Flux removal agent and method for removing flux

Abstract

To provide a flux removal agent that enables effective removal of flux existing on an aluminum-based metallic material such as a heat exchanger and that is advantageous for imparting excellent resistance to re-elution to the aluminum-based metallic material following flux removal.SOLUTION: A flux removal agent comprises an oxoacid and / or a salt thereof (A) and a surfactant (B), the flux removal agent having a pH of 2 or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a flux remover and a flux removal method. [Background technology]

[0002] Heat exchangers are installed in automobiles and other vehicles as radiators, intercoolers, evaporators, etc. In recent years, heat exchangers have often been constructed with a tank section consisting of a base plate and a tank cover attached to both ends of a stack of alternately stacked tubes and corrugated fins. Such heat exchangers are generally manufactured by brazing using the Nocolok flux method.

[0003] Heat exchangers manufactured using the Nocolok flux method retain some residual flux. Recently, it has become clear that residual flux can adversely affect the performance of heat exchangers. For example, polymer electrolyte membrane fuel cell systems have been developed for fuel cell electric vehicles (FCEVs) equipped with fuel cells as their driving sources. These systems are configured to protonate hydrogen fuel in the fuel cell stack through the action of a proton catalyst supported on a polymer electrolyte membrane, which then generates electric potential in cooperation with oxygen present across the membrane. These fuel cell systems use a heat exchanger through which a refrigerant is circulated to maintain the fuel cell at an optimal temperature due to the heat generated during power generation. In these fuel cell systems, the water-containing refrigerant circulating through the heat exchanger directly contacts the proton catalyst. Therefore, if flux remains at the joints between the heat exchanger tubes and base plate or inside the tubes, metal ions or other substances may be mixed into the refrigerant, potentially poisoning the catalyst.

[0004] In contrast to this, Patent Document 1 discloses a technology in which vacuum brazing is performed in a high-temperature vacuum furnace without using flux (vacuum method), and then the inside of the tube and tank is washed with pure water or ethylene glycol liquid at 70°C or higher.

[0005] Furthermore, Patent Document 2 proposes a method for removing residual flux after a brazing process, which combines an alkali cleaning process, an acid cleaning process, a physical treatment process for physically removing residual flux, and a warm pure water cleaning process. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-233011 [Patent Document 2] Japanese Patent Application Laid-Open No. 2009-301997 Summary of the Invention [Problem to be solved by the invention]

[0007] However, compared to brazing methods that use flux, the vacuum method described in Patent Document 1, which does not use flux, has some concerns, such as expensive equipment, slightly inferior brazing properties, and the tendency for Zn contained in the base material to evaporate, which can cause a decrease in strength and corrosion resistance. Therefore, there is a growing demand for a technology that allows brazing to be performed using flux but that can then be removed.

[0008] The residual flux removal method described in Patent Document 2 aims to remove flux by combining an alkaline cleaning process, an acid cleaning process, a physical treatment process for physically removing residual flux, and a warm pure water cleaning process. However, the alkaline cleaning process and the acid cleaning process are essential to achieve good performance. In addition, there are many work steps, many of which require expensive equipment, and cleaning takes a long time. There is no specific explanation about the condition of the inner surface after cleaning or resistance to re-elution.

[0009] Therefore, in one embodiment, the present invention aims to provide a flux remover that can effectively remove flux present on aluminum-based metallic materials such as heat exchangers and that is advantageous in imparting excellent resistance to re-elution to the aluminum-based metallic materials after flux removal. In another embodiment, the present invention aims to provide a flux removal method. [Means for solving the problem]

[0010] The present inventors have found that flux can be efficiently removed by bringing a predetermined flux remover into contact with an aluminum-based metallic material from which flux is present, and that the flux remover is advantageous in imparting excellent resistance to re-elution to the aluminum-based metallic material after flux removal, and have thus completed the present invention, which is exemplified below.

[0011] [1] A flux remover comprising an oxoacid and / or a salt thereof (A) and a surfactant (B), and having a pH of 2 or less. [2] The flux remover according to [1], wherein the oxoacid and / or salt thereof (A) comprises one or more selected from nitric acid, sulfuric acid, sulfurous acid, nitrous acid, and salts thereof. [3] The flux remover according to [1] or [2], wherein the surfactant (B) includes one or both of a nonionic surfactant and a cationic surfactant. [4] The flux remover according to any one of [1] to [3], which has a surface tension of 20 to 55 mN / m. [5] The flux remover according to any one of [1] to [4], wherein the surfactant (B) contains one or both of a nonionic surfactant and a cationic surfactant, and has a surface tension of 20 to 55 mN / m. [6] A method for removing flux, comprising the step (i) of contacting an aluminum-based metal material to which flux has adhered with a flux remover containing an oxoacid and / or a salt thereof (A) and a surfactant (B) and having a pH of 2 or less. [7] The flux removal method according to [6], wherein the oxoacid and / or salt thereof (A) comprises one or more selected from nitric acid, sulfuric acid, sulfurous acid, nitrous acid, and salts thereof. [8] The flux removal method according to [6] or [7], wherein the surfactant (B) includes one or both of a nonionic surfactant and a cationic surfactant. [9] The method for removing flux according to any one of [6] to [8], wherein the surface tension is 20 to 55 mN / m.

[10] The flux removal method according to any one of [6] to [9], wherein the surfactant (B) contains one or both of a nonionic surfactant and a cationic surfactant, and has a surface tension of 20 to 55 mN / m.

[11] The method for removing flux according to any one of [6] to

[10] , wherein the temperature of the flux remover is 60°C or higher and lower than 100°C.

[12] The flux removal method according to any one of [6] to

[11] , further comprising, after the step (i), a step (ii) of washing the aluminum-based metallic material with deionized water having an electrical conductivity of 2 μS / cm or less.

[13] The flux removal method according to any one of [6] to

[12] , wherein the aluminum-based metallic material is a heat exchanger or a part thereof.

[14] The flux removal method according to any one of [6] to

[13] , wherein the step (i) involves passing the flux remover through a tube of a heat exchanger at a linear velocity (LV) of 1000 m / Hr or more.

[15] The method for removing flux according to

[12] or

[13] or

[14] dependent on

[12] , wherein the step (ii) involves passing deionized water having an electrical conductivity of 2 μS / cm or less through the tubes of the heat exchanger at a linear velocity (LV) of 200 m / Hr or more.

[16] The flux removal method according to any one of

[12] to

[15] , comprising a step (iii) between the step (i) and the step (ii) or after the step (ii), of drying the aluminum-based metallic material in an oxygen-containing gas atmosphere at an atmospheric temperature of 80°C or higher for 0.5 hours or more.

[17] Between the steps (i) and (ii) or after the step (ii), the amount of K element measured on the surface of the aluminum-based metal material by X-ray fluorescence analysis (XRF) is 15 mg / m 2 The flux removal method according to any one of

[12] to

[15] below.

[18] The flux removal method according to

[16] or

[17] , wherein, after the step (iii), the X-ray intensity of O element when the surface of the aluminum-based metallic material is measured by X-ray fluorescence spectroscopy (XRF) is 0.01 kcps or more. [Effects of the Invention]

[0012] According to one embodiment of the present invention, a flux remover can be provided that can effectively remove flux present on aluminum-based metal materials such as heat exchangers and that is advantageous for imparting excellent re-elution resistance to the aluminum-based metal materials after flux removal. According to another embodiment of the present invention, a flux removal method can be provided. The flux remover or flux removal method contributes to maintaining the quality of, for example, heat exchangers in which aluminum-based metals are used. DETAILED DESCRIPTION OF THE INVENTION

[0013] (1. Deflux remover) A flux remover according to one embodiment of the present invention includes an oxoacid and / or a salt thereof (A) and a surfactant (B). The flux remover can be provided in the form of a liquid typically containing water as a solvent or dispersion medium, and more typically in the form of an aqueous solution.

[0014] <Oxoacid and / or salt thereof (A)> A flux remover according to one embodiment of the present invention includes an oxo acid and / or a salt thereof (A). In this specification, the oxo acid (A) refers to a compound in which a hydroxy group (—OH) and an oxo group (═O) are bonded to some atom, and the hydroxy group can donate a proton. The oxo acid (A) does not include acqua acid or hydroxo acid. The oxo acid (A) is not particularly limited, and examples thereof include sulfuric acid, oleum, sulfurous acid, sulfonic acid, sulfinic acid, nitric acid, nitrous acid, hypochlorous acid, hypobromous acid, hypoiodous acid, and organic carboxylic acids. Examples of sulfonic acids that can be used include chlorosulfonic acid and benzenesulfonic acid. Examples of sulfinic acids that can be used include benzenesulfinic acid. The oxo acid (A) may be used as is or in the form of a salt such as an ammonium salt or a sodium salt. The oxo acid and / or salt thereof (A) may be used alone or in combination of two or more. Among these, it is preferable to use one or more selected from sulfuric acid, sulfurous acid, nitric acid, nitrous acid, and salts thereof.

[0015] The total content of the oxo acid and / or salt thereof (A) in the flux remover is not particularly limited, but is preferably, for example, from 1% by mass to 20% by mass, and more preferably from 5% by mass to 10% by mass.

[0016] <Surfactant (B)> A defluxing agent according to one embodiment of the present invention contains a surfactant (B). The surfactant (B) is not particularly limited, but may be a nonionic surfactant, a cationic surfactant, an anionic surfactant, or the like. It is more preferable to use one or both of a nonionic surfactant and a cationic surfactant. The surfactant (B) may be used alone or in combination of two or more.

[0017] The nonionic surfactant is not particularly limited, but it is preferable to use one with an HLB of 7 or higher. Examples of nonionic surfactants include polyoxyalkylene alkyl ethers. Examples of polyoxyalkylene alkyl ethers that can be used include polyoxyalkylene isodecyl ether, polyoxyalkylene tridecyl ether, and polyoxyalkylene lauryl ether. The polyoxyalkylene chain contained in the polyoxyalkylene alkyl ethers can be composed of a polyoxyethylene chain, a polyoxypropylene chain, or a combination thereof. Examples of polyoxyalkylene alkyl ethers that can be used include polyoxyethylene alkyl ethers. Examples of polyoxyethylene alkyl ethers that can be used include polyoxyethylene isodecyl ether, polyoxyethylene lauryl ether, polyoxyethylene oleyl cetyl ether, and polyoxyethylene tridecyl ether.

[0018] The cationic surfactant is not particularly limited, but examples thereof include quaternary ammonium salts. Examples of quaternary ammonium salts that can be used include monoalkyl quaternary ammonium salts, monoalkyl ether quaternary ammonium salts, dialkyl quaternary ammonium salts, dialkyl ester quaternary ammonium salts, and benzalkonium quaternary ammonium salts. Examples of monoalkyl quaternary ammonium salts that can be used include cetrimonium chloride, steartrimonium chloride, behentrimonium chloride, steartrimonium bromide, cetrimonium methosulfate, and behentrimonium methosulfate. Examples of monoalkyl ether quaternary ammonium salts that can be used include stearoxypropyltrimonium chloride and behenyl PG trimonium chloride. Examples of dialkyl-type quaternary ammonium salts that can be used include distearyldimonium chloride, dicocodimonium chloride, dialkyl (C12-C18)dimonium chloride, and quaternium-18. Examples of dialkyl ester-type quaternary ammonium salts that can be used include dicocoyl ethyl hydroxyethylmonium methosulfate and distearoyl ethyl hydroxyethylmonium methosulfate. Examples of benzalkonium-type quaternary ammonium salts that can be used include benzalkonium chloride.

[0019] The anionic surfactant is not particularly limited, but examples thereof include sulfate ester surfactants, phosphate ester surfactants, carboxylic acid surfactants, and sulfonic acid surfactants, and among these, sulfonic acid surfactants are preferably used. Examples of sulfonic acid surfactants that can be used include sodium alkyl sulfonate, sodium alkyl benzene sulfonate, sodium alkyl naphthalene sulfonate, sodium dialkyl sulfosuccinate, sodium alkyl diphenyl ether disulfonate, and sodium alkyl glyceryl ether sulfonate.

[0020] The content of the surfactant (B) contained in the flux remover is not particularly limited, but is preferably 0.01% by mass or more and 10% by mass or less, and more preferably 0.1% by mass or more and 5% by mass or less.

[0021] <pH of the flux remover> The defluxing agent according to one embodiment of the present invention has a pH of 2 or less, and more preferably a pH of 1.5 or less. If the pH exceeds 2, the cleaning time tends to be longer, resulting in poor productivity. Furthermore, if the pH exceeds 2, excess ions accumulate in the defluxing agent, and the persistence of ion dissolution tends to decrease. While there is no set lower limit for the pH, it is usually -0.5 or more, and typically -0.2 or more. Therefore, the pH of the defluxing agent is preferably, for example, -0.5 or more and 2 or less, and more preferably -0.2 or more and 1.5 or less. In this specification, pH refers to the pH at 25°C.

[0022] <Surface tension of flux remover> From the viewpoint of surfactant performance, the defluxing agent according to one embodiment of the present invention preferably has a surface tension of 20 mN / m or more, and more preferably 25 mN / m or more. Furthermore, from the viewpoint of wettability of aluminum-based metallic materials, the defluxing agent according to one embodiment of the present invention preferably has a surface tension of 55 mN / m or less, and more preferably 40 mN / m or less. Therefore, the defluxing agent according to one embodiment of the present invention preferably has a surface tension of 20 mN / m or more and 55 mN / m or less, and more preferably 25 mN / m or more and 40 mN / m or less. In this specification, the surface tension refers to a value measured at 25°C by the Wilhelmy method.

[0023] (2. How to remove flux) <Process (i)> A flux removal method according to one embodiment of the present invention includes step (i) of contacting the above-described flux remover with an aluminum-based metallic material to which flux has adhered. For example, flux is adhered to a brazed portion of an aluminum-based metallic material. The method of contacting the aluminum-based metallic material with the flux remover is not particularly limited, and may include, for example, immersing the aluminum-based metallic material in the flux remover, or spraying or pouring the flux remover onto the aluminum-based metallic material. Two or more of these methods may be combined.

[0024] Although there are no particular limitations on the type of flux attached to aluminum-based metal materials, it is common for the flux to be used in brazing aluminum-based metal materials. Such fluxes are generally non-corrosive K-based fluorides (potassium fluoroaluminate complex salts such as KAlF4). Because the flux is in powder form, it is often applied to the surface of the aluminum-based metal material as a water-soluble flux (water + KAlF4) or flux paint (water (solvent) + KAlF4 + binder). Resins such as acrylic resins, urethane resins, or elastomer resins are preferably used as binders.

[0025] In step (i), the contact time of the flux remover with the aluminum-based metallic material is preferably longer, since this increases the flux removal efficiency. The lower limit of this time is preferably 3 minutes or more, more preferably 5 minutes or more, and even more preferably 10 minutes or more. On the other hand, there is no particular upper limit to this time, but from the viewpoint of production efficiency, it is preferably 60 minutes or less, more preferably 30 minutes or less, and even more preferably 20 minutes or less. Therefore, in step (i), the contact time of the flux remover with the aluminum-based metallic material is, for example, preferably 3 minutes or more and 60 minutes or less, more preferably 5 minutes or more and 30 minutes or less, and even more preferably 10 minutes or more and 20 minutes or less.

[0026] Examples of aluminum-based metal materials include aluminum and aluminum alloys. For example, JIS H4000:2022 1000 series (pure aluminum) aluminum can be used. For example, 3000 series (aluminum-manganese (Al-Mn) alloys), 4000 series (aluminum-zinc (Al-Si) alloys), 5000 series (aluminum-magnesium (Al-Mg) alloys), and 7000 series (aluminum-zinc-magnesium (Al-Zn-Mg) alloys) can be used. When the aluminum-based metal material is a heat exchanger as described below, the inner surfaces of its tubes, plates, corrugated fins, and tank may be clad with the aluminum or aluminum alloy.

[0027] The temperature of the defluxing agent in step (i) is not particularly limited, but is preferably 60°C or higher but lower than 100°C, more preferably 70°C or higher but lower than 100°C, and even more preferably 80°C or higher but lower than 95°C. If the temperature of the defluxing agent is lower than 60°C, the removability tends to be poor, the removal time tends to be too long, and productivity tends to be poor. If the temperature of the defluxing agent is higher than 100°C (if it boils), air inhibits liquid circulation, reducing surface contact efficiency and decreasing removal efficiency.

[0028] The application of the aluminum-based metal material is not particularly limited, and in one embodiment, it may be a heat exchanger or a part thereof. The heat exchanger is not particularly limited, and for example, a fin-tube heat exchanger or the like can be used. Examples of heat exchanger parts include tubes, plates, corrugated fins, and tanks, as well as clad materials that form the inner surfaces of these parts. In a fin-tube heat exchanger, flux adheres to the inner surfaces of the tubes as well as to brazed parts in general, such as the brazed part between the tank and core plate and the brazed part between the tank and pipe.

[0029] When the aluminum-based metallic material is a heat exchanger, the step (i) may involve passing the flux removing agent through the tubes of the heat exchanger at a linear velocity (LV) of 1000 m / Hr or more from the viewpoint of flux removal performance. By passing the flux removing agent through the heat exchanger from the refrigerant inlet to the outlet, or from the outlet to the inlet, the flux removing agent can be distributed to various brazed parts of the heat exchanger, such as the brazed parts in the tubes, the brazed parts between the tank and the core plate, and the brazed parts between the tank and the inlet / outlet pipes. The linear velocity (LV) is expressed as LV=Q / A (m / Hr), where Q is the flow rate (m 3 / Hr), A: tube cross-sectional area (m 2 ). The lower limit of the linear velocity of the flux removing agent is not particularly limited, but is preferably 1200 m / Hr or more, and more preferably 1400 m / Hr or more. The upper limit of the linear velocity of the flux removing agent when passed through the tubes of the heat exchanger is also not particularly limited, but can be, for example, 10000 m / Hr or less, preferably 5000 m / Hr or less, and more preferably 4000 m / Hr or less. Therefore, the linear velocity of the flux removing agent when passed through the tubes of the heat exchanger can be, for example, 1000 m / Hr or more to 10000 m / Hr or less, preferably 1200 m / Hr or more to 5000 m / Hr or less, and more preferably 1400 m / Hr or more to 4000 m / Hr or less. When the flux removing agent is passed through the tubes of the heat exchanger, the flux removing agent can be circulated using, for example, an apparatus in which the refrigerant inlet / outlet of the heat exchanger, a tank for storing the flux removing agent, a pump, and an ion exchange resin tower are mutually connected by piping such as hoses.

[0030] <Process (ii)> In a flux removal method according to one embodiment of the present invention, step (i) may be followed by step (ii) of washing the aluminum-based metal material with deionized water having an electrical conductivity of 2 μS / cm or less. By including step (ii), impurity ions contained in the flux remover remaining on the aluminum-based metal material can be more efficiently removed. The method for washing the aluminum-based metal material with deionized water having an electrical conductivity of 2 μS / cm or less is not particularly limited. For example, the aluminum-based metal material may be immersed in deionized water having an electrical conductivity of 2 μS / cm or less, or the aluminum-based metal material may be sprayed or poured with deionized water. Two or more of these methods may also be combined. In this specification, the electrical conductivity of deionized water is measured at 25°C.

[0031] The cleaning time in step (ii), i.e., the time during which deionized water is brought into contact with the aluminum-based metal material, is preferably longer because cleaning efficiency is enhanced. The lower limit of the cleaning time is preferably 5 minutes or more, more preferably 10 minutes or more, and even more preferably 20 minutes or more. On the other hand, there is no particular upper limit to the cleaning time, but from the viewpoint of production efficiency, it is preferably 60 minutes or less, more preferably 40 minutes or less, and even more preferably 30 minutes or less. Therefore, the cleaning time in step (ii) is, for example, preferably 5 minutes or more and 60 minutes or less, more preferably 10 minutes or more and 40 minutes or less, and even more preferably 20 minutes or more and 30 minutes or less.

[0032] The temperature of the deionized water in step (ii) is not particularly limited, but is preferably 5°C to 95°C, more preferably 10°C to 90°C, and even more preferably 15°C to 85°C. If the temperature of the deionized water is below 5°C, the cleaning performance tends to be poor, the cleaning time tends to be too long, and productivity tends to be poor. If the temperature of the deionized water is above 100°C (which would cause it to boil), air will hinder liquid circulation and reduce surface contact efficiency.

[0033] When the aluminum-based metal material is a heat exchanger, step (ii) may involve passing deionized water having an electrical conductivity of 2 μS / cm or less at 25° C. through the tubes of the heat exchanger. The lower limit of the linear velocity (LV) of the deionized water is not particularly limited, but can be, for example, 200 m / Hr or more, preferably 400 m / Hr or more, and more preferably 1000 m / Hr or more. The upper limit of the linear velocity (LV) of the deionized water when passing through the tubes of the heat exchanger is also not particularly limited, but can be, for example, 10,000 m / Hr or less, preferably 4,000 m / Hr or less, and more preferably 2,000 m / Hr or less. Therefore, the linear velocity (LV) of the deionized water when passing through the tubes of the heat exchanger can be, for example, 200 m / Hr to 10,000 m / Hr, preferably 400 m / Hr to 4,000 m / Hr, and more preferably 1,000 m / Hr to 2,000 m / Hr. When passing deionized water having an electrical conductivity of 2 μS / cm or less at 25° C. through the tubes of the heat exchanger, the deionized water can be circulated using, for example, a device in which the refrigerant inlet / outlet of the heat exchanger, a water tank for storing deionized water, a pump, and an ion exchange resin tower are mutually connected by piping.

[0034] Between the steps (i) and (ii) or after the step (ii), it is desirable that the amount of potassium (K) remaining on the aluminum-based metallic material is small. Specifically, the amount of K element when the surface of the aluminum-based metallic material is measured by X-ray fluorescence analysis (XRF) is 15 mg / m 2 Preferably, it is 10 mg / m or less. 2 More preferably, it is 5 mg / m or less. 2 It is even more preferable that the amount of K element is 15 mg / m or less. 2 If the temperature exceeds this value, the flux is likely to be insufficiently removed, and when a heat exchanger is used for an aluminum-based metal material, ions of metals and the like are likely to be mixed into the refrigerant.

[0035] <Step (iii)> In a flux removal method according to one embodiment of the present invention, a step (iii) may be provided between steps (i) and (ii) or after step (ii), in which the aluminum-based metal material is dried in an oxygen-containing gas atmosphere at an ambient temperature of 80°C or higher for 0.5 hours or longer. Step (iii) allows a passive film to be formed on the aluminum-based metal material, thereby making it easier to prevent Al from leaching out of the aluminum-based metal material into refrigerants and the like. Examples of oxygen-containing gases include oxygen and air. From the viewpoint of drying efficiency, the ambient temperature during step (iii) is preferably 90°C to 150°C, more preferably 95°C to 140°C, and even more preferably 100°C to 130°C. From the viewpoints of productivity and drying efficiency, the drying time in step (iii) is preferably 0.5 hours to 12 hours, more preferably 1 hour to 8 hours, and even more preferably 2 hours to 4 hours.

[0036] The surface of the aluminum-based metal material after step (iii) preferably has an X-ray intensity of O element measured by X-ray fluorescence spectroscopy (XRF) of 0.01 kcps or more, more preferably 0.02 kcps or more, and even more preferably 0.03 kcps or more. When the X-ray intensity of O element is within the above range, the passive film formed on the aluminum-based metal material, as described above, tends to suppress the elution of Al derived from the aluminum-based metal material into the cooling water. Although no particular upper limit is set for the X-ray intensity of O element, taking into account the balance with production efficiency, it is usually, for example, 0.3 kcps or less, typically 0.2 kcps or less, and more typically 0.1 kcps or less.

[0037] <Post-treatment step (iv)> In the present invention, a post-treatment step (iv) may be performed after the above-described flux removal method to improve the corrosion resistance of the aluminum-based metal material. In the post-treatment step (iv), for example, a chemical conversion layer, a primer layer, or the like may be applied. When both a chemical conversion layer and a primer layer are applied, it is preferable to apply the primer layer after the chemical conversion layer. For example, the chemical conversion layer may contain at least one metal element selected from the group consisting of chromium, zirconium, titanium, and vanadium. For the primer layer, a primer layer containing a resin having at least one functional group selected from epoxy, urethane, acrylic, phenol, alkyl alcohol, and alkyl carboxylic acid may be used. [Example]

[0038] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to these examples and comparative examples.

[0039] (Examples 1 to 16, Comparative Examples 1 to 12) <1.Preparing the flux board> An aluminum alloy (A3003) plate (dimensions: 0.1 mm x 40 mm x 90 mm) was coated with flux paint (water (solvent) + KAlF4 + binder resin) and placed in a furnace heated to 660°C for 20 minutes to prepare a flux plate. The resulting flux plate was cooled to room temperature and removed from the furnace. XRF measurement was then performed on the surface to measure the amount of K element before flux removal. The results are shown in the "Before step (i)" column in Table 2. XRF measurement was performed using a Rigaku Corporation scanning X-ray fluorescence analyzer (product name: ZSX-PrimusIV) under the following conditions: X-ray tube: Rh, tube current / voltage: 50 kV / 60 mA, analysis diameter: 10 mm. The number of flux plates required for the following tests was prepared.

[0040] <2. Preparation of flux remover> Thereafter, each component was added to industrial water and stirred to obtain the mass concentration shown in Table 1, thereby preparing deflux agents of each level, No. 1 to No. 22. The following products were used as the nonionic surfactants and cationic surfactants in the table. Nonionic surfactant (polyoxyalkylene alkyl ether): ADEKA Corporation, Adekanol B2020 Cationic surfactant (octyldimethylethylammonium ethyl sulfate): Daiichi Kogyo Seiyaku Co., Ltd., Catiogen ES-O Anionic surfactant (sodium alkyldiphenyl ether disulfonate): Kao Corporation, Pelex SS-H

[0041] The surface tension of each flux remover at 25°C was measured by the Wilhelmy method using a static surface tensiometer (DY-500) manufactured by Kyowa Interface Science Co., Ltd. The results are shown in Table 1.

[0042] The pH of each flux remover at 25°C was measured using a glass electrode hydrogen ion concentration indicator (IM-32P) manufactured by DKK-TOA Corporation. Three-point calibration was performed using standard solutions of pH 6.86, 4.01, and 9.18. The results are shown in Table 1.

[0043] [Table 1]

[0044] <3. Flux removal process (i)> The prepared flux removers were placed in a tank, and the flux plate was placed in an acrylic column measuring 60 mm in diameter and 1,000 mm in length. The tank, pump, and column were connected in series with piping to construct a flux remover flow system. Note that an ion exchange resin tower was not used. The flux removal step (i) was performed by passing the flux remover through the column under the conditions listed in Table 2. In Table 2, "Temperature" refers to the temperature of the flux remover. "Time" refers to the time the flux plate was in contact with the flux remover. "Linear velocity" was calculated from the flow rate measured using a float flowmeter and the cross-sectional area of ​​the column. The amount of K element on the surface of the flux plate was then measured using the same method as above, and the results are listed in the "After step (i)" column of Table 2. The flux removal rate based on the change in the amount of K element before and after removal step (i) is also listed in Table 2.

[0045] <4.Water washing process (ii)> After the flux removal step (i), a tank containing deionized water was connected in place of the tank containing the defluxing agent. A deionized water-passing device was constructed, with the tank, pump, and column connected in series by piping. The washing step (ii) was performed by passing deionized water through the column under the conditions listed in Table 2. Note that an ion-exchange resin tower was not used. In Table 2, "Temperature" refers to the temperature of the deionized water. "Time" refers to the time the flux plate was in contact with the deionized water. The linear velocity was calculated from the flow rate measured using a float-type flowmeter and the cross-sectional area of ​​the column. "Electrical conductivity" refers to the electrical conductivity of deionized water at 25°C before use in washing. It was measured using an electrical conductivity cell (CT-27112B) connected to an electrical conductivity meter (IM-32P) manufactured by DKK-TOA Corporation. After the washing step (ii), the amount of potassium on the surface of the flux plate was measured using the same method as above. The results are listed in the "After step (ii)" column of Table 2. Table 2 also shows the flux removal rate based on the change in the amount of K element before and after the water washing step (ii).

[0046] <5. Drying process (iii)> After the water washing step (ii), the flux plate was placed in a dryer in an air atmosphere and dried at the atmospheric temperature and for the time shown in Table 2 (drying step (iii)). After cooling to room temperature, the flux plate was removed from the dryer and subjected to XRF measurement of the surface to measure the X-ray intensity of the O element. The XRF measurement was performed using a scanning X-ray fluorescence analyzer (product name: ZSX-PrimusIV) manufactured by Rigaku Corporation under the following conditions: X-ray tube: Rh, tube current / voltage: 50 kV / 60 mA, analysis diameter: 10 mm. The results are shown in the "Oxygen Intensity" column of Table 2.

[0047] <6. Evaluation> The water washability, resistance to re-elution, and processed appearance were evaluated according to the following procedures.

[0048] (6-1. Evaluation of water washability) Near the end of the water washing step (ii), 300 mL of washing water was collected in a glass beaker, and the electrical conductivity of the washing water was measured under the same conditions as those described for the water washing step (ii). The results are shown in Table 2.

[0049] (6-2. Evaluation of re-elution resistance) Two liters of deionized water with an electrical conductivity of 2 μS / cm at 25°C was placed in a water tank. The flux plate after the drying step (iii) was then immersed in the deionized water in the water tank at 40°C for 480 hours. After removing the flux plate from the water tank, the electrical conductivity of the deionized water in the water tank at 25°C was measured. The electrical conductivity of the deionized water at 25°C was measured using an electrical conductivity cell (CT-27112B) connected to an electrical conductivity meter (IM-32P) manufactured by DKK-TOA Corporation. The better the resistance to re-elution, the lower the electrical conductivity. Evaluation was performed according to the following criteria. The results are shown in Table 2. Although Comparative Examples 5, 6, and 9 had high oxygen intensity, it is presumed that the poor results were due to the generation of smut caused by the flux removal using sodium hydroxide, which then eluted. A: 50μS / cm or less B: More than 50μS / cm and less than 100μS / cm C: More than 100μS / cm and less than 200μS / cm D: More than 200μS / cm

[0050] (6-3. Appearance of the processed product) The appearance of the flux plate after the drying step (iii) was visually observed, and the degree of discoloration was visually evaluated. The results are shown in Table 2. A: Aluminum metallic color or white appearance is observed B: Yellowing is observed C: Blackened

[0051] [Table 2-1]

[0052] [Table 2-2]

Claims

1. A flux remover comprising (A) an oxoacid and / or a salt thereof and (B) a surfactant, and having a pH of 2 or less.

2. 2. The flux remover according to claim 1, wherein the oxoacid and / or salt thereof (A) comprises one or more selected from nitric acid, sulfuric acid, sulfurous acid, nitrous acid, and salts thereof.

3. 2. The flux remover according to claim 1, wherein the surfactant (B) comprises one or both of a nonionic surfactant and a cationic surfactant.

4. 2. The flux remover according to claim 1, which has a surface tension of 20 to 55 mN / m.

5. 2. The flux remover according to claim 1, wherein the surfactant (B) comprises one or both of a nonionic surfactant and a cationic surfactant, and has a surface tension of 20 to 55 mN / m.

6. A method for removing flux, comprising a step (i) of contacting an aluminum-based metal material to which flux has adhered with a flux remover comprising (A) an oxoacid and / or a salt thereof and (B) a surfactant and having a pH of 2 or less.

7. 7. The flux removal method according to claim 6, wherein the oxoacid and / or salt thereof (A) comprises one or more selected from nitric acid, sulfuric acid, sulfurous acid, nitrous acid, and salts thereof.

8. 7. The flux removal method according to claim 6, wherein the surfactant (B) includes one or both of a nonionic surfactant and a cationic surfactant.

9. 7. The method for removing flux according to claim 6, wherein the surface tension is 20 to 55 mN / m.

10. 7. The flux removal method according to claim 6, wherein the surfactant (B) contains one or both of a nonionic surfactant and a cationic surfactant, and has a surface tension of 20 to 55 mN / m.

11. The flux removing method according to claim 6, wherein the temperature of the flux removing agent is 60°C or higher and lower than 100°C.

12. 7. The flux removal method according to claim 6, further comprising, after the step (i), a step (ii) of washing the aluminum-based metallic material with deionized water having an electrical conductivity of 2 μS / cm or less.

13. 7. The flux removal method according to claim 6, wherein the aluminum-based metallic material is a heat exchanger or a part thereof.

14. 7. The method for removing flux according to claim 6, wherein the step (i) involves passing the flux removing agent through a tube of a heat exchanger at a linear velocity (LV) of 1000 m / Hr or more.

15. 13. The method for removing flux according to claim 12, wherein the step (ii) involves passing the deionized water having an electrical conductivity of 2 μS / cm or less through a tube of the heat exchanger at a linear velocity (LV) of 200 m / Hr or more.

16. The flux removal method according to any one of claims 12 to 15, comprising a step (iii) of drying the aluminum-based metallic material in an oxygen-containing gas atmosphere at an atmospheric temperature of 80°C or higher for 0.5 hours or more between the step (i) and the step (ii) or after the step (ii).

17. Between the step (i) and the step (ii), or after the step (ii), the amount of K element when the surface of the aluminum-based metal material is measured by X-ray fluorescence analysis (XRF) is 15 mg / m 2 The flux removal method according to any one of claims 12 to 15, wherein:

18. 17. The flux removal method according to claim 16, wherein, after the step (iii), the X-ray intensity of O element when the surface of the aluminum-based metallic material is measured by X-ray fluorescence spectroscopy (XRF) is 0.01 kcps or more.

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