JPH04235772A - Post-treatment of fin material for heat exchanger made of aluminum having polyvinyl alcohol type hydrophilic film - Google Patents

Abstract

PURPOSE:To efficiently restore a hue before heating and drying by eliminating the hue change due to the heating and drying of the polyvinyl alcohol type hydrophilic film on the surface of the fin material for a heat exchanger made of aluminum. CONSTITUTION:The surface of the fin material for a heat exchanger made of aluminum is coated with a hydrophilic treatment agent containing one or more kind of a compound selected from polyvinyl alcohol and a water-soluble derivative thereof and the coated fin material is heated and dried to form a hydrophilic film to the surface of the fin material and the surface of this film is subjected to at least either one of post-treatments, that is, washing treatment (a), treatment by an aqueous solution of at least one kind of a compound selected from sulfuric acid, nitric acid, percarboxylic acid and alkali metal permanganate (b), ultraviolet irradiation treatment (c), combination treatment (d) of (a) and (c) and combination treatment (e) of (d) and (c).

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for post-treatment of fin materials for aluminum heat exchangers having polyvinyl alcohol-based hydrophilic coatings used in home and commercial room air conditioners.

[0002] In this specification, the term aluminum is used to include not only pure aluminum but also aluminum alloys.

0003

BACKGROUND OF THE INVENTION Conventionally, various methods have been proposed in which water-soluble organic polymers are used for hydrophilic treatment of fin materials for aluminum heat exchangers (hereinafter abbreviated as fin materials).

Among them, polyvinyl alcohol (hereinafter referred to as
As a hydrophilic treatment method using a hydrophilic treatment agent containing PVA (abbreviated as PVA), the following methods are known.

[0005] First, those that require the combination of PVA and an inorganic hydrophilizing agent such as silica or alkali silicate (for example, JP-A-55-99976, JP-A-60-101156, and JP-A-62 (Refer to Publication No.-235477).

[0006] Next, a method using an adhesive of insoluble water-absorbing resin powder using PVA (for example, JP-A-62-8
0495, and JP-A-62-80496).

[0007] Furthermore, there is a method in which PVA is used as the main component of a hydrophilic treatment agent (see, for example, JP-A-62-105629).

By the way, the present inventors have proceeded with the study of a treatment agent containing PVA and/or its water-soluble derivative that is hydrophilic and has good mold wear resistance during molding processing, and first developed an aluminum fin coil. We proposed a method for making the material hydrophilic.
A patent application has been filed for this (patent application Hei 1-18205
(see 6).

[0009]

[Problems to be Solved by the Invention] The hydrophilic treatment agent containing PVA and/or its water-soluble derivative, which the present inventors identified in the above-mentioned previously proposed invention, maintains excellent hydrophilicity over a long period of time. , which gives good mold abrasion resistance and adhesion to the coated object, but the hydrophilic treatment agent is
When a film is formed by heating and drying at temperatures above .degree. C., there is a problem in that the color tone of the film changes, resulting in poor appearance.

[0010] Here, if no surface treatment is performed before the hydrophilic treatment or if a colorless pretreatment such as boehmite is applied, the color tone of the film after the hydrophilic treatment will be slightly yellowish and blue pigment When an organic polymer resin base treatment is applied, the film becomes slightly greener than the original blue color.

[0011] In addition to the hydrophilic treatment according to the previously proposed invention, the present inventors also investigated known PVA-based hydrophilic treatment agents, but the same color change as described above was observed.

An object of the present invention is to solve the above-mentioned problems of the prior art, to eliminate the change in color tone of a PVA-based hydrophilic film caused by heat drying, and to efficiently restore the color tone to that before heat drying. An object of the present invention is to provide a method for post-treatment of an aluminum heat exchanger fin material having a polyvinyl alcohol-based hydrophilic film.

[0013]

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a method in which the surface of an aluminum heat exchanger fin material is made of polyvinyl alcohol and one or more water-soluble derivatives thereof. After forming a hydrophilic film on the surface of the fin material by coating it with a hydrophilic treatment agent containing a compound of (a) and drying it by heating,
water washing treatment, (b) treatment with an aqueous solution of at least one compound selected from alkali metal salts of sulfuric acid, nitric acid, percarboxylic acid, and permanganic acid, (c) ultraviolet irradiation treatment, (d) the above ( It has a polyvinyl alcohol-based hydrophilic film, characterized in that it undergoes any one treatment selected from the combination treatment of a) and (c), and (e) the combination treatment of (b) and (c) above. The summary is a post-treatment method for fin materials for aluminum heat exchangers.

[0014] Here, PVA and/or its water-soluble derivative has the general formula

[0015]

[Chemical formula 1]

The polymer represented by the following is usually a water-soluble copolymer obtained by hydrolysis of vinyl acetate or a copolymer thereof, or a water-soluble copolymer obtained by further post-reacting these.

[0017] Here, p is an integer of 50 to 100, m is 0
an integer of ˜50, and n is an integer of 0-50. Further, R1 is H or CH3.

When X is an anionic substituent containing at least one of a carboxyl group and a sulfonic acid group, examples include acrylic acid, methacrylic acid, maleic anhydride,
Anion-modified P that is a copolymer with vinyl sulfonic acid, etc.
One example is VA. Also included are those that become anionic upon hydrolysis, such as methacryloxyethyl phosphate and acrylic ester.

When X is a cationic substituent, it is any one of primary to tertiary amino groups or a quaternary amine salt. Next, examples of the PVA type include active methylene-modified products, and reaction products of PVA and diketene, such as acetoacetylated PVA. Moreover, X includes any one type or two or more types of the above-mentioned groups.

Water-soluble derivatives of PVA include, in addition to the structures described above, those in which styrene, acrylonitrile, vinyl ether, and other nonionic polymerizable monomers are copolymerized to the extent that water solubility is not impaired.

[0021] PVA shown in the above structure, and/
The hydrophilic treatment agent containing PVA or a derivative thereof is PVA
This is a hydrophilic treatment agent containing a water-soluble organic polymer and a water-soluble organic crosslinking agent that can be mixed with , and/or a derivative thereof.

Here, the water-soluble organic polymer has a carboxyl group, a sulfonic acid group, a phosphonic acid group, or a salt thereof, a primary to tertiary amino group, a quaternary amine group, or a polyoxyethylene group in the molecule. , a water-soluble organic polymer having at least one kind of hydrophilic group such as hydroxyl group, amide group, etc., such as acrylic acid, methacrylic acid, itaconic acid, maleic acid,
Individual polymerizable monomers such as vinyl sulfonic acid, styrene sulfonic acid, sulfoethyl acrylate, acrylamide, N-methylenesulfonic acid acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, N-methylolacrylamide, ethyleneimine, dimethyldiallylammonium, etc. Polymers or copolymers, water-soluble nylons obtained by condensation reactions, polyamides, epoxy-modified polyamides, water-soluble polyesters, other natural water-soluble polysaccharides such as starch, cellulose, and their derivatives, homopolymers of ethylene oxide Examples include water-soluble alkyd resins such as polyethylene oxide, a copolymer of ethylene oxide and propylene oxide, and an ammonium salt of a copolymer of trimellitic anhydride and neopentyl glycol.

Examples of the water-soluble organic crosslinking agent include water-soluble blocked polyisocyanates, water-soluble polymethylol, polyglycidyl, polyaziridyl compounds, and aldehydes, such as sodium bisulfite blocked isocyanates, methylolmelamine, Examples include methylol urea, methylolated polyacrylamide, diglycidyl ether of polyethylene oxide, and diaziridylated polyethylene oxide glyoxal.

[0024] In these hydrophilic treatment agents containing PVA and/or its derivatives, it is possible to add inorganic hydrophilic agents such as alkali silicate, silica sol, alumina sol, etc. to the extent that they can be mixed. In addition, rust preventives, fillers, colorants, surfactants, antifoaming agents, leveling agents, antibacterial and antifungal agents, etc. can be added as long as they can be mixed.

Post-processing in the present invention includes (a)
Simply cleaning with water such as city water, industrial water, deionized water, etc. is effective, but (b) treatment with a dilute solution of sulfuric acid, nitric acid, percarboxylic acid, or permanganate alone in water is more effective. In addition, (c) irradiation with ultraviolet rays in the atmosphere is also effective, (d) a combination treatment of (a) and (c) above, and (e) a combination treatment of (b) and (c) above. If you combine them like this, the effect will be even greater.

[0026] As for the post-treatment agent (b) above,
Sulfuric acid, nitric acid, percarboxylic acid, permanganate, etc., each in an amount of 0.001 to 10% by weight, preferably 0.01 to 10% by weight.
A water dilution containing a concentration of 5% by weight is used.

[0027] Here, the concentration of sulfuric acid etc. is 0.001% by weight.
If the concentration is less than 10% by weight, the effect of color recovery will be small, and if the concentration of sulfuric acid exceeds 10% by weight, the physical properties of the film will deteriorate due to oxidative decomposition, which is not preferable.

[0028] The percarboxylic acids mentioned above include peracetic acid, performic acid,
perbenzoic acid, perp-nitrobenzoic acid, monoperphthalic acid,
Pertrifluoroacetic acid, etc.

[0029] Permanganates include potassium permanganate and sodium permanganate.

The present invention is applied to a fin material having a film formed with a hydrophilic treatment agent containing PVA and/or a water-soluble derivative thereof, and the pretreatment for coating the hydrophilic treatment agent is particularly important. It is not limited.

For example, when a chromic acid-based chemical conversion treatment such as chromate chromate or chromate phosphate is applied, or after a non-chromium-based chemical conversion treatment, or without any of these chemical conversion treatments, organic The post-treatment method of the fin material of the present invention can be applied even when a polymeric base treatment is applied, or when a film is formed directly on a chemical conversion film or on the base surface without such a base treatment. It is.

[0032]

[Operation] The present inventors studied the mechanism of film discoloration when a hydrophilic treatment agent containing PVA and/or its water-soluble derivative is applied to the surface of a fin material and then heated and dried to form a film. As a result, P in the film composition components
It has been found that when heated, VA and/or its water-soluble derivative undergoes intramolecular dehydration and autooxidation to produce a conjugated polyene, which causes discoloration of the film.

The effects of the treatment in the post-treatment method of the fin material of the present invention include hydration of the generated double bonds with water, sulfuric acid or diluted nitric acid, epoxidation with percarboxylic acid, and alkaline permanganate. Hydroxylation with metal salts eliminates or significantly reduces double bonds that cause discoloration, and ultraviolet irradiation has the effect of promoting the above reaction. Furthermore, even if the heat-dried PVA film was directly irradiated with UV rays without the above-mentioned cleaning, an effect was observed, and this is presumed to be due to promoting the hydration reaction of the double bonds due to moisture in the atmosphere. be done.

[0034] The above action solves the problem of uneven appearance due to color change of the film after applying a hydrophilic treatment agent containing PVA and/or its water-soluble derivative to the surface of the fin material and then heating and drying it. be done.

[0035]

[Examples] Next, examples of the present invention will be explained together with comparative examples.

Example 1 A coil material (JIS A1100-H26) with a thickness of 0.11 mm was used as the aluminum fin material, and an alkaline degreaser (FC- manufactured by Nippon Parkerizing Co., Ltd.) was used.
After degreasing the coil material by spraying a 20 g/1 aqueous solution of 4306) at 70°C for 10 seconds, color the organic polymer undercoat (TOP-3978 agent manufactured by Nippon Parkerizing Co., Ltd.) as a base treatment. Pigment (TOP-3977-TBL2 manufactured by Nippon Parkerizing Co., Ltd.)
was added using a roll coater and coated with 200~
It was dried by heating at 250°C for 10 seconds.

Next, as a hydrophilic treatment, 50 parts of carboxyl group-modified PVA (Gosenal T manufactured by Nippon Gosei Kagaku Kogyo Co., Ltd.), 40 parts of polyacrylic acid, 9 parts of sulfite block polyether isocyanate prepolymer, and industrial grade An aqueous solution consisting of 1 part of phosphoric acid is coated with a roll coater.
The coating was applied so that the dry film weight was 200±50 mg/m 2 and dried at 230 to 280° C. for 10 seconds.

Furthermore, as a post-treatment, spray pressure: 1 to
1.8 kg/cm2, spray flow rate: 3 to 7 liters/min, time: 5 to 10 seconds, distance from nozzle tip to treated fin material: 20 to 300 mm, nozzle angle with treated surface: 30 to 90 degrees. It was spray washed with water and dried at 80°C.

Example 2 Using the same aluminum coil material as in Example 1 above,
Degreasing, surface treatment, and hydrophilic treatment were performed in the same manner as in Example 1. For post-treatment, an 80W/cm mercury lamp with a light emission length of 350mm (H2800L manufactured by Toshiba Ricetex Corporation) was used.
/2) was used to perform ultraviolet irradiation (irradiation distance to the treated fin material: 100 mm, irradiation time: 10 seconds).

Example 3 Using the same aluminum coil material as in Example 1, the same degreasing, surface treatment, and hydrophilic treatment as in Example 1 were carried out.

As a post-treatment, spray washing was carried out (the conditions were the same as in Example 1), and before drying, ultraviolet ray irradiation (the conditions were the same as in Example 2) was carried out, followed by drying at 80°C.

Example 4 Using the same aluminum coil material as in Example 1, the same degreasing and surface treatment as in Example 1 were carried out, followed by 70 parts of saponified polyvinyl alcohol 90% and N-methylenesulfonic acid acrylamide. An aqueous solution consisting of 20 parts of a homopolymer of 1 and 10 parts of tetramethylolmelamine tetramethyl ether was applied to give a dry film weight of 200±50 mg/m 2 and dried by heating at 230 to 280°C.

As a post-treatment, a 1% by weight peracetic acid aqueous solution was spray applied (the conditions were the same as in the case of spray washing in Example 1), and after washing with water to remove excess acid, the material was dried at 80°C. .

Example 5 Using the same aluminum coil material as in Example 1, the same degreasing, surface treatment, and hydrophilic treatment as in Example 4 were performed. Post-treatment was carried out by spraying a 0.1% by weight potassium permanganate aqueous solution (the conditions were the same as in the case of spray washing in Example 1), washing with water to remove excess salt, and drying at 80°C. did.

Example 6 Using the same aluminum coil material as in Example 1, the same degreasing, surface treatment, and hydrophilic treatment as in Example 4 were carried out.

As a post-treatment, a 3% by weight sulfuric acid aqueous solution was spray applied (the conditions were the same as in the case of spray washing in Example 1), and ultraviolet rays were irradiated (the conditions were the same as in Example 2).
After washing with water to remove excess acid, the sample was dried at 80°C.

Comparative Example 1 Using the same aluminum coil material as in Example 1, degreasing, surface treatment, and hydrophilic treatment were carried out in the same manner as in Example 1, except for the post-treatment.

Comparative Example 2 Using the same aluminum coil material as in Example 4, degreasing, surface treatment, and hydrophilic treatment were carried out in the same manner as in Example 1, except for the post-treatment.

Note that Examples 1 to 6 and Comparative Examples 1 to
The results of 2 are summarized in Table 1.

Measurement method Measurement samples were sampled for the fin material test pieces prepared in Examples 1 to 6 and Comparative Examples 1 to 2, and a color difference meter (manufactured by Minolta Co., Ltd., CR -200), the b value (blue - → + yellow) was measured, and the change in color tone over time (immediately after post-processing, left indoors 3
1 day, 7 days, and 14 days).

[0051]

[Table 1]

Explanation of Measurement Results The b values shown in Table 1 above indicate the degree of blue to yellow color tone, with blue indicating a negative value and yellow indicating a positive value.

[0053] In addition, Examples 1 to 6 and Comparative Examples 1 to
B of the fin material that has been subjected to surface treatment in the same manner as in 2.
The value is -2, which is the original color tone due to the blue pigment added to the base treatment agent.

First, in Comparative Example 1 and Comparative Example 2 in Table 1,
Immediately after applying the hydrophilic treatment agent and heating and drying, the b value was +1 in Comparative Example 1 and +2 in Comparative Example 2, indicating that the color tone was changing toward yellow. If these are left indoors, the original b value (
-2).

[0055] Compared to these, the b values of Examples 1 to 6 are as follows.
As shown in Table 1, -1.5 to +0.5 immediately after post-processing.
After being left indoors for 3 days, the color tone recovered to the original b value (-2) in all examples, and the color tone change caused by heating and drying of the PVA-based hydrophilic film was quickly canceled and the heating It is clear that the color tone before drying can be efficiently restored.

[0056]

[Effects of the Invention] As described above, the post-treatment method of the fin material for an aluminum heat exchanger having a polyvinyl alcohol-based hydrophilic film of the present invention is such that the surface of the fin material for an aluminum heat exchanger is coated with polyvinyl alcohol and its aqueous solution. After forming a hydrophilic film on the surface of the fin material by coating with a hydrophilic treatment agent containing one or more compounds selected from chemical derivatives and heating and drying, the surface of the film is (a) washing with water; (b) treatment with an aqueous solution of at least one compound selected from alkali metal salts of sulfuric acid, nitric acid, percarboxylic acid, and permanganic acid; (c)
The present invention is performed by performing any one treatment selected from ultraviolet irradiation treatment, (d) a combination treatment of the above (a) and (c), and (e) a combination treatment of the above (b) and (c). The post-treatment has the effect of canceling the change in color tone of the film that occurred during heat drying and efficiently restoring the color tone before heat drying.

Claims (1)

[Claims] Claim 1: The surface of an aluminum heat exchanger fin material is coated with a hydrophilic treatment agent containing one or more compounds selected from polyvinyl alcohol and its water-soluble derivatives, and then heated and dried. After forming a hydrophilic film on the surface of the fin material, the surface of the film is subjected to (a) washing treatment with water, (b) treatment with an alkali metal salt selected from sulfuric acid, nitric acid, percarboxylic acid, and permanganic acid. (c) ultraviolet irradiation treatment, (d) a combination treatment of (a) and (c) above, and (e) a combination treatment of (b) and (c) above. A method for post-treatment of a fin material for an aluminum heat exchanger having a polyvinyl alcohol-based hydrophilic film, the method comprising performing any one of the selected treatments.