JPH0381139A - Aluminum fin material for heat exchanger - Google Patents

Abstract

PURPOSE:To increase the corrosion resistance, hydrophilic nature of the material concerned and flexibility of its film and consequently improve its formability and mold wear resistance by a method wherein aluminum fin material is treated by hydrophilic film former after being treated by corrosion-resistant film former. CONSTITUTION:The aluminum fin material for heat exchange concerned is equipped with hydrophilic film through corrosion-resistant film. The corrosion- resistant film is produced by treating fin material by corrosion-resistant film former, which contains synthetic resin having film-forming properties and metal- containing compound forming chelate with the synthetic resin. The hydrophilic film is produced by trating fin material having the corrosion-resistant film by hydrophilic film former, which contains alkali silicate and low-molecular organic compound having carbonyl group.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an aluminum fin material for heat exchangers,
More specifically, it relates to aluminum fin materials used in room air conditioners, car air conditioners, etc.

In this specification, aluminum includes aluminum and aluminum alloys.

Prior Art When the above heat exchanger is used for summer cooling, the surface temperature of the aluminum fins is below the dew point of the atmosphere.
Water droplets adhere to the fin surface.

When water droplets adhere to the fin surface, three problems occur. First, the aluminum fins become susceptible to corrosion. Second, the ventilation resistance increases and the air volume decreases, resulting in a decrease in heat exchange efficiency. Thirdly, water droplets on the fin surface scatter into the interior of the vehicle or the vehicle as air is blown out.

If the fin surface has good wettability, the water adhering to the fin surface will form a film rather than spherical water droplets.To eliminate the above problem, a hydrophilic film is generally formed on the surface of the fin material. There is. Furthermore, for corrosion protection, a corrosion-resistant film is interposed between the fin material and the hydrophilic film.

Conventionally, in order to form a corrosion-resistant film on aluminum fin materials, an inorganic treatment agent was used to form a chromate film or a boehmite film on the fin material, or an organic treatment agent was used to form a urethane film on the fin material. A resin film or acrylic acid resin film was formed.

Conventionally, in order to form a hydrophilic film on an aluminum fin material, a water glass (alkali silicate) film was formed on the surface of the fin material.

Problems to be Solved by the Invention When an inorganic treatment agent is used to form a corrosion-resistant film, the corrosion resistance of the aluminum fin material improves, but
A problem arises in that moldability deteriorates. When an organic treatment agent is used, on the contrary, the moldability of the fin material improves, but the corrosion resistance is not sufficient, and to compensate for this, it is necessary to make the corrosion-resistant film particularly thick. If the corrosion-resistant film is thick,
When the fins are brazed or welded during the assembly of the heat exchanger, the corrosion-resistant coating is burned and turns yellow or brown, which impairs the appearance of the heat exchanger.

When a water glass film is formed as a hydrophilic film, the initial hydrophilicity of the fins is improved, but this hydrophilicity quickly deteriorates and has a disadvantage of poor sustainability. In addition, since the water glass film is hard, it not only causes cracks in the bent portions of the fins during fin forming such as burring, but also has the drawback that the mold is easily worn out.

An object of the present invention is to provide an aluminum fin material for a heat exchanger that solves all of the above problems.

Means for Solving the Problems The fin material for a heat exchanger according to the present invention has an aluminum fin material provided with a hydrophilic film via a corrosion-resistant film,
The corrosion-resistant film is formed by treating the fin material with a corrosion-resistant film-forming agent containing a synthetic resin with film-forming ability and a metal-containing compound that forms a chelate with the synthetic resin. It is formed by treating a fin material having a corrosion-resistant film with a hydrophilic film-forming agent containing an alkali silicate and a low-molecular organic compound having a carbonyl group.

The synthetic resin having film-forming ability in the corrosion-resistant film-forming agent is a necessary component to ensure good moldability of the fin material, and a typical example thereof is polyacrylic acid. Other materials such as polyvinyl alcohol and cellulose hydroxy ether can also be used.

The metal-containing compound that forms a chelate with the synthetic resin in the corrosion-resistant film forming agent is a necessary component to ensure good corrosion resistance of the treated fin material, and typical examples include trivalent or hexavalent chromic acid. can give. Other metal oxides such as zirconium oxide, titanium oxide or chromium oxide; metal salts such as potassium chromate, sodium chromate, potassium dichromate or sodium dichromate; metals such as titanate esters Acid esters; metal salts of acids such as chromium nitrate, zirconium nitrate, zirconium fluoride, titanium fluoride or titanium sulfate can also be used.

The preferred thickness of the corrosion-resistant film is 0.1 to 1.0 μm. If the film thickness is less than 0.1 μm, the performance as a base for the hydrophilic film is insufficient, and if the film thickness exceeds 10 μm, the film may be burnt and discolored by heat during assembly of the heat exchanger.

The preferred blending ratio of synthetic resin and metal-containing compound is 2:8~
The ratio is 9:1, and 3-near to 7:3 is more preferred.

The alkali silicate in the hydrophilic film-forming agent is the main component for imparting hydrophilicity to the aluminum fin material, and is expressed as S i 02 /M2O (where M means an alkali metal such as lithium, sodium, or potassium). ) must have a ratio of 1 or more. In particular, it is preferable to use an alkali silicate having S102/M2O of 2 to 5. When the ratio of S I 02 /M2O is less than 1, there is less 5io2 than the alkaline component, so the corrosion effect of the alkali component on the aluminum fin material increases.

The low-molecular organic compound in the hydrophilic film-forming agent is a low-molecular organic compound having a carbonyl group (>C-0) in the molecule, which stabilizes the film formed by the alkali silicate and makes it more hydrophilic. It improves the properties and gives flexibility to the film.

Specific examples of such low-molecular organic compounds include aldehydes, esters, and amides.

As the aldehyde, formaldehyde, acetaldehyde, glyoxal, malondialdehyde, succindialdehyde, glutardialdehyde or furfuraldialdehyde is 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; ethylene glycol diacetate, glycerine triacetate, ethylene glycol dipropionate, etc. fatty acid ester of polyhydric alcohol; γ-butyrolactone, ε-
Intra-molecular esters such as caprolactone; 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 esters, sorbitol monoformate, sorbitol monoacetate, and glycose acid monoacetate; monohydric alcohol esters of polybasic acids such as dimethyl succinate and dimethyl maleate; ethylene carbonate, propylene carbonate, and glycerin Cyclic carbonates such as carbonate are used.

As amides, use is made of formamide, dimethylformamide, acetamide, dimethylacetamide, propionamide, butyramide, acrylamide, malondiamide, pyrrolidone or caprolatam.

Among the low-molecular-weight organic compounds, water-soluble compounds such as aldehydes and esters are preferably used in view of uniform treatment. It is desirable to use glyoxal because it can form a highly hydrophilic film.

The water-soluble organic polymer compound further improves the hydrophilicity of the film formed from the alkali silicate and the low molecular weight organic compound having a carbonyl group, and also improves the flexibility of the film.

Specific examples of water-soluble organic polymer compounds include polysaccharide-based natural polymers, water-soluble protein-based natural polymers, anionic, nonionic or cationic addition polymerization-based water-soluble synthetic polymers, and polycondensation-based water-soluble polymers. can be given.

As the polysaccharide natural polymer, soluble starch, carboxymethylcellulose, hydroxyethylcellulose, guar gum, gum tragacanth, xanthan gum or sodium alginate is used. For example, gelatin 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 or 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 polyalkylamino (meth) compounds such as polyethyleneimine, Mannich-modified compounds of polyacrylamide, diacryldimethylaluminum chloride, polyvinylimidacillin, and dimethylaminoethyl acrylate polymers. Use acrylate.

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. A water-soluble polyurethane resin, a polyhydroxymethylurea resin or a polyhydroxymethylmelamine resin which is polycondensed with a polyisocyanate is used.

Among water-soluble organic polymer compounds, it is preferable to use anionic addition-polymerized water-soluble polymers having carboxylic acids or carboxylic acid groups, especially polyacrylic acid, acrylic acid copolymers, and maleic acid copolymers. Alternatively, it is preferable to use these alkali metal salts. Examples of acrylic acid copolymers or maleic acid copolymers include copolymers of acrylic acid and maleic acid, acrylic acid or maleic acid, and methacrylic acid, methyl methacrylate, ethyl methacrynide, and hydroxyethyl methacrylate. , itaconic acid or vinylsulfonic acid, copolymers with acrylamide are preferably used.

The blending ratio of the alkali silicate and the low molecular weight organic compound having a carbonyl group is 061 to 5 parts by weight of the low molecular weight organic compound having a carbonyl group to 1 part by weight of the alkali silicate.

When adding a water-soluble organic polymer compound to alkali silicic acid and a low-molecular-weight organic compound having a carbonyl group, the blending ratio of the three is 1 part by weight of the alkali silicate to the low-molecular-weight organic compound having a carbonyl group. 0.1 to 5 parts by weight, and 0.01 to 5 parts by weight of the water-soluble organic polymer compound.

In the above, if the amount of alkali silicate in the hydrophilic film forming agent is small, a sufficient hydrophilic film will not be formed on the surface of the aluminum fin material. On the other hand, if the amount is too high, the hydrophilic film becomes too hard, resulting in poor moldability and mold wear resistance.

If the low molecular weight organic compound having a carbonyl group is less than 0.1 part by weight per 1 part by weight of the alkali silicate, the effect of adding the low molecular weight organic compound will not be apparent, and if it exceeds 5 parts by weight, the relative Since there is less alkali silicate in
Hydrophilicity is not sufficiently exhibited.

If the water-soluble organic polymer compound is less than 0.01 parts by weight per 1 part by weight of the alkali silicate, the effect of adding the water-soluble organic polymer compound will not be apparent, and if it exceeds 5 parts by weight, no formation will occur. The resulting film becomes more easily eluted by water, and the sustained effect of hydrophilicity is therefore reduced.

The alkali silicate, the low-molecular organic compound having a carbonyl group, and the water-soluble polymer compound are used after being diluted with water. The dilution ratio is determined in consideration of the hydrophilicity, film thickness, and workability of the film.

The surface of the aluminum fin material having a corrosion-resistant coating is treated with a hydrophilic film-forming agent by spraying, brushing or dipping.

By heating and drying the fin material after the above treatment at a temperature of 50 to 200C, preferably 150 to 180C for a period of 30 seconds to 30 minutes, a hydrophilic film is formed on its surface.

If the heat drying temperature is less than 50°C, the composition will not form a film sufficiently, and if it is heated above 200°C, not only will there be no heating effect, but the quality of the fin material will be adversely affected.

If the heat drying time is less than 30 seconds, the composition will not form a film sufficiently, and if it exceeds 30 minutes, productivity will decrease. If the heating drying temperature is high, such as 1,60 to 200°C, the drying time may be as short as 30 seconds to 1 minute, but if the temperature is
If the temperature is lower than 60°C, it is necessary to increase the drying time. If heat drying is insufficient, the composition will not form a film sufficiently.

The thickness of the hydrophilic film is 0.1 to 10 g/l12, preferably 0.5 to 3 g/l2. If the thickness of the film is 0.1 g/i2 or more, the initial hydrophilicity is good, but in order to maintain good hydrophilicity, it is preferable to form a film of 0.5 g/m2 or more. If the film exceeds 10 g/112, it will take a long time to dry and will have an adverse effect on moldability.

Hydrophilic film-forming agents include conventionally known additives, such as inorganic rust inhibitors such as sodium nitrite, sodium polyphosphate, and sodium metaborate, benzoic acid and its salts, varanitrobenzoic acid and its salts, and cyclohexylamine. Organic rust preventive agents such as carbonates and benzotriazole may be added.

By further forming a coating layer made of wax or a water-soluble polymer compound such as wax and polyvinyl alcohol on the surface of the hydrophilic film, wear of the mold when molding the fin material into a predetermined fin shape is reduced. It can be further reduced.

Function: According to the aluminum fin material for heat exchangers of the present invention,
The aluminum fin material is provided with a hydrophilic film via a corrosion-resistant film, and the corrosion-resistant film is made using a corrosion-resistant film-forming agent containing a synthetic resin with film-forming ability and a metal-containing compound that forms a chelate with the synthetic resin. Since it is formed by treating the fin material with a heat exchanger, it has sufficient corrosion resistance without having to make the corrosion-resistant film particularly thick. During welding, the corrosion-resistant coating does not burn, turn yellow or brown, and has excellent formability.

In addition, the hydrophilic film is formed by treating a fin material with a corrosion-resistant film with a hydrophilic film-forming agent containing an alkali silicate and a low-molecular-weight organic compound having a carbonyl group. By heating and drying, the alkali silicate and the low molecular weight organic compound having a carbonyl group react to form a three-dimensional insoluble silicate film. At this time, the low-molecular organic compound becomes an organic carboxylate or an organic hydroxycarboxylate and is incorporated into the three-dimensional network polymer of the silicate, forming a stable silicate film.
In addition to improving hydrophilicity, the flexibility of the film increases, so it has good ductility, so no cracks occur during fin molding, and there is very little wear on the mold during molding.

When a water-soluble organic polymer compound is further added to the hydrophilic film-forming agent, the water-soluble organic polymer compound is further incorporated into the three-dimensional silicate polymer, further increasing the hydrophilicity and flexibility of the film. As a result, moldability and mold wear resistance are further improved.

Example Examples of the present invention will be described below along with comparative examples.

As aluminum fin material, thickness 1cm, width 50n+
JIS A1100-H2 with m and length 1100n
4 was used.

As shown in Table 1, a corrosion-resistant film was formed on the surface of the aluminum fin material using various corrosion-resistant film-forming agents, and various hydrophilic film-forming agents were further applied thereto, and the coating was heated at 160°C for 10 minutes. A hydrophilic film was formed on the surface of the fin material having a corrosion-resistant film by heating and drying for 1 minute. In addition, as the alkali silicate in the components of the hydrophilic film-forming agent, one having a 5i02/Na2O ratio of 3 was used.

In order to evaluate the performance of the above-mentioned various fin materials, corrosion resistance, heat discoloration resistance, hydrophilicity, moldability, and mold wear resistance were determined by Gl, and the obtained results are shown in Table 1.

Regarding corrosion resistance, the fin material was sprayed with salt water for 300 hours, and if there were no abnormalities, a mark of ◎ was given, and if there was slight corrosion of the solder, a mark of O was given to indicate the corrosion resistance evaluation. .

Regarding heat discoloration resistance, when the fin material is heated at 400°C for 1 minute, if there is no change in appearance, a ◎ mark is given, and if the surface becomes significantly yellowed, a Δ mark is given. The heat discoloration resistance was evaluated by marking the cases with an x mark.

Hydrophilicity is determined in the early stages and in the oleic acid contamination test (
The contact angle of water on the fin material was measured at the stage after a cycle test in which a test (14 hours) and a running water immersion test (8 hours) were alternately repeated three times.

In addition, for hydrophilic evaluation, contact angle of 15° or less is ◎, 16°
- 30'' was indicated as 0131° - 50'' was indicated as △, and 51° or more was indicated as ×.

Formability was measured by performing a burring process on an aluminum fin material having a hydrophilic film and determining whether or not cracks were formed at the bent portions.

The mold wear resistance was measured by measuring the state of wear of the mold when a fin material having a corrosion-resistant film and a hydrophilic film was molded into a fixed fin shape using a mold.

The moldability and mold wear resistance tests were evaluated as shown below.

◎: Very good, O: Good, △: Slightly poor, ×: Poor.

(The following is a blank space) As is clear from Table 1 above, the fin materials of Examples have superior corrosion resistance, heat discoloration resistance, hydrophilicity, moldability, and mold wear resistance compared to those of Comparative Examples. Moreover, there is little deterioration of hydrophilicity over time.

Effects of the Invention According to the aluminum fin material for heat exchangers of the present invention,
Sufficient corrosion resistance can be obtained with a thickness that does not discolor the corrosion-resistant coating during brazing or welding, so the appearance of the heat exchanger is not impaired, and the hydrophilic properties of the hydrophilic coating can be maintained for a long period of time. It has excellent corrosion resistance and mold abrasion resistance, and both films have good moldability, so there is no fear that molding will be difficult or that cracks will occur.

that's all

Claims (13)

[Claims] (1) The aluminum fin material is provided with a hydrophilic film via a corrosion-resistant film, and the corrosion-resistant film contains a synthetic resin with film-forming ability and a metal-containing compound that forms a chelate with the synthetic resin. The hydrophilic film is formed by treating the fin material with a
An aluminum fin material for a heat exchanger, which is formed by treating a fin material with a corrosion-resistant film with a hydrophilic film-forming agent containing an alkali silicate and a low-molecular-weight organic compound having a carbonyl group. (2) The aluminum fin material for a heat exchanger according to claim 1, wherein the corrosion-resistant film has a thickness of 0.1 to 1.0 μm. (3) The blending ratio of synthetic resin and metal-containing compound is 2:8 to 9
The aluminum fin material for a heat exchanger according to claim 1, wherein the aluminum fin material is: 1. (4) The aluminum fin material for a heat exchanger according to claim 1, wherein the synthetic resin is polyacrylic acid, polyvinyl alcohol, or cellulose hydroxyethyl ether. (5) The hydrophilic film-forming agent contains 0 low molecular weight organic compound having a carbonyl group per 1 part by weight of the alkali silicate.
．． The aluminum fin material for a heat exchanger according to claim 1, wherein the aluminum fin material is blended in a proportion of 1 to 5 parts by weight. (6) The aluminum fin material for a heat exchanger according to claim 1, wherein the hydrophilic film-forming agent further contains a water-soluble organic polymer compound. (7) The hydrophilic film-forming agent contains 0 low-molecular organic compound having a carbonyl group per 1 part by weight of the alkali silicate.
．． 1 to 5 parts by weight and 0.0 parts by weight of a water-soluble organic polymer compound
The aluminum fin material for a heat exchanger according to claim 1, wherein the aluminum fin material is blended in a proportion of 1 to 5 parts by weight. (8) Claim 1, 5, 6 or 7, wherein the alkali silicate has a ratio of SiO_2/M_2O (in the formula, M means an alkali metal such as lithium, sodium, potassium, etc.) of 1 or more. Aluminum fin material for heat exchangers as described. (9) The aluminum fin for a heat exchanger according to claim 1, wherein the metal-containing compound is at least one selected from the group consisting of metal oxides, metal acids or salts thereof, metal acid esters, and metal salts of acids. Material. (10) The aluminum fin material for a heat exchanger according to claim 9, wherein the metal oxide is zirconium oxide, titanium oxide, or chromium oxide. (11) The metal acid or its salt is trivalent or hexavalent chromic acid, potassium chromate, sodium chromate,
The aluminum fin material for a heat exchanger according to claim 9, which is potassium dichromate or sodium dichromate. (12) The aluminum fin material for a heat exchanger according to claim 9, wherein the metal acid ester is a titanate ester. (13) The aluminum fin material for a heat exchanger according to claim 9, wherein the acid metal salt is chromium nitrate, zirconium nitrate, zirconium fluoride, titanium fluoride, or titanium sulfate.