JP2003138221A - Coating composition for heat exchange plate and for fin material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a coating composition for a heat exchange plate and for a fin material which can be made in a smaller size than a brazing plate fin type and has a higher pressure resistance than a plate type. SOLUTION: A composition mainly comprising 100-5,000 pts. nickel component and 100 pts. binder consisting of a polyvinyl acetal resin is applied to a stainless steel sheet so as to form a 120 μm-thick dry film and dried in a 200 deg.C atmosphere for 5 min, thus giving a coating composition for a heat exchange plate or for a fin material.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat exchange plate of a heat exchanger for exchanging heat between a plurality of fluids having different temperatures via a metal or an alloy separating the fluids, and a pipe for passing the fluids therein. The present invention relates to a coating composition used for a heat exchange plate constituting a wall surface of a duct or the like.

[0002]

2. Description of the Related Art Heat exchangers, pipes and ducts for sending fluids are usually made of metal. Since metals generally have excellent heat transfer properties, they are optimal as materials for heat exchangers. On the other hand, pipes and ducts for sending liquids and gases are often made of metal because of their strength.

A heat exchanger used as a heater core, a radiator, a condenser or the like has a core portion in which a large number of heat transfer tubes each formed in a flat tubular shape and a large number of corrugated fins are alternately stacked. Both ends of the plurality of heat transfer tubes are made to communicate with a pair of headers or tanks, respectively. When using such a heat exchanger,
A fluid such as cooling water or a refrigerant is passed between the pair of headers or tanks through the plurality of heat transfer tubes. Then, heat exchange is performed between this fluid and the air or liquid flowing while passing through the core portion.

Conventionally, an aluminum alloy has been used to form the heat transfer tubes and fins of the heat exchanger as described above. For example, in the case of a heat exchanger used as a heater core or a radiator, a heat transfer tube, a sacrificial material on the inner peripheral surface side of the core material, and a brazing material on the outer peripheral surface are laminated (clad). It is made of clad material. Further, as an aluminum alloy constituting the core material, 30
03 material (JIS H4000) as an aluminum alloy constituting the above sacrificial material, 7072 material (JIS H4000)
4000) is generally used as the aluminum alloy composing the brazing material. Furthermore,
As the aluminum alloy forming the fins, the one in which the Zn content of the 3003 material is increased to 1.5% by weight to make the potential base is generally used. By such a combination, corrosion of the core material is suppressed, and required durability (corrosion resistance) is secured.

If all the heat transfer tubes and fins are made of aluminum alloy, the wall thickness of the heat transfer tubes cannot be extremely thinned in order to secure required strength and durability. Therefore, although the aluminum alloy itself is a metal having a small specific gravity and a good heat transfer coefficient, there is a limit to weight reduction and improvement of heat exchange performance. If the heat transfer tube is made of a stainless steel plate having far better corrosion resistance than an aluminum alloy, the wall thickness of the heat transfer tube can be made much thinner than that of a case of being made of an aluminum alloy, resulting in weight reduction and heat resistance. Exchange performance can be improved.

Heat exchangers are widely used in various industries as a device for transferring heat from a high temperature fluid to a low temperature fluid. Such heat exchangers include multi-tube type, double-tube type, spiral plate type, brazing plate fin type, plate type, scraped surface type, etc., which are appropriately used depending on the application.

Among these, the brazed plate fin type heat exchanger and the plate type heat exchanger have a wider heat transfer area than the other methods when compared in the same volume, and the heat transfer area can be easily increased or decreased by increasing or decreasing the plates. It is suitable for small-scale applications because it has excellent design flexibility such as changeable.
It is also used in small appliances, such as household appliances.

By the way, in recent years, in the field of such a small heat exchanger, there is an increasing demand for products having higher efficiency and lower price, but the present brazing plate fin type has a limit to downsizing. On the other hand, the plate type has a low withstand pressure, and there is a problem that it is difficult to obtain a small-sized and high-efficiency heat exchanger without significantly increasing the price in any type.

[0009]

SUMMARY OF THE INVENTION In view of the above situation, an object of the present invention is to provide a heat exchange plate and fins that can be made smaller than the brazed plate fin type and have higher pressure resistance than the plate type. A coating composition for lumber.

[0010]

According to the present invention, there is provided a coating composition for heat exchange plates and a coating composition for fins, which is characterized by containing a binder and a nickel component as main components.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention is a stainless steel plate in which punched stainless steel plates are laminated and bonded to each other, and holes formed in the stainless steel plates or spaces connected to them are used as fluid passages. The gist of the invention is a steel plate laminate type heat exchanger, and a coating composition for a stainless steel plate laminate type heat exchanger, wherein the stainless steel plates are joined by brazing.

As a result of intensive studies to solve the above problems, the present inventor has found that a nickel component can be surely formed into a film on the surface of a stainless steel sheet by using a predetermined binder and a nickel component as main components. Further, they have found that a heat exchanger can be produced at a lower cost than by using a nickel foil by joining them by brazing, and completed the present invention.

The material used for the heat exchanger used in the present invention is copper or copper alloy, aluminum or aluminum alloy, which is excellent in thermal conductivity, or inexpensive carbon steel, except for special applications. Low alloy steel, and stainless steel and the like are considered when corrosion resistance to the fluid and environment used is a problem. Among these materials, stainless steel has a higher strength than other general-purpose materials, and thus the same base material strength as other materials can be obtained with a material having a smaller cross-sectional area. Therefore, if the laminate is made of stainless steel, it is most advantageous for downsizing the heat exchanger. Further, since stainless steel has excellent corrosion resistance as compared with other general-purpose materials, there are many options for the heat medium that can be used, and therefore, there is an advantage that, for example, a substance having a larger latent heat can be used.

The reason why the material used for the laminate in the present invention is stainless steel is because these points are taken into consideration, and to provide a heat exchanger that is smaller and has a wider range of applications. The stainless steel used in the present invention may be any of ferrite type, austenite type, martensite type, two phase type and precipitation hardening type, and the impurities contained may be at the level of general commercial steel.

The binder used in the present invention adheres to a material such as a stainless steel plate and decomposes when it is thermally decomposed. In the present invention, what is decomposed when thermally decomposed means that the mass loss is 9 at a predetermined temperature (preferably 500 ° C.) in a thermal analysis by a thermogravimetric measuring device.
5% or more.

As specific examples, polyvinyl acetals synthesized by a known method (for example, those having a polymerization degree of 200 or more and 2500 or less and an acetalization degree of 60 to 70% or a butyralization degree of 60 to 81.6%, specifically, Examples thereof include formal resin and butyral resin), cellulose derivatives (eg, cellulose esters such as acetyl cellulose and nitrocellulose, cellulose ethers such as methyl cellulose, ethyl cellulose, benzyl cellulose, carboxymethyl cellulose), epoxy resins (eg alkylene). Glycidin ethers of glycol polyethers such as polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, polyoxytetramethylene glycol diglycidyl ether And acrylic resins. These are used alone or in combination of two or more.

In the present invention, a resin in which the constituent elements of the binder are composed of carbon and hydrogen or carbon, hydrogen and oxygen and does not have a benzene ring structure, specifically, a polyvinyl acetal resin, a cellulose derivative or an acrylic resin is used. Is preferably used.

The binder used in the coating composition of the present invention is preferably decomposed by heat at 500 ° C. This is because the binder component is carbonized when it is not thermally decomposed, and the bonding strength after brazing is reduced.

The nickel component in the present invention melts during brazing and bonds the heat exchange plate and the fin material. In brazing joining of stainless steel plates, a copper component may be considered in addition to the nickel component, but the copper component is inferior in corrosion resistance to the nickel component and is not suitable in the present invention. The lower the temperature during brazing, the better the working efficiency, and the melting temperature of the nickel component is desired to be as low as possible, so alloyed nickel is preferable to pure nickel. As a specific example, BNi-1, BNi-1A, BNi-2, BNi-3 for nickel brazing material for metal joining,
BNi-4, BNi-5, BNi-6, BNi-7, BNi-8, etc. can be mentioned. In particular, BNi-
2, BNi-5 and BNi-7 are particularly preferable because they have high bonding strength after brazing.

A typical form of the nickel component used in the present invention is metallic nickel powder, but it is also possible to use a metallic nickel powder and a paste made of water, a solvent, a resin or the like. Moreover, it is not limited to these. In consideration of forming a uniform film when the nickel component is powdery, the average particle size is 20 μm to 150 μm.
It is preferably μm.

The coating composition of the present invention comprises the above binder and the above nickel component in the following formula: binder: nickel component = 100:
It is preferable to mix in a ratio of 100 to 100: 5000 (solid content ratio). More preferably, the binder: nickel component = 100: 500 to 100: 5000.

1 part of nickel component is added to 100 parts of the binder.
When the amount is less than 00 parts, the coating composition film is not preferable because the binder component is decomposed during brazing, resulting in a large decrease in film thickness and a decrease in bonding strength between the heat exchange plate and the fin material. On the other hand, if it exceeds 5000 parts, the amount of the binder is small, so that the adhesion to the material (stainless steel plate) is deteriorated and the handling property is deteriorated, which is not preferable.

As the solvent used in the present invention, water, an organic solvent or the like can be used without particular limitation as long as it can dissolve the binder, disperse the nickel component and liquefy the coating composition. Therefore, it is preferable to use a solvent having a boiling point of 80 ° C. or higher. As the solvent, it is also possible to mix and use various solvents.

The coating composition of the present invention can be prepared by mixing the above binder and the above nickel component.

It is preferable that the coating composition of the present invention is optionally liquefied by optionally adding components such as pigments and additives which are usually used in the production of coating materials and mixing them.

The coating composition of the present invention can be coated by a known coating method. To bond the heat exchange plate and the fin material, it depends on the processing accuracy of the object to be coated, but in order to maintain the bonding force after brazing, the coating composition of the present invention should be coated with a dry film thickness of 30 μm to 200 μm. Is preferred.
As a coating method, roll coating and screen coating are preferable coating methods.

The stainless material having the coating composition coating of the present invention was subjected to 1000 times under vacuum by the above method.
By allowing the binder in the coating film to be thermally decomposed by leaving it in an atmosphere of a high temperature of ℃ or more, only nickel powder remains in the coating film, and brazing between the objects to be coated becomes possible.

[0028]

EXAMPLES The present invention will be described in more detail below with reference to examples and comparative examples.

Example 1 100 parts of polyvinyl acetal resin (manufactured by Sekisui Chemical Co., Ltd .; S-REC BM-2: decomposition peak temperature 364 ° C., decomposition weight loss rate at 500 ° C. 100%), 200 parts benzyl alcohol and Solvesso # 150.
(Shell, trade name: aromatic hydrocarbon solvent) 200 parts of a mixture is dissolved by heating at 80 ° C. with stirring. Nickel powder (manufactured by Shinwa Co .;
4900 parts of Nicroblaze LM: BNi-2 standard powder) was gradually added. Benzyl alcohol / Solvesso #
150 = 1/1 solution with composition viscosity of 150P / 20 ° C
I adjusted it so that.

The obtained composition was applied to a degreased processed stainless steel plate (SUS316) having a thickness of 0.8 mm so that the dry film thickness would be 120 μm using a screen printer, and the composition was dried at 200 ° C. It was heated and dried in an atmosphere for 5 minutes to obtain a stainless steel plate having a coating. The following evaluations were performed on the obtained stainless steel sheets. The results are shown in Table 1.
Shown in.

<Coating state> The appearance of the coating film was visually observed and the coating film state was evaluated according to the following criteria. ○: No abnormality ×: Coating film defect

<Adhesion> An X-shaped cut (X
(Cut) was attached with a cutter knife, and a cellophane adhesive tape was attached thereon and peeled off, and the adhesiveness was evaluated according to the following criteria (according to JIS K5400 8.5.3). ◯: There is no peeling on the coating ×: Peeling occurred on the coating

<Joinability> A stainless steel plate was temporarily fixed using a tool, and the temperature was gradually raised to 1100 ° C. in an environment of 10 ⁻⁵ Torr using a vacuum furnace to perform vacuum brazing.
The following criteria evaluated the joining nature of a brazing part. ◯: The joint does not easily peel off ×: The joint easily peels off

<Corrosion Resistance> The stainless steel sheets produced by the above-mentioned bondability test were immersed in seawater at 80 ° C. for 200 hours to evaluate the corrosion resistance of the stainless steel sheets according to the following criteria. ○: Good corrosion resistance ×: Corrosion occurred, poor corrosion resistance

Example 2 A coating composition was prepared in the same manner as in Example 1 except that 4900 parts of the nickel powder was reduced to 500 parts, and the coating film was evaluated. The results are shown in Table 1.

Comparative Example 1 A coating composition was prepared in the same manner as in Example 1 except that the nickel powder was replaced with copper powder (Shinwa Bronze Blow Wax Bloat # 1). An evaluation was made. The results are shown in Table 1.

Comparative Example 2 A coating composition was prepared in the same manner as in Example 1 except that the binder was not used and only the nickel component was used, and the coating film was evaluated. The results are shown in Table 1.

Comparative Example 3 A coating composition was prepared in the same manner as in Example 1 except that the nickel component was not used and only the binder was used, and the coating film was evaluated. The results are shown in Table 1.

[0039]

[Table 1]

[0040]

As described above, according to the present invention, it is possible to provide a coating composition capable of forming a nickel coating for brazing on the surfaces of a heat exchange plate and a fin material inexpensively and accurately and reliably. Became.

Continuation of the front page (51) Int.Cl. ⁷ Identification symbol FI theme code (reference) // B23K 101: 14 B23K 101: 14 (72) Inventor Susumu Nakai 309-7 Handa, Kaizuka, Osaka (72) Inventor Hiro Mihara 2-13-23 Wakabadai, Taira-gun, Ikoma-gun, Nara F-term (reference) 4J038 BA021 CE061 CE071 CG141 DB031 HA066 NA11 PB09 PC02

Claims (5)

[Claims] 1. A coating composition for a heat exchange plate, which comprises a binder and a nickel component as main components. 2. A coating composition for a heat exchange fin material, which comprises a binder and a nickel component as main components. 3. The coating composition according to claim 1, wherein the binder and the nickel component are liquefied with a solvent. 4. The binder thermally decomposes at 500 ° C. 1.
The coating composition according to any one of 1 to 3. 5. The coating composition according to claim 1, which contains 100 parts to 5000 parts (solid content) of a nickel component with respect to 100 parts (solid content) of the binder.