JP3225793B2 - Highly hydrophilic paint - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a highly hydrophilic paint. More specifically, the present invention relates to a suitable highly hydrophilic paint which imparts a high degree of hydrophilic persistence and corrosion resistance to the aluminum fin surface of a heat exchanger for an air conditioner. More specifically, the present invention relates to a highly hydrophilic coating containing a specific shape of alumina sol.

[0002]

2. Description of the Related Art Conventionally, aluminum and its alloys have been widely used for heat exchangers of air conditioners because of their excellent workability and thermal conductivity. In the heat exchanger of the air conditioner, the condensed water generated during cooling turns into water droplets, forming a water bridge between the fins, increasing the ventilation resistance and deteriorating the heat exchange rate. Generally, processing is performed. On the other hand, in recent years, home appliances have been strongly required to be downsized, and air conditioners are no exception. In particular, heat exchangers that occupy a large volume among air conditioners are most strongly required to be downsized. The tendency of the fin shape to be complicated and the fin interval to be narrowed due to such demand imposes a further improvement in the hydrophilicity of the fin.

Methods for imparting hydrophilicity to aluminum fins include a chemical conversion treatment and a method of applying a hydrophilic paint. However, since the chemical conversion treatment is generally performed after fin processing such as drilling, there is a disadvantage that productivity is poor.

[0004] In order to solve this problem, there has been proposed a method of applying water glass or a hydrophilic paint before fin processing. Examples of such a hydrophilic paint include a paint made of an organic hydrophilic resin and a paint containing synthetic silica and the like. However, when an organic hydrophilic resin, for example, aqueous nylon, aqueous acrylic resin, polyvinyl alcohol, polyvinylpyrrolidone, or the like is used, the hydrophilicity is insufficient,
There was a problem that the balance between hydrophilicity and anticorrosiveness could not be achieved, or the effect of suppressing (preventing) odor was insufficient. On the other hand, when a coating containing synthetic silica or the like is used to impart hydrophilicity, the hydrophilicity and anticorrosion properties are superior to ordinary organic hydrophilic coatings, but the coating is hard, such as perforation. There have been problems such as severe wear of the molds and processing tools used for processing, shortening the life of the tools, and insufficient odor control (prevention) effects.

Further, when water glass is applied, there are disadvantages such as shortening of the service life of the tool or adsorption of odor as in the case of using a coating containing synthetic silica or the like.

[0006] In view of the above problems, there has been a demand for a paint which is excellent in hydrophilicity and anticorrosion properties and provides a relatively soft coating film which does not shorten the life of the tool.

On the other hand, as a hydrophilic paint containing no synthetic silica or the like, JP-A-5-22234 discloses poly (meth) acrylic acid and nitrates such as Al, Sn, Co, La, Ce and Ta. Japanese Patent Application Laid-Open No. 4-366182 discloses a hydrophilic coating film with polyvinylpyrrolidone and polyvinyl alcohol.

JP-A-3-252461 discloses a polyester urethane base coat coated with a hydrophilizing film using a carboxymethyl cellulose derivative and N-methylolacrylamide.
No. 3 discloses a hydrophilically-treated coating film using polyacrylamide, styrenesulfonic acid, and water-soluble urethane (used for both base coat and top coat).

However, these are insufficient in terms of hydrophilicity and are not practically used. Generally, aluminum fins are required to have sufficient hydrophilicity not only immediately after coating film formation, that is, at the initial stage, but also after various tests. The hydrophilicity persistence test assumes not only running water with condensed water and rainwater, but also a drying process at 50 ° C. with a heating medium during heating, with at least 8 cycles of immersion in running water and drying at 50 ° C. for 16 hours as one cycle. Although evaluation is necessary, the surface treatment method using each of the above coating films or treatment agents does not sufficiently satisfy the hydrophilicity.

In addition to the above, without containing synthetic silica or the like,
Alumina sol and those containing alumina are disclosed in
JP-A-134572, JP-A-58-76462, JP-A-59-205596, JP-A-59-2
29197, JP-A-60-164168,
JP-A-63-249643, JP-A-63-262
238, JP-A-63-262239, JP-A-2-22047, JP-A-5-70711, JP-A-6-172777, and the like.

Japanese Patent Application Laid-Open No. 57-134572 discloses a method of chemical conversion treatment of an aluminum material with an acid-based treatment liquid containing alumina sol or silica sol. It is thought that the use of alumina sol or silica sol was intended to increase the surface area and improve the wettability to water, but the hydrophilicity is insufficient because the alumina sol does not aggregate.

JP-A-58-76462 discloses an antifogging coating composition in which an alumina sol is combined with at least one selected from the group consisting of a specific carboxylate, sulfonate and phosphonate. ing. However, since this is intended for a synthetic resin film, a synthetic resin plate, and a glass plate, it has poor adhesion to an aluminum material. Also in the present invention, the hydrophilicity is insufficient because the alumina sol is not aggregated.

JP-A-59-205596 discloses a method in which a corrosion-resistant coating layer is provided on an aluminum plate, and a hydrophilic coating layer comprising silicic acid, silicate, silica sol, and alumina sol is formed on the surface of the corrosion-resistant coating layer. The disclosed aluminum fin material is disclosed. However, this hydrophilic coating layer is coated with a dispersion of silicic acid, silicate, silica sol, alumina sol on an aluminum plate as it is,
Since it is baked, when using silicic acid, silicate or silica sol, there is a problem that the life of the tool is shortened as described above because the coating film is hard, and when alumina sol is used. However, since it is used without aggregation, the contact angle with water is 30 to 35 degrees, which is insufficient in terms of hydrophilicity.

JP-A-59-229197 discloses a method for surface treatment of an aluminum heat exchanger in which a corrosion-resistant surface treatment film is formed on an aluminum plate, and then an aqueous suspension containing alumina fine particles is applied. It has been disclosed. However, a suspension aqueous solution containing alumina fine particles is insufficient in terms of hydrophilicity when used alone,
When used in combination with a polyethylene oxide thermoplastic polymer resin, although the hydrophilicity is somewhat improved as compared with a single system, an alumina sol that is not coagulated once cannot secure sufficient hydrophilicity.

JP-A-60-164168 discloses a heat exchanger having a coating layer formed of a glass frit containing polyamide-imide resin, Al ₂ O ₃ and calcium phosphate as main components. However, the heat exchanger in the present invention is not a heat exchanger of an air conditioner,
Therefore, the coating layer is not intended to improve the hydrophilicity and anticorrosion, but is intended to improve the heat resistance. Therefore, even if this coating composition is used for an aluminum fin heat exchanger of an air conditioner, the coating between the fins is not affected. Water bridge formation cannot be prevented. Also, the Al ₂ O shown here
Reference numeral ₃ denotes alumina, which forms a hard coating like synthetic silica, and is unsuitable for an aluminum fin heat exchanger of an air conditioner in order to shorten a tool life.

JP-A-63-249643 discloses that after forming a corrosion-resistant film on both sides of an aluminum plate, one of the corrosion-resistant films comprises a hydrophilic inorganic material and a low molecular organic compound having a carbonyl group on the surface. A first hydrophilic film is formed, and a second hydrophilic film comprising a water-soluble organic polymer compound or a water-soluble organic polymer compound and a low-molecular organic compound having a carbonyl group is formed on the surface of the other corrosion-resistant film. The disclosed fin material for a heat exchanger is disclosed. Alumina sol is mentioned as an example of the hydrophilic inorganic material forming the first hydrophilic film. However, alumina sol that is not once aggregated cannot secure sufficient hydrophilicity.

Further, since the first hydrophilic film uses a low molecular weight organic compound, the film forming performance is poor, and there is a problem that only a brittle film can be formed.

JP-A-63-262238 discloses that an organic or inorganic corrosion-resistant film is formed on a thin plate of aluminum or aluminum alloy, and water-soluble cellulose (or polyvinyl alcohol), alumina sol, melamine resin, urea A heat exchanger fin material in which a coating layer made of a resin or an amino resin such as a benzoguanamine resin is formed is disclosed. However, alumina sol that is not once aggregated cannot secure sufficient hydrophilicity.

JP-A-63-262239 discloses a heat exchanger fin in which a coating layer made of water-soluble cellulose (or polyvinyl alcohol), alumina sol and chromium compound is formed on a thin plate of aluminum or aluminum alloy. A material is disclosed. However, alumina sol that is not once aggregated cannot secure sufficient hydrophilicity.

JP-A-2-22047 discloses a heat exchange method in which a coating layer comprising a styrene-modified acryl-melamine resin, an epoxy resin and a styrene-methacrylic acid ester resin and activated alumina fine particles is formed. An instrument fin is disclosed. However, the fine particles shown here are alumina, which forms a hard coating like synthetic silica, causes significant damage to tools, and has insufficient hydrophilicity of the binder resin, so that it is unsuitable for aluminum fin heat exchangers of air conditioners. It is.

JP-A-5-70711 discloses an aluminum-containing metal containing a hydrophilizing component composed of an alkali silicate, colloidal silica, alumina sol, or a hydrophilic organic polymer material and a lubricating component composed of a siloxane compound. A hydrophilizing agent for a material is disclosed. However, alumina sol that is not once aggregated cannot provide sufficient hydrophilicity.

Japanese Patent Application Laid-Open No. 6-172777 discloses a lubrication method using a treatment liquid containing a siloxane compound on a hydrophilic film containing at least one of alkali silicate, colloidal silica, alumina sol and hydrophilic organic polymer material. A hydrophilic, lubricious aluminum-containing metal material having a coating formed thereon is disclosed. However, alumina sol that is not once aggregated cannot provide sufficient hydrophilicity.

In view of the various problems described above, as a result of repeated studies, it has been found that a non-silica-based or non-aqueous glass-based non-silica-based or non-aqueous glass-based material having a relatively soft coating film that is excellent in hydrophilicity and corrosion resistance and does not shorten the life of a tool. The present inventors have found a highly hydrophilic paint and have reached the present invention.

[0024]

That is, according to the present invention, the primary particles have a feather-like, rod-like, or dendritic-like shape and shape, and have an average particle size of 0.5 to 10 in a form in which they are aggregated in advance by a synthesis method. Alumina sol (a) which is 20 μm, and α having sulfonic acid or sodium sulfonate group,
10 to 80 parts of a β unsaturated monomer, 10 to 50 parts of an α, β unsaturated monomer having a carboxylic acid group, and 10 to 50 parts of an α, β unsaturated monomer having an alcoholic hydroxyl group. A water-soluble resin (b) obtained by copolymerizing a part of the high-hydrophilic resin (b).

Alumina sol (a) used in the present invention
Is a water-dispersed primary particle of alumina hydrate, having a colloidal size in which an anion in water is dispersed as a stabilizer, in a form in which the primary particles are aggregated in advance by a synthesis method, The average particle size of the aggregated particles is 0.5 to 20 μm
m. Specifically, "Cataloid AS-3" manufactured by Catalyst Chemicals, Inc. may be mentioned.

In the present invention, a relatively large alumina sol having a specific shape and form is preferably used. That is,
By having a feather-like, rod-like, or dendritic shape / morphology, the specific surface area is increased, and the primary particles of these alumina sols are in an aggregated form.
The wettability to water could be improved by capillary action. As a commercially available alumina sol having such a special shape and form, "Cataloid AS-3" manufactured by Catalyst Chemicals, Inc. is mentioned.

Also, "Cataloid AS" manufactured by Catalyst Chemicals, Inc.
-1 "," Cataloid AS-2 ", Nissan Chemical Industries, Ltd." Alumina Sol-100 "," Alumina Sol-20 "
0 "," Alumina sol-520 "," Alumina clear sol "manufactured by Kawaken Fine Chemical Co., Ltd.," Alumina sol-520 "
Alumina sol dispersed as primary particles having an average particle size of 2 to 100 nm, such as "10", and "Cataloid AS-3" in 90
A similar form can be obtained by mixing with a composition of parts / 10 parts to 0 parts / 100 parts and forming a paint.

Alumina sol (a) used in the present invention
Is in the middle of transition from amorphous gel to boehmite, and this state does not change in the agglomeration process and the normal baking conditions of the coil coat coating film (for example, 250 ° C. × 20 seconds). The alumina sol in the middle of the transition from the irregular gel to the boehmite is softer than the colloidal silica, and therefore, the blade of the press machine when processing the film containing this alumina sol has very little wear.

Alumina sol (a) used in the present invention
Has an average particle size of 0.5 to 20 μm. In the present invention, by using the alumina sol (a), the film thickness is reduced to 0.1.
It has succeeded in increasing the surface area of contact with water by roughening the surface of a hydrophilic coating film of 5 to 2 μm. Those having an average particle size of less than 0.5 μm are buried in the coating film, and those having an average particle size of more than 20 μm result in coating defects such as bumps, and none of them are suitable for use.

When the mixture of "Cataloid AS-3" and the alumina sol exemplified above is too large, it can be used after being classified by means such as centrifugation or filtration. Alternatively, it is also possible to adjust the particle size by pulverizing with a high-pressure homogenizer or the like after forming the coating.

Alumina sol (a) used in the present invention
Is desirably contained in an amount of 0.1 to 50 parts by weight based on 100 parts by weight of the solid content of the paint. If the amount is less than 0.1 part by weight, the hydrophilicity is insufficient, and if the amount is more than 50 parts by weight, the viscosity increases and the coatability deteriorates.

The water-soluble resin (b) used in the present invention includes 10 to 80 parts of an α, β unsaturated monomer having a sulfonic acid group or a sodium sulfonic acid group, and an α, β unsaturated monomer having a carboxylic acid group. It is obtained by copolymerizing 10 to 50 parts of a saturated monomer and 10 to 50 parts of an α, β unsaturated monomer having an alcoholic hydroxyl group. The water-soluble resin forms an essentially hydrophilic coating film on the substrate, and is blended to fix the alumina sol (a) in the coating film.

The α, β unsaturated monomer having a sulfonic acid group or a sodium sulfonic acid group exhibits anionic strong hydrophilicity and improves the wettability of the surface of the formed film with water.
For example, vinyl sulfonic acid, aryl sulfonic acid, 2-acrylamido-2-methyl sulfonic acid, styrene sulfonic acid, methacryloyloxyethyl sulfonic acid and their sodium, potassium, lithium salts and the like can be mentioned.

The α, β unsaturated monomer having a carboxylic acid group exhibits some hydrophilicity and adhesion to an aluminum substrate. For example, acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, crotonic acid and the like can be mentioned.

The α, β unsaturated monomer having an alcoholic hydroxyl group exhibits some hydrophilicity, and further causes crosslinking with the active hydroxyl group on the alumina sol particles, so that the whole water-soluble resin fixes the alumina sol particles. To act as a binder for the purpose. For example, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, N-methylol (meth) acrylamide and the like can be mentioned.

The water-soluble resin (b) is desirably contained in an amount of 30 to 99.9 parts by weight based on 100 parts by weight of the solid content of the paint. If the amount is less than 30 parts by weight, the content of the alumina sol (a) becomes relatively large, the viscosity increases, and the coatability deteriorates.
On the other hand, if it exceeds 99.9 parts by weight, the content of alumina sol (a) becomes relatively small, and the hydrophilicity becomes insufficient.

The paint of the present invention contains the above component (a),
In addition to (b), one or more of water-soluble resins or water-dispersible resins such as cellulose, polyurethane, polyester, polyether polyol, polyamide, and epoxy resin, and further, if necessary, Depending on the surfactant, hydrophilic organic or inorganic particles, antibacterial agent, lubricant,
You may mix | blend a coloring agent, a solvent, etc.

The highly hydrophilic paint of the present invention can be used not only as a precoat paint applied to aluminum fin materials, but also as a postcoat paint applied to processed fins.

[0039]

Next, the present invention will be described by way of examples.

Synthesis Example 1 220 g of deionized water was placed in a 500 cc three-necked flask.
Stir at 0 ° C. 0.4 g of ammonium persulfate was charged, and 160 g of a 50% aqueous solution of 2-acrylamido-2-methylpropanesulfonic acid (2AA2MPSA) and 2 g of 2% were added.
-A mixed solution of 10 g of hydroxyethyl acrylate (HEA) and 10 g of acrylic acid (AA) is added dropwise over 1 hour. Ammonium persulfate (0.4 g, 5% aqueous solution) was added four times every 50 minutes to complete the polymerization and obtain a water-soluble acrylic resin.

Synthesis Examples 2 to 6 (Water-soluble acrylic resin)
Synthesis Example 1) Aqueous polymerization was carried out in the same manner as in Synthesis Example 1 with the composition (weight ratio) shown in Table 1 to obtain a water-soluble acrylic resin.

[0042]

[Table 1]

Example 1 The particle size of Cataroid AS-3 manufactured by Catalyst Chemicals Co., Ltd. was measured with a Microtrac MK-II particle size analyzer manufactured by Nikkiso Co., Ltd., and the average particle size was 0.8 μm. . Synthesis Example 1
70 parts by weight of the water-soluble acrylic resin obtained in
30 parts of the aggregate was mixed with stirring and diluted with ion-exchanged water to prepare a hydrophilic paint having a nonvolatile content of 10%. Bar coat N is applied to an aluminum plate which has been treated with phosphoric acid chromate beforehand.
After coating according to O.6, it was baked for 20 seconds in a gas oven at 250 ° C. (wind speed 2 m / s) to obtain an aluminum coating material having a coating thickness of about 1 μm.

Examples 2 to 5 The same procedure as in Example 1 was carried out except that the type and the mixing ratio of the cataloid AS-3 and the other alumina sol were changed and the water-soluble acrylic resin of Synthesis Example 1 was used. Then, a hydrophilic coating material was prepared to obtain an aluminum coating material. Example 2 is 70 parts / 30 parts by weight of Cataloid AS-3 and Cataloid AS-1 manufactured by Catalysis Kasei Co., Ltd., and Example 3 is a mixture of Cataloid AS-3 and Alumina Sol-200 manufactured by Nissan Chemical Co., Ltd. In a dry weight ratio of 70 parts / 30 parts, Example 4
Is 50 parts / 50 parts by weight of Cataroid AS-3 and Alumina Sol-200 manufactured by Nissan Chemical Co., Ltd., and Example 5 is a dry weight ratio of Cataroid AS-3 to Alumina Sol-10 manufactured by Kawaken Fine Chemicals Co., Ltd. 70 parts / 30 parts.

The average particle size of each of the alumina sol mixture particles in the coating material after coating was 6 μm, 6 μm, 18 μm, and 3 μm, respectively.
m.

Examples 6 and 7 A hydrophilic paint was prepared by changing the composition ratio of Cataroid AS-3 and the water-soluble acrylic resin according to Synthesis Example 1 to obtain an aluminum paint. Example 6 is a mixture of 99.9 parts of a water-soluble acrylic resin and 0.1 part of a cataloid AS-3 by dry weight, and Example 7 is a mixture of 50 parts of a water-soluble acrylic resin and a cataloid AS-3 by dry weight. Were mixed in the same manner as in Example 1 to prepare a hydrophilic coating material to obtain an aluminum coating material.

Examples 8 to 10 Example 1 was repeated except that the water-soluble acrylic resin obtained in Synthesis Examples 2 to 4 was used instead of the water-soluble acrylic resin.
In the same manner as in the above, a hydrophilic coating material was prepared to obtain an aluminum coating material.

Example 11 The water-soluble acrylic resin according to Synthesis Example 1 was dried at 60% by weight.
Parts, 30 parts of Cataroid AS-3 and 10 parts of hydroxyethyl cellulose (SP-250: Daicel Chemical Industries, Ltd.) were mixed, and a hydrophilic paint was prepared and aluminum-coated in the same manner as in Example 1 below. Wood was obtained.

Example 12 The water-soluble acrylic resin according to Synthesis Example 1 was dried at a dry weight of 60%.
Parts, 30 parts of Cataroid AS-3 and 10 parts of polyvinyl alcohol (GL-5: Nippon Synthetic Chemical Industry Co., Ltd.) manufactured by Nippon Synthetic Chemical Industry Co., Ltd. A hydrophilic paint was prepared to obtain an aluminum coating material.

Example 13 The water-soluble acrylic resin according to Synthesis Example 1 was dried at a weight of 60%.
Parts, 30 parts of cataloid AS-3 and 10 parts of polyethylene glycol (PAOGEN PP-15: manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), and a hydrophilic paint was prepared in the same manner as in Example 1. An aluminum coating was obtained.

Example 14 The water-soluble acrylic resin according to Synthesis Example 1 was dried at a dry weight of 50%.
Parts, 30 parts of Cataroid AS-3 and 20 parts of an emulsion of polyurethane (Superflex 110: manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), and then a hydrophilic coating material was prepared in the same manner as in Example 1. Then, an aluminum coating material was obtained.

Example 15 The water-soluble acrylic resin according to Synthesis Example 1 was dried at a dry weight of 60%.
Parts, 30 parts of cataloid AS-3 and 10 parts of non-swellable synthetic mica (MK-100: manufactured by Corp Chemical Co., Ltd.), and a hydrophilic coating material was prepared in the same manner as in Example 1; An aluminum coating was obtained. Example 16 The water-soluble acrylic resin according to Synthesis Example 1 was dried at a weight of 60%.
Parts, 30 parts of cataloid AS-3, water-soluble nylon (A
10 parts of Q-nylon A-90: manufactured by Toray Industries, Inc.
Thereafter, a hydrophilic coating material was prepared in the same manner as in Example 1 to obtain an aluminum coating material.

Example 17 The water-soluble acrylic resin according to Synthesis Example 1 was dried at a dry weight of 50%.
Parts, 30 parts of cataloid AS-3 and 20 parts of calcium alginate beads (manufactured by Nisshinbo Co., Ltd.) were mixed, and a hydrophilic coating material was prepared in the same manner as in Example 1 to obtain an aluminum coating material. .

Comparative Example 1 The water-soluble acrylic resin obtained in Synthesis Example 1 was applied and baked on a phosphoric acid chromated aluminum plate in the same manner as in Example 1 to obtain an aluminum coating material.

Comparative Example 2 50 parts by weight of AQ-nylon A-90, 30 parts by weight of Elastron W-11 and 2 parts of alumina sol-200
0 parts (in the state of a primary dispersion without coagulation) were mixed, and a hydrophilic coating material was prepared in the same manner as in Example 1 to obtain an aluminum coating material.

Comparative Examples 3 and 4 Example 1 was repeated except that the water-soluble acrylic resin obtained in Synthesis Examples 5 and 6 was used instead of the water-soluble acrylic resin.
In the same manner as in the above, a hydrophilic coating material was prepared to obtain an aluminum coating material.

The compositions of the hydrophilic paints of Examples 1 to 17 and Comparative Examples 1 to 4 are shown in Table 2.

[0058]

[Table 2]

For each of the obtained aluminum coating materials (hydrophilic coating film), a hydrophilicity sustaining test, an adhesion test,
A corrosion resistance test was performed.

(1) Sustained Hydrophilicity Test The coated aluminum plate was immersed in tap water (a flow rate of 1 liter / min per minute for a 30 liter plastic container) for 8 hours, and then the electric oven at 50 ° C. was used. The drying for 16 hours was regarded as one cycle, and the water contact angle was measured continuously up to 20 cycles. To measure the water contact angle, place the sample horizontally, drop 5 μl of pure water on it, and use a contact angle meter (CA
-Z: Kyowa Interface Science Co., Ltd.). The evaluation is as follows.

◎: less than 5 degrees ：: 5 degrees or more and less than 20 degrees Δ: 20 degrees or more and less than 30 degrees ×: 30 degrees or more

(2) Adhesion test The coated aluminum plate was wiped with a dry rag and evaluated. ：: Cannot be wiped off ○: Surface layer can be wiped off, but still remains on substrate ×: Can be wiped off

(3) Corrosion resistance test A salt water spray test was performed on the painted aluminum plate for 40 minutes.
This was performed for 0 hour, and the ratio of the area of the corroded portion was evaluated. ：: 0% or more and less than 1% ： １: 1% or more and less than 5% ×: 5% or more

Table 3 shows the results of the tests (1) to (3).

[0065]

[Table 3]

[0066]

The coating film obtained by drying and curing the hydrophilic coating composition of the present invention has extremely good hydrophilicity persistence, and has good adhesion and corrosion resistance. The addition of alumina sol in an amorphous gel state also has the effect of extremely reducing the wear of the mold and extending the life of the mold, and the hydrophilic paint is a hydrophilic paint suitable for aluminum fin materials for heat exchangers. It provides a coating.

────────────────────────────────────────────────── ─── Continuation of front page (56) References JP-A-59-229197 (JP, A) JP-A-63-63726 (JP, A) JP-A-2-219879 (JP, A) JP-A-3-3 86750 (JP, A) JP-A-6-172777 (JP, A) JP-A-3-215082 (JP, A) JP-A-8-104828 (JP, A) JP-B-51-9717 (JP, B1) (58) Field surveyed (Int.Cl. ⁷ , DB name) C09D 1/00-201/10 F28F 13/18 F28F 1/32

Claims (1)

(57) [Claims] 1. Alumina sol (a) in which the primary particles have a feather-like, rod-like or dendritic shape and form, and are aggregated in advance by a synthesis method and have an average particle size of 0.5 to 20 μm, and 10 to 80 parts of an α, β unsaturated monomer having a sulfonic acid or sodium sulfonate group, 10 to 50 parts of an α, β unsaturated monomer having a carboxylic acid group,
Α, β unsaturated monomers having an alcoholic hydroxyl group
A highly hydrophilic paint, comprising: a water-soluble resin (b) obtained by copolymerizing from 50 to 50 parts.