodiments thereof in the water treatment method of the present invention are the same as the oxidizing agent and preferred embodiments thereof in the water treatment composition of the present invention described above.

[0035] When the water system to be treated by the water treatment composition and water treatment method of the present invention is a circulating type such as a circulating cooling water system, the water pump that sends water from a water tank of the circulating water system is regarded as the starting point of the circulating water system, and the position of water sent from the water pump that is closest to the water pump is regarded as the upstream side. Also, the water tank of the circulating water system is regarded as the downstream side of the water system, and the piping for transporting water from the water tank to the water pump is regarded as the most downstream side. EXAMPLES

[0036] Examples and comparative examples are shown below, but the present invention is not limited to the following examples.

[0037] <Corrosion test 1> In the following tests, the metal corrosion test method of the water treatment agent in the test example was in accordance with the test method of JIS G 0593 "Test method for evaluating corrosion and scale prevention of water treatment agents." Figure 1 is a schematic diagram of the cooling water system used in the evaluation of metal corrosion damage. As the test tube 1, a copper tube (JIS H 3100 C1100) and a mild steel tube (JIS G 3445 STKAM11A) having an outer diameter of 12.7 mm, a wall thickness of 1.2 mm, and a length of 510 mm were used. The test results using the copper tube as the test tube 1 are shown in Table 2 below, and the test results using the mild steel tube as the test tube 1 are shown in Table 3 below.

[0038] Industrial water from a certain chemical factory A was circulated through a test device equipped with a cooling tower and heat exchanger, and concentrated until it reached the desired electrical conductivity (52-55 mS / m), creating approximately six-fold concentrated water, which was then used as the test water for the test. The metal corrosion inhibitors shown below were added to the test water to prepare the concentrations shown below. The prepared test water was maintained at 33° C. in the test water pit 5. Using a circulation pump 3, the test water was circulated from the test water pit 5 through the test column 2 to the cooling tower 4 and the test water pit 5. A test tube in direct contact with the test water was placed in the column, with the test water placed on the outside of the test tube and a heater as a heat source placed on the inside. During the test, the electrical conductivity was controlled at 52-55mS / m, and make-up water was added to make up for any shortage. The make-up water was industrial water from a certain factory that was used in the process of making the test water. The quality of the make-up water is shown in Table 1 below. The metal corrosion inhibitor concentrations remained constant (ie, the concentrations shown below) throughout the test period. For the water treatment agent according to the test example, hypochlorous acid or hypobromous acid, which is an oxidizing agent, the residual chlorine concentration in the test water pit 5 was continuously measured using a residual chlorine meter (RM-52, manufactured by TACMINA, not shown), and appropriate addition was made so that the residual chlorine concentration in the test water was 0.3 mg / L. Even when hypobromous acid was used as the oxidizing agent, the measurement value of the residual chlorine meter was displayed in chlorine equivalent. Hereinafter, the concentration of hypobromous acid in the test water will be expressed in chlorine equivalent. As the oxidizing agent, sodium hypochlorite was used for hypochlorous acid, and hypobromous acid was generated by reacting sodium hypochlorite and sodium bromide in equimolar amounts and used. As the water treatment agent in the test example, a nonionic surfactant, which is a corrosion rate reducer, was added appropriately so that the average concentration in the test water became the concentrations shown in Tables 2 and 3 below. The temperature of the test water in the test water pit 5 was set to 33°C, the linear flow rate of the test water in the test tube was set to 0.5 m / s, and the heater temperature in the test tube was set to 90°C. The test was run for 7 days with each set. The number of bacteria during the test period was measured using a biochecker (manufactured by San-ai Oburi Co., Ltd., not shown in the figure) and was less than 1000 CFU / mL in all test plots. After the test, the test tube was removed and the weight change of the test tube before and after the test was measured in accordance with JIS K0100-1990 to determine the corrosion rate of the test tube (weight loss per day, MDD, mg / day dm 2 The results are shown in Tables 2 and 3.

[0039] [Table 1]

[0040] (Oxidizing agent) The following commercially available reagents were added so that the drug concentrations in the aqueous system became the concentrations shown in Tables 2 and 3 below. Sodium hypochlorite (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) Sodium bromide (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) (Nonionic surfactant) The following commercially available reagents were added so that the drug concentrations in the aqueous system became the concentrations shown in Table 2 below. Polyoxyethylene polyoxypropylene decyl ether (Decyl ether EO / PO) (HLB13.8) Polyoxyethylene octylphenyl ether (Octylphenyl ether EO) (HLB15.5) (Metal corrosion inhibitor) The following commercially available reagents were added so that the drug concentrations in the aqueous system were as follows: Phosphoric acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) 4.6 [mg / L] Zinc (zinc chloride, Fujifilm Wako Pure Chemical Industries, Ltd.) 3.3 mg / L PBTC (2-phosphonobutane-1,2,4-tricarboxylic acid, manufactured by Tokyo Chemical Industry Co., Ltd.) 1.6 [mg / L] Benzotriazole (Fujifilm Wako Pure Chemical Industries, Ltd.) 2.9 [mg / L]

[0041] [Table 2] *The hypochlorous acid concentration is listed as a chlorine equivalent concentration.

[0042] [Table 3] *The hypochlorous acid concentration is listed as a chlorine equivalent concentration.

[0043] From the results in Table 2 above, in the test example according to Example 1 in which polyoxyethylene octylphenyl ether was added as a corrosion rate reducer, and in the test examples according to Examples 2 to 4 in which polyoxyethylene polyoxypropylene decyl ether was added as a corrosion rate reducer, the corrosion rate MDD in the copper pipe was reduced by 30% or more compared to Comparative Examples 1 and 2 which did not contain a corrosion rate reducer. Furthermore, even when polyoxyethylene octylphenyl ether or polyoxyethylene polyoxypropylene decyl ether was added as a corrosion rate reducer, the number of bacteria in the water was less than 1000 CFU / mL in the test examples according to Examples 1 to 4, and the amount of hypochlorous acid used (amount of sodium hypochlorite used) did not increase, but rather the amount of hypochlorous acid used decreased, confirming that the effect of the oxidizing agent in the test water was fully exerted while the amount of oxidizing agent used was reduced. In addition, the amount of metal corrosion inhibitor added was constant in all test plots in Examples 1 to 6 and Comparative Examples 1 to 3. The concentration of hypochlorous acid added was recorded as a chlorine equivalent concentration.

[0044] From the results of Table 3 above, in the test example according to Example 5 in which polyoxyethylene octylphenyl ether was added as a corrosion rate reducer, and in the test example according to Example 6 in which polyoxyethylene polyoxypropylene decyl ether was added as a corrosion rate reducer, the corrosion rate MDD in the mild steel pipe was reduced by 25% or more compared to Comparative Example 3 in which no polyoxyethylene octylphenyl ether was included. Furthermore, even when polyoxyethylene octylphenyl ether or polyoxyethylene polyoxypropylene decyl ether was added as a corrosion rate reducer, the number of bacteria in the water was less than 1000 CFU / mL in the test examples according to Examples 5 and 6, and the amount of hypochlorous acid used did not increase, but rather decreased, confirming that the effect of the oxidizing agent in the test water was fully exerted while the amount of oxidizing agent used was reduced.

[0045] <Corrosion test 2> A copper test piece measuring 1.0 mm x 30 mm x 50 mm was prepared and fixed in the cooling tower pit of a certain chemical factory B during operation, and the corrosion rate was measured during the test period. The copper test piece was measured using (JIS H 3100 C1100). The corrosion rate of copper (corrosion weight loss per day, MDD, mg / day dm 2 ) was measured in accordance with JIS K0100-1990 and was evaluated by measuring the change in weight of the test piece before and after the test. The metal corrosion inhibitor, oxidizing agent, and corrosion rate reducer used in the cooling water system, and their concentrations, are shown in Table 5 below, and the details of the agents are as shown in Corrosion Test 1. The metal corrosion inhibitor, oxidizing agent, and corrosion rate reducer were all added in the cooling pit. The test period for all test examples shown in Table 5 below was 10 days.

[0046] The water quality (average water quality during the test period) of the cooling water system water (water in the cooling tower pit) during the test period is as shown in Table 4 below. The water temperature in the cooling tower pit fluctuated between 32 and 34°C, and the retention time was approximately 30 hours. The number of bacteria during the test period was measured using a biochecker (manufactured by San-ai Obri Co., Ltd.) and was less than 1000 CFU / mL.

[0047] [Table 4]

[0048] [Table 5]

[0049] From the results of Example 7 and Comparative Example 4 in Table 5 above, the corrosion rate MDD of the test piece in Example 7, in which polyoxyethylene polyoxypropylene decyl ether (decyl ether EO / PO) was added as a corrosion rate reducer in the concentration range of 0.18 to 0.35 mg / L and sodium hypochlorite was added as an oxidizing agent so that the residual chlorine concentration was in the range of 0.1 to 1.0 mg / L, was reduced by about 30% compared to the corrosion rate MDD of the test piece in Comparative Example 4, in which only the oxidizing agent was added at the same concentration and no corrosion rate reducer was added. Furthermore, in both Comparative Example 4 and Example 7, the number of bacteria in the water was less than 1000 CFU / mL, and in Example 7, the corrosion rate MDD could be reduced without suppressing the effect of the oxidizing agent. The amounts of the metal corrosion inhibitor added in Example 7 and Comparative Example 4 were the same. [Explanation of symbols]

[0050] 1 test tube 2 Test column 3 Circulation pump 4 cooling tower 5. Test water pit 6. Electrical conductivity control device 7. Conductivity measuring cell 8 Flow meter 9. Water treatment agent injection device

Claims

1. A water treatment composition added to an aqueous system in contact with a metal, comprising: A water treatment composition comprising an oxidizing agent and a nonionic surfactant as a corrosion rate reducing agent.

2. 2. The water treatment composition according to claim 1, wherein the HLB of the nonionic surfactant is 8 to 16.

3. 3. The water treatment composition according to claim 1, wherein the nonionic surfactant contains ethylene oxide and / or propylene oxide, an alkyl group and an ether bond.

4. 3. The water treatment composition according to claim 1, wherein the nonionic surfactant is a polyoxyalkylene alkyl ether.

5. The water treatment composition according to claim 1 or 2, wherein the aqueous system contains a metal corrosion inhibitor.

6. 3. The water treatment composition according to claim 1, wherein the metal is copper or mild steel.

7. A water treatment method comprising adding an oxidizing agent and a nonionic surfactant as a corrosion rate reducer to an aqueous system in contact with a metal, so that the oxidizing agent and the nonionic surfactant are mixed in the aqueous system.

8. The water treatment method according to claim 7, wherein the HLB of the nonionic surfactant is 8 to 16.

9. 9. The water treatment method according to claim 7, wherein the nonionic surfactant contains ethylene oxide and / or propylene oxide, an alkyl group, and an ether bond.

10. 9. The water treatment method according to claim 7 or 8, wherein the nonionic surfactant is a polyoxyalkylene alkyl ether.

11. 9. The water treatment method according to claim 7, wherein the nonionic surfactant is added to the aqueous system so that the concentration of the nonionic surfactant in the aqueous system is 0.1 to 400 mg / L.

12. The water treatment method according to claim 7 or 8, wherein the aqueous system contains a metal corrosion inhibitor.

13. 9. The water treatment method according to claim 7 or 8, wherein the metal is copper or mild steel.

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