JPH0347570A - Hydrophilic treatment of aluminum fin coil material - Google Patents

Abstract

PURPOSE:To form a hydrophilic film to an aluminum fin coil material by applying a mixture of polyvinyl alcohol, a water-soluble polymer obtained by the homopolymerization or mutual copolymerization of a specific polymerizable monomer and a water-soluble crosslinking agent thereto. CONSTITUTION:Polyvinyl alcohol and/or a water-soluble derivative thereof are prepared. A water-soluble polymer obtained by the homopolymerization or mutual copolymerization of a polymerizable monomer having a carboxyl group, a sulfonic acid group or the like in its molecule or the copolymerization of said monomer and a nonionic monomer is also prepared. A mixed aqueous solution of polyvinyl alcohol, the water-soluble polymer and a water-soluble crosslinking agent is applied to the surface of an aluminium fin coil material and dried. By this method, a hydrophilic film excellent in hydrophilicity durability can be formed.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a method for anticorrosive and hydrophilic treatment of metal surfaces, particularly aluminum or aluminum alloy (hereinafter collectively referred to as aluminum) surfaces. , relates to anti-corrosion and hydrophilic surface treatment of aluminum fin coil materials used in aluminum heat exchangers.

(Prior art) As a surface treatment for the purpose of preventing white rust on aluminum materials conventionally used in aluminum heat exchangers made of aluminum or aluminum alloys, that is, aluminum fin coil materials in the pre-coating shown in Fig. 1. , anticorrosive oxide coatings, boehmite coatings, resin coatings, etc. have been applied, but the coating surfaces formed by these treatments have almost no water wettability, and are rather water repellent. In addition, chromate conversion coating treatment is also performed to prevent white rust. Although chromate conversion coatings have some water pitting properties in the initial stage of coating formation, sufficient wood-philicity cannot be obtained by chromate treatment alone. Furthermore, chromate conversion coatings tend to change from hydrophilic to hydrophobic over time, which poses a problem as coatings for heat exchanger fins.

On the other hand, most heat exchangers are designed to have as large a surface area per unit volume of the heat radiation section and cooling section as possible in order to improve the heat radiation or cooling effect, so the spacing between the fins is extremely narrow. Therefore, when used for cooling, moisture condenses on the surface of the heat exchanger, especially in the gaps between the fins, and the more hydrophobic the fins are, the more easily the condensed water becomes water droplets. This causes clogging, increases ventilation resistance, and reduces heat exchange efficiency.

In addition, the water droplets accumulated between the fins are easily blown away by the air blower of the heat exchanger, and cannot be received by the water droplet tray installed in the single part of the heat exchanger, polluting the vicinity of the heat exchanger with water.

Therefore, in order to prevent water droplets remaining in the fin gaps from causing clogging, a treatment has been proposed to impart hydrophilicity to the aluminum surface and improve water wettability.

Treatment methods to improve water wettability include water glass,
Various methods have been proposed in which hydrophilic compounds such as silica sol and organic compounds such as surfactants and water-soluble resins are used alone or in combination.

Among these methods, polyvinyl alcohol (hereinafter PV
The following methods are known as methods using A).

JP-A No. 55-99,976 describes ``Covering of metal surfaces with an inorganic-organic composite reactant consisting of water-dispersible silica, water-soluble or organic synthetic resin with water molecules and, in short, a reactive silane compound. A method for making a metal surface hydrophilic, which is characterized by This invention relates to a hydrophilic film-forming agent J for aluminum characterized by containing a molecular compound.

Furthermore, JP-A No. 62-235,477 relates to ``a hydrophilic film-forming agent for aluminum containing an alkali silicate, an inorganic hardening agent, and a water-soluble organic polymer compound.''

These include P as one of the organic polymer compounds that can be used.
Although VA is mentioned, it is also essential to use an inorganic hydrophilic agent such as silica or alkali silicate. However, when manufacturing heat exchangers by subjecting fins that have been hydrophilized using these inorganic hydrophilic agents to post-processing, such as ironing or hammering, the wear of the processing jig is accelerated. There's a big fish.

JP-A No. 62-80.495 discloses ``A fin material for a heat exchanger characterized in that a super absorbent resin layer is formed on the surface of the fin material body via an adhesive layer,'' JP-A No. 62-80 ．．
496 is a fin material J for a heat exchanger characterized by forming a mixed layer of an adhesive and a highly water-absorbent resin powder on the surface of the r-fin material main body. JP-A-62-129.366 is an r-fin material for water-based paints. This article relates to a method for aluminum fins characterized by containing a resin, a water-absorbing resin, and a surfactant. Examples of water-absorbing resins include saponified vinyl acetate-methyl acrylate copolymer, vinyl acrylate Alcohol copolymer systems are listed.

However, in these applications, the main component that imparts hydrophilicity is the water-absorbing resin, that is, the frame I! PVA is an insoluble water-absorbing resin powder with a structure, and PVA, which is mentioned in the former two, has these insoluble water-absorbing +! It is only used as a bracing agent for resin powder. Therefore, these processing agents are either a processing liquid with powder dispersed as described above, or a coating film is formed by scattering the powder on the adhesive, so it is necessary to apply it uniformly.
In particular, thin film coating is difficult.

Also, it's water absorbent! 1. When fat powder absorbs water, its volume expands significantly compared to its original volume. Therefore, it is necessary to use an organic solvent as a solvent, which poses a fire and work environment problem. Even when a mixed solvent is used, it is necessary to reduce the amount of water-absorbing resin powder used, resulting in a decrease in hydrophilicity.

JP-A No. 62-105.629 discloses that ``a corrosion-resistant film is formed on the surface of a thin aluminum plate, and the upper layer of the film is made of PVA.
This article relates to a heat exchanger fin material 1 characterized in that a coating layer consisting of an organic curing agent and an organic curing agent is formed, and melamine resin, urea resin, benzoguanamine 61 fat, etc. are listed as the organic curing agent.

(Problem to be Solved by the Invention) However, as shown in the comparative example of the present application, the crosslinked cured product of polyvinyl alcohol itself does not have very high wood-philicity, and therefore As mentioned above, the combined use of colloidal silica and alkali silicate has been proposed. However, as mentioned above, the combined use of these inorganic substances is not welcomed in terms of wear on the processing jig.

An object of the present invention is to provide a method for forming a film with excellent hydrophilicity and long-lasting hydrophilicity in anti-corrosion and hydrophilic surface treatment of aluminum fin coil materials used in aluminum heat exchangers.

The process of manufacturing an aluminum heat exchanger is shown in FIG. 1 with emphasis on hydrophilic treatment. There is a pre-coat case in which the fin coil material is degreased, a corrosion-resistant film is formed, and washed with water to make it hydrophilic, and then molded into a heat exchanger, and a post-coat case is in which the fin coil material is molded and then treated to make it hydrophilic. However, the present invention is directed to the former case of precoating, in which the fin coil material is subjected to parent wood treatment.

(Means for Solving the Problems) As mentioned above, the present invention aims to investigate a surface treatment agent that has a low inorganic content and maintains parent tree sustainability in order to reduce the degree of jig wear during post-processing. Proceed with the patent application 1986-98, 02
A patent application has been filed for a 2-in-1 aluminum hydrophilic treatment method. This uses an acrylamide-based water-soluble polymer as Pl within the scope of the patent application. As a result of further investigation, we developed a water-based hydrophilic treatment method that uses a polyvinyl alcohol-based water-soluble polymer as Pl to provide a film with excellent hydrophilicity and long-lasting wood parentage. It's from 〒.

In addition, the present invention relates to polyvinyl alcohol and/or its water-soluble derivative (P1); polymerizable polyvinyl alcohol and/or its water-soluble derivative (P1); Monopolymerization of monomers or salts of these monomers [these monomers are <I)] or mutual copolymerization of (I) and (or) nonionic monomers copolymerizable with (■) and (I) A water-soluble polymer (R2) which is ffF by copolymerization with; a water-soluble crosslinking agent (C
) is applied to the surface of the aluminum fin coil material or the aluminum fin coil material on which the chemical conversion film has been dripped and dried.

PVA and/or PVA derivatives shown in (P1) are polymers that can be represented by the general formula, and are usually water-soluble copolymers obtained by hydrolysis of vinyl acetate or copolymers thereof, or further It is a water-soluble polymer that can be turned blue by post-reaction. Here, R1 is 1'' or CH3. Although X will be described later, it is not limited to one type of ionic bamboo V1 substituent, but may be two or more types. Therefore m-+-n=100
In the case m=50-1001 preferably m=60-100
, most preferably m=70-100.

The water-soluble polymer represented by the above general formula is firstly a hydrolyzate of vinyl acetate homopolymer, generally PVA.
Examples include those commercially available as . In other words, it is a polymer represented by C13, and m=9 depending on the degree of hydrolysis.
9 to 100 Completely saponified products m-90 to 99 Semi-completely saponified products m-70 or less These are called partially saponified products.

PVA derivatives are generally known as anion-modified PVA, cation-modified PVA, active methylene-modified PVA, etc., but the point is that they can be used as long as they are water-soluble bamboo in addition to P and C within the range of the general formula mentioned above. . For example, examples of anionic modification include acrylic acid, methacrylic acid,
Maleic anhydride, vinyl sulfonic acid, methacryloxyethyl phosphate, acrylic acid, etc. contain carboxyl groups, sulfone M groups, phosphonic acid groups, or can be converted into these groups by hydrolysis. Examples include hydrolyzates of copolymers of polymerizable monomers and vinyl acetate, and sulfonic acid esters and phosphoric acid esters of PVA.

A reaction product of PVA and diketene is known as active methylene-modified PvΔ.

Of course, in addition to the above two enomers, it is also possible to copolymerize styrene, acrylonitrile, vinyl ether, and other nonionic polymerizable monomers to the extent that they do not impair water solubility; This does not preclude the use of a co-combination of Φ or more with vinyl acetate.

The molecular weight of (P1) is preferably 5.000 or more, and 5.0
00 or less, especially when the hydrophilicity is high, it is necessary to increase the crosslinking agent ratio in order to make it non-water soluble. Further, in order to suppress high viscosity and stringiness during coating, it is appropriate that the molecular weight is 2 million or less, preferably 1 million or less.

As the water-soluble crosslinking agent (C), water-soluble blocked polyisocyanates and/or water-soluble bamboo polymethylol, polyglycidyl, boriasilicyl compounds, and aldehydes can be used.

A specific example of this is polyisocyanate blocked with NaHSO3 (e.g. Elastron manufactured by Dai-Kogyo Seiyaku).
Organic crosslinking agents such as mebrol melamine, mebrol urea, methylolated polyacrylamide, diglycidyl ether of polyethylene oxide, diarylylated polyethylene A oxide, and glycidyl acidyl can be used.

The amount of crosslinking agent (C) used varies depending on the type of crosslinking agent, but in terms of boat fishing, the amount of PVA-based polymer (P1) used
For every 100 suspended parts, 1 to 400 suspended parts, preferably 5 to 200 suspended parts, and most preferably 10 to 100 suspended parts are used.

Next, (P,2), that is, a carboxyl group in the molecule,
Specific examples of water-soluble polymers and copolymers of monomers or salts thereof having ionic groups such as sulfonic acid groups and phosphonic acid groups will be explained. These monomers are (
Ionic monomers shown as monomers for copolymerization of P1)
7-, such as acrylic acid, methacrylic acid, itaconic acid,
Maleic acid, polysulfonic acid, sulfoethyl acrylate, sulfoethyl methacrylate, N-methylenesulfonic acid acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, styrenesulfonic acid, etc., or their salts can be used, and these monomers can be Coalescing and copolymers can be used. In the case of a copolymer, in order to achieve the object of the present invention, the copolymerization R of nonionic monomers such as styrene, (meth)acrylic ester, vinyl acetate, etc. should be 40 mol% or less, preferably 20% or less. It is preferable to stop at

It is also possible to use monomers such as polymers of acid halides, for example (meth)acrylic acid chloride, which are subsequently hydrolyzed to give poly(meth)acrylic acid.

The molecular weight of P2 is i. ooo or more, preferably 3,000 or more is used.

The solvent is mainly water, but this does not preclude the combined use of water-soluble solvents such as alcohol, ketone, and cellosolve in order to control the drying rate and improve the condition of the coating film. The amount of P2 added is P
10 to 1000 parts by weight per 1100 parts by weight, preferably 50 to 800 parts by weight, most preferably 150 to 6 parts by weight.
Although the stability of the coating solution at 0.00 parts by weight differs depending on the composition, it is necessary to avoid using the amphoteric polymer near the iso-point because precipitation and separation of the polymer will occur.

From the viewpoint of stability, it is preferable to keep isocyanate-based crosslinking agents on the acidic side, and methylol, glycidyl, and aziridyl-based crosslinking agents on the neutral to alkaline side.

In addition, rust inhibitors, fillers, coloring agents, surfactants, antifoaming agents, leveling agents, antibacterial and antifungal agents, etc.
It can be added within a range that does not impair film performance.

As the coating method, dipping, spraying, rolling, flow coating, etc. are used.

Concerning the concentration and viscosity, an appropriate one is selected depending on the coating method used, desired film thickness, etc. The coating thickness was set at 0.05 to increase thermal efficiency and contribute to corrosion resistance.
It is preferably from microns to 10 microns or less, preferably from about 0.2 microns to 2 microns.

Aluminum T is degreased in advance, and a-grained cloth or,
Boehmite treatment, chromate treatment! l! (However, in the case of direct application, it is effective to add chromic acid, dichromic acid, and their salts.) Also, apply a suitable brimer such as TOP-3978.
[The hydrophilic treatment of the present application may be performed after applying Nippon Parkerine Jig Kyusei 1 or the like.

Drying is generally carried out at a temperature of (90) to (300)'C1, more preferably (100) to (250)C.

(Function) The paint film obtained by the method of the present invention has excellent corrosion resistance, hydrophilicity, and especially long-term hydrophilicity, and has excellent aluminum heat exchanger yI!
It is suitable as a surface coating for fin coil materials used in containers.

Although the mechanism of hydrophilicity, especially the persistence of hydrophilicity, due to the addition of the water-soluble polymer (P2) used in the present invention is not necessarily clear, the highly crosslinked network polymer due to the reaction between the PVA polymer (P1) and the crosslinking agent (C) Resin and (P2) are I P N
(Inter Panetrat+na14etV1
(0rk) structure, strongly hydrophilic (P2) always migrates to the film surface, or in some cases, the polar part dissolves and is washed away together with the tribute adhering to the film surface.
It seems to have the effect of improving hydrophilicity, especially the persistence of parent trees.

(Example) The present invention will be further explained below with reference to Examples.

The test method in the examples is as follows.

・Running water stability ■Contact angle The process of immersion in running water for 8H1 at room temperature, followed by drying at 80°C for 16HR is defined as 1 cycle, and the contact angle with water after 5C17CIO is shown.

The contact angle was measured by using a FACE contact angle tester CA-P model (manufactured by Kyowa Kaimen Kagaku) to measure the contact angle of a small water droplet with a diameter of 1 to 2 shoes placed on the sample surface.

・Running water stability ■Film survival rate It was immersed in running water for 3 days at room temperature and was expressed by the following formula.

Wo: 1- Ground treated aluminum plate dry heavy W1: I!
Water-treated aluminum plate dry simW2: Labor of parent-treated aluminum plate dried after soaking in running water for 3 days In the comparative examples and examples shown in Table 1, the hydrophilic treatment agent was applied directly to the aluminum plate, or the aluminum plate was pre-coated with the hydrophilic treatment agent. The board was subjected to the following surface treatment and then subjected to KXVA water treatment.

Lower 1t! 1) Chemically molded chromic chromate [AM-713<729/1 manufactured by Nippon Parriki Rising Co., Ltd.]
An aluminum plate was immersed in the solution No. 1 at 40° C. for 30 seconds, then washed with water and dried.

Surface treatment 2) Coating type chromate [Nihon Bariki Rising Co., Ltd. ['rOP-3978A]
An aluminum plate was immersed at room temperature in a solution of 125 g of agent B and 125 g of agent B (11 with water), dried for 1 minute, and then baked at 220 to 250° C. for 2 minutes to dry.

Surface treatment 3) Immerse the aluminum plate in a solution of chemically formed phosphoric acid chromate (AM-7028I agent 47y manufactured by Nippon Parriki Rising Co., Ltd. and 2 g of AC agent to 11 with water) at 40°C for 30 seconds. After that, it was washed with water and dried.

Surface treatment 4) Acrylic resin brusher Nippon Parriki Rising Co., Ltd. [TOP-3977-2 with bar coater #
No. 3 was used to give a coating weight of 1.0 to 1.2 g/TrL2, and the coating was baked at 190 to 200° C. for 10 seconds to dry.

The composition of the hydrophilic treatment agent is shown in Table 1. The dry skin weight ω of these hydrophilic treatment agent aqueous solutions is 300#±501t.
g/TrL2 Ninaru J: Sea urchin L 17 Coated on a aluminum plate, heated and dried at 170 to 200°C for 3 minutes, allowed to cool, coated with breath oil, molded, left for 2 days, and then coated with trichlorethylene. After washing and drying, its performance was measured.

The results are shown in Table 1.

The raw materials used to create the parent tree treatment agent are as follows.
The numbers in the table indicate the number of solid molecules fli.

(P) Polyvinyl alcohol and its deactivation (P-1) Degree of saponification 90 mol%, a) Molecule 1 a
,b 8 about 100,000 polyvinyl alcohol,b) 50,000 molecule reservation (Pl-2) diketene-treated polyvinyl alcohol molecule about 50,000 (Pl-3) Sulfone F [3 mol% containing polyvinyl alcohol molecule about 20,000 ( P2) Water-soluble polymer containing ionic functional group (P2-1
) Polyacrylic acid (P -2, b, c
) Sulfoethyl acrylate/acrylic acid copolymer Sulfoethyl acrylic Molecular loss rate content (mol%) a) 20 Approximately 4,000 b) 30 Approximately 80,000) 40 Approximately 80,000 (C) Crosslinking agent (C -1> Tetramethylolmelamine tetramedyl ether (C-2) Pentaethylene glycol diglycidyl ether (C-3) Sulfite 6!3 salt block polyether isocyanate prepolymer (isocyanate content 5.0 to 5. 5%) As seen in Comparative Example 1.2 and Example 1.2 in Table 1,
A film containing only a PVA polymer and a crosslinking agent without P2 has a high contact angle and cannot be called a hydrophilic film.

As seen in the comparison between Comparative Examples 3 and 4 and Example 3.4, P
Comparative Example 3, which does not contain VA-based polymers and uses only highly hydrophilic P2 and a crosslinking agent, and Comparative Example 4, which does not contain a crosslinking agent, have poor water resistance, and most parts of the film are resistant to water after being immersed in running water for 3 days. There is an influx.

In contrast, Examples 1 to 7 prepared at the expense of the applicant
Even after immersion in running water, there was almost no drifting of the constituent components of the various coatings, and the wood affinity was maintained at a high level.

(Effects of the Invention) Corrosion-preventing and hydrophilic surface treatment of aluminum fin coil material used in the aluminum heat exchanger of the present invention 1! i! 71
The film on the surface of the fin coil mill treated by the J method has excellent hydrophilicity and long-lasting hydrophilicity.

[Brief explanation of drawings]

FIG. 1 shows the manufacturing process of an aluminum heat exchanger.

Claims (1)

[Claims] (1) Polyvinyl alcohol and/or its water-soluble derivative (P_1); Polymer monomers having one or more groups selected from the group of carboxyl groups, sulfonic acid groups, and phosphonic acid groups in the molecule, or those monomers Salt of [These monomers (I
)] or copolymerization of (I) with each other and/or copolymerization of (I) with a nonionic monomer copolymerizable with (I) (P_2 ) and; Applying a mixed aqueous solution of (P_1) and (P_2) and a water-soluble crosslinking agent (C) mixable to the surface of the aluminum fin coil material or the aluminum fin coil material on which the chemical conversion film has been applied and drying it. Features a hydrophilic treatment method for aluminum fin coil material.