JP5145023B2 - Fin material for heat exchanger and manufacturing method thereof - Google Patents

Description

  The present invention relates to a fin material for a heat exchanger used in a heat exchanger such as an air conditioner, and a manufacturing method thereof.

  As a heat exchanger in an air conditioner or a refrigerator, a plate fin tube heat exchanger configured by combining a large number of plate fins and tubes is frequently used. Conventionally, aluminum is used for the plate fin because it is lightweight and excellent in thermal conductivity and workability.

In a heat exchanger used for an air conditioner, when contaminants typified by dust, dust, and oily smoke floating in the air adhere to the surface of the fin, it loses hydrophilicity and becomes water repellent ( Here, the water contact angle with water is 90 ° or more).
And with the operation of the air conditioner, the water condensed on the fin surface becomes water droplets and water splashes. Moreover, even in an outdoor unit in which water splash does not become a problem, it leads to a decrease in heat exchange performance and becomes a problem. In order to solve such problems, many inventions have been reported in which a material having a photocatalytic decomposition function is contained in a coating film for a fin material for a heat exchanger.

  When trying to apply a photocatalyst to the fin of an air conditioner, there is a problem that an epoxy resin, a urethane resin or the like is decomposed by the photocatalytic resolution. For this reason, it is desirable to apply a silicone resin or fluororesin that is difficult to be decomposed to the photocatalyst. However, since silicone resin and fluororesin are generally water-repellent, they are suitable for fin materials intended to maintain hydrophilicity. It has become difficult to apply.

In addition, there is a method of hydrophilizing the coating film by utilizing the superhydrophilization of the photocatalyst itself, but when added to a general silicone resin, the problem is that it takes a very long time to hydrophilize by photoexcitation. .
In addition, when the coating film shows water repellency, when the inorganic material adheres, there is no effect of washing away the dirt with water. The
Therefore, there is a demand for a coating film that has high organic matter decomposing ability but does not decompose the base resin and exhibits hydrophilicity in a short time.

JP-A-9-229585 Japanese Patent Laid-Open No. 9-40907 Japanese Patent Laid-Open No. 9-40909 JP-A-9-111188

  The present invention has been made in view of such conventional problems, and is intended to provide a fin material for a heat exchanger that exhibits hydrophilicity in a short time and has hydrophilic sustainability, and a method for producing the same. .

1st invention is the fin material for heat exchangers which consists of a board | substrate and the photocatalyst layer formed in the surface of this board | substrate,
The photocatalyst layer is formed by dispersing photocatalyst particles in a base resin made of silicone resin.
The silicone resin has a contact angle with water of 85 ° or less when forming a coating film made of only the silicone resin without containing the photocatalyst particles,
The content of the photocatalyst particles, Ri 10PHR~80PHR der,
The silicone resin has at least a tetrafunctional silicon structure represented by the general formula SiZ ₄ (Z represents either a hydrolyzable group or a residue bonded to another silicon atom through a siloxane bond). Heat exchange characterized by being formed using a silicone resin coating comprising an alkoxy oligomer containing 10 mol% or more of Q units as a unit with respect to all siloxane units and a quick-drying silicone resin. It exists in a dexterous fin material (Claim 1).

The fin material for a heat exchanger has a photocatalyst layer in which a predetermined amount of photocatalyst particles are dispersed in a base resin made of a specific silicone resin on the surface of the substrate.
That is, the silicone resin has a contact angle with water of 85 ° or less when a coating film made of only the silicone resin is formed without containing the photocatalytic particles. Therefore, the photocatalyst layer formed by dispersing the photocatalyst particles in the base resin made of the silicone resin can be hydrophilized in a short time without the base resin inhibiting superhydrophilization due to photoexcitation of the photocatalyst particles.

In addition, since the base resin is a silicone resin, the base resin is difficult to be decomposed by the photocatalyst particles and can hold the photocatalyst particles well, so that it exhibits photocatalytic activity such as hydrophilicity and organic decomposability over a long period of time. can do.
Thus, according to the present invention, it is possible to obtain a fin material for a heat exchanger that exhibits hydrophilicity in a short time and has hydrophilic durability.

The second invention is at least tetrafunctional silicon represented by the general formula SiZ ₄ (Z represents a hydrolyzable group or a residue bonded to another silicon atom through a siloxane bond). Preparation of photocatalyst layer coating material containing photocatalyst particles in a silicone resin coating material containing an alkoxy oligomer containing 10 mol% or more of Q units as a structural unit with respect to all siloxane units and a quick-drying silicone resin Then, a photocatalyst layer containing 10 PHR to 80 PHR of the photocatalyst particles is formed by applying the photocatalyst coating material so as to cover the surface of the substrate and drying the coating material. (Claim 7 ).

  In the method for producing the heat exchanger fin material, the photocatalyst layer is formed on the surface of the substrate using the specific photocatalyst layer forming coating material, and the heat exchanger fin material is produced. Accordingly, a photocatalyst layer in which a predetermined amount of photocatalyst particles are dispersed in a base resin having a hydrophilic group can be provided.

Therefore, the heat exchanger fin material obtained can be hydrophilized in a short time without the base resin inhibiting superhydrophilization by photoexcitation of the photocatalyst particles. In addition, since the base resin is a silicone resin, the base resin is difficult to be decomposed by the photocatalyst particles and can hold the photocatalyst particles well, so that it exhibits photocatalytic activity such as hydrophilicity and organic decomposability over a long period of time. can do.
Thus, according to this invention, the fin material for heat exchangers which shows hydrophilic property in a short time and has hydrophilic durability can be manufactured.

As described above, the heat exchanger fin material of the first invention includes a substrate and a photocatalyst layer formed on the surface of the substrate.
As the substrate, aluminum or an aluminum alloy is preferably used because it is lightweight and excellent in thermal conductivity and workability.

The photocatalyst layer is formed by dispersing photocatalyst particles in a base resin made of a silicone resin.
As the silicone resin, any silicone resin can be used as long as the contact angle with water at the time of forming a coating film made of only the silicone resin without containing the photocatalyst particles is 85 ° or less.
When the contact angle of the silicone resin with water exceeds 85 °, it takes a long time for the photocatalyst layer to exhibit hydrophilicity upon irradiation with ultraviolet rays, and lacks practicality. More preferably, the silicone resin has a contact angle with water of 70 ° or less.

The silicone resin having a contact angle of 85 ° or less is, for example, the silicone resin having at least a general formula SiZ ₄ (Z is a hydrolyzable group or a residue bonded to another silicon atom by a siloxane bond). For silicone resins comprising an alkoxy oligomer containing 10 mol% or more of the Q unit as a tetrafunctional silicon structural unit represented by the formula (1) and a quick-drying silicone resin. It can be formed using a paint .

  In addition, when the alkoxy oligomer and the quick-drying silicone resin are mixed, it is preferable to mix an organic solvent-based solvent with an organic solvent and an aqueous solvent with an aqueous solvent. In particular, an aqueous one may aggregate when the polarity (cation, anion, nonion) of the resin being emulsified is different, and therefore, in consideration of stability, it is preferable to align the polarity of the emulsion.

The Q unit is a silicon structural unit containing four hydrolyzable groups that can finally form a silanol group or can be condensed with other silicon to form a siloxane bond.
In addition, said Z may be 1 type in the residue couple | bonded with the other silicon atom by the hydrolyzable group or the siloxane bond, However, The combination of 2 or more types may be sufficient as it.
A conventionally known hydrolyzable group represented by Z can be used, and examples thereof include a methoxy group, an ethoxy group, a butoxy group, an isopropenoxy group, an acetoxy group, and a butanoxime group.

  In addition, the alkoxy oligomer is a silicone resin that is a polymer having an inorganic siloxane (Si-O) bond as a main skeleton and having various organic substituents in the branches and leaves. It refers to a low molecular weight silicone resin, and has a feature that it can be cured at room temperature / moisture.

And in the alkoxy oligomer which contains 10 mol% or more of Q units as tetrafunctional silicon structural units represented by the general formula SiZ ₄ with respect to the total siloxane units, the portion consisting of the above Q units is a side chain of Si. Both are alkoxyl groups. Therefore, when a photocatalyst layer is formed using a coating for silicone resin containing this alkoxy oligomer, a hydrophilic hydroxy group exists on the surface of the photocatalyst layer after curing, and hydrophilicity can be imparted to the photocatalyst layer. .

  And as long as the said alkoxy oligomer satisfy | fills the said conditions, any alkoxy oligomer may be used and it can manufacture by a conventionally well-known various method.

  The quick-drying silicone resin may be any known silicone resin as long as it dries within 30 seconds at 100 to 300 ° C. A suitable one may be selected from silicone alkoxy oligomers having no organic substituents, methylphenyl, phenyl, epoxy, mercapto, acrylic, etc.).

  Since the silicone resin paint contains a quick-drying silicone resin, the silicone resin paint can be dried in a short time, so that an effect of excellent productivity can be obtained. Moreover, the formed photocatalyst layer can have adhesiveness.

The silicone resin paint has a Q unit as the tetrafunctional silicon structural unit represented by the above general formula SiZ ₄ that reduces the drying property when the photocatalyst layer is formed in an amount of 10 mol% or more based on the total siloxane units. A photocatalyst with a low contact angle that is dried under pre-coating conditions, that is, within a period of 1 minute at 100 ° C. to 300 ° C., even if it contains an alkoxy oligomer contained therein, by blending with the quick-drying silicone resin. A layer can be formed.

  Moreover, you may use together a curing catalyst with the said coating material for silicone resins as needed. The curing catalyst can be appropriately selected from cationic, anionic and nonionic in consideration of the polarity of the emulsion used and the required drying speed.

As the photocatalyst particles, any substance that exhibits hydrophilicity by photoexcitation can be used. For example, titanium oxide, zinc oxide, tin oxide, lead oxide, ferric oxide, dibismuth trioxide. , Tungsten trioxide, strontium titanate and the like.
And from a chemical stability, cost, and a viewpoint of safety | security, it is preferable that the said photocatalyst particle uses a titanium oxide.

  The titanium oxide includes a rutile type, anatase type, and brookite type because of the difference in crystal form, and any of them can be used, but it is preferable to use an anatase type because of its high photocatalytic activity.

Further, the hydrophilization and organic decomposition of titanium oxide are reactions that occur on the surface of titanium oxide, and the larger the surface area, the higher the photocatalytic activity. Therefore, the average particle diameter of titanium oxide is 100 nm or less, more preferably 50 nm or less. is there. More preferably, it is 10 nm or less.
Moreover, you may use the said titanium oxide surface-treated with apatite etc.
The photocatalyst particles to be added are preferably those dispersed in water by a dispersant. Examples of the dispersant include nonionic surfactants, anionic surfactants, and inorganic dispersants.

The content of the photocatalyst particles is 10 PHR to 80 PHR (Parts per hundred Resin, the weight of the photocatalyst particles when the weight of the resin solid content in the photocatalyst layer is 100).
When the content of the photocatalyst particles is less than 10 PHR, the photocatalyst particles are not sufficiently exposed on the surface, and thus there is a possibility that the photocatalyst particles are not completely hydrophilicized even when exposed to light. On the other hand, when the content of the photocatalyst particles exceeds the resin solid content concentration of 80 PHR, the adhesion of the coating film may not be obtained.
The content of the photocatalyst particles is preferably 20 to 50 PHR.

Further, as a manufacturing method of the heat exchanger fin stock, for example, as shown in the manufacturing method of the heat exchanger fin material of the second invention, at least tetrafunctional silicon structural unit represented by the general formula SiZ ₄ As a photocatalyst layer coating material containing photocatalyst particles in a quick-drying silicone resin coating material, and preparing the photocatalyst coating material on the surface of the substrate. There is a method of producing a fin material for a heat exchanger by forming a photocatalyst layer by coating and drying so as to cover.

  The silicone resin coating is preferably applied to the surface of the substrate by roll coating or spray coating. Moreover, it is preferable to dry the said coating material for silicone resins on the conditions of less than 1 minute at 100-300 degreeC.

In the first and second inventions, the silicone resin paint preferably contains 10 to 90% of the alkoxy oligomer in a resin solid content concentration (Inventions 2 and 8 ).
When the content of the alkoxy oligomer is less than 10% in the resin solid content concentration, the hydrophilicity becomes insufficient, and the contact angle of the coating film may not be 85 ° or less. On the other hand, when the content of the alkoxy oligomer exceeds 90% in the resin solid content concentration, the coating film may not be dried.

Moreover, the silicone resin coating material is preferably a water-soluble emulsion type (claim 3, 9)
In this case, there is no risk of ignition / explosion at the time of painting, odor is reduced, and generation of VOC (volatile organic compound) gas is also suppressed. it can.

Moreover, it is preferable that the said photocatalyst particle is an anatase type titanium oxide whose average particle diameter is 100 nm or less (Claims 4 and 10 ).
In this case, as described above, since the surface area of titanium oxide is increased, the photocatalytic activity such as hydrophilization and organic decomposition occurring on the surface of titanium oxide is increased.

Further, the photocatalyst layer preferably has a surface roughness Ra of 0.1μm or more (claim 5, 11).
In this case, the photocatalyst particles are sufficiently exposed on the surface of the photocatalyst layer, and the organic decomposability can be exhibited well.
The coating film surface roughness Ra is more preferably 0.15 μm to 0.5 μm.
The surface roughness Ra here is based on JIS B0601-2001.

Moreover, it is preferable that a base treatment layer is formed between the substrate and the photocatalyst layer (claims 6 and 12 ).
In this case, the adhesion between the substrate and the photocatalyst layer can be improved.

  Chromate treatment such as phosphate chromate and chromate chromate as the undercoat layer, and non-chromate such as titanium phosphate, zirconium phosphate, molybdenum phosphate, zinc phosphate, titanium oxide and zirconium oxide other than chromium compounds There are films obtained by chemical film treatment (chemical conversion treatment) such as treatment. The chemical film treatment method includes a reaction type and a coating type, and any method may be employed in the present invention.

Example 1
In this example, heat exchanger fin materials (sample E1 to sample E14, sample C1 to sample C4) were produced as examples and comparative examples according to the fin material for heat exchanger of the present invention.
As shown in FIG. 1, the heat exchanger fin material 1 of this example includes a substrate 2 and a photocatalyst layer 3 formed on the surface of the substrate 2. The photocatalyst layer 3 is formed by dispersing photocatalyst particles 32 in a base resin 31 made of a silicone resin.
This will be described in detail below.

First, a Q unit as a tetrafunctional silicon structural unit represented by the general formula SiZ ₄ (Z represents a hydrolyzable group or a residue bonded to another silicon atom through a siloxane bond). A water-soluble emulsion type coating for a silicone resin prepared by mixing an alkoxy oligomer containing 10 mol% or more with respect to all siloxane units and a quick-drying silicone resin was prepared.

X-52-8212 manufactured by Shin-Etsu Chemical Co., Ltd. as an alkoxy oligomer containing 10 mol% or more of the Q unit as a tetrafunctional silicon structural unit represented by the above general formula SiZ ₄ with respect to all siloxane units and improving hydrophilicity. A water-soluble emulsion was prepared.
Further, as a quick-drying silicone resin that dries within 30 seconds at 100 to 300 ° C., a water-soluble emulsion of Shin-Etsu Chemical X-52-8148 was prepared.

First, the alkoxy oligomer and the quick-drying silicone resin are blended at a resin solid content concentration ratio shown in Table 1 without containing photocatalyst particles, and Shin-Etsu Chemical CAT-PM-4PS-2 is added as a curing catalyst. Thus, paints for silicone resin (resin 1 to resin 9) were produced.
And the said coating material for silicone resins was apply | coated on the aluminum plate of JIS A1050-H26 and thickness 0.1mm using a bar coater, and it dried on the conditions of 180 degreeC-200 degreeC for 20 second, and film thickness 2 micrometers. A coating film was prepared and the following characteristics were evaluated. The results are shown in Table 1.

<Adhesion>
The adhesion of the coating film made of silicone resin was evaluated by making a 4 cm incision reaching the substrate with a cutter knife, peeling the cellophane tape in close contact therewith, and checking for the presence or absence of coating film peeling. The case where peeling was not confirmed was set to pass (evaluation (circle)), and the case where peeling was confirmed was set to fail (evaluation x).

<Hydrophilicity>
The hydrophilicity of the coating film made of a silicone resin was evaluated by dropping 2 μL of pure on each test piece and measuring the contact angle of water droplets generated thereby with a goniometer.
The case where the contact angle was 85 ° or less was regarded as acceptable, and the case where the contact angle exceeded 85 ° was regarded as unacceptable.

As is known from Table 1, the resin 1 to the resin 7 have a contact angle with water of 85 ° or less when the coating film made of only the silicone resin is formed without including the photocatalyst particles, and the adhesiveness is also good. Met.
The resin 8 was made of a kind obtained by making X-52-8212 made by Shin-Etsu Chemical into a water-soluble emulsion, and the paint for silicone resin was not dried, and a coating film could not be formed.
In addition, the resin 9 was made of a kind obtained by making X-52-8148 made by Shin-Etsu Chemical into a water-soluble emulsion, and the contact angle was 90 °, and the hydrophilicity was unacceptable.

  Next, the photocatalyst particles 32 (an anatase type titanium oxide ST-01 (average particle size 8 nm) manufactured by Ishihara Sangyo Co., Ltd., dispersed in water) are dispersed in the above-described coating for silicone resin (resin 1 to resin 7 and resin 9). A photocatalyst layer coating was prepared by adding so that the weight of the photocatalyst particles when the weight of the photocatalyst layer was 100 was the amount shown in Table 2.

Also, as the base material 2, an aluminum plate with a material JIS A 1050-H26 and a thickness of 0.1 mm is prepared, and the chemical conversion film 4 is formed on the surface of the base material 2 by immersing phosphoric acid chromate. did.
Thereafter, a photocatalyst layer coating material is applied onto the chemical conversion film 4 using a bar coater and dried under the condition of 180 ° C. × 20 seconds, whereby the photocatalyst having the film thickness shown in Table 2 is formed on the surface of the substrate 2. The layer 3 was formed and the heat exchanger fin material 1 (sample E1 to sample E14 and sample C1 to sample C4) was produced.

For the obtained heat exchanger fin material 1 (samples E1 to E14 and samples C1 to C4), the surface roughness Ra of the photocatalyst layer 3 was measured, and hydrophilicity evaluation and organic matter decomposability evaluation were performed. The results are shown in Table 2.
<Surface roughness>
The surface roughness was measured using a Shimadzu confocal laser microscope OLS3000.

<Hydrophilicity evaluation>
Evaluation of hydrophilicity was performed by continuously irradiating the photocatalyst layer surface of the fin material for heat exchanger with ultraviolet rays (1500 μW / cm ² ), and after ultraviolet irradiation, the coating film at 0h, 24h, 48h, 72h, 144h, 240h, 500h, 1000h The contact angle between water and water was measured, and the time until hydrophilization was observed.
The case where the contact angle is 40 ° or less at 1000 h after UV irradiation is evaluated as Δ, the case where the contact angle is 40 ° or less at 500 h is evaluated as ○, and the case where the contact angle is 40 ° or less at 240 h. Evaluation ◎. The case where the contact angle exceeded 40 ° at 1000 h was evaluated as x. A case where the evaluation is Δ, ○, and ◎ is acceptable, and a case where the evaluation is × is unacceptable.

<Organic substance degradability>
Evaluation of organic substance decomposability was performed by bringing the methylene blue aqueous solution 5 into contact with the fin material 1 for heat exchanger and irradiating with ultraviolet rays 6 as shown in FIG. Specifically, first, a double-sided tape 7 having a 2 cm × 2 cm through hole was laminated on the surface of the photocatalyst layer 3 of the fin material 1 for heat exchanger. Next, the methylene blue aqueous solution 5 was put into the recess 71 formed by the heat exchanger fin material 1 and the through hole of the double-sided tape 7 to bring the photocatalyst layer 3 and the methylene blue aqueous solution 5 into contact with each other. A PET resin plate 8 having a thickness of 1 mm was laminated thereon to form a sealed state. In this state, the methylene blue aqueous solution 5 was irradiated with 1500 μW / cm ² of ultraviolet rays 6 through the PET resin plate 8 for 1 hour, and the color change of the methylene blue aqueous solution 5 was observed.
(Evaluation criteria)
◎: When the blue color disappears completely,
○: When the blue color almost disappears
△: When the blue color is a little thin,
X: When no change is seen in blue.

As can be seen from Table 2, Sample E1 to Sample E14 as examples are hydrophilized in a short time. Moreover, since the base resin of the photocatalyst layer of the samples E1 to E14 contains a hydrophilic silicone resin, it is difficult to be decomposed by the photocatalyst and can exhibit photocatalytic activity over a long period of time. It can also be seen that the larger the surface roughness Ra of the photocatalyst layer, the better the organic decomposability can be achieved.
From this, according to this invention, it turns out that the fin material for heat exchangers which shows hydrophilic property in a short time and has hydrophilic sustainability can be obtained.

Further, as is known from Table 2, the sample C1 as a comparative example was rejected because it did not contain photocatalyst particles.
Further, Samples C2 to C4 as comparative examples were unacceptable because the hydrophilicity of the base resin was low, and thus hydrophilicity could not be confirmed even after 1000 hours had elapsed after irradiation with ultraviolet rays.

Explanatory drawing which shows the fin material for heat exchangers in Example 1. FIG. Explanatory drawing which shows the organic substance decomposition property evaluation method in Example 1. FIG.

Explanation of symbols

1 Fin material for heat exchanger 2 Substrate 3 Photocatalyst layer 31 Base resin 32 Photocatalyst particles

Claims (12)

A fin material for a heat exchanger comprising a substrate and a photocatalyst layer formed on the surface of the substrate,
The photocatalyst layer is formed by dispersing photocatalyst particles in a base resin made of silicone resin.
The silicone resin has a contact angle with water of 85 ° or less when forming a coating film made of only the silicone resin without containing the photocatalyst particles,
The content of the photocatalyst particles, Ri 10PHR~80PHR der,
The silicone resin has at least a tetrafunctional silicon structure represented by the general formula SiZ ₄ (Z represents either a hydrolyzable group or a residue bonded to another silicon atom through a siloxane bond). Heat exchange characterized by being formed using a silicone resin coating comprising an alkoxy oligomer containing 10 mol% or more of Q units as a unit with respect to all siloxane units and a quick-drying silicone resin. Fin material for dexterity. 2. The fin material for a heat exchanger according to claim 1, wherein the silicone resin paint contains 10 to 90% of the alkoxy oligomer in a resin solid content concentration. 3. The fin material for a heat exchanger according to claim 1, wherein the silicone resin paint is a water-soluble emulsion type. The fin material for a heat exchanger according to any one of claims 1 to 3, wherein the photocatalyst particles are anatase-type titanium oxide having an average particle size of 100 nm or less. 5. The fin material for a heat exchanger according to claim 1, wherein the photocatalyst layer has a surface roughness Ra of 0.1 μm or more. The heat exchanger fin material according to any one of claims 1 to 5 , wherein a base treatment layer is formed between the substrate and the photocatalyst layer. Q unit as a tetrafunctional silicon structural unit represented by at least the general formula SiZ ₄ (Z represents either a hydrolyzable group or a residue bonded to another silicon atom through a siloxane bond) Of a photocatalyst layer in which a photocatalyst particle is contained in a silicone resin paint comprising an alkoxy oligomer containing 10 mol% or more of all siloxane units and a quick-drying silicone resin, and the photocatalyst paint A method for producing a fin material for a heat exchanger is characterized in that a photocatalyst layer containing 10 PHR to 80 PHR of the photocatalyst particles is formed by coating the substrate so as to cover the surface of the substrate and drying . 8. The method for producing a fin material for a heat exchanger according to claim 7, wherein the silicone resin paint contains the alkoxy oligomer in a resin solid content concentration of 10 to 90%. 9. The method for manufacturing a fin material for a heat exchanger according to claim 7 or 8, wherein the silicone resin paint is a water-soluble emulsion type. The method for producing a fin material for a heat exchanger according to any one of claims 7 to 9, wherein the photocatalyst particles are anatase-type titanium oxide having an average particle diameter of 100 nm or less. 11. The method for producing a fin material for a heat exchanger according to claim 7, wherein the photocatalyst layer has a surface roughness Ra of 0.1 μm or more. The method for manufacturing a fin material for a heat exchanger according to any one of claims 7 to 11 , wherein a base treatment layer is formed between the substrate and the photocatalyst layer.

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