JPH0376827B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD This invention relates to a fin material for a heat exchanger. In this specification, aluminum includes aluminum and aluminum alloys. 2. Description of the Related Art In general, in a heat exchanger, particularly an evaporator of an air conditioner, water droplets adhere to the surface of the fin because the surface temperature of the fin is below the dew point of the atmosphere. Due to the adhesion of such water droplets, ventilation resistance increases, the air volume decreases, and heat exchange efficiency decreases. This becomes especially noticeable when the fin pitch is narrowed to improve the performance and downsize the heat exchanger. Heat exchange efficiency is greatly influenced by the ability of water to get wet on the fin surface, and if the fin surface has good wettability, attached water will be less likely to form droplets, which will reduce ventilation resistance and increase air volume. Heat exchange efficiency increases. In order to improve the wettability of the fin surface, a method has been proposed in which a water glass (alkali silicate) film is formed on the surface of an aluminum fin (see Japanese Patent Publication No. 48177/1983). Problems to be Solved by the Invention However, according to this conventional method, although the initial hydrophilicity of the fins is improved, this hydrophilicity deteriorates early and has a problem of poor sustainability. In addition, since the water glass film is hard, especially when this film is formed on the fin material, cracks may occur at the bent part of the fin during the burring process during fin molding, resulting in poor moldability and poor moldability. There was a problem that it was easily worn out. In order to solve these problems, the present applicant previously proposed a hydrophilic film-forming agent for aluminum containing an alkali silicate and a low-molecular organic compound having a carbonyl group (Japanese Patent Application No. 58-209508 (Refer to the corresponding Japanese Patent Publication No. 2-42389). According to the previously proposed hydrophilic film forming agent, a film having excellent hydrophilicity and durability can be formed on the surface of the fin material. From the viewpoint of affinity with the hydrophilic coating, it is also desirable to provide a hydrophilic coating. Here, if a chemical film such as a chromate film is provided as a film constituting the base layer on the hydrophilic film constituting the surface layer, this is relatively hard, so the fin material as a whole is pushed to its limit. This results in a problem of thinning of the fin, and cracks occur at the bent part during the burring process during fin molding, resulting in poor moldability and poor mold abrasion. Ta. Furthermore, the chromate film has poor alkali resistance, so it cannot be used in applications that require alkali resistance, such as commercial air conditioners that are cleaned with alkaline cleaners and installed on concrete walls. What kind of base film should be provided for the above-mentioned hydrophilic film constituting the layer has been an extremely important issue. This invention was made in view of the above points,
The first coating is made of a water-soluble synthetic resin that has excellent corrosion resistance and is relatively soft. By forming a second film composed of a component that stabilizes the silicate film, further improves hydrophilicity, and gives flexibility to the film, the limit ironing rate of the fin material as a whole can be improved, and the fin material can be improved. It can be made thinner, has excellent formability, can increase the height of the bent part during burring, does not cause cracks, and can be easily molded into fins. The purpose of the present invention is to provide a fin material for a heat exchanger that exhibits very little wear on molds and has excellent alkali resistance. Means for Solving the Problems In order to achieve the above-mentioned object, the present invention has a water-soluble acrylic resin, a water-soluble polyurethane resin and a copolymer thereof, a water-soluble alkyd resin, a water-soluble A first film made of at least one water-soluble synthetic resin selected from the group consisting of polyester resins and water-soluble amino resins is provided, and on the surface of this first film, alkali silicate (A) and Abstract: A fin material for heat exchangers is provided with a second coating mainly composed of a low-molecular organic compound (B) having a carbonyl group selected from the group consisting of aldehydes, esters, and amides. It is said that The water-soluble synthetic resins constituting the first film include water-soluble acrylic resins, water-soluble polyurethane resins and their copolymers, water-soluble alkyd resins,
At least one of a water-soluble polyester resin and a water-soluble amino resin is used. Here, the amino resin refers to a resin obtained by a condensation reaction between a compound containing an amino group and an aldehyde, and specifically includes melamine resin, urea resin, aniline amino resin, and the like. The water-soluble synthetic resins include those that completely dissolve in water to form a solution and those that partially dissolve in water to form a dispersed solution. The process of forming a first film made of a water-soluble synthetic resin on the surface of a plate-shaped aluminum material is performed by dipping, spraying, or coating using an aqueous solution containing the water-soluble synthetic resin. The first film thus formed has hydrophilicity and excellent corrosion resistance. The thickness of the first film made of such a water-soluble synthetic resin is preferably 1 to 50 μm, for example. If the thickness of the first film is less than 1 .mu.m, there will be a problem in corrosion resistance, and if it exceeds 50 .mu.m, heat conduction of the aluminum fin material will be inhibited and moldability will deteriorate. Next, the alkali silicate (A) contained in the second film constitutes the main component for imparting hydrophilicity to the fin material, and is SiO ₂ /M ₂ O (in the formula, M is lithium, It is necessary to use a metal having a ratio of 1 or more (meaning an alkali metal such as sodium or potassium). In particular, SiO ₂ /M ₂ O is 2
Preference is given to using alkali silicates of 5 to 5.
Here, when the ratio of SiO ₂ /M ₂ O is less than 1, there is less SiO ₂ than the alkaline component, so
The corrosion effect of aluminum by alkal components increases. Furthermore, the above-mentioned low-molecular organic compound (B) is a low-molecular organic compound having a carbonyl group (>C=O) in the molecule, which stabilizes the film formed by the alkali silicate (A) and makes it more It improves hydrophilicity and gives flexibility to the film. Specific examples of such low molecular weight organic compounds (B) include aldehydes, esters, and amides. Here, as the aldehydes, formaldehyde, acetaldehyde, glyoxal, malondialdehyde, succindialdehyde, glutardialdehyde, furfuraldialdehyde, etc. are used. Examples of esters include fatty acid esters of monohydric alcohols such as methyl formate, ethyl acetate, methyl acetate, butyl acetate, amyl acetate, and methyl propionate, as well as ethylene glycol diacetate, glycerine triacetate, and ethylene glycol dipropionate. Fatty acid esters of polyhydric alcohols such as esters, intramolecular esters such as γ-butyrolactone and ε-caprolactone,
Also, ethylene glycol monoformate, ethylene glycol monoacetate, ethylene glycol monopropionate, glycerin monoformate, glycerin monoacetate,
Glycerin monopropionate, glycerin diformate, glycerin diacetate,
Polyhydric alcohol partial esters such as sorbitol monoformate, sorbitol monoacetate, and glycose acid monoacetate, monohydric alcohol esters of polybasic acids such as dimethyl succinate and dimethyl maleate, and ethylene carbonate, propylene carbonate, Cyclic carbonates such as glycerin carbonate are used. Further, as the amides, formamide, dimethylformamide, acetamide, dimethylacetamide, propionamide, butyramide, acrylamide, malondiamide, pyrrolidone, caprolatam, and the like are used. Among the low-molecular-weight organic compounds (B), water-soluble compounds are preferably used in order to perform uniform treatment, and aldehydes and esters are particularly preferably used. Furthermore, it is desirable to use glyoxal because it forms a highly hydrophilic film. Next, a water-soluble organic polymer Compound (C) may also be added. Specifically, such water-soluble organic polymer compounds (C) include polysaccharide-based natural polymers, water-soluble protein-based natural polymers, anionic, nonionic, or cationic addition-polymerized water-soluble synthetic polymers. , and polycondensation water-soluble polymers. Here, as the polysaccharide natural polymer, soluble starch, carboxymethyl cellulose, hydroxyethyl cellulose, guar gum, gum tragacanth, xanthan gum, sodium alginate, etc. are used. Gelatin or the like is used as the water-soluble protein-based natural polymer. Examples of anionic or nonionic addition polymer water-soluble polymers include polyacrylic acid, sodium polyacrylate, polyacrylamide, partial hydrolysates thereof, polyvinyl alcohol, polyhydroxyethyl acrylate, polyvinylpyrrolidone, and acrylic acid copolymers. , maleic acid copolymers and their alkali metal, organic amine and ammonium salts. Furthermore, water-soluble synthetic polymers modified by carboxymethylation or sulfonation of the above-mentioned addition polymerized water-soluble synthetic polymers can also be used. Examples of cationic addition-polymerized water-soluble synthetic polymers include polyethyleneimine, Mannitz-modified compounds of polyacrylamide, diacryldimethylaluminum chloride, polyvinylimidazoline,
Polyalkylamino (meth)acrylates such as dimethylaminoethyl acrylate polymers are used. Polycondensation water-soluble synthetic polymers include polyalkylene polyols such as polyoxyethylene glycol and polyoxyethylene oxypropylene glycol, polycondensates of epichlorohydrin and polyamines such as ethylenediamine or hexamethyldiamine, and water-soluble polyethers and polyesters. Water-soluble polyurethane resin, polyhydroxymethylurea resin, polyhydroxymethylmelamine resin, etc., which are polycondensed isocyanates, are used. Among the water-soluble organic polymer compounds (C), it is preferable to use an anionic addition-polymerized water-soluble polymer having a carboxylic acid or a carboxylic acid group, particularly polyacrylic acid, acrylic acid copolymer, maleic acid Preference is given to using acid copolymers and their alkali metal salts. Here, the acrylic acid copolymer and maleic acid copolymer include copolymers of acrylic acid and maleic acid, as well as acrylic acid or maleic acid, methacrylic acid, methyl methacrylate, ethyl methacrylate,
Preference is given to using copolymers with hydroxyethyl methacrylate, itaconic acid, vinylsulfonic acid and acrylamide. In the above, the blending ratio of the alkali silicate (A), the low molecular organic compound having a carbonyl group (B), and the water-soluble organic polymer compound (C) is as follows. First, in the case of (A)+(B), the low molecular weight organic compound (B) having a carbonyl group is blended in a ratio of 0.15 to 5 parts by weight per 1 part by weight of the alkali silicate (A). Next, in the case of (A) + (B) + (C), 0.1 to 5 parts by weight of a low molecular weight organic compound (B) having a carbonyl group is added to 1 part by weight of the alkali silicate (A). and a water-soluble organic polymer compound in a proportion of 0.01 to 5 parts by weight. In the above, if the amount of alkali silicate (A) in the hydrophilic film forming agent is small, a sufficient hydrophilic film will not be formed on the surface of aluminum. On the other hand, if the amount is too large, the film becomes too hard, resulting in poor moldability and mold wear resistance. Also, low-molecular organic compounds (B) having a carbonyl group
If it is less than 0.1 part by weight per 1 part by weight of the alkali silicate (A), the effect of adding the low-molecular organic compound (B) will not be apparent, and if it exceeds 5 parts by weight, the alkali silicate will be relatively weak. Since the amount of salt (A) decreases, sufficient hydrophilicity is not exhibited. The water-soluble organic polymer compound (C) is an alkali silicate
If the amount is less than 0.01 part by weight relative to 1 part by weight of (A), the effect of adding the polymer compound (C) will not appear, and if it exceeds 5 parts by weight, the formed film will be easily eluted into water. The sustained effect of hydrophilicity is reduced. Here, the alkali silicate (A), the low-molecular organic compound having a carbonyl group (B), and the water-soluble polymer compound (C) are used after being diluted with water. The dilution ratio must be determined in consideration of the hydrophilicity, film thickness, and workability of the film. After forming the first film on the surface of the plate-shaped aluminum material, in order to treat it with an aqueous solution of the above mixture, it may be applied by spraying or brushing, or the aluminum may be immersed in the aqueous solution. The fin material after being treated with an aqueous solution is heated at 50 to 200℃.
The hydrophilic second film is coated on the surface of the first film by heating and drying, preferably at a temperature of 150 to 180°C for a period of 30 seconds to 30 minutes.
Forms a film. Here, if the heating drying temperature is less than 50°C, the composition will not form a film sufficiently, and if it exceeds 200°C,
Further heating has no effect. If the heating drying time is less than 30 seconds, the composition will not form a film sufficiently, and if it exceeds 30 minutes, productivity will decrease. When the heating drying temperature is as high as 160 to 200℃,
The drying time may be as short as 30 seconds to 1 minute, but if the temperature is low, it may be necessary to increase the drying time.
If heat drying is insufficient, the composition will not form a film sufficiently. In addition, the hydrophilic second film has a surface of 0.1
It is formed at a rate of ~10 g/m ² , preferably 0.5-3 g/m ² . Here, if the second film is 0.1 g/m ² or more, the initial hydrophilicity is good, but in order to maintain even better hydrophilicity, it is necessary to form a second film with a thickness of 0.5 g/m ^{2 or} more. It is preferable to do so. Moreover, if the second film exceeds 10 g/m ² , it takes a long time to dry and has an adverse effect on press formability, which is not preferable. In order to improve the adhesion between the first film and the second film and the hydrophilicity of both films, if necessary,
Adding a silane coupling agent or a titanium coupling agent to the aqueous solution for forming the first film,
Alternatively, a surfactant may be added to the aqueous solution for forming the second film. Here, as the surfactant, nonionic surfactants can be suitably used. In addition, in the aqueous solution for forming the second film,
Conventionally known additives, such as inorganic rust preventives such as sodium nitrite, sodium polyphosphate, and sodium metaborate, benzoic acid and its salts,
Organic rust preventive agents such as paranitrobenzoic acid and its salts, cyclohexylamine carbonate, and benzotriazole may be blended. In addition, after forming the first and second hydrophilic films on the fin material, in the final step, in order to remove dirt from the surface of the fin material, an aqueous solution or solvent containing a surfactant to an extent that does not attack the second film is applied. You may also wash it with hot water or the like. By further forming a coating layer made of wax or wax and a water-soluble polymer compound such as polyvinyl alcohol on the surface of the fin material having the first and second coatings according to the present invention, the fin material can be shaped into a predetermined fin shape. It is preferable to further reduce the wear of the mold during forming. The use of such waxes and water-soluble polymer compounds is described in detail in JP-A-59-118450. In manufacturing the fin material of the present invention, the plate-shaped aluminum material can be treated and processed in the form of a flat plate having the required length, but it is particularly important to treat and process the plate-like aluminum material continuously in the form of a coil. It is preferable to do so. Examples Next, examples of the present invention will be described together with comparative examples. Examples 1 to 4 JISA-1100H24 having a thickness of 1 mm, a width of 50 mm, and a length of 100 mm was used as the aluminum plate. After forming a corrosion-resistant first film made of the following water-soluble synthetic resin on the surface of this aluminum plate, a hydrophilic film-forming agent of the present invention containing various components of the second film as described below was applied, and the coating was heated at 160°C. A hydrophilic second film was formed on the surface of the first film by heating and drying for 10 minutes, thereby producing a fin material for a heat exchanger. In addition,
As the alkali silicate in the components of the hydrophilic second film, one having a SiO ₂ /Na ₂ O ratio of 3 was used. Evaluation test In order to evaluate the performance of the fin material obtained as described above, the film adhesion, corrosion resistance, alkali resistance, hydrophilicity, formability, and mold abrasion resistance were measured, and the obtained results are presented below. Shown in the table. Here, the adhesion was measured by measuring the adhesion between the first film and the second film. Corrosion resistance was determined by measuring the surface condition of the fin material 20 days after the salt spray test. Alkali resistance was measured by measuring pitting on the surface of the fin material after immersing the fin material in saturated lime water with a pH of approximately 13 at 30°C for 100 hours. Hydrophilicity was determined by measuring the contact angle of water on the fin material at the initial stage and after a cycle test in which the oleic acid contamination test (14 hours) and the running water immersion test (8 hours) were repeated three times each. It was measured by In addition, for hydrophilicity evaluation, contact angle of 15° or less is ◎,
16° to 30° was indicated as ○, 31° to 50° was indicated as △, and 51° or more was indicated as ×. After forming, the fin material was subjected to ironing and burring, and the improvement of the limit ironing rate and whether or not cracks were generated at the bent portion during burring were measured. The mold abrasion resistance was measured by measuring the state of wear of the mold when the fin material was molded into a fixed fin shape using a mold. Note that molds with less wear were rated as good. The evaluation of adhesion, corrosion resistance, alkali resistance, moldability, and mold abrasion tests was as follows. ◎: Very good, ○: Good, △: Slightly poor.
×: Defective. For comparison, fin materials having the following three types of coatings on the surface of the aluminum plate were manufactured.
Evaluation tests were conducted on these fin materials in the same manner as above, and the results are summarized in the table below.

[Table] As is clear from the above table, the fin material according to the present invention has superior hydrophilicity compared to the fin material of the comparative example, and also has excellent alkali resistance, moldability, and mold abrasion resistance. It is something that Effects of the Invention As described above, the fin material for a heat exchanger according to the present invention has water-soluble acrylic resin, water-soluble polyurethane resin and its copolymer, water-soluble alkyd resin, and water-soluble polyester resin on the surface of the plate-shaped aluminum material. A first film made of at least one water-soluble synthetic resin selected from the group consisting of ,
A low-molecular organic compound having a carbonyl group selected from the group consisting of esters and amides
(B), the compatibility between the first film and the second film is very good, and the first film made of water-soluble synthetic resin is , has excellent corrosion resistance,
It is softer than chemical films such as chromate films, and the second film stabilizes the alkali silicate (A) film and improves its hydrophilicity. In addition, since it contains a low-molecular organic compound (B) that gives flexibility to the film, the limit ironing rate of the fin material as a whole is improved, making it possible to make the fin thinner, and it also has excellent formability. This allows the height of the bent part to be increased during burring, does not cause cracks, and has very little wear on the mold during fin molding.
It also has the effect of having excellent alkali resistance.

Claims (1)

[Claims] 1 At least one selected from the group consisting of water-soluble acrylic resin, water-soluble polyurethane resin and its copolymer, water-soluble alkyd resin, water-soluble polyester resin, and water-soluble amino resin on the surface of the plate-shaped aluminum material. A first film made of a water-soluble synthetic resin is provided, and the surface of the first film is coated with an alkali silicate (A) and a carbonyl selected from the group consisting of aldehydes, esters, and amides. A fin material for a heat exchanger, which is provided with a second film mainly composed of a low-molecular organic compound (B) having a group.