JPH11183084A - Heat exchanger - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat exchanger which employs a resin coated metal member at low cost excellent in resistance to acid and heat and dew-point anticorrosion. SOLUTION: This heat exchanger empolys a metal member 1, the surface of which is coated with a protective layer 3 comprising a resin composition having 10-50 wt.% of an inorganic additive blended with at least one thermoplastic resin selected from a polyether-ether ketone resin, polyphenylene sulfide resin, polyethersulfone resin and a fluororesin through a primer layer 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a heat exchanger,
In particular, it relates to a heat exchanger excellent in durability and reliability.

[0002]

2. Description of the Related Art Heat exchangers used in water heaters, instantaneous water heaters, and the like usually have a coating layer having excellent acid resistance and heat resistance formed on the surface of metal members, especially heat exchange pipes. Thereby, the durability and the reliability are improved.

Conventionally, various methods have been proposed for forming a coating layer on the surface of a heat exchanger or a metal member. For example, Japanese Patent Application Laid-Open No. 58-123096 proposes a method of coating a heat-resistant paint on a base material surface of a heat exchanger using an inorganic polymer containing ultrafine metal powder as a binder. JP-A-59-1948 proposes a method of coating the surface of a heat exchanger with a paint obtained by mixing graphite and a dispersant in a binder. JP-A-59-122847 proposes a method in which a paint obtained by mixing a titanium organic compound with a binder of an inorganic polymer is applied to the surface of a heat exchanger. Further, Japanese Unexamined Patent Publication No.
Japanese Patent No. 308746 discloses a method of roughening the surface of a steel pipe by blast treatment, and coating an epoxy phenol resin or a phenol resin paint thereon through an epoxy primer.

Japanese Patent Laid-Open No. 62-209289 discloses that
A method has been proposed in which a metal selected from the group consisting of Ni, Cr and Mo is plated on the surface of a steel pipe and a polyphenylene sulfide resin layer is coated thereon via a chromate treatment layer. Also, JP-A-4-308746 discloses that
A method has been proposed in which metal spraying is performed in the form of islands on a steel material surface, and a resin layer of polyether sulfone, polyether ether ketone, or polyphenylene sulfide is laminated thereon. In addition, in Japanese Utility Model Publication No. 62-180233,
A method has been proposed in which an inorganic lining is formed on the surface of a structural material and a fluororesin layer is provided thereon. Further, Japanese Patent Application Laid-Open No. 4-86254 proposes a method in which a metal body surface is treated with a metal alkoxide and a thermoplastic resin layer is provided thereon.

[0005] Of the above methods, Japanese Patent Application Laid-Open No. 58-1230
No. 96, JP-A-59-1948, JP-A-59-122
847 and a method disclosed in JP-A-4-308.
The method disclosed in Japanese Patent No. 746 has a problem that the formed coating layer has low dew-point corrosion resistance.

[0006] Dew point corrosion refers to water vapor, SO _x and HC
in an environment containing l, acid occurs merges the SO _x and HCl in water condensed on the surface of the metal member, as a result, means that substantial corrosion blistering and cracking occurs and results in the coating. The above-mentioned Japanese Patent Application Laid-Open Nos.
The coating layer proposed or disclosed in Japanese Patent No. 308746 has low adhesion to a metal member in an environment containing water vapor, SO _x and HCl, and thus has low acid resistance and blister resistance, and low dew point corrosion resistance. Was. Also,
The acid resistance and heat resistance of the coating layer itself were insufficient, and the dew point corrosion resistance was low.

JP-A-62-209289, JP-A-4-209
In the methods proposed in JP-A-308746, JP-A-62-180233 and JP-A-4-86254, the formed resin layer has high adhesion and the acid resistance and heat resistance of the resin layer itself are high. Dew point corrosion resistance was high, but there was a problem of high cost. That is, in order to improve the adhesion, the metal member is subjected to surface treatment with metal plating, metal spraying, inorganic lining, or metal alkoxide before coating with a resin, so that the cost is high.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to provide a heat exchanger using a resin-coated metal member which is excellent in acid resistance, heat resistance and corrosion resistance at dew point and is inexpensive.

[0009]

In order to solve the above-mentioned problems, in the present invention, a polyetheretherketone (PEEK) resin, a polyphenylenesulfide (PPS) resin, a polyethersulfone (PES) resin and a fluororesin are used. A metal member having a protective layer made of a resin composition in which 10 to 50% by weight of an inorganic additive is blended with at least one selected thermoplastic resin and coated on the surface via a primer layer is used. A heat exchanger is provided.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1 shows a schematic cross-sectional view of a resin-coated metal member used for the heat exchanger according to the present invention.

In FIG. 1, a primer layer 2 for suppressing surface oxidation of the metal member 1 is first provided on the surface of the metal member 1.
Is formed, and the surface of the primer layer 2 is covered with a protective layer 3 made of a resin composition.

The metal member 1 includes, for example, steel, stainless steel, and the like. As the primer layer 2,
Although not particularly limited, examples thereof include a chromate film, an epoxy resin film, a phenol resin film, and a polyimide resin film, and the thickness is, for example, 3 to 20 μm.

In the present invention, the resin composition constituting the protective layer 3 is 10 to 50% by weight, preferably 10 to 50% by weight, based on at least one thermoplastic resin selected from PEEK resin, PPS resin, PES resin and fluororesin. A material containing 20 to 40% by weight of an inorganic additive is used. Examples of the inorganic additive include glass, metal oxide, and carbon.

When the content of the inorganic additive is less than 10% by weight or more than 50% by weight, the adhesion of the resin composition to the metal member 1 is reduced. Further, when the amount of the inorganic additive is less than 10% by weight, blisters are generated on the surface of the protective layer 3.

The thickness of the protective layer 3 is 100 to 150.
0 μm, preferably 200 to 1000 μm. PE
EK resin, PPS resin, PES resin, and fluororesin are thermoplastic resins having high acid resistance and high heat resistance, respectively. Therefore, by coating these resins on the surface, the acid resistance and heat resistance of the resin-coated metal member can be increased.

By blending the resin with an inorganic additive, the adhesion between the metal member 1 provided with the primer layer 2 and the protective layer 3 can be easily improved. The reason why the adhesion is improved is that the generation of residual stress at the interface between the metal member 1 provided with the primer layer 2 and the protective layer 3 can be suppressed by blending the inorganic additive. Since the coefficient of thermal expansion between the metal member 1 and the resin composition forming the protective layer 3 is different, the metal member 1 provided with the primer layer 2 and the protective member are cooled while the protective layer 3 is cooled from the baking temperature to room temperature. Residual stress occurs at the interface of the layer 3. This residual stress reduces the adhesion between the metal member 1 and the protective layer 3. However, by blending the inorganic additive as described above, the generation of the residual stress is suppressed, and the adhesion is improved.

As described above, as a result of the improved adhesion, acid resistance and blister resistance can be improved. as a result,
In combination with the excellent acid resistance and heat resistance of the thermoplastic resin itself, the dew point corrosion resistance of the resin-coated metal member can be increased.

In the present invention, a resin-coated metal member can be obtained at low cost. The reason is that high adhesion can be easily obtained only by blending the inorganic additive, so that it is not necessary to perform a special surface treatment using metal spraying or metal alkoxide before resin coating.

The inorganic additive also has a function of suppressing the penetration of water vapor and gas, which are corrosive components in the environment, in the thickness direction of the protective layer 3. As described above, a low-cost resin-coated metal member having excellent acid resistance, heat resistance, and dew-point corrosion resistance can be obtained.

Next, a method for forming the resin-coated metal member shown in FIG. 1 will be described. First, blast processing is performed on the surface of the metal member 1 such as steel. This is for cleaning and roughening the surface of the metal member to enhance the adhesion with the resin composition of the present invention, and is a well-known technique in the art. The blast treatment can be performed using sand, steel grid, steel shot, copper slag, air-blasted slag (blast furnace slag), or the like. As a result of the blasting process, the surface of the metal
The surface is roughened in the range of １００100 μm, preferably 20-40 μm. If the average roughness is less than 5 μm, it is difficult to obtain sufficient adhesion of the resin composition, and if it exceeds 100 μm, irregularities remain on the surface of the protective layer 3 after coating the resin composition.

The blasted surface is degreased.
The degreasing treatment can be performed by a method well known in the art. The primer layer 2 is formed on the surface of the degreased metal member 1. The method of forming the primer layer 2 is not particularly limited. For example, a method of forming a chromate film by chromate treatment using a solution containing chromic acid, or a polyurethane, epoxy, polyester, fluorine, silicon, etc. System, phenolic resin, polyimide synthetic resin, metal oxide, glass,
A method of blending an additive with a pigment such as carbon and forming a resin film to which a solvent is added as necessary is exemplified.

The surface of the primer layer 2 is covered with a protective layer 3. The coating is performed by applying and baking the resin composition of the present invention and then cooling. The baking temperature is usually about 380-430 ° C. for PEEK resin, about 350-400 ° C. for PPS resin, and about 380-42 ° C. for PES resin.
0 ° C. and about 310 to 420 ° C. in the case of a fluororesin.
The baking time is usually about 10 to 60 minutes.

Cooling after baking is preferably slow cooling. The reason is that if the temperature is rapidly cooled from the baking temperature (particularly 400 ° C. or higher), the protective layer 3 may crack or have fine wrinkles on the surface. It is more preferable to perform the annealing treatment during the slow cooling. Although the detailed annealing conditions vary depending on the resin used, for example, 150 to 200 ° C. can be used as the annealing temperature.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be specifically described below with reference to FIG. (Example 1) A blast treatment was performed on an outer surface of a steel pipe having an outer diameter of 38 mmφ, which is a metal member 1, and a primer layer 2 was formed on the surface using a chromate treatment solution. Then, the surface of the primer layer 2 was coated with a resin composition in which glass flakes were mixed with PEEK resin to form the protective layer 3, thereby producing a resin-coated steel pipe. The PEEK resin composition is first baked at 400 ° C. for 20 minutes.
This was performed by slow cooling at a cooling rate lower than ° C / min. The ratio of the glass flakes to be mixed with the PEEK resin composition was changed to 10, 20, 30, 40, 50, and 60% by weight, and resin-coated steel pipes were prepared at the respective mixing ratios.

Example 2 Instead of PEEK resin, PP
A resin-coated steel pipe was produced under the same conditions as in Example 1 except that S resin was used and the baking conditions were set at 380 ° C. × 20 minutes.

Example 3 Instead of PEEK resin, PE
A resin-coated steel pipe was produced under the same conditions as in Example 1 except that S resin was used and the baking conditions were set at 400 ° C. for 20 minutes.

(Comparative Example 1) A resin-coated steel pipe was produced under the same conditions as in Example 1 except that glass flakes were not mixed with PEEK resin.

Comparative Example 2 A resin-coated steel pipe was manufactured under the same conditions as in Example 2 except that no glass flake was mixed with the PPS resin.

Comparative Example 3 A resin-coated steel pipe was manufactured under the same conditions as in Example 3 except that no glass flake was mixed with the PES resin.

A heat exchanger was manufactured using each of the resin-coated steel pipes prepared in Examples 1 to 3 and Comparative Examples 1 to 3. Activate each heat exchanger, circulate hot water of 60 ° C. on the inner surface of each resin-coated steel tube,
The system was operated for one month by exposing it to an environment containing 1000 ppm of HCl and 100 ppm of SO _x in 20% by weight of water vapor at 0 ° C. After the operation of the heat exchanger was stopped, a JISK-5400 grid test was performed on the resin-coated steel pipe, and the adhesion of the protective layer 3 was compared between before and after one month of operation.

In the cross-cut test, four scratch lines in the vertical and horizontal directions are cut into the protective layer 3 at intervals of 2 mm with a cutter knife so as to reach the surface of the metal member 1. The coating of the protective layer 3 cut in a grid pattern in this manner is peeled off with an adhesive tape, and the adhesion is evaluated from the number of remaining grids. The state where the protective layer 3 is not peeled at all is scored 10 points, and as the peeling increases, the points are 8, 6, 4, 2, and 0 points. Eight or more points are regarded as having no practical problem, and six or less points are evaluated as defective.

After the operation for one month, the surface shape of the protective layer 3 was observed to confirm the occurrence of blisters. The test results are shown in Tables 1 to 3.

[0033]

[Table 1]

[0034]

[Table 2]

[0035]

[Table 3]

As is clear from the results in Tables 1 to 3, in Comparative Examples 1 to 3, when the glass flake content was 0% by weight, all types of resins were evaluated as poor due to blistering on the surface of the protective layer 3. You. Further, in Examples 1 to 3, when the glass flake content was 60% by weight, the adhesion of the protective layer 3 was low for all types of resins, and thus the resin was evaluated as 6 in the grid test, and was also evaluated as defective. . On the other hand, Example 1
In No. 3 to No. 3, when the glass flake content is in the range of 10 to 50% by weight, results of all kinds of resins are evaluated as good. Therefore, it can be seen that an optimum resin-coated steel pipe can be obtained in this range.

[0037]

As described above, according to the present invention, at least one thermoplastic resin selected from the group consisting of polyetheretherketone resin, polyphenylenesulfide resin, polyethersulfone resin and fluororesin is used.
A metal member whose surface is coated with a protective layer made of a resin composition in which an inorganic additive is blended by weight is excellent in acid resistance and heat resistance, and between the resin and the metal member. Because of high adhesion, it has excellent dew-point corrosion resistance and can be manufactured at low cost. Therefore, by using this metal member for the heat exchanger, especially for the most corrosive heat exchange pipe among the parts used in the heat exchanger, the acid resistance, heat resistance and durability of the heat exchange pipe are improved. Therefore, the durability and reliability of the heat exchanger itself can be improved.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a resin-coated metal member according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Metal member 2 ... Primer layer 3 ... Protective layer

Claims (1)

[Claims] 1. A resin composition in which at least one thermoplastic resin selected from a polyetheretherketone resin, a polyphenylenesulfide resin, a polyethersulfone resin and a fluororesin is blended with 10 to 50% by weight of an inorganic additive. A heat exchanger using a metal member whose surface is covered with a protective layer made of a material via a primer layer.