JP2564478B2 - Method for making hydrophilic metal material containing aluminum - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for hydrophilizing the surface of an aluminum-containing metal material, that is, aluminum or an aluminum alloy material. More specifically, the heat dissipation of an aluminum-containing metal heat exchanger is described. The present invention relates to a method of hydrophilizing the surfaces of fins constituting the cooling section and the cooling section.

[0002]

2. Description of the Related Art Conventionally, in fins of a heat exchanger composed of an aluminum-containing metal material, an anodized film, a boehmite film, a surface treatment for the purpose of preventing white rust,
Although resin film treatments are performed at the same time, the film surface formed by these treatments has almost no water wettability,
Rather it is water repellent. In addition, chromate conversion film treatment is also performed to prevent white rust. The chromate conversion film has some wettability at the initial stage of film formation, but sufficient hydrophilicity cannot be obtained only by chromate treatment. Further, since the chromate conversion film tends to change from a hydrophilic surface to a hydrophobic surface with the passage of time particularly under heating and drying conditions, it is problematic as a fin film of a heat exchanger.

On the other hand, many heat exchangers are designed so that the areas of the heat radiating portion and the cooling portion are as large as possible in order to improve the heat radiating or cooling effect, so that the fin spacing is extremely small. Therefore, when used for cooling, moisture in the atmosphere is condensed on the surface of the heat exchanger, especially on the fin gap. The water condensed in this way is more likely to become water droplets as the fin surface is more hydrophobic, and also causes clogging in the fin gap to increase ventilation resistance and reduce the heat exchange rate.
Further, the water droplets accumulated in the fin gap are easily scattered by the blower of the heat exchanger, cannot be received by the water droplet receiving tray installed in the lower part of the heat exchanger, and the vicinity of the heat exchanger is soiled with water.

Therefore, in order to prevent water droplets from remaining in the fin gaps and causing clogging due to water droplets, a treatment for imparting hydrophilicity to the aluminum surface and improving water wettability has been proposed. In particular, many methods for treating fines with silicates such as water glass have been proposed because they have high wettability and heat resistance and are inexpensive. From the viewpoint of using inorganic compounds such as silicates and organic compounds, the conventional methods can be classified into the following four layer forming methods.

One of the methods (a) is a method in which an aqueous silicate solution is directly applied to the surface of the aluminum which has been subjected to the chemical conversion treatment and then dried. As this method, for example, Japanese Patent Laid-Open No.
No. 38645 is available.

As the next method (b), JP-A-60-221
Japanese Patent No. 582 discloses a fin material in which a hydrophilic inorganic film layer composed of silicate, boehmite, or the like is formed on an aluminum plate, and a hydrophilic organic polymer film having a degree of polymerization of 50 or more is formed thereon. are doing.

As another method (C), a method has been proposed in which an organic polymer film is formed on the surface of aluminum in advance, and then a silicate solution is applied onto the film and dried. This method is described, for example, in JP-A-56-205596. The fin material disclosed in this publication has an organic polymer resin anticorrosion film formed on an aluminum plate, and a hydrophilic film composed of a silicate such as silica sol, silicic acid, and water glass formed thereon. Is.

As another method (d), it has been proposed to apply a mixture of an organic polymer compound and an inorganic silicate on the surface of aluminum. This proposal can be found, for example, in the following publication. Japanese Unexamined Patent Publication No. 61-8598 discloses a styrene-maleic acid copolymer, polyacrylamide, butylene maleic acid copolymer, polyacrylic acid or salts thereof, and xM.
₂ O · ySiO ₂ (M = Li, Na, K, y / x ≧ 2)
Discloses a fin material having a mixture with a silicate compound represented by JP-A-60-101156 discloses an aluminum hydrophilic film forming agent containing an alkali silicate and a compound containing a carbonyl group (aldehydes, esters, amides, etc.).

Next, among the conventional techniques using organic compounds for hydrophilic treatment of aluminum, Japanese Patent Laid-Open No. 59-20559
No. 6 relates to a method using an organic solvent. That is, the organic compound disclosed in the publication is an acrylic resin, an epoxy resin, a urethane resin such as polyvinyl chloride-
Vinyl acetate, polyethylene, vinyl resin such as polypropylene, styrene resin, phenol resin, fluorine resin, silicon resin, diallyl phthalate resin, polycarbonate resin, polyamide resin, alkyd resin, polyester resin, These include urea melamine-based resins, polyacetal-based resins and fibrin-based resins, which are often applied using an organic solvent. On the other hand, a low molecular weight organic compound having a carbonyl group (eg glyoxal) and a water-soluble organic polymer compound (eg acrylamide and acrylic acid) contained in the hydrophilic treatment agent for aluminum described in JP-A-60-101156. Copolymer) is coated in aluminum, diluted with water and dried by heating.

Furthermore, when the prior art of using polyacrylamide as an organic compound for hydrophilic treatment is examined, JP-A-60-101156 and JP-A-61-8.
As disclosed in Japanese Patent No. 598, it is known that polyacrylamide is used as a hydrophilic treatment agent, but when the concentration in an aqueous solution is low, it is uniformly mixed, but the concentration is increased during the drying step or the like. As a result, the alkali silicate layer and the polymer layer undergo phase separation, which often causes variations in reproducibility of performance.

In the method disclosed in JP-A-60-221582, a polyacrylamide is formed on a hydrophilic inorganic film layer as a hydrophilic organic film forming agent, and a hydrophilic organic polymer film layer having an appropriately adjusted degree of polymerization is used. It has been proposed to facilitate solvent degreasing of press oil during processing and fill the pinholes of the inorganic hydrophilic film with the hydrophilic organic polymer layer remaining after degreasing on the hydrophilic inorganic film. In this publication, polyacrylamide is cross-linked by a cross-linking agent composed of a compound such as zirconium or titanium, within the range where all hydrophilic groups are not cross-linked. The fin material of the above publication is
What remains as a hydrophilic film after solvent degreasing as a heat exchanger member is the lowest inorganic hydrophilic film layer formed by silicate treatment or boehmite treatment.

[0012]

The film formed by the above-mentioned conventional hydrophilic treatment layer construction method (a) (direct application of silicate aqueous solution to chemical conversion treated aluminum) is a hydrophilic film but not a corrosion resistant film. Therefore, there are drawbacks such that the corrosion resistance is lowered and the tendency of white rust to occur is increased due to the film formation.

The conventional hydrophilic treatment layer forming method (b)
In (forming an organic polymer film after forming an inorganic film), the main component of the hydrophilic film is an inorganic film such as boehmite or silicate, and the organic film becomes water repellent because the inorganic film is contaminated with the press oil. The main purpose is to prevent this, and after this purpose, it is removed together with the press oil in the degreasing step, so that not only the corrosion resistance but also the hydrophilicity is insufficient.

The conventional hydrophilic treatment layer construction method (C)
In (Silicate film formation after organic polymer film formation), corrosion resistance and initial hydrophilicity are sufficient, but the upper layer silicate is easily washed away by condensed water, so there is a drawback that hydrophilicity persistence is poor. It was

The conventional hydrophilic treatment layer construction method (d)
Since the silicate contained in the film formed on aluminum by applying a mixture of organic polymer and silicate is hydrophilic, fins treated by this method tend to promote white rusting of aluminum. . Further, since the silicate and the organic polymer are phase-separated at the stage of coating and drying the mixture on the aluminum-containing metal material, there is a large variation in the performance depending on the production conditions, and the fin is often insufficient in hydrophilicity.

Therefore, as a result of various examinations of the prior art, the present inventors further examined the organic polymer film to be coated on the aluminum-containing metal material. The method described in JP-A-59-205596, which uses an organic polymer film having water resistance and corrosion resistance as the undercoat as described above, uses an organic solvent in many cases, so that there is a problem of fire or environmental pollution. It is difficult to apply a water glass aqueous solution as a topcoat thinly and uniformly because the hydrophilicity of the generated undercoat coating film is low.

Therefore, the present inventor studied a method of applying an aqueous solution of an organic polymer compound to aluminum. There are various water-soluble organic compounds used for the undercoat,
It is easily available and inexpensive, has a group that can be rendered insoluble by the reaction with a cross-linking agent, and the formed film is stable against hydrolysis reactions, etc., and at the same time, is resistant to external force and heat applied during subsequent processing. On the other hand, the polymer of (meth) acrylamide and its derivative is most suitable from the viewpoint of maintaining sufficient strength.

In the method disclosed in Japanese Patent Laid-Open No. 60-221582, which discloses polyacrylamide and the like, since almost no polyacrylamide remains on the fin material, the method is the same as that of the prior art (see FIG. It does not indicate a method corresponding to (a) and using a water-soluble organic compound such as polyacrylamide as a permanent film of fin.

As a result of various studies as described above, the present inventor has provided a coating fin having sufficient corrosion resistance and hydrophilicity (including running water durability) even if only one organic polymer compound is used as the layer structure. Thus, the inventor has reached the idea that the drawbacks of the layer construction technique (a) can be solved and that hydrophilic coating layers having various layer structures can be realized.

A zwitterionic copolymer layer having high corrosion resistance as described above and sufficient hydrophilicity for topcoating is used as an undercoating film, and a highly hydrophilic organic polymer film is formed thereon. It is also possible to prevent the inorganic hydrophilic layer, such as silica gel or water glass, that wears the tool used during the post-processing from coming out as the surface layer.

[0021]

The method for hydrophilizing an aluminum-containing metal according to the present invention is represented by the general formula (I):

Embedded image A zwitterionic polymer (A) obtained by copolymerization of the monomer (I) represented by the formula (1), a cationic unsaturated monomer (II) and an anionic unsaturated monomer (III), and a homopolymer of the monomer (I). A cross-linking agent containing at least one selected from the group consisting of zwitterionic polymers (B) obtained by post-ionic treatment of a polymer or copolymer, and at least one water-soluble compound of chromium, titanium and aluminum ( An aqueous solution containing C) is applied to the surface of the aluminum-containing metal material and dried.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION It is known that polymers of acrylamide (R ₁ , R ₂ , R ₃ = H in the general formula (I)) have excellent hydrophilicity, but linear structure polymers are soluble in water. It is not suitable as a hydrophilic film for heat exchangers because it is easy to do. However, when polyacrylamide is used as a zwitterionic polymer and a network structure is formed by a crosslinking agent containing at least one water-soluble compound of chromium, titanium and aluminum, it becomes insoluble in water and can be used as a film of a heat exchanger. It has been found that various excellent properties as a film appear. That is, even if the water-insolubilized film obtained by the method of the present invention is placed in running water, it does not run off, and a film having permanent durability can be formed. The coating also prevents it from dissolving in organic solvents that may be used in post-processing steps, such as trichloroethane. In order to obtain such excellent properties, the zwitterionic polymers (A) and (B)
It is effective to uniformly mix the above-mentioned water-soluble chromium, a cross-linking agent containing titanium or an aluminum compound with the cross-linking agent so that the cross-linking reaction proceeds sufficiently.

Further, as will be described later, even when chromic acid, dichromic acid or salts thereof are added for the purpose of imparting corrosion resistance to the surface of the aluminum-containing metal material serving as a substrate, the above monomers (I), ( The polymers produced by II) and (III) have sufficient mixing stability, so that the corrosion-resistant chemical conversion treatment of the aluminum-containing metal material surface with chromic acid and the (co) polymer coating formation treatment are performed. It is completed in a single operation, and both treatment effects are combined to provide excellent surface performance.

The present invention will be specifically described below. As the water-soluble cross-linking agent (C), water-soluble compounds of Cr, Ti and Al capable of forming a complex compound with the polymers (A) and (B), particularly chromic acid, dichromic acid and salts thereof having high water-solubility, Diisopropoxytitanium bisacetylacetone, a reaction product of lactic acid and titanium alkoxide, and aluminum sulfate are effective.

The cross-linking agent used in the method of the present invention is a cross-linking compound of other metals such as zirconyl nitrate, zirconyl acetate, ammonium zirconyl carbonate, zircon hydrofluoric acid and salts thereof in addition to the above-mentioned water-soluble chromium, titanium and aluminum compounds. May be used in combination, or a water-soluble organic cross-linking agent may be used in combination.

As the water-soluble organic cross-linking agent, a water-soluble blocked polyisocyanate and / or a water-soluble polymethylol, polyglycidyl or polyaziridyl compound can be used. An example of this is NaHSO
Polyisocyanates blocked with ₃ (eg, Elastron manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.), methylol melamine, methylol urea, methylol polyacrylamide, diglycidyl ether of polyethylene oxide, diaziridyl polyethylene oxide and the like.

As the water-soluble crosslinking agent, an organic crosslinking agent and an inorganic crosslinking agent can be used in combination. Examples thereof include the combined use of water-soluble Cr, Ti, Al compounds and water-soluble blocked polyisocyanates, polymethylols, polyglycidyls, and polyaziridyl compounds.

The amount of the cross-linking agent (C) used varies depending on the type of the cross-linking agent, and is small when the coating films of the (co) polymers (A) and (B) are used as an undercoat mainly composed of corrosion resistance. Since the number of cases where it is used in a single coating type increases, it depends on the use of the coating film of the copolymers (A) and (B), but generally speaking, it is based on 100 parts by weight of the polymer or the copolymer used. 1 to 400 parts by weight, preferably 5 to 200
Parts by weight are used.

Specific examples of the zwitterionic polymer used in the present invention include the general formula: (I ') _l- (II) _m- (III) _n- (IV) _o . In the above formula, l> 40, m = 1 to 59, n = 1 to 5
9, 0 ≦ o <30, l + m + n + o = 100. In the above formula, (I ') is acrylamide, methacrylamide, N
They are methyl acrylamide and N dimethyl acrylamide.

(IV) is a copolymerizable nonionic monomer, and specific examples thereof include 2-hydroxy (meth) acrylate, diacetone acrylamide, methylol acrylamide, acryloylmorpholine, acrylonitrile, and (meth) acrylic acid ester. , Styrene and vinyl acetate.

[0031]

Embedded image Is.

[0032]

[Chemical 4] Alternatively, it is a copolymer of it with an unsaturated carboxylic acid such as maleic anhydride or itaconic acid, or an unsaturated compound having a sulfonic acid (phosphonic acid) group. N in the above formulas, for example, f) -COOH (or a salt thereof) bets) -SO ₃ H (or a salt thereof)

[0033]

Embedded image Represents

Specific examples of the post-ionization treatment of the polymer include i) conversion of a part of the amide group of the copolymer having an amide group and a cation group into a carboxyl group by hydrolysis,

[0035]

[Chemical 6]iii) of a copolymer having an amide group and a side chain ester group
Side chain ester group and alkylenediamine (H₂N-R₆−
NH₂) -CONH-R₆-NH ₂Introduction of
(However, R₆Is C₂~ C₆Is an alkylene group of), iv) ii) and iii) of the amino group obtained by the reaction
It is a quaternary amino compound obtained by killing.

As the coating method of the above-mentioned aqueous solution, dipping, spraying, brush, roll, flow coating method, etc. are used.
In order to suppress the stringing phenomenon during coating, it is appropriate that the molecular weight is 2,000,000 or less, preferably 1,000,000 or less. The concentration and the viscosity are appropriately selected depending on the coating method used, the desired film thickness and the like. The coating thickness is 0.1 to 10 microns or less, preferably 0.2 to 2 microns, in order to enhance the thermal efficiency and contribute to the corrosion resistance, especially when used in a heat exchanger. preferable.

The aluminum-containing metal material may be degreased in advance and directly applied or subjected to chemical conversion treatment such as boehmite treatment or chromate treatment and then applied with the above coating aqueous solution. However, in the case of direct application, chromic acid, The addition of dichromic acid and its salts is particularly effective.

In addition to the above, rust preventives, fillers, colorants, surfactants, defoamers, leveling agents, antibacterial and antifungal agents, etc. are added within the range not impairing the purpose of the present invention or the film performance. You can

As described above, water is used as the paint solvent, but it does not prevent the combined use of water-soluble solvents such as alcohols, ketones and cellosolves in order to accelerate the drying and improve the state of the coating film.

The stability of the coating liquid differs depending on the composition, but it is necessary to avoid the use of the amphoteric polymer in the vicinity of the isoelectric point because precipitation separation of the polymer occurs.

[0041]

According to the method of the present invention, a coating film obtained by crosslinking a zwitterionic polymer becomes insoluble in water and can be used as a coating film for aluminum fins. It was found that the corrosion resistance was excellent. A coating film having such excellent properties is suitable as a surface coating for an aluminum-containing metal heat exchanger.

[0042]

The present invention will be further described with reference to the following examples.
The test methods in the examples were as follows. Test method-Contact angle The contact angle of a small water droplet having a diameter of 1 to 2 mm, which was allowed to stand on a solid surface, was measured using a FACE contact angle meter CA-P type (Kyowa Interface Chemistry). Early stage after processing, immersion in running water 1
The measurement was made for each of those after a week. -Corrosion resistance It is shown by the spray test time until the white rust area reaches 5% based on the salt spray test method JIS Z-2371. - running water after 8H _R immersed in stability at room temperature in running water, 16
H _R , the treatment of drying at 80 ° C. is 1 cycle, and 5
The contact angle to water after cycle is shown.

Example 1 An aqueous solution of 20 g / liter of a copolymer of 60 mol% of acrylamide, 30 mol% of sodium styrenesulfonate, and 10 mol% of dimethylaminoethyl acrylate and 4 g / liter of chromic anhydride was placed on an aluminum plate. And was heated and dried in an electric drying oven at 250 ° C. The weight of the applied coating film was 0.3 g / m ² . Table 1 shows the processing conditions and test results.

[0044]

[Table 1]

[0045]

According to the method of the present invention, a film excellent in hydrophilicity and corrosion resistance can be formed on the surface of an aluminum-containing metal material.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Ai Nishihara 1-151-1 Nihonbashi, Chuo-ku, Tokyo Nihon Parkerizing Co., Ltd. (72) Inventor Hiroshi Okita 1-15-1 Nihonbashi, Chuo-ku, Tokyo (72) Inventor Yoshinori Sakamoto Nihonbashi 1-15-1 Nihonbashi, Chuo-ku, Tokyo Nihon Parkerizing Co., Ltd.

Claims (1)

(57) [Claims] 1. A compound represented by the general formula (I): A zwitterionic polymer (A) obtained by copolymerization of the monomer (I) represented by the formula (1), a cationic unsaturated monomer (II) and an anionic unsaturated monomer (III), and a homopolymer of the monomer (I). A cross-linking agent containing at least one selected from the group consisting of zwitterionic polymers (B) obtained by post-ionic treatment of a polymer or copolymer, and at least one water-soluble compound of chromium, titanium and aluminum ( An aqueous solution containing C),
A method for hydrophilizing an aluminum-containing metal material, which comprises coating the surface of the aluminum-containing metal material and drying.