JPS61238864A - Coating composition for heat exchanger - Google Patents

Abstract

PURPOSE:To provide the titled compsn. having excellent water-wettability, persistence and frosting-inhibiting properties, consisting of an aq. thermosetting acrylic/aminoplast resin, etc., the particle of a resin contg. ampholytic ion groups and an alkali metal salt. CONSTITUTION:60-95pts. (by weight; the same applies hereinbelow) aq. resin (A) such as aq. thermosetting acrylic/aminoplast resin composed of 9-5pts. acrylic resin such as methyl (meth)acrylate resin and 1-5pts. aminoplast resin and/or aq. emulsion silicone resin, 3-40pts. OH group-contg. aminosulfonic acid type ampholytic ion compd. (B) contg. aminosulfonic acid type ampholytic ion group of formula I (wherein A is a 1-6C alkylene, phenylene) as an ampholytic group, represented by formula II (wherein R1 is a 1-20C alkyl group which contains at least one OH group and, optionally, O and COO; R2, R3 are each H, a 1-20C alkyl, etc.) and 1-20pts. alkali metal salt (C) (e.g. Li2CO3) are mixed together.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a coating composition applied to a heat transfer surface of a heat exchanger for an air conditioner. This is a coating composition for forming a film that improves the heat exchange characteristics of the resulting heat exchanger, and the heat transfer surface has good water wettability under conditions where moisture condenses on the heat transfer surface.

and its persistence on the heat transfer surface. Characterized by suppressing frost growth.

BACKGROUND ART In recent years, the proportion of air-source heat pump type air conditioners (hereinafter simply referred to as heat pumps) in air conditioners has been rapidly increasing, and they account for more than half of household room air conditioners, commercial air conditioners, and the like. Furthermore, most of the heat exchangers used in these heat pumps are composed of aluminum fins and refrigerant pipes orthogonal to these. It is a fin tube type heat exchanger.

On the other hand, during cooling, moisture condenses on the fin surfaces of the indoor heat exchanger, but if the fin surfaces are in contact with water, water droplets may adhere between adjacent fin surfaces or cause bridges between the fin surfaces. . This increases the ventilation resistance of the heat exchanger, leading to a decrease in the heat exchanger ventilation volume.
This in turn causes a decrease in cooling capacity.

On the other hand, during heating, a similar phenomenon occurs in the outdoor heat exchanger as in the indoor heat exchanger during cooling. Furthermore, during heating, depending on the outside air temperature, frost may form on the outdoor heat exchanger. If frost forms on the heat exchanger, ventilation resistance will increase, leading to a decrease in the amount of air passing through the heat exchanger, which will cause a decrease in heating capacity.

Same as when moisture condensation occurs, but in case of frost formation,
As the heat exchanger becomes more and more clogged, the reduction in passing air volume does not stay at a certain level, but gradually decreases over time.For this reason, it is generally recommended that the outdoor heat exchanger Defrosting the container. Hot gas defrost is a common defrosting method, but during this time heating operation is temporarily stopped. As a result, the indoor temperature decreases, resulting in discomfort.

In addition, when defrosting, if the fin surface is in contact with water, the water from the melted frost becomes water droplets between adjacent fins, or remains in the heat exchanger in a bridged state, which makes it difficult to restart heating operation. In addition, residual moisture freezes between the fins, which promotes frost formation and accelerates clogging of the heat exchanger, resulting in an even more severe reduction in heating capacity. This increases the frequency of defrosting, which increases discomfort and significantly reduces operating efficiency.

In conventional heat pumps, various problems arise if the aluminum fin surface is not made hydrophilic, so several treatment methods have been proposed to make the fin surface hydrophilic. No. 50-38645 discloses a method of forming a porous inorganic film on the fin surface, and JP-A-54-148034 discloses a method of attaching an organic film to the fin surface.
A method to obtain water wettability by hydrolyzing only the surface.

A method has been proposed to improve water drainage and water wettability by specializing the shape of the fins. however.

All of these methods are aimed primarily at maintaining heat exchange characteristics by improving water wettability, eliminating bridges between fins, and suppressing increases in ventilation resistance.1 They are completely powerless to prevent frost formation. be.

In addition, in the technology of improving water wettability using surfactants, in order to reduce durability due to dissolution of surfactants, JP-A-58 taught the formation of a film made of surfactants and higher fatty acids. -16192, but this technique also does not take into account frost formation prevention at all.

On the other hand, as a means to prevent frost formation,
No. 138 proposes periodically spouting a melting point depressing substance into a press-fit container, but this is mainly used as a means to prevent frost formation inside a refrigerator.

In the outdoor heat exchanger of a heat pump with a large number of fins, uniform jetting is difficult, and providing a pressure vessel increases the size of the device, which is undesirable.Another method is to form a hydrophobic film on the surface of the fins. This is disclosed in Japanese Patent Publication No. 139159/1982, but although it has the possibility of suppressing frost formation, it is undesirable because it has the problem of water droplet bridges occurring during defrosting.

As described above, no technology has been found that simultaneously solves the problems of water wettability and sustainability and the suppression of frost formation.

There was a strong need for the development of an effective means for this purpose in the market.

On the other hand, fire prevention and worker health in painting lines,
Also, from the point of view of saving resources, it is clear that such a coating composition that is an aqueous treatment agent meets market needs.

In view of the problems to be solved by the invention, it is an object of the present invention to provide an aqueous coating composition that has excellent water wettability and durability when applied to heat exchanger aluminum fins, and is effective in suppressing frost formation. This is the object of the present invention.

Means for Solving the Problems The inventors of the present invention have conducted a series of researches in which a hydrophilic group such as a hydroxyl group, a carboxyl group, an amino group, a sulfone group, a phosphoric acid group, etc. It is said that the scales impart water wettability to a considerable extent by making the fin surface layer have a zwitterionic group, and due to the polarity of the fin surface layer, a much greater improvement in water wettability can be seen than with normal parent wood groups. discovered. However, when the zwitterionic group is a molecule, its water solubility is high;
Elutes from the membrane surface over time.

On the other hand, when a polymer having an amphoteric ionic group is made into a polymer or hydrophobic, its water solubility and water dispersibility become too poor, resulting in aggregation and precipitation in water. Therefore, the present inventors introduced amphoteric ionic groups in the form of resin particles having such groups to maintain stability in water.

Furthermore, we succeeded in preventing dissolution and outflow due to water and greatly improving water wettability and durability.

Furthermore, we are conducting research on the formation and growth mechanism of frost formation. First, water droplets condense when the fin surface is below the dew point, and then the water droplets or water film (when water wettability is good) freezes, resulting in so-called crystallization. Then, frost kernels form on top of the frost, and in the first stage, moisture in the air adheres to the frost kernels due to the sublimation phenomenon, forming frost.

It was confirmed that they were forming and growing. It is clear that it would be desirable if the height of frost on the aluminum fins of the heat exchanger on the outdoor side could be lowered, allowing heating operation to continue for a longer period of time. The present inventors include an alkali metal salt in the coating composition.

We discovered the surprising fact that this frost growth can be suppressed and the height of frost can be kept low.

Based on this knowledge, the present invention provides a coating composition having the following composition that can provide a coating that is water-wettable, durable, and effective in suppressing frost formation when applied to heat exchanger aluminum fins. be given

That is, the coating composition of the present invention comprises (a) an aqueous thermosetting acrylic/aminoplast modified resin and/or an aqueous emulsion silicone resin, (b) resin particles having zwitterionic groups, and (c) an alkali metal salt. .

Solid content weight ratio (a): (b): (c) = (
60-95): (3-40): (1-20).

The aqueous resin used as the first component of the composition of the invention is a thermoset acrylic/aminoplast modified resin and/or an aqueous emulsion silicone resin. The term "aqueous resin" used in the present invention broadly includes water-soluble, water-dispersible, and emulsion-type resins. These resins have excellent weather resistance, water resistance, corrosion resistance, and stain resistance, making them ideal for use in heat exchangers for both indoor and outdoor surfaces. By the way, it's alkyd resin.

Epoxy resins have insufficient weather resistance and cannot be used outdoors.Acrylic resins can be used with alkyl esters of acrylic acid or methacrylic acid, and in some cases with other ethylenically unsaturated monomers that can be copolymerized with this. The most desirable resin is a resin obtained by copolymerizing a monomer having a crosslinkable functional group by a conventional method. A suitable alkyl (meth)acrylate ester is, for example, methyl (meth)acrylate.

Ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, (meth)acrylic acid 2
-Ethylhexyl etc.

Examples of other ethylenically unsaturated monomers include vinyl acetate, acrylonitrile, styrene, vinyltoluene, etc. The monomers used in the present invention are of course not limited to these, but are usually acrylic resins. Conveniently, what is known as a snail is used. Examples of monomers having a crosslinkable functional group include acrylic acid, methacrylic acid, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, and N-(butoxymethyl)-(meth)acrylamide.

Examples include glycidyl (meth)acrylate.

In addition, monomers that act as catalysts in the crosslinking reaction between the copolymer and the crosslinking agent can be incorporated into the Acrif polymer. For example, acrylic acid and methacrylic acid are commonly used.
Acid groups can also be introduced using sulfonic group-containing monomers such as 2-sulfoethyl methacrylate and acidic butyl maleate. As a method for producing the acrylic resin, known methods such as solution polymerization, water solubilization from bulk polymerization, or water dispersion can be used, and emulsion polymerization methods can also be used.

In the present invention, examples of aqueous aminoplast resins that can be crosslinked with acrylic resins include urea, thiourea, melamine, benzoguanamine, and lower alkyl ethers of the condensates. The blending amount of the crosslinking agent is acrylic resin/aminoplast resin in a solid weight ratio of 9/1 to 515. It is preferable to use a ratio of 872 to 6/4.

The aqueous emulsion silicone resin used in the present invention can be appropriately selected from various commercially available products.

Next, in the coating composition of the present invention, the resin particles having amphoteric ionic groups used as the second component have amphoteric ionic groups, and any resin can be used as long as it can exist as particles in the system. In particular, those having an aminosulfonic acid type zwitterionic group represented by the following formula % as the zwitterionic group are desirable. Such resin particles have the formula % formula % (wherein R1 has at least one hydroxyl group,
May contain 10- or -Co〇- in the molecule0
1-C2° alkyl group, R2 and R1 are the same or different from each other and have a hydrogen atom, 01-C2° alkyl group, an alkyl group or cyclic group having at least one hydroxyl group and/or sulfonic acid group, A is 01- C,
Acrylic polymer particles obtained by emulsion polymerization using a polyester containing a hydroxyl group-containing aminosulfonic acid zwitterionic compound (hereinafter simply referred to as a zwitterionic compound) represented by (an alkylene or phenylene group) as an emulsifier have advantages in production and effectiveness. The above is particularly suitable.

The above emulsifier is produced using the amphoteric ionic compound represented by the above formula 2 and from common polyester resin constituents in accordance with a conventional method. The constituent components of the polyester resin and their usage amounts are as follows.

Oil-free system: Zwitterionic compound 0.05-50% by weight, preferably 0
．． 5-30% by weight, polybasic acid compound 2-90% by weight, optionally polyhydric alcohol 0-90% by weight, and/or oxirane compound O-90% by weight, alkyd system: zwitterionic compound 0.05-90% by weight 30% by weight, preferably 0
．． 1 to 20% by weight, polybasic acid compound 2 to 90% by weight, polyhydric alcohol 2 to 90% by weight, fatty acid and/or oil 1 to 80% by weight. Examples of the above zwitterionic compounds include N-(2-hydroxyethyl ) Aminomethanesulfonic acid, N-(2-hydroxy-1-methylethyl)aminomethanesulfonic acid, N-(2-hydroxypropyl)aminomethanesulfonic acid, N-(3-hydroxypropyl)aminomethanesulfonic acid, N -(2-propyl 2-hydroxyethyl)
Aminomethanesulfonic acid, N-(2-methyl-2-ethyl-2-hydroxyethyl)aminomethanesulfonic acid,
N-(1,2-dimethyl-2-hydroxyethyl)aminomethanesulfonic acid, N-(1-methyl-5,5-dimethyl-5-hydroxypentyl)aminomethanesulfonic acid, N-(1,-2- diisopropyl-2-hydroxyethyl)aminomethanesulfonic acid, N-(2,3-dihydroxypropyl)aminomethanesulfonic acid, N-(1
-Hydroxymethyl-2-hydroxyethyl)aminomethanesulfonic acid, N-(1-hydroxymethyl-2-methyl-2-hydroxyethyl)aminomethanesulfonic acid, N-(1-hydroxymethyl-3-hydroxypropyl)amino Methanesulfonic acid, N-(1-(γ-hydroxypropyl)-2-hydroxyethyl)aminomethanesulfonic acid, N-(1,,1-bis(hydroxymethyl)-2-hydroxyethyl)aminomethanesulfonic acid.

N-(2,2-bis(hydroxymethyl)-3-hydroxypropyl)aminomethanesulfonic acid and N-alkyl and N,N-dialkyl substituted products thereof; N,N-bis(2-hydroxyethyl)amino Methanesulfonic acid, N-(2-hydroxyethyl)-N-(2-
hydroxypropyl)aminomethanesulfonic acid, N,N
-bis(2-hydroxypropyl)aminomethanesulfonic acid, N,N-bis(4-hydroxybutyl)aminomethanesulfonic acid, N-(2-hydroxyethyl)-N-
(1,1-bis(hydroxymethyl)-2-hydroxyethyl)aminomethanesulfonic acid, N-(3-hydroxypropyl)-N-(1,1-bis(hydroxymethyl)-2-hydroxyethyl)aminomethane Sulfonic acid,
N,N-bis(2,3-dihydroxypropyl)aminomethanesulfonic acid, N,N-bis(1-hydroxymethyl)-2-hydroxyethyl)aminomethanesulfonic acid, N,N-bis(1゜1 -(bishydroxymethyl)
-2-hydroxyethyl)aminomethanesulfonic acid and N-alkyl substituted products thereof; N-(2-hydroxyethyl)aminoethanesulfonic acid, N-(2,2-bis(hydroxymethyl)-3-hydroxypropyl) aminoethanesulfonic acids and N-alkyl or N,N-dialkyl substituted products thereof;
N,N-bis(2-hydroxyethyl)aminoethanesulfonic acid, N-(2-hydroxyethyl)-N-(2-
hydroxypropyl)aminoethanesulfonic acid, N,N
-bis(2-hydroxypropyl)aminoethanesulfonic acid, N,N-bis(4-hydroxybutyl)aminoethanesulfonic acid, N-(2-hydroxyethyl)-N-
(1,1-bis(hydroxymethyl)-2-hydroxyethyl)aminoethanesulfonic acid, N-(3-hydroxypropyl)-N-(1,1-bis(hydroxymethyl)-2-hydroxyethyl)aminoethane Sulfonic acid,
N,N-bis(2,3-dihydroxypropyl)aminoethanesulfonic acid, N,N-bis-(1-(hydroxymethyl)-2-hydroxyethyl)aminoethanesulfonic acid.

N,N-bis-(1,1-(bishydroxymethyl)-
2-hydroxyethyl)aminoethanesulfonic acid and their N-alkyl substituted products; 3-(N-(2-hydroxyethyl))aminopropanesulfonic acid, 3-(N-(2-hydroxy-1-methylethyl) ) Aminopropanesulfonic acid (1), 3-(N
-(2-hydroxypropyl))aminopropanesulfonic acid (1), 3-(N-(3-hydroxypropyl)
) Aminopropanesulfonic acid (1), 3-(N-(2
-propyl-2-hydroxyethyl))aminopropanesulfonic acid-(1),3-(N-(2-methyl-2-ethyl-2-hydroxyethyl))aminopropanesulfonic acid-(1),3-( N-(1,2-dimethyl-2-
hydroxyethyl))aminopropanesulfonic acid-(1
), 3-(N-(1,1,2,2-tetramethyl-2-
hydroxyethyl))aminopropanesulfonic acid-(1
), 3-(N-(1-methyl-5,5-dimethyl-5-
hydroxypentyl)) aminopropanesulfonic acid-(
1), 3-(N-(1,2-diisopropyl-2-hydroxyethyl))aminopropanesulfonic acid-(1),
3-(N-(2,3-dihydroxypropyl))aminopropanesulfonic acid-(1), 3-(N-(1-hydroxymethyl-2-hydroxyethyl))aminopropanesulfonic acid-(1), 3 -(N-(1-hydroxymethyl-2-methyl-2-methyl-2-hydroxyethyl))aminopropanesulfonic acid = (1), 3-(N-(
1-hydroxymetal-3-hydroxypropyl)) aminopropanesulfonic acid-(1), 3-(N-(1-
(γ-hydroxypropyl)-2-hydroxyethyl)
) Aminopropanesulfonic acid, 3-(N-(1,1-bis(hydroxymethyl)-2-hydroxyethyl))aminopropanesulfonic acid-(1), 3-(N-(2,2
-bis(hydroxymethyl)-3-hydroxypropyl))aminopropanesulfonic acid-(1) and N-alkyl or N,N-dialkyl substituted products thereof; 3
-(N,N-bis(2-hydroxyethyl))aminopropanesulfonic acid-(1),3-(N-(2-hydroxyethyl)-N-(2-hydroxypropyl))aminopropanesulfonic acid-( 1), 3-(N, N-bis(2
-Hydroxypropyl))aminopropanesulfonic acid-
(1), 3-(N, N-bis(4-hydroxybutyl)
) Aminopropanesulfonic acid-(1), 3-(N-(2
-hydroxyethyl)-N-(1,1-bis(hydroxymethyl)-2-hydroxyethyl))aminopropanesulfonic acid-(1),3-(N-(3-hydroxypropyl)-N-1,1 -bis(hydroxymethyl)-2-
hydroxyethyl))aminopropanesulfonic acid-(1
), 3-(N,N-bis(2,3-dihydroxypropyl))aminopropanesulfonic acid-(1), 3-(N,
N-bis(1-(hydroxymethyl)-2-hydroxyethyl))aminopropanesulfonic acid-(1), 3-(
N,N-bis-(1゜1-(bishydroxymethyl)-
2-Hydroxyethyl))aminopropanesulfonic acid-
(1), and their N-alkyl substituents; 5-(
N-(2-hydroxyethyl))aminopentanesulfonic acid-(1) and its N-alkyl and N,N-dialkyl substituted products; 5-(N,N-bis-(2-hydroxyethyl))aminopentanesulfone Acid-(1) and its N-alkyl substituted product (5-(N-methyl-N, N-bis-2-hydroxyethyl))ammoniopentanesulfonic acid-(1) Betaine, 5-(N-ethyl- N,N-bis(2-hydroxyethyl))ammoniopentanesulfonic acid-(1) betaine, 5-(N-butyl-N,N-
Bis(2-hydroxyethyl))ammoniopentanesulfonic acid = (1) Betaine, 5-(N-dodecyl-N.

N-bis(2-hydroxyethyl)ammoniopentanesulfonic acid-(1) Betaine, 5-(N-stearyl-N,N-bis(2-hydroxyethyl))ammoniopentanesulfonic acid-(1) 5-(N
, N,N-tris-(2-hydroxyethyl))ammoniopentanesulfonic acid-(1) betaine.

N-(2-hydroxyethyl)iminodiethanesulfonic acid, N-(2-hydroxypropyl)iminodiethanesulfonic acid, N-(2,3-dihydroxypropyl)iminodiethanesulfonic acid, N-(1,1 -bis(hydroxymethyl)-2-hydroxyethyl)iminodiethanesulfonic acid, N-(2-hydroxyethyl)iminoethanesulfonic acid propanesulfonic acid.

N-(2-hydroxypropyl)iminoethanesulfonic acid propanesulfonic acid, N-(2,3-dihydroxypropyl)iminoethanesulfonic acid propanesulfonic acid,
N-(1,1-bis(hydroxymethyl)-2-hydroxyethyl)iminoethanesulfonic acid, propanesulfonic acid, N-(2-hydroxyethyl)orthanylic acid, N-
(2-hydroxyethyl)methanilic acid, N-(2-hydroxyethyl)sulfanilic acid.

N,N-bis-(2-hydroxyethyl)orthanilic acid, N,N-bis-(2-hydroxyethyl)methanilic acid, N,N-bis-(2-hydroxyethyl)sulfanilic acid, etc. One or more of these are used. These may be present in their original form or as basic substances (
For example, it is used as a salt with ammonia, amine, alkali metal).

Examples of polybasic acid compounds include adipic acid, azelaic acid, sebacic acid, decanedicarboxylic acid, dodecyldicarboxylic acid, phthalic anhydride, isophthalic acid, terephthalic acid,
Phosuccinic anhydride, tetrahydrophthalic anhydride, himic anhydride, trimellitic anhydride, pyromellitic anhydride, tetrabromo phthalic anhydride, tetrachlorophthalic anhydride,
Het's acid anhydride, etc., and polyhydric alcohols such as ethylene glycol and propylene glycol.

1.3-butylene gellicol, 1,6-hexanediol, diethylene glycol, dipropylene glycol,
Examples include neopentyl glycol, triethylene glycol, hydrogenated bisphenol, glycerin, trimethylolethane, trimethylolpropane, and pentaerythritol, each of which may be used singly or in combination of two or more.

Examples of oxirane compounds include phenyl glycidyl ether, methyl glycidyl ether, n-butyl glycidyl ether, persatic acid glycidyl ester, and examples of fatty acids include soybean oil fatty acid,
Linseed oil fatty acids, safflower oil fatty acids, tall oil fatty acids, coconut oil fatty acids, anhydrous castor oil fatty acids, tung oil fatty acids,
Synthetic fatty acids, etc. are used as oils such as castor water,
coconut oil.

Linseed oil, palm oil, safflower oil, soybean oil, tung oil,
Examples include anhydrous castor oil, and one or more types of each can be used.

The emulsifier used in the present invention is composed of the polyester resin obtained as described above, and particularly has an acid value of 30 to 1.
50. Preferably it is 40 to 150, and the number average molecular weight (
(hereinafter referred to as M5) is 500 to 5000. Preferably 70
It only needs to be set within the range of 0 to 3000. By adjusting the balance between the molecular weight and the hydrophilic functional group in this way, various properties such as reliability as an emulsifier, emulsification, and dispersibility are improved. . Further, the polyester resin may be used in a state in which at least 20 or more of its acid groups in terms of acid value are neutralized with ammonia, amine or alkali metal. Such a neutralized state improves solubility in water.

The acrylic resin emulsion polymer particles according to the present invention can be easily emulsion polymerized by using the above polyester resin as an emulsifier when carrying out emulsion polymerization of α,β-unsaturated monomers in an aqueous medium in the presence of a polymerization initiator. Manufactured.

As the above α,β-unsaturated monomer, any one mentioned in the section of the acrylic/aminoplast resin can be used. Furthermore, the polymer particles may optionally be crosslinked, in which case as crosslinkable comonomers.

A monomer having two or more radically polymerizable ethylenically unsaturated bonds in the molecule, or a monomer having two types of ethylenically unsaturated groups each carrying a group that can react with each other. Can be used in combination.

Examples of the former include ethylene glycol diacrylate, ethylene glycol dimethacrylate, triethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, 1,3-butylene gelicold dimethacrylate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, 1,
4-butanediol diacrylate, neopentyl glycol diacrylate, 1,6-hexanediol diacrylate, pentaerythritol diacrylate, pentaerythritol triacrylate.

Pentaerythritol tetraacrylate, pentaerythritol dimethacrylate, pentaerythritol trimethacrylate, pentaerythritol tetramethacrylate, glycerol dimethacrylate, glycerol diacrylate, glycerol allyloxy dimethacrylate, 1,1゜1-trishydroxymethylethane diacrylate, 1,1 .1-trishydroxymethylethane triacrylate, 1.1.1-trishydroxymethylethane dimethacrylate, 1,1.1-trishydroxymethylethane triacrylate.

1.1.1-trishydroxymethylpropane diacrylate, 1,1.1-trishydroxymethylpropane triacrylate, 1,1.1-trishydroxymethylpropane dimethacrylate, 1.1.1-trishydroxymethylpropane triacrylate Examples include methacrylate, triallyl cyanurate, triallyl isocyanurate, triallyl trimellitate, diallyl cyanurate, diallyl phthalate and divinylbenzene; examples of the latter include glycidyl group-containing ethylenic monomers such as glycidyl methacrylate and glycidyl acrylate. Saturated monomers, acrylic acid, methacrylic acid.

Carboxyl group-containing ethylenically unsaturated monomers such as crotonic acid; 2-hydroxyethyl acrylate, hydroxypropyl acrylate, 2-hydroxyethyl methacrylate, hydroxypropyl methacrylate, hydroxybutyl acrylate, hydroxybutyl methacrylate, furyl alcohol, methalyl alcohol, etc. Ethylenically unsaturated monomers having an isocyanate group such as vinyl isocyanate, isopropenyl isocyanate, and the like can be mentioned.

During polymerization, 1. A common emulsion polymerization initiator, such as potassium persulfate, hydrogen peroxide, etc., a redox initiator, and an azo initiator such as azobiscyanovaleric acid, is used to give a .05-5%, preferably 0.1-5%
About 4% is used, and if desired, organic peroxides such as benzoyl peroxide and t-butyl peroxide, azo compounds, and other conventional chain transfer agents can be used.

The emulsion polymerization method may be carried out under normal conditions and methods, except for using the above-mentioned polyester resin as an emulsifier. For example, the emulsion polymerization may be carried out under conditions of 0 to 100°C for 5 minutes to 72 hours, batchwise or wholly or partially dropwise. The amount of the polyester resin emulsifier to be used is usually selected in the range of 0.5 to 200 parts, preferably 1.0 to 100 parts, based on 100 parts of the α,β-unsaturated monomer. If it is less than 5 parts, a large amount of lumps tends to be produced during synthesis, and if it exceeds 200 parts, there is no particular problem.

If the amount is too large, the meaning of the acrylic resin emulsion polymer particles will be lost.The polymer particles of the present invention can be prepared by solution polymerization or bulk polymerization of α,β-unsaturated monomers by a conventional method, without using such emulsion polymerization method. It can also be made by polymerization and then emulsified and dispersed in an aqueous medium in the presence of the polyester resin.

Such polymer particles can be used in isolation or in the form of an emulsion. However, in the present invention, it is necessary that the composition contains 3 to 40% by weight of the zwitterion-containing polymer particles in terms of solid content. This is because if it is less than 3%, water wettability will be poor, and if it exceeds 40%, water resistance will be poor, both of which are unfavorable for the purpose of the present invention.

In the composition of the present invention, an alkali metal salt is used as the third component. Various alkali metal salts can be used as the component, but those with a high water solubility are not preferred for long-lasting frost formation prevention, and those with a water solubility of 5% by weight or less at 20°C are particularly preferred. In this sense, acetates and carbonates of alkali metals, especially lithium, are preferably used as they give good results.

The amount of alkali metal salt blended is selected within the range of 1 to 20% by weight based on the total composition; if it is less than 1% by weight, the frost formation inhibiting effect will not be exhibited, while if it exceeds 20%, the coating film will become brittle. It has been found to be impractical.

The composition of the present invention may also include pigments, extender pigments,
Dyes, surfactants and other paint additives can be added. In addition, steel ball mills are a common dispersion method for producing paints.

Techniques such as a sand grind mill and disperser stirring can be used.

The composition of the present invention is applied to heat exchanger aluminum fins in a conventional manner.
For example, when applied by conventional coating means and treated with dry baking, it provides a coating that not only has good water wettability and durability, but also has excellent anti-frost effect, and is suitable for heat exchanger aluminum fins. This invention effectively suppresses the formation of water droplet bridges, freezing, and frost formation, and is extremely useful in maintaining good thermal efficiency in ordinary indoor and outdoor heat exchangers.

The present invention will be explained below with reference to Examples. Unless otherwise specified, all parts and percentages are by weight.

Production Example 1 (Aqueous acrylic resin) 50 parts of butyl cellosolve and 10 parts of butyl calpitol were charged into a reaction vessel equipped with a stirrer, a temperature controller, and a reflux condenser. Next, a solution of methacrylic acid with the following composition
10 parts Methyl methacrylate 31 Ethyl acrylate 442-Hydroxyethyl acrylate 153-Azobisisobutyronitrile 20 parts of 1.5 were added, heated with stirring, and the temperature was gradually raised to 130°C over 1 hour. .

Next, the remaining 81.5 parts of the above mixture was added dropwise at 130°C over 3 hours, and further 0.3 parts of azobisisobutyronitrile,
A solution consisting of 3 parts of quijirole and 2 parts of butyl cellosolve was added dropwise over 30 minutes. The reaction solution was further stirred at 130° C. for 2 hours to increase the conversion rate to resin, and then the reaction was terminated.

Cool to 80°C, add 10 parts of dimethylethanolamine dropwise over 1 hour while stirring, and add 75 parts of deionized water.
1 hour to make it aqueous, completing the synthesis of the resin liquid. The aqueous resin solids content was 40%.

Production Example 2 (Production of emulsifier) 191 parts of hydroxyethyl taurine, 140 parts of ethylene glycol, and 170 parts of triethylene glycol were placed in a 2Q Kolbene equipped with a stirrer, a nitrogen inlet tube, a temperature controller, a condenser, and a decanter.

331 parts of adipic acid, 168 parts of phthalic anhydride and 40 parts of xylene were charged and the temperature was raised. Water produced by the reaction is removed by azeotropic reflux with xylene.

The temperature was raised to 190° C. over about 2 hours from the start of reflux, and stirring and dehydration were continued until the acid value equivalent to carboxylic acid became 10 or less to complete the reaction. The obtained polyester resin had a monovalent value of 79, a hydroxyl value of 79, and an M5 of 708.

Production Example 3 (Production of emulsifier) 85 parts of dehydrated coconut oil, 63 parts of coconut oil, and 53 parts of trimethylolpropane were charged into a 2Q Kolben equipped with a stirrer, a nitrogen inlet pipe, a temperature control device, a condenser, and a decanter, and the mixture was heated under a nitrogen atmosphere. When the temperature was raised to 240° C. and stirred for 30 minutes, the methanol tolerance became infinite. The temperature of the contents was lowered to 150°C, stirring was stopped, and 725 parts of phthalic anhydride, 343 parts of ethylene glycol, 43 parts of trimethylolpropane, and 375 parts of N,N-bis-(2-hydroxyethyl)aminoethanesulfonic acid were added. and 45 parts of xylene were charged, stirring was started again, and the water produced was removed by azeotropic reflux with the xylene while gradually increasing the temperature. The temperature was raised to 240° C. over about 2 hours, and stirring and dehydration were continued at the same temperature until the acid value equivalent to carboxylic acid reached 8 to complete the reaction. The obtained polyester resin has an oil length of 10, an acid value of 66, and a hydroxyl value of 100. It was M5800.

Production Example 4 (Particles I) 306 parts of deionized water, 30 parts of the polyester resin obtained in Production Example 2, and 3 parts of dimethylethanolamine were placed in a reaction vessel equipped with a stirrer, a cooler, and a temperature control device. Mixed solution) is dissolved while stirring while maintaining the temperature at 80°C, and to this is added a solution of 4.5 parts of azobiscyanovaleric acid dissolved in 45 parts of deionized water and 4.3 parts of jetanolamine. Next, a second mixed solution consisting of 72 parts of methyl methacrylate, 96 parts of n-butyl acrylate, 72 parts of styrene and 30 parts of 2-hydroxyethyl acrylate is added dropwise over 60 minutes.

After the dropwise addition, 1.5 parts of azobiscyanovaleric acid dissolved in 15 parts of deionized water and 1.4 parts of jetanolamine was added, and stirring was continued for 60 minutes at 80°C, resulting in a zwitterion with a non-volatile content of 45%. Acrylic resin emulsion particles with groups were obtained.

Production Example 5 (Particles ■) The resin obtained in Production Example 3 was used instead of the resin obtained in Production Example 2 as an emulsifier, and methyl methacrylate 7
Crosslinked zwitterionic group-containing acrylic emulsion particles were obtained in the same manner as in Production Example 4 except that 62 parts of methyl methacrylate and 10 parts of ethylene glycol dimethacrylate were used instead of 2 parts. The nonvolatile content was 43%.

Example 1 100 parts of the aqueous acrylic resin obtained in Production Example 1 and 5 parts of lithium carbonate were placed in a 500 taQ stainless steel airtight container together with alumina beads having a diameter of 5 nn, and dispersed for 30 minutes using a Red Devil type disperser. Next, 15 parts of Sumimaru M-40w (manufactured by Sumimaru Kagaku Co., Ltd., melamine resin non-volatile content = 80%) was added as a curing agent, and then 22.2 parts of the emulsion obtained in Production Example 4 was added to prepare the coating material.

Apply this paint to an aluminum plate (10 cx x 20 parts w x lam
) with a percoater and baked at 140℃ for 20 minutes to prepare test pieces (coating thickness 10μ), water wettability,
Sustainability and frost formation tests were conducted. As shown in Table 1 below, extremely satisfactory results were obtained in all tests.

Comparative Examples 1-2 Comparative Example 1 Comparative Example 2 Acrylic resin of Production Example 1 100 parts 100 parts Sumimaru M-40w 15 15 Emulsion of Production Example 4 0 0 Lithium carbonate
05 With the above composition, paints were prepared by disper stirring in Comparative Example 1 and by the same means as in Example 1 in Comparative Example 2, and test pieces were prepared in the same manner as in Example 1 and subjected to testing. As shown in Table 1, the test results showed poor water wettability and durability.
The height of frost formation was also large.

Example 2 100 parts of Toray Silicone (manufactured by Toray Silicone Co., Ltd., organopolysiloxane emulsion resin non-volatile content 40%) Lithium fluoride
2 parts Emulsion of Production Example 5 1.2 parts The composition was prepared according to the preparation method of Example 1, applied to an aluminum plate in the same manner as in Example 1, and baked at 140°C for 30 minutes to form a test piece (film thickness 5 μm). ) was created and tested. As shown in Table 1, the water wettability, durability, and frost suppression were all extremely good.

Comparative Examples 3 to 4 Comparative Example 3 Comparative Example 4 Toray Silicone 100 parts Lithium fluoride OO 0 A composition consisting of 12 parts of the emulsion of Production Example 5 was prepared by disper stirring, and test pieces were prepared in the same manner as in Example 2. Tested.

As is clear from Table 1, silicone alone is unsatisfactory in terms of water wettability, sustainability, and frost formation control, and even if resin particle emulsion is added to this, although water wettability and sustainability are improved, frost formation It is recognized that no improvement has been made in terms of suppression.

Test method: Water wettability: Pure water was sprayed once on the test piece using Wider #71 (manufactured by Iwakuni Toki Co., Ltd.), and the spread of water droplets was observed.

0...Good water wettability X...Same defect Sustainability of water wettability: Immerse the test piece in pure water at 20℃ for 8 hours Then, lift it up and leave it in the wind for 16 hours at 20℃. 5 cycles of drying Water wettability after cycle Judgment was made using the sex test method.

For evaluation of frost suppression effect, use the equipment shown in the attached diagram.
Tests were conducted on various test pieces under the following conditions.

Evaluation conditions Air temperature (DB) 20℃ Air temperature (WB) 14.5℃ Average wind speed in duct 0.5■18 Sample surface temperature -10℃ The entire device was installed in a constant temperature room where temperature and humidity could be controlled. ing. The average wind speed in the duct is calculated from the value obtained from the nozzle differential pressure type airflow meter, and is made to reach a predetermined value by controlling the rotation speed of the fan. The surface temperature of the test piece is kept at a predetermined value by controlling the temperature of the brine sent to the cooling plate.

To evaluate the frost height, we devised a device that could move perpendicular to the cooling plate and read the distance, and measured the height of the frost surface at appropriate times. For the frost height, the average value of the measurement results at multiple points was used.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of a testing device for frost formation suppression as an effect of the present invention. patent application agent

Claims (1)

[Scope of Claims] (a) water-based thermosetting acrylic/aminoplast resin and/or water-based emulsion silicone resin, (b) resin particles having zwitterionic groups, and (c) alkali metal salt, solid weight In the ratio, (a):(b):(c)=(60~9
5) A composition for coating a heat exchanger, characterized in that it contains the composition in a ratio of: (3-40): (1-20).