WO2021075335A1

WO2021075335A1 - Heat exchanger and air conditioning device provided with same

Info

Publication number: WO2021075335A1
Application number: PCT/JP2020/038072
Authority: WO
Inventors: 孝仁中島; 広田　正宣; 憲昭山本
Original assignee: パナソニックＩｐマネジメント株式会社
Priority date: 2019-10-15
Filing date: 2020-10-08
Publication date: 2021-04-22
Also published as: JP7442033B2; JP2021063612A; CN113454416A

Abstract

Brazing sheets (10): are each provided with an aluminum alloy core material (11), a brazing material layer (12), and a sacrificial anode material layer (13) that contains zinc; and have bonding surfaces (10a) that constitute a joined section (21) and non-bonding adjacent surfaces (10b) that are adjacent to the bonding surfaces (10a). A fillet (22) is formed at a site that is between the non-bonding adjacent surfaces (10b) and adjacent to the bonding surfaces (10a), and an epoxy-based coating film (14), 10–50 μm in thickness, is disposed on the bonding surfaces (10a) and the fillet (22).

Description

Heat exchanger and air conditioner equipped with it

The present disclosure relates to an aluminum heat exchanger and an air conditioner equipped with the heat exchanger.

A general heat exchanger is usually provided with a pipe and fins, and has a configuration in which a plurality of fins are attached to the outer circumference of the pipe. As the material of the tube, copper (Cu) or an alloy thereof (referred to as "copper material" for convenience) has been used, but in recent years, aluminum (Al) or an alloy thereof (aluminum material) has also been used. As a fin material, an aluminum material is generally used.

When manufacturing a heat exchanger, joining with brazing material is generally used to attach fins to the pipe. If both the pipe and the fin are made of an aluminum material, for example, a brazing sheet in which a brazing material layer is clad (coated) on at least one surface of a core material made of an aluminum alloy is used. Considering the corrosion resistance of the pipe and fins, a brazing sheet in which a brazing material is clad on one surface of the core material and a sacrificial anode material layer is clad on the other surface is used.

As the brazing material, an aluminum-silicon (Si) -based alloy used for brazing an aluminum alloy is generally used, and as a sacrificial anode material, aluminum is generally used in order to make its potential low. An alloy in which zinc (Zn) is added is used. As a typical sacrificial anode material, a brazing material of a general aluminum-silicon alloy with zinc added can be mentioned. As a result, the sacrificial anode material also functions as a brazing material.

As an example of the brazing sheet in which the sacrificial anode material layer is clad, for example, the one disclosed in Patent Document 1 is known. Patent Document 1 discloses an aluminum alloy brazing sheet used for a heat exchanger for an automobile, particularly a passage component of a fluid (cooling water, a refrigerant, etc.), and has good brazing property and excellent after brazing. The components of the core material and the sacrificial anode material are adjusted to achieve the strength and corrosion resistance.

In this brazing sheet, the content of silicon, iron (Fe) and manganese (Mn) in the sacrificial anode material is regulated to 0.15% by mass or less. This is because the formation of Al—Mn—Si or Al—Fe—Mn—Si compounds is suppressed, and the decrease in strength after brazing is suppressed. Further, in this brazing sheet, the silicon content of the core material is regulated to 0.15% by mass or less, and copper is added to the core material in the range of 0.40 to 1.2% by weight. The reason for adding copper is to improve the strength of the core material, increase the potential difference between the core material and the sacrificial anode layer, and improve the anticorrosion effect due to the sacrificial anode action.

Further, as another example of the brazing sheet in which the sacrificial anode material layer is clad, for example, the one disclosed in Patent Document 2 is known. Patent Document 2 also discloses an aluminum alloy brazing sheet used for an automobile heat exchanger, particularly a fluid passage component. In the brazing sheet, not only the core material and the sacrificial anode material but also the brazing material component has a sacrificial anticorrosive effect on both sides and a brazing function on one side thereof and further prevents preferential corrosion of the joint portion. Is also adjusting.

In this brazing sheet, zinc (Zn) is added not only to the sacrificial anode material but also to the brazing material, and copper is further added to the brazing material in the range of 0.1 to 0.6 mass%. Copper is also added to the core material in the range of 0.05 to 1.2 mass%. The purpose of adding copper to each material is different, for the brazing material, to make the potential of the brazing material noble, and for the core material, to improve the strength of the core material.

Japanese Unexamined Patent Publication No. 2010-163674 Japanese Unexamined Patent Publication No. 2013-155404

In the brazing sheet disclosed in Patent Document 1, the strength is improved by adding copper to the core material, and the anticorrosion effect is improved by the sacrificial anode action. However, in this brazing sheet, the silicon content of both the sacrificial anode material and the core material is limited to 0.15% by mass or less, and the core material also contains various metal elements other than copper. It is specified in detail. Therefore, the range of material choices that can be used as the core material and the sacrificial anode material is reduced. Moreover, in this brazing sheet, the silicon content of the sacrificial anode material is regulated to a very small amount. Therefore, it is considered that this sacrificial anode material layer does not have a function as a general brazing material.

In the brazing sheet disclosed in Patent Document 2, by adding copper together with zinc to the brazing material, not only zinc is concentrated at the brazing joint but also copper is concentrated in the same manner. Here, by concentrating (containing) this copper, it is attempted to prevent the potential of the joint portion from being overly based by zinc. However, when copper and zinc are used in combination, as a result of diligent studies by the present inventors, it has been clarified that the preferential corrosive action of the sacrificial anode material layer is reduced and the corrosion resistance is lowered.

For example, depending on the type of heat exchanger, a structure is included in which when the brazing sheets are joined to each other, the angle formed by the respective joint surfaces becomes an acute angle. For convenience, if such a structure is referred to as an "acute-angled joint structure" and a surface that is not joined adjacent to the joint surface of the brazing sheet is referred to as a "non-joint adjacent surface", in such a sharp-angle joint structure, non-joins that form an acute angle with each other Fillets are formed between the adjacent surfaces. This fillet is defined herein as a solidified wax or sacrificial anode material that has flowed out of the joint surface during joining.

When copper and zinc are used in combination in a brazing material as in Patent Document 2, zinc having a low potential and copper having a noble potential coexist in the fillet as described above. If the sacrificial anode material layer is configured to contain copper in advance, the potential of the fillet may be too noble due to copper, the sacrificial anode action of zinc may be reduced, and the corrosion resistance of the fillet may be lowered. In this case, corrosion may proceed from the fillet toward the joint, resulting in a decrease in the joint strength of the joint.

The purpose of this disclosure is to improve the corrosion resistance of aluminum heat exchangers.

The heat exchanger according to the present disclosure is an aluminum heat exchanger, and has an epoxy-based coating film having a thickness in the range of 10 to 50 μm on a part of the surface of the heat exchanger. The heat exchanger is arranged inside the box so that the coating film is not directly irradiated with ultraviolet rays.

With the above configuration, the corrosion resistance of the aluminum heat exchanger can be improved.

FIG. 1A is a schematic cross-sectional view showing a schematic configuration of a brazing sheet according to a typical embodiment of the present disclosure. FIG. 1B is a schematic cross-sectional view showing a schematic configuration of a joining structure of a brazing sheet according to a typical embodiment of the present disclosure. FIG. 2A is a schematic cross-sectional view showing an example of a header of a plate fin laminated heat exchanger constructed by using the brazing sheet shown in FIG. 1A. FIG. 2B is an enlarged schematic partial cross-sectional view of the joining structure of the brazing sheet included in the header shown in FIG. 2A. FIG. 3A is a schematic partial cross-sectional view showing an example of a parallel flow capacitor (PFC) configured using the brazing sheet shown in FIG. 1A. FIG. 3B is an enlarged schematic partial cross-sectional view of the joining structure of the brazing sheet included in the PFC shown in FIG. 3A. FIG. 4 is a schematic cross-sectional view showing a schematic configuration in which a plate fin laminated heat exchanger in which the header shown in FIG. 2A is subjected to dipping coating is installed in an air conditioner. FIG. 5 is a diagram showing the molecular structure of epichlorohydrin / bisphenol A type resin. FIG. 6A is a diagram showing the results of a corrosion resistance test of the coating film arranged on the brazing sheet according to Comparative Example 1. FIG. 6B is a diagram showing the results of a corrosion resistance test of the coating film arranged on the brazing sheet according to Comparative Example 2. FIG. 6C is a diagram showing the results of a corrosion resistance test of the coating film arranged on the brazing sheet according to Example 1. FIG. 6D is a diagram showing the results of a corrosion resistance test of the coating film arranged on the brazing sheet according to Example 2. FIG. 7A is a diagram showing the results of an adhesion test after the corrosion resistance test of the coating film arranged on the brazing sheet according to Comparative Example 1. FIG. 7B is a diagram showing the adhesion test result after the corrosion resistance test of the coating film arranged on the brazing sheet according to Comparative Example 2. FIG. 7C is a diagram showing the adhesion test result after the corrosion resistance test of the coating film arranged on the brazing sheet according to Example 1. FIG. 8A is a diagram showing the results of an adhesion test after the moisture resistance test of the coating film arranged on the brazing sheet according to Comparative Example 1. FIG. 8B is a diagram showing the results of an adhesion test after the moisture resistance test of the coating film arranged on the brazing sheet according to Comparative Example 2. FIG. 8C is a diagram showing the results of an adhesion test after the moisture resistance test of the coating film arranged on the brazing sheet according to Example 1. FIG. 9 is a graph showing the relationship between the thickness of the coating film and the adhesion according to the present disclosure.

The heat exchanger according to the present disclosure is an aluminum heat exchanger, and has an epoxy-based coating film having a thickness in the range of 10 to 50 μm on a part of the surface of the heat exchanger. The heat exchanger is arranged inside the box so that the coating film is not directly irradiated with ultraviolet rays. By using an epoxy-based paint having good adhesion to an aluminum material, it is possible to structurally protect the weather resistance, which is a drawback of the aluminum material, and suppress deterioration and peeling of the coating film.

The coating film may contain a metal powder having a lower potential than aluminum.

The heat exchanger may be configured by using brazing. In this case, the joint between the brazing sheets having a relatively low potential is protected by the sacrificial anodic action of the metal particles having a relatively low potential. Therefore, it is possible to effectively suppress or prevent the possibility that corrosion progresses from the fillet generated adjacent to the joint portion between the brazing sheets to the joint portion and causes a decrease in the joint strength of the joint portion, so that the heat exchanger can be joined. Corrosion resistance in the part can be made even better. That is, even when the potential of the fillet is lower than that of its surroundings, the preferential corrosion of the fillet can be easily and effectively suppressed or prevented, and the corrosion resistance of the heat exchanger can be improved.

In order to protect the joint between the brazing sheets, the joint is concentrated on the header, and the epoxy-based paint containing metal particles whose potential is lower than that of the joint is applied only to the joint and its surroundings. May be overcoated.

The potential evaluation method is not particularly limited, and a known method can be preferably used. Typically, a potential measurement sample (for example, a brazing sheet 10 or a core material 11, a brazing material, a sacrificial anode material, a fillet 22 or a joint portion 21, or a composition simulating these) is used on a potato stat / galvanostat. (Alloy, etc.), the counter electrode, and the reference electrode (for example, silver / silver chloride (Ag / AgCl) electrode) are connected and immersed in an electrolytic solution (for example, 5% by weight & sodium chloride (NaCl) solution) to refer to the sample. A method of measuring the potential difference from the electrode can be mentioned.

As an anticorrosion coating, a multi-layer structure is generally composed of an epoxy-based paint that can obtain suitable adhesion strength to an aluminum material as an undercoat, and a urethane-based paint as a topcoat for the purpose of protecting the undercoat coating film from ultraviolet rays. Used. However, the second and subsequent coats are not desirable from the viewpoint of cost control and environmental protection. As a result of the studies by the inventors, it has been clarified that a structure that sufficiently suppresses the invasion of ultraviolet rays into the painted portion can sufficiently improve the corrosion resistance life as a heat exchanger. Further, when the joints that need to be painted are concentrated on the header portion, even a complicated shape can be painted at once by dip painting, for example. Therefore, the heat exchanger can be produced more easily and the burden on the environment can be reduced. Further, the heat exchange efficiency of the header portion is not as good as that of the fin portion and the heat transfer tube portion. Therefore, when the joint portion is arranged in the header portion, the efficiency decrease can be minimized by making the header portion a relative non-ventilated portion in the entire heat exchanger.

By installing the heat exchanger so that the header portion is located at the vertical bottom of the heat exchanger, the dew condensation water generated during the operation of the heat exchanger can more reliably wash away the peeled coating film or the corrosion products. .. As a result, it is possible to effectively suppress or prevent the scattering of the peeled coating film or the corrosion product, and it is possible to suppress the pollution of the surrounding environment.

Hereinafter, typical embodiments of the present disclosure will be described with reference to the drawings. In the following, the same or corresponding elements will be designated by the same reference numerals throughout all the figures, and duplicate description will be omitted.

(Embodiment 1)
[Blazing sheet]
The heat exchanger according to the present disclosure is configured by using, for example, a brazing sheet made of an aluminum alloy. Specifically, for example, as shown in FIG. 1A, the brazing sheet 10 according to the present disclosure includes a core material 11, a brazing material layer 12, and a sacrificial anode material layer 13. The brazing material layer 12 is coated (clad) on one surface of the core material 11, and the sacrificial anode material layer 13 is the other surface of the core material 11, that is, the surface opposite to the surface on which the brazing material layer 12 is coated. It is covered with. The core material 11, the brazing material forming the brazing material layer 12, and the sacrificial anode material forming the sacrificial anode material layer 13 are all aluminum alloys.

Alternatively, although not shown, the brazing sheet 10 may have a configuration in which the core material 11 and the sacrificial anode material layer 13 are provided, and the brazing material layer 12 is not provided. In such a brazing sheet 10, a sacrificial anode material layer 13 is formed on both surfaces of the core material 11.

The brazing sheet 10 has a joint surface at least on the side of the sacrificial anode material layer 13, and the joint surface is formed by joining the joint surfaces to each other. The structure in which the brazing sheets 10 are joined to each other at the joining surface is the joining structure of the brazing sheets 10. The brazing sheet 10 has a non-joint adjacent surface adjacent to the joint surface. When the brazing sheets 10 are joined together to form a joined structure, the angle formed by the respective non-joined adjacent surfaces is an acute angle.

In the joining structure 20, when the brazing sheets 10 are joined together to form the joining portion 21, a fillet 22 is formed between the non-joining adjacent surfaces 10b as shown in FIG. 1B. The heat exchanger includes a member or structure on which such a fillet 22 is formed, and in such a member or structure, the non-joined adjacent surfaces 10b often form an acute angle. .. In the present embodiment, the fillet 22 is defined as a solidified brazing material (or sacrificial anode material) that has flowed out from the joint surface 10a at the time of joining.

In the heat exchanger using the brazing sheet 10, it is effectively suppressed or avoided that the fillet 22 is preferentially corroded.

In the brazing sheet 10 of the present embodiment, the joint surface 10a is set at least on the sacrificial anode material layer 13. Therefore, as will be described later, the sacrificial anode material also serves as a brazing material. That is, the sacrificial anode material layer 13 contributes to joining the brazing sheets 10 as a brazing material at the time of joining, and contributes to the anticorrosion effect of the brazing sheet 10 as a sacrificial anode material after joining.

In the brazing sheet 10, a non-joint adjacent surface 10b is set adjacent to the joint surface 10a. Therefore, the non-bonded adjacent surface 10b is also the sacrificial anode material layer 13 like the bonded surface 10a.

In the joint structure 20 of the brazing sheet 10, corrosion may proceed in the directions indicated by the block arrows C1 and C2 in FIG. 1B. The direction of the block arrow C1 is the corrosion direction that progresses from the non-bonded adjacent surface 10b to the direction of the core material 11. The direction of the block arrow C2 is the corrosion direction that progresses along the direction of the joint surface 10a at the joint portion 21 including the fillet 22.

Of these, the corrosion that progresses in the corrosion direction C1 is suppressed (avoided or prevented) by the sacrificial anode action of the sacrificial anode material layer 13, but the corrosion that progresses in the corrosion direction C2 is that zinc is concentrated in the fillet 22. Therefore, there is a possibility that the potential of the joint portion 21 including the fillet 22 is too low and progresses. In the brazing sheet 10 according to the present embodiment, the corrosion in the corrosion direction C2 can be effectively suppressed (avoided or prevented) by arranging the epoxy-based coating film 14 on the surfaces of the joint surface 10a and the fillet 22. it can.

[Blazing sheet joint structure and heat exchanger]
The brazing sheet 10 can be particularly suitably used for manufacturing a heat exchanger as described above. The bonding structure 20 formed when the brazing sheet 10 is applied to the heat exchanger has a structure as illustrated in FIG. 1B as described above, but more specifically, it is shown in FIGS. 2A and 2B. Examples thereof include a plate fin laminated heat exchanger having such a structure and a parallel flow capacitor (PFC) having a structure as shown in FIGS. 3A and 3B.

Although not shown, the plate fin laminated heat exchanger is a plate fin laminated body having a flow path through which a refrigerant, which is a first fluid, flows, and air, which is a second fluid, is flowed between each plate fin laminated body to flow the first fluid. Heat exchange is performed between the fluid and the second fluid. The plate fin included in this heat exchanger has a flow path region having a plurality of first fluid flow paths through which the first fluid flows in parallel, and a header flow path communicating with each first fluid flow path in this flow path region. It has a header area and.

In the plate fin laminated heat exchanger, end plates having substantially the same shape as the plate fins in a plan view are provided on both sides of the plate fin laminated body in the laminating direction, and are interposed between these pair of end plates. The plurality of plate fins to be formed are joined and integrated by brazing in a laminated state. FIG. 2A shows a schematic structure of a header portion in the plate fin laminated body 30 as a partial cross section, and a plurality of plate fins 32 are laminated on an end plate 31 located at the uppermost part in the drawing.

An opening is provided in each of the end plate 31 and the plate fin 32, and the header opening 33 is formed by laminating these plates to form the plate fin laminated body 30. In the configuration shown in FIG. 2A, the refrigerant as the first fluid flows in from the outside of the header opening 33 in the direction indicated by the block arrow in the drawing, and further flows in between the plate fins 32. As described above, each plate fin 32 is provided with the first fluid flow path, so that the refrigerant flowing between the plate fins 32 flows through the first fluid flow path. Further, the air, which is the second fluid, flows in the space formed between the plate fins 32 so as to intersect the direction in which the refrigerant flows (the direction of the first fluid flow path). As a result, the air is cooled by the refrigerant.

FIG. 2B is a partially enlarged view of the plate fin laminate 30 shown in FIG. 2A, and schematically shows an example of the joining structure 20 of the brazing sheet 10. In the examples shown in FIGS. 2A and 2B, the plate fin 32 is the brazing sheet 10 according to the present disclosure, and the joint structure 20 is the joint portion 21 located on the header opening 33 side. In FIG. 2B, the plate fin 32, which is the brazing sheet 10, is shown by emphasizing the sacrificial anode material layer 13 with hatching, and also highlighting the fillet 22 with hatching.

At the joint portion 21 on the header opening 33 side, the joint surfaces 10a of the plate fins 32 are joined to each other, and a fillet 22 is formed between the non-joint adjacent surfaces 10b adjacent to the joint surface 10a. In the present embodiment, the epoxy coating film 14 is arranged on the surfaces of the joint surface 10a and the fillet 22. As a result, the preferential corrosion of the joint portion 21 is satisfactorily suppressed (avoided or prevented), so that the corrosion resistance life of the plate fin laminated heat exchanger can be improved.

Specific configuration examples of such a plate fin laminated heat exchanger include, for example, JP-A-2017-180856, JP-A-2018-066531, JP-A-2018-066532, and JP-A-2018-066533. It is described in Japanese Patent Application Laid-Open No. 2018-066534, Japanese Patent Application Laid-Open No. 2018-066535, Japanese Patent Application Laid-Open No. 2018-066536, etc. It shall be a part of the description of the specification.

A parallel flow condenser (PFC) is a heat exchanger widely used for car air conditioners (air conditioners for automobiles). A plurality of flat tubes are arranged between a pair of header tubes, and heat is dissipated between these flat tubes. Corrugated fins are arranged. These header pipes, flat pipes, corrugated fins and the like are joined by brazing. FIG. 3A shows a schematic structure of a connecting portion between the header pipe 41 and the flat pipe 42 in the PFC 40 as a partial cross section. Corrugated fins 43 are provided between the flat pipes 42, and these are also joined by brazing, and the joining structure 20 is a connecting portion between the header pipe 41 and the flat pipe 42, as shown in an enlarged view in FIG. 3B. is there.

In the example shown in FIG. 3B, the header tube 41 and the flat tube 42 are both brazing sheets 10, and the header tube 41 and the flat tube 42 are shown by emphasizing the sacrificial anode material layer 13 with hatching. The fillet 22 is also highlighted by hatching. Since the sacrificial anode material layer 13 of the flat tube 42 is flat, the joint surface 10a and the non-joint adjacent surface 10b are set as different regions on a continuous single surface (the surface of the sacrificial anode material layer 13). Therefore, the flat tube 42 has a flat shape such that the brazing sheet 10 does not have a bent portion.

The header pipe 41 has an opening for penetrating and inserting the flat pipe 42, and the joint surface 10a and the non-joint adjacent surface 10b are provided in the opening. In FIG. 3B, the joint surface 10a of the header pipe 41 is shown as a surface parallel to the joint surface 10a (outer surface) of the flat pipe 42, but the present invention is not limited to this, and the joint surface 10a is parallel to the outer surface of the flat pipe 42. It may be a surface that does not become. The opening of the header tube 41 has a shape having a one-step bent portion as the brazing sheet 10.

In the joint structure 20 shown in FIG. 3B, a fillet 22 is formed between the non-joint adjacent surface 10b adjacent to the joint surface 10a of the header pipe 41 and the non-joint adjacent surface 10b adjacent to the joint surface 10a of the flat pipe 42. Has been done. In the present embodiment, the epoxy coating film 14 is arranged on the surface of the fillet 22. As a result, the preferential corrosion of the joint portion 21 is satisfactorily suppressed (avoided or prevented), so that the corrosion resistance life of the PFC can be improved.

The method for producing the joint structure 20 of the brazing sheet 10 is not particularly limited, and a known brazing method or the like can be preferably used. For example, a method in which a known flux is applied to the joint surface 10a of the brazing sheet 10 and then heated in a nitrogen atmosphere furnace at a temperature of, for example, about 600 ° C. can be mentioned.

[Arrangement form of heat exchanger]
FIG. 4 shows an example of the mode when the above-mentioned plate fin laminated heat exchanger or PFC is arranged in the air conditioner. The air conditioner has a box body 56, and a heat exchanger 51 and a blower fan 53 are arranged in the box body 56. An epoxy-based coating film installation portion 52 on which the above-mentioned epoxy-based coating film 14 is arranged is arranged in a part of the heat exchanger 51. In the example of FIG. 4, the epoxy-based coating film installation portion 52 corresponds to the header portion of the heat exchanger 51. In the present embodiment, as shown in FIG. 4, the epoxy-based coating film installation portion 52 is provided vertically above the drainage receiver 55. The condensed water generated in the heat exchanger 51 during the operation of the air conditioner is received by the drainage receiver 55 and discharged to the outside of the box body 56. The air passage of the second fluid described above is indicated by a block arrow in the figure. The fluid sucked by the blower fan 53 passes through the air filter 54, is heat exchanged by the heat exchanger 51, and is discharged to the outside of the box body 56. At this time, the epoxy-based coating film installation portion 52 constitutes a part of the air passage, but since the air passage is partially blocked by the drainage receiver 55, the epoxy-based coating film installation portion 52 of the heat exchanger 51 The air volume in is smaller than the air volume in the non-installed portion of the coating film. For convenience, the portion where the air passage is relatively blocked is called a non-ventilation portion.

In such a structure, since the epoxy-based coating film installation portion 52 is arranged inside the box body 56, ultraviolet rays from outside the box body 56 are blocked by the box body 56. Therefore, the epoxy-based coating film setting portion 52 is substantially unaffected by ultraviolet rays. As a result, the deterioration of the epoxy coating film 14 by ultraviolet rays is suppressed and the life of the epoxy coating film 14 is extended. Further, the peeled coating film or the corrosion product due to the deterioration of the epoxy-based coating film 14 is almost certainly washed away by the dew condensation water generated from the heat exchanger 51 because the epoxy-based coating film installation portion 52 is a non-ventilated portion. Then, it is received by the drainage receiver 55 and discharged to the outside of the box 56 together with the condensed water. Therefore, the heat exchange can be performed by the heat exchanger 51 while avoiding the above-mentioned products and the like from scattering in the environment where the air conditioning is performed by the air conditioning device.

[Epoxy paint]
The epoxy-based epoxy-based coating material according to the present disclosure has an epoxy group at the terminal and is produced by a ring-opening reaction, and is composed of epichlorohydrin and phenol, alcohol, aldehyde, ester, amine, fatty acid and isocyanate. Refers to the reaction product with one of them (s). The molecular weight is not specified.

FIG. 5 shows the molecular structure of epichlorohydrin / bisphenol A type resin, which is a typical epoxy resin. Epichlorohydrin / bisphenol A type resin has a highly reactive epoxy group at both ends, a rigid bisphenol nucleus as a skeleton, and a structure connected by a flexible ether group. Further, the epichlorohydrin / bisphenol A type resin has a structure in which hydroxyl groups contributing to adhesion are arranged at appropriate intervals. Therefore, it exhibits good adhesion, chemical resistance, water resistance and electrical insulation by utilizing various cross-linking reactions. The base of aluminum to be painted is covered with a dense and smooth oxide film, and generally, suitable adhesion cannot be obtained without base treatment such as chromate treatment or blast treatment. However, the epoxy-based paint has adhesiveness that can withstand the rust-preventive purpose of the heat exchanger without the base treatment for the above-mentioned reason. Therefore, the painting process can be simplified.

Further, it is desirable that the epoxy-based paint contains a metal powder having a lower potential than aluminum in a pure water or salt water environment such as zinc oxide or zinc powder for the purpose of improving corrosion resistance. Although lead or indium can be used instead of zinc, zinc and its alloy (for example, an alloy of aluminum and zinc) are desirable from the viewpoint of environmental protection and cost control. The amount to be added is not particularly specified, but the amount to be added is set so that the sacrificial anodic action can be sufficiently obtained. The particle size of the powder is not particularly specified, but it is desirable that the powder has an order of several μm or less so that the powder is uniformly dispersed as a paint.

As the diluting solvent, one having high compatibility with the above-mentioned epoxy paint components is selected. Typical examples include, but are not limited to, ethylbenzene, xylene, toluene, methylethylketone and the like. Since the viscosity of the coating material changes depending on the dilution ratio, and as a result, the thickness of the coating film after coating changes, the amount of the diluting solvent is adjusted so as to obtain the desired coating film thickness.

In addition, a component that improves the durability of the epoxy-based paint, for example, various weather-resistant agents for compensating for the fragile weather resistance (ultraviolet ray resistance) that is a drawback of the epoxy-based paint may be added. In this disclosure, since the weather resistance is improved by structural ingenuity, these weather resistant agents may not be added.

[Thickness of coating film]
When the film thickness of the epoxy coating film is thick, the sacrificial anodic action acts for a long period of time because the abundance of metal particles in the coating film is large, and the permeation of oxygen, water, etc. in the coating film is effectively suppressed. It has the advantage of improving the ability to block from the surrounding environment. On the other hand, if the film thickness of the epoxy-based coating film is thick, stress load is applied to the inside of the coating film and the contact surface with the aluminum material due to thermal expansion due to the operation of the heat exchanger, etc. There is a risk of peeling and significantly impairing the effect of improving the corrosion resistance of the heat exchanger. Further, when a minute space is provided in the header portion of the heat exchanger for the purpose of heat insulation between fluids having different temperatures, if the film thickness of the epoxy-based coating film is thick, the minute space is filled with the coating film. Therefore, there is a risk that the performance as a heat exchanger will be significantly reduced. In addition, the cost increases as the amount of paint used increases.

When the film thickness of the epoxy-based coating film is thin, the above-mentioned drawbacks are eliminated, but the sacrificial anode action acts only for a short period of time because the abundance of metal particles in the coating film is small. Further, it is not possible to effectively suppress the permeation of oxygen, water and the like through the coating film, and the coating film is peeled off due to corrosion under the coating film. Therefore, the effect of improving the corrosion resistance of the heat exchanger cannot be sufficiently obtained.

As a result of the examination by the inventors, as described later, when the thickness of the coating film is 10 μm to 50 μm, it exhibits a sufficient environmental blocking effect against oxygen, water, etc., a sacrificial anode action, and an early coating. It was clarified that the film peeling can be suppressed. Therefore, the corrosion resistance of the heat exchanger can be effectively improved.

The corrosion resistance test, moisture resistance test and adhesion test in Examples and Comparative Examples described later were carried out as shown below.

[Corrosion resistance test]
The corrosion resistance of the coating film of the heat exchanger was evaluated based on the SWAAT test (Sea Water Acidified Test) defined by ASTM G85-A3.

[Moisture resistance test]
The moisture resistance of the coating film of the heat exchanger was evaluated by holding the sample in a constant temperature and humidity layer set at an ambient temperature of 40 ° C. and a relative humidity of 98%.

[Adhesion test]
The adhesion of the coating film after the durability test was evaluated based on the 100-square grid test defined by JIS K5400.

(Comparative Example 1)
As the coating film according to Comparative Example 1, an epichlorohydrin / bisphenol A type coating film containing zinc powder was arranged on a brazing sheet with a film thickness of 80 μm.

The above-mentioned corrosion resistance test and subsequent adhesion test were carried out on the coating film. As a result, as shown in the cross-sectional photograph of FIG. 6A, with respect to the corrosion resistance, there was almost no progress of corrosion on the brazing sheet, and the sacrificial anticorrosion function by the zinc powder was recognized. On the other hand, as for the adhesiveness, remarkable peeling of the coating film was confirmed as shown in FIG. 7A.

The above-mentioned moisture resistance test and subsequent adhesion test were carried out on the coating film. As a result, as shown in FIG. 8A, remarkable peeling of the coating film was confirmed.

(Comparative Example 2)
As the coating film according to Comparative Example 2, an epichlorohydrin / bisphenol A type coating film containing zinc powder was arranged on a brazing sheet with a film thickness of 5 μm.

The above-mentioned corrosion resistance test and subsequent adhesion test were carried out on the coating film. As a result, as shown in the cross-sectional photograph of FIG. 6B, as for the corrosion resistance, the progress of corrosion to the brazing sheet under the coating film was observed. As for the subsequent adhesion, remarkable peeling was confirmed as shown in FIG. 7B.

The above-mentioned moisture resistance test and subsequent adhesion test were carried out on the coating film. As a result, as shown in FIG. 8B, no peeling of the coating film was confirmed.

(Example 1)
As the coating film according to Example 1, an epichlorohydrin / bisphenol A type coating film containing zinc powder was arranged on a brazing sheet with a film thickness of 40 μm.

The above-mentioned corrosion resistance test and subsequent adhesion test were carried out on the coating film. As a result, as shown in the cross-sectional photograph of FIG. 6C, with respect to the corrosion resistance, the progress of corrosion to the brazing sheet was not observed, and the sacrificial anticorrosion function by the zinc powder was observed. As for the subsequent adhesion, no peeling was confirmed as shown in FIG. 7C.

The above-mentioned moisture resistance test and subsequent adhesion test were carried out on the coating film. As a result, as shown in FIG. 8C, no peeling of the coating film was confirmed.

(Example 2)
As the coating film according to Example 2, an epichlorohydrin / bisphenol A type coating film containing zinc powder was arranged in a fillet portion of a heat exchanger composed of a brazing sheet with a film thickness of 40 μm.

The above-mentioned corrosion resistance test was carried out on the coating film. As a result, as shown in the cross-sectional photograph of FIG. 6D, it was confirmed that the preferential corrosion of the header portion was effectively suppressed in terms of corrosion resistance.

(Comparison between Examples and Comparative Examples)
As is clear from the comparison of FIGS. 6A to 6D and 7A, 7B, and 7C, if the coating film is sufficiently thick (Example and Comparative Example 1), the sacrificial anticorrosion function effectively and the coating film is coated. Corrosion does not occur under the coating film, but if the thickness of the coating film is sufficiently thin (Comparative Example 2), corrosion under the coating film occurs due to insufficient blocking of water, oxygen, and the like.

Further, as is clear from the comparison of FIGS. 8A, 8B and 8C, if the thickness of the coating film is sufficiently thick (Comparative Example 1), stress is generated inside the coating film and at the interface between the coating film and the substrate. As a result, the coating film is easily peeled off. However, if the thickness of the coating film is sufficiently thin (Example and Comparative Example 2), the adhesion of the coating film is ensured.

In FIG. 9, the adhesion of Example 1 and Comparative Example is plotted with the horizontal axis representing the thickness of the coating film and the vertical axis representing the adhesion. Regarding the adhesion on the vertical axis, the number of remaining coating films in the above-mentioned 100-square grid test is defined as the adhesion and plotted. As shown in FIG. 9, it can be seen that the thickness of the coating film (epoxy film) in the range of 10 to 50 μm is the most suitable condition for ensuring the corrosion resistance of the coating film.

It should be noted that the present disclosure is not limited to the description of the above-described embodiment, and various changes can be made within the scope of the claims, and the disclosure is disclosed in different embodiments or a plurality of modifications. Embodiments obtained by appropriately combining technical means are also included in the technical scope of the present disclosure.

The present disclosure can be widely and suitably used in the field of aluminum heat exchangers for air conditioners and the like.

10 Brazing sheet 10a Joint surface 10b Non-bonded adjacent surface 11 Core material 12 Wax layer 13 Sacrificial anode material layer 14 Epoxy coating film 20 Brazing sheet joint structure 21 Joint 22 Fillet 30 Plate fin laminate 31 End plate 32 Plate fin 33 Header opening 40 Parallel flow capacitor (PFC)
41 Header pipe 42 Flat pipe 43 Corrugated fin 51 Heat exchanger 52 Epoxy coating film installation part 53 Blower fan 54 Air filter 55 Drainage receiver

Claims

It ’s an aluminum heat exchanger.
A part of the surface of the heat exchanger has a layer of epoxy-based coating having a thickness in the range of 10 to 50 μm.
The heat exchanger is arranged inside the box so that the coating film is not directly irradiated with ultraviolet rays.
Heat exchanger.
The coating film contains a metal powder having a lower potential than aluminum.
The heat exchanger according to claim 1.
The coating film contains zinc powder.
The heat exchanger according to claim 1.
The coating film is arranged in a non-ventilated portion inside the box.
The heat exchanger according to any one of claims 1 to 3.
The coating film is arranged so that products associated with deterioration of the coating film are removed by dew condensation water generated during the operation of the heat exchanger.
The heat exchanger according to any one of claims 1 to 4.
The heat exchanger is configured using a brazing sheet.
The brazing sheet is
Aluminum alloy core material and
A sacrificial anode material layer made of an aluminum alloy sacrificial anode material coated on one or both sides of the core material and containing zinc (Zn) and silicon (Si).
To prepare
The heat exchanger according to any one of claims 1 to 5.
The heat exchanger has a joint that includes the sacrificial anode layer.
The coating film is applied to the joint portion,
The heat exchanger according to claim 6.
The heat exchanger is configured by using an aluminum tube made of an aluminum alloy.
The aluminum tube is provided with a sacrificial anode material layer made of a sacrificial anode material made of an aluminum alloy containing zinc (Zn) or zinc (Zn) and silicon (Si) on the surface of the aluminum tube.
The heat exchanger according to any one of claims 1 to 5.
The heat exchanger is configured using a brazing sheet.
The brazing sheet is
Aluminum alloy core material and
A sacrificial anode material layer comprising a sacrificial anode material made of an aluminum alloy coated on one or both sides of the core material and containing zinc (Zn) or zinc (Zn) and silicon (Si).
The heat exchanger according to any one of claims 1 to 8.
The heat exchanger has a joint that includes the sacrificial anode layer.
The coating film is applied to the joint portion,
The heat exchanger according to claim 8 or 9.
An air conditioner including the heat exchanger according to any one of claims 1 to 10.
It is equipped with a drainage receiver that receives the condensed water generated from the heat exchanger.
The coating film was provided vertically above the drainage receiver.
Air conditioner.