JPH086063B2 - Hydrophilic surface treatment agent and treatment method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a hydrophilic surface treating agent for a heat exchanger fin and a surface treating method, and more specifically, an aluminum fin of a heat exchanger has corrosion resistance and hydrophilicity. The present invention relates to a hydrophilic surface treating agent and a surface treating method for forming a film.

[Conventional technology]

Aluminum and its alloys are lightweight, have excellent workability and thermal conductivity, and are widely used in heat exchangers.
With the spread of air conditioning systems, the number of air conditioners for both cooling, dehumidification, and heating / cooling has increased, and aluminum alloy fins are generally used in the heat exchange section of these air conditioners.

During the cooling operation of the air conditioner, water in the air tends to adhere to the fin surface as condensed water. In order to prevent this, it is possible to make the fin surface water repellent, but then the condensed water will adhere to the fins in a hemispherical shape or will exist in a bridge shape between the fins, and the smooth flow of air will occur. To prevent ventilation and increase ventilation resistance. In this way, making the fin surface water-repellent decreases the heat exchange rate.

On the other hand, aluminum and its alloys are originally excellent in corrosion resistance, but when condensed water stays on the fin surface for a long period of time, formation of oxygen concentration cells or pollutants in the atmosphere gradually adhere and are concentrated to cause hydration and corrosion reactions. Is promoted. This corrosion product is, of course, deposited on the surface of the fins and impairs the heat exchange characteristics, but during heating operation in winter, it becomes white fine powder and is discharged together with warm air by the blower.

Therefore, in order to improve these problems, an attempt was made to form a film having both of the above properties on the fin surface for the purpose of improving the corrosion resistance of the fin and, at the same time, increasing the hydrophilicity of the surface. There is.

Such methods are roughly classified into a method of forming an inorganic film and a method of forming an organic film. As a method for forming an inorganic film, for example, after a corrosion resistant film is provided by a chromate chemical conversion treatment, a boehmite system (JP-A-56-108071) or a silicate system (JP-A-56-13).
No. 078 and No. 50-38645). However, although such an inorganic film has excellent corrosion resistance, it does not necessarily have sufficient hydrophilicity. In the case of silicate-based treatment, the odor peculiar to silica is emitted from the air conditioner and there is discomfort.When it is applied to precoat treatment, the coating film cracks at the time of cutting and corrosion resistance decreases, and cutting is also difficult. There is a drawback that the tool wear is remarkable at the time.

On the other hand, as a method of forming an organic film, for example, a method of applying a water-soluble or water-acidic polymer resin to which an aqueous solution containing silica fine particles is applied, followed by heating and curing to form a hydrophilic film (JP-A-55-99976). No. 53-125437
No. 55-164264) are typical. However, since it contains silica fine particles, when it is applied to the precoat treatment, the coating film cracks during cutting, the corrosion resistance decreases, and the tool wear during cutting is significant. In addition, the hydrophilicity is slightly inferior, and there is a problem that a slight odor peculiar to silica is emitted from the air conditioner to cause discomfort. Incidentally, JP-A-55
-164264 describes the use of water-soluble melamine, alkyd, polyester and acrylic for the same purpose, but their performance is not yet sufficient.

Further, JP-A-62-105629 discloses an organic film made of a water-soluble acrylic resin or a water-soluble urethane resin as a corrosion-resistant film on the surface of an aluminum thin plate, or a chromate film,
An inorganic film composed of a boehmite film or an anodized film is formed, and an organic compound composed of one or two kinds of a water-soluble cellulose resin or polyvinyl alcohol as a hydrophilic covering layer and an organic curing agent such as a melamine resin are formed on the inorganic film. Disclosed is a heat exchanger fin agent having a skin covering layer formed of.

However, this hydrophilic film is also insufficient in hydrophilicity and water solubility resistance.

[Problems to be solved by the invention]

As described above, the conventional surface treatment technology for heat exchanger fins has sufficient hydrophilicity and corrosion resistance, has good film strength, and cannot provide an odorless film.

Therefore, an object of the present invention is to solve such a problem, to improve hydrophilicity,
Provide a surface treatment agent and a surface treatment method for forming a hydrophilic film for heat exchanger fins, which has good corrosion resistance, water solubility resistance, solvent resistance, etc., does not generate cracks during processing, and does not generate an unpleasant odor. It is to be.

[Means for solving problems]

The hydrophilic surface treating agent of the present invention comprises 5 to 25 parts by weight of sodium salt and / or potassium salt of carboxymethyl cellulose and 25 to 25 parts of ammonium salt of carboxymethyl cellulose.
It is characterized by containing 50 parts by weight and 25 to 70 parts by weight of N-methylol acrylamide.

In addition, the surface treatment method of the present invention comprises: after subjecting an aluminum material to a base treatment, 5 to 25 parts by weight of sodium salt and / or potassium salt of carboxymethyl cellulose, 25 to 50 parts by weight of ammonium salt of carboxymethyl cellulose, and N.
It is characterized in that it is treated with a hydrophilic surface treating material containing 25 to 70 parts by weight of methylol acrylamide.

In general, carboxymethyl cellulose having a degree of polymerization of 30 to 800 is used as sodium salt, potassium salt and ammonium salt. If the degree of polymerization is less than 30, the water solubility is low, and if it exceeds 800, the viscosity is high and the workability is deteriorated. The preferred degree of polymerization is 80 to 500.

The sodium salt and potassium salt of carboxymethyl cellulose have a function of imparting hydrophilicity. In order to effectively exhibit this action, the amount of sodium salt and / or potassium salt of carboxymethyl cellulose in the hydrophilic surface treating agent is 5 to 25 parts by weight. If it is less than 5 parts by weight, the hydrophilicity (expressed by the contact angle of water) is low, and if it exceeds 25 parts by weight, an odor problem occurs. The preferred content is 9 to 16 parts by weight.

The ammonium salt of carboxymethyl cellulose has a function of reducing odor. In order to effectively exert this action, the content of the NH ₄ salt of carboxymethyl cellulose in the hydrophilic surface treatment agent is 25 to 50 parts by weight,
If it is less than 50 parts by weight, the odor suppressing effect is insufficient, and if it exceeds 50 parts by weight, the hydrophilicity is lowered. The preferred content is 30-45
Parts by weight.

Na salt and / or K salt of carboxymethyl cellulose NH
The ratio with ₄ salts is 0.1: 1 to 1: 1 by weight. If the Na salt and / or K salt is less than 0.1 of the NH ₄ salt, the hydrophilicity is insufficient, and conversely if it exceeds 1, the odor suppressing effect is insufficient. Na
The preferable mixing ratio of the salt and / or K salt / NH ₄ salt is 0.2 to 0.53.
Is.

N-methylol acrylamide has the functions of improving the adhesion of the hydrophilic film and improving the water solubility. The content of N-methylol acrylamide is 25-70
If the amount is less than 25 parts by weight, the adhesion (film-forming property) and water solubility of the film are insufficient, and if it exceeds 70 parts by weight, the hydrophilicity is lowered. The total ratio of Na salt and / or K salt of carboxymethyl cellulose to N-methylol acrylamide and NH ₄ salt is 0.43 to 3.0,
If it is less than 3.0, the hydrophilicity is insufficient, and if it exceeds 3.0, a film having poor film-forming properties and water solubility is formed. The preferred ratio is 0.64 to 1.56.

The hydrophilic surface treating agent of the present invention may contain a surfactant, an antifungal agent, an antiseptic agent and the like in addition to the above-mentioned essential components.

As the surfactant, there are nonionic, cationic, and anionic ones, and the anionic one is preferable from the viewpoint of hydrophilic sustainability and coating workability. As an anionic surfactant,
Sodium alkyl benzene sulfonate, sodium alkyl diphenyl ether disulfonate, sodium alkyl naphthalene sulfonate, naphthalene sulfonic acid-
A sodium salt of a formalin condensate or the like can be used. The addition amount of the anionic surfactant is 1 to 10 parts by weight. If it is less than 1 part by weight, the effect of addition is insufficient, and if it exceeds 10 parts by weight, the water solubility is lowered.

Quaternary ammonium salts, nitrogen-containing sulfur compounds, halogen-containing nitrogen-sulfur compounds, 1,2-benzisothiazolin-3-one (BIT), organic iodine compounds, benzimidazole compounds, etc. are used as fungicides and preservatives. can do. The addition amount is preferably 0.15 to 1.5 parts by weight.

Next, the surface treatment method of the present invention will be described. Before forming a film with a hydrophilic surface treating agent, first, a base treatment is performed. As the base treatment, degreasing treatment is first performed. The degreasing treatment may be either solvent degreasing with trichloroethylene, perchlorethylene, gasoline, normal hexane or the like, or alkaline degreasing with an alkaline solution of sodium hydroxide, sodium carbonate, sodium silicate, sodium phosphate or the like.

A corrosion resistant film is formed by chemical conversion treatment after degreasing. The corrosion resistant film can be obtained by a chromate treatment. The chromate treatment is performed with a treatment liquid prepared by adding an additive to chromic anhydride, sulfuric acid, nitric acid, hydrofluoric acid, phosphoric acid and the like. There are a phosphoric acid chromate system that uses phosphoric acid as an inorganic acid and a chromium chromate system that uses another acid. The latter has better corrosion resistance. The chromate treatment can be carried out by dipping in the treatment liquid, spraying the treatment liquid, or the like, but the dipping method is simple and preferable for fins of a heat exchanger having a complicated shape. The corrosion resistant coating obtained by the chromate treatment has a Cr content of 3 to 50 mg / m ² . If it is less than 3 mg / m ² , the corrosion resistance is insufficient, and if it exceeds 50 mg / m ² , a reaction with the hydrophilic film occurs to lower the hydrophilicity. The aluminum material on which the corrosion resistant film is formed is washed with water. Washing with running water
It is preferable to carry out for about 10 to 30 seconds.

Alternatively, treatment with a zirconium-based treatment agent may be used. Examples of the zirconium-based treatment agent include a mixture of polyacrylic acid and zircon fluoride. The amount of Zr in this film is 0.1-40 m
It is g / m ² . Similar to Cr, when Zr is less than 0.1 mg / m ² , corrosion resistance is insufficient, and when it exceeds 40 mg / m ² , hydrophilicity is rather deteriorated. When the zirconium-based treatment is superposed on the chromate treatment, the effect is further enhanced.

Further, by applying a phenolic primer coating after the degreasing treatment, better corrosion resistance can be imparted.
Resol-type water-soluble phenolic resin (prepolymerized with phenol and formalin under an alkaline catalyst) is preferable for this, and for example, Guntopei Chemical Co., Ltd.'s Resitop PL-2761, P
L-2717, Arakawa Chemical Co., Ltd. Tamanol 721,722, etc. can be used. The phenolic primer may contain a melamine resin in addition to the phenol resin. As the melamine resin, a methylated, ethylated and / or butylated water-soluble melamine resin is preferable, and the content thereof is 50% by weight or less based on 50 to 100% by weight of the phenol resin. In addition, an acrylic resin or the like can be mixed in order to improve workability such as bending workability and coating workability. After coating, the phenol resin primer is baked at a temperature of 180 to 280 ° C for 10 seconds to 1 minute. The coating is preferably in the range of 0.5 to 2 g / m ^2, it is insufficient in corrosion resistance and less than 0.5 g / m ^2, not only the heat exchange rate is lowered if it exceeds 2 g / m ^2, high cost .

A hydrophilic surface treatment material is applied onto the aluminum material that has been subjected to the above-described base treatment. For this, a roll coating method, a dipping method, a spraying method, a brush coating method and the like are possible. For example, in the case of the roll coating method, after coating, the temperature is 150 to 240 ° C for 10 seconds to 1
A hydrophilic film is obtained by drying for a minute. The film thickness of the hydrophilic film is 0.05 to 0.5 g / m ^2, an insufficient hydrophilicity is less than 0.05 g / m ^2, and at the same time increases the cost exceeds 0.5 g / m ^2, commensurate therewith The effect cannot be improved.

〔Example〕

 The present invention is described in more detail by the following examples.

Examples 1 to 5 After degreasing an aluminum plate, a zirconium-based surface treatment material (“Arodin 1690/1691”, manufactured by Nippon Paint Co., Ltd.) was applied by a bar coating method, dried at 150 ° C. for 15 seconds, and Zr was 5
A mg / m ² corrosion resistant film was formed.

Next, a hydrophilic surface treating agent containing sodium and ammonium salts of carboxymethyl cellulose having the composition shown in Table 1 and N-methylol acrylamide is applied by a bar coating method and dried at 240 ° C. for 30 seconds to make it hydrophilic. A film was formed. The film thickness of the hydrophilic film was 0.2 g / m ² . The hydrophilic surface treating agent contains sodium alkyldiphenyl ether disulfonate as a surfactant in a ratio of 5 parts by weight to 100 parts by weight of the above essential components, and a benzimidazole compound and a nitrogen-containing agent as a fungicide. The sulfur-based compound was contained in a ratio of 0.25 parts by weight.

An odor test, a water solubility test, a water contact angle (hydrophilicity) test and a corrosion resistance test were performed on each of the obtained hydrophilic coatings as follows.

(1) Odor test An odor test was conducted by directly sniffing each hydrophilic film-formed aluminum plate (hereinafter simply referred to as a sample). The evaluation criteria are as follows.

◎: No odor was felt ○: Almost no odor was felt △: Odor was felt clearly ×: Strong odor was felt (2) Water solubility Solubility Each sample was immersed in tap water for 24 hours, and the amount of film before and after immersion was measured. The water dissolution rate was calculated by the following formula.

Water dissolution rate = [(initial amount of film−amount of film after soaking for 24 hours) / initial amount of film] × 100 The evaluation criteria for water solubility are as follows.

Water dissolution rate ◎: Less than 10% ○: 10% or more and less than 30% △: 30% or more and less than 50% ×: 50% or more (3) Hydrophilic sustainability test Each sample was run under running water for 17 hours (flowing water 5 / hour, After repeating a cycle of exposing the dried hydrophilic film to tap water) for 7 hours and drying at 80 ° C. for 5 hours, the contact angle of water droplets was measured as follows.

Measurement of Contact Angle of Water Droplet The sample was placed horizontally, 5 ml of pure water was dropped, and the contact angle was measured with a goniometer. The evaluation criteria of the contact angle are as follows.

Contact angle ◎: Less than 20 ° ○: 20 ° or more and less than 30 ° △: 30 ° or more and less than 40 ° ×: 40 ° or more (4) Corrosion resistance test Each sample was subjected to a salt spray test of 500 based on JIS-Z-2371. After that, the corrosion resistance was evaluated by the area ratio of white rust generation on the flat surface.

White rust occurrence area ratio ◎: 0 ○: more than 0% and less than 10% △: 10% or more and less than 50% ×: 50% or more The results are shown in Table 1.

Example 6 A hydrophilic film was formed under the same conditions as in Example 1 except that the Zr content of the zirconium-based film formed by Alodin 1690/1691 was 0.1 mg / m ² and the composition of the hydrophilic surface treatment agent was as shown in Table 1. Formed and subjected to the same tests. The results are shown in Table 1.

Example 7 A hydrophilic film was formed under the same conditions as in Example 6 except that the Zr content of the zirconium-based film formed by Alodin 1690/1691 was changed to 40 mg / m ² and the same test was performed. The results are shown in Table 1.

Examples 8 to 10 In Example 6, the amount of Zr by Alodin 1690/1691 is 2 mg.
/ m ² of Zr-based corrosion resistant film is formed, then Alodin 407/47
Phosphoric acid chromate treatment (manufactured by Nippon Paint Co., Ltd.) was performed to form chromate-based corrosion resistant coatings having Cr amounts of 3 mg / m ² , 20 mg / m ² and 50 g / m ² , respectively. A hydrophilic film was formed on it with a hydrophilic surface treating agent having the composition shown in Table 1.
The test results are also shown in Table 1.

Examples 11 to 13 In Examples 8 to 10, the amount of Cr was 3 mg / m ² , 20 mg / m ² and 50 m directly by allodynes 407/47 without forming a Zr-based corrosion resistant coating by allodynes 1690/1691, respectively.
A chromate film of g / m ² was formed, and a hydrophilic film having the same composition as in Example 6 was formed thereon. The test results are shown in Table 1.

Examples 14 to 16 In Examples 11 to 13, instead of allodine 407/47, allodine was used as a chromium chromate chemical conversion treatment agent.
Using 600, the Cr content was 3 mg / m ² , 20 mg / m ² and 50 respectively.
A corrosion resistant film and a hydrophilic film were formed in the same manner except that a mg / m ² chromate film was formed. The test results are shown in Table 1.

Examples 17 and 18 NR Alcoat as phenol resin-based primer paint
450 (manufactured by Nippon Paint Co., Ltd.)
After forming 0.5 g / m ² and 2.0 g / m ² of primer, a hydrophilic film having a thickness of 0.2 g / m ² was formed by using a hydrophilic surface treating agent having the same composition as in Example 6. The same test as described above was performed on the obtained hydrophilic film. The results are shown in Table 1.

Example 19 A hydrophilic film was formed in the same manner as in Example 2 except that potassium salt was used instead of sodium salt of carboxymethyl cellulose. The same test was performed on the obtained hydrophilic film. As a result, the odor was ⊚, the water solubility was ⊚, the water contact angle was ⊚, and the corrosion resistance was ∘.

Comparative Examples 1 to 8 A zirconium-based corrosion-resistant coating (Zr amount 5 mg / m ² ) was formed on a degreased aluminum plate with Alodin 1690/1691, and a hydrophilic surface treatment agent having the composition shown in Table 2 was used to make it hydrophilic. Formed a protective film. The same test as in Example 1 was performed on the obtained hydrophilic coating of each sample. The results are shown in Table 2.

[Effects of the Invention] As described above, the hydrophilic film formed by the hydrophilic surface treating agent of the present invention not only has good hydrophilicity and water solubility resistance, but also significantly suppresses odor. Also, since it has good corrosion resistance, it is suitable for hydrophilic treatment of aluminum fin materials for heat exchangers.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location C08L 1/26 LAM C09D 5/08 PQC

Claims (9)

[Claims] 1. A sodium salt and / or potassium salt of carboxymethyl cellulose 5 to 25 parts by weight, an ammonium salt of carboxymethyl cellulose 25 to 50 parts by weight, and N-
A hydrophilic surface treating agent, characterized by containing 25 to 70 parts by weight of methylol acrylamide. 2. The hydrophilic surface treating agent according to claim 1, wherein the ratio of sodium salt and / or potassium salt of carboxymethyl cellulose to ammonium salt of carboxymethyl cellulose is 0.1 to 1.0 by weight. Characteristic hydrophilic surface treatment agent. 3. The hydrophilic surface treating agent according to claim 2, wherein the total ratio of sodium salt and / or potassium salt of carboxymethyl cellulose and ammonium salt of carboxymethyl cellulose to N-methylol acrylamide is weight. And 0.43 to 3.0. A hydrophilic surface treatment agent. 4. A carboxymethylcellulose sodium salt and / or potassium salt in an amount of 5 to 25 parts by weight after a base treatment and an ammonium salt of carboxymethylcellulose.
25 to 50 parts by weight and N-methylol acrylamide 25 to 70
A surface treatment method for an aluminum material, comprising treating with a hydrophilic surface treatment agent containing 10 parts by weight. 5. The method according to claim 4, wherein a chromate chemical conversion treatment is performed as the base treatment. 6. The method according to claim 5, wherein the chemical conversion treatment is performed by using a phosphoric acid chromate-based or chromium chromate-based chemical conversion treatment agent. 7. The method according to claim 4, wherein a zirconium-based chemical conversion treatment is performed as the base treatment. 8. The method according to claim 4, wherein a zirconium-based chemical conversion treatment is further performed after the chromate-based chemical conversion treatment is performed as the base treatment. 9. The method according to claim 4, wherein the primer treatment is a phenol resin-based primer coating.