JP2002256446A - Functional copper base-material and heat exchanger tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a coating which greatly improves wettability of the surface of a copper base-material and has durability, and to provide a manufacturing method therefor. SOLUTION: A method includes forming a layer 101 having a structure with submicron size of fine unevenness on the surface of the copper base-material 100, by forming copper oxide on the surface by immersing the copper base- material 100 in an alkaline aqueous solution of high temperature, or by immersing the copper base-material in an electroless copper plating bath. The method, subsequently, reacts the surface of the layer 101 having the structure with fine unevenness with a thiol compound having a function group such as a hydrophilic group or a hydrophobic group at the end group, and forms a coating consisting of a sulfur compound layer 102 on the surface of the layer 101 having a structure with fine unevenness.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a surface treatment for imparting functionality to a copper base material surface.

[0002]

2. Description of the Related Art Copper base materials have poor wettability with water, and have a contact angle with water of about 80 degrees. In a copper heat transfer tube of an evaporator used in an absorption refrigerator, a heat source water is caused to flow inside the heat transfer tube, and a liquid refrigerant (water) is dropped and sprayed from the upper portion along the outer periphery of the heat transfer tube to evaporate. In order to improve the performance of the heat transfer tube, it is necessary that the entire surface of the heat transfer tube is covered with the liquid refrigerant, that is, wet with the liquid refrigerant so that the liquid refrigerant is evaporated on the entire surface of the heat transfer tube. However, as described above, since the copper surface has poor wettability, the entire surface of the heat transfer tube is not wet, and dryout is likely to occur. If the entire surface of the heat transfer tube is not wet, the evaporation area is reduced and the performance is reduced. Therefore, the performance is improved by improving the wettability of the heat transfer tube surface with water. In order to improve the wettability, various methods have been proposed.

In Japanese Patent Application Laid-Open No. Hei 11-213376, a method of forming a copper oxide film by immersing a copper heat transfer tube in a high-temperature alkaline solution is disclosed. In Japanese Patent Application Laid-Open No. 10-253195, a heat treatment is performed after blasting. Japanese Patent Application Laid-Open No. 6-82126 discloses a method for forming an oxide film by corona discharge.
No. 981 proposes a method of coating the surface of a heat transfer tube with fine gauze gauze to improve wettability by utilizing a capillary phenomenon.

In an air conditioner such as a package air conditioner or a room air conditioner, as a refrigerant pipe connecting the indoor unit and the outdoor unit, a pipe (generally referred to as a gas pipe) through which the refrigerant gasifies and a gas or liquid pipe are provided. Two pipes of two phases or pipes through which liquid flows (generally called liquid pipes) are arranged. Among them, the pipe from the outlet of the evaporator to the inlet of the compressor, the so-called gas pipe, has a larger pipe diameter than the liquid pipe so as not to increase the pressure loss in the pipe. These pipes are copper smooth pipes.

As another method for improving the surface functionality of a copper base material, there has been reported a method of forming a functional film by chemically reacting a thiol compound having a functional group on a copper surface. For example, JP-A-11-274602 discloses an optical semiconductor device that forms a self-assembled film having a functional group such as a hydroxyl group, an amino group, a carboxyl group, a carbonyl group, or an aldehyde group on the surface of a copper electrode. . That is, a molecule having a thiol group chemically adsorbs to gold, silver, copper, etc., and introduces various functions to a solid surface of gold, silver, copper, etc. by introducing a functional functional group on the side opposite to the thiol group. be able to.

[0006]

It is conventionally known that when a thiol compound having a hydrophilic functional group is reacted with a gold surface, a surface having extremely high hydrophilicity can be formed. Journal of the American Chemical Society. Vol.
111 (No. 1) p325 (1989)), by reacting a thiol compound having a functional group of a hydrophilic group such as a hydroxyl group or a carboxyl group on the gold surface, the contact angle of the gold surface becomes 10 degrees or less, It is reported to exhibit hydrophilicity. It has been reported that this treatment is also effective for the copper substrate surface. However, application of thiol compounds is more difficult than gold, because copper surfaces tend to form oxides. Actually, one of the thiol compounds, H,
Using a solution of S (CH ₂ ) ₁₀ CH ₂ OH in ethanol and reacting it with gold and copper substrates and measuring the contact angle by the water drop method, the contact angle of the copper reacted with the thiol compound was 31 °. As shown, the wettability was poor compared to the low contact angle of 5 degrees of gold reacted with the thiol compound, and it was found that the wettability of the copper surface was insufficient.

As a method for improving the wettability of the surface of a copper substrate, Japanese Patent Laid-Open No. 2000-2000 discloses a heat transfer tube for an evaporator of an absorption refrigerator.
Japanese Patent No. 220981 discloses a method of coating the heat transfer tube surface with a gauze having a fine lattice shape to improve the wetting by utilizing the capillary phenomenon. However, this method has problems with the adhesion of the gauze to the heat transfer tube, the durability thereof, the life of the gauze, and the like.

[0008] In the method of hydrophilization treatment by corona discharge described in JP-A-6-82126, -C =
Although an oxide film having a hydrophilic group of O (ketone group) is formed to improve the hydrophilicity, an apparatus for forming the oxide film becomes large-scale, which affects the manufacturing cost. In addition, there is no durability in attaching ketone groups, and the reliability of hydrophilicity is low.

[0009] The copper oxide coating described in Japanese Patent Application Laid-Open No. 11-213376 has a problem that sufficient hydrophilicity of the surface cannot be achieved particularly at the initial stage.

[0010] JP-A-10-253195 describes,
In the method of forming a copper oxide by performing a heat treatment after the blast treatment, there is a problem that the copper base material is softened by the heat treatment and the material strength is reduced.

Refrigerating machine oil is added to the refrigerant applied to the air conditioner. As this refrigerating machine oil, one having a compatibilizing action with the refrigerant is generally used. When the refrigerant is in the liquid phase in the pipe, the refrigerating machine oil flows together with the refrigerant,
The pressure loss in the pipe is low. However, when the refrigerant is in a gaseous state, a phenomenon occurs in which the refrigerating machine oil separates and adheres to the pipe wall, and the pressure loss in the pipe increases. In addition, since the amount of refrigerating machine oil returning to the compressor due to adhesion to the pipe wall decreases, the risk of poor lubrication increases as it is. Therefore, the amount of refrigerating machine oil to be added is increased in consideration of safety. An increase in the amount of refrigerating machine oil causes a decrease in compressor efficiency, a decrease in cycle efficiency, and the like. However, efficiency is sacrificed to some extent in order to avoid poor lubrication. In order not to increase the amount of refrigerating machine oil to be added, it is necessary to make the surface such that the refrigerating machine oil does not easily adhere to the pipe wall.

An object of the present invention is to provide a copper substrate having a highly functional coating such as a durable superhydrophilic coating or superhydrophobic coating on the surface and a method for producing the same.

[0013]

As described above, one of the thiol compounds, HS (CH ₂ ) ₁₀ CH ₂ OH, is used.
When the wettability was improved by reacting with a copper substrate using the ethanol solution of No. 4, satisfactory wettability was not obtained.
The inventors focused on the surface shape of the copper substrate to be reacted with the thiol compound, and as a result of conducting tests by changing the roughness of the surface shape variously, a fine uneven structure was formed on the surface of the copper substrate, It has been found that a functional group such as a hydrophilic group or a hydrophobic group of the thiol compound acts effectively by reacting the thiol compound with the fine uneven structure to form a film by a thiolate bond. It has been found that the fine uneven structure is preferably formed by a plating method or a chemical conversion method.

[0014] That is, the above problem is to provide a layer having a fine uneven structure on the surface of a copper base material, and further provide a layer of the fine uneven structure with a thiol compound having a functional group such as a hydrophilic group or a hydrophobic group at a terminal group. It can be achieved by reacting to form a thiolate bond. The fine concavo-convex structure is a fine concavo-convex structure in which the distance between the peaks of the convex portions of the surface unevenness is on the order of microns or submicrons.

A method for forming a layer having a fine uneven structure on the surface of a copper substrate will be described. Typical methods include (1) a method of forming copper oxide, and (2) a method of performing copper plating.

In the method (1) for forming copper oxide, a copper base material is immersed in a high-temperature aqueous alkali solution,
Copper oxide is formed on a copper base material surface (chemical conversion treatment method). The formed copper oxide has a whisker-like crystal morphology with a submicron size, as shown in FIG. 2 (a photograph observed with a scanning electron microscope (SEM)). Note that, even when copper oxide is reduced to metallic copper, the whisker-like crystal form does not change, so that it can be used similarly. In the copper plating of (2), a palladium catalyst is applied to the surface of the copper substrate, and the copper substrate is immersed in an electroless copper plating bath mixed with a reducing agent to precipitate Cu-Ni-P and form a fine uneven structure. can do. As shown in FIG. 3 (SEM image of plating surface), the formed plating surface has a needle-like shape having a submicron size. Instead of electroless copper plating, normal electroplating may be used.

These methods are generally used for the roughening treatment of a copper foil performed for bonding an inner layer copper foil of a multilayer printed wiring board and an insulating resin. The fine concavo-convex structure can also be formed by an etching method as another chemical conversion treatment.

The molecule of the thiol compound has a hydrophilic group such as a hydroxyl group, a carboxy group, an amino group, a CF ₃ group,
In linear structure having a functional group having a hydrophobic group of H ₃ group, the adhesion strength of the film for Cu or Cu alloy and a sulfur atom of the thiol compound in the molecule of the copper base is chemically bonded is high, durability There is. In addition, since this coating is a monomolecular film and is oriented so that the functional group (having a hydrophilic group or a hydrophobic group) of the terminal group of the thiol compound becomes the outermost surface, the coating has hydrophilicity, hydrophobicity, or water repellency. Present. Further, since a submicron fine uneven structure is formed on the surface of the copper base material, the hydrophilicity becomes more hydrophilic and shows superhydrophilicity, and the hydrophobicity becomes more hydrophobic and shows superhydrophobicity. Although hydrophilicity and water repellency are expressed using a contact angle, here, conceptually, when the contact angle is 10 degrees or less, super hydrophilicity, 15
The case where the temperature is 0 degrees or more is defined as super water repellency.

FIG. 1 is a schematic diagram showing an example of the structure of a film on the surface of a copper base material according to the present invention, in the case where the functional group of the terminal group has a hydroxyl group. In the illustrated example, a fine uneven structure layer 101 is provided on a copper base material 100, and a thiol compound having a hydroxyl group (hydrophilic group) at a terminal group is reacted on the surface thereof to form a sulfur compound layer 102. . The coating having such a structure is used for a heat exchanger configured to exchange heat between a heat exchange medium flowing in the heat transfer tube and a heat exchange medium dropped on the outer surface of the heat transfer tube. By forming the heat pipe on the outer surface of the heat transfer tube of an evaporator of an absorption refrigerator, for example, the performance can be improved.

In the case of an evaporator of an absorption refrigerator, a fine concavo-convex structure layer is provided on the outer surface of the heat transfer tube constituting the evaporator by a plating method or a chemical conversion treatment, and the heat transfer tube on which the fine concavo-convex structure layer is formed is functionally applied. A hydrophilic film is formed by immersing in a thiol compound solution having a group and reacting the thiol compound having a hydrophilic group on the surface of the fine uneven structure layer. Thus, the water (refrigerant) dropped on the outer surface of the heat transfer tube widely spreads on the outer surface of the heat transfer tube, and the heat transfer performance can be improved by improving the wettability.

The above-mentioned piping for an air conditioner (gas pipe, liquid pipe)
In the case of (1), a fine uneven structure layer is formed on the inner surface of the pipe, and a thiol compound having a hydrophobic group is reacted with the fine uneven structure layer to form a water-repellent coating. This water-repellent coating can prevent oil in the refrigerant from adhering to the inner surface of the pipe, and can reduce pressure loss in the pipe. Further, since the amount of oil adhering to the inner surface of the pipe is reduced, the amount of refrigerating machine oil added can be reduced, and the compressor performance efficiency and cycle performance efficiency are improved.

[0022]

FIG. 1 is a block diagram showing an embodiment of the present invention.
This will be described with reference to FIGS.

First Embodiment First, a coating having a fine concavo-convex structure having a needle shape is formed on the surface of a copper substrate.
Here, a film having a fine uneven structure was formed by the following procedure by an interplate process of Ebara Ujilite Co., Ltd., which is one of the electroless copper plating methods. After subjecting the copper substrate to alkaline degreasing and pre-etching treatment, a palladium catalyst is deposited on the surface of the copper substrate, and the solution is placed in a plating solution bath containing copper sulfate, nickel sulfate, and sodium hypophosphite at a temperature of 70 ° C.
After immersion for about 1 minute, an acicular electroless copper plating film having a thickness of about 1 μm was formed.

Then, a solution was prepared by dissolving a thiol compound of 11-mercaptoundecanol OH (CH ₂ ) ₁₁ SH in an ethanol solution of a solvent such that the concentration became 1 mM (mmol). Was immersed at room temperature for 24 hours. After immersion for 24 hours, the copper substrate was taken out, washed with an ethanol solution, and air-dried.

Next, the wettability of this sample with water was 0.5 μl
(Microliters) of water droplets were dropped, and the contact angle with water at that time was measured and evaluated. As a result, the contact angle was extremely high, being 5 degrees.

As described above, the fine uneven structure layer is provided on the surface of the copper base material where it is difficult to improve the wettability, and a thiol compound having a functional group at the terminal is reacted with the fine uneven structure layer to form a coating film. Thereby, it is possible to improve the wettability and to maintain the improvement in the wettability over a long period of time.

Further, a film was formed in the same manner using 1-dodecanethiol CH ₃ (CH ₂ ) ₁₁ SH instead of 11-mercaptoundecanol as a thiol compound, and the contact angle was measured. It showed super water repellency.

In the above embodiment, the fine uneven structure layer is provided on the surface of the copper substrate by electroless copper plating. However, the fine uneven structure layer may be formed by ordinary electroplating, not by electroless copper plating. Is also possible.

By using the heat transfer tube to which this embodiment is applied, the performance of the evaporator can be improved, and the evaporator and the absorption refrigerator can be reduced in size and cost.

Next, an example in which the present invention is applied to piping of an air conditioner will be described. FIG. 4 shows a cycle configuration of the air conditioner. The illustrated air conditioner includes an outdoor unit 416 and a plurality of indoor units 41 connected to the outdoor unit 416 in parallel with each other.
7, 418.

The outdoor unit 416 includes a compressor 401, a four-way valve 402 having an A port connected to the discharge side of the compressor 401 and a C port connected to the suction side, and an outdoor heat source having one end connected to the B port of the four-way valve 402. Exchanger 403, high-pressure vessel (gas-liquid separation receiver) 404 having one end connected to the other end of outdoor heat exchanger 403, and high-pressure vessel (gas-liquid separation receiver) 4
04 and a four-way valve 402
And a blocking valve 410 connected to the D port. The high-pressure container 404 has a function as a gas-liquid separator and a function as a liquid receiver.

The indoor unit 417 includes an indoor heat exchanger 407,
Decompression device 405 having one end connected to indoor heat exchanger 407
The indoor unit 418 includes the indoor heat exchanger 40
8 and a decompression device 406 having one end connected to the indoor heat exchanger 408. Decompression devices 405, 40
6 The other end is connected to the blocking valve 409 via a connection pipe 414, and the ends of the indoor heat exchangers 407 and 408 on the side opposite to the pressure reducing device are connected to the blocking valve 410 via a connection pipe 415, respectively. Have been.

In the apparatus having the above configuration, the refrigerant flows during the cooling operation in the direction indicated by the solid arrow in the figure. In the figure, the position of the four-way valve 402 is at the time of the cooling operation. On the other hand, during the heating operation, the operation position of the four-way valve 402 is switched, and the refrigerant flows in the direction of the dashed arrow.

The refrigerant used is not only Freon R22 but also HFC-based refrigerants, for example, R407C, R410A, R3
2, a refrigerant such as R134a, R404A, etc.
C-based refrigerants and natural-based refrigerants such as propane, isobutane,
It is also used for refrigerants such as carbon dioxide and ammonia.

The connection pipe 415 for the air conditioner has an outer diameter of 15.
A 9 mm oxygen-free copper tube was used. The inner surface of the oxygen-free copper tube was subjected to electroless copper plating, and then immersed in a 1 mM concentration 1-dodecanethiol / ethanol solution to form a coating.
Electroless copper plating, according to the above method, degreasing, etching,
For treatments such as catalyst application and plating, each solution was supplied into a pipe using a chemical pump. The plating thickness is about 1 μm. When the formed film was observed by SEM, a needle-like crystal form was observed. A 1 mM concentration of 1-dodecanethiol / ethanol solution was used as a thiol compound, and this solution was filled in a tube after plating and left as it was for 24 hours to form a film. Next, the 1-dodecanethiol / ethanol solution was discharged, the inner surface of the tube was washed with an ethanol solution, and air dried.

The refrigerating machine oil currently used as a refrigerant for an air conditioner differs depending on the type of the refrigerant, but is mainly an alkylbenzene type, ether oil, ester oil or the like. The wettability of the copper tube after the formation of the film with respect to the refrigerator oil was examined. Since it is difficult to measure the contact angle of the inner surface of the tube, the same treatment was performed using a copper plate material and examined. The contact angle with respect to various types of refrigerator oil showed a value of around 165 degrees, and it was confirmed that the film had high oil repellency.

In place of 1-dodecanethiol, H
The same treatment was performed using a thiol compound of S (CH ₂ ) ₂ (CF ₂ ) ₅ CF ₃ . The contact angle with various refrigerator oils is around 168 degrees, and 1-dodecanethiol.
As in the case of using the ethanol solution, high oil repellency was exhibited.

By using a pipe exhibiting such high oil repellency, adhesion of refrigeration oil to the pipe is reduced. Therefore, the amount of refrigerating machine oil added to the refrigerant can be reduced, the pressure loss in the piping can be reduced, and the compressor and cycle efficiency can be improved. (Second Embodiment) After oxygen-free copper base material is subjected to alkaline degreasing treatment, 95%
Ebonol C Special (Japan Metal
(Finishing Co. Ltd. solution) for 5 minutes, then taken out, washed with water and dried. Subsequently, a solution was prepared by dissolving a thiol compound of 11-mercaptoundecanol OH (CH ₂ ) ₁₁ SH in an ethanol solution of a solvent so as to have a concentration of 1 mM, and the copper substrate was placed in the solution at room temperature. Soaked for 24 hours. Thereafter, the surface of the copper substrate was washed with an ethanol solution and dried in the air to form a film. When the contact angle of this coating with water was measured, it was 5 degrees or less, indicating super hydrophilicity.

The durability of the obtained coating film was measured by immersing it in running water (5 ml / s) of deionized water for 30 days and then measuring the contact angle. It was confirmed that the coating was high.

Next, using a smoothed pipe made of phosphorus-deoxidized copper having an outer diameter of 15.9 mm and a wall thickness of 0.6 mm as a heat transfer tube, the outer surface of the heat transfer tube is subjected to a hydrophilization treatment under the same conditions as those described above. Was. The surface was black and had a whisker crystal morphology of submicron when observed by SEM. Further, when the water droplet was dropped on the outer surface of the heat transfer tube, the water droplet spread over the entire outer periphery and showed high hydrophilicity. The measured contact angle was 5 degrees or less.

It is to be noted that a film forming process using the thiolate compound is also possible on a surface on which the outer surface of the heat transfer tube is formed with irregularities by rolling, machining, or the like.

According to the present embodiment, the wettability of the outer surface of the heat transfer tube is improved, and the performance of the evaporator and the absorption refrigerator can be improved and the size can be reduced.

In each of the above embodiments, the fine uneven structure is formed by the plating method or the chemical conversion method. However, the fine uneven structure of the micron order or the submicron order is formed on the surface (inside) of the pipe regardless of these methods. (Surface).

[0044]

According to the present invention, it has become possible to form a highly functional coating such as a durable superhydrophilic coating, superhydrophobic coating or oil-repellent coating on the surface of a copper substrate.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a coating structure showing the principle of the present invention.

FIG. 2 shows a copper oxide surface on a copper substrate according to an embodiment of the present invention.
It is a figure which shows the photograph observed by SEM.

FIG. 3 shows a plating surface on a copper base material according to an embodiment of the present invention.
It is a figure which shows the photograph observed by SEM.

FIG. 4 is a system diagram showing a configuration example of an air conditioner to which the present invention is applied.

[Explanation of symbols]

 REFERENCE SIGNS LIST 100 Copper base material 101 Fine uneven structure layer 102 Sulfur compound layer 401 Compressor 402 Four-way valve 403 Outdoor heat exchanger 404 High-pressure vessel 405, 406 Pressure reducing device 407, 408 Indoor heat exchanger 409, 410 Restriction valve 414, 415 Connection pipe 416 Outdoor units 417, 418 Indoor units

Continued on the front page (72) Inventor Tomomi Umeda 502 Kandate-cho, Tsuchiura-shi, Ibaraki F-term in Machine Research Laboratory, Hitachi Ltd. 4K022 AA02 AA33 BA08 BA31 CA03 CA04 CA06 DA01 EA02 4K026 AA06 AA11 AA25 BA01 BB10 CA39 DA03 DA11

Claims (5)

[Claims] 1. A fine uneven structure formed on the surface of a copper base material, and a compound layer formed on the surface of the fine uneven structure via a thiolate bond and having a functional group on the outermost surface. Functional copper substrate. 2. A fine uneven structure layer formed on the inner surface by a plating method or a chemical conversion treatment method, and further bonded to the surface of the fine uneven structure layer via a thiolate group.
A coating in which functional groups of F ₃ or CH ₃ are oriented,
An air conditioner pipe composed of a copper pipe having: 3. A fine uneven structure layer formed on an outer surface and bonded to the surface of the fine uneven structure layer via a thiolate group,
A heat transfer tube formed of a copper tube having, on the outermost surface, a coating in which a hydrophilic functional group is oriented. 4. A plating method or a chemical treatment on the inner surface of the copper tube.
Procedure for forming a fine uneven structure layer by the method
CF is added to the copper tube on which the fine uneven structure layer is formed. ₃Group
Is CH₃Filled with a thiol compound solution having a functional group
And bringing the thiol compound solution into contact with its inner surface
Discharging the thiol compound solution in the copper tube,
Cleaning the inside with a solvent and drying it.
And the inner surface of the copper tube is provided with a thiolate group.
And CF on the outermost surface₃Group or CH₃Orient functional group
Surface treatment of copper tubes characterized by forming a coated film
Method. 5. A procedure for forming a fine concavo-convex structure layer on the outer surface of a copper tube by a plating method or a chemical conversion treatment method, and a method for forming the fine concavo-convex structure layer on the outer surface of the copper tube having a hydrophilic functional group. A procedure of immersing in a thiol compound solution, and a procedure of washing and drying the immersed copper tube with a solvent, and then drying the outer surface of the copper tube with a thiolate group on the outermost surface. A method for treating a surface of a copper tube, comprising forming a film in which the functional groups are oriented.