JP2020105426A - Hydrophilization treatment agent, hydrophilic film formation method, and hydrophilic film - Google Patents

Abstract

To provide a hydrophilization treatment agent capable of forming a hydrophilic film that is excellent in adhesion between the hydrophilic film and a metal base material surface in a state in which water is attached thereto, and is excellent in hydrophilicity persistence and water discharge property not only at normal temperature but also at low temperature, a hydrophilic film formation method using the hydrophilization treatment agent, and a hydrophilic film formed by the hydrophilic film formation method.SOLUTION: A hydrophilization treatment agent contains a hydrophilic resin and crosslinkable fine particles, and contains a specific (meth)acrylic resin, polyvinyl alcohol and a polyalkylene ether resin having a specific molecular amount as the hydrophilic resin, in which blending of each of the components is within a specific range.SELECTED DRAWING: None

Description

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

Conventionally, there is known a technique of applying a hydrophilic treatment to the surface of a metal base material. For example, in a heat exchanger using aluminum, the fin surface is subjected to a hydrophilic treatment in order to prevent problems such as noise caused by condensed water adhering to the fin surface and contamination due to splashing of water droplets. ..

As the hydrophilic treatment agent used for the hydrophilic treatment, for example, a polymer composition for hydrophilic treatment containing a polymer such as polyacrylic acid polymer and a polymer such as polyethylene oxide that hydrogen bonds with the polymer is proposed. (See Patent Document 1).

According to the hydrophilic treatment agent described in Patent Document 1, a hydrophilic film with improved hydrophilic durability can be obtained. However, depending on the type of pollutant that adheres, deterioration may proceed, and the hydrophilicity may not be sufficient. Further, the adhesion (WET adhesion) between the hydrophilic film and the surface of the metal base material in a state where water is attached may be insufficient in some cases.

As another hydrophilizing agent, a hydrophilizing agent containing a salt of carboxymethylcellulose, N-methylolacrylamide, polyacrylic acid, and polyethylene oxide, and an aqueous polymer compound having a polyoxyalkylene chain, an aqueous resin, and A hydrophilic treatment agent containing N-methylol acrylamide has been proposed (see Patent Documents 2 and 3).

According to the hydrophilic treatment agents described in Patent Documents 2 and 3, a hydrophilic film with improved hydrophilic durability can be obtained. However, since these are blended with N-methylol acrylamide as a monomer, there are still cases where the hydrophilicity persistence when contaminants adhere is still insufficient.

As another hydrophilic treatment agent, a crosslinkable fine particle obtained by copolymerizing a monoethylenic monomer having a polyoxyalkylene chain, a (meth)acrylamide monoethylenic monomer, a crosslinkable unsaturated monomer, and another monomer Have been proposed (see Patent Documents 4 to 6).

The hydrophilic treatment agents described in Patent Documents 4 to 6 improve the hydrophilic sustainability by containing the crosslinkable fine particles. Further, by containing the specific crosslinkable fine particles, it is possible to enhance the hydrophilicity persistence after the contaminants are attached and also enhance the adhesion between the hydrophilic film and the metal substrate surface in the state where water is attached. Techniques have also been proposed (Patent Documents 7 and 8).

JP-A-6-322292 JP-A-6-322552 JP, 7-102189, A JP-A-8-120003 JP-A-2000-248225 JP 2002-302644 A JP, 2005-002151, A JP, 2014-000534, A

As described above, when the hydrophilic treatment agents described in Patent Documents 7 and 8 are used, the hydrophilic film formed on the surface of the metal substrate has excellent hydrophilic durability in the state where contaminants are attached, and water It also excels in the adhesion between the hydrophilic film and the surface of the metal substrate in the adhered state.

By the way, products made of a metal base material including a heat exchanger made of aluminum are required to be downsized. As the product becomes smaller, the distance between adjacent metal substrates may become shorter, and if the distance between the metal substrates becomes shorter, for example, in a heat exchanger, clogging due to water droplets easily occurs. Therefore, the surface of the metal base material is required to have a property (drainage property) in which contacted water can easily flow, in addition to the required properties such as hydrophilic durability and WET adhesion.

In particular, for example, heat exchangers using aluminum may be used even in outdoor units in cold regions, and when water drops freeze on the surface of a metal substrate in a low temperature environment, ventilation resistance increases significantly. Will be done. When the frozen water droplets are melted in order to reduce the ventilation resistance, excessive energy that is not directly related to heat exchange is required, resulting in high cost.

Further, the conventional hydrophilic treatment agents are not yet sufficiently satisfactory in terms of hydrophilicity sustainability at low temperatures, and further hydrophilicity sustainability is required when used in low temperature environments such as cold regions.

That is, the hydrophilic film formed on the surface of the metal substrate used in a low temperature environment such as a cold region has low temperature resistance, that is, drainage property at low temperature and hydrophilic continuity, in addition to hydrophilic continuity and WET adhesion. Was wanted.

The present invention was made in order to solve the above problems, the object is excellent in adhesion between the hydrophilic film and the metal substrate surface in the state where water is attached, not only at room temperature but also at low temperature To provide a hydrophilic treatment agent capable of forming a hydrophilic coating excellent in hydrophilic durability and drainage, a hydrophilic coating forming method using the hydrophilic treatment agent, and a hydrophilic coating formed by the hydrophilic coating forming method. It is in.

The present inventors contain a hydrophilic resin and crosslinkable fine particles, and as the hydrophilic resin, a specific (meth)acrylic resin, polyvinyl alcohol, and a polyalkylene ether resin having a specific molecular weight are contained, and The inventors have found that the above problems can be solved by using a hydrophilic treatment agent having a component in a specific range, and have completed the present invention. More specifically, the present invention provides the following.

（式中、Ｒ^１は、水素またはメチル基を表す。Ｒ^２は、ＣＨ_２またはＣ_２Ｈ_４を表す。）
前記親水化処理剤の全固形分における、前記（メタ）アクリル系樹脂（Ａ）の含有率が１０質量％以上２０質量％以下であり、前記ポリビニルアルコール（Ｂ）の含有率が１０質量％以上２０質量％以下であり、前記ポリアルキレンエーテル樹脂（Ｃ）の含有率が４０質量％以上５５質量％以下であり、前記架橋性微粒子（Ｄ）の含有率が２０質量％より大きく３０質量％未満である親水化処理剤である。 In order to solve the above problems, the present invention provides
A hydrophilic treatment agent for forming a hydrophilic film on the surface of a metal substrate,
(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, polyvinyl alcohol (B), polyalkylene ether resin (C), and crosslinkable fine particles ( D),
The (meth)acrylic resin (A) is
(1) Does not have a repeating unit derived from a monomer having a sulfo group and a repeating unit derived from a monomer having an amide group,
(2) the weight average molecular weight is 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 mass% of a monomer (a) represented by the following formula (I), 5 to 60 mass% of a monomer (b) having a polyoxyalkylene chain and a polymerizable double bond, And a copolymerization of 0 to 50 mass% of other 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) is 10% by mass or more and 20% by mass or less, and the content of the polyvinyl alcohol (B) is 10% by mass or more in the total solid content of the hydrophilic treatment agent. 20% by mass or less, the content of the polyalkylene ether resin (C) is 40% by mass or more and 55% by mass or less, and the content of the crosslinkable fine particles (D) is more than 20% by mass and less than 30% by mass. Which is a hydrophilic treatment agent.

In the hydrophilic treatment agent, the polyalkylene ether resin (C) may have a weight average molecular weight of 5,000 to 50,000.

Still another aspect of the present invention is the step of forming a chemical conversion film by contacting the surface of a metal substrate with a chemical conversion treatment agent, and the hydrophilization treatment according to claim 1 or 2 for the chemical conversion film. And a hydrophilic film forming step of forming a hydrophilic film by contacting the agent.

Still another aspect of the present invention is a hydrophilic film formed on the surface of the metal substrate by the hydrophilic film forming method.

The hydrophilic film may have a film thickness of 0.3 to 10 μm.

The hydrophilic film formed on the metal surface using the hydrophilic treatment agent of the present invention has excellent adhesion between the hydrophilic film and the surface of the metal substrate in a state where water is attached, and is hydrophilic not only at room temperature but also at low temperature. A hydrophilic film with excellent durability and drainage.

Hereinafter, embodiments of the present invention will be described. The present invention is not limited to the embodiments below.

<Metal substrate>
The metal base material on the surface of which the hydrophilic treatment is formed by the hydrophilic treatment agent according to the present invention is not particularly limited. For example, an aluminum base material made of aluminum can be used. Here, “aluminum” is a general term for metals and alloys mainly containing aluminum, and is a concept including pure aluminum and aluminum alloys.

The use of the aluminum base material is not particularly limited, and examples thereof include an aluminum heat exchanger. In the heat exchanger, a plurality of fins are arranged at a narrow interval in order to maximize the surface area of the heat exchanger from the viewpoint of improving heat exchange efficiency, and tubes for supplying a refrigerant are arranged intricately in these fins. Is often taken.

<Hydrophilic treatment agent>
The hydrophilic treatment agent according to the present invention contains a specific hydrophilic resin and specific crosslinkable fine particles in a specific ratio. The hydrophilic treatment agent of the present invention, by the blending of each component in a specific range, the hydrophilic film formed, with excellent adhesion between the hydrophilic film and the metal substrate surface in the state where water is attached, The hydrophilic film has excellent hydrophilic durability and drainage properties not only at room temperature but also at low temperature.

[Hydrophilic resin]
The hydrophilic resin in the present invention includes 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. The resin (C) is contained as an essential component.

((Meth)acrylic resin (A))
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 in the range of 50 to 100% by mass.

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

As the repeating unit derived from an acrylic acid monomer and the repeating unit derived from a methacrylic acid monomer, for example, as a monomer having one polymerizable unsaturated bond in the molecule, methyl methacrylate, n-butyl methacrylate, i-butyl methacrylate, Alkyl methacrylate such as 2-ethylhexyl methacrylate, isononyl methacrylate, n-octyl methacrylate, lauryl methacrylate, stearyl methacrylate, methyl acrylate, n-butyl acrylate, i-butyl acrylate, 2-ethylhexyl acrylate, isononyl acrylate, n-octyl acrylate And the like, aralkyl methacrylates such as benzyl methacrylate, aralkyl acrylates such as benzyl acrylate, alkoxyalkyl methacrylates such as butoxyethyl methacrylate, and alkoxyalkyl acrylates such as butoxyethyl acrylate. These may be used alone or in combination of two or more.

The (meth)acrylic resin (A) is a repeating unit derived from a monomer having a sulfo group as another component other than the repeating unit derived from an acrylic acid monomer and the repeating unit derived from a methacrylic acid monomer, and an amide. It does not contain a repeating unit derived from a monomer having a group. If these are included, it tends to be difficult to suppress the generation of odor.

The weight average molecular weight of the (meth)acrylic resin (A) is 20,000 to 2,000,000. When the weight average molecular weight of the (meth)acrylic resin (A) is less than 20,000, the adhesion between the hydrophilic film and the surface of the metal substrate when water is attached is deteriorated. When the weight average molecular weight of the (meth)acrylic resin (A) exceeds 2,000,000, the viscosity of the hydrophilic treatment agent becomes high, resulting in poor workability.

When 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 hydrophilic film is contacted with water has a hydrophilic film. Will move to the surface side of. Then, when the (meth)acrylic resin (A) moves to the surface side of the hydrophilic film, the adhesiveness between the hydrophilic film and the metal surface is reduced. Further, if the weight average molecular weight is too small, the adhesiveness between the hydrophilic film and the metal surface is lowered because it is eluted in water. When the weight average molecular weight of the (meth)acrylic resin (A) is within the above range, there is a problem that the adhesion between the hydrophilic film and the metal surface is deteriorated even if water remains on the surface of the hydrophilic film. Absent.

The more preferable range of the weight average molecular weight of the (meth)acrylic resin (A) is 20,000 to 100,000. More preferably, it is in the range of 20000 to 60000.

The value of the weight average molecular weight is the value measured by the gel permeation chromatography (GPC) method. Specifically, a solution prepared by dissolving 0.4 parts by weight of a resin sample in 100 parts by weight of tetrahydrofuran is used as a sample solution, and this is a LC-08 (A-5432) type GPC manufactured by Nippon Analytical Industry Co., Ltd. And calculated by polystyrene conversion.

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 adhesiveness between the hydrophilic film and the metal surface in the state where water adheres decreases. When the acid value of the (meth)acrylic resin (A) exceeds 800 mgKOH/g, the hydrophilic film adsorbs the acid component in the atmosphere, and the odor resistance decreases.

The solid content of the (meth)acrylic resin (A) in the total solid content of the hydrophilic treatment agent is 10% by mass or more and 20% by mass or less. It is preferably 10% by mass or more and 15% by mass or less.

When the solid content of the (meth)acrylic resin (A) is less than 10% by mass, the hydrophilic film formed has poor adhesion between the hydrophilic film and water on the surface of the metal substrate when water is attached. In addition, the drainage property at room temperature and low temperature is reduced. When the solid content of the (meth)acrylic resin (A) exceeds 20% by mass, the hydrophilic film formed has poor hydrophilic persistence and drainage properties at room temperature and low temperature. If the solid content of the (meth)acrylic resin (A) is within the above range, most of the (meth)acrylic resin (A) is allowed to exist at the boundary between the hydrophilic film and the metal substrate, and the hydrophilic film is formed. It is possible to prevent the (meth)acrylic resin (A) from existing on the surface side opposite to the metal substrate.

(Polyvinyl alcohol (B))
The polyvinyl alcohol (B) contained in the hydrophilic treatment agent can be obtained by saponifying a polymer obtained by polymerizing polyvinyl acetate. In the present invention, the degree of polymerization of polyvinyl alcohol (B) is not particularly limited, but is preferably 300 to 2000 or less. The saponification degree of polyvinyl alcohol (B) is preferably 95% or more.

The solid content of polyvinyl alcohol (B) in the total solid content of the hydrophilic treatment agent is 10% by mass or more and 20% by mass or less. It is preferably 10% by mass or more and 15% by mass or less.

When the solid content of the polyvinyl alcohol (B) is less than 10% by mass, the hydrophilic film formed may have poor hydrophilic persistence and drainage properties at room temperature and low temperature. When the solid content of the polyvinyl alcohol (B) exceeds 20% by mass, the hydrophilic film formed is less likely to exhibit hydrophilicity (initial hydrophilicity and hydrophilic sustainability) at room temperature, and drainage at room temperature and low temperature. Also drops.

(Polyalkylene ether resin (C))
The polyalkylene ether resin (C) contained in the hydrophilic treatment agent is a component that imparts hydrophilicity and lubricity to the hydrophilic film. By imparting lubricity to the hydrophilic film, workability at the time of pressing the surface of a metal base material such as an aluminum fin material is improved.

The polyalkylene ether resin (C) is not particularly limited as long as the polymerization average molecular weight is within the following range. For example, polyoxyethylene (polyethylene oxide, polyethylene glycol), polyoxypropylene, condensates thereof, and the like can be mentioned. In the present invention, these polyalkylene ether resins may be mixed and used. 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 weight average molecular weight of the polyalkylene ether resin (C) is 5,000 to 500,000. It is more preferably 5,000 to 300,000, and most preferably 5,000 to 50,000.

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, so that the hydrophilic film formed has a hydrophilic sustainability at room temperature and low temperature. Is reduced. 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 thus the coatability deteriorates. When the weight average molecular weight of the polyalkylene ether resin (C) decreases, the hydrophilicity of the polyalkylene ether resin (C) increases, so that the resulting hydrophilic film has higher hydrophilicity (initial hydrophilicity and hydrophilic continuity). Can be expressed.

The solid content of the polyalkylene ether resin (C) in the total solid content of the hydrophilic treatment agent is 40% by mass or more and 55% by mass or less. It is preferably 45% by mass or more and 55% by mass or less.

When the solid content of the polyalkylene ether resin (C) is less than 40% by mass, the hydrophilic film formed does not exhibit hydrophilicity. When the solid content of the polyalkylene ether resin (C) exceeds 55% by mass, components may be eluted from the formed hydrophilic film into water, and the stain removability may be deteriorated.

The hydrophilic treatment agent of the present invention increases the solid content of the polyalkylene ether resin (C) in the solid content of the hydrophilic treatment agent as described above. As a result, the polyvinyl alcohol (B), which serves as the basis of the hydrophilic film to be formed and enhances the adhesion to the surface of the metal substrate such as aluminum, and the polyalkylene ether resin (C) present on the surface of the hydrophilic film are closely matched. After separation, many irregularities are formed on the surface of the hydrophilic film. As a result, it is considered that the obtained hydrophilic film exhibits high hydrophilicity (initial hydrophilicity and hydrophilic sustainability).

In addition, when the solid content of the polyalkylene ether resin (C) is increased, the adhesiveness between the hydrophilic film and the metal surface tends to decrease. However, in the hydrophilic treatment agent of the present invention, by setting the solid content of the (meth)acrylic resin (A) existing near the boundary with the surface of the metal substrate within the above range, the hydrophilic film and the metal surface are It is possible to improve the adhesion.

[Crosslinkable fine particles (D)]
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 made of a copolymer obtained by copolymerizing c).

(Monomer (a) represented by the above formula (I))
The crosslinkable fine particles (D) used in the present invention include a methylol group and an ethylol group of the monomer (a) represented by the above formula (I) and a monomer (b) having a polyoxyalkylene chain and a polymerizable double bond. Monomers represented by the above formula (I), such as reaction with functional groups such as carboxyl group and hydroxyl group, condensation reaction between the methylol groups and ethylol groups of the monomer (a) represented by the above formula (I) It reacts with the methylol group and ethylol group of (a) and the carboxyl group and hydroxyl group contained in the other polymerizable monomer (c).

Therefore, when the crosslinkable fine particles (D) are used as a component of the hydrophilic treatment 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 have a relatively large amount of unreacted functional groups, when used as a component of the hydrophilic treatment agent, they react with the hydrophilic resin contained in the hydrophilic treatment agent. In addition, it is possible to greatly improve the hydrophilicity persistence after the contaminants are attached, without impairing the hydrophilicity. Further, since the crosslinkable fine particles (D) have a relatively small swelling ratio in water, it is possible to prevent the formed hydrophilic film from being dissolved in water.

Examples of the monomer (a) represented by the above formula (I) include N-methylol acrylamide, N-methylol methacrylamide, N-hydroxyethyl acrylamide, and N-hydroxyethyl methacrylamide. The hydrophilic treatment agent containing the crosslinkable fine particles (D) obtained by using the monomer (a) represented by the formula (I) has a hydrophilic continuity at room temperature and a low temperature, and a state in which water is attached. It is possible to form a hydrophilic film having excellent adhesion between the hydrophilic film and the surface of the metal substrate. These monomers (a) represented by the above formula (I) 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 mass% of the monomer (a) represented by the formula (I) with respect to 100 mass% of the monomer component. The monomer (a) represented by the formula (I) is preferably 40 to 80% by mass.

When the amount of the monomer (a) represented by the above formula (I) is less than 30% by mass, the hydrophilic film formed may have reduced hydrophilic persistence after contaminants are attached. When the amount of the monomer (a) represented by the above formula (I) exceeds 95% by mass, production may be difficult.

When the monomer (a) represented by the above formula (I) is in the above range, the monomer (a) represented by the above formula (I) functions as a crosslinking component and forms a hydrophilic film in the hydrophilic treatment agent. It also functions as the main component of the component. That is, in order to exert only the function as a crosslinking component, it is usually used in a smaller amount than the above range, but in the crosslinkable fine particles (D) used in the present invention, the monomer (a) represented by the above formula (I) is used. By setting the above range within the above range, the methylol group and the ethylol group remain in the crosslinkable fine particles (D) even after the copolymerization. For this reason, when a hydrophilic film is formed by using the hydrophilic treatment agent containing the crosslinkable fine particles (D), it reacts with other hydrophilic resin contained in the hydrophilic treatment agent to give strong adhesion and hydrophilicity. Persistence can be expressed. As a result, the hydrophilicity of the hydrophilic film is sufficiently maintained even after adhesion of a lubricant for plastics such as palmitic acid, stearic acid, paraffinic acid, and a contaminant such as diisooctyl phthalate to the formed hydrophilic film. be able to.

Further, the crosslinkable fine particles (D) have a high degree of crosslinking due to the increase in the content of the monomer (a) represented by the above formula (I). Therefore, the hydrophilic film formed of the hydrophilic treatment agent containing the crosslinkable fine particles (D) is prevented from being dissolved by water, and the hydrophilic film and the surface of the metal substrate are adhered to each other in the state where water is attached. A film having excellent properties can be formed.

(Monomer (b) Having Polyoxyalkylene Chain and Polymerizable Double Bond)
The monomer (b) having a polyoxyalkylene chain and a polymerizable double bond is not particularly limited as long as it is a monomer having a polyoxyalkylene chain and a polymerizable double bond, but the following formula (II) and/or the following formula (II) It is preferably a compound represented by III). This makes it possible to obtain crosslinkable fine particles (D) which are stable in water dispersion and have excellent hydrophilicity.

In the above formula (II), R ³ and R ⁴ are the same or different and are hydrogen or a methyl group. R ⁵ is 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, the dispersion stability and hydrophilicity are insufficient, and when it exceeds 300, the production becomes difficult. n is preferably an integer of 30 to 200.

In the above formula (III), R ⁶ and R ⁸ are the same or different and are hydrogen or a methyl group. R ⁹ is hydrogen, a methyl group, SO ₃ H, SO ₃ Na, or SO ₃ NH ₄ . The above R ⁷ is 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, the dispersion stability and hydrophilicity are insufficient, and when it exceeds 300, the production becomes difficult. m is preferably an integer of 30 to 200.

Examples of the monomer (b) having a polyoxyalkylene chain and a polymerizable double bond include, in addition to the compounds represented by the above formulas (II) and (III), for example, methoxy polyethylene glycol monomethacrylate, methoxy polyethylene glycol mono. Acrylate, octoxy polyethylene glycol-polypropylene glycol monoacrylate, etc. can also be mentioned. These may be used alone or in combination of two or more.

The monomer (b) having a polyoxyalkylene chain and a polymerizable double bond 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, in 100% by mass of the solid content of the monomer (b) having a polyoxyalkylene chain and a polymerizable double bond, the total mass of the solid part of the polyoxyalkylene chain is 50% by mass. It means that the content is at least mass %. If it is less than 50% by mass, the hydrophilicity of the hydrophilic film may decrease. The monomer (b) having a polyoxyalkylene chain and a polymerizable double bond more preferably contains the polyoxyalkylene chain in an amount of 80 to 99% by mass.

The crosslinkable fine particles (D) are obtained by copolymerizing a monomer component containing 5 to 60 mass% of the monomer (b) having a polyoxyalkylene chain and a polymerizable double bond with 100 mass% of the monomer component. To be The amount of the monomer (b) having a polyoxyalkylene chain and a polymerizable double bond is preferably 10 to 40% by mass.

When the amount of the monomer (b) having a polyoxyalkylene chain and a polymerizable double bond is less than 5% by mass, the dispersibility of the crosslinkable fine particles in the hydrophilic treatment agent is lowered and the hydrophilicity of the hydrophilic film is reduced. descend. If it exceeds 60% by mass, the adhesion of the hydrophilic film will be insufficient, and the hydrophilicity persistence after contaminants will adhere will be reduced.

(Other polymerizable monomers (c))
The other polymerizable monomer (c) has a polymerizable unsaturated bond in one molecule, a monomer (a) represented by the above formula (I), a polyoxyalkylene chain and a polymerizable double bond. The compound is not particularly limited as long as it is a compound that can be copolymerized with the monomer (b). For example, acrylic acid, methacrylic acid, itaconic acid, maleic acid, vinyl acetate and other vinyl monomers, 2-hydroxyethyl acrylate, hydroxypropyl acrylate, N-vinylacetamide, N-vinylformamide, N-vinylpyrrolidone, N -Vinylimidazole, acrylonitrile, methyl acrylate, methyl methacrylate, styrene, surfactant containing unsaturated double bond, acrylamide, methacrylamide, N-methylacrylamide, N-vinylsulfonic acid, N-allylsulfonic acid, styrenesulfonic acid Examples thereof include soda and 2-acrylamido-2-methylpropanesulfonic acid. Further, unsaturated monomers such as methyl acrylate, acrylic acid ester other than methyl methacrylate, and methacrylic acid ester, which are commonly used in radical polymerization, can be used. Of these, acrylic acid and methacrylic acid are preferable from the viewpoint that the hydrophilicity of the crosslinkable fine particles (D) can be improved. 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 0 to 50 mass% of another polymerizable monomer (c) with respect to 100 mass% of the monomer component. The other polymerizable monomer (c) is preferably 0 to 30% by mass.

When the amount of the other polymerizable monomer (c) exceeds 50% by mass, the hydrophilicity and crosslinkability of the resulting crosslinkable fine particles (D) are deteriorated, and the hydrophilic persistence of the hydrophilic film after adhesion of contaminants is reduced. descend.

(Water swelling rate)
The crosslinkable fine particles (D) used in the present invention preferably have a water swelling ratio of 1.0 to 1.5. As a result, when a hydrophilic film is formed from the hydrophilic treatment agent containing the crosslinkable fine particles (D), the adhesion between the hydrophilic film and the metal surface is reduced even if the hydrophilic film is exposed to water. Can be suppressed. The water swelling rate is more preferably 1.0 to 1.3.

The water swelling ratio of 1.5 or less has a monomer (a) represented by the above formula (I), a monomer (b) having a polyoxyalkylene chain and a polymerizable double bond, and another polymerizable monomer (c). Can be obtained by setting the above-mentioned mixing ratio and appropriately setting the reaction conditions.

In addition, the water swelling ratio in this specification is a value calculated as water swelling ratio=particle diameter in aqueous solution (D ₅₀ )/particle diameter in solvent (D ₅₀ ). The particle diameter (D ₅₀ ) is a value measured using an electrophoretic light scattering photometer, physical ELS-800 (manufactured by Otsuka Electronics Co., Ltd.).

(Volume average particle diameter)
The volume average particle diameter of the crosslinkable fine particles (D) is not particularly limited, but from the viewpoint of stability of the crosslinkable fine particles, it is generally 0.03 to 1 μm, preferably 0.05 to 0.6 μm. It is within.

(Mixing ratio)
Since the hydrophilic treatment agent of the present invention contains the crosslinkable fine particles (D) and the hydrophilic resin, the hydrophilic treatment agent has excellent adhesion between the hydrophilic film and the metal substrate surface in the state where water is attached, and is only at room temperature. It is possible to form a hydrophilic film excellent in durability and drainage even at low temperatures. The hydrophilic treatment agent of the present invention can form a hydrophilic film exhibiting a particularly excellent effect when used on a metal substrate, particularly aluminum or its alloy substrate.

The content of the crosslinkable fine particles (D) in the total solid content of the hydrophilic treatment agent is more than 20% by mass and less than 30% by mass. When the content of the crosslinkable fine particles (D) is 20% by mass or less, the hydrophilic film formed has poor hydrophilic persistence and drainage properties at room temperature and low temperature. On the other hand, when the content of the crosslinkable fine particles (D) is 30% by mass or more, the hydrophilicity of the formed hydrophilic film at low temperature decreases.

In the present invention, the content of the crosslinkable fine particles (D) in the solid content of the hydrophilic treatment agent is set within a specific range as described above. As a result, the polyvinyl alcohol (B) that enhances the adhesion to the surface of the metal substrate such as aluminum and the polyalkylene ether resin (C) that is present on the surface of the hydrophilic film are closely phase-separated to form a hydrophilic layer. The crosslinkable fine particles (D) enter the concaves and convexes on the surface of the coating. It is considered that the crosslinkable fine particles (D) enter the concaves and convexes on the surface of the hydrophilic film to flatten the surface of the hydrophilic film and improve the drainage property of the hydrophilic film.

(Method for producing crosslinkable fine particles (D))
The method for producing the crosslinkable fine particles (D) of the present invention is not particularly limited, but for example, 30 to 95% by mass of the monomer (a) represented by the above formula (I), a polyoxyalkylene chain and polymerization. 5 to 60% by mass of the monomer (b) having a polymerizable double bond and 0 to 50% by mass of the other polymerizable monomer (c) are produced in the absence of the dispersion stabilizer, although the monomer used is dissolved. The copolymer can be produced by polymerizing in a water-miscible organic solvent or a water-miscible organic solvent/water mixed solvent which is substantially insoluble.

A dispersant may be used in combination during the polymerization of the crosslinkable fine particles (D). Examples of the dispersant include dispersants such as polyvinylpyrrolidone, polyvinyl alcohol, and polycarboxylic acid, and various anionic, cationic, and nonionic surfactants.

In the production of the crosslinkable fine particles (D), the monomer (a) represented by the above formula (I), the monomer (b) having a polyoxyalkylene chain and a polymerizable double bond, and the other polymerizable monomer (c). The copolymerization of the monomer component containing a can be carried out in an ether solvent such as an alkylene glycol monoalkyl ether (eg, ethylene glycol monobutyl ether), a solvent such as methoxypropanol, a mixed solvent of these and water, and the like.

In the production of the crosslinkable fine particles (D), the copolymerization of the monomer components is usually performed in the presence of a radical polymerization initiator. The radical polymerization initiator is not particularly limited, and any of those commonly used 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 Butyrate, azo compounds such as 4,4′-azobis(4-cyanopentanoic acid), 2,2′-azobis(2-amidinopropane)dihydrochloride, 2,2′-azobis(NN′-) Amidine compounds such as dimethylene isobutylamidine) and 2,2′-azobis(NN′-dimethyleneisobutylamidine)dihydrochloride, persulfide initiators such as potassium persulfate and ammonium persulfate, or thiosulfate Examples thereof include a system in which sodium, amine and the like are used in combination. These may be used alone or in combination of two or more. The amount used can usually be within the range of 0.2 to 5 mass% with respect to the total amount of the monomers.

The polymerization temperature in the copolymerization of the monomer components can be selected depending on the kind of the polymerization initiator used and the like, but it is usually suitable to set it in the range of 70 to 140°C. If it is lower than 70°C, the crosslinkability becomes insufficient, and if it exceeds 140°C, it is difficult to control the reaction. The polymerization temperature is more preferably in the range of 90 to 120°C. When the polymerization temperature is 90° C. or higher, intraparticle crosslinking can be promoted. When the polymerization temperature is lower than 70° C., usually, the intra-particle crosslinking reaction hardly progresses during the polymerization. Therefore, after the polymerization reaction, the produced polymer is heated at a temperature of 90° C. or higher for 0.2 to 5 hours, It is preferable to carry out an operation for promoting intra-particle crosslinking.

The reaction time in the copolymerization of the monomer components is usually 0.2 to 5 hours. If it is less than 0.2 hours, the crosslinkability becomes insufficient, and if it exceeds 5 hours, the reaction does not change, which is economically disadvantageous.

A crosslinking reaction catalyst may be added to the polymerization reaction system, if necessary, for the purpose of promoting the intraparticle crosslinking reaction of the polymer particles during or after the polymerization reaction more quickly. Examples of the cross-linking reaction catalyst include strong acid catalysts such as dodecylbenzene sulfonic acid and paratoluene sulfonic acid, and polymerizable double bond-containing strong acid catalysts such as sulfoethyl methacrylate.

[Other ingredients]
A pigment may be added to the hydrophilic treatment agent of the present invention 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.

Further, the hydrophilic treatment agent of the present invention may optionally contain other components in required amounts according to the function to be added. Other components include, for example, surfactants, colloidal silica, titanium oxide, hydrophilic additives such as sugars, tannic acid, imidazoles, triazines, triazoles, guanines, hydrazines, phenolic resins, zirconium compounds, silanes. Anticorrosive additives such as coupling agents, melamine resins, epoxy resins, blocked isocyanates, amines, phenolic resins, crosslinking agents such as silica, aluminum, zirconium, antibacterial agents, dispersants, lubricants, deodorants, solvents, etc. Can be mentioned.

<Method for forming hydrophilic film>
The hydrophilic film forming method of the present invention includes a chemical conversion film forming step, a hydrophilic film forming step, and an essential step. By using the method for forming a hydrophilic film according to the present invention, it is excellent in the adhesion between the hydrophilic film and the surface of the metal base material in the state where water is attached, and is excellent in the hydrophilic durability and drainage property not only at room temperature but also at low temperature. A hydrophilic film can be formed. In particular, the hydrophilic film forming method according to the present invention is a method that can be suitably applied to aluminum or its alloy. The above effects are exhibited by using the specific hydrophilic treatment agent of the present invention described above. Therefore, a general method can be adopted as the method for forming the hydrophilic film.

[Degreasing process]
The hydrophilic film forming method of the present invention includes a chemical conversion film forming step, a hydrophilic film forming step, and an essential step, but prior to the chemical conversion film forming step, a degreasing treatment step of degreasing the surface of the metal base material is performed. You may. The degreasing treatment performed in the degreasing treatment step may be any of alkali degreasing with an alkaline solution of sodium hydroxide, sodium carbonate, sodium silicate, sodium phosphate or the like.
[Chemical conversion film formation process]
The chemical conversion film forming step of the present invention is a step of forming a chemical conversion film by bringing a chemical conversion treatment agent into contact with the surface of the metal base material. The chemical conversion treatment carried out in the chemical conversion film forming step is not particularly limited, and examples thereof include phosphoric acid chromate treatment, coating type chromate treatment, non-chromate treatment and the like.

When the phosphoric acid chromate treatment is carried out in the chemical conversion film formation step, it 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 immersion in the treatment liquid, spraying the treatment liquid, or the like. Examples of the corrosion-resistant resin primer used include acrylic, epoxy, polyester, phenol or urethane resin primer treatment.

The chemical conversion film obtained by the phosphoric acid chromate treatment preferably has a chromium (Cr) content 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 base material 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 for about 10 to 30 seconds.

When the coating type chromate treatment is carried out in the chemical conversion film forming step, the treating agent used is a chromate treating agent using a coating treatment such as a roll coater. When the coating type chromate treatment is performed, the amount of chromium in the chemical conversion film is preferably 5 to 30 mg/m ² .

When a non-chromate treatment is carried out in the chemical conversion film forming step, the treating agent used is a chromium-free treating agent, 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 Zr amount in the chemical conversion film obtained with the zirconium-based treatment agent is preferably 0.1 to 40 mg/m ² . If it is less than 0.1 mg/m ² , corrosion resistance is insufficient, and if it exceeds 40 mg/m ² , it becomes uneconomical. When the zirconium-based treatment is superposed on the chromate treatment in the chemical conversion film forming step, the effect is further enhanced.

[Corrosion resistance surface treatment process]
In many cases, the surface of a metal substrate such as an aluminum substrate is required to have both hydrophilicity and corrosion resistance, but in general, the more hydrophilic the film, the lower the corrosion resistance. Therefore, in the hydrophilic film forming method of the present invention, after performing the chemical conversion film forming step, before forming the hydrophilic film by the hydrophilic film forming step, for the purpose of forming a corrosion resistant film on the base, a corrosion-resistant surface treatment step It may be carried out. In the corrosion resistant surface treatment step, the chemical conversion film formed in the chemical conversion film forming step is subjected to a primer treatment with an organic resin to form a corrosion resistant surface.

[Hydrophilic film formation process]
The step of forming a hydrophilic film, and the step of forming a hydrophilic film by bringing the above-mentioned hydrophilic treatment agent of the present invention into contact with a chemical conversion film that has been optionally subjected to corrosion-resistant surface treatment.

The method of applying the hydrophilic treatment agent of the present invention is not particularly limited, and examples thereof include a roll coating method, a bar coating method, a dipping method, a spray method, and a brush coating method.

After applying the hydrophilic treatment agent, it is preferable to perform drying at a temperature of 120 to 300° C. for 3 seconds to 60 minutes and baking. If the baking temperature is lower than 120° C., sufficient film forming property cannot be obtained, and the hydrophilic film may be dissolved after immersion in water. If the temperature exceeds 300°C, the resin may decompose and the hydrophilicity of the hydrophilic film may be impaired.

<Hydrophilic film>
The hydrophilic film formed by the method for forming a hydrophilic film of the present invention is a hydrophilic film formed on the surface of a metal, particularly aluminum and its alloy, and the adhesion between the hydrophilic film and the surface of the metal substrate in the state where water is attached. It is a hydrophilic film that is excellent not only in water resistance but also in water retention and drainage at room temperature as well as at room temperature.

The film thickness of the hydrophilic film is preferably 0.3 to 10 μm. If the film thickness of the hydrophilic film is less than 0.3 μm, the hydrophilicity and the hydrophilic sustainability tend to decrease. If the film thickness of the hydrophilic film is less than 10 μm, the drainage tends to decrease.

Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to these examples.

<Material>
The materials used in Examples and Comparative Examples are shown below.
-PAA: polyacrylic acid (weight average molecular weight: 20000, acid value 780 mgKOH/g)
PVA: polyvinyl alcohol (weight average molecular weight: 20000, saponification degree: 98.5)
-PEO: polyethylene oxide (weight average molecular weight: 500000)
-PEG-1: polyethylene glycol (weight average molecular weight: 20000)
-PEG-2: polyethylene glycol (weight average molecular weight: 1000)
PEO-PPO: polyoxyethylene-polyoxypropylene condensate (weight average molecular weight: 15500)
-Resin particles: crosslinkable fine particles (manufacturing method will be described later)

[Method for producing crosslinkable fine particles]
A monomer solution prepared by dissolving 200 parts by mass of methoxypropanol, 60 parts by mass of N-methylolacrylamide, 20 parts by mass of methoxypolyethylene glycol monomethacrylate (polyethylene chain of 100 repeating units), 10 parts by mass of acrylic acid, and 10 parts by mass of acrylamide. And a solution prepared by dissolving 1 part by mass of "ACVA" (manufactured by Otsuka Chemical Co., Ltd., azo-based initiator) in 50 parts by mass of methoxypropanol, each through a separate port at 105°C under a nitrogen atmosphere and 150 parts by mass of methoxypropanol Was added dropwise to 3 parts over 3 hours, and the mixture was heated with stirring for 1 hour for polymerization.

In the obtained dispersion liquid, 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 the viscosity Ford cup was No. No. 4 for 18 seconds and the solid content concentration was 20% by mass.

<Examples 1 to 7, Comparative Examples 1 to 7>
[Preparation of hydrophilic treatment agent]
The components shown in Table 1 and Table 2 were mixed in the proportions shown in Table 1 and Table 2 to prepare hydrophilic treatment agents used in Examples and Comparative Examples. In addition, the number in the table is the solid content rate (unit: mass %) in the solid content of the hydrophilic treatment agent.

[Preparation of test plate]
(Degreasing process)
A 150 mm×200 mm×0.13 mm 1000 series aluminum material was prepared, and a degreasing treatment was performed at 70° C. for 5 seconds using a 1% solution of Surf Cleaner EC370 manufactured by Nippon Paint Co., Ltd.

(Chemical conversion film formation process)
Then, using a 10% solution of Alsurf 4130 manufactured by Nippon Paint Co., Ltd., phosphoric acid chromate treatment was carried out at 40° C. for 5 seconds to form a chemical conversion film.

(Hydrophilic film forming process)
Next, the hydrophilic treatment agent prepared above was adjusted to a solid content of 5%, and applied to the aluminum material having the chemical conversion coating obtained above with a bar coater #4, and heated at 220° C. for 20 seconds to be dried. Then, a test plate was prepared. The coating amount of the hydrophilic treatment agent was adjusted such that the film thickness of the hydrophilic film after drying was 1 μm.

<Evaluation>
The following evaluation was implemented about each obtained test board.

[Initial hydrophilicity]
The contact angle of the test plate with the water droplet was evaluated. The water contact angle was measured using an automatic contact angle meter (model number: DMo-701SA, manufactured by Kyowa Interface Science Co., Ltd.). The measured contact angle is the contact angle between the test plate and the water drop 30 seconds after the dropping in a room temperature environment. The evaluation results are shown in Tables 1 and 2. If the contact angle is less than 10°, the hydrophilicity is considered to be good.

[Hydrophilicity]
The test plate was immersed in pure water for 240 hours, pulled up, and dried. Then, the water contact angle with the water drop of the dried test plate was measured. The contact angle was measured using an automatic contact angle meter (model number: DMo-701SA, manufactured by Kyowa Interface Science Co., Ltd.). The measured contact angle is the contact angle between the test plate and the water drop 30 seconds after the 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 is good.

[WET adhesion]
Pure water was sprayed on the test plate, and the coating was rubbed with a finger so that a weight of about 500 g was applied. One reciprocation was once, and the number of times until the base material of the test plate was exposed was evaluated. The evaluation results are shown in Tables 1 and 2. Adhesion is considered to be good if the number of times until the base material of the test plate is exposed is 8 or more.

[Hydrophilicity persistence at low temperature]
The test plate was exposed to a constant temperature bath of −20° C. for 16 hours, subsequently immersed in running water for 7 hours, and then dried at 40° C. for 1 hour as one cycle. After 10 cycles, the test plate was dried. .. Then, the water contact angle with the water drop of the dried test plate was measured. The contact angle was measured using an automatic contact angle meter (model number: DMo-701SA, manufactured by Kyowa Interface Science Co., Ltd.). The measured contact angle is the contact angle between the test plate and the water drop 30 seconds after the dropping in a room temperature environment. The evaluation criteria are shown below.
◎: 20° or less ○: 20° or more, 30° or less △: 30° or more, 50° or less ×: 50° or more [Drainage property at low temperature]
The test plate was exposed to a constant temperature bath of −20° C. for 16 hours, subsequently immersed in running water for 7 hours, and then dried at 40° C. for 1 hour as one cycle. After 10 cycles, the test plate was dried. .. Subsequently, the falling angle of water droplets on the dried hydrophilic film was evaluated. Specifically, an automatic contact angle meter (model number: DMo-701SA, manufactured by Kyowa Interface Science Co., Ltd.) was used to measure the water falling angle between the hydrophilic film and the water droplet in the room temperature environment 30 seconds after the dropping. did. The evaluation criteria are shown below.
◎: 30° or less ◯: 30° or more, 50° or less △: 50° or more, 70° or less ×: more than 70°

The hydrophilic treatment agent according to the present invention has excellent adhesion between the hydrophilic film and the surface of the metal substrate in a state where water is attached, and has excellent hydrophilic persistence and drainage properties not only at room temperature but also at low temperature. A hydrophilic film can be formed. Therefore, the hydrophilic treatment agent according to the present invention can be preferably used particularly on the surface of a metal base material that serves as fins of a heat exchanger such as an air conditioner in a cold region.

Claims (5)

A hydrophilic treatment agent for forming a hydrophilic film on the surface of a metal substrate,
(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, polyvinyl alcohol (B), polyalkylene ether resin (C), and crosslinkable fine particles ( D),
The (meth)acrylic resin (A) is
(1) Does not have a repeating unit derived from a monomer having a sulfo group and a repeating unit derived from a monomer having an amide group,
(2) the weight average molecular weight is 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 mass% of a monomer (a) represented by the following formula (I), 5 to 60 mass% of a monomer (b) having a polyoxyalkylene chain and a polymerizable double bond, And a copolymerization of 0 to 50 mass% of other 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) is 10% by mass or more and 20% by mass or less, and the content of the polyvinyl alcohol (B) is 10% by mass or more in the total solid content of the hydrophilic treatment agent. 20% by mass or less, the content of the polyalkylene ether resin (C) is 40% by mass or more and 55% by mass or less, and the content of the crosslinkable fine particles (D) is more than 20% by mass and less than 30% by mass. Which is a hydrophilic treatment agent. The hydrophilic treatment agent according to claim 1, wherein the polyalkylene ether resin (C) has a weight average molecular weight of 5,000 to 50,000. A chemical conversion film forming step of forming a chemical conversion film by bringing a chemical conversion treatment agent into contact with the surface of the metal substrate;
A hydrophilic film forming method, comprising the step of bringing the hydrophilic treatment agent according to claim 1 or 2 into contact with the chemical conversion film to form a hydrophilic film. A hydrophilic film formed on the surface of the metal substrate by the hydrophilic film forming method according to claim 3. The hydrophilic film according to claim 4, wherein the hydrophilic film has a thickness of 0.3 to 10 µm.