JP2564479B2 - 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. More specifically, it constitutes a heat radiating portion and a cooling portion of an aluminum-containing metal heat exchanger. The present invention relates to a method for hydrophilizing the surface of fins.

[0002]

2. Description of the Related Art Conventionally, in fins of aluminum heat exchangers composed of aluminum-containing metal materials,
As surface treatments for the purpose of preventing white rust, anodic oxide film forming treatments, boehmite film forming treatments, and resin film forming treatments are also performed, but the film surfaces formed by these treatments have almost no water wettability. Instead, it shows water repellency. Further, chromate conversion film treatment has been carried out to prevent white rust, but the chromate conversion film has some wettability at the initial stage of film formation, but sufficient chromate treatment cannot provide sufficient hydrophilicity. In addition, the chromate chemical conversion film, especially under heating and drying conditions,
Since the hydrophilic surface tends to change to a hydrophobic surface, there is a practical problem as a fin film for a heat exchanger.

On the other hand, in many heat exchangers, the fins are extremely narrow because the heat radiating portion and the cooling portion are designed to have the largest possible area in order to improve the heat radiating or cooling effect. Therefore, when this fin is used for cooling, moisture in the atmosphere is condensed on the heat exchanger surface, particularly on the fin gap, and the condensed water is more likely to form water droplets as the fin surface has higher hydrophobicity. For,
There is a problem that clogging occurs in the fin gap to increase ventilation resistance and reduce the heat exchange rate.

Further, the water droplets retained in the fin gap are easily scattered by the blower attached to the heat exchanger, and the scattered water cannot be sufficiently received by the water droplet receiving tray installed at the lower portion of the heat exchanger, and therefore, The vicinity of the heat exchanger is polluted with water. Therefore, in order to prevent water droplets from accumulating in the fin gap and becoming water droplets and clogging the heat exchanger, it is necessary to impart hydrophilicity to the surface of the aluminum-containing metal material to improve its wettability. Proposed to apply. In particular, as a method of treating the fin surface with a silicate such as water glass, many improvement methods have been proposed because a surface having high wettability and heat resistance can be formed at low cost. From the viewpoint of the method of using an inorganic compound such as silicate and an organic compound, the conventional methods are classified into the following four layer constitution methods.

One of the methods (a) is a method of directly applying an aqueous silicate solution to the surface of the chemical conversion treated aluminum-containing metal material and drying it. As this method, there is, for example, Japanese Patent Laid-Open No. 50-38645. As the following method (b), JP-A-60-221582 discloses that a hydrophilic inorganic coating layer composed of silicate, boehmite or the like is formed on an aluminum-containing metal plate, and the degree of polymerization is 50 on the hydrophilic inorganic coating layer. The method for producing a fin material for forming the above hydrophilic organic polymer film is disclosed.

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

As another method (d), a method is known in which a mixture of an organic polymer compound and an inorganic silicate is applied to the surface of a metal material containing aluminum. This method is disclosed, for example, in the following publication. JP-A-61-859
No. 8 discloses 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), a fine material having a mixture with a silicate compound as a coating layer is disclosed. Further, JP-A-60-101156 discloses a hydrophilic film forming agent for aluminum-containing metal materials, which contains an alkali silicate and a compound containing a carbonyl group (aldehydes, esters, amides, etc.). ing.

Next, among the conventional techniques of using an organic compound for hydrophilic treatment of an aluminum-containing metal material, Japanese Patent Laid-Open Publication No. Sho.
No. 9-205596 relates to a method using an organic solvent. That is, the organic compound shown in the publication is an acrylic resin, an epoxy resin, a urethane resin, for example, a vinyl resin such as vinyl chloride-vinyl acetate copolymer, polyethylene, a polyolefin resin such as polypropylene, Styrene resin, phenol resin, fluorine resin, silicon resin, diallyl phthalate resin, polycarbonate resin, polyamide resin, alkyd resin, polyester resin, urea melamine resin, polyacetal resin and fibrin resin Etc., and these are often applied using organic solvents. On the other hand, the hydrophilic treatment agent for aluminum-containing metal materials described in JP-A-60-101156 is a low-molecular organic compound having a carbonyl group (eg glyoxal) and a water-soluble organic polymer compound (eg acrylamide). Acrylic acid copolymer), which are diluted with water, coated on the surface of the aluminum-containing metal material, and dried by heating.

Further, a conventional technique using polyacrylamide as an organic compound for hydrophilic treatment will be examined. JP-A-60-101156, and JP-A-6-101156
As disclosed in JP-A-1-8598, it is known to use polyacrylamide as a hydrophilizing agent, but when polyacrylamide is used in combination with an alkali silicate, the concentration of polyacrylamide in an aqueous solution is low. In these cases, these are uniformly mixed, but since the alkali silicate layer and the polymer layer undergo phase separation as the concentration increases in the drying step, etc., there is a drawback that the reproducibility of performance often causes variations. is there.

In the method described in JP-A-60-221582, a hydrophilic organic polymer film is formed on a hydrophilic inorganic film layer by using polyacrylamide as a hydrophilic organic film forming agent. By appropriately adjusting the degree of polymerization, solvent degreasing of the press oil during processing is facilitated, and pinholes of the hydrophilic inorganic film are closed by the hydrophilic organic polymer layer remaining thereon after degreasing. Is proposed. In the method of the publication, polyacrylamide is cross-linked by a cross-linking agent composed of a compound such as zirconium or titanium to the extent that uncrosslinked hydrophilic groups remain. However, the fin material of the above publication, when subjected to solvent degreasing as a heat exchanger member, finally remains as a hydrophilic film is the lowest inorganic hydrophilic film layer formed by silicate treatment or boehmite treatment. is there.

[0011]

A film formed by the conventional method (a) for forming a hydrophilic treatment layer (direct application of a silicate aqueous solution to a chemically treated aluminum-containing metal material) is a hydrophilic film, but has a corrosion resistance. Since it is not a film, there are drawbacks such as the corrosion resistance of the obtained hydrophilized metal material is lowered and the tendency of white rust to occur is increased rather than the film formation.

Further, in the conventional hydrophilic treatment layer forming method (b) (organic polymer film formation after inorganic film formation),
The main component of the hydrophilic coating is an inorganic coating such as boehmite or silicate, and the organic polymer coating is formed mainly for the purpose of preventing the inorganic coating from being contaminated with press oil and becoming water repellent. After the object was achieved, it was removed together with the press oil in the degreasing step, so that the degreased metal material had insufficient corrosion resistance as well as its hydrophilicity.

Further, according to the conventional method for forming a hydrophilic treatment layer (C) (forming a silicate film after forming an organic polymer film), the resulting film has sufficient corrosion resistance and initial hydrophilicity, but the upper layer of silicic acid is Since the salt is easily washed away by the condensed water, there is a drawback that the durability of hydrophilicity is poor.

Furthermore, the conventional hydrophilic treatment layer construction method (d)
In coating (mixture of organic polymer and silicate), the film formed on the aluminum-containing metal material contains silicate, and this silicate is hydrophilic. It tends to accelerate the occurrence of white rust on the material. In addition, when the mixture is applied to an aluminum-containing metal material and dried, the silicate and the organic polymer are phase-separated, so that there is a large variation in performance depending on the production conditions, and the fin becomes insufficiently hydrophilic. There are many.

In view of the above problems of the prior art, the present inventors have made various investigations on the prior art, and in particular, have further investigated organic polymer coatings applied on aluminum-containing metal materials. An organic polymer film that imparts water resistance and corrosion resistance as described above is formed as an undercoat layer.
Since the method of JP05596A often uses an organic solvent, there is a problem of fire and environmental pollution. At the same time, since the generated undercoat coating film has low hydrophilicity, a water glass aqueous solution is overcoated thereon. As a result, it is difficult to apply it thinly and uniformly.

Therefore, the present inventor has investigated a method of applying an aqueous solution of various organic polymer compounds onto an aluminum-containing metal material. As the water-soluble organic compound used for the undercoat, various ones are known, but they are easily available and inexpensive, have a group that can be rendered insoluble by the reaction with a cross-linking agent, and the formed film has a hydrolysis reaction. Considering that it is stable against the like, and at the same time, it retains sufficient strength against external force and heat applied during the subsequent processing, the polymer of (meth) acrylamide and its derivative It was confirmed to be optimal.

Among the above methods (d), Japanese Patent Application Laid-Open No. 60-221582 discloses polyacrylamide and the like.
In the method of No. 2, since polyacrylamide hardly remains in the hydrophilized layer formed on the fin material, this method is substantially the same as the conventional method (a) in terms of the layer constitution. Moreover, a hydrophilic treatment method for fixing a water-soluble organic compound such as polyacrylamide as a permanent film on the surface of the fin has not been known yet.

As a result of various investigations as described above, the present inventor has found that the hydrophilization layer has sufficient corrosion resistance and hydrophilicity (including running water durability) even if only a single layer made of an organic polymer compound is used. It has come to the idea that, if a coating fin having the above can be provided, the drawbacks of the method (a) for forming a hydrophilic inorganic layer can be solved, and a hydrophilic coating layer having various layer structures can be realized. The organic polymer compound layer as described above is used as an undercoating film, and a silicate film is formed thereon as in the layer constitution method (b) to further improve the property of fin in terms of hydrophilicity. Be expected. Further, if necessary, as a base coat, a film having high corrosion resistance and having sufficient hydrophilicity for a uniform top coat is formed, and a high hydrophilic property is formed on the two-layer structure thus obtained. By forming the organic film of (1), it is possible to avoid exposing an inorganic hydrophilic layer, such as silica gel or water glass, which causes abrasion to a tool used during post-processing as a surface layer.

[0019]

The method of hydrophilizing the surface of an aluminum-containing metal material according to the present invention is represented by the general formula (I).

[0020]

Embedded image A water-soluble polymer or copolymer (A) obtained by polymerization or copolymerization of a monomer represented by the following formula, and chromium, titanium or the like, which can be made water-insoluble by crosslinking the polymer or copolymer (A). It is characterized in that a mixed aqueous solution with a crosslinking agent (B) containing at least one water-soluble compound of aluminum is applied to the surface of an aluminum-containing metal material and dried and crosslinked, whereby hydrophilicity is obtained. A film can be formed.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION It is known that polymers of acrylamide (in the case of R ₁ , R ₂ and R ₃ = H in the general formula (I)) are excellent in hydrophilicity. The polymer (1) is easily dissolved in water and is not suitable for a hydrophilic film of a heat exchanger. However, it has been found that when polyacrylamide is crosslinked with a crosslinking agent to form a network structure, it becomes insoluble in water and can be used as a film of a heat exchanger, and various excellent properties of the film appear. . That is, in the present invention, by using a water-soluble chromium, titanium or aluminum compound as a cross-linking agent, the formed film is made water-insoluble, and even if it is placed in running water, it does not run off and has a durable durability. A certain film can be formed, and when an organic solvent is used in the post-processing step, it is possible to prevent dissolution even in this organic solvent such as trichloroethane. In order to obtain such excellent properties, it is necessary to uniformly mix a cross-linking agent containing a water-soluble chromium, titanium or aluminum compound in a water-soluble (co) polymer solution to allow the cross-linking reaction to proceed sufficiently. Is.

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 water-soluble crosslinking agent (B Since the above (co) polymer (A) crosslinked by) has a sufficient mixing stability, the surface of the aluminum-containing metal material is subjected to a corrosion-resistant chemical conversion treatment with chromic acid, and a (co) polymer coating film is formed. The treatment is completed in one operation, and both treatment effects are combined to obtain excellent surface performance.

The specific conditions for crosslinking will be described below. As the water-soluble cross-linking agent (B), as a water-soluble metal compound capable of forming a complex compound with the water-soluble polymer or copolymer (A), a compound having particularly high water-solubility among Cr, Ti and Al compounds, That is, chromic acid, dichromic acid and salts thereof, diisopropoxytitanium bisacetylacetone, a reaction product of lactic acid and titanium alkoxide, and aluminum sulfate are used.

As the water-soluble cross-linking agent (B), other inorganic cross-linking agent or organic cross-linking agent may be used in combination with the cross-linking agent. As such a water-soluble organic cross-linking compound, one or more selected from water-soluble blocked polyisocyanates, water-soluble polymethylol, polyglycidyl, and polyaziridyl compounds can be used. Specific examples thereof include polyisocyanates blocked with NaHSO ₃ (eg, Elastron manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), methylolmelamine, methylolurea, methylolated polyacrylamide, diglycidyl ether of polyethylene oxide, diaziridylated polyethylene oxide and the like. is there. Examples of the combined use of the inorganic cross-linking agent and the organic cross-linking agent include the combined use of a water-soluble Cr, Ti or Al compound and a water-soluble blocked polyisocyanate, polymethylol, polyglycidyl or polyaziridyl compound. As other inorganic cross-linking agents, water-soluble compounds of metals having a coordination number of 4 or more except chromium, aluminum and titanium, such as zirconyl nitrate, zirconyl acetate, zirconyl ammonium carbonate, zircon hydrofluoric acid and salts thereof are used in combination. be able to.

The amount of the cross-linking agent (B) used varies depending on the type of the cross-linking agent, and the coating film of the (co) polymer (A) is used as an undercoat mainly composed of corrosion resistance, or is used in a single coating type. Generally speaking, 1 to 400 parts by weight, preferably 5 to 200 parts by weight, of the crosslinking agent is used with respect to 100 parts by weight of the polymer or copolymer to be used, although it varies depending on whether or not. Drying is generally performed at 90 to 300 ° C, more preferably 100 to 250 ° C.

The method for forming the coating film will be further described below. The molecular weight of the polymer or copolymer (A) used in the present invention is preferably 5,000 or more, and when the molecular weight is 5,000 or less, especially when the hydrophilicity is high, a crosslinking agent for water insolubilization is used. It is necessary to increase the usage rate.

As the polymer and the copolymer (A),
(I) acrylamide, methacrylamide, N-methyl acrylamide, or N-dimethyl acrylamide (I ') polymer or copolymer, (ii) the monomer (I') described in (i) above, and A nonionic copolymer with a copolymerizable nonionic unsaturated monomer (II), a cationic copolymer of the monomer (I ′) described in the above item (i) and an unsaturated monomer (III) having an amino group, and A cationic copolymer of the monomer (I ′) described in (i) above, the nonionic unsaturated monomer (II), and the amino group-containing unsaturated polymer (III), (i.
ii) Hoffmann reaction products or Mannich reaction products of the polymers and copolymers described in the above items (i) and (ii), or polymers obtained by further alkylating the reaction products to give a quaternary amination, (iv) A copolymer of the monomer (I ′) described in the above item (i) and an acrylic ester and a reaction product of an alkylene polyamine; (v) a monomer (I ′) described in the above item (i); Anionic copolymer with a polymerizable unsaturated anionic monomer (IV), and the above-mentioned monomer (I ′) and anionic monomer (I
V), and an anionic copolymer of a nonionic monomer (II), (vi) a copolymer of the monomer (I ′) and maleic anhydride or itaconic acid, (vii) the (i),
Anionic polymers, which are hydrolysates of the polymers and copolymers described in (v) and (vi), can be used.

Further, one specific example of the copolymer described in the above item (ii) is a nonionic or cationic polymer represented by the following general formula. (I ′) _l − (III) _m − (II) _n − where _l > 40 _m = 0 to 60 _n = 0 to 60 _l + _m + _n = 100 (I ′) is the same as the above item (i). The indicated monomers are shown as (I
I) represents a nonionic monomer copolymerizable with the monomer (I ′), and specific examples thereof include 2-hydroxy (meth)
Acrylate, diacetone acrylamide, methylol acrylamide, acryloylmorpholine, acrylonitrile, (meth) acrylic acid ester, styrene, and vinyl acetate.

[0029]

Embedded image

Examples of the Mannich reaction and Hoffmann reaction described in the above item (iii) are:

[0031]

[Chemical 4] There is.

Further, specific examples of the anionic copolymer described in the above item (v) include those represented by the following general formula. (I ′) _l − (IV) _o − (II) _p where (I ′) and (II) are as described above, and (IV)
Represents an unsaturated anionic monomer copolymerizable with the monomer (I ′). _l > 40 _o = 0 to 60 _p = 0 to 59 _l + _o + _p = 100

[0033]

Embedded image Is.

As the coating method in the method of the present invention, dipping, spraying, brush coating, roll coating, flow coating and the like are used. In order to suppress the stringing phenomenon during coating,
It is appropriate that the molecular weight of the polymer or copolymer (A) is 2,000,000 or less, preferably 1,000,000 or less. The concentration and viscosity of the coating solution are appropriately selected depending on the coating method used, the desired film thickness and the like. In order to increase the thermal efficiency and contribute to the corrosion resistance especially when used for a heat exchanger, the thickness of the coating film is about 0.1 μm or more and 10 μm or less, preferably 0.2 μm or more and 2 μm or less. Preferably.

The aluminum-containing metal compound may be degreased in advance and directly applied thereto, or it may be applied after chemical conversion treatment such as boehmite treatment or chromate treatment. However, in the case of direct coating, addition of chromic acid, dichromic acid and salts thereof is particularly effective. In the coating liquid, in addition to the above components, a rust preventive agent, a filler, a coloring agent, a surfactant, an antifoaming agent, a leveling agent, an antibacterial and antifungal agent, etc.
You may add in the range which does not impair the meaning of this application and film performance. As described above, water is used as the coating liquid solvent,
In order to accelerate drying and improve the condition of the coating film, alcohol,
It does not prevent the combined use of water-soluble solvents such as ketones and cellosolves.

The stability of the coating solution differs depending on its composition, but generally speaking, when a cationic polymer is used, its pH is preferably set to a neutral to acidic side. Its pH, if used
Is preferably maintained on the neutral to alkaline side. Further, in the method of the present invention, since a water-soluble compound of chromium, titanium, or aluminum is used as a crosslinking agent, the acidic side is generally preferred.

[0037]

According to the present invention, a coating film of a copolymer or a polymer crosslinked with a specific water-soluble crosslinking agent becomes insoluble in water and thus can be practically used as a coating film of fins made of an aluminum-containing metal. In addition to the improvement in hydrophilicity due to the use of polyacrylamide, it was possible to further improve the corrosion resistance. A coating film having such excellent properties is suitable as a surface coating for an aluminum-containing metal heat exchanger.

[0038]

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 the surface of the test solid, was measured using a FACE contact angle meter CA-P type (Kyowa Interface Chemistry). As the sample to be tested, an initial sample after processing and one week after immersion in running water were used. Corrosion resistance: Based on the salt spray test method JIS Z-2371, the spray test time until the white rust area on the test sample reached 5% was measured. - flowing water Stability: After 8H _R immersed in running water at room temperature test sample, the process of drying 16H _R, 80 ° C. and 1 cycle,
The contact angle with water after 5 cycles of this was measured.

Example 1 A mixed aqueous solution containing 40 g / liter of polyacrylamide having a molecular weight of about 100,000, 10 g / liter of aluminum sulfate, Elastron A-42, and 10 g / liter of Daiichi Kogyo Seiyaku Co., Ltd. (solid content conversion) was defatted. Aluminum plate after post phosphoric acid chromate treatment (JIS standard A1100,
The amount of Cr deposited was 70 mg / cm ² ) and dried in an electric dryer at 180 ° C. for 3 minutes. The average film thickness of the obtained coating film was 0.
It was 5μ. The processing conditions are shown in Table 1 and the test results are shown in Table 2.

Examples 2 to 4 The same operation as in Example 1 was carried out by changing the conditions as shown in Table 1. The test results are shown in Table 2.

[0041]

[Table 1]

[0042]

[Table 2]

Continuation of the front page (51) Int.Cl. ⁶ Identification number Reference number within the agency FI Technical display area F28F 1/32 F28F 1/32 H 13/18 13/18 19/04 19/04 (72) Inventor Ai Nishihara Nihonbashi 1-15-1 Nihonbashi Parkizing Co., Ltd., Chuo-ku, Tokyo (72) Inventor Hiroshi Okita 1-15-1 Nihonbashi Nihonbashi Chuo-ku, Tokyo Nihon Parkerizing Co., Ltd.

Claims (1)

(57) [Claims] 1. A compound represented by the general formula (I): The water-soluble polymer or copolymer (A) obtained by polymerization or copolymerization of the monomer represented by and the water-soluble polymer or copolymer (A) can be cross-linked to make them insoluble in water. The aluminum-containing metal material is characterized in that a mixed aqueous solution with a crosslinking agent (B) containing at least one of water-soluble compounds of chromium, titanium and aluminum is applied to the surface of the aluminum-containing metal material and dried and crosslinked. Hydrophilization treatment method.