JP6654814B2 - Hydrophilizing agent, hydrophilic film forming method and hydrophilic film - Google Patents

Description

  The present invention relates to a hydrophilic treatment agent, a method for forming a hydrophilic film, and a hydrophilic film.

  Conventionally, a technique of performing a hydrophilic treatment on the surface of a metal substrate is known. For example, in a heat exchanger using aluminum, the fin surface is subjected to a hydrophilic treatment in order to prevent problems such as generation of noise due to condensed water adhered to the fin surface and contamination due to scattering of water droplets. .

  As the hydrophilizing agent used for the hydrophilizing treatment, a polymer composition for hydrophilizing treatment containing a polymer such as a polyacrylic acid polymer and a polymer such as polyethylene oxide which forms a hydrogen bond with the polymer has been proposed. (For example, see Patent Document 1). Although this is a technique in which the hydrophilicity of the hydrophilic film is improved, the suppression of the deterioration of the hydrophilicity is not sufficient depending on the type of contaminants to be adhered. Further, the adhesion (WET adhesion) between the metal surface and the hydrophilic film in a state where water is attached is also insufficient.

  Further, a hydrophilizing agent containing a salt of carboxymethyl cellulose, N-methylol acrylamide, polyacrylic acid and polyethylene oxide, and an aqueous polymer compound having a polyoxyalkylene chain, an aqueous resin, and a hydrophilic agent containing N-methylol acrylamide Chemical treatment agents have been proposed (see, for example, Patent Documents 2 and 3). Since these compounds contain N-methylolacrylamide as a monomer, their hydrophilicity persists when contaminants adhere to them.

  Further, a monoethylenic monomer having a polyoxyalkylene chain, a (meth) acrylamide-based monoethylenic monomer, a crosslinkable unsaturated monomer having an N-methylol group such as N-methylolacrylamide and a polymerizable double bond, and other monomers (For example, see Patent Documents 4 to 6). In particular, by blending specific crosslinkable fine particles with the hydrophilizing agent, the hydrophilicity after the contaminants are adhered is increased, and the adhesion between the hydrophilic film and the metal substrate surface in a state where water is adhered is also improved. (See Patent Documents 7 and 8).

JP-A-6-322292 JP-A-6-322552 JP-A-7-102189 JP-A-8-120003 JP 2000-248225 A JP-A-2002-302644 JP 2005-2151 A JP 2014-000534 A

  As described above, when the hydrophilizing treatment agents described in Patent Documents 7 and 8 are used, the hydrophilic film formed on the metal surface has excellent adhesion between the hydrophilic film and the metal surface in a state where water is attached, and contamination It also has excellent hydrophilicity persistence when the substance is attached.

  By the way, products made of a metal substrate, including an aluminum heat exchanger, are required to be downsized. With the miniaturization of products made of metal base materials, the distance between adjacent metal base materials may be reduced. When the distance between the metal base materials is reduced, for example, in a heat exchanger, clogging with water droplets is likely to occur. Therefore, on the surface of the metal substrate, it is required to form a hydrophilic film having high hydrophilic persistence in a state where water is attached, in addition to the conventionally required hydrophilicity.

  Further, when the space between adjacent metal base materials becomes narrow, water droplets crosslink between the metal base materials, and for example, in a heat exchanger, ventilation resistance may be increased. As described above, in order to prevent water droplets from bridging between the metal base materials, it is also required that the surface of the metal base material is easy for the contacted water to flow (has a high drainage property). In particular, in a heat exchanger used in an outdoor unit in a cold region, when water droplets bridge between fin materials and the water droplets freeze, the ventilation resistance significantly increases. Further, when the frozen water droplets are melted in order to reduce the ventilation resistance caused by the frozen water droplets, excessive energy that is not directly related to heat exchange is required, and the cost is increased.

  As described above, there is a need for a technique for forming a hydrophilic film having a sufficiently long lasting hydrophilic property and drainage property on a metal substrate, but it is difficult at present to form such a hydrophilic film. .

  The present invention has been made in order to solve the above-mentioned problems, and an object thereof is to provide a hydrophilic treatment agent capable of forming a hydrophilic film having a high hydrophilic persistence in a state where water is attached and an excellent drainage property. An object of the present invention is to provide a hydrophilic film forming method using such a hydrophilic treatment agent and a hydrophilic film formed by such a hydrophilic film forming method.

  The present inventors contain a hydrophilic resin and crosslinkable fine particles, as a hydrophilic resin, a specific (meth) acrylic resin, polyvinyl alcohol, and a polyalkylene ether resin having a specific molecular weight, each containing It has been found that the use of a hydrophilizing agent in which the composition of components is adjusted to a specific range can solve the above-mentioned problems, and the present invention has been completed. More specifically, the present invention provides the following.

（式中、Ｒ^１は、水素又はメチル基を表す。Ｒ^２は、ＣＨ_２又はＣ_２Ｈ_４を表す。）
前記親水化処理剤固形分中における、前記（メタ）アクリル系樹脂（Ａ）の含有率が１０〜３０質量％であり、前記ポリビニルアルコール（Ｂ）の含有率が１０〜４０質量％であり、前記ポリアルキレンエーテル樹脂（Ｃ）の含有率が１５〜５０質量％であり、前記架橋性微粒子（Ｄ）の含有率が３０〜６５質量％である親水化処理剤を提供する。 To solve the above problems, the present invention provides:
A hydrophilic treatment agent for forming a hydrophilic film on the surface of the metal substrate,
(Meth) acrylic resin (A), polyvinyl alcohol (B), polyalkylene ether resin (C), and crosslinkable fine particles containing a repeating unit derived from an acrylic acid monomer and / or a repeating unit derived from a methacrylic acid monomer D) containing
The (meth) acrylic resin (A)
(1) not having a repeating unit derived from a monomer having a sulfo group and a repeating unit derived from a monomer having an amide group,
(2) a weight average molecular weight of 20,000 to 2,000,000,
(3) The resin solid content has an acid value of 100 to 800 mgKOH / g,
The polyalkylene ether resin (C) has a weight average molecular weight of 5,000 to 500,000,
The crosslinkable fine particles (D) are 30 to 95% by mass of a monomer (a) represented by the following formula (I), 5 to 60% by mass of a monomer (b) having a polyoxyalkylene chain and a polymerizable double bond, And copolymerized with 0 to 50% by mass of another polymerizable monomer (c),

(In the formula, R ¹ represents hydrogen or a methyl group. R ² represents CH ₂ or C ₂ H _4. )
The content of the (meth) acrylic resin (A) in the solid content of the hydrophilizing agent is 10 to 30% by mass, the content of the polyvinyl alcohol (B) is 10 to 40% by mass, Provided is a hydrophilizing agent in which the content of the polyalkylene ether resin (C) is 15 to 50% by mass and the content of the crosslinkable fine particles (D) is 30 to 65% by mass.

The present invention includes the steps of forming a conversion coating by contacting the chemical conversion treatment agent to the surface of the A aluminum substrate is contacted with the hydrophilic treatment agent to chemical conversion film obtained in about該工hydrophilic coating Forming a hydrophilic film.

  Further, the present invention provides a hydrophilic film formed on the surface of the metal substrate by the method for forming a hydrophilic film.

  Further, it is preferable that the thickness of the hydrophilic film is 0.3 to 10 μm.

  The hydrophilic film formed on the metal surface by using the hydrophilizing agent of the present invention has extremely high hydrophilic persistence and excellent drainage.

  Hereinafter, embodiments of the present invention will be described. Note that the present invention is not limited to the following embodiments.

<Metal base material>
Examples of the metal substrate on which a hydrophilic film is formed by the hydrophilic treatment agent according to the present invention include an aluminum substrate. The aluminum base is a base made of aluminum. Here, “aluminum” is a general term for metals and alloys mainly composed of aluminum, and is a concept including pure aluminum and aluminum alloys.

  Examples of the aluminum base include an aluminum heat exchanger. In the heat exchanger, from the viewpoint of improving the heat exchange efficiency, a plurality of fins are arranged at narrow intervals so as to increase the surface area as much as possible, and tubes for supplying the refrigerant are arranged intricately in these fins.

<Hydrophilic treatment agent>
The hydrophilizing agent according to the present invention contains a specific hydrophilic resin and specific crosslinkable fine particles at a specific ratio. When the hydrophilizing treatment agent contains these components, the formed hydrophilic film has high hydrophilic persistence in a state where water is attached and excellent drainage.

[Hydrophilic resin]
The hydrophilic resin in the present invention is a (meth) acrylic resin (A) containing a repeating unit derived from an acrylic acid monomer and / or a repeating unit derived from a methacrylic acid monomer, a polyvinyl alcohol (B), and a polyalkylene ether. It is essential to contain the resin (C).

  The (meth) acrylic resin (A) contains a repeating unit derived from at least one of an acrylic acid monomer and a methacrylic acid monomer. The total content of the repeating units derived from the acrylic acid monomer and the repeating units derived from the methacrylic acid monomer is not particularly limited, but is preferably 50 to 100% by mass.

  The (meth) acrylic resin (A) may contain a repeating unit other than a repeating unit derived from an acrylic acid monomer and a repeating unit derived from a methacrylic acid monomer. For example, it is a derivative of an acrylic acid monomer or a methacrylic acid monomer.

  Specifically, monomers having one polymerizable unsaturated bond in the molecule include methyl methacrylate, n-butyl methacrylate, i-butyl methacrylate, 2-ethylhexyl methacrylate, isononyl methacrylate, n-octyl methacrylate, lauryl methacrylate , Alkyl methacrylates such as stearyl methacrylate, methyl acrylate, n-butyl acrylate, i-butyl acrylate, 2-ethylhexyl acrylate, isononyl acrylate, alkyl acrylates such as n-octyl acrylate, aralkyl methacrylates such as benzyl methacrylate, benzyl acrylates and the like Alkoxyalkyl methacrylates such as aralkyl acrylate and butoxyethyl methacrylate, butoxyethyl acryle Alkoxyalkyl acrylates such as bets and the like. These may be used alone or in combination of two or more.

  In addition, the (meth) acrylic resin (A) may contain a component other than the above-mentioned monomer, but a repeating unit derived from a monomer having a sulfo group and a repeating unit derived from a monomer having an amide group It is more preferable not to include. If they are contained, it tends to be difficult to suppress the generation of odor.

  The solid content of the (meth) acrylic resin (A) in the total solid content of the hydrophilizing agent is 10 to 30% by mass. When the solid content of the (meth) acrylic resin (A) is less than 10% by mass, the adhesion between the hydrophilic film and the metal surface and the drainage property are reduced. When the solid content of the (meth) acrylic resin (A) exceeds 30% by mass, the hydrophilicity persistence and the drainage property decrease. When the solid content of the (meth) acrylic resin (A) is within the above range, most of the (meth) acrylic resin (A) is present at the boundary with the metal surface, and The (meth) acrylic resin (A) can be prevented from being present.

  The acid value of the (meth) acrylic resin (A) is 100 to 800 mgKOH / g. When the acid value of the (meth) acrylic resin (A) is less than 100 mgKOH / g, the adhesion between the hydrophilic film and the metal surface decreases. When the acid value of the (meth) acrylic resin (A) exceeds 800 mgKOH / g, the hydrophilic film adsorbs acid components in the air, and the odor resistance is reduced.

  The weight average molecular weight of the (meth) acrylic resin (A) is 20,000 to 2,000,000. When the (meth) acrylic resin (A) has a weight average molecular weight of less than 20,000, the hydrophilicity persistence is reduced. When the weight average molecular weight of the (meth) acrylic resin (A) exceeds 2,000,000, the viscosity of the hydrophilizing agent becomes high, and the workability is poor. If the weight average molecular weight of the (meth) acrylic resin (A) is small, the (meth) acrylic resin (A) existing near the boundary with the metal surface when the water comes into contact with the hydrophilic film becomes a hydrophilic film. It moves to the surface side of. When the (meth) acrylic resin (A) moves to the surface side of the hydrophilic film, the adhesion between the hydrophilic film and the metal surface decreases. On the other hand, if the weight average molecular weight is too small, the adhesiveness between the hydrophilic film and the metal surface is reduced because it is eluted in water. When the weight average molecular weight of the (meth) acrylic resin (A) is within the above range, the problem of a decrease in adhesion between the hydrophilic film and the metal surface does not occur even if the state where water adheres to the surface of the hydrophilic film continues. . The more preferable range of the weight average molecular weight of the (meth) acrylic resin (A) is 20,000 to 100,000. The value of the weight average molecular weight employs a value measured by a gel permeation chromatography (GPC) method. Specifically, a solution obtained by dissolving 0.4 part by weight of a resin sample with respect to 100 parts by weight of tetrahydrofuran is used as a sample solution, and this is used as an LC-08 (A-5432) type GPC manufactured by Nippon Kagaku Kogyo Co., Ltd. And calculated in terms of polystyrene.

  The polyvinyl alcohol (B) contained in the hydrophilizing agent is obtained by saponifying a polymer obtained by polymerizing polyvinyl acetate. In the present invention, the degree of polymerization of the polyvinyl alcohol (B) is not particularly limited, but is preferably 300 to 2,000 or less. The saponification degree of the polyvinyl alcohol (B) is preferably 95% or more.

The solid content of the polyvinyl alcohol (B) in the total solid content of the hydrophilizing agent is 5 to 40% by mass. If the content is less than 5 % by mass, there is a possibility that the hydrophilicity retention and drainage properties may be reduced. When the content exceeds 40% by mass, the hydrophilic film becomes less likely to exhibit hydrophilicity (initial hydrophilicity and hydrophilic continuity), and the drainage property also decreases. The content is preferably 10 to 25% by mass.

  The polyalkylene ether resin (C) contained in the hydrophilizing agent is a component that imparts hydrophilicity and lubricity to the hydrophilic film. By imparting lubricity to the hydrophilic film, workability when pressing the surface of the aluminum fin material or the like is improved.

  The polyalkylene ether resin (C) is not particularly limited as long as the polymerization average molecular weight falls within the above range. Examples of the polyalkylene ether resin (C) include polyoxyethylene (polyethylene oxide, polyethylene glycol), polyoxypropylene, and condensates thereof. Further, these polyalkylene ether resins may be used as a mixture. As the polyalkylene ether resin (C), it is preferable to use polyoxyethylene from the viewpoint of enhancing the hydrophilicity of the formed hydrophilic film.

  The polyalkylene ether resin (C) has a weight average molecular weight of 5,000 to 500,000. When the weight average molecular weight of the polyalkylene ether resin (C) is less than 5,000, the solubility of the polyalkylene ether resin (C) in water becomes too high, and the hydrophilic persistence of the formed hydrophilic film decreases. On the other hand, when the weight average molecular weight of the polyalkylene ether resin (C) exceeds 500,000, the viscosity of the polyalkylene ether resin (C) increases, and the coatability deteriorates. The polyalkylene ether resin (C) preferably has a weight average molecular weight of 5,000 to 300,000. As described above, since the polyalkylene ether resin (C) has a small weight-average molecular weight, the hydrophilicity of the polyalkylene ether resin (C) increases, so that the hydrophilic film has higher hydrophilicity (initial hydrophilicity and hydrophilic durability). ) Can be expressed.

  The solid content of the polyalkylene ether resin (C) in the solid content of the hydrophilizing agent is 15 to 50% by mass. When the content is less than 15% by mass, the hydrophilic film does not exhibit hydrophilicity. If the content exceeds 50% by mass, the film components may be eluted into water, and the decontamination property is also reduced.

In the present invention, the solid content of the polyalkylene ether resin (C) in the solid content of the hydrophilizing agent is increased as described above. As a result, the polyvinyl alcohol (B), which forms the basis of the formed hydrophilic film and enhances the adhesion to the aluminum surface, and the polyalkylene ether resin (C) existing on the surface of the hydrophilic film are densely phase-separated to form a hydrophilic film. It is considered that the hydrophilic film expresses high hydrophilicity (initial hydrophilicity and hydrophilic persistence) by increasing the surface irregularities.
When the solid content of the polyalkylene ether resin (C) is increased, the adhesion between the hydrophilic film and the metal surface tends to decrease. In the present invention, the adhesion between the hydrophilic film and the metal surface is improved by increasing the solid content of the (meth) acrylic resin (A) existing near the boundary with the metal surface to be within the above range. Let it.

[Crosslinkable fine particles]
The crosslinkable fine particles (D) in the present invention include a monomer (a) represented by the following formula (I), a monomer (b) having a polyoxyalkylene chain and a polymerizable double bond, and other polymerizable monomers ( Resin particles comprising a copolymer obtained by copolymerizing the monomer component comprising c). In the crosslinkable fine particles (D), the methylol group or the ethylol group of the above (a) reacts with the functional group such as the carboxyl group or the hydroxyl group of the above (b), or the methylol group or the ethylol group undergoes a condensation reaction. And (c) the carboxyl group and the hydroxyl group. For this reason, when the crosslinkable fine particles (D) are used as a component of the hydrophilizing agent, a strong water-insoluble hydrophilic film can be formed on the metal surface. Further, since the crosslinkable fine particles (D) have high hydrophilicity and relatively many unreacted functional groups, when used as a component of the hydrophilizing agent, they react with other hydrophilic resins and have a hydrophilic property. Without impairing, the hydrophilicity persistence after the contaminant adheres can be greatly improved. Further, since the crosslinkable fine particles (D) have a relatively small swelling ratio with respect to water, dissolution of the formed hydrophilic film in water is also suppressed.

  The monomer (a) represented by the above formula (I) is N-methylolacrylamide, N-methylolmethacrylamide, N-hydroxyethylacrylamide or N-hydroxyethylmethacrylamide. When a hydrophilic treatment agent containing the crosslinkable fine particles (D) obtained by using the monomer (a) represented by the above formula (I) is used, a hydrophilic film excellent in the above-mentioned hydrophilic persistence and the above-mentioned adhesiveness is obtained. Can be formed. These may be used alone or in combination of two or more.

  The crosslinkable fine particles (D) are obtained by copolymerizing a monomer component containing 30 to 95% by mass of the monomer (a) represented by the formula (I). When the content is less than 30% by mass, there is a possibility that the hydrophilicity persistence after the contaminants of the hydrophilic film have adhered may be reduced. If it exceeds 95% by mass, production may be difficult. Since the monomer (a) represented by the above formula (I) is compounded in the above range, it functions not only as a crosslinking component but also as a main component of a hydrophilic film forming component. That is, when it is blended in order to exhibit only the function as a crosslinking component, it is usually used in a blending amount smaller than the above range, but in the crosslinkable fine particles (D) of the present invention, the formula (I) By using the monomer (a) represented in the above range, the methylol group and the ethylol group remain in the crosslinkable fine particles even after the copolymerization. For this reason, when a hydrophilic film is formed using the hydrophilizing agent containing the crosslinkable fine particles (D), it reacts with other hydrophilic resins to obtain strong adhesion and hydrophilic durability. Therefore, even after a contaminant such as a lubricant for plastics such as palmitic acid, stearic acid or paraffinic acid, or diisooctyl phthalate adheres to the formed hydrophilic film, the hydrophilicity of the hydrophilic film can be sufficiently maintained.

  In addition, the crosslinking degree of the crosslinkable fine particles obtained by blending the monomer (a) represented by the above formula (I) increases due to an increase in the blending amount. For this reason, dissolution of the formed hydrophilic film by moisture is suppressed, and a film having excellent adhesion (adhesion when the film is exposed to moisture) can be formed.

  The amount of the monomer (a) represented by the above formula (I) is 30 to 95% by mass based on 100% by mass of the monomer component. The lower limit is preferably 40% by mass, and the upper limit is preferably 80% by mass.

The monomer (b) is not particularly limited as long as it has a polyoxyalkylene chain and a polymerizable double bond, and may be a compound represented by the following formula (II) and / or the following formula (III). preferable. Thereby, water-dispersible stable crosslinkable fine particles having excellent hydrophilicity can be obtained.

In the above formula (II), R ³ and R ⁴ are the same or different and represent hydrogen or a methyl group. R ⁵ represents hydrogen, a methyl group, SO ₃ H, SO ₃ Na, or SO ₃ NH ₄ .

  In the above formula (II), n represents an integer of 6 to 300. When it is less than 6, dispersion stability and hydrophilicity are insufficient, and when it exceeds 300, production becomes difficult. The lower limit is preferably 30 and the upper limit is preferably 200.

In the formula (III), R ⁶ and R ⁸ are the same or different and represent hydrogen or a methyl group. R ⁹ represents hydrogen, a methyl group, SO ₃ H, SO ₃ Na, or SO ₃ NH ₄ . R ⁷ represents CH ₂ or a benzene ring (the following chemical formula (IV)).

  In the above formula (III), m represents an integer of 6 to 300. When it is less than 6, dispersion stability and hydrophilicity are insufficient, and when it exceeds 300, production becomes difficult. The lower limit is preferably 30 and the upper limit is preferably 200.

  The monomer (b) is not particularly limited. For example, in addition to the compounds represented by the formulas (II) and (III), methoxypolyethylene glycol monomethacrylate, methoxypolyethylene glycol monoacrylate, octoxypolyethylene glycol- Polypropylene glycol monoacrylate and the like can also be mentioned. These may be used alone or in combination of two or more.

  The monomer (b) is preferably a compound containing a polyoxyalkylene chain in an amount of 50% by mass or more. Here, 50% by mass or more means that the total solids mass of the polyoxyalkylene chain portion is 50% by mass or more in 100% by mass of the solid content of the monomer (b) used. If it is less than 50% by mass, the hydrophilicity of the hydrophilic film may be reduced. More preferably, the monomer (b) contains a polyoxyalkylene chain in an amount of 80 to 99% by mass.

  The amount of the monomer (b) is 5 to 60% by mass based on 100% by mass of the monomer component. If it is less than 5% by mass, the dispersibility of the crosslinkable fine particles in the hydrophilizing agent will be reduced, and the hydrophilicity of the hydrophilic film will be reduced. If it exceeds 60% by mass, the adhesion of the hydrophilic film is insufficient, and the durability of the hydrophilic film after the contaminants adhere is reduced. The lower limit is preferably 10% by mass, and the upper limit is preferably 40% by mass.

  The other polymerizable monomer (c) has a polymerizable unsaturated bond in one molecule and can be copolymerized with the monomer (a) represented by the formula (I) and the monomer (b). The compound is not particularly limited as long as it is a compound. For example, acrylic acid, methacrylic acid, itaconic acid, maleic acid, vinyl monomers such as vinyl acetate group, 2-hydroxyethyl acrylate, hydroxypropyl acrylate, N-vinylacetamide, N- Vinyl formamide, N-vinyl pyrrolidone, N-vinyl imidazole, acrylonitrile, methyl acrylate, methyl methacrylate, styrene, an unsaturated double bond-containing surfactant, acrylamide, methacrylamide, N-methyl acrylamide, N-vinyl sulfonic acid, N-allyl sulfonic acid, sodium styrene sulfonic acid, 2 acrylic Amide 2-methylpropane sulfonic acid, and the like. Unsaturated monomers used in ordinary radical polymerization, such as acrylates and methacrylates other than methyl acrylate and methyl methacrylate, can also be used. Among them, acrylic acid and methacrylic acid are preferable from the viewpoint that the hydrophilicity of the obtained crosslinkable fine particles can be improved. These may be used alone or in combination of two or more.

  The compounding amount of the other polymerizable monomer (c) is 0 to 50% by mass relative to 100% by mass of the monomer component. When the content exceeds 50% by mass, the hydrophilicity and crosslinkability of the obtained crosslinkable fine particles (D) decrease, and the hydrophilic persistence after the contaminant of the hydrophilic film adheres decreases. The upper limit is preferably 30% by mass.

The crosslinkable fine particles (D) of the present invention preferably have a water swelling ratio of 1.0 to 1.5. Thereby, when the hydrophilic film is formed, even if the hydrophilic film is exposed to moisture, a decrease in the adhesion between the hydrophilic film and the metal surface is suppressed. The water swelling ratio of 1.5 or less can be obtained by appropriately adjusting the reaction conditions by mixing the monomer (a), the monomer (b), and the other polymerizable monomer (c) represented by the above formula (I) at the above-described mixing ratio. It can be obtained by setting. The water swelling ratio is more preferably from 1.0 to 1.3. In addition, the water swelling ratio in this specification is a value calculated as water swelling ratio = particle size in aqueous solution / particle size in solvent. The particle diameter (D ₅₀ ) is a value measured using an electrophoretic light scattering photometer, photo ELS-800 (manufactured by Otsuka Electronics Co., Ltd.).

  The crosslinkable fine particles (D) of the present invention include, for example, 30 to 95% by mass of the N-methylol (meth) acrylamide (a), the monomer (b) 5 to 60 having a polyoxyalkylene chain and a polymerizable double bond. % By mass and 0 to 50% by mass of the above other polymerizable monomer (c) in the absence of a dispersion stabilizer in the presence of a water-miscible organic compound which dissolves the monomer used but does not substantially dissolve the copolymer formed. It can be produced by polymerizing in a solvent or a water-miscible organic solvent / water mixed solvent.

  In the polymerization in the production of the crosslinkable fine particles (D), a dispersant may be used in combination. Examples of the dispersant include a dispersion resin such as polyvinylpyrrolidone, polyvinyl alcohol, and polycarboxylic acid, and various surfactants such as anions, cations, and nonions.

  In the production of the crosslinkable fine particles (D) of the present invention, the copolymerization of the monomer component consisting of the above (a), (b) and (c) is carried out by alkylene glycol monoalkyl ether (for example, ethylene glycol monobutyl ether and the like). And methoxypropanol, and a mixed solvent of these and water.

  The copolymerization of the monomer components (a), (b) and (c) is usually carried out in the presence of a radical polymerization initiator. The radical polymerization initiator is not particularly limited, and any commonly used radical polymerization initiator can be used. For example, peroxides such as benzoyl peroxide, lauroyl peroxide, di-t-butyl peroxide, cumene hydroperoxide, t-butyl peroctoate, t-butyl peroxy 2-ethylhexanoate; 2,2'-azobis Isobutyronitrile, 2,2'-azobis (2,4-dimethylvaleronitrile), 2,2'-azobis (4-methoxy-2,4-dimethylvaleronitrile), dimethyl 2,2'-azobisiso Azo compounds such as butyrate and 4,4'-azobis (4-cyanopentanoic acid); 2,2'-azobis (2-amidinopropane) dihydrochloride, 2,2'-azobis (NN-) Amidines such as dimethyleneisobutylamidine) and 2,2'-azobis (NN-dimethyleneisobutylamidine) dihydrochloride Compounds; potassium persulfate, persulfate-based initiator or sodium thiosulfate to such ammonium persulfate, can be given in combination with the system, such as an amine or the like. These may be used alone or in combination of two or more. The amount used can usually be in the range of 0.2 to 5% by mass based on the total amount of the monomers.

  The polymerization temperature in the above copolymerization can be changed depending on the type of the polymerization initiator to be used and the like, but usually, a temperature in the range of 70 to 140 ° C is appropriate. If the temperature is lower than 70 ° C., the crosslinking property becomes insufficient, and if the temperature exceeds 140 ° C., it is difficult to control the reaction. The lower limit is more preferably 90 ° C., and the upper limit is more preferably 120 ° C. The reaction time is usually from 0.2 to 5 hours. If the time is less than 0.2 hours, the crosslinking property becomes insufficient, and if the time exceeds 5 hours, the reaction does not change, which is economically disadvantageous. By setting the polymerization temperature to 90 ° C. or higher, intraparticle crosslinking can be advanced. When the polymerization temperature is lower than 70 ° C., usually, the intra-particle crosslinking reaction hardly progresses during the polymerization. An operation for promoting intraparticle crosslinking is performed.

  Further, a crosslinking reaction catalyst may be added to the polymerization reaction system as needed in order to make the intraparticle crosslinking reaction of the polymer particles proceed more quickly during or after the polymerization reaction. Examples of the crosslinking reaction catalyst include a strong acid catalyst such as dodecylbenzenesulfonic acid and paratoluenesulfonic acid; and a strong acid catalyst containing a polymerizable double bond such as sulfoethyl methacrylate.

  The volume average particle diameter of the crosslinkable fine particles obtained as described above is not particularly limited, but is generally in the range of 0.03 to 1 μm, preferably 0.05 to 0.6 μm from the viewpoint of the stability of the crosslinkable fine particles. Is within.

  The hydrophilizing treatment agent containing the above-mentioned crosslinkable fine particles and a hydrophilic resin can form a hydrophilic film having excellent hydrophilic durability and adhesion. The above-mentioned hydrophilizing agent is capable of forming a hydrophilic film having excellent hydrophilicity persistence and adhesion when used for a metal, particularly aluminum or an alloy thereof.

  The content of the crosslinkable fine particles (D) in the total solid content of the hydrophilic treatment agent is 30 to 65% by mass. When the content of the crosslinkable fine particles (D) is less than 30% by mass, the drainage property of the formed hydrophilic film is reduced, and the contaminant removal property is also reduced. On the other hand, when the content of the crosslinkable fine particles (D) exceeds 65% by mass, the hydrophilicity of the formed hydrophilic film decreases.

  In the present invention, the content of the crosslinkable fine particles (D) in the solid content of the hydrophilizing agent is increased as described above. Thereby, the unevenness of the surface of the hydrophilic film formed by dense phase separation between the polyvinyl alcohol (B) that enhances the adhesion to the aluminum surface and the polyalkylene ether resin (C) existing on the surface of the hydrophilic film. Crosslinkable fine particles (D) enter into the concave portions. It is considered that when the crosslinkable fine particles (D) containing a large amount of the hydrophilizing agent enter the concave portions of the unevenness of the hydrophilic film surface, the surface of the hydrophilic film surface becomes flat and the drainage property of the hydrophilic film is improved. .

[Other ingredients]
A pigment can be added to the hydrophilic treatment agent for the purpose of forming a colored hydrophilic film. The pigment to be added is not particularly limited, and commonly used coloring pigments such as inorganic pigments and organic pigments can be used.

  The above-mentioned hydrophilizing agent may be added in necessary amounts of the following other components depending on the function to be added. For example, hydrophilic additives such as surfactants, colloidal silica, titanium oxide, and sugars; prevention of tannic acid, imidazoles, triazines, triazoles, guanines, hydrazines, phenolic resins, zirconium compounds, silane coupling agents, and the like. Rust additives; melamine resins, epoxy resins, blocked isocyanates, amines, phenolic resins, silica, aluminum, zirconium, and other crosslinking agents; antibacterial agents, dispersants, lubricants, deodorants, solvents, and the like.

<Method for forming hydrophilic film>
By using the hydrophilic film forming method according to the present invention, it is possible to form a hydrophilic film that exhibits high hydrophilic persistence in a state where water is attached and also has excellent drainage properties. In particular, the method for forming a hydrophilic film according to the present invention is a method that can be suitably applied to aluminum or an alloy thereof. In addition, since the above-mentioned effect is exerted by using the above-mentioned specific hydrophilizing agent, a general method can be adopted as a method for forming a hydrophilic film.

  In a general method of forming a hydrophilic film, first, the surface of a metal substrate is first degreased. Next, a chemical conversion film is formed by contacting the chemical conversion treatment agent, and a step of forming a hydrophilic film by contacting the hydrophilization treatment agent with the chemical conversion film obtained in the above step is performed.

  The degreasing treatment may be any of alkali degreasing with an alkali solution such as sodium hydroxide, sodium carbonate, sodium silicate, and sodium phosphate. Examples of the chemical conversion treatment include phosphoric acid chromate treatment, coating type chromate treatment, and non-chromate treatment. The above-mentioned phosphoric acid chromate treatment can be carried out using a treatment liquid obtained by adding an additive to chromic anhydride and phosphoric acid. The phosphoric acid chromate treatment can be performed by dipping in a treatment liquid, spraying the treatment liquid, or the like. Examples of the corrosion-resistant resin primer include acrylic, epoxy, polyester, phenol or urethane resin primer treatment.

The conversion film obtained by the phosphoric acid chromate treatment preferably has a chromium (Cr) amount of 3 to 50 mg / m ² . If it is less than 3 mg / m ² , the rust-preventive property is insufficient, and if it exceeds 50 mg / m ² , a reaction with the hydrophilic film occurs to lower the hydrophilicity. The metal such as aluminum or aluminum alloy on which the chemical conversion film is formed is usually washed with water. The water washing at this time is preferably performed in about 10 to 30 seconds.

The treating agent used in the coating type chromate treatment is a chromate treating agent using a coating treatment such as a roll coater. In this case, the amount of chromium in the film is preferably 5 to 30 mg / m ² .

  The treating agent used for the non-chromate treatment is a treating agent that does not contain chromium, and examples thereof include a zirconium-based treating agent. Examples of the zirconium-based treating agent include a mixture of polyacrylic acid and zircon fluoride.

The amount of Zr in the film obtained by the zirconium-based treating agent is preferably 0.1 to 40 mg / m ² . If it is less than 0.1 mg / m ² , the corrosion resistance is insufficient, and if it exceeds 40 mg / m ² , it is uneconomical. When the zirconium-based treatment is performed on top of the chromate treatment, the effect is even greater.

  Usually, hydrophilicity and corrosion resistance are required on the surface of the aluminum base material. Generally, the more excellent the hydrophilicity, the lower the corrosion resistance. Therefore, in the method of forming a hydrophilic film according to the present embodiment, before forming the hydrophilic film, in order to form a corrosion-resistant film on the base, after a chemical conversion treatment, perform a corrosion-resistant surface treatment by a primer treatment with an organic resin. Is preferred.

  The method for forming a hydrophilic film according to the present invention includes a step of applying the above-mentioned hydrophilizing treatment agent on the surface of a metal substrate made of aluminum or an aluminum alloy or the like that has been subjected to the above-mentioned chemical conversion treatment. Examples of the method of application include a roll coating method, a bar coating method, a dipping method, a spray method, and a brush coating method. After application, it is preferable to obtain a hydrophilic film by drying and baking at a temperature of 120 to 300 ° C. for 3 seconds to 60 minutes. If the baking temperature is lower than 120 ° C., sufficient film-forming properties cannot be obtained, and the film may be dissolved after immersion in water. When the temperature exceeds 300 ° C., the resin is decomposed, and the hydrophilicity of the hydrophilic film may be impaired.

<Hydrophilic film>
The hydrophilic film formed by the above-mentioned method for forming a hydrophilic film is a film formed on the surface of a metal, particularly aluminum and its alloy, and has excellent hydrophilicity, particularly excellent hydrophilic persistence after adhesion of contaminants, and excellent adhesion. Is also an excellent film.

  The hydrophilic film preferably has a thickness of 0.3 to 10 μm. When the film thickness of the hydrophilic film is less than 0.3 μm, the hydrophilicity and the hydrophilic durability tend to decrease. When the film thickness of the hydrophilic film is less than 10 μm, the drainage property tends to decrease.

  Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples.

<Material>
PAA-1: polyacrylic acid (weight average molecular weight: 20,000, acid value 780 mg KOH / g)
PVA: polyvinyl alcohol (weight average molecular weight: 20,000, degree of saponification: 98.5)
PEO (Comparative Example 10): polyethylene oxide (weight average molecular weight: 500000)
PEG: polyethylene glycol (weight average molecular weight: 20,000)
Resin particles: crosslinkable fine particles (manufacturing method will be described later)

[Method for producing crosslinkable fine particles]
A monomer solution obtained by dissolving 60 parts by mass of N-methylolacrylamide, 20 parts by mass of methoxypolyethylene glycol monomethacrylate (a polyethylene chain having 100 repeating units), 10 parts by mass of acrylic acid, and 10 parts by mass of acrylamide in 200 parts by mass of methoxypropanol; And a solution in which 1 part by mass of “ACVA” (manufactured by Otsuka Chemical Co., Ltd., azo-based initiator) was dissolved in 50 parts by mass of methoxypropanol. The mixture was added dropwise over a period of time, and the mixture was further heated and stirred for 1 hour to polymerize. In the obtained dispersion, the average particle diameter of the crosslinkable fine particles was 350 nm, the water swelling ratio of the crosslinkable fine particles was 1.15, and 4 was 18 seconds, and the solid concentration was 20% by mass.

<Preparation of hydrophilizing agent>
The components shown in Tables 1 and 2 were mixed at the ratios shown in Tables 1 and 2 (content (unit: mass%) in the solid content of the hydrophilizing agent) to be used in the Examples. And the hydrophilizing agent used for the comparative example was prepared.

<Preparation of Test Plates of Examples and Comparative Examples>
A 1000 mm aluminum material of 150 mm × 200 mm × 0.13 mm is degreased with a 1% solution of Surf Cleaner EC370 manufactured by Nippon Paint Co. at 70 ° C. for 5 seconds, and a 10% solution of Alsurf 4130 manufactured by Nippon Paint Co., Ltd. is used. Phosphoric acid chromate treatment was performed at 40 ° C. for 5 seconds. Next, each of the hydrophilizing treatment agents obtained above was adjusted to a solid content of 5%, and this was applied to the above aluminum material with a bar coater # 4, and dried by heating at 220 ° C. for 20 seconds. Was prepared. The amount of the hydrophilic treatment agent applied was adjusted so that the film thickness of the dried hydrophilic film was 1 μm. Each of the obtained test plates was subjected to the following evaluation.

<Evaluation of initial hydrophilicity>
The contact angle of the test plate with a water drop was evaluated. The water contact angle was measured using an automatic contact angle meter (model number: DSA20E, manufactured by KRUSS). The measured contact angle is the contact angle between the test plate and the water droplet 30 seconds after dropping in a room temperature environment. The evaluation results are shown in Tables 1 and 2. If the contact angle is less than 10 °, it is recognized that the hydrophilicity is good.

<Evaluation of hydrophilic sustainability>
The test plate was immersed in pure water for 240 hours, pulled up, and dried. Subsequently, the water contact angle of the dried test plate with a water droplet was measured. The contact angle was measured using an automatic contact angle meter (model number: DSA20E, manufactured by KRUSS). The measured contact angle is the contact angle between the test plate and the water droplet 30 seconds after dropping in a room temperature environment. The evaluation results are shown in Tables 1 and 2. If the water contact angle is less than 10 °, it is recognized that the hydrophilicity persistence is good.

<Evaluation of WET adhesion>
Pure water was sprayed on the test plate, and the film was rubbed by applying a load of about 500 g with a finger. One reciprocation was defined as one time, and the number of times until the substrate of the test plate was exposed was evaluated. The evaluation results are shown in Tables 1 and 2. If the number of times until the substrate of the test plate is exposed is 8 or more, it is recognized that the adhesion is good.

<Evaluation of drainage>
A 10 μL water drop was placed on a test plate placed horizontally. Subsequently, the test plate was set upright, the time required for the water droplet to move down 8 cm was measured, and the drainage property was evaluated. The evaluation results are shown in Tables 1 and 2. If the measured time is less than 10 seconds, it is recognized that drainage is good.

<Evaluation of decontamination property>
The test plate was immersed in pure water for 24 hours, pulled up, and dried. Subsequently, the dried test plate was dissolved in 3 parts by mass of stearic acid, 3 parts by mass of 1-octadecanol, 3 parts by mass of palmitic acid and 3 parts by mass of bis (2-ethylhexyl) phthalate with 1188 parts by mass of trichloroethylene. For 30 seconds. Pure water was sprayed onto the test plate that was pulled up after infiltration and air-dried, and then air-dried, and the water contact angle of the test plate with water droplets was measured. The measurement of the contact angle was performed using an automatic contact angle meter (model number: DSA20E, manufactured by KRUSS). In a room temperature environment, the contact angle with a water droplet 30 seconds after the dropping was measured, and evaluated according to the following criteria. The evaluation results are shown in Tables 1 and 2. When the water contact angle is B or more, it is recognized that the decontamination property is good.
(Evaluation criteria)
A: water contact angle is 20 ° or less B: more than 20 °, 30 ° or less C: more than 30 °, D: more than 50 ° D: more than 50 °

<Preparation of test plate of test example>
As shown in Table 3, a test plate of a test example was produced using the hydrophilizing agent of Example 1 , Reference Example 2 , Example 3 or 4 . The test plates of the test examples were prepared in the same manner as the test plates of the examples and comparative examples, except that the thickness of the formed hydrophilic film after drying was changed to the film thickness shown in Table 3. . Each of the obtained test plates was subjected to the same evaluation as the test plates of Examples and Comparative Examples. Table 3 shows the evaluation results.

From a comparison between Reference Example 1 and Comparative Example 1, it was found that the hydrophilic film of Reference Example 1 was more excellent in WET adhesion, drainage properties, and contamination removal properties. From a comparison between Example 1 and Comparative Example 2, it was found that the hydrophilic film of Example 1 was more excellent in WET adhesion, hydrophilicity, drainage, and contamination removal. From these results, when the solid content of the (meth) acrylic resin (A) contained in the hydrophilic treatment agent is 10 to 30% by mass, the formed hydrophilic film has hydrophilicity and WET adhesion. It was confirmed that it had excellent drainage and decontamination properties.

From a comparison between Example 2 and Comparative Example 3, it was found that the hydrophilic film of Example 2 was more excellent in hydrophilicity, WET adhesion, drainage properties and contamination removal properties. From a comparison between Reference Example 2 and Comparative Example 4, it was found that the hydrophilic film of Reference Example 2 was more excellent in drainage property and contamination removal property. From these results, when the solid content of the polyvinyl alcohol (B) contained in the hydrophilizing treatment agent is 10 to 40% by mass, the formed hydrophilic film has hydrophilicity, WET adhesion, drainage, and It was confirmed that it had excellent decontamination properties.

From a comparison between Example 3 and Comparative Example 5, it was found that the hydrophilic film of Example 3 was more excellent in hydrophilicity, hydrophilic persistence and drainage. From a comparison between Reference Example 3 and Comparative Example 6, it was found that the hydrophilic film of Reference Example 3 was more excellent in hydrophilic persistence, WET adhesion, and stain removal properties. From these results, when the hydrophilizing treatment agent contains the polyalkylene ether resin (C) in an amount of 15 to 50% by mass, the formed hydrophilic film has hydrophilicity, long-lasting hydrophilicity, wet adhesion, drainage, and contamination. Excellent removability was confirmed.

From a comparison between Example 4 and Comparative Example 7, it was found that the hydrophilic film of Example 4 was more excellent in hydrophilicity, WET adhesion, drainage properties and contamination removal properties. In addition, a comparison between Reference Example 4 and Comparative Example 8 showed that the hydrophilic film of Reference Example 4 had better drainage properties. From these results, it can be seen that when the hydrophilizing treatment agent contains the crosslinkable fine particles (D) in an amount of 30 to 65% by mass, the formed hydrophilic film is excellent in hydrophilicity, WET adhesion, drainage, and contamination removal. Was confirmed.

  From a comparison between Test Example 1 and Test Example 9, it was found that the hydrophilic film of Test Example 1 was more excellent in hydrophilicity and stain removability. In addition, from a comparison between Test Example 2 and Test Example 10, it was found that the hydrophilic film of Test Example 2 was more excellent in hydrophilicity persistence, WET adhesion, drainage properties, and stain removal properties. From these results, it was confirmed that by setting the film thickness of the hydrophilic film to 0.3 to 10 μm, hydrophilicity, hydrophilicity persistence, WET adhesion, drainage properties, and stain removal properties can be improved.

  ADVANTAGE OF THE INVENTION According to the hydrophilic treatment agent which concerns on this invention, the hydrophilic film which has high hydrophilic persistence in the state which water adhered, and excellent drainage can be formed on a metal surface. For this reason, the hydrophilic treatment agent according to the present invention can be preferably used particularly for forming a hydrophilic film on the surface of a fin of a heat exchanger such as an air conditioner.

Claims (4)

A hydrophilic treatment agent for forming a hydrophilic film on the surface of the metal substrate,
(Meth) acrylic resin (A), polyvinyl alcohol (B), polyalkylene ether resin (C), and crosslinkable fine particles containing a repeating unit derived from an acrylic acid monomer and / or a repeating unit derived from a methacrylic acid monomer D) containing
The (meth) acrylic resin (A)
(1) not having a repeating unit derived from a monomer having a sulfo group and a repeating unit derived from a monomer having an amide group,
(2) a weight average molecular weight of 20,000 to 2,000,000,
(3) The resin solid content acid value is 100 to 800 mgKOH / g,
The polyalkylene ether resin (C) has a weight average molecular weight of 5,000 to 500,000,
The crosslinkable fine particles (D) are 30 to 95% by mass of a monomer (a) represented by the following formula (I), 5 to 60% by mass of a monomer (b) having a polyoxyalkylene chain and a polymerizable double bond, And copolymerized with 0 to 50% by mass of another polymerizable monomer (c),

(In the formula, R ¹ represents hydrogen or a methyl group. R ² represents CH ₂ or C ₂ H _4. )
The content of the (meth) acrylic resin (A) in the hydrophilic treatment agent solid content is 15 to 30% by mass, the content of the polyvinyl alcohol (B) is 5 to 40% by mass, A hydrophilizing agent wherein the content of the polyalkylene ether resin (C) is 15 to 50% by mass and the content of the crosslinkable fine particles (D) is 30 to 65% by mass. Forming a conversion coating by contacting the chemical conversion treatment agent to the surface of the A aluminum substrate,
A method of forming a hydrophilic film by contacting the hydrophilizing agent according to claim 1 with the chemical conversion film obtained in the step.   A hydrophilic film formed on the surface of the metal substrate by the method for forming a hydrophilic film according to claim 2.   The hydrophilic film according to claim 3, having a thickness of 0.3 to 10 m.