Surface treatment agent

Abstract

To provide a surface treatment agent capable of forming a good film capable of maintaining hydrophilicity, corrosion resistance and frosting resistance over a long period of time.SOLUTION: A surface treatment agent comprising a water-soluble inorganic compound (A), an organoalkoxysilane (B), and one or more (C) selected from an anionic surfactant having a weight average molecular weight of 3000 or less and a nonionic surfactant having a weight average molecular weight of 3000 or less and a cloud point of a 10% by mass aqueous solution of 20 °C or higher, wherein Mc / (Ma + Mb) = 0.001 to 0.3, where Ma, Mb, and Mc are the respective masses of (A), (B), and (C).SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a surface treatment agent, particularly to a surface treatment agent for metal materials. The present invention also relates to a surface treatment method for metal materials using the surface treatment agent, a method for manufacturing a surface-treated metal material, a heat exchanger using the surface-treated metal material, a surface treatment method for a heat exchanger, a method for manufacturing a surface-treated heat exchanger, and a surface-treated heat exchanger. [Background technology]

[0002] Air-conditioning heat exchangers are often made of aluminum due to their cost, specific strength, and workability. Surface treatments are often used to impart corrosion resistance and hydrophilicity to the heat exchangers. Furthermore, with the recent spread of electric vehicles and other vehicles, the number of heat pump-type air conditioners has increased, creating a demand for frost resistance in surface treatments. Frost, formed by frozen condensed water, accumulates on the exterior heat exchanger of a heat pump during heating operation. Because the frost reduces heat exchange efficiency, the system must periodically shut down heating operation and perform defrosting. However, this reduces the power efficiency of the heating system. Therefore, there is a need for heat exchanger surfaces that are less susceptible to frost growth.

[0003] Patent Document 1 discloses a method for slowing the growth of frost by coating the surface of a heat exchanger with a water-repellent coating. Patent Document 2 also discloses a technique for delaying the freezing of water condensed on the surface of a heat exchanger by adding a freeze retardant such as a sugar (Patent Document 2) or an antifreeze protein (Patent Document 3) to a surface treatment agent. Patent Document 4 also discloses a surface treatment agent using a water-soluble inorganic oxide and an organoalkoxysilane. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2011-102334 A [Patent Document 2] JP 2019-135283 A [Patent Document 3] Japanese Patent Publication No. 2020-098064 [Patent Document 4] Japanese Patent Publication No. 2023-145182 Summary of the Invention [Problem to be solved by the invention]

[0005] However, if the heat exchanger surface is treated to be water-repellent as described in Patent Document 1, when the frost that has formed is dissolved in water during defrosting operation and then tried to be discharged from the heat exchanger, water bridges form between the fins of the heat exchanger, making it difficult to discharge, and when heating operation is resumed, the water remaining in the heat exchanger refreezes, making the heat exchanger more likely to become clogged.

[0006] Furthermore, the freeze retardants or surface treatment agents described in Patent Document 2, Patent Document 3, or Patent Document 4 have a problem with performance durability because they flow out of the surface treatment film together with water when condensed water is repeatedly generated and discharged in a heat exchanger.

[0007] In view of the above circumstances, an object of the present invention is to provide, in one embodiment, a surface treatment agent capable of forming a good film that can maintain hydrophilicity, corrosion resistance, and frost resistance for a long period of time. In a further embodiment, an object of the present invention is to provide, respectively, a method for surface treatment of a metal material, a method for manufacturing a surface-treated metal material, a heat exchanger using the surface-treated metal material, a method for surface treatment of a heat exchanger, a method for manufacturing a surface-treated heat exchanger, and a surface-treated heat exchanger. [Means for solving the problem]

[0008] As a result of intensive research to solve the above problems, the present inventors have found that by mixing a water-soluble inorganic compound (A), an organoalkoxysilane (B), and a specific surfactant (C) in an appropriate mixing ratio, it is possible to form a good coating on the surface of a metal material that can maintain hydrophilicity, corrosion resistance, and frost resistance for a long period of time.

[0009] The present invention is exemplarily specified as follows. [1] A surface treatment agent comprising: (A) a water-soluble inorganic compound; (B) an organoalkoxysilane; and (C) one or more surfactants selected from the group consisting of anionic surfactants having a weight-average molecular weight of 3,000 or less and nonionic surfactants having a weight-average molecular weight of 3,000 or less and having a cloud point of 20°C or higher in a 10% by mass aqueous solution, wherein Mc / (Ma+Mb)=0.001 to 0.3 when Ma, Mb, and Mc are the masses of (A), (B), and (C), respectively. [2] The surface treatment agent according to [1], wherein the water-soluble inorganic compound (A) is alkaline and contains one element (M1) selected from Si, V, Zr, Mo, Ti, and W, and one cation component (M2) selected from Na, K, Li, and NH4, and the molar ratio of (M2) to (M1), (M2) / (M1), is 0.1 to 8.0. [3] The surface treatment agent according to [1] or [2], wherein Ma / Mb=0.25 to 4.0. [4] The surface treatment agent according to any one of [1] to [3], wherein the water-soluble inorganic compound (A) and the organoalkoxysilane (B) form a composite. [5] The surface treatment agent according to any one of [1] to [4], wherein the water-soluble inorganic compound (A) is represented by the molecular formula Me2O·nSiO2, where Me is one cation component selected from Na, K, Li, and NH4, and n is 0.5 to 8.0. [6] The surface treatment agent according to any one of [1] to [5], further comprising a water-soluble anionic resin (D) having a weight-average molecular weight of 5,000 or more. [7] The surface treatment agent according to [6], wherein the water-soluble anionic resin (D) has an acid value of 20 to 500 mgKOH / g and a weight-average molecular weight of 10,000 to 2,000,000. [8] The surface treatment agent according to [6] or [7], wherein the water-soluble anionic resin (D) has one or more functional groups selected from an amide group and a hydroxyl group. [9] The surface treatment agent according to any one of [6] to [8], wherein, when the mass of the water-soluble anionic resin (D) is Md, Md / (Ma+Mb+Mc)=0.1 to 4.0.

[10] A method for treating the surface of a metal material, comprising the step (a) of contacting the metal material with the surface treatment agent according to any one of [1] to [9].

[11] The surface treatment method for a metal material according to

[10] , further comprising, prior to the step (a), a step (b) of forming an undercoat film containing at least one element selected from Cr, Zr, Ti, and V on the metal material.

[12] The surface treatment method for a metal material according to

[10] or

[11] , further comprising, before the step (a), a step (c) of forming a primer layer containing a resin on the metal material.

[13] The method for treating the surface of a metal material according to any one of

[10] to

[12] , further comprising, after the step (a), a step (d) of drying the metal material.

[14] A method for producing a surface-treated metal material, comprising a step of contacting a metal material with the surface treatment agent according to any one of [1] to [9] and then drying the metal material.

[15] A heat exchanger using a surface-treated metal material obtained by the method for surface treatment of a metal material according to

[10] .

[16] A method for treating the surface of a heat exchanger, comprising a step of contacting the heat exchanger with the surface treatment agent according to any one of [1] to [9] and then drying the heat exchanger.

[17] A method for producing a surface-treated heat exchanger, comprising a step of contacting a heat exchanger with the surface treatment agent according to any one of [1] to [9] and then drying the heat exchanger.

[18] A surface-treated heat exchanger obtained by the manufacturing method described in

[17] . [Effects of the Invention]

[0010] According to one embodiment of the present invention, a surface treatment agent capable of forming a film that can maintain hydrophilicity, corrosion resistance, and frost resistance for a long period of time can be provided. Therefore, the present invention can contribute to improving the performance of, for example, heat exchangers including metal materials, particularly heat exchangers for heat pumps that include metal material fins. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments of the present invention, including a surface treatment agent and a surface-treated metal material, will be described in detail. The present invention can be modified as desired without departing from the spirit of the present invention, and is not limited to the following embodiments. In this specification, the symbol "to" indicating a numerical range includes both the upper and lower limits. For example, "X to Y" means that the range is from X to Y.

[0012] <1. Surface treatment agent> According to one embodiment of the present invention, there is provided a surface treatment agent comprising a water-soluble inorganic compound (A), an organoalkoxysilane (B), and one or more surfactants (C) selected from the group consisting of anionic surfactants having a weight-average molecular weight of 3,000 or less and nonionic surfactants having a weight-average molecular weight of 3,000 or less and having a cloud point of 20°C or higher in a 10% by mass aqueous solution.

[0013] <1-1. Water-soluble inorganic compound (A)> The water-soluble inorganic compound (A) serves to impart hydrophilicity and corrosion resistance to the coating. The water-solubility of the water-soluble inorganic compound (A) provides the advantage of improved workability. The water-soluble inorganic compound (A) may be used singly or in combination of two or more. The water-soluble inorganic compound (A) is preferably one or more selected from water-soluble inorganic oxides and their salts (A), and is alkaline. It contains an element (M1) selected from Si, V, Zr, Mo, Ti, and W, and a cation component (M2) selected from Na, K, Li, and NH4. The molar ratio of (M2) to (M1), (M2) / (M1), is preferably 0.1 to 8.0. When (M2) / (M1) is 0.1 or greater, corrosion of metals such as aluminum can be prevented, resulting in enhanced coating durability. The lower limit of (M2) / (M1) is preferably 0.2 or greater, more preferably 0.25 or greater. When (M2) / (M1) is 8.0 or less, water solubility is increased, and the liquid stability of the surface treatment agent can be improved. The upper limit of (M2) / (M1) is more preferably 7.0 or less, and even more preferably 6.0 or less. Therefore, (M2) / (M1) is, for example, even more preferably 0.2 to 7.0, and even more preferably 0.25 to 6.0.

[0014] To obtain excellent hydrophilicity and corrosion resistance, it is preferable to use an alkali silicate represented by the general molecular formula Me2O·nSiO2 (Me represents one cationic component selected from Na, K, Li, and NH4, and n is 0.5 to 8.0) as the water-soluble inorganic compound (A). In particular, it is preferable to use an alkali silicate in which n = 1.0 to 8.0.

[0015] In this specification, "water-soluble" refers to a substance that has a solubility of 0.1% by mass or more in water at room temperature (20° C.), with a solubility of 0.5% by mass or more being preferred, and particularly 1% by mass or more being more preferred. In addition, in this specification, an inorganic oxide refers to a compound in which a metal atom is directly bonded to an oxygen atom and has a moiety in which the oxidation number of the metal atom is (+I) or more.

[0016] The water-soluble inorganic compound (A) being "alkaline" means that (A) exhibits "alkaline" when dissolved in water at 25° C. at a concentration of 0.1% by mass. The pH of (A) when dissolved in water at 25° C. at a concentration of 0.1% by mass is preferably 8 to 12, and more preferably 9 to 11.5.

[0017] Other silicon compounds that can be used as the water-soluble inorganic compound (A) include, for example, silicon dioxide hydrates.

[0018] Titanium compounds that can be used as the water-soluble inorganic compound (A) include salts of titanium oxide (potassium salts, ammonium salts, etc.).

[0019] Examples of vanadium compounds that can be used as the water-soluble inorganic compound (A) include vanadates (sodium, potassium, ammonium salts, etc.) and metavanadates (sodium, potassium, ammonium salts, etc.).

[0020] Examples of zirconium compounds that can be used as the water-soluble inorganic compound (A) include zirconium carbonate and its hydrates, as well as zirconium carbonate salts such as ammonium zirconium carbonate and potassium zirconium carbonate.

[0021] Examples of molybdenum compounds that can be used as the water-soluble inorganic compound (A) include molybdic acid and its salts (sodium, potassium, ammonium salts, etc.).

[0022] Examples of tungsten compounds that can be used as the water-soluble inorganic compound (A) include salts of tungstic acid (sodium, potassium, ammonium salts, etc.).

[0023] <1-2. Organoalkoxysilane (B)> The organoalkoxysilane (B) acts as a binder when mixed into the coating. The organoalkoxysilane (B) has the effect of delaying the freezing of condensed water due to the action of the functional group bonded to the alkoxysilane. It also prevents the water-soluble inorganic compound (A), surfactant (C), and water-soluble anionic resin (D) from washing away, contributing to the long-term development of hydrophilicity, corrosion resistance, and frost resistance. Furthermore, it ensures the stability of the water-soluble inorganic compound (A) in the surface treatment agent, contributing to the enhancement of the stability of the surface treatment agent.

[0024] The organoalkoxysilane (B) is not particularly limited as long as it can be hydrolyzed in water and dehydration-condensed. The organoalkoxysilane (B) may be used alone or in combination of two or more.

[0025] Examples of organoalkoxysilanes include silane coupling agents having an alkoxy group as a hydrolyzable group. Examples of alkoxy groups include, but are not limited to, alkoxy groups having 1 to 4 carbon atoms (particularly, 1 or 2 carbon atoms), such as methoxy, ethoxy, propoxy, and butoxy. Furthermore, the silane coupling agent may have, as an organic functional group, an epoxy group (particularly, a glycidyl group), an amino group, a vinyl group, a mercapto group, an acryloxy group, a methacryloxy group, a ureido group, or an isocyanate group. Among these, organoalkoxysilanes having one or more glycidyl groups as organic functional groups are preferred, due to their excellent ability to form a complex with the water-soluble inorganic compound (A). Suitable organoalkoxysilanes include, for example, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, and 3-glycidoxypropylmethyldiethoxysilane. Unless contrary to the above intention, the organoalkoxysilane may have one or more of an amino group, a vinyl group, a mercapto group, an acryloxy group, a methacryloxy group, a ureido group, or an isocyanate group in addition to the glycidyl group.

[0026] Organoalkoxysilanes can be hydrolyzed in water to produce silanols and alcohols as hydrolysates. The silanols and / or alcohols produced by hydrolysis may be hydrogen-bonded to each other, and such compounds are also considered hydrolysates in this specification. Furthermore, some or all of the silanols produced by hydrolysis may undergo a dehydration condensation reaction to produce a condensation product (organosiloxane) having a siloxane bond (Si-O-Si). The surface treatment agent according to the present invention may contain the organoalkoxysilane (B) in its original form or in the form of a hydrolyzate and / or condensate. Therefore, in this specification, "organoalkoxysilane" refers to one or more selected from organoalkoxysilanes, their hydrolysates, and condensates.

[0027] <1-3. Compounds> The water-soluble inorganic compound (A) and the organoalkoxysilane (B) preferably form a complex in the surface treatment agent. Although the chemical structure of the complex is not entirely clear, it is presumed to have a structure in which silanol (-Si-OH) generated by hydrolysis of the organoalkoxysilane is bonded to a metal element of the water-soluble inorganic compound. In this specification, when multinuclear NMR spectrum measurement is performed, if a peak of (Si-O-Me; Me constitutes the water-soluble inorganic compound, and is a metal atom or cationic component directly bonded to an oxygen atom, such as Si, V, Zr, Mo, Ti, W, Na, K, Li, or NH4) is observed, the complex is deemed to be present; if such peak is not observed, the complex is deemed not to be present. In the examples, multinuclear NMR spectrum measurements were carried out under the following conditions. Measurement equipment: JEOL Ltd. JNM-ECX400 Probe: JEOL Ltd. NM-40T10AT Measurement solvent: Deuterium oxide

[0028] The particle size of the composite of the water-soluble inorganic compound (A) and organoalkoxysilane (B) contributes to the stability and film-forming properties of the surface treatment agent. The smaller the particle size of the composite, the less likely precipitation will occur in the surface treatment agent during long-term storage, and the adhesion of the film formed by using the surface treatment agent and the film-forming properties of the film itself will also be improved. From the above perspective, the median diameter of the composite is preferably 10 nm or less.

[0029] In this specification, the term "median diameter" refers to the cumulative 50% diameter based on the scattered light intensity when measuring particle size distribution by dynamic light scattering, regardless of whether the particle is a primary particle or a secondary particle. An example of a measuring instrument using dynamic light scattering is the UPA-EX150 manufactured by Nikkiso Co., Ltd. Dynamic light scattering utilizes the fact that the speed of movement (Brownian motion) of particles in a solution varies depending on their size. A laser beam is irradiated onto the solution, and the scattered light is observed with a photon detector, followed by frequency analysis to obtain a particle size distribution. In the examples, the particle size distribution of the composite was measured under the following conditions. While the measurement procedure allows for a particle size distribution that takes into account particles other than the composite, it is difficult to measure these particles separately. Therefore, in this specification, even when particles other than the composite are present, the particle size distribution is considered to be that of the composite. (Particle size measurement conditions) Measuring device: Nikkiso Co., Ltd. UPA-EX150 Light source: Semiconductor laser 780nm, 3mW Light source probe: Internal probe type Preparation of measurement sample: The composite of the water-soluble inorganic compound (A) and the organoalkoxysilane (B) is diluted with deionized water to a solids concentration of about 0.01% by mass, and then thoroughly stirred and dispersed. The solids concentration here refers to the value measured by the normal pressure heat drying method (sample weight: 1.0 g, drying temperature 110 ° C × 2 hours) in accordance with JIS K6828-1:2003. Measurement time: 180 seconds Circulation: None Transparency: Transparent Shape: Non-spherical Refractive index: 1.81 (default setting of the device) Solvent: Water Solvent refractive index: 1.333

[0030] <1-4. Surfactants (C)> The one or more surfactants (C) selected from anionic surfactants having a weight-average molecular weight of 3,000 or less and nonionic surfactants having a weight-average molecular weight of 3,000 or less and a cloud point of a 10% by mass aqueous solution of the surfactant being 20°C or higher, have high hydrophilicity, reduce the contact angle of the film, make the condensed water flat, and have the effect of delaying the freezing of the condensed water and slowing the growth of frost.

[0031] The hydrophilicity of a nonionic surfactant can be determined by its cloud point. As the temperature of a nonionic surfactant in an aqueous solution increases, the hydrophilic groups of the nonionic surfactant self-associate, lose their hydrophilicity, and precipitate from the water at a certain temperature. This temperature is called the cloud point. Generally, the more hydrophilic a nonionic surfactant is, the higher its cloud point. In this specification, the cloud point is measured in accordance with JIS K2269-1987. The cloud point of a 10% by weight aqueous solution of a nonionic surfactant is preferably 20°C or higher, more preferably 30°C or higher. While no particular upper limit is set for the cloud point of a 10% by weight aqueous solution of a nonionic surfactant, from the perspective of procurement costs, it is preferably 80°C or lower, more preferably 70°C or lower. Therefore, for example, the cloud point of a 10% by weight aqueous solution of a nonionic surfactant is preferably 20 to 80°C, more preferably 30 to 70°C.

[0032] The weight-average molecular weight of the anionic surfactant and the nonionic surfactant is preferably 3000 or less, more preferably 2000 or less, still more preferably 1500 or less, and still more preferably 1000 or less, because the effect per unit weight is high. Further, the weight-average molecular weight of the anionic surfactant and the nonionic surfactant is preferably 100 or more, more preferably 150 or more, and still more preferably 300 or more, for the reason of the stability during storage of the surface treatment agent. Therefore, the weight-average molecular weight of the anionic surfactant and the nonionic surfactant is, for example, preferably 100 to 3000, more preferably 150 to 2000, still more preferably 300 to 1500, and still more preferably 300 to 1000.

[0033] In the present specification, the weight-average molecular weight of the anionic surfactant and the nonionic surfactant is measured by the GPC method. The measurement of the weight-average molecular weight in the examples was carried out under the following conditions. <Measurement conditions by GPC> The measurement was carried out using a high-speed GPC device (HLC-8320GPC: manufactured by Tosoh Corporation), and the weight-average molecular weight was determined using a combination of an SEC column and a guard column. The measurement was carried out under the following conditions. SEC column: TSKgel SuperAWM-H (manufactured by Tosoh Corporation) Guard column: TSKgurdcolumn SuperAW-H (manufactured by Tosoh Corporation) Detector: RI (built-in detector of HLC-8320GPC) Standard sample: Polystyrene Sample injection volume: 30 μL of 0.06% DMF solution Flow rate: 0.5 mL / min Eluent: DMF / 100 mM LiBr / 60 mM H3PO4

[0034] Let Ma be the mass of the water-soluble inorganic compound (A), Mb be the mass of the organoalkoxysilane (B), and Mc be the mass of one or more (C) selected from anionic surfactants with a weight-average molecular weight of 3000 or less and nonionic surfactants with a weight-average molecular weight of 3000 or less and a cloud point of a 10% by mass aqueous solution of the surfactant being 20°C or higher. By blending the surfactants so that Mc / (Ma+Mb) = 0.001 to 0.3, it is possible to flatten the shape of condensed water before freezing and improve frost resistance. Preferably, Mc / (Ma+Mb) = 0.005 to 0.25, and more preferably, Mc / (Ma+Mb) = 0.01 to 0.25.

[0035] Examples of nonionic surfactants include, but are not limited to, polyalkylene glycols, polyalkylene glycol alkyl ethers, polyoxyalkylene alkyl ethers, polyoxyalkylene phenyl ethers, ether ester compounds, glycidyl ether compounds, and carbohydrates having a pyranose structure or a furanose structure.

[0036] Examples of anionic surfactants include, but are not limited to, low-molecular-weight organic compounds having hydrophilic groups such as carboxylic acids, sulfonic acids, sulfates, and phosphates; homopolymers and copolymers of monomers having one or more of these hydrophilic groups in their side chains; and alkali metal salts thereof. Examples of hydrophilic groups include carboxyl groups, sulfo groups, and phosphate groups. The sulfo groups and phosphate groups may each form an ester bond. More specifically, examples include carboxylic acids or salts thereof, alkyl ether carboxylic acids or salts thereof, alkyl sulfuric acids or salts thereof, alkyl ether sulfuric acids or salts thereof, acyl isethionic acids or salts thereof, alkyl sulfonic acids or salts thereof, alkyl benzene sulfonic acids or salts thereof, monoalkyl diphenyl ether disulfonic acids or salts thereof, dialkyl diphenyl ether disulfonic acids or salts thereof, monoalkyl diphenyl ether monosulfonic acids or salts thereof, and dialkyl diphenyl ether monosulfonic acids or salts thereof.

[0037] <1-5. Water-soluble anionic resin (D)> The water-soluble anionic resin (D) imparts hydrophilicity due to its anionic functional group, reduces the contact angle of the film, flattens the condensed water, retards the freezing of the condensed water, and slows the growth of frost. In addition, since it has a higher molecular weight than the above-mentioned anionic surfactants and nonionic surfactants, it also improves the durability of the film when it comes into contact with water.

[0038] Such an effect is particularly pronounced when the composition satisfies Md / (Ma+Mb+Mc)=0.1 to 4.0, where Ma is the mass of the water-soluble inorganic compound (A), Mb is the mass of the organoalkoxysilane (B), Mc is the mass of one or more surfactants (C) selected from anionic surfactants having a weight-average molecular weight of 3000 or less and nonionic surfactants having a weight-average molecular weight of 3000 or less and a cloud point of a 10% by mass aqueous solution of the surfactant being 20°C or higher, and Md is the mass of the water-soluble anionic resin (D). The frost resistance of the coating can be improved by blending the components such that Md / (Ma+Mb+Mc)=0.3 to 3.8 is preferred, and Md / (Ma+Mb+Mc)=0.5 to 3.6 is more preferred.

[0039] The water-soluble anionic resin (D) is preferably a copolymer of a monomer having a sulfo group or its salt with a monomer having an anionic functional group other than the sulfo group and its salt, or a copolymer of a monomer having a sulfo group or its salt with a monomer having an anionic functional group other than the sulfo group and its salt, and a non-anionic monomer copolymerizable with the above two monomers. Examples of monomers having a sulfo group or its salt include vinyl sulfonic acid, styrene sulfonic acid, sulfoethyl acrylate, sulfoethyl methacrylate, N-methylenesulfonic acid acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, olefin sulfonic acids such as 5-sulfoisophthalic acid, benzenesulfonic acid, and salts thereof. Examples of anionic functional groups other than the sulfo group and its salt include carboxyl groups, phosphonic acid groups, phosphate groups, and salts thereof. Examples of monomers having an anionic functional group other than a sulfo group and its salts include unsaturated acids or their salts, such as (meth)acrylic acid, itaconic acid, maleic acid, malonic acid, propane-1,2,3-tricarboxylic acid, 2-(phosphonooxy)ethyl methacrylate, vinylphosphonic acid, and allylphosphonic acid. Examples of copolymers of such monomers having a sulfo group or its salt with monomers having an anionic functional group other than a sulfo group or its salt include copolymers of acryl sulfonic acid and acrylic acid, copolymers of sodium 2-acrylamido-2-methylpropanesulfonate and acrylic acid, and copolymers of sodium sulfoethyl acrylate and acrylic acid. Other examples of the water-soluble anionic resin (D) include homopolymers of monomers having a sulfo group or its salt, and homopolymers of monomers having an anionic functional group other than a sulfo group or its salt. For example, examples of homopolymers of monomers having a sulfo group or a salt thereof include homopolymers of olefin sulfonic acids or salts thereof, such as vinyl sulfonic acid, styrene sulfonic acid, sulfoethyl acrylate, sulfoethyl methacrylate, N-methylene sulfonic acid acrylamide, and 2-acrylamido-2-methylpropane sulfonic acid.Examples of homopolymers of monomers having anionic functional groups other than sulfo groups and their salts include homopolymers of unsaturated acids or their salts, such as poly(meth)acrylic acid, polyitaconic acid, polymaleic acid, poly2-(phosphonooxy)ethyl methacrylate, polyvinylphosphonic acid, and polyallylphosphonic acid. Examples of non-anionic monomers include pentaerythritol, ethylene glycol, propylene glycol, and glycerin. Examples of copolymers of these non-anionic monomers and anionic monomers include copolymers of polyethylene glycol, propylene glycol, and 5-sulfoisophthalic acid ester. The water-soluble anionic resin (D) may be used singly or in combination of two or more.

[0040] The acid value of the water-soluble anionic resin (D) is preferably 20 to 500 mgKOH / g, more preferably 50 to 400 mgKOH / g. The acid value of the water-soluble anionic resin (D) can be adjusted, for example, by partially neutralizing sulfo groups or acids other than sulfo groups. The acid value is measured in accordance with JIS K0070-1992.

[0041] The weight-average molecular weight of the water-soluble anionic resin (D) is preferably 10,000 or more, more preferably 30,000 or more, and even more preferably 60,000 or more, for reasons of preventing the water-soluble anionic resin from washing away from the film into water when the film is exposed to water and thus making it easier to maintain its performance. Furthermore, the weight-average molecular weight of the water-soluble anionic resin (D) is preferably 2,000,000 or less, more preferably 1,800,000 or less, and even more preferably 1,500,000 or less, for reasons of making the viscosity of the surface treatment agent easy to apply. Therefore, the weight-average molecular weight of the water-soluble anionic resin (D) is, for example, preferably 10,000 to 2,000,000, more preferably 30,000 to 1,800,000, and even more preferably 60,000 to 1,500,000.

[0042] In this specification, the weight average molecular weight of the water-soluble anionic resin (D) is measured by the GPC method. The measurement of the weight average molecular weight in the examples was carried out under the following conditions. <Measurement conditions by GPC> The measurement was carried out using a high-speed GPC device (HLC-8320GPC, manufactured by Tosoh Corporation), and the weight average molecular weight was determined using a combination of SEC columns and guard columns. The measurement was carried out under the following conditions. SEC column: TSKgel SuperAWM-H (manufactured by Tosoh Corporation) Guard column: TSKgurdcolumn SuperAW-H (manufactured by Tosoh Corporation) Detector: RI (built-in detector of HLC-8320GPC) Standard sample: Polystyrene Sample injection volume: 30 μL of 0.06% DMF solution Flow rate: 0.5 mL / min Eluent: DMF / 100 mM LiBr / 60 mM H3PO4

[0043] <1-6. Solvent (E)> The surface treatment agent can contain various additives such as an acid catalyst, a cross-linking agent, an antibacterial agent, a lubricant, a pigment, a dye, an inhibitor for imparting corrosion resistance, etc. as necessary. Further, the surface treatment agent preferably contains water, a water-miscible solvent, or a mixed solvent of water and a water-miscible solvent in order to dissolve the necessary components. From the viewpoint of easy handling of the surface treatment agent, it is preferable to use deionized water as the water. The water content is preferably 80 to 99% by mass, more preferably 85 to 95% by mass, based on the total amount of the surface treatment agent. When using a mixed solvent of water and a water-miscible solvent, the proportion of water is preferably, for example, 60% by mass or more based on the total mass of the mixed solvent. The water-miscible solvent is not particularly limited as long as it does not phase-separate after mixing with water, and examples thereof include alcohols such as methanol and ethanol.

[0044] <1-7. Manufacturing method> The surface treatment agent can be prepared, for example, by mixing the above components in a desired ratio, adding a required amount of water to the mixture, and stirring.

[0045] However, with regard to the organoalkoxysilane (B), one or more selected from hydrolysates and condensates of the organoalkoxysilane (B) may be produced in water beforehand and then mixed with the other components. Alternatively, the organoalkoxysilane (B) may be mixed with the other components and one or more selected from hydrolysates and condensates may be produced during mixing. In either case, in order to efficiently promote the hydrolysis of the organoalkoxysilane (B), it is preferable to stir the mixture while heating it to 30 to 80°C. To promote the hydrolysis of the organoalkoxysilane (B), an acid catalyst may be added as needed.

[0046] Furthermore, to promote the formation of the complex, the water-soluble inorganic compound and the organoalkoxysilane (B) may be placed in a container and pretreated with water, heated, stirred, or the like, before being mixed with other components. The heating temperature is preferably 30 to 80°C to efficiently promote the hydrolysis of the organoalkoxysilane (B) and / or the formation of the complex. In the pretreatment, an acid catalyst may be added as needed to promote the hydrolysis of the organoalkoxysilane (B).

[0047] <2. Surface-treated metal materials and surface-treated heat exchangers> According to one embodiment of the present invention, there is provided a surface treatment method for a metal material, and a method for producing a surface-treated metal material, comprising the steps of contacting the above-described surface treatment agent with a metal material and drying the surface treatment agent after the contacting step. Furthermore, this production method produces a metal material having a surface treatment film. The metal material produced in this manner and having a surface treatment film on its surface is useful for forming fin materials. Furthermore, this fin material is useful as a component of a heat exchanger. Therefore, according to one embodiment of the present invention, there is provided a heat exchanger using the surface-treated metal material obtained by the above-described production method.

[0048] According to another embodiment of the present invention, there are provided a surface treatment method for a heat exchanger and a method for manufacturing a surface-treated heat exchanger, the method including the steps of contacting the heat exchanger with the surface treatment agent and drying the surface treatment agent after the contacting step. Furthermore, the method allows for the production of a surface-treated heat exchanger having a surface treatment film. The heat exchanger thus obtained is provided with a surface treatment film having excellent corrosion resistance, which is useful in terms of extending the life of the equipment and making effective use of resources. Furthermore, the surface treatment film formed on the heat exchanger has excellent hydrophilicity, which prevents water droplets from accumulating between the fins, thereby suppressing a decrease in heat exchange efficiency and ultimately improving energy efficiency.

[0049] The proportions of the water-soluble inorganic compound (A), organoalkoxysilane (B), one or more surfactants (C) selected from the group consisting of anionic surfactants having a weight-average molecular weight of 3000 or less and nonionic surfactants having a weight-average molecular weight of 3000 or less and having a cloud point of 20°C or higher in a 10% by mass aqueous solution, and the water-soluble anionic resin (D) in this surface treatment film are substantially the same as the proportions of the water-soluble inorganic compound (A), organoalkoxysilane (B), one or more surfactants (C) selected from the group consisting of anionic surfactants having a weight-average molecular weight of 3000 or less and nonionic surfactants having a weight-average molecular weight of 3000 or less and having a cloud point of 20°C or higher in a 10% by mass aqueous solution, and the water-soluble anionic resin (D) in the surface treatment agent.

[0050] <2-1. Metallic materials and heat exchanger materials> The metal materials and heat exchanger materials to which the surface treatment agent can be applied are not particularly limited, and examples thereof include aluminum, steel, stainless steel, titanium, and alloys thereof. The surface treatment agent is particularly suitable for aluminum-containing metal materials. The material constituting the aluminum-containing metal material may be pure aluminum or an aluminum alloy.

[0051] <2-2. Cleaning process> It is preferable to preliminarily clean untreated metal materials and heat exchangers with an acidic or alkaline cleaner. Examples of acidic cleaners include an acidic aqueous solution containing at least one of nitric acid, sulfuric acid, and hydrofluoric acid. Examples of alkaline cleaners include an alkaline aqueous solution containing at least one of sodium hydroxide, sodium silicate, and sodium phosphate. To improve cleaning properties, a surfactant may be added to the alkaline aqueous solution.

[0052] Methods for cleaning metal materials and heat exchangers include, for example, immersion methods and spray methods.

[0053] <2-3. Rust prevention treatment> Rust prevention treatment may be performed after the cleaning process. Rust prevention treatment methods include chemical conversion treatment and base rust prevention treatment using a resin primer. Among these, the chemical conversion treatment agent used in the chemical conversion treatment includes a conventionally known chromate chromate treatment agent, a phosphate chromate treatment agent, or a non-chromium treatment agent. The resin primer can include a conventionally known water-soluble or water-dispersible aqueous resin. Rust prevention treatment methods include, for example, a dipping method and a spray method.

[0054] <2-4. Contact process> The method for contacting the surface treatment agent with the surface of the metal material and the heat exchanger or on the surface thereof is not particularly limited, but examples thereof include immersion, spraying, roll coating, brush coating, etc. The temperature of the surface treatment agent at this time can be about 10 to 50°C, and the contact time can be about 3 seconds to 5 minutes.

[0055] <2-5. Drying process> The method for drying the surface treatment agent is not particularly limited as long as the solvent, such as water, in the surface treatment agent evaporates. Examples include drying methods using known drying equipment, such as ovens, batch-type drying ovens, continuous hot air circulation drying ovens, conveyor-type hot air drying ovens, and electromagnetic induction heating ovens using IH heaters. The drying temperature can be 100 to 250°C, preferably 120 to 180°C. The drying time can be 10 seconds to 120 minutes, preferably 1 to 60 minutes.

[0056] <2-6. Mass of surface treatment film> The mass of the surface treatment film in the metal material and heat exchanger having the surface treatment film is not particularly limited as long as it is an amount that can exhibit the effects of the present invention. 2 It is preferable that the range is 0.05 to 3.5 g / m 2 It is more preferable that the range is 0.1 to 2.0 g / m 2 It is particularly preferable that the amount of the surface treatment film is within the range of 0.1 g / m 2 If the amount of the surface treatment film is 3.0 g / m, the metal material and the heat exchanger are sufficiently coated, and a film that can maintain the hydrophilicity, corrosion resistance, and frost resistance that are the objectives of the present invention can be obtained. 2 It is economical if:

[0057] <2-7. Post-processing process> A post-treatment process may be carried out after the formation of the surface treatment film. Examples of the post-treatment process include a lubricating oil contact process or a lubricating film formation process. More specifically, a process of contacting a lubricating oil or a lubricant with the surface treatment film on the surface of the metal material and the heat exchanger to form a lubricating film can be mentioned. In this way, a metal material and a heat exchanger having a multi-layer film can be obtained in which a lubricating oil is contacted or a lubricating film is formed on the surface treatment film. The method for contacting the lubricating oil or lubricant is not particularly limited, and examples thereof include a roll coating method, a spray method, and an immersion method.

[0058] As the lubricating oil, any known lubricant used in molding processing can be used, and as the lubricant for forming the lubricating coating, known lubricants such as water-soluble polyether, polyethylene glycol, polyoxyethylene alkyl ether, and polyoxyethylene hydrogenated castor oil ether can be used. [Example]

[0059] The present invention will be described in more detail below based on examples, but the present invention is not limited to these examples.

[0060] <1. Preparation of surface treatment agent> The inorganic compounds (A1 to A8) shown in Table 1 were prepared. A1 to A8 are water-soluble inorganic compounds, and Table 1 shows the pH when dissolved in water at 25°C at a concentration of 0.1% by mass. The colloidal silica in A8 is water-insoluble. Next, using the inorganic compounds (A1 to A8) as raw materials, composites with organoalkoxysilane were synthesized. The blending amounts of the water-soluble inorganic compound and organoalkoxysilane are shown in Table 2. A composite of the water-soluble inorganic compound and organoalkoxysilane was synthesized by heating a mixture of water, the water-soluble inorganic compound, and the organoalkoxysilane.

[0061] [Table 1]

[0062] [Table 2]

[0063] The synthesis method for the composite is described using Synthesis Example X1 in Table 2 as an example. 30 g of lithium silicate, 70 g of 3-glycidoxypropyltrimethoxysilane, and 900 g of deionized water were sequentially added to a glass vessel containing a stirrer, and the solution was heated to 40 °C to initiate the ring-opening reaction and hydrolysis of the methoxy groups. Four hours after the start of the reaction, the bath was cooled to room temperature, and the water lost by evaporation was then diluted with deionized water to obtain a 10% solids aqueous dispersion containing a composite of lithium silicate (A1) and 3-glycidoxypropyltrimethoxysilane (B1). The "solids" concentration here refers to the value measured by the atmospheric pressure heat drying method (sample weight: 1.0 g, drying temperature: 110 °C x 2 hours) in accordance with JIS K6828-1:2003.

[0064] Synthesis Examples X2 to X12 in Table 2 were also synthesized in the same manner except that the substance types and blending amounts were changed, to obtain composites of water-soluble inorganic compounds and organoalkoxysilanes in predetermined mass ratios.

[0065] The median diameters of the composites according to Synthesis Examples X1 to X12 obtained by the above procedure were measured by the dynamic light scattering method described above. The measurement results are shown in Table 2. Due to analytical precision, values ​​less than 10 nm are marked as "<10". The presence of the composites was confirmed by the multinuclear NMR spectrum measurement described above.

[0066] In addition, surfactants shown in Table 3 were prepared as nonionic or anionic surfactants, and resins shown in Table 4 were prepared as water-soluble anionic resins. Note that D5 is classified as an anionic surfactant in this specification.

[0067] [Table 3]

[0068] [Table 4]

[0069] The surface treatment agents in each Example and Comparative Example were prepared by mixing the aqueous dispersion containing the composite prepared above, a surfactant, and a water-soluble resin in the solids mass ratios shown in Tables 5 and 6. Next, 80 g of ethylene glycol monobutyl ether was added to 100 g of the resulting mixture. Then, deionized water was added to bring the total to 1000 g and the mixture was stirred. The "solids mass" referred to here refers to the value measured by the atmospheric pressure heat drying method (sample weight: 1.0 g, drying temperature: 110°C x 2 hours) in accordance with JIS K6828-1:2003. The solid masses of (A) and (B) in Tables 5 and 6 were calculated based on the solids mass ratios of the raw materials used to synthesize the composites.

[0070] [Table 5]

[0071] [Table 6]

[0072] <2. Preparation of test materials> An aluminum test piece (A1050 manufactured by Paltec Co., Ltd., dimensions: 70 mm x 150 mm, plate thickness: 0.8 mm) was prepared.

[0073] <3. Formation of surface treatment film> The test material was immersed for 3 minutes in a treatment bath containing an alkaline degreasing agent "Fine Cleaner 315E" (manufactured by Nihon Parkerizing Co., Ltd.) at a concentration of 20 g / L and a bath temperature of 60°C to remove any dirt or oil adhering to the surface, and then the remaining alkali on the surface was washed away with city water.

[0074] The washed test material was immersed in the surface treatment agent (liquid temperature: 25°C) according to each Example and Comparative Example for 30 seconds, and then hung in a blower dryer adjusted to 150°C and heated and dried for 6 minutes to form a surface treatment film on the surface of the test material, which was then cooled to room temperature to prepare an evaluation sample. The mass of the surface treatment film was 0.8 g / m 2The solid content was adjusted so that the solid content was 0.01 to 0.01. The number of evaluation samples required for the following evaluations was prepared.

[0075] <4. Hydrophilicity Evaluation Method> One microliter of deionized water was dropped onto the evaluation sample prepared above, and the contact angle of the formed water droplet was measured using a contact angle meter (DM-501, manufactured by Kyowa Interface Science Co., Ltd.). The contact angle of the evaluation sample cooled to room temperature after hydrophilic treatment was taken as the initial hydrophilicity, and the contact angle after the evaluation sample was immersed in deionized water for 240 hours, dried for 1 hour in a fan dryer adjusted to 50°C, and cooled to room temperature was taken as the durable hydrophilicity. The obtained contact angles were rated according to the following criteria, and a rating of 3 or higher was considered to be acceptable hydrophilicity, which is the objective of this invention. The results are shown in Tables 7-1 and 7-2.

[0076] <Hydrophilicity rating criteria> 5 points: Less than 10° 4 points: 10° or more and less than 20° 3 points: 20° or more, less than 30° 2 points: 30° or more, less than 40° 1 point: 40° or more

[0077] <Frost resistance evaluation method> A cooling block was placed in the chamber of a thermo-hygrostat maintained at 10°C and 50% RH. A cooling liquid at -10°C was flowed through the block, keeping the surface at -7°C. The evaluation sample was attached to the cooling block with double-sided tape, and the frost growth from the evaluation sample surface was observed under a microscope. The time it took for the frost height to reach 0.5 mm was measured. The same test was also conducted on the evaluation sample after immersion in deionized water for 240 hours. A rating of 3 or higher was considered to have good frost resistance. The results are shown in Tables 7-1 and 7-2.

[0078] <Frost resistance evaluation criteria> 5 points: Time required for frost height to reach 0.5 mm is 30 minutes or more 4 points: Time required for frost height to reach 0.5 mm is between 27 and 30 minutes. 3 points: Time required for frost height to reach 0.5 mm is between 24 and 27 minutes 2 points: Time required for frost height to reach 0.5 mm is between 21 and 24 minutes 1 point: Time to reach frost height of 0.5 mm is less than 21 minutes

[0079] <Corrosion resistance evaluation method> (1) SST The evaluation samples prepared above were exposed to salt spray testing (JIS Z2371:2015) for 240 hours, and the rust area of ​​the test material (ratio of white rust area to total area) was evaluated by visual inspection. The evaluation criteria are shown below. A rating of 3 or higher was considered to have good corrosion resistance. The results are shown in Tables 7-1 and 7-2.

[0080] <Evaluation criteria> 5 points: White rust area less than 10% 4 points: White rust area is 10% or more but less than 30% 3 points: White rust area is 30% or more but less than 50% 2 points: White rust area is 50% or more but less than 70% 1 point: white rust area of ​​70% or more

[0081] (2) SWAAT Based on the SWAAT test (ASTM G85-A3), an aqueous solution was prepared by adjusting the pH of artificial seawater (ASTM D1 141-98) to 3.0 with acetic acid. The evaluation samples prepared above were exposed to artificial seawater spray (49°C x 30 minutes) followed by wet exposure (49°C x 90 minutes), for a total of 120 minutes per cycle, for a total of 60 cycles. Afterwards, the samples were immersed in a 2% by weight aqueous chromic acid solution at 95°C for 10 minutes to remove white rust. The size and number of pits were evaluated using the rating number method based on JIS Z2371:2015. A rating of 3 or higher was considered to have good pitting corrosion resistance. The results are shown in Tables 7-1 and 7-2.

[0082] <Evaluation criteria> 5: RN is 9.5 or higher 4: RN is 9.3 or more and less than 9.5 3: RN is 9 or more and less than 9.3 2: RN is 8 or more but less than 9 1: RN less than 8

[0083] <Dispersion stability evaluation method> The surface treatment agents according to each Example and Comparative Example were stored in a thermostatic chamber at 40°C for one week, and the appearance of the liquid after storage was visually inspected and rated as follows. A rating of 3 or more was considered acceptable. Regarding dispersion stability, even if precipitation occurred, the agent was considered acceptable (3 points) if it was used after thorough stirring and redispersion, and other performance evaluation results were acceptable. The results are shown in Tables 7-1 and 7-2.

[0084] <Dispersion stability rating criteria> 5 points: no precipitation 3 points: A small amount of precipitate appears at the bottom of the container 1 point: A large amount of precipitate was generated, covering the entire bottom of the container.

[0085] [Table 7-1]

[0086] [Table 7-2]

Claims

1. The surface treatment agent comprises a water-soluble inorganic compound (A), an organoalkoxysilane (B), and one or more surfactants (C) selected from the group consisting of anionic surfactants having a weight-average molecular weight of 3,000 or less and nonionic surfactants having a weight-average molecular weight of 3,000 or less and having a cloud point of 20°C or higher in a 10% by mass aqueous solution, wherein Mc / (Ma+Mb)=0.001 to 0.3 when Ma, Mb, and Mc are the masses of (A), (B), and (C), respectively.

2. The water-soluble inorganic compound (A) is alkaline and contains one element (M1) selected from Si, V, Zr, Mo, Ti, and W, and Na, K, Li, and NH 4 and one cationic component (M2) selected from the group consisting of (M1), and a molar ratio of (M2) to (M1), (M2) / (M1), is 0.1 to 8.

0.

3. 2. The surface treatment agent according to claim 1, wherein Ma / Mb=0.25 to 4.

0.

4. 2. The surface treatment agent according to claim 1, wherein the water-soluble inorganic compound (A) and the organoalkoxysilane (B) form a composite.

5. The water-soluble inorganic compound (A) is represented by the general formula Me 2 O.nSiO 2 where Me is Na, K, Li, and NH 4 2. The surface treatment agent according to claim 1, wherein n is 0.5 to 8.

0.

6. The surface treatment agent according to claim 1 , further comprising a water-soluble anionic resin (D) having a weight-average molecular weight of 5,000 or more.

7. 7. The surface treatment agent according to claim 6, wherein the water-soluble anionic resin (D) has an acid value of 20 to 500 mgKOH / g and a weight-average molecular weight of 10,000 to 2,000,000.

8. 7. The surface treatment agent according to claim 6, wherein the water-soluble anionic resin (D) has one or more functional groups selected from an amide group and a hydroxyl group.

9. 7. The surface treatment agent according to claim 6, wherein Md / (Ma+Mb+Mc)=0.1 to 4.0, where Md is the mass of the water-soluble anionic resin (D).

10. A method for treating the surface of a metal material, comprising the step (a) of contacting the metal material with the surface treatment agent according to any one of claims 1 to 9.

11. 11. The surface treatment method for a metal material according to claim 10, further comprising, prior to the step (a), a step (b) of forming a base coating containing at least one element selected from Cr, Zr, Ti, and V on the metal material.

12. The method for surface treatment of a metal material according to claim 10, further comprising, before the step (a), a step (c) of forming a primer layer containing a resin on the metal material.

13. The method for surface treatment of a metal material according to claim 10, further comprising, after the step (a), a step (d) of drying the metal material.

14. A method for producing a surface-treated metal material, comprising a step of contacting a metal material with the surface treatment agent according to any one of claims 1 to 9 and then drying the metal material.

15. A heat exchanger using a surface-treated metal material obtained by the method for surface treatment of a metal material according to claim 10.

16. A method for treating the surface of a heat exchanger, comprising the steps of contacting the heat exchanger with the surface treatment agent according to any one of claims 1 to 9 and then drying the heat exchanger.

17. A method for producing a surface-treated heat exchanger, comprising a step of contacting the surface treatment agent according to any one of claims 1 to 9 with a heat exchanger and then drying the heat exchanger.

18. A surface-treated heat exchanger obtained by the manufacturing method according to claim 17.

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