JPH02107678A - Coating composition for heat-exchanger fin - Google Patents

Abstract

PURPOSE:To obtain the subject coating composition having excellent adhesivity to metallic material and giving a coating film having excellent water-resistance and mechanical properties by compounding two kinds of different block copolymers with a metal chelate-type crosslinking agent at specific ratios. CONSTITUTION:The objective coating composition is produced by compounding (A) a block copolymer composed of 5-35wt.% of glycidyl (meth)acrylate, etc., 65-95wt.% of a hydroxyalkyl (meth)acrylate, 70-95wt.% of a lower alkyl (meth) acrylate and 5-30wt.% of (meth)acrylic acid, (B) a block copolymer composed of 1-35wt.% of glycidyl (meth)acrylate, etc., 65-99wt.% of acryloyl morpholine, etc., 70-95wt.% of methyl methacrylate and 5-30wt.% of acrylic acid and (C) one or more kinds of metal chelate-type crosslinking agent of formula AlXnY3-n (X is 1-5C alkoxy; Y is R<1>COCH2COR<2>, etc.; R<1> and R<2> are 1-10C alkyl; n is 0, 1 or 2) at ratios (A:B:C) of (5-40):(60-95):(1-30).

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention provides an excellent coating for the fins of heat exchangers for air conditioners, which protects the surface and permanently maintains hydrophilicity and corrosion resistance. The present invention relates to a coating composition for heat exchanger fins for imparting strength.

[Conventional technology] Conventionally, aluminum fins for heat exchangers have been designed to prevent a decrease in ventilation resistance due to condensation water generated when operating an air conditioner.
Generally, its surface is subjected to hydrophilic treatment. For example, a method is known in which a hydrophobic acrylic resin paint or the like is coated with a composition in which a surfactant, silica, titanium oxide, etc. are added and dispersed (JP-A-55-99987, JP-A-59-1).
70170 and Japanese Patent Application Laid-Open No. 61-343865)
.

In addition, a method of forming a film by chemical conversion treatment such as boehmite treatment is also known (Minao Izumi, Shinji Sasakuma, "Rust Prevention Management J Vol. 16.21-27, 1981).
.

[Problems to be Solved by the Invention] However, the above-mentioned conventional method has several practical problems. That is, the former method has excellent hydrophilicity in the initial stage, but after the surfactant is removed by condensed water, the hydrophilicity is considerably reduced. In addition, since it contains silica, it causes wear of processing tools, etc., and there is a problem that it can only be passed through a so-called post coat that is applied after processing the aluminum fin.

Furthermore, the latter method has problems in that productivity is poor and corrosion resistance is not necessarily sufficient.

The purpose of the present invention is to impart sufficient long-lasting hydrophilicity to the aluminum surface, as well as impart corrosion resistance and adhesion to the aluminum surface, as well as to prevent the wear of processing tools and the like, and to provide the aluminum surface with sufficient durability before forming the fin material. It is an object of the present invention to provide a coating composition for heat exchanger fins that can be used as a pre-coat type coating composition.

[Means for Solving the Problems] In order to achieve the above object, the present inventors have completed the present invention as a result of intensive studies.

That is, the coating composition for heat exchanger fins of the present invention consists of the following components (a), (b), and (C), and the solid content weight ratio is (
a): (b): (c) = 5-40: 60-95
:1 to 30 is adopted.

(a) Hydrophilic polymer portion consisting of 5 to 35% by weight of structural units based on glycidyl (meth)acrylate or N-methylol (meth)acrylamide, and 65 to 95% by weight of structural units based on hydroxyalkyl (meth)acrylate. and structural unit 7 based on lower alkyl (meth)acrylate
A block copolymer (hereinafter referred to as A polymer) consisting of a hydrophobic polymer portion consisting of 0 to 95% by weight and 5 to 30% by weight of structural units based on (meth)acrylic acid.

(b) Structural units 1 to 35 based on glycidyl (meth)acrylate or N-methylol(meth)acrylamide
i (3%, a monomer selected from acryloylmorpholine, N-vinylpyrrolidone, N,N-dimethylacrylamide, polyethylene glycol monomethacrylate (
A hydrophilic polymer portion consisting of 65 to 99% by weight of structural units based on one or more types of crosslinkable monomers (hereinafter referred to as crosslinkable monomers), 70 to 95% by weight of structural units based on methyl methacrylate, and 70 to 95% by weight of structural units based on acrylic acid. A block copolymer (hereinafter referred to as B) consisting of a hydrophobic polymer portion consisting of 5 to 30% by weight of structural units.
polymer).

(c) General formula Aj? XnY3-n C In the formula, X is an alkoxy group having 1 to 5 carbon atoms, Y is RICO, CH2C0R
2 or R3COCH2COOR4, R1, R2,
R3 and R4 are alkyl groups having 1 to 10 carbon atoms,
n is Oll or 2] and the general formula TiXnY4-n
In formula C, X is an alkoxy group or hydroxyl group having 1 to 5 carbon atoms, and Y is QC(CH3)CHCOCH3, QC2H4N
(C2H4OH), OCR(CH3)COOH, where n is 0 or an integer from 1 to 4]
species or two or more metal chelate type crosslinking agents.

Moreover, it is a suitable means to blend a block copolymer (hereinafter referred to as C polymer) consisting of polyethylene oxide and polypropylene glycol as component (d) into the above-mentioned coating composition.

[Detailed Description of Means] Each component of the coating composition for heat exchanger fins will be described below.

First, polymer A, which is component (a), will be explained.

The hydrophilic polymer portion is glycidyl (meth)acrylate [
In this specification, acrylic and methacrylic are collectively referred to as (meth)acrylic] or 5 to 35% by weight of structural units based on N-methylol (meth)acrylamide and 65 to 95% by weight of structural units based on hydroxyalkyl (meth)acrylate. It consists of %. As the hydroxyalkyl (meth)acrylate, hydroxymethyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, etc. are used. If the former structural unit is less than 5% by weight or the latter structural unit is more than 95% by weight, the corrosion resistance and adhesion of the resulting coating will decrease;
If the content of the latter structural unit is more than 5% by weight or less than 65% by weight, the adhesion of the resulting film will decrease.

The hydrophobic polymer portion consists of 70 to 95% by weight of structural units based on lower alkyl (meth)acrylate and 5 to 30% by weight of structural units based on (meth)acrylic acid.

Examples of the lower alkyl in the lower alkyl (meth)acrylate include straight or branched alkyl having 1 to 4 carbon atoms. If the former structural unit is less than 70% by weight or the latter structural unit exceeds 30% by weight, the corrosion resistance and adhesion of the resulting coating will decrease, and if the former structural unit exceeds 95% by weight or the latter structure If the unit content is less than 5% by weight, the corrosion resistance of the coating will decrease.

Next, the B polymer serving as the component (b) will be explained.

The hydrophilic polymer portion has 1 to 35% by weight of structural units based on glycidyl (meth)acrylate or N-methylol(meth)acrylamide and 65 to 99 structural units based on one or more of the above-mentioned crosslinkable monomers. It consists of % by weight.

The former structural unit is less than 1% by weight or the latter structural unit is 9% by weight.
If it exceeds 9% by weight, the corrosion resistance and adhesion of the resulting coating will decrease, and if the former structural unit exceeds 35% by weight or the latter exceeds 65% by weight, the adhesiveness of the coating will decrease.

The hydrophobic polymer portion consists of 70 to 95% by weight of structural units based on lower alkyl (meth)acrylate and 5 to 30% by weight of structural units based on (meth)acrylic acid.

As the lower alkyl (meth)acrylate, those similar to those of the above-mentioned A polymer can be used. The structural unit of the former is 70
If the content of the latter structural unit exceeds 30% by weight, the corrosion resistance and adhesion of the resulting coating will decrease, and if the content of the former structural unit exceeds 95% by weight or the content of the latter structural unit exceeds 5% by weight. In this case, the corrosion resistance of the coating decreases.

The block copolymer consisting of a hydrophilic polymer part and a hydrophobic polymer part of the present invention can be synthesized by a conventionally known method.
In particular, from the viewpoint of ease of industrial productivity and versatile performance, polymeric peroxides having two or more peroxy bonds in one molecule, polyazo compounds having two or more azo bonds in one molecule, and radical It is preferable to produce by a radical polymerization method using a polymerizable group-containing peroxide. As the polymerization method, ordinary bulk polymerization method, suspension polymerization method, solution polymerization method, emulsion polymerization method, etc. are employed.

Next, as a typical production example of the block copolymer of the present invention, a polymerization method using polymeric peroxide as a polymerization initiator will be described below. First, when a vinyl monomer that forms a hydrophilic polymer is polymerized using polymeric peroxide, a peroxy-bonded gold-visible aqueous vinyl polymer with peroxy bonds introduced into the chain is obtained. When a vinyl monomer forming a hydrophobic polymer is added and polymerized, the peroxy bonds are cleaved at the peroxy bonds contained therein, and a block copolymer can be efficiently obtained.

As the metal chelate crosslinking agent serving as the component (C), one or more compounds represented by the above general formula are used,
Among them, aluminum monoacetylacetonate bis(ethylacetoacetate), aluminum tris(acetylacetonate),
Diisopropoxybis(acetylacetonate)titanium and tetra-n-butoxytitanium alone or in combination are suitable.

The C polymer, which is component (d), is a block copolymer of polyethylene oxide and polypropylene glycol, and the average molecular weight of polypropylene glycol in the block copolymer is 13,000 to 10,000. This C polymer is suitable for exhibiting hydrophilicity and sustainability of hydrophilicity.Furthermore, this C polymer can be easily synthesized by a known method.

The blending ratio of each component (a) to (d) above is such that the solid content coulometric ratio is (a): (b): (c) = 5 to 40:60.
~95:1 to 30, or when (d, ) components are blended, (a): (b): (c): (d)
=5-40:60-95:1-30;1-40.

If component (a) is less than 5 parts by weight, the corrosion resistance and adhesion of the resulting coating will be reduced, and if it exceeds 40 parts by weight, the hydrophilicity of the coating will be reduced. If component (b) is less than 60 parts by weight, the hydrophilicity of the coating will decrease, and if it exceeds 95 parts by weight, the corrosion resistance of the coating will decrease.6 If component (C) is less than 1 part by weight, crosslinking will be insufficient. The corrosion resistance and adhesion of the coating will decrease, and if it exceeds 30 parts by weight, the hydrophilicity of the coating will decrease. If component (d) is less than 1 part by weight, further improvement in hydrophilicity sustainability cannot be achieved;
If the amount exceeds 1 part by weight, the corrosion resistance and adhesion of the coating will be impaired.

Next, a method for coating the surface of the fins of a heat exchanger with the coating composition of the present invention will be explained. - For boat fishing, a method is adopted in which a coating composition is applied to the surface of the fin and cured by heating. As the coating method, common coating methods for paints, such as a roll coating method, a spray method, a dipping method, a spacing method, a spin cord method, etc. are used.

Solvents used in this case include water, methanol, ethanol, n-propanol, isopropanol, n-butanol, diacetone alcohol, J(7) flucolic solvent, methyl cellosolve, ethyl cellosolve, butyl cellosolve, methyl carpitol. , alcohol solvents such as ethyl calpitol and butyl calpitol, ketone solvents such as methyl ethyl ketone and methyl isobutyl ketone, ester solvents such as methyl acetate, ethyl acetate and butyl acetate, aromatic hydrocarbons such as benzene, toluene and xylene. Examples include amide solvents such as formamide and dimethylformamide, and nitrile solvents such as acetonitrile and acetylnitrile.

[Function] By employing the above means, when the coating composition is applied to the fins of a heat exchanger, the A polymer and the B polymer in the coating have appropriate compatibility, and the aluminum base material side It has a phase-separated structure in which the A polymer with good corrosion resistance and adhesion is present in a high concentration on the air side surface, and the polymer with good hydrophilicity is present in a high concentration on the air side surface, and the crosslinking component of the block copolymer is Because self-crosslinking by oxidation and crosslinking mediated by a metal chelate type crosslinking agent proceed, the coating exhibits extremely good hydrophilic sustainability, corrosion resistance, and adhesion in a well-balanced manner.

Furthermore, by blending the C polymer into the coating composition, the C polymer is present at a high concentration on the air-side surface while intertwined with the B polymer, so that the above effects are more effectively exhibited.

[Example] Hereinafter, the present invention will be specifically explained with reference to Reference Examples, Examples, and Comparative Examples. The number of monomers charged in Reference Examples is summarized in Tables 1 and 2. All copies shown are based on weight.

(Reference Examples 1 to 9) (Production of block copolymer) Thermometer,
230 parts of methyl cellosolve was charged into a reactor equipped with a stirrer and a reflux condenser, and 72 parts of methyl cellosolve was charged while blowing nitrogen gas.
Heat to ℃ and add methyl cellosolve to it.
100 parts Hydrophilic monomer S Part Crosslinking monomer T Part -CCO (
CH2)4 Coo (C2H40)3-Co (CH
2) 4 C00OIs.

A mixture consisting of 20 parts was prepared over 2 hours, and then for another 2 hours.
A polymerization reaction was performed. Then, methyl cellosolve 285 parts methyl methacrylate U part acrylic acid
A mixed solution consisting of part V was charged over 30 minutes and a polymerization reaction was carried out at 75°C for 5 hours. In addition, the above S
The number of copies of -V is as shown in Tables 1 and 2. The polymerization results are also shown in Tables 1 and 2.

(Reference Examples 10 to 13) (Production of random copolymer) 230 parts of methyl cellosolve was charged into a reactor equipped with a thermometer, a stirrer, and a reflux condenser, and 7 parts of methyl cellosolve was charged while blowing nitrogen gas.
Heat to 0℃ and add methyl cellosolve to it.
100 parts hydrophilic monomer S part crosslinking monomer T part methyl methacrylate U part acrylic acid
V part CH3C (CH3) 200CO
A mixed solution consisting of 34.3 parts of C(CH3) was charged over a period of 2 hours, and a copolymerization reaction was carried out over a further 5 hours. The number of parts of the SV and the polymerization results are shown in Table 2.

table The abbreviations in Tables 1 and 2 above have the following meanings.

■: 2-Hydroxyethyl methacrylate ■ Niacryloylmorpholine ■: Vinylpyrrolidone ■: Dimethyl acrylamide ■; Polyethylene glycol methacrylate (side chain molecules 9 approximately 3000) ■: Glycidyl methacrylate ■: N-methylol acrylamide ■: Methyl methacrylate ■ Niacryl Acid *: Solid content (wt%) *; Viscosity at 25°C (P) (Examples 1 to 12 and Comparative Examples 1 to 18) Reference Examples 1 to 13
The C polymer and metal chelate type crosslinking agent shown in Tables 3.5 and 6 were blended with the polymer produced in Table 3.5 and 6, and the composition was applied to aluminum to give a dry film thickness of about 1 μm. Baking was performed under the baking conditions shown in 7.

Various tests shown in Tables 8 to 11 were conducted on these coatings. The results are shown in Tables 8 to 11. In addition,
Comparative Example 18 was directed to an aluminum plate to which no coating composition was applied.

Table 3 The abbreviations of C polymer and metal chelate crosslinking agent in Table 3 above have the following meanings.

(a): Polyethylene oxide (weight average molecular weight 33
00) and polypropylene glycol (weight average molecular weight 2
000) block copolymer (b): polyethylene oxide (weight average molecular weight 10
000) and polypropylene glycol (weight average molecular T
i2000) block copolymer (C) Nidipropoxybis(acetylacetonato)titanium, 75% solution, manufactured by Nippon Soda Co., Ltd. Product name (d):
Tetra n-butoxytitanium, 75% solution, manufactured by Nippon Soda Co., Ltd., trade name TBT (e) Nialuminum monoacetylacetonate bis(
ethyl acetoacetate), 76% solution, manufactured by Kawaken Fine Chemical Co., Ltd. Product name Aluminum Chelate D (f) Nialuminum tris (acetylacetonate)
, 76% solution, Kawaken Fine Chemical Co., Ltd., product name Aluminum Chelate A Table 4 The abbreviations in Table 4 above have the following meanings.

■: Baking at 180℃ for 30 seconds ■: Baking at 200℃ for 30 seconds 02230℃, baking for 30 seconds ■: Baking at 250℃ for 30 seconds Table-5 Table-7 The meanings of the abbreviations in Table 7 above are the same as in Table 4 above.

Table 6 The abbreviations for C polymer and metal chelate crosslinking agent in Tables 5 and 6 above have the same meanings as in Table 3 above Table 8 Table 9 Table 11 Table 1 Tables 8, 9, 10, and 11 above The meanings of the abbreviations are as follows.

(1): Contact angle (degrees) when the coating composition is applied to an aluminum plate and baked (2): Wet state when the coated plate is immersed in water ◎: Full surface repellency, ○: Repellency of about 10% , △: repellency of about 50%, ×: repulsion of about 90% (3): The coated plate was immersed in punch oil, degreased with trichlorethylene at 50°C for 5 minutes, trichlorethylene at room temperature for 3 minutes, and dried. Contact angle (degrees) when applied (4): Similar to (3) above, wet state when coated plate is immersed in water after treatment with trichlorethylene (5) A cycle test was conducted with 7 hours of immersion in running water and 17 hours of drying at 50°C as one cycle. Contact angle (degrees) showing hydrophilicity after the cycle test (6): Water wettability after the cycle test (7); Salt water spray The test was conducted according to JTSZ-2371.

O: No change △: Slight rust ×: Peeling or rust on the entire surface (8): Adhesion test, conducted according to JISD-0202 (base grain peeling test).

(al; 100/100 (bl; 90/1
00 (C1; 70/100 (dl; 60/1
00 (9) The state of wear of the die was observed when pressing the aluminum plate with the die.

○; Mold wear during depression is equivalent to that of untreated aluminum plate.

As shown in the Examples in Tables 8 to 11 above, the coating composition of the present invention exhibits good hydrophilic sustainability, corrosion resistance, and adhesion of the coating formed on the aluminum surface in a well-balanced manner. I understand. This is because polymer A with good corrosion resistance and adhesion exists in a high concentration in the coating on the aluminum plate side, and polymer with good hydrophilicity exists in a high concentration on the air surface side, and the block copolymer This is thought to be due to self-crosslinking by the crosslinking component and a crosslinked structure with a metal chelate type crosslinking agent.

Furthermore, it was found that by blending C polymer, the hydrophilicity was further improved. This is thought to be because the C polymer is present at a high concentration on the air surface side and is present intertwined with the B polymer, so that the hydrophilicity is more effectively exhibited.

On the other hand, as shown in each comparative example, when a random copolymer is used, when a metal chelate type crosslinking agent, etc. is not blended, and when the blending ratio of each component is outside the scope of the present invention, has a drawback in any of these three characteristics,
It was found that the performance was insufficient as a coating composition for heat exchanger fins.

[Effects of the Invention] The coating composition for heat exchanger fins of the present invention has excellent hydrophilicity on the surface of the coating formed on the entire bottom surface of aluminum, etc., and can permanently maintain this effect. It has excellent adhesion to materials, and the film has very good water resistance and mechanical properties. Further, when a block copolymer of polyethylene oxide and polypropylene glycol is blended, the above effects are more effectively exhibited. Therefore, the coating composition for heat exchanger fins of the present invention is very useful as a hydrophilic agent for heat exchanger fins of air conditioners, etc., and moreover, it is a pre-coat applied to aluminum plates before forming the fin material. It can also be used as a type.

Claims (1)

[Claims] 1. Consisting of the following components (a), (b) and (c), with a solid content weight ratio of (a):(b):(c)=5 to 40:60 to
A coating composition for heat exchanger fins having a ratio of 95:1 to 30. (a) Hydrophilic polymer portion consisting of 5 to 35% by weight of structural units based on glycidyl (meth)acrylate or N-methylol (meth)acrylamide, and 65 to 95% by weight of structural units based on hydroxyalkyl (meth)acrylate. and structural unit 7 based on lower alkyl (meth)acrylate
A block copolymer consisting of a hydrophobic polymer portion consisting of 0 to 95% by weight and 5 to 30% by weight of structural units based on (meth)acrylic acid. (b) 1 to 35% by weight of structural units based on glycidyl (meth)acrylate or N-methylol (meth)acrylamide, selected from acryloylmorpholine, N-vinylpyrrolidone, N,N-dimethylacrylamide, polyethylene glycol monomethacrylate A hydrophilic polymer portion consisting of 65 to 99% by weight of structural units based on one or more monomers, 70 to 95% by weight of structural units based on methyl methacrylate, and 5 to 30 structural units based on acrylic acid. A block copolymer consisting of a hydrophobic polymer portion consisting of % by weight. (c) General formula AlX_nY_3_-_n [wherein X is an alkoxy group having 1 to 5 carbon atoms, Y is R^1COCH_2
COR^2 or R^3COCH_2COOR^4, where R^1, R^2, R^3, and R^4 have 1 to 1 carbon atoms.
0 alkyl group, n is 0, 1 or 2] and general formula TiX_nY_4_-_n [wherein X is an alkoxy group or hydroxyl group having 1 to 5 carbon atoms, Y is OC(CH_3
) CHCOCH_3, OC_2H_4N(C_2H_4
OH), OCH(CH_3)COOH, and n is 0 or an integer from 1 to 4]. 2. Consisting of the coating composition for heat exchanger fins according to claim 1 and the following component (d), the solid content weight ratio is (a):(b)
:(c):(d)=5~40:60~95:1~30:
A coating composition for heat exchanger fins having a number of 1 to 40. (d) A block copolymer consisting of polyethylene oxide and polypropylene glycol.