JPS63280776A - Coating composition and heat exchanger coated therewith - Google Patents

Abstract

PURPOSE:To obtain a coating material, having excellent water wettability and persistence, effective in suppressing frosting and suitable for heat exchangers, etc., of air conditioners, by containing an N-alkylene-substituted acrylamide polymer, etc., saccharides and alkali metal salt. CONSTITUTION:The aimed coating composition, obtained by blending (A) an emulsion of at least one or more polymers consisting of the group of N-alkylene- substituted acrylamide homopolymer expressed by the formula [A is -(CH2)n-; n is 4 or 5], two kinds of copolymers and copolymers of the above-mentioned N-alkylene-substituted acrylamide and other monomers with (B) saccharides at 30/70-90/10 (solid weight ratio) or the component (A) in an amount of 30-89wt.% (based on the total weight of the three components), component (B) in an amount of 10-69wt.% with (C) 1-50wt.% alkali metal salt. Heat transfer surfaces of a heat exchangers in air conditioner are coated with the above-mentioned composition.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a coating composition applied to a heat transfer surface in a heat exchanger for an air conditioner. The present invention relates to a coating composition for forming a coating that improves the heat exchange characteristics of a heat exchanger that produces heat exchangers, and a heat exchanger that has a heat transfer surface coated with the composition. Under conditions where condensation occurs, the heat transfer surface has good water wettability and is persistent, and suppresses the growth of frost on the heat transfer surface. .

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 now account for more than half of household room air conditioners and commercial air conditioners. Furthermore, most of the heat exchangers used in these heat pumps are fin-tube heat exchangers that are composed of aluminum fins and refrigerant pipes orthogonal to the aluminum fins.

During cooling, moisture condenses on the fin surfaces of the indoor heat exchanger, but if the fin surfaces are water-repellent, water droplets will adhere to the surfaces of adjacent fins or form bridges between the fin surfaces, thus preventing heat exchange. Increase the ventilation resistance of the vessel and heat exchanger ventilation! i! +, which in turn causes a decrease in cooling capacity.

On the other hand, during heating, the same phenomenon occurs in the outdoor heat exchanger as in the indoor heat exchanger during cooling. Also, during heating, frost may form on the outdoor heat exchanger depending on the outside air temperature. When frost forms on a heat exchanger, ventilation resistance increases, leading to a decrease in the amount of air passing through the heat exchanger, which causes a decrease in heating capacity in the same way as moisture condensation. As the vessel becomes more and more clogged, the decrease in the amount of air passing through it does not stay at a certain level, but gradually decreases over time. For this reason, the outdoor heat exchanger is generally defrosted based on certain criteria. Hot gas defrost is a common defrosting method, but heating operation is temporarily stopped during this time. This causes the indoor temperature to drop, resulting in discomfort. Furthermore, during defrosting, if the fin surface is water-repellent, water from melted frost becomes water droplets between adjacent fins or remains in the heat exchanger in a bridged state. For this reason, when heating operation is restarted, the initial air volume decreases. In addition, residual moisture freezes between the fins, which promotes frost formation, which leads to faster clogging of the heat exchanger and further worsens the reduction in heating capacity. For this reason, the frequency of defrosting increases, which increases discomfort and significantly reduces operating efficiency.

As described above, in conventional heat pumps, various problems arise unless the aluminum fin surfaces are made hydrophilic, so several treatment methods have been proposed to make the fin surfaces hydrophilic. For example, JP-A-50-38645 discloses a method of forming a porous inorganic film on the fin surface, and JP-A-54-148034 discloses a method of forming an organic film on the fin surface.
A method of obtaining water wettability by hydrolyzing only the surface, and a method of improving water drainage and water wettability by specializing the shape of the fins have been proposed. However, all of these methods mainly aim to maintain heat exchange characteristics by improving water wettability, eliminating bridges between fins, and suppressing increases in ventilation resistance, and do not work at all to prevent frost formation. Powerless.

In addition, in the technology of improving water wettability using surfactants, Japanese Patent Application Laid-Open No. 58-16192 taught the formation of a film consisting of a surfactant and a higher fatty acid in order to reduce durability due to dissolution of the surfactant. No. 1, but this technology does not take into account frost prevention at all.

On the other hand, as a means to prevent frost formation, the Japanese Patent Publication No. 53-161
No. 38 proposes that a melting point depressing substance be periodically injected into a pressurized container, but this is mainly a means of preventing frost formation inside a refrigerator, and the outdoor heat exchanger of a heat pump with a large number of fins has a uniform temperature. It is difficult to spray properly, and the provision of a pressure vessel increases the size of the device, which is undesirable. In addition, as an alternative method, a method of forming a hydrophobic film on the fin surface is disclosed in JP-A-54-1391/59, but although it may suppress frost formation, it does not prevent the formation of water droplet bridges during defrosting. Problematic and undesirable.

Furthermore, JP-A No. 60-102978 discloses a method of imparting hydrophilicity by forming a film on the surface of the object to be coated by fixing ion-exchange resin powder with an adhesive. The method is limited to improving the workability and water wettability of the fin material.

As described above, no technology has been found that can simultaneously solve the problems of water wettability and sustainability and the suppression of frost formation, and there has been a strong desire in the market for the development of an effective means. Ikegata: It is clear that a water-based treatment agent for the paint composition meets market needs from the standpoint of preventing fires on painting lines, health of workers, and saving resources.

In view of the problems that the invention aims to solve, an object of the present invention is to provide an aqueous coating composition that has excellent water wettability and durability when applied to aluminum fins of a heat exchanger, and is effective in suppressing frost formation. , and coat the heat transfer surface with such aqueous coating composition. ! It is an object of the present invention to provide an overturned heat exchanger.

Means for Solving the Problems The present inventors have conducted research into the formation and growth mechanisms of frost formation, and have found that the frost formation and growth process begins with water droplets condensing when the fin surface is below the dew point. After that, the water droplets or water film (when water wettability is good) freezes, so-called ice crystallization occurs, and frost nuclei are formed on top of them.Then, moisture in the air adheres to the nuclei by sublimation phenomenon, and the growth of frost is inhibited. I confirmed that it happens. It is obvious that if the height of frost on the aluminum fins of the heat exchanger on the outdoor side can be lowered, heating operation can be continued for a long time, which is desirable. The present inventors found that in the frosting process, after the water film turns into ice crystals, there is no way to control the sales amount other than by controlling external factors such as wind speed, temperature, humidity, and fin shape. If this was due to factors other than the above, it was determined that some kind of countermeasure was needed before the water film turned into ice crystals. As a result of extensive research, they discovered a method to delay ice crystallization by eliminating as much of the water film on the surface as possible when water droplets condense at temperatures below the dew point.

In other words, this is a method of delaying crystallization by allowing the surface treatment film to absorb water. However, even if water is absorbed, if there is no method for dehydrating it, there will be no effect at all if the water content exceeds the absorption capacity. The inventors of the present invention have discovered the surprising fact that the height of frost can be kept low by using a water-absorbing and desorbing polymer as a coating film material. In other words, the time to crystallization can be delayed by absorbing water, and by raising the temperature during defrosting, it is possible to return to the pre-frost state through dehydration, which maintains the efficiency of the heat exchanger. Gender was resolved. Furthermore, the present inventors have discovered that the time required for ice crystallization can be further extended by incorporating water-absorbing saccharides and/or alkali metal salts into the water-absorbing and dehydrating coating film.

Based on this knowledge, the present invention provides a coating composition having the following composition which, when applied to aluminum fins of a heat exchanger, can provide a coating that has water wettability, durability, and is useful for inhibiting frost formation. Provided. That is, the coating composition of the present invention is a composition containing a water-absorbing and desorbing polymer emulsion (hereinafter simply referred to as a water-absorbing and desorbing polymer emulsion) and a saccharide and/or an alkali metal salt within a range in which the entire system has film-forming ability. It is.

The water-absorbing and desorbing polymer emulsion of the present invention is an N-alkylene-substituted acrylamide represented by the general formula: homopolymer, two types of copolymers and the N-
It is an emulsion of at least one kind of polymer selected from the group consisting of copolymers of alkylene-substituted acrylamide and copolymerizable monomers. The copolymerizable monomers include hydrophilic monomers, ionic monomers, and lipophilic monomers. Examples of hydrophilic monomers include acrylamide, methacrylamide, N-methylol acrylamide, N-methylol methacrylamide, diacetone acrylamide, methylol acrylamide, hydroxyethyl methacrylate, hydroxyethyl acrylate, hydroxypropyl methacrylate, hydroxypropyl acrylate, and various other hydrophilic monomers. Methoxypolyethylene glycol (meth)acrylate, N-vinyl-2-
Examples include pyrrolidone. Examples of ionic monomers include acrylic acid, methacrylic acid, vinylsulfonic acid, allylsulfonic acid, methallylsulfonic acid, styrenesulfonic acid, 2-acrylamido-2-phenylpropanesulfonic acid, and 2-acrylamido-2-methyl-propane. Acids such as sulfonic acids and their salts, N,N-dimethylaminoethyl methacrylate, N,N-diethylaminoethyl methacrylate, N,N-dimethylaminoethyl acrylate, N,N-dimethylaminopropylmethacrylamide, N,N- Examples include amines such as dimethylaminopropylacrylamide and salts thereof. Lipophilic monomers include (meth)acrylate derivatives such as ethyl acrylate, methyl methacrylate, butyl methacrylate, butyl acrylate, lauryl acrylate, 2-ethylhexyl methacrylate, glycidyl methacrylate, acrylonitrile,
Methacrylonitrile, vinyl acetate, vinyl chloride, vinylidene chloride, olefins such as ethylene, propylene, butene, styrene, divinylbenzene, α-methylstyrene, butadiene, isoprene, N-methoxymethylacrylamide, N-ethoxymethylacrylamide, N
-N-alkoxymethyl (meth)acrylamide derivatives such as n-propoxymethylacrylamide, N-n-butoxymethylacrylamide, N-n-butoxymethylmethacrylamide, N-inbutoxymethylacrylamide, N-t-octoxymethylacrylamide, etc. etc. can be mentioned.

An aqueous composition containing a polymer of the above-mentioned monomers changes its hydrophilicity and hydrophobicity depending on the temperature. For example, if it is water-soluble, it becomes hydrophobic by heating and becomes cloudy (the temperature at that time is changed). point). Further, when the aqueous composition forms an emulsion, the viscosity of the solution decreases by heating. In addition, the other copolymerizable monomers such as hydrophilic monomers and ionic monomers are useful for repurposing the emulsion surface and stabilizing the emulsion itself.

In producing the water-absorbing and desorbing polymer emulsion of the present invention, the quantitative ratio of the acrylamide derivative and the various other monomers mentioned above to be combined therewith may vary depending on the combination of these monomers. do not have. However, in the case of hydrophilic monomers, the amount is 60% by weight or less based on the total amount of monomers,
The content of the ionic monomer is preferably 40% by weight or less, and the ionic monomer content is 30% by weight or less, preferably 20% by weight or less, based on the total amount of monomers. On the other hand, the lipophilic monomer accounts for 8% (1% by weight or less, preferably 60% by weight or less) of the total monomer amount.

Next, in order to obtain a polymer having excellent water insolubility and forming a smooth coating film by polymerizing the monomers or their monomer mixtures, it is necessary to form seed particles and carry out emulsion polymerization. .

Specifically, first, a portion of the monomer to be polymerized is polymerized to form seed particles that will become the core of the emulsion particles. Next, further monomers are added to cause polymerization to occur in the seed particles, thereby allowing emulsion polymerization to proceed. That is, water is used as the reaction medium, and specifically, ion-exchanged water, distilled water, tap water, industrial water, etc. are used. When a lipophilic monomer is used in combination, a common surfactant such as an alkyl sulfate, an alkylaryl sulfonate, a fatty acid soap, or the above-mentioned ionic monomer may be used as necessary. An emulsion of the monomers can be formed, followed by emulsion polymerization. On the other hand, when (meth)acrylamide derivatives are used alone or in combination with hydrophilic or ionic monomers, the monomers are usually water-soluble and cannot be emulsified. Emulsification of the polymer occurs by dissolving the activator or ionic monomer and heating it to a polymerization initiation temperature above the polymer deposition point, and then adding the monomers described above. Emulsions, ie water-absorbing and dehydrating polymer emulsions, can be produced.

As the polymerization initiator used in the polymerization, any water-soluble radical polymerization initiator such as persulfate can be used, and of course it is also possible to use a redox type initiator. Specifically, examples include ammonium persulfate, potassium persulfate, hydrogen peroxide, tert-butyl peroxide, and redox initiators, and examples of reducing agents combined with the above-mentioned oxidizing agents include sulfites, hydrogen sulfites, iron, Examples include salts with low ionic valences such as fed cobalt, organic amines such as aniline, and reducing sugars such as aldoses and ketoses. In addition, as an azo compound,
2-2'-azobis-2-amidinopropane hydrochloride, 2
-2''-azobis-2,4-dimethylvaleroni-1-lyl, 4,4''-azobis-4-cyatubaleic acid and its salts, etc. can be used.Also, two or more of the above polymerization initiators can be used. It is also possible to use them together.The polymerization temperature varies depending on the polymerization initiator used, or is usually 0 to 1.
00°C1 is preferably 5 to 90°C, and is in a range equal to or higher than the deposition point of the polymer.

The polymer concentration, which is the polymer content in the aqueous composition, is not particularly limited, but is approximately 5 to 60%.

As a specific method for producing a polymer emulsion, it is essential to first produce seed particles at a temperature below -F at which the polymer is insoluble. The monomer constituting the seed may be the (meth)acrylamide derivative shown in the above-mentioned item, a lipophilic monomer alone, a mixture thereof, or a hydrophilic monomer. May be used together. The proportion of the monomers added to produce the seed particles in the total monomers is 0.1 to 40% by weight, preferably 0.2%.
It is 5-30%.

Next, regarding the polymerization time, the polymerization time for seed particle formation was 10
~120 minutes, and the polymerization does not necessarily need to be completed; it is sufficient that the polymerization solution becomes cloudy and particles are formed. Monomers are then added thereto for emulsion polymerization. At this time, the entire amount of monomers may be added at once, but to ensure stable polymerization, it is necessary to add them continuously or sequentially. It is preferable to add it to At this time, a polymerization initiator may also be added at the same time as the monomer addition. The time required for its addition depends on the amount of monomer to be added;
~10 hours. Furthermore, in order to polymerize and eliminate monomers that remain even after addition, it is preferable to continue polymerization for 1 to 5 hours.

Throughout the above polymerization, it is preferable to replace oxygen-containing gas such as air with an inert gas such as nitrogen in the atmosphere within the polymerization system in order to speed up the polymerization.

In addition, the emulsion of the monomers described above can exist as an emulsion even if the temperature is changed if the ratio of lipophilic monomers is relatively high; however, the ratio of lipophilic monomers decreases, and When the ratio of the (meth)acrylamide derivative becomes relatively high, the polymer becomes an emulsion above the point of attachment, and becomes an aqueous solution or an aqueous gel below the point of attachment of the polymer. Normally, it becomes an aqueous solution below the standing point, but when the molecular weight of the polymer is high, when it is copolymerized with crosslinking monomers such as methylenebisacrylamide, various mono- or polyethylene glycol di(meth)acrylates, or acrylonitrile. In cases where a lipophilic monomer such as the following is added in the early stages of emulsion polymerization and copolymerized, the polymer may take on a gel-like form below the deposition point.

The properties of the water-absorbing and dehydrating polymer emulsion when formed into a coating film are as follows. That is, it has a water respiration effect in that it absorbs water under low or high temperature conditions and releases the absorbed water under high or low temperature conditions. At that time, the amount of water absorbed or released varies depending on the surrounding temperature and humidity conditions, the composition of the coating film, etc., and cannot be stated uniformly, but its maximum value is approximately 10 g per gram of coating film. Moreover, since the solubility in water is suppressed to the utmost, even if the coating film is immersed in water, it will not dissolve but swell and retain its gel-like or film-like shape. The amount of swelling at that time depends on the temperature; the amount of swelling increases at low temperatures, and decreases when heated. Specifically, for example, 1
The ratio of the swelling amount between 0'C and 50°C varies depending on the composition of the coating film, etc., but if the swelling amount at 50°C is 1, then at 10°C it is in the range of 13 to 10 It is in. The swelling amount itself at that time is approximately 5 to 100 times the weight of the dry coating film at 10°C.

Various types of saccharides can be used in the present invention, including monosaccharides, trisaccharides, trisaccharides, tetrasaccharides, and polysaccharides, but in particular, as saccharides that can be stably contained in the aqueous coating composition, Monosaccharides and trisaccharides are preferred. In addition, water-absorbing and dehydrating polymer emulsion (I) and saccharide (
The solid content weight ratio with n) can be used within the range of 30/70 to 90/10, particularly 60/40 to 80/20.
A range of is preferred. If the saccharide (n) is mixed in 70% by weight or more of the total solid content of the saccharide (II) and the water-absorbing/dehydrating polymer (I), cracks may occur in the coating film, making it impossible to form a film.

On the other hand, if it is less than 10% by weight, the frost formation suppressing effect of the present invention will be insufficient.

Various alkali metal salts can be used as the alkali metal salts that can be used in the present invention, but those with high water solubility are not preferable for long-lasting frost formation suppression.
Those having a water solubility of 5% by weight or less at 20° C. give particularly good results, and in this sense, acetates and carbonates of alkali metals, especially lithium, are preferably used. The blending amount of the alkali metal salt is selected within the range of 1 to 50% by weight of the total solid content of the water-absorbing/dehydrating polymer (I) and the alkali metal salt (Ill), and if it is less than 1% by weight, the frost formation suppressing effect is low. On the other hand, it has been found that if the amount exceeds 50% by weight, the coating film becomes brittle and lacks practical use. More preferably 5~
It is 20% by weight.

In addition, when using the three components of water-absorbing and desorbing polymer (■), saccharide (II), and alkali metal salt (1) in combination, the amount of water-absorbing and desorbing polymer (I) is calculated based on the total solid content of these three components.
may be selected in the range of 89 to 30% by weight of solid content, 69 to 10% by weight of saccharide (n), and 1 to 50% by weight of alkali metal salt (1). Preferably, the water absorption and desorption polymer (I) The solid content is 75-40% by weight, the sugar (II) is 20-40% by weight, and the alkali metal salt is 5-20% by weight.

The composition of the present invention may also contain resins other than the water-absorbing and dehydrating polymer (I), pigments, extender pigments, dyes, surfactants, and other coating additives, if necessary. Further, in producing the coating composition, common dispersion methods such as steel ball mill, sand grind mill, disperser stirring, etc. can be used.

The composition of the present invention can be applied to the aluminum fins of a heat exchanger using a conventional method, dried, and assembled into the heat exchanger, or the composition can be assembled into the heat exchanger and then dip-coated in the composition and then dried. It is also possible to coat the aluminum fins. The drying conditions after coating are preferably 80 to 200°C for 15 to 20 minutes. In order to achieve the purpose of the present invention, the film thickness after drying is preferably 5 to 100 microns, preferably 5 to 40 microns.

The coating thus treated not only has good water wettability and durability. It exhibits an excellent frost formation suppression effect, effectively suppressing the formation of water droplet bridges, freezing, and frost formation on heat exchanger aluminum fins, and is useful in maintaining good thermal efficiency of ordinary indoor and outdoor heat exchangers. It is something that makes an invention.

The present invention will be explained below with reference to Examples. All parts and percentages are by weight unless otherwise noted.

Production Example 1: Production side of water absorption/desorption polymer emulsion 4.5 g of N-acryloylpyrrolidine and Ojg of sodium 2-phenylpropanesulfonate under 2-acrylamide (hereinafter abbreviated as API'5-Na) were added to 170 g of distilled water and reacted. After purging the inside of the vessel with nitrogen gas, it was heated to 60°C. Then, 0.6 g of potassium persulfate was added to the reaction solution.
Polymerization was started and continued for 60 minutes to obtain a seed particle dispersion. To the thus obtained seed particle dispersion, 5.5 g of N-acryloylpyrrolidine was added, followed by 4 g of acrylonitrile. After the addition was complete, the reaction solution was allowed to react at 60° C. for an additional 4 hours. The polymerization proceeded in a uniform emulsion state without any string-like precipitation of polymer.

The viscosity of the obtained polymerization liquid was measured at 50°C, 25°C and 10°C, and the results are shown in Table 1. At that time, the polymerization solution was 50℃
It was in an emulsified state at 25°C and at 10°C, and was a translucent aqueous gel.

Further, the above-mentioned polymerization solution was applied with a brush onto a Teflon sheet measuring 12cm x 12cm square, and the sheet was dried at 125°C for 2 hours to form a coating film. The resulting coating film had an even thickness and a smooth surface. When the coating film was peeled off from the Teflon sheet and its thickness was measured, it was found to be 0.2 mm. When the coating film was immersed in water, it absorbed water and became a hydrogel film. At that time, the temperature of the immersing water was changed to 1O125, 50°C, and the amount of swelling per 1 g of the coating film was measured and shown in Table 1.

Production Example 2 N-acryloylpyrrolidine was added to 83g of distilled water. Og and APl'5-NaO, 1 g were added, and the inside of the reactor was purged with nitrogen and heated to f&60°C. Next, 0.06 g of potassium persulfate was added to the reaction solution to start polymerization.
Polymerization was carried out for 30 minutes. The reaction solution gradually became cloudy as the polymerization progressed, and seed particles were generated. An aqueous solution consisting of 10 $ of distilled water and 5.0 g of N-acryloylpyrrolidine was slowly added dropwise to the thus obtained seed particle dispersion at the same temperature over 1 hour, followed by further polymerization for 2 hours. The viscosity of the obtained polymerization liquid was set to 50°C and 125°C.
and 10°C, and the results are shown in Table 1. The polymerization solution was in an emulsified state at 50°C and transparent at 25°C and 10°C.

In addition, the above polymerization solution was applied with a brush to a Teflon sheet measuring 1 2 cm x 1 2 cm, and then heated at 125°C for 2 hours.
After drying for a while, a paint film was formed. The resulting coating film had an even thickness and a smooth surface. When the coating film was peeled off from the DEFRON sheet and its thickness was measured, it was found to be 0.2 mm. When the coating film was immersed in water, it absorbed water and became a hydrogel film. At that time, the temperature of the immersing water was changed to 10.25.50°C, and the amount of swelling per tg of coating film was measured and shown in Table 1.

Production Example 3 Distilled water 110g, N-acryloylpyrrolidine 0.7
gN-acryloylpiperidine 2.1g, sodium 2-acrylamido-2-methylpropanesulfonate 0.
Seed particles were produced in exactly the same manner as in Example 2, except that 2 g of potassium persulfate and 0.1 g of potassium persulfate were used. 35 g of distilled water, N
-Acryloylpyrrolidine 2.1g, N-acryloylpiperidine 6.2g, AMPS-Na(t) 0.2g
An aqueous solution consisting of the above was added dropwise at the same temperature over 1 hour, and then polymerization was carried out for 4 hours. The viscosity of the resulting polymer solution and the amount of swelling of the coating film were measured in exactly the same manner as in Production Example 2, and the results are shown in Table 1.

Example 1 200 parts of the water-absorbing and dehydrating polymer obtained in Production Example 1 was placed in a 500 m, E stainless steel container, and 3 parts of sodium carbonate powder was gradually added while stirring with a stirrer to obtain a composition.

Examples 2 to 6 Compounds 111 having the following compositions were prepared in the same manner as in Example 1. The results are shown in Table 2.

(Left below) Each composition of Examples 1 to 6 was placed on an aluminum plate (10 cm x 20
Ω×1 city) using a bar coater to a dry film thickness of 10 μm, and dried at 140° C. for 20 minutes to prepare a test piece.

In addition, an untreated aluminum plate (10 cm x 20 cm x
1 mm) was defined as Comparative Example 1. Using these, the following tests on water wettability, durability, and frost formation suppression effect were conducted, and extremely satisfactory effects were obtained for Examples 1 to 6, but no satisfactory effects were obtained for Comparative Example 1. Ta. The results are shown in Table 3.

Trial 1 Scrap method - Water wettability: Using Wider #71 (manufactured by Iwakuni Painting Machinery Co., Ltd.), pure water was sprayed once on the test piece in a mist-like manner, and the spread of water droplets was observed.

○...Good water wettability ×...Poor water wettability Sustainability of water wettability: The test piece was immersed in pure water at 20°C for 8 hours and then pulled out for 20 hours.
The water wettability after 5 cycles was determined by the water wettability test method described above, with one cycle being air drying at 16 hours at °C.

Frost formation suppression effect: The above test piece was brought into close contact with the cooling plate of the apparatus shown in the reference diagram, and the frost formation height was measured under the following conditions.

Air temperature (DB) 20℃ Air temperature (WB) 14.5℃ Average wind speed in duct 0.5m/s Sample surface temperature
The entire −10°C apparatus is installed in a thermostatic chamber where temperature and humidity can be controlled. The average wind speed in the duct is calculated from the value obtained from the nozzle differential pressure type airflow meter, and is maintained at 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 can move perpendicular to the cooling plate and read the distance, and we measured 60
The height of the frost surface was measured after 1 minute.

For the frost height, the average value (mu) of the measurement results at multiple points was used.

(Left below) Example 7 Using a roll coater, the coating composition obtained in Example 1 was applied to a rolled fin material for an aluminum heat exchanger that had been previously degreased to a dry film thickness of 10 μm. ,
Drying treatment was performed at 140°C for 20 minutes.

Example 8 The coating composition obtained in Example 3 was applied to a rolled fin material for an aluminum heat exchanger and dried in the same manner as in Example 7.

The heat exchanger obtained by assembling the fins treated in Examples 7 and 8 was used as an outdoor heat exchanger during heating operation of a heat pump type air conditioner, and was operated under conditions where frost formation occurred. The relationships between the elapsed time and heating capacity, and the elapsed time and air volume were investigated, and the results are shown as A and B in the attached figures 1 and 2, respectively. It showed good air volume and heating capacity change, ie heat exchange characteristics.

Comparative Example 2 The same beat pump type air conditioner as that used in Examples 7 to 8 was used, but the above coating composition was not applied to the fin material of the outdoor heat exchanger, and heating operation was performed in the same manner as in Examples 7 to 8. We investigated the relationship between elapsed time and heating capacity, elapsed time and air volume, and
The results are shown as C in FIGS. 1 and 2 of the attached drawings. Performance was poor in both tests.

[Brief explanation of drawings]

Figure 1 shows heating operation of a heat pump air conditioner using heat exchangers (A) and (B) coated with the coating composition according to the present invention and a heat exchanger (C) without the coating. FIG. 2 is a diagram showing the relationship between elapsed time and heating capacity; FIG. 2 is also a diagram showing the relationship between elapsed time and air volume; the reference diagram is a diagram of the equipment used in the frosting test on the painted test board. In addition, in the reference diagram, 1 is an air flow, 2 is a duct, 3 is a hot wire anemometer sensor, 4 is a hot wire anemometer, 5 is a cooling plate, 6 is a test piece, 7 is a frost height measuring device, 8 is a heat insulating material, 9 is a brine cooling tank, 10 is a pump, 11 is a chamber, 12 is a nozzle differential pressure airflow meter, and 13 is a fan. patent application agent

Claims (2)

[Claims] (1) Homopolymer of N-alkylene-substituted acrylamide represented by the general formula ▲ Numerical formula, chemical formula, table, etc. ▼ (In the formula, A is -(CH_2)-_n, and n is 4 or 5.) , an emulsion (I) of at least one or more polymers selected from the group consisting of two types of copolymers and copolymers of the N-alkylene-substituted acrylamide and other copolymerizable monomers; and A coating composition comprising a saccharide (II) and/or an alkali metal salt (III) within a range such that the entire system has film-forming ability. (2) Homopolymer of N-alkylene-substituted acrylamide represented by the general formula ▲ Numerical formulas, chemical formulas, tables, etc. ▼ (In the formula, A is -(CH_2)-_n, and n is 4 or 5.) , two types of copolymers, and copolymers of the N-alkylene-substituted acrylamide and other copolymerizable monomers. ) and a saccharide (II) and/or an alkali metal salt (III) within a range that allows the entire system to form a film.