JPH1030069A - Aqueous hydrophilicity imparting agent and production of pre-coated fin material for heat exchanger using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an aqueous hydrophilicity imparting agent especially excellent in lastly property of hydrophilicity and provide a method for producing a high quality pre-coated fin material capable of obtaining an excellent hydrophilicity and not generating a blocking even on winding the fin as a roll. SOLUTION: This aqueous hydrophilicity imparting agent consists of a colloidal silica having 5-100nm dispersed particle diameter, a water soluble polymer containing at least a carboxylic acid polymer and water in (30:70)-(70:30) weight ratio of the solid portions of the colloidal silica to the water soluble polymer by 4-20wt.% total content of them. Also, the content of the carboxylic acid group in the carboxylic acid polymer contained in the water soluble polymer is 20-63wt.%, and total pH value thereof is 1-5. The method for producing a pre-coated fin material is to apply the hydrophilicity imparting agent over the fin base material made from aluminum so as to attain 0.3-1.5g/m<2> adhered amount of the solid portion, and drying the applied agent by heating.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aqueous hydrophilicity-imparting agent suitable for imparting hydrophilicity to the surface of an aluminum material and a method for producing a precoated fin material for a heat exchanger using the agent. is there.

[0002]

2. Description of the Related Art Generally, in a heat exchanger such as an air conditioner used for a building or an automobile, an aluminum material (hereinafter referred to as aluminum or aluminum alloy) is formed into a predetermined fin shape. Fin material is used. In such a fin material, since the interval between the fins is narrowed due to the purpose of increasing the heat exchange efficiency and the effect of miniaturization of the air conditioning equipment, water condensed on the fin surface during cooling or the like becomes spherical. A phenomenon occurs in which a bridge is formed between the fins, and as a result, there is a problem that the ventilation resistance increases and the heat exchange capacity decreases.

[0003] For this reason, conventionally, a surface treatment for imparting hydrophilicity to the fin surface by applying a hydrophilicity imparting agent to the fin base material before fin processing is conventionally performed. This is to increase the hydrophilicity of the fin surface so that the water adhering to the fin surface spreads over the entire surface of the fin surface without agglomeration, thereby avoiding the above-mentioned bridging phenomenon. Note that a fin material in which such a hydrophilicity-imparting agent or the like is applied before use before forming is usually also referred to as a pre-coated fin material.

As such a hydrophilicity-imparting agent, for example, those containing silica and an organic polymer as main components are known (JP-A-53-92846, JP-A-5-92846).
JP-A-5-99976 and JP-A-6-221786.

[0005]

However, conventional hydrophilicity-imparting agents containing silica and an organic polymer as main components are:
Although the hydrophilicity is well exhibited in the initial stage, the hydrophilicity tends to gradually deteriorate over time due to repeated dry / wet conditions and adhesion of hydrocarbons in the air, etc. There is a demand for improvement.

[0006] Further, the hydrophilicity-imparting materials proposed in the above publications are all alkaline in view of the composition and the like, and the surface after being applied to the fin base material is relatively low as described later. It tends to be smooth. Then, not only the hydrophilicity persistence is insufficient on such a fin-coated surface, but another phenomenon that water is repelled is observed. In JP-A-6-221786, a mixed solution (alkali) of a silicate (sodium silicate), a water-soluble resin (sodium polyacrylate) and water is applied to an aluminum plate in Example 1. , Average particle size 0.5 μm
Although a pre-coated fin material that forms a hydrophilic film with silica particles is shown, the film itself to be formed becomes alkaline, which causes foaming and deterioration of the volatile press oil during fin processing and reduces the corrosion resistance of the fin material. In addition, there is a problem that the film structure changes with the passage of time due to the dissolution of alkali.

[0007] Further, the pre-coated fin material is usually stored in a roll before storage, and when the fin material is coated with a conventional hydrophilicity imparting agent, the fins adhere to each other. So-called blocking may occur.

[0008] The object of the present invention is to provide, for example, when applied to the surface of an aluminum material, not only excellent hydrophilicity can be obtained in the initial stage, but also aqueous hydrophilicity imparted continuously over a relatively long period of time. To provide an agent. Another object of the present invention is to provide a method for producing a precoated fin material for a heat exchanger, which can produce a high quality precoated fin material that does not cause blocking even when rolled, in addition to obtaining such excellent hydrophilicity. Is to provide.

[0009]

The aqueous hydrophilicity-imparting agent of the present invention is composed of colloidal silica having a dispersed particle diameter of 5 to 100 nm, a water-soluble polymer containing at least a carboxylic acid polymer, and water, The colloidal silica and the water-soluble polymer have a solid content weight ratio of 30: 70-7.
0:30, the total content is 4 to 20% by weight, the content of the carboxyl group in the carboxylic acid polymer contained in the water-soluble polymer is 20 to 63% by weight, and the total pH value is 1 -5.

Further, a method for producing a precoated fin material for a heat exchanger of the present invention comprises a composition comprising colloidal silica having a dispersed particle diameter of 5 to 100 nm, a water-soluble polymer containing at least a carboxylic acid polymer, and water; The colloidal silica and the water-soluble polymer have a solid content weight ratio of 3
0: 70-70: 30, the total content of which is 4-20% by weight, the content of carboxyl groups in the carboxylic acid polymer contained in the water-soluble polymer is 20-63% by weight, and An aqueous hydrophilicity-imparting agent having a pH value of 1 to 5 is coated on a surface of an aluminum fin substrate directly or via a corrosion-resistant undercoat formed on the surface of the aluminum fin base material with a solid content of 0.3 to 1.5 g / m ^2, and drying by heating.

The colloidal silica may be either an acid (pH 1 to 4) stable silica sol or an alkali (pH 9 to 10.5) stable silica sol provided as an aqueous dispersion. Is 5 to 100 nm,
Preferably, one having a thickness of 10 to 30 nm is used. When using alkali-stable colloidal silica, the colloidal silica is neutralized by the acid of the carboxylic acid, but in order to minimize aggregation of the silica in a bath having a pH value of 1 to 5, It is important to minimize the time for the alkali-stable colloidal silica to pass (reside) in the neutral range of pH 5 to 7 in the bath. If the dispersed particle diameter is less than 5 nm, the silica is likely to aggregate, and the required roughened surface cannot be obtained, and the hydrophilicity level is also low. On the other hand, if it exceeds 100 nm, the silicas will coalesce and the stability of the bath will deteriorate.

The water-soluble polymer contains a water-soluble carboxylic acid polymer and, if necessary, other polymer materials described later. In this water-soluble polymer, the content of carboxyl groups in the carboxylic acid polymer present in the polymer, that is, the weight ratio of carboxyl groups (COOH) to the total weight of the carboxylic acid polymer is 20 to 63% by weight. If the content is less than 20% by weight, the solubility in water becomes poor. On the other hand, the upper limit of the content (63% by weight) is the upper limit of the theoretical calculation value when the total amount is an acrylic acid polymer. Is not really possible. The content of the carboxyl group is measured by, for example, a chemical analysis method (for example, a reaction amount is calculated by neutralization titration and converted) in a liquid state before coating,
In the state of the film after the application, it is measured by an infrared spectroscopic analysis method.

The water-soluble carboxylic acid polymer functions as a pH adjuster when present as an imparting agent before application, and functions as a film-forming retention agent and a binder for colloidal silica particles when a film is formed by application. As the carboxylic acid polymer, an acrylic acid polymer such as a polyacrylic acid resin, a polymethacrylic acid resin, a polyacrylic acid copolymer, or an esterified product of polyacrylic acid is used alone or in combination. Incidentally, the pH value of the aqueous solution of the acrylic acid-based polymer alone (concentration: 20% by weight) is 1 to 3. The carboxylic acid polymer has an average molecular weight of 2,000.
0 to 500,000, preferably 15,000 to 10
It is good to be 0000. If the molecular weight is less than 2,000, the coating film is easily dissolved in water, and conversely,
If it exceeds 000, the viscosity as a coating material becomes abnormally high, so that it becomes difficult to dissolve in water, and the compatibility with other polymers becomes poor. Coating cannot be performed.

The polymer used in combination with the water-soluble polymer includes, for example, resins having an ether bond in the molecule (polyethylene glycol, polyether urethane,
Polyglycidyl ether compound).
When a resin having this ether bond is used, a coating film of an imparting agent with less thermal yellowing can be obtained.

The water-soluble polymer may be blended with a polymer material that functions as a crosslinking agent or a film-forming softener for insolubilizing the carboxylic acid polymer in water. Examples of the polymer to function as a crosslinking agent include diethylene glycol, glycerin, polyhydric alcohols such as pentaerythritol, a water-soluble epoxy resin, a water-soluble melamine resin,
A water-soluble urethane polymer such as isocyanate is used. In addition, as a polymer that functions as a film-forming softener, polyacrylamide, polyethylene glycol,
Polyvinyl alcohol, water-soluble polyester and the like are used. For these compounding amounts, the equivalent amount of the carboxylic acid is limited in the crosslinking agent, and the amount obtained by subtracting the total compounding amount of the carboxylic acid polymer and the crosslinking agent from the compounding amount of the water-soluble polymer in the film-forming softener is limited. .

The colloidal silica and the water-soluble polymer have a solid content weight ratio of 30:70 to 70:30, preferably 4:70.
It is blended so as to be 0:60 to 70:30. If the solid content weight ratio of the colloidal silica is less than 30, the concentration of the hydrophilic group in the total surface area of the coating film is insufficient, so that the amount of sustained hydrophilicity is reduced. When the amount of the compound is too small, the coating film becomes brittle.

The colloidal silica and the water-soluble polymer are blended so that the total content of the colloidal silica and the water-soluble polymer is 4 to 20% by weight. If the total compounding amount is less than 4% by weight, the desired level of hydrophilicity cannot be imparted and the uniformity of the coating film decreases, while if it exceeds 40% by weight, the viscosity of the liquid increases and the coating workability increases. Or the uniformity of the coating film decreases.

The water is not particularly limited, but deionized water, pure water and the like are used. Since this water corresponds to the remainder of the entire imparting agent excluding the colloidal silica and the water-soluble polymer, its content is 80 to 96% by weight including the optional components described below.

The pH value of the whole imparting agent is 1 to 5,
When H is less than 1, the bath stability of the imparting agent is poor, and it is not appropriate because the aluminum material surface or the corrosion-resistant underlying film may be dissolved at the time of coating film formation. When the pH exceeds 5, colloidal silica is spherical at the time of film formation. And does not precipitate on the surface layer. The pH value is adjusted by adjusting the amount of the carboxylic acid polymer, but may be adjusted by using a volatile acid such as nitric acid or acetic acid.

The imparting agent may include, if necessary, a water-soluble organic solvent, a leveling agent, an antifoaming agent, a surfactant, a preservative,
Optional components such as antibacterial agents and antifungal agents can be added,
In that case, it is added within a range where the total content does not exceed 30% by weight with respect to the entire imparting agent. The content of each optional component is in the range of 0.1 to 10% by weight based on the entire imparting agent. It is necessary not to add a polyvalent metal ion such as chromium ion into the bath of the imparting agent. When this chromium ion is added, the polymerization and curing of the acrylic acid polymer as a water-soluble polymer proceeds during storage in a bath, making it difficult to form an appropriate coating film.

The water-soluble organic solvent is added to dilute the water-soluble polymer, and specifically, alcohols such as methyl alcohol, ethyl alcohol, propyl alcohol, butyl alcohol, and ethylene glycol are used. . The leveling agent is added to reduce the surface tension of the imparting agent, and specifically, a silicon-based leveling agent such as polysiloxane and silicon oligomer, a fluorine-based leveling agent such as perfluoroalkyl, and a polyacrylate. And other acrylic leveling agents. Antifoaming agents are added to suppress foaming during the preparation and application of the imparting agent, and specifically include glycols such as polypropylene glycol, methanol, ethanol, isopropanol, n-butanol, and isobutanol. And lower fatty acids such as metal soaps and higher fatty acid metal soaps such as metal soaps. Surfactants are added to lower the surface tension of the imparting agent to improve applicability or to function as an initial hydrophilicity imparting agent in the coating film.Specifically, alkylbenzene sulfonate, alkyl Anionic surfactants such as sulfosuccinates and nonionic surfactants such as polyoxyethylene alkylamines and polyoxyethylene alkyl ethers are used. In addition, a cationic surfactant is not preferable from the bath stability of the imparting agent. Preservative,
Antibacterial agents, antifungal agents and the like are added to prevent the generation of mold odor due to corrosion odor and mold generation.
Imidazole-based compounds such as (4-thiazolyl) -benzimidazole, methyl 2-benzimidazole carbamate, and 2-dicarboximide o-phenylphenol are used. These preservatives, antibacterial agents, antifungal agents and the like are preferably added so that the total solid content is 5 to 20% by weight.

The imparting agent of the present invention is prepared as an aqueous composition (paint) by blending colloidal silica, a water-soluble polymer, water and, if necessary, optional components under the above-mentioned conditions. The imparting agent has a surface tension of 40 dyn or less and a viscosity of 5 to 100 cps (2
0 ° C). The imparting agent is used by being applied to aluminum or an alloy thereof, but may be applied to other metal materials for the purpose of, for example, preventing dew condensation.

In producing a precoated fin material for a heat exchanger using the imparting agent of the present invention, the imparting agent is applied directly to the surface of an aluminum fin substrate or on a corrosion-resistant undercoat formed on the surface. And then dried by heating. When the application material is directly applied, the surface of the fin base material is subjected to a degreasing treatment or the like. In addition, as a corrosion-resistant undercoat, chromate chromate treatment, phosphoric acid chromate treatment,
An inorganic film formed by a coating type chromate treatment or a corrosion-resistant resin film such as an acrylic resin or an epoxy resin is formed. In this case, the thickness of the inorganic film is preferably 0.01 to 0.2 μm, and the thickness of the corrosion-resistant resin film is preferably 0.5 to 3 μm.

The application of the imparting agent to the fin base material is performed by using a coating method such as a roll coating method, a bar coating method, a spraying method, a dipping method or the like so that the solid content becomes 0.3 to 1.5 g / m ² . Do so. When the amount of adhesion is less than 0.3 g / m ² , the hydrophilicity level of the coating film is low, and when unevenness in application occurs, the required hydrophilicity cannot be obtained partially. On the other hand, if it exceeds 1.5 g / m ² , there is no further improvement in the hydrophilicity level, and problems such as peeling of the coating film during the fin forming process occur.

The heating and drying after the coating is performed at a heating temperature of 200 to
Preferably, the heating is performed at 280 ° C. and a heating time of 5 to 60 seconds. If the heating temperature is lower than 200 ° C., the polymer component is uncured, and the coating film dissolves or wets when it comes in contact with water. The membrane becomes brittle. Also,
When the heating time exceeds 60 seconds, not only the improvement of the coating film performance is not seen, but also the production cost is increased. Therefore, the heating time is preferably 10 to 30 seconds.

The precoated fin material thus obtained is wound into a roll, if necessary, and stored. Then, volatile press oil is applied to the precoated fin material, followed by forming such as slitting and corrugating. A fin material for a heat exchanger having a desired shape is used. Then, the hydrophilic coating is exposed by heating the fin material to volatilize the volatile press oil from the surface.

The imparting agent of the present invention contains colloidal silica as a stable colloidal solution in the solution. During the coating and heating and drying, the water evaporates and the acidity increases (pH is 1 or less). When the coating is formed, the colloidal silica becomes spherical in an independent state, and the coating film surface becomes roughened. Also, the adhesion of the coating film is good.
This allows a high level of hydrophilicity to be obtained,
Moreover, this excellent hydrophilicity is maintained not only in the initial stage but also for a long period of time. The independent particle size of the spherical silica gel formed at the time of film formation is 0.1 to 2.5 μm, preferably 0.2 to 1.5 μm.

Further, in the precoated fin material for a heat exchanger to which this imparting agent is applied, granular silica gel is densely present on the surface of the coating film, and the coating film surface is in a roughened state.
Even if the fin material is rolled or overlapped, no blocking occurs. Further, the pre-coated fin material to which the imparting agent is applied has extremely good moldability in the post-process.

[0029]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in more detail with reference to examples. It goes without saying that the present invention is not limited to these examples.

Example 1 Aqueous solution of polyacrylic acid resin (trade name: Accumer 151)
0, manufactured by ROHM & HUS, solid content 25%, average molecular weight 6
000, carboxyl group content 62% by weight) 16
g and colloidal silica (trade name: Snowtex ST
-0, manufactured by Nissan Chemical Co., Ltd., solid content 20%, particle size 10
20 nm, pH 2-4) 20 g with a solid content weight ratio of 5
The mixture was mixed at 0:50, and deionized water was added to dilute the mixture to obtain a hydrophilicity-imparting agent, which was a composition bath prepared so as to have a total weight of 100 g. The pH of the resulting bath was 2.6. The application agent was applied to a degreased aluminum fin base material by a coater so that the solid content was 0.8 g / m ^2, and then heated and dried at 240 ° C. for 30 seconds to prepare a precoated fin material.

In order to know the coating properties of the obtained fin material,
The coating film was examined for initial hydrophilicity, hydrophilicity persistence, wet adhesion, and independent average particle size of the silica sol. Regarding the initial hydrophilicity, the spreading diameter (mm) of a water droplet when 10 μl (microliter) of deionized water was dropped on the surface of the coating film was measured.
φ) was measured. Regarding the hydrophilicity persistence, the fin material was immersed in running water for 7 hours, then left to dry at a temperature of 20 ° C. for 17 hours, and dried for 10 times. Diameter of spread (m
mφ) was measured. Regarding the wet adhesion, the fin material was immersed in running water for 100 hours, dried at room temperature, and then the peel length when the cross-cut cellophane tape was peeled was measured. Regarding the independent average particle size, actual dimensions were individually measured from an enlarged photograph of the coating film surface.

The results show that the initial hydrophilicity is 10 mmφ or more, the hydrophilicity persistence is 10 mmφ or more, and the wet adhesion is 100/1.
00, the independent particle size was 0.3 to 1.4 μm. Also,
The surface coverage of the particulate silica sol on the coating film was measured using a planimeter, and the coverage was 93%.
Further, when the life of the bath was examined, it was stable after 30 days had passed. Regarding the life of this bath, the same results were obtained in Examples 2 and 3 described later.

Example 2 A hydrophilicity-imparting agent was prepared under the same conditions as in Example 1 except that 0.3 g of glycerin was added to adjust the total weight to 100 g. The pH of the bath was 2.6. Then, this imparting agent was applied to a degreased aluminum fin substrate under the same conditions as in Example 1, and dried by heating to prepare a precoated fin material.

In the case of this example, the coating film properties were such that the initial hydrophilicity was 10 mmφ or more, and the hydrophilicity was 10 mmφ.
As described above, the wet adhesion was 100/100, and the independent particle size was 0.3.
１1.4 μm, and the surface coverage was 93%.

Example 3 The hydrophilicity-imparting agent of Example 1 was applied to a solid content of 0.6 g /
The coating was performed under the same conditions as in Example 1 except that the coating was performed so as to obtain m ² , followed by heating and drying to prepare a precoated fin material.

In the case of this example, the characteristics of the coating film were such that the initial hydrophilicity was 10 mmφ or more and the hydrophilicity was 10 mmφ.
As described above, the wet adhesion was 100/100 and the independent particle size was 0.2.
0.9 μm, and the surface coverage was 90%. In addition, a micrograph (FIG. 1) of the surface of the coating film magnified and taken at this time shows that the silica sol is surely formed in an independent granular form and densely. Therefore, it can be said that the surface of the coating film formed by the agent of the present invention has a structure composed of an aggregate of independent particles.

Example 4 Hydrophilicity was imparted under the same conditions as in Example 1 except that an amount corresponding to 7% by weight of 2 (4 thiazolyl) -benzimidazole was added to adjust the total weight to 100 g. I made a medicine. The pH of the bath was 2.6. Then, this imparting agent was applied to a degreased aluminum fin substrate under the same conditions as in Example 1, and dried by heating to prepare a precoated fin material.

Regarding the antibacterial and antifungal properties of the fin material, cut-out 3 × 3 cm square samples were incubated at 28 ° C. and 37 ° C. in a constant temperature base using bacterial agar medium and mold agar medium.
When stored at 48 ° C. for 48 hours and examined for growth status, neither bacteria nor mold was detected.

Example 5 The same polyacrylic acid resin aqueous solution as in Example 1 was used in an amount of 8 g.
Water-soluble epoxy resin (trade name: Denacol EX313,
A hydrophilicity-imparting agent was produced under the same conditions as in Example 1 except that 2 g of a solid content of 100%, epoxy equivalent 141) manufactured by Nagase Kasei Co., Ltd. was added. The pH of the bath was 2.8. Then, this imparting agent was applied to a degreased aluminum fin substrate under the same conditions as in Example 1, and dried by heating to prepare a precoated fin material.

The properties of the coating film in this embodiment are as follows: initial hydrophilicity: 10 mmφ, hydrophilicity retention: 10 mmφ, wet adhesion: 100/100, independent particle size: 0.1 to 0.2.
μm, and the surface coverage was 93%. After the fin material was kept in an atmosphere at 350 ° C. for 5 minutes, the degree of yellowing of the coating film surface was measured by a color difference meter, and the b value indicating the degree of yellowing was 8. Incidentally, when this yellowing degree measurement was also performed on the fin material of Example 1, the b value was 16
Met. As a result, it can be seen that the yellowing degree of the fin material of this embodiment is reduced to half and is improved as compared with the case of the first embodiment.

Comparative Example 1 A hydrophilicity-imparting agent was prepared under the same conditions as in Example 1 except that sodium hydroxide was added to adjust the pH of the bath to 9.0. Then, this imparting agent was applied to a degreased aluminum fin substrate under the same conditions as in Example 1, and dried by heating to prepare a precoated fin material.

In this case, the initial hydrophilicity was 9 mmφ, the hydrophilicity persistence was 5.5 mmφ (water was repelled), the wet adhesion was 100/100, the independent particle size was less than 0.01 μm, No independent particles were found on the surface. Bath life is 3
It was stable even after 0 days. Also, from a micrograph (FIG. 2) of the coating film surface at this time,
It can be seen that the surface is almost smooth.

Comparative Example 2 A hydrophilicity-imparting agent was prepared under the same conditions as in Example 1 except that the colloidal silica in Example 1 was used in an amount of 8 g and the weight ratio of the solid content to the polyacrylic acid polymer was set to 28:72. The pH value of this bath was 2.5. Then, the imparting agent is added to the degreased aluminum fin substrate with a solid content of 0.6
The coating was performed under the same conditions as in Example 1 except that the coating was performed so as to be g / m ^2, and the coating was heated and dried to produce a precoated fin material.

In this case, the initial hydrophilicity is 7 to 8 mmφ,
Hydrophilicity lasting 6mmφ, wet adhesion 100/100
Met. In addition, a micrograph (FIG. 3) of the coating film surface enlarged at this time (FIG. 3) shows that the silica sol is in an amorphous state in which the silica sols are connected to each other. Therefore, both the initial hydrophilicity and the hydrophilicity lasting power were inferior to those of Example 1.

Comparative Example 3 The same conditions as in Example 1 were used except that trivalent chromium ion was added in an amount of 0.7% by weight and fluorine ion in an amount of 0.1% by weight to adjust the total weight to 100 g. A hydrophilicity-imparting agent was prepared. The pH of this bath was 1.9. Then, this imparting agent was applied to the degreased aluminum fin base material in Example 1.
The precoated fin material was prepared by applying under the same conditions as above and drying by heating.

In this case, the initial hydrophilicity was 9 mmφ, the hydrophilicity persistence was 6 mmφ, the wet adhesion was 90/100, the independent particle size was less than 0.01, and no independent particles were found on the surface of the coating film. Was. The bath life became unstable within 5 days.

Comparative Example 4 Self-crosslinking acrylic emulsion (trade name: Julimer SEK-301, manufactured by Nippon Pure Chemical Industries, Ltd., solid content 40)
%, PH 8.5 to 9.5) and colloidal silica (trade name: Snowtex ST-20, manufactured by Nissan Chemical Industries, Ltd., solid content 20%, particle size 10 to 20 nm, pH 9.5)
To 10) were mixed at a solid content weight ratio of 50:50 to prepare a hydrophilicity-imparting agent under the same conditions as in Example 1 except that the total weight was adjusted to 100 g. P of this bath
H was 9.7. Then, this imparting agent was applied to a degreased aluminum fin substrate under the same conditions as in Example 1, and dried by heating to prepare a precoated fin material.

In this case, the initial hydrophilicity was 10 mmφ, the lasting hydrophilicity was 6 mmφ, and the wet adhesion was 100/100. The surface of the coating film was as smooth as that of Comparative Example 1.

[0049]

As described above, according to the hydrophilicity-imparting agent of the present invention, when the imparting agent is applied to, for example, the surface of an aluminum material, the colloidal silica is spheroidized on the surface of the coating film. Independently formed with a roughened surface of the coating and good adhesion of the coating, a high level of hydrophilicity can be obtained. Can be obtained over a long period of time.

Further, according to the production method of the present invention, in addition to obtaining the above-mentioned good hydrophilicity, a high-quality precoated fin material which does not cause blocking even when wound into a roll can be obtained. The precoated fin material has good press workability during molding.

[Brief description of the drawings]

FIG. 1 is a micrograph showing a structure of a coating film surface of a fin material according to Example 3.

FIG. 2 is a micrograph showing a structure of a coating film surface of a fin material according to Comparative Example 1.

FIG. 3 is a micrograph showing a structure of a coating film surface of a fin material according to Comparative Example 2.

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Reiko Takazawa 1-34-1 Kambara, Kambara-cho, Anbara-gun, Shizuoka Pref. Nippon Light Metal Co., Ltd. Group Technology Center

Claims (2)

[Claims] 1. A composition comprising: a colloidal silica having a dispersed particle diameter of 5 to 100 nm; a water-soluble polymer containing at least a carboxylic acid polymer; and water, wherein the colloidal silica and the water-soluble polymer have a solid content ratio by weight. 30:70 to 70:30, the total content of which is 4 to
20% by weight and the content of carboxyl groups in the carboxylic acid polymer contained in the water-soluble polymer is 20 to
An aqueous hydrophilicity-imparting agent characterized by being 63% by weight and having an overall pH value of 1 to 5. 2. A composition comprising colloidal silica having a dispersed particle size of 5 to 100 nm, a water-soluble polymer containing at least a carboxylic acid polymer, and water, wherein the colloidal silica and the water-soluble polymer have a solid content weight ratio of 30: 7
0 to 70:30, the total content is 4 to 20% by weight, the content of the carboxyl group in the carboxylic acid polymer contained in the water-soluble polymer is 20 to 63% by weight, and the whole pH value Is 1 to 5 and the solid content is 0.3 on the surface of the aluminum fin substrate directly or via the corrosion-resistant undercoat formed on the surface of the fin substrate.
A method for producing a pre-coated fin material for a heat exchanger, wherein the pre-coated fin material is applied so as to be 1.5 g / m ² and heated and dried.