JPS61246059A - Fin material for heat exchanger - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] Industrial applications The present 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 heat exchangers, particularly in evaporators of air conditioners, water droplets adhere to the surfaces of the fins because the surface temperature of the fins 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; if the fin surface has good wettability, the attached water becomes water droplets), which reduces ventilation resistance and increases 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). 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. 58-20950 (see issue). According to the previously proposed hydrophilic film-forming agent, it is possible to form a film with excellent hydrophilicity and durability on the surface of the fin material. In terms of affinity with hydrophilic coatings, it is desirable to provide a coating that is similarly hydrophilic. Here, when 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, the fin material as a whole is This leads to problems such as poor moldability and poor mold abrasion due to the occurrence of cracks in bent portions during the burring process during fin molding. 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. The question of what type of base film to provide for the above-mentioned hydrophilic film has become a critical and important issue.

Purpose of the Invention The present invention has been made in view of the above points, and has a hydrophilic coating as a surface layer that has excellent hydrophilicity and its sustainability, and a hydrophilic coating that has excellent corrosion resistance and hydrophilicity and is relatively durable. By providing a film as a soft base layer, the limiting ironing rate can be improved and the fins can be made thinner.
It also has excellent formability, allowing the height of the bent part to be increased during burring, without cracking, and with very little wear on the mold during fin forming. The object of the present invention is to provide a fin material for a heat exchanger that is small in amount and has excellent alkali resistance.

Constituent of the Invention A material 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 is applied to the surface of the plate-shaped aluminum material. A first coating made of at least one hydrophilic synthetic resin is provided, and the first coating is made of at least one hydrophilic synthetic resin.
The gist of the present invention is a fin material for a heat exchanger, in which a second film is provided on the surface of the film, and the second film is mainly composed of an alkali silicate (A) and a low-molecular-weight organic compound ([3) having a carboxyl group].

1. As the hydrophilic synthetic resin constituting the first film, at least one of a water-soluble acrylic resin, a water-soluble polyurethane resin and its copolymer, a water-soluble alkyd resin, a water-soluble polyester resin, and a water-soluble amino resin is used. use. 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 hydrophilic synthetic resin on the surface of a plate-shaped aluminum material is performed by dipping, spraying, or coating using an aqueous solution containing the hydrophilic synthetic resin.

The first film thus formed has excellent corrosion resistance as well as hydrophilicity.

The thickness of the first film made of such hydrophilic synthetic resin is:
For example, it is preferably 1 to 50 μm. Here the first
If the thickness of the film is less than 1 μm, there will be a problem in corrosion resistance, and if it exceeds 50 μm, the heat conduction of the aluminum fin material will be inhibited and the formability will deteriorate.

Next, the alkali silicate (A
) constitutes the main component for imparting hydrophilicity to the fin material, and 5i02/M20 (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, it is preferable to use an alkali silicate having a Si 02 /M20 of 2 to 5. Here, when the ratio of SiO2/M20 is less than 1, 81
Since the amount of 02 is small, the corrosion effect of aluminum by the alkaline component becomes large.

Further, the above-mentioned low-molecular organic compound (B) is a low-molecular organic compound having carbonyl W (>C=O) in the molecule, which stabilizes the film formed by the alkali citrate (A) and makes it more It avoids improving hydrophilicity and gives flexibility to the film.

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

Here, as the aldehydes, formaldehyde, acetaldehyde, glyoxal, malondialdehyde, succindialdehyde, glutardialdehyde, furfuraldialdehyde, etc. are used.

In addition, esters include fatty acid esters of monohydric alcohols such as methyl formate, ethyl acetate, methyl acetate, ethyl acetate, amyl acetate, and methyl propionate, as well as ethylene glycol diacetate, glycerine triacetate, and ethylene glycol dipropionate. Fatty acid Nisdel of polyhydric alcohols such as esters, intramolecular esters such as γ-butyrolactone, ε-caprolactone, ethylene glycol monoformate, ethylene glycol monoacetate, ethylene glycol monopropionate, glycerin monoformate, glycerin Polyhydric alcohol partial esters such as Nisder monoacetate, glycerine monopropionate, glycerine diformate, glyreline diacetate, sorbitol monoformate, sorbitol monoacetate, and glycose acid monoacetate, as well as dimethyl succinate, maleic acid Monohydric alcohol esterates of polybasic acids such as dimethyl, cyclic carbonates such as propylene carbonate, glycerin carbonate, etc. 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 organic compounds (B), water-soluble compounds are preferably used in order to perform uniform treatment,
It is particularly preferred to use aldehydes and esters. 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, the polysaccharide natural polymers include 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, 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 polymerization water-soluble synthetic polymers include polyethyleneimine, Mannich-modified compounds of polyacrylamide, diacryldimethylaluminum chloride,
Polyalkylamino (meth)acrylates such as polyvinylimidacillin and dimethylaminoethyl acrylate are used.

Polycondensation water-soluble synthetic polymers include polyoxyethylene glycol, polyoxyethylene oxypropylene glycol, and other alkylene polyols, ethylene diamino and hexamethyl diamino and other polyamino polycondensates with epichlorohydrin, and water-soluble polyethers. Water-soluble polyurethane resin, polyhydroxymethylurea resin, polyhydroxymethylmelamine resin, etc., which are polycondensed with polyisocyanate and polyisocyanate, are used.

Among the above-mentioned water-soluble organic polymer compounds (C), it is preferable to use anionic addition-polymerized water-soluble polymers containing carboxylic acids or carboxylic acid groups, particularly polyacrylic acid, acrylic acid copolymers, Preference is given to using maleic 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 and methacrylic acid, medyl methacrylate, and ethyl methacrylate. , and droxyethyl methacrylate, itaconic acid, vinylsulfonic acid, 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), alkali silicate (A
) A low molecular weight organic compound (B) having a carbonyl group is blended in a ratio of 0.1 to 5 parts by weight per 1 part by weight.

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). part, and a water-soluble organic polymer compound at a ratio 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.

In addition, the amount of the low molecular weight organic compound (8) having a carbonyl group is 0.1 fflf per 1 weight part of the alkali silicon M salt (A).
If the amount is less than u parts, the effect of adding the low-molecular organic compound (B) will not be apparent, and if it exceeds 5,000 m parts, the alkali silicate (A) will be relatively small, so hydrophilicity will be sufficiently exhibited. Not done.

The water-soluble organic polymer compound (C) is an alkali silicate (A
) If it is less than 0.011 parts by weight per part by weight, the effect of adding the polymer compound (C) will not be apparent, and if it exceeds 5 parts by weight, the formed film will be easily eluted into water. , the lasting effect of hydrophilicity is reduced.

Here, an alkali silicate (A), a low-molecular compound (B) having a carbonyl group, and a water-soluble polymer compound (
C) is used by diluting it 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 treated with the aqueous solution is heated and dried at a humidity of 50 to 200°C, preferably 150 to 180°C, for a period of 30 seconds to 30 minutes to form a hydrophilic second film on the surface of the first film. Form.

Here, if the heat drying temperature is less than 50°C, the composition will not form a film sufficiently, and if it exceeds 200°C, further heating will have no effect. Moreover, if the heating drying time is less than 30 seconds, the composition will not be formed into a film sufficiently, and if it exceeds 30 minutes, productivity will decrease. And the heat drying humidity is 16
If the temperature is 0 to 200°C, the drying time may be as short as 30 seconds to 1 minute, but if the temperature is low, the drying time needs to be longer. If heat drying is insufficient, the composition will not form a film sufficiently.

Further, the hydrophilic second film is formed on the surface of the first film at a temperature of 0°1 to 10°.
g/m2, preferably 0.5 to 3 (J/m2). Here, if the second film is 0°1 (1/m2 or more), the initial hydrophilicity is good, but In order to maintain good hydrophilicity, it is preferable to form a second film with a thickness of 0.50 g/m2 or more.If the second film exceeds 10 g/12, it will take a long time to dry, and press molding will be difficult. It is undesirable because it has a negative effect on sexuality.

In order to improve the adhesion between the first film and the second film and the hydrophilicity of both films, if necessary, a silane coupling agent or a titanium coupling agent may be added 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, the aqueous solution for forming the second film contains 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, cyclohexylaminocarbonate, 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 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 molding. Regarding the use of such waxes and water-soluble polymer compounds, Japanese Patent Application Laid-Open No. 59-1
No. 18450 describes this in detail.

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.

Example Next, examples of the present invention will be described together with comparative examples.

Examples 1 to 4 J15A-1100H24 having a thickness of 1 mm, a width of 50 mm, and a length of 100 mm was used as an aluminum plate.

After forming a corrosion-resistant first film made of the following hydrophilic synthetic resin on the surface of this aluminum plate, a second corrosion-resistant film as shown below is formed.
The hydrophilic film-forming agent of the present invention containing various components of the film is applied and dried by heating at 160° C. for 10 minutes to form a hydrophilic second film on the surface of the first film, thereby forming a fin material for a heat exchanger. Manufactured. In addition, as the alkali silicate in the components of the hydrophilic second film, S! 7j using one with a 02/Na2O ratio of 3.

In order to evaluate the performance of the fin material obtained as described in the evaluation test report, the sealing properties, corrosion resistance, alkali resistance, hydrophilicity,
The moldability and mold abrasion properties were measured, and the results are shown in Table M.

Here, the adhesion was determined by measuring the visibility between the first film and the second film.

Corrosion resistance was determined by measuring the surface condition of the fin material after salt spray test 20 ().

Alkali resistance was determined by immersing the fin material in saturated lime water with a pH of about 13 for 100 hours at 30°C, and then measuring the pitting state on the surface of the fin material.

Hydrophilicity is determined in the early stages and in the oleic acid contamination test (
14 hours) and running water immersion test (8 hours) were repeated three times alternately.
Measurements were made by measuring the contact angle of water on each fin material.

In addition, for hydrophilic evaluation, 2 contact angles of 15° or less are ◎, 16°
~・30° is ○, 31° to 50° is Δ, 51° or more is ×
was displayed.

Formability was determined by subjecting the inner material to ironing and burring, and measuring the improvement in the limit ironing rate and whether or not cracks were generated at the bent portion during burring.

The mold abrasion resistance was measured by measuring the state of wear of the mold when the fin material was molded into a fixed twin 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, ○: Fair f, △: Slightly poor, X: Poor.

For comparison, fin materials were manufactured with the following three types of coatings on the surface of the aluminum plate, and evaluation tests were conducted on these fins H in the same manner as in the case described in F.
The results are summarized in the table below.

(Here are the blanks) As is clear from the table above, the fin material according to the present invention has superior hydrophilicity, as well as alkali resistance, moldability, and mold abrasion resistance, compared to the fin material of the comparative example. It is also excellent.

Effects of the Invention As described above, the fin material for a heat exchanger according to the present invention has the following features:
At least one resin 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 is applied to the surface of the plate-shaped aluminum material. A first film made of two hydrophilic synthetic resins is provided on the surface of the first film. Since the first film made of hydrophilic synthetic resin is provided as the base layer of the second film, which determines its excellent hydrophilicity and its sustainability, the first film and the second film are The compatibility of the coating is very good, and the first coating made of hydrophilic synthetic resin has excellent corrosion resistance and is softer than chemical coatings such as chromate coating, so it is difficult to push the limits of the fin material as a whole. The fins can be made thinner with improved moldability, and have excellent formability, making it possible to increase the height of the bent part during burring and preventing cracks from forming. In addition, there is very little wear on the mold during fin molding, and it also has excellent alkali resistance.

that's all

Claims (1)

[Claims] 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 is applied to the surface of the plate-shaped aluminum material. A first film made of a hydrophilic synthetic resin is provided, and this first film is made of a hydrophilic synthetic resin.
A second layer containing alkali silicate (A) and a low molecular weight organic compound (B) having a carboxyl group as main components is applied to the surface of the film.
Fin material for heat exchangers that is coated with a film.