JPH06248232A - Treating material for substrate of alkali silicate hydrophilic coating film for heat exchanger - Google Patents

Abstract

PURPOSE:To obtain a substrate treating material useful for a hydrophilic coating film of a heat exchanger made of metal, excellent in adhesiveness, corrosion resistance, etc., and consisting of a specific polymer component, a cross-linking agent component and an acid component. CONSTITUTION:The treating material consists of (A) a polymer component consisting of at least one compound selected from homopolymers containing a monomer of the formula (R1 is H or methyl; R2 and R3 are H, 1-4C alkyl, benzyl or hydroxyalkyl) (e.g. acrylamide, etc.) and copolymers and (B) a cross- linking agent component consisting of a metal compound (e.g. chromic acid, zirconyl nitrate, etc.) which cross-links the component A to make it water insoluble, and an acidic component containing more than one compound selected from an inorganic acid and an organic acid having an acid group containing phosphorus (e.g. ortho-phosphoric acid, meta-phosphoric acid, etc.), an ammonium salt of the acid and an acidic salt of the acid. here, the content of each component is preferably 20-80(wt.) A, 5-10% B and 10-80% C based on the total weight.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface treating agent for an alkali silicate hydrophilic film for a heat exchanger. More specifically, the present invention relates to an undercoating agent used for forming an underlayer when an alkali silicate hydrophilic film is formed on the surface of a fin material for a heat exchanger made of an aluminum metal material. It is a thing. In the specification of the present application, the aluminum metal material includes an aluminum material and an aluminum alloy (for example, aluminum-manganese alloy, aluminum-magnesium alloy) material.

[0002]

2. Description of the Related Art In a hydrophilic treatment method for a fin material for a heat exchanger made of an aluminum metal material, a conventional method using an alkali silicate is disclosed in JP-A-50-38645. Method of applying alkali silicate to aluminum surface that has been subjected to immersion treatment using a solution of alkali metal chromate ”, JP-A-54-
"Method of treating an aluminum heat exchanger with an aqueous solution containing an alkali metal silicate and then treating it with an aqueous solution containing an alkaline earth metal compound" disclosed in Japanese Patent No. 57264.
Japanese Patent Laid-Open No. 56-27895 discloses a method of treating an aluminum material with a treatment liquid containing a salt of an alkali metal or an alkaline earth metal, and then treating with a silicate, tannic acid or a salt thereof. JP-A-59-20
2398, "A method of forming a chemical coating on the surface of an aluminum plate and forming a hydrophilic coating layer composed of a hydrophilic inorganic material such as alkali silicate and a specific hydrophilic organic material on the surface" JP-A-60-10115
Japanese Patent Laid-Open No. 6-235477, "Aluminum hydrophilic film forming agent characterized by containing an alkali silicate, a low molecular weight organic compound having a carbonyl group, and a water-soluble organic compound". "A hydrophilic film-forming agent containing an alkali silicate, an inorganic curing agent and a water-soluble organic polymer compound, and JP-A-62-27"
No. 2099, "A heat exchanger having a film containing a compound having a silanol group such as an alkali silicate and polyvinylpyrrolidone" is disclosed.

In forming a hydrophilic film using an alkali silicate as described above, the technique for forming the base is as follows:
It has not been established yet, and the above hydrophilic film is formed without a base, or for forming a base layer, formation of a chemical conversion film by chromate chromate or phosphoric acid chromate, or boehmite method Formation of such an oxide film was carried out, and all of them formed an inorganic base film.

In the method of forming a hydrophilic film on an aluminum metal material with an alkali silicate, as a method for forming the underlying film, there is disclosed a method of using an oxide film by hypohalite treatment in JP-A-58-106397. And JP-A-59-205596, "Method of coating with organic polymer resin". Further, although the kind of the hydrophilic film is not specified, as a method of treating the surface of the aluminum fin material, Japanese Patent Laid-Open No. 247866/1987 describes "A synthetic resin capable of forming a foundation film and a chelate with the synthetic resin. A method of pretreating a fin material with a treatment agent containing a metal compound such as a metal oxide has been proposed.

In the case of treating the surface of an aluminum metal material with a hydrophilic treatment agent containing an alkali silicate, if a conventionally used inorganic chemical conversion treatment such as chromate is applied to the base treatment, it has excellent corrosion resistance and hydrophilicity. And the adhesiveness between the base film and the hydrophilic film can be obtained. However,
When manufacturing a heat exchanger by press-molding a fin material that has been pretreated with a treatment agent that forms these inorganic-based coatings, the base coating is hard, so the mold tends to wear, and drawless When subjected to severe ironing such as processing, there were drawbacks such as cracking of the film itself and easy occurrence of seizure. Further, in the chemical conversion treatment, a water washing step is required after the treatment, and in the chromium-based chemical conversion treatment, it is necessary to carry out wastewater treatment of hexavalent chromium, so that there is a drawback that productivity is deteriorated.

According to the method disclosed in JP-A-58-106397, the corrosion resistance and the adhesion are not sufficient. Further, the above-mentioned JP-A-59
In the case of using an undercoating film containing an organic polymer resin as a main component, as disclosed in JP-A-205596 and JP-A-62-247866, the adhesion to the alkali silicate film (particularly water-resistant adhesion) is insufficient, When using solvent washing process or volatile press oil after press working, after press oil is removed by heating, it is exposed to high temperature and high humidity environment like the process of washing excess press oil with high pressure steam, and pressing When an external force is applied to the coating during processing, the coating may fall off or peel off, causing problems such as poor appearance of the heat exchanger and deterioration of hydrophilicity. Further, there is a problem that the coating film that has fallen off causes wear of the press die.

The inventors of the present invention have previously described a hydrophilic film using an acrylamide polymer in Japanese Patent Laid-Open No. 63-171.
No. 683 and JP-A-63-171684. As one aspect of these methods, a mixed aqueous solution of an acrylamide polymer and a water-soluble cross-linking agent that renders it water-insoluble is applied to the surface of the aluminum metal material, and this is dried and cross-linked to form a film, and then water is further added. There is a method of forming an inorganic hydrophilic film such as glass. As the water-soluble cross-linking agent, when using an organic cross-linking agent such as blocked isocyanate prepolymer, trimethylolmelamine, or triethylene glycol glycidyl ether, the corrosion resistance is not so high, in order to obtain sufficient corrosion resistance such as chromate. It was necessary to use the base treatment together. When using a metal cross-linking agent such as chromic anhydride, corrosion resistance is excellent even without using a base treatment such as chromate, but the water-resistant adhesion with a water glass hydrophilic treatment agent is insufficient, In particular, in a high humidity environment, when an external force is applied to the film, the film is likely to peel off.

No. 1 of the example (Table 1) of JP-A-63-171683. 1, 5, 6, 7, 12 and JP-A-63
No. 171684 Example (Table 1). When the organic cross-linking agent as shown in 2 is used, the corrosion resistance is insufficient and it is necessary to preliminarily subject the surface of the aluminum metal material to a surface treatment such as chromate. Also, JP-A-63-17
No. 1683 Example (Table 1). Nos. 1, 5, 7 and No. 1 in the examples (Table 1) of JP-A-63-171684. Phosphoric acid or a phosphate salt is used for 2, which is used to prevent thickening or gelation of the used organic cross-linking agent or mixed treatment liquid. When used together with the organic cross-linking agent, the effect of improving the adhesiveness with the alkali silicate-based hydrophilic treatment film of the top coat was not observed.

[0009]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned problems of the prior art and has an excellent adhesion to a hydrophilic film containing an alkali silicate and promotes the formation of a denser hydrophilic film. Has corrosion resistance, press molding resistance, chemical resistance,
It is intended to provide an undercoating agent for an alkali silicate hydrophilic film for a heat exchanger made of an aluminum metal material, which is excellent in solvent resistance.

[0010]

Means for Solving the Problems Regarding the organic film using the acrylamide-based water-soluble polymer of the above-mentioned prior invention, the inventors of the present invention do not use the hydrophilic film as a hydrophilic film but an alkali silicate-based hydrophilic film as a base treatment film. And a specific acrylamide water-soluble polymer and a metal compound capable of cross-linking it to make it water-insoluble, and an inorganic acid having an acid group containing phosphorus, an organic acid, an ammonium salt or an acid salt thereof. By applying the mixed aqueous solution to an aluminum metal material and performing cross-linking drying, a base film having excellent corrosion resistance and excellent adhesion to the alkali silicate hydrophilic film was successfully obtained.

That is, the base treatment agent for an alkali silicate hydrophilic film for a heat exchanger according to the present invention comprises the following components: (A) the following general formula (I):

[Chemical 2] [Wherein, in the above formula (I), R ¹ represents a hydrogen atom or a methyl group, and R ² and R ³ are each independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, or benzyl. A group or a hydroxyalkyl group] as a polymerization component, a polymer component comprising at least one selected from homopolymers and copolymers, (B) the polymer of the polymer component (A) is crosslinked. And (C) inorganic acid and organic acid having a phosphorus-containing acid group, and ammonium salt and acidic salt of the inorganic acid and organic acid. Acidic component containing at least one selected from the above.

The polymer component (A) used in the present invention is
One or more selected from homopolymers and copolymers containing the monomer of formula (I) as a polymerization component. In the above formula (I), the hydroxyalkyl group represented by R ² or R ³ preferably has 1 to 4 carbon atoms, and is selected from, for example, a hydroxymethyl group and a hydroxyethyl group. Homopolymers and copolymers include homopolymers and copolymers such as acrylamide, methacrylamide, N-methyl acrylamide, N-dimethyl acrylamide, N-methylol acrylamide and their Hoffmann reaction products and Mannich reaction products.

The comonomer that is copolymerized with the monomer of formula (I) can be selected from anionic ethylenically unsaturated monomers, cationic ethylenically unsaturated monomers, nonionic ethylenically unsaturated monomers and the like.

Examples of the anionic unsaturated monomer include acrylic acid, methacrylic acid, itaconic acid, maleic acid, vinyl sulfonic acid, allyl sulfonic acid, sulfoethyl acrylate, sulfoethyl methacrylate, styrene sulfonic acid and 2-acrylamide-2. -A monomer having an anionic group such as a carboxyl group, a sulfonic acid group, or a phosphonic acid group in the molecule such as methylpropanesulfonic acid and vinylphosphonic acid, or a salt thereof can be used.

Examples of the cationic unsaturated monomer are ethyleneimine, aminoalkyl acrylate, aminoalkyl methacrylate, aminoalkyl acrylamide, N-methylaminoalkyl acrylate, N-methylaminoalkyl methacrylate, N-methylaminoalkylacrylamide, N, N-. Dimethylaminoalkyl acrylate, N, N-dimethylaminoalkylmethacrylate, N, N-dimethylaminoalkylacrylamide, N, N-diallylamine, N, N-dialkyl-N, and N-diallylammonium salts are used in the molecule. Monomers having a cationic group such as primary amine, secondary amine, tertiary amine, and quaternary ammonium salt can be used.

The nonionic unsaturated monomer is 2
-Acrylic ester such as hydroxyalkyl acrylate, methacrylic ester such as 2-hydroxyalkyl methacrylate, allyl alcohol, vinyl acetate, acroylmorpholine, acrylonitrile, and styrene can be used.

There are no particular restrictions on the molecular weight and the degree of polymerization of the polymer of the polymer component (A) used in the present invention, but it is generally preferable to have an average molecular weight of 5,000 to 1,000,000. .

The crosslinking agent component (B) used in the present invention is
It is composed of at least one metal compound capable of crosslinking the polymer in the polymer component (A) and making it insoluble in water. As such a crosslinking agent metal compound, 4
Metal compounds having a coordination number or more, such as Cr, Ti,
Zr and Al compounds can be used. Among these metal compounds, particularly highly water-soluble compounds, namely chromic acid, dichromic acid, and salts thereof, chromium diphosphate, chromium fluoride, chromium nitrate, chromium acetate, diisopropoxytitanium biscetylacetone, and lactic acid. Reaction products with titanium alkoxide, zirconyl nitrate, zirconyl acetate, zirconyl ammonium carbonate, zirconium hydrofluoric acid and its salts, and aluminum nitrate are useful.

The acidic component (C) used in the present invention comprises at least one selected from inorganic and organic acids having phosphorus-containing acid groups, ammonium salts and acidic salts of the inorganic and organic acids. . Examples of the inorganic acid and organic acid having a phosphorus-containing acid group include condensed phosphoric acid such as orthophosphoric acid, metaphosphoric acid, pyrophosphoric acid and tripolyphosphoric acid, phosphorous acid, hypophosphorous acid, phytic acid, 1-hydroxyethylidene-1, Examples thereof include 1-diphosphonic acid and aminotrimethylenephosphonic acid. Further, ammonium salts and acid salts of these acids can be used.

In the surface treatment agent of the present invention, based on the total solid weight of the components (A), (B) and (C),
The content of the polymer component (A) is preferably 3 to 90% by weight, more preferably 20 to 80% by weight, and the content of the crosslinking agent component (B) is 2 to 70% by weight. %, More preferably 5 to 50% by weight, and further, the content of the acidic component (C) is 5
Is preferably 95% by weight to 10% by weight to 80% by weight
Is preferred.

The surface treatment agent of the present invention is applied to the surface of a metal material such as an aluminum metal material. This coating method is not particularly limited, and an appropriate coating method such as a dipping method, a spraying method, a brush method, a roll method, and a flow coating method can be used. There is no restriction on the concentration and viscosity of the base treatment agent, and it can be appropriately set according to the coating method used, the thickness of the coating film, and the like. There is no particular limitation on the thickness of the undercoat, but it is generally preferably 0.02 μm to 10 μm.

[0022]

The undercoating film formed by applying the undercoating agent of the present invention has excellent adhesion to the hydrophilic film containing alkali silicate applied on the undercoating film, and forms a more dense hydrophilic film. And has excellent corrosion resistance, press-molding resistance, chemical resistance, and solvent resistance.

The inventors of the present invention have conducted the chemical analysis of the undercoating film formed by applying the undercoating agent, and as a result, consider the action and effect of the undercoating agent as follows. When the base treatment agent of the present invention is applied to a degreased and washed metal material such as aluminum or an aluminum alloy material and then subjected to a drying step by heating, the polymer component (A) is a cross-linking agent component. (B) Reacts with a part of (metal compound) to form a highly crosslinked network structure.

A part of the metal compound of the crosslinking agent component (B) is
It is oriented on the surface of the metallic material or reacts with it to form a passive layer. The excellent corrosion resistance, chemical resistance, and solvent resistance of the undercoating film of the present invention are considered to be derived from the above film structure. It is considered that the undercoating film of the present invention is excellent in press workability because the undercoating film has excellent flexibility as compared with the inorganic chemical conversion coating film such as chromate due to the polymer component (A). The acidic component (C) consisting of an inorganic acid having a phosphorus-containing acid group, or an organic acid or a salt thereof easily forms an insoluble salt with the metal compound of the crosslinking agent component (B). Ingredient (B)
It is believed that the acid groups are bonded to a part of the base film to be fixed in the base film, but some of the acid groups remain, and these are oriented to the surface of the base film to activate this surface.

When the hydrophilic treatment liquid containing an alkali silicate is applied to the undercoat formed as described above, the alkali metal ions in the alkali silicate are fixed in the undercoat and the Acidic component present on the surface (C)
It is considered that the compound is attracted to the acid group of the compound to form a salt, which lowers the pH of the hydrophilic treatment liquid, accelerates gelation of silicic acid, and condensation reaction during heating and drying. By this action, the hydrophilic film on the undercoat film is made more compact. It is considered that the excellent adhesion between the undercoating film and the hydrophilic film of the present invention is due to the reaction between the silicate ion and the metal compound of the crosslinking agent component (B) at the interface between the coating films.

As described above, the undercoating film formed by applying the undercoating agent of the present invention has a particularly excellent undercoating function when a hydrophilic film containing an alkali silicate is formed thereon. Although it is effective, it also exerts an excellent function when a hydrophilic film containing no alkali silicate, for example, an organic hydrophilic film having a hydrophilic organic polymer as a main component is used as an upper layer. Therefore, it goes without saying that the base treatment agent of the present invention can also be applied as a base treatment agent for an organic hydrophilic film.

[0027]

The present invention will be further described with reference to the following examples. Example 1 Alkaline degreasing agent (trademark: Fine Cleaner 315,
An aluminum plate (A1100H24 material, thickness: 0.11 mm) was degreased and washed for 60 seconds by using Nippon Parkerizing Co., Ltd. at a concentration of 30 g / liter, washed with water, and drained and dried at 80 ° C. for 60 seconds. did. The aluminum plate, aqueous undercoating liquid of the following composition: INGREDIENT AMOUNT acrylamide (AAM) homopolymer 33.3 g / liter (average molecular weight: about 800,000) of chromic anhydride 3.3 g / l chromium fluoride trihydrate 6 0.7 g / liter orthophosphoric acid 16.7 g / liter was applied using a bar coder and dried at 220 ° C. for about 20 seconds to form an undercoat film having a thickness of about 0.3 μm.

[0028] onto the primer coating, a hydrophilic coating aqueous coating solution having the following composition: INGREDIENT AMOUNT No. 3 sodium silicate (manufactured by Nippon Chemical Industrial Co.) 25 g / l (solids) acrylamide (AAM) and acrylic acid 25 g / L Copolymer with sodium (AANa) (AAM / AANa molar ratio = 50:50, average molecular weight: about 100,000) Glyoxal 10 g / l was applied, and this was heated and dried at 200 ° C for about 20 seconds,
A hydrophilic film having a dry film thickness of 0.3 μm was formed.

Example 2 The same treatment operation as in Example 1 was carried out to form a base film and a hydrophilic film. However, pyrophosphoric acid was used instead of orthophosphoric acid in the base treatment liquid.

Example 3 The same treatment operation as in Example 1 was carried out to form a base film and a hydrophilic film. However, phytic acid was used instead of orthophosphoric acid in the base treatment liquid.

Comparative Example 1 The same treatment operation as in Example 1 was performed to form a base film and a hydrophilic film. However, orthophosphoric acid was not used in the base treatment liquid.

Comparative Example 2 The same treatment operation as in Example 1 was carried out to form a base film and a hydrophilic film. However, chromic anhydride and chromium trifluoride trihydrate were not used in the base treatment liquid.

Example 4 The same processing operation as in Example 1 was carried out except for the following matters. (1) a copolymer of composition Ingredient of the aqueous undercoating liquid acrylamide and (AAM) 2-acrylamide 120 g / liter 2-methylpropanesulfonic sodium sulfonate (AMPS) (AAM / AMPS molar ratio = 60: 40, Average molecular weight: about 75,000) Chromium nitrate 45 g / liter Tripolyphosphoric acid 35 g / liter Drying: 220 ° C., about 20 seconds Thickness of undercoating: about 1 μm

[0034] (2) hydrophilic film aqueous coating solution Ingredient Quantity alkali silicate-containing treatment solution 200 g / l (Trademark: parentheses -4534, Nippon Parkerizing Co., Ltd.) Deionized water remainder portion coating method: dipping method Drying: 180 ℃, about 60 seconds Hydrophilic coating thickness: 0.5μm

Comparative Example 3 The same treatment operation as in Example 4 was carried out to form a base film and a hydrophilic film. However, nitric acid was used instead of tripolyphosphoric acid in the base treatment liquid.

Example 5 An undercoat and a hydrophilic film were formed by performing the same treatment operation as in Example 1 except for the following matters. (1) copolymerizing polymers of the aqueous undercoating liquid Ingredient Quantity acrylamide (AAM) and dimethylaminoethyl 50 g / liter methacrylate quaternized (DAM) (AAM / DAM molar ratio = 60: 40, average molecular weight: about 950,000 ) Chromic anhydride 5 g / liter Ammonium zirconium carbonate 15 g / liter (solid content) Ammonium aminotrimethylphosphonate 30 g / liter Coating method: Barcorder method Drying: 220 ° C., about 20 seconds Thickness of base film: 0.5 μm

[0037] (2) a hydrophilic film-forming aqueous coating solution Ingredient Quantity No. 3 sodium silicate (manufactured by Nippon Chemical Industrial Co.) 30 g / l (solids) of sodium polyacrylate (average molecular weight: about 100,000) 30 g / l Coating method: Bar coder method Drying: 200 ° C., about 20 seconds Thickness of hydrophilic film: 0.3 μm

Comparative Example 4 The same treatment operation as in Example 5 was carried out to form a base film and a hydrophilic film. However, ammonium trimethylphosphonate was not used in the base treatment liquid.

Comparative Example 5 A base film and a hydrophilic film were formed by performing the same treatment operation as in Example 1 except for the following matters. (1) an aqueous undercoating liquid Ingredient Quantity polyacrylamide (average molecular weight: about 800,000) 40 g / liter water-soluble blocked isocyanate prepolymer 10 g / l (Trademark: Elastoron A-42, manufactured by Daiichi Kogyo Co., Ltd.) (solid content ) Orthophosphoric acid 30 g / liter Coating method: Barcoder method Drying: 180 ° C., about 3 minutes Thickness of undercoating: 0.5 μm

[0040] (2) a hydrophilic film-forming aqueous coating solution Ingredient Quantity No. 3 sodium silicate (manufactured by Nippon Chemical Industrial Co.) 50 g / l (solids) coating method: bar coater method Drying: 160 ° C., for about 30 seconds hydrophilic Film thickness: 0.3 μm

Test Evaluation The processed plate samples produced according to the contents shown in the above Examples and Comparative Examples were tested and evaluated according to the following method. (1) Corrosion resistance Salt spray test method JIS-Z-23
Time until white rust occurrence area based on 71 reaches 5%

(2) Water-proof adhesion 0.2 ml on the sample surface
Deionized water was added dropwise and lightly rubbed with Kimwipe (trade name: Wiper S-200, manufactured by Tojo Kimberley Co., Ltd.) 5 times, and then the surface was observed. The evaluation was based on the following criteria. No peeling --- ○ Partially peeling ----- Almost all peeling --- ×

(3) Resistance to boiling water The sample was immersed in boiling deionized water for 5 minutes, and the surface of the sample was observed by rubbing the surface of the sample lightly 5 times with the Kimwipe. The evaluation was based on the following criteria. No peeling --- ○ Partially peeling ----- Almost all peeling --- ×

The results of the above test evaluations are shown in Table 1.

[Table 1]

As is clear from Table 1, in Comparative Examples 1, 3 and 4, the products obtained had good corrosion resistance, but the base treatment liquid contained the specific acidic component (C) of the present invention.
Therefore, the obtained product was poor in water-resistant adhesion and boiling water resistance. In Comparative Example 2, the undercoating liquid or the specific crosslinking agent component (B) of the present invention was used.
In Comparative Example 5, since the (metal compound) was not contained, and the undercoating liquid contained the organic cross-linking agent instead of the specific cross-linking agent component (B) (metal compound) of the present invention, The obtained product had poor corrosion resistance, water-resistant adhesion, and boiling water resistance. On the other hand, the products of Examples 1 to 5 according to the present invention all had good corrosion resistance, water-resistant adhesion and boiling water resistance, and were excellent in practical use.

[0046]

The undercoating film formed by coating the undercoating agent of the present invention has excellent adhesion to the hydrophilic film containing an alkali silicate applied on the undercoating film and exhibits excellent corrosion resistance. Is. Therefore, the base treatment agent of the present invention,
It has practically excellent performance with respect to a hydrophilic coating of a heat exchanger made of metal, for example, aluminum metal material.

Claims (1)

[Claims] 1. The following components: (A) the following general formula (I): [Wherein, in the above formula (I), R ¹ represents a hydrogen atom or a methyl group, and R ² and R ³ are each independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, or benzyl. Group or a hydroxyalkyl group] as a polymerization component, a polymer component comprising at least one selected from homopolymers and copolymers, (B) a polymer of the polymer component (A) is cross-linked. And a crosslinker component consisting of at least one metal compound that makes it insoluble in water, and (C) an inorganic acid and an organic acid having a phosphorus-containing acid group, and an ammonium salt and an acid salt of the inorganic acid and the organic acid. An alkaline silicate-based hydrophilic coating surface-treating agent for a heat exchanger, comprising an acidic component containing at least one selected from the above.