JP4306504B2 - Metal substrate and heat exchanger using the same - Google Patents

Description

  The present invention relates to a metal base material having a film containing polyaniline formed on the surface, and a heat exchanger in which a heat exchanging portion is formed using the metal base material. For example, an evaporator such as a car air conditioner or an air conditioner Thus, it is suitable for use in a heat exchanger or the like that requires a function of deodorizing odorous substances and a function of sterilizing harmful microorganisms.

  In general, a film material for preventing adhesion of substances that become components of odor and dirt is used for a film of a heat exchanger. However, a substance having a functional group and a high polarity is likely to adhere to a metal substrate having a complicated surface shape such as a tube or a fin forming the heat exchange part, and it is difficult to prevent the substance once it starts to adhere. Therefore, a function capable of decomposing a substance attached from the initial state is necessary.

  In patent document 1, the antifouling method of the heat exchanger using polyaniline is proposed. This is to provide a film made of polyaniline on the heat exchanger or heat exchange part, and activate the oxygen in the condensed water using the condensed water adhering to the heat exchange, thereby decomposing the organic substance. .

There are various forms of the above polyaniline. When the relationship between the form of polyaniline and the amount of active oxygen generated is examined, according to Patent Document 2, a doped type (non-doped polyaniline / polyaniline derivative ( A polyaniline / polyaniline derivative (having a dopant attached by electrostatic interaction) is superior in generating active oxygen. Further, Patent Document 3 describes that this dopant includes, for example, a protonic acid and a Lewis acid.
JP 2002-71296 A Japanese Patent Laid-Open No. 2003-200532 JP 2001-70426 A

  However, when active oxygen is generated by attaching condensed water to a metal substrate on which a polyaniline containing the above dopant (for example, proton acid or Lewis acid) is formed, rust due to corrosion of the metal substrate occurs. This is a corrosive action by the dopant, which leads to a problem of durability of the metal substrate itself.

  Therefore, in order to provide an anticorrosive effect, it is possible to generate active oxygen in the same manner as described above using a metal base material (Patent No. 3129838) on which a so-called undoped polyaniline containing no dopant is formed. Further, the active oxygen generation ability is remarkably lowered as compared with the dope type, and a sufficient deodorizing ability cannot be obtained.

  In addition, polyaniline using a protonic acid or a Lewis acid as a dopant has a problem that the ability to generate active oxygen does not last for a long time. This is because the polyaniline turns into an undoped type by flowing out into the condensed water because the molecular weight of the protonic acid or Lewis acid is small.

  In view of the above problems, an object of the present invention is to provide a metal base material having a polyaniline film as a film without corrosion of the metal base material while maintaining a deodorizing / sterilizing function for a long time, and a heat exchanger using the same. And

  In order to achieve the above object, the present invention employs the following technical means.

In the invention according to claim 1, in the metal substrate (13, 14) provided with a film on the surface, the film is formed with the first film (51) formed on the metal substrate (13, 14), A second film (52) formed on the first film (51), the first film (51) being an undoped polyaniline film made of undoped polyaniline and / or a derivative thereof; The second film (52) is a doped polyaniline film made of polyaniline and / or its derivative containing an organic acid as a dopant and having a doping rate in the range of 10 to 30% . The organic acid is acid phosphoxymethacrylate. It is characterized by being.

  Thereby, the undoped polyaniline film as the first film (51) protects the metal base (13, 14), and the doped polyaniline film as the second film (52) can generate active oxygen. Therefore, it can provide as a metal base material (13, 14) which has rust prevention and the active oxygen generation | occurrence | production function.

  Further, since both the first film (51) and the second film (52) are made of polyaniline or a polyaniline derivative, the adhesion between the first film (51) and the second film (52). Excellent in properties.

Further, by using an organic acid as a dopant imparted to the second film (52), the organic acid itself has a structure involving the polyaniline or the polyaniline derivative, so that the organic acid itself does not flow out into the condensed water. . Therefore, the doped polyaniline used in the second film (52) is always kept in a doped state, can generate stable active oxygen, and can have a long life.
In order for the second film (52) to generate sufficient active oxygen, it is preferable that the doping rate of the polyaniline with the organic acid is 10 to 30%.
Here, the doping rate is obtained by dividing the number of functional groups (for example, phosphonic acid groups) in the organic acid contributing as a dopant by the number of positions where polyaniline can be doped. The dopant is doped into the polyaniline by approaching the nitrogen in the polyaniline by Coulomb force, but it is doped into one of the two nitrogens rather than all the nitrogen. Therefore, the maximum doping rate is 50%. However, the active oxygen generation capacity of the doped polyaniline does not increase linearly with respect to the doping rate, but rapidly decreases at a certain doping rate. This is because when the doping rate is increased, the organic acid in the doped polyaniline hinders the mobility of electrons, and as a result, active oxygen is hardly generated. Therefore, the organic acid can be used without waste by optimally controlling the doping rate.

  The specific type of polyaniline is the same as that of the invention described in claim 2, in which the first film (51) is formed from an undoped polyaniline or a polyaniline derivative represented by the chemical formula (Chemical Formula 1 or Chemical Formula 2). Can be used. Further, the second film (52) is formed from a doped polyaniline or a polyaniline derivative in which the functional group in the organic acid represented by the chemical formula (Chemical Formula 3 or Chemical Formula 4) is ionized, and as a result, the anion is doped. Can be used.

Furthermore, the invention described in claim 3 is characterized in that the organic acid used in the second film (52) has a molecular weight of 100 or more. Thereby, it can prevent that the organic acid in the polyaniline which forms the 2nd membrane | film | coat (52) flows out into water.

The metal base (13, 14) can be made of a metal (aluminum alloy) containing aluminum, as in the fourth aspect of the invention. Aluminum alloys have the advantages of being light, easy to process, and low in cost, and more suitable as a metal substrate.

In invention of Claim 5 , in the heat exchanger which has a heat exchange part (12) with which a heat exchange fluid distribute | circulates inside, a heat exchange part (12) is in any one of Claims 1-4. It was formed from the metal base material (13, 14).

Thereby, the heat exchanger (10) provided with the effect of Claims 1-4 can be provided.

The heat exchanger (10) can be applied to a refrigerant that circulates in the refrigeration cycle as a heat exchange fluid as in the invention described in claim 6 , and further, as in the invention described in claim 7. It is suitable for use in an evaporator (10) for evaporating the refrigerant.

And as invention of Claim 8 , as a refrigerating cycle, the thing for motor vehicles is suitable.

  Incidentally, the reference numerals in parentheses of each means described above are an example showing the correspondence with the specific means described in the embodiments described later.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments shown in the drawings will be described below. FIG. 1 shows a temperature control device 1 having a heat exchanger 10 according to an embodiment of the present invention. The temperature control device 1 is applied to an air conditioner for an automobile.

  The temperature control device 1 includes a case 5, a heat exchanger 10 provided therein, a heater 20, an air suction device 30, and an air outlet 40. The heat exchanger 10 is a tube 13 formed by molding an aluminum material and heat radiating fins 14 and is brazed, and is, for example, a laminated drone cup type heat exchanger. This heat exchanger 10 is arranged in a refrigeration cycle, and is configured as an evaporator in which a refrigerant such as alternative chlorofluorocarbon (corresponding to the heat exchange fluid in the present invention) circulates in the tube 13.

  The air introduced from the air suction device 30 into the case 5 is cooled by the heat exchanger 10 and warmed by the heater 20. Then, the cold air and the warm air are appropriately mixed and blown out from the air outlet 40 and sent to the vehicle interior.

  FIG. 2 shows the heat exchanger 10 in detail, and a pipe joint 11 is disposed on one end of the heat exchanger 10 in the left-right direction. In addition, a large number of tubes 13 are arranged in parallel, and the heat radiating fins 14 are interposed in the gaps between the outer surfaces of adjacent tubes 13 to form the heat exchanging portion 12. The heat exchange unit 12 exchanges heat between the refrigerant flowing through the refrigerant passage in the tube 13 and the air flowing outside the tube 13. The heat radiating fins 14 increase the heat transfer area on the air side and promote the heat exchange.

  The upper and lower portions of the tube 13 are in communication with the tank 15, and the refrigerant circulates through the tubes 13 and the tank 15 and flows into and out of the heat exchanger 10 through the pipe joint 11. Each of these parts is made of, for example, an aluminum alloy.

  As described above, the tube 13 and the heat radiating fins 14 forming the heat exchanging portion 12 form the metal base material in the present invention, and as shown in FIG. 3, the metal base materials (the tube 13 and the heat radiating fins 14). First, the first film 51 is formed on the surface, and the second film 52 is further formed on the surface of the first film 51.

  The first film 51 is an undoped polyaniline film made of undoped polyaniline and / or a derivative thereof, and the second film 52 is a doped type made of polyaniline and / or a derivative thereof containing an organic acid as a dopant. A polyaniline film is used.

  In addition, if the metal (side plate etc.) other than the tube 13 and the radiation fin 14 is used in the heat exchange part 12 of the heat exchanger 10, the second film on the first film 51 is also applied to this metal. A polyaniline film in which 52 is formed may be formed.

  The first film 51 may be made of undoped polyaniline and / or a derivative thereof represented by the above chemical formula (Chemical Formula 1 or Chemical Formula 2). As the second film 52, a film made of polyaniline and / or a derivative thereof containing an organic acid represented by the chemical formula (Chemical Formula 3 or Chemical Formula 4) shown above as a dopant can be used.

  The organic acid that can be used as a dopant for the second film 52 is selected from a compound containing at least one of a phosphonic acid group, a fosiphonic acid group, a nitric acid group, a carboxyl group, a sulfonic acid group, a sulfinic acid group, and a hydroxyl group. Is at least one kind. For example, acid phosphoxy methacrylate having the above phosphonic acid group, p-styrene sulfonic acid having a sulfonic acid group, and the like can be used.

  In the heat exchanger 10 in which the undoped polyaniline film 51 is formed on the metal bases 13 and 14 and the doped polyaniline film 52 is formed thereon, when the temperature control device 1 is operated, the arrow A in FIG. The air containing the water vapor shown passes through the heat exchanger 10. At this time, when the heat exchanger 10 and the air come into contact with each other, the air temperature decreases due to the absorption of heat from the internal refrigerant. When the decreased temperature falls below the dew point, water vapor in the air becomes water droplets and heat exchange of the heat exchanger 10 occurs. It adheres as condensed water to the portion 12 (the surface of the doped polyaniline film 52 formed on the tube 13 and the radiation fin 14).

When the condensed water comes into contact with the doped polyaniline film 52, the polyaniline reduces dissolved oxygen (O ₂ ) in the condensed water (gives electrons to the dissolved oxygen), and superoxide anion radical (O ₂ ⁻ ) that is active oxygen. It becomes. And this active oxygen decomposes | disassembles odorous substances, microorganisms, bacteria, etc. in condensed water, without using special control. As a result, the air that has passed through the heat exchanger 10 is deodorized and sterilized, and clean air indicated by an arrow B in FIG. 2 is sent into the vehicle interior. When the heat exchanger 10 is not in operation, such as when the air conditioner is stopped, the condensed water is evaporated by the air passing through the heat exchanger 10 and the surface of the heat exchanger 12 is dried. Occurrences are automatically stopped.

  Further, according to the present embodiment, the undoped polyaniline film 51 protects the metal bases 13 and 14 to improve the rust prevention. For this reason, it is possible to provide a heat exchanger 10 that is prevented from metal corrosion due to condensed water and has a good antirust property while maintaining a deodorizing and sterilizing function.

  Further, since both the first film 51 and the second film 52 are made of polyaniline or a polyaniline derivative, the adhesion between the first film 51 and the second film 52 is excellent.

  Furthermore, by using an organic acid as a dopant imparted to the second film 52, the organic acid itself has a structure involving the polyaniline or the polyaniline derivative, so that the organic acid itself does not flow out into the condensed water. Therefore, the doped polyaniline used in the second film 52 is always kept in a doped state, can generate stable active oxygen, and can have a long life.

Rust prevention evaluation Surface Adjustment of Metal Substrate An aluminum alloy material (2 cm × 6.5 cm) used as a fin material for heat exchanger 10 is immersed in 200 ml of 5% sodium hydroxide aqueous solution maintained at 60 ° C. for 30 seconds, and then 30% It was immersed in 200 ml of nitric acid aqueous solution for 60 seconds, and then washed with tap water for 30 seconds. By this treatment, surface contaminants such as oil and oxide films formed on the surface of the aluminum alloy material were removed.

2. Preparation of Solution for First Film 51 Undoped polyaniline having an undoped polyaniline molecular weight of 10,000 (manufactured by Sigma-Aldrich) was used. 5 g of this polyaniline powder was dissolved in 95 ml of NMP (N-methyl-2-pyrrolidone) little by little while taking care not to agglomerate, thereby obtaining a 5% undoped polyaniline solution.

3. Solution Preparation of Second Film 52 Doped polyaniline used undoped polyaniline molecular weight 10,000 (manufactured by Sigma Aldrich) and acid phosphoxymethacrylate (trade name: manufactured by Hosmer M Unichemical) as an organic acid. The ratio of polyaniline and acid phosphoxymethacrylate was 5 g: 1 g, 5 g: 2.5 g, 5 g: 5 g, 5 g: 10 g, respectively. These were dissolved in 94 ml, 92.5 ml, 90 ml, and 85 ml of NMP to obtain dope-type polyaniline solutions. The doping rates at this time were 4.4%, 9.7%, 21.3%, and 47.5%, respectively.

4). Creation of first coating 51 The first coating (51) solution (undoped polyaniline solution) prepared in 2 above was applied to one side of the aluminum alloy material prepared in 1 above. The coating amount was such that the weight of polyaniline was 1 g / m ² . Next, the aluminum alloy material coated with the undoped polyaniline was allowed to stand for 20 minutes in a thermostatic chamber heated to 140 ° C. and dried.

5. Preparation of second coating 52 On the non-doped polyaniline coating prepared in 4 above, the second coating (52) solution (dope-type polyaniline solution) prepared in 3 above was applied on one side. The coating amount was such that the weight of polyaniline was 1 g / m ² . Next, the aluminum alloy material coated with the dope-type polyaniline was allowed to stand for 20 minutes in a thermostat heated to 140 ° C. and dried. The same procedure was performed for all polyanilines having a doping ratio of 4.4%, 9.7%, 21.3%, and 47.5%.

6). Sample Processing for Corrosion Current Density Measurement As shown in FIG. 4, the resin tape was cut out by 1 cm × 1 cm and attached to the polyaniline-coated surface of the sample prepared in 5 above (FIG. 4A) (FIG. 4B). )). The cut-out boundary surface of the tape was masked with a resin material (FIG. 4C).

7). Polarization measurement The measurement apparatus used the potentiostat / evaluation tank (HZ-3000 manufactured by Hokuto Denko) and the electrolytic solution (5% NaCl aqueous solution) shown in FIG.

The anodic polarization measurement was performed by bubbling the electrolyte solution with 1.0 L / min N ₂ for 30 min or more and degassing, then attaching the above 6 samples as shown in FIG. 5, and adjusting the potential from natural potential to -0.2 V vs SCE. The relationship between current and potential was collected. Cathodic polarization measurement was performed by bubbling the electrolyte solution with 1.0 L / min of dry air for 30 min or more to obtain an oxygen saturated state, and the above 6 samples were attached as shown in FIG. 5 and −1.5 V vs. natural potential. The potential was changed to SCE, and the relationship between current and potential was collected.

8). Corrosion Current Density Calculation From the measurement results of anodic polarization and cathodic polarization obtained in 7 above, the relationship between the absolute value of each current and the potential was plotted on a semi-logarithmic graph as shown in FIG. (Absolute values were taken on a logarithmic scale). The current density at this intersection is the corrosion current density.

9. Creation of Comparative Example As the case without the first film 51, a sample excluding the above 4 among the above 1 to 8 was created, and the corrosion current density was calculated.

10. Effect As shown in FIG. 7, from the relationship between the doping rate of the second film 52 and the corrosion current density in this example and the comparative example, the corrosion current density in this example was reduced to 1/10 compared to the comparative example. The effect of improving the rust prevention property by the first film 51 was confirmed.

Salt spray A first film 51 and a second film 52 were formed on the heat exchanger 10 made of an aluminum alloy material in the same manner as in Examples 1 to 5. This heat exchanger 10 was exposed to salt water for 240 hours with a salt spray test apparatus (manufactured by Suga Test Instruments), visually confirmed for the presence or absence of rust, and the rust ratio was calculated by image processing.

1. Calculation Method of Rust Rate About 5 mm square sample pieces were cut out from the heat exchanger 10 after exposure to salt water for a total of 9 sites of upper, middle, and lower, left, center, and right. The image of the sample piece was taken in as electronic data with an optical microscope, binarized with image processing software (white: rust, black: polyaniline), and the rust ratio was calculated based on Equation 1.

(Equation 1)
Rust rate = {white area ÷ (black area + white area)} x 100 (%)
2. Preparation of Comparative Example As in the comparative example in Example 1, a heat exchanger without the first film 51 except for 1 to 5 of Example 1 was prepared and exposed to salt water for 240 hours as described above. The presence or absence of rust was confirmed visually, and the rust rate was calculated by image processing.

3. Effect After the salt water exposure 240H, generation | occurrence | production of rust was not recognized by the heat exchanger 10 of the present Example 2, and the rust rate was 0%. In the heat exchanger of the comparative example, generation of rust was recognized, and the rust rate was 30%.

Verification of generation of active oxygen A first film 51 and a second film 52 were formed on the heat exchanger 10 made of an aluminum alloy material in the same manner as in Examples 1 to 5. A fin material of 1 cm ² was cut from the heat exchanger 10 and the active oxygen generation capacity was measured. In this measurement, the fin material is put into 1 ml of water, the water is taken out every 1 hour, 3 hours, and 5 hours, and the amount of hydrogen peroxide (H ₂ O ₂ ) generated is measured by measuring this water by ESR. Is. If active oxygen is generated by the reaction of water and polyaniline, hydrogen peroxide is detected by ESR measurement. Therefore, the greater the amount of hydrogen peroxide generated, the higher the active oxygen generation capacity.

FIG. 8 is a diagram showing the measurement results of this active oxygen generation capacity. As a comparative example, the result for a fin material of 1 cm ² obtained from a heat exchanger having only the second film 52 is shown.

  In this example, the hydrogen peroxide concentration became maximum when the doping rate was around 20%. On the other hand, in the comparative example, the hydrogen peroxide concentration when the doping rate was around 20% was about 1/3 of the present example. At this time, rust was generated in the comparative example.

  In the said embodiment, although the example which applies this invention to the heat exchanger (evaporator) 10 of the air conditioner for motor vehicles was shown, it applies also to heat exchangers, such as a domestic air conditioner, a refrigerator, and a dehumidifier. be able to.

It is sectional drawing which shows schematic structure of a temperature control apparatus. It is a perspective view which shows the external appearance of a heat exchanger (evaporator). It is sectional drawing which shows the metal base material in this invention. It is a figure which shows the process point of the sample for a corrosion current density measurement. It is sectional drawing which shows a polarization measuring apparatus. It is a figure which shows the relationship between each current density and electric potential of anodic polarization and cathode polarization in Example 1. FIG. It is a figure which shows the corrosion current density of Example 1 and a comparative example. It is a figure which shows the hydrogen peroxide generation amount of Example 3 and a comparative example.

Explanation of symbols

10 Heat exchanger (evaporator)
12 Heat Exchanger 13 Tube (Metal Base)
14 Radiation fin (metal base)
51 Undoped polyaniline film (first film)
52 Doped polyaniline film (second film)

Claims (8)

In the metal substrate (13, 14) provided with a film on the surface,
The coating comprises a first coating (51) formed on the metal substrate (13, 14) and a second coating (52) formed on the first coating (51). ,
The first film (51) is an undoped polyaniline film made of undoped polyaniline and / or a derivative thereof,
The second film (52) is a doped polyaniline film having a doping rate of 10 to 30%, comprising polyaniline containing an organic acid as a dopant and / or a derivative thereof,
The metal base material, wherein the organic acid is acid phosphoxymethacrylate. The undoped polyaniline film (51) is at least one polyaniline selected from the group consisting of polyaniline represented by the following chemical formula 1 or chemical formula 2:
The metal substrate according to claim 1, wherein the doped polyaniline film (52) is at least one polyaniline selected from the group consisting of polyaniline represented by the following chemical formula 3 or chemical formula 4.







  The metal substrate according to claim 1 or 2, wherein the molecular weight of the organic acid used for the doped polyaniline film (52) is 100 or more. The metal substrate according to any one of claims 1 to 3 , wherein the metal substrate (13, 14) is an aluminum alloy. In a heat exchanger having a heat exchange section (12) through which a heat exchange fluid flows,
The said heat exchange part (12) was formed from the metal base material (13, 14) in any one of Claims 1-4 , The heat exchanger characterized by the above-mentioned. The heat exchanger according to claim 5 , wherein the heat exchange fluid is a refrigerant that circulates in the refrigeration cycle. The heat exchanger according to claim 6 , wherein the heat exchange part (12) is used in an evaporator (10) for evaporating the refrigerant. The heat exchanger according to claim 6 or 7 , wherein the refrigeration cycle is used for an automobile.