JPS58200958A - Forming method of heat collecting surface for solar heat - Google Patents

Abstract

PURPOSE:To improve the selective absorbency of solar heat and the stability of a coated film by coating the surface of a heat collecting plate with special paints and heating and curing the film at a specific stoving temperature. CONSTITUTION:Paints manufactured by adding a disperser to a mixture of one kind or more of oxides, multiple oxides and metallic superfines selected from a group of Fe, Mn, Cu, Cr, Co and Ni in a base polymer (a resin) and a pigment and mixing them together with a solvent are applied onto the metallic substrate 6 of the heat collecting plate. The film is heated and cured at the stoving temperature of 50 deg.C or more, higher than a curing temperature of the single base polymer (the resin). Accordingly, the solar-heat selective absorption film 5 at an extremely high level can be formed.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is applied to the surface of a heat collector that collects all solar energy, and is mainly applied to a metal heat collecting plate to provide the surface with selective absorption of solar heat. This invention relates to a method of forming a hot surface.

Due to the energy situation in recent years, solar energy utilization technology is attracting more and more attention, and active development and practical application to home water heaters and the like are being promoted.

As a heat collecting plate for efficiently collecting solar heat in a solar heat collector, the wavelength range of solar radiant energy (Q, 2 to 2.
6μm) uses a surface that has optical spectral characteristics that absorb energy very close to that of a perfect black body, and that emits as little heat as possible as the temperature of the heat collecting plate itself increases, that is, a selective absorption surface. It is known to do.

Conventional selective absorption surfaces include black plating with Or, Ni, etc., black oxide film formed by chemical conversion treatment, and those treated by methods such as vacuum evaporation and sputtering.

However, the plating method requires advanced technology to always achieve a uniform finish, and its role is complex, making it especially difficult to process large items. In addition, chemical conversion treatment generally has problems with durability, as the film lacks heat resistance and adhesion to the base material, and discoloration tends to cause metallization.

Furthermore, management of the processing liquid is extremely complicated.

Similar to plating methods, vacuum evaporation and sputtering methods are difficult to completely process large-sized items. These technologies have common problems such as increased costs, lack of productivity (mass production), and difficulty in obtaining stable quality.

Furthermore, a method using paint has also been proposed.

The method of using this paint is advantageous in terms of productivity and cost, but in terms of selective absorption, if you try to increase the total absorption rate of solar energy, the emissivity will also increase, so how can you improve the emissivity? The challenge in forming the entire heat-collecting surface was how to lower it. C. In order to form a complete coating film on a metal substrate using a paint and make it a surface that selectively absorbs solar heat, it is necessary to use a black pigment that has excellent absorption of light with a wavelength of 2.5 μm or less. This is because although the absorption rate of sunlight can be made relatively high, normally even light with a wavelength of 2.6 μml is absorbed, so the emissivity at this wavelength also becomes high. The general idea of how to achieve all of this is to take advantage of the fact that metal surfaces reflect infrared rays well, and to make the coating thickness as thin as possible to reduce the absorption of infrared rays of 2.6 μm or more, which means lowering the overall emissivity. There is a way to stop it. In the case of this method, the selection of paint components such as binders and pigments is extremely important for achieving selective absorption of solar heat. It has a high absorption rate of sunlight, and 2.
It is important to be as transparent as possible to infrared rays above 5 μm 1d, and pigments are particularly important among paint components. It is necessary that this is uniformly dispersed and does not contain any impurities.

Although certain metal oxide pigments have relatively good absorption of sunlight, with only 1V of infrared absorption, there is still room for further improvement in absorption characteristics, especially in the near-infrared region, and film thickness and absorption There is a relationship between absorption rate and emissivity, and as mentioned above, there is an optimal film thickness range in which the thicker the film, the higher the absorption rate and the emissivity, and conversely, the thinner the film, the lower both. However, there were limits to the performance of this type of pigment alone.

In view of the above-mentioned conventional drawbacks, the present invention has improved the formation method in order to further reduce the emissivity, increase the absorption rate of sunlight even with a thin film, and ensure reliability as a surface treatment. The overall purpose of this invention is to provide a method for forming a solar heat collecting surface with extremely high performance in terms of both selective solar heat absorption and coating film properties.

In order to achieve all of the above objects, the present invention provides that the base polymer (resin) and the pigment are Fe, Mn, Cu, Cr, G.
o.

Painting on the surface of the heat collector plate using a paint consisting of a mixture of one or more oxides or composite oxides selected from the NthO group and ultrafine metal powder, with the addition of a dispersant and mixed with a solvent. Then, the curing temperature was 50°C, which was higher than the curing temperature of the resin alone.
Baking at temperatures higher than 0.9°C means that the coating film is cured by heating at a temperature that allows the entire surface to selectively absorb solar heat.

By having the above-mentioned structure, the present invention can disperse the pigment extremely uniformly in the resin, significantly improve the hiding power of the thin film, and reduce the emissivity and maintain and improve the absorption rate of the thin film. In particular, after painting, if the temperature is higher than the curing temperature of the resin alone, which is higher than the curing temperature of 60°C, the entire coating film will be cured by heating, so the resin 9 dispersant etc. that makes up the entire paint will be Various trace additives and impurities contained therein can be blown away by heat, and as a result, an extremely stable final coating film can be obtained.

In other words, dispersants play an extremely important role in promoting uniform dispersion when preparing paints and preventing sedimentation when the paint is left to stand. These contain various small amounts of additives, such as stabilizers, deterioration preventive agents, and preservatives that are used to preserve the paint. These effects can be eliminated.

Embodiments of the present invention will be described below with reference to all the accompanying drawings.

Fig. 1 is a plan view of a solar heat collector to which the heat collecting surface obtained by the present invention is applied, Fig. 2 is a sectional view taken along line A-A' of the first area, and Fig.
The figure shows an enlarged cross-sectional view of the main parts of the heat collecting plate surface (light receiving surface side).

In these drawings, 1 is a box body of a solar heat collector, 2 is a heat insulating layer 11 provided in the box body 1, and placed on both inner surfaces and the inner lower part of the box body 1; 4 is a transparent housing cover provided on the upper end of the box body 1; 5 is a solar heat selective absorption film formed by coating and baking on a metal base material 6; be.

Stainless steel, copper, aluminum, etc. are used as the metal base material 6, and as mentioned above, it is preferable that the metal base material 6 has a higher surface reflectance, but the metal base material 6 is limited to these materials here. isn't it.

When sunlight enters through the transparent protective cover 4, the sunlight is absorbed by the solar heat selective absorption film 6 formed on the surface of the heat collecting plate, and the resulting heat is transmitted through the metal base material 6 by thermal conduction. , heat is exchanged with water or a medium and stored as hot water. At this time, the ideal selective absorption surface is one that absorbs as much corner energy as possible, and as a result of which the radiant energy from the surface whose temperature has increased is as small as possible, and the heat collection efficiency of the solar collector is significantly improved. Two.

Next, the selective absorption paint applied to the surface of the heat collecting plate and the method for forming the heat collecting surface of the present invention will be described.

Thermosetting acrylic resin “Dianaru 5E-” is used as the resin.
100 parts by weight of ts661J (trade name), as a pigment, Fe, Mn, Cu41M composite oxide 1F-6331j (trade name) with an average particle size of 0.6 μm and F with an average particle size of 300 μm.
e Ultrafine powder 'ji-9675 mixed at a ratio of 52
Parts by weight, solvent: [Tsurupez #100] (trade name) 1
00 parts by weight, n-butanol 60 parts by weight, Kinrol 4
0 parts by weight, and as a dispersant, a 2% xylene solution of polyether-modified silicone was used.
Add 0.29t1 to the total amount and use a whole mill.
The mixture was dispersed and mixed for 4 hours and made into a paint.

Next, for painting and baking, the mixed paint is diluted with twice the amount of the same solvent as this paint, and the base material Nialuminum (
160B

The coating was spray-painted using an air pressure of 2.5 to 3 kg/c4)k, dried at room temperature, and then heated and cured for 30 minutes at 260° C., which is higher than the temperature at which the coating itself is cured, to form a coating film.

The thickness of the coating film completed at this time was 1.3 μm.

When the selective absorption was measured for the above sample, the solar absorption rate (α) (10,955i) was shown, and the emissivity (ε)
was 0.15.

The level of selective absorption achieved by the conventional coating method is at the highest level, with an absorption rate α of 0.94. Emissivity ε=06
It is about 35.

(Old - absorption rate α is Shimabara Seisakusho spectrophotometer @+MPs-60
Total spectral reflectance was measured using Model 00 and evaluated from the ratio to black body emissivity at 60000K.
Measured using a PANY emissivity meter,
In both cases, the average value is given when the number of test pieces is 71=5.

As described above, in the examples of the present invention, an extremely high level of selective absorption is obtained. This is due to the use of a mixed system of pigment total oxide, composite oxide, and ultrafine metal powder, which play a central role in the selective absorption of sunlight, and the addition of a dispersant. It is a thin film because it is uniformly dispersed in the resin and prevents separation of the resin and pigment and precipitation of the pigment when the paint is left to stand or is dried at room temperature after painting and before baking. Nevertheless, it seems that the hiding power of the coating film was significantly improved, and that low emissivity and high absorption rate were ensured and improved. This is because ultrafine metal powder and pigment are all evenly distributed inside the coating film.
If it is dispersed and mixed in a well-balanced manner, the sunlight will not pass through the paint film, but will be scattered within the paint film, resulting in more opportunities for it to be absorbed by the pigment. As mentioned above, it is thought that a high level of absorption rate could be achieved even with an extremely thin film thickness.

In addition, pigments play an important role in selectively absorbing paints applied to the heat collecting plates of 1% solar heat generators. In order to achieve selective absorption, absorption of infrared red below 2.5 μm should be avoided as much as possible, and from this point of view, Fe is a particularly good pigment.

Examples include oxides and composite oxides of one or more selected from the group consisting of Mn, Cu, Or, Go, and Ni0. This is due to the characteristics of red IA rays as mentioned above, but as these pigments, Goo・Cr2O3
・Mn02-Fe2O3, F6203*MnO*CuO
, CuO++ Cr2O3, among which Fe2
It is thought that this is because the pigment of 0s*MnO*CuO is optimal, and the selective absorption property is further improved due to the combination with ultrafine metal powder and the homogenization effect by the dispersant.

When applied to the heat collection plate of a solar heat collector, it is important to achieve selective absorption properties, as well as to fully ensure the physical properties of the coating and long-term human surface treatment reliability. Furthermore, in the present invention, regarding the method of forming the W hot surface, if coating 11.k is . It improves hiding power by preventing precipitation, sedimentation, and pigment separation, and especially when resin 1' is hardened by itself.
By completely heating and curing the coating film at temperatures higher than 50°C each time, the resin is stabilized, and even sensitive additives and impurities can be blown away by heat, making the coating film hard. As for physical properties, corrosion resistance (
Sufficient results were obtained for severe adhesion evaluations such as salt spray, Cath tests, etc.), heat resistance, weather resistance, impact of falling balls after hitting the base, heat shock, and tape peeling. Regarding resins, dispersants, etc., various sensitive additives are blended as mentioned by Ail, and when the final coating is formed,
Particularly when trying to achieve selective absorption of solar heat, for example, absorption in the infrared region appears because the light absorption characteristics of the additives are different.

Therefore, in the case of forming a final coating film, it is more convenient for this purpose that this type of substance is not present in the coating film. As a method of forming the heat collecting surface, after coating the solar heat selective absorption paint, the coating film is heated and cured at a temperature of 60°C or higher, which is higher than the curing temperature of the resin alone. It is thought that the additives were dispersed more easily, the impurities were dispersed, and the coating was stabilized.According to the confirmation by the present inventors, the resin was less transparent than the infrared rays due to χ・1. The present invention does not limit the resin, but is at least 5 % higher than the curing temperature of the resin IP alone.
It has been fully confirmed that this objective can be achieved by heat curing at temperatures below 0°C.

However, C, which raises the entire heating curing temperature for trimming, can lead to deterioration of the resin itself due to heat, and the curing temperature of the resin alone is V, which is extremely high! It is not convenient to make it easy, and from that effect, -t!L is in the range of 50 to 100'.

As shown in C, the selective absorption of solar heat and the human face of one coating p
lj Very good reliability 2S: Result is 117 et al.
However, it is 1 in the formation method of tree 5c Akira! T et al! 1. A selective absorption surface was formed by incorporating heat treatment into the heat treatment I.
1. Heat Niji 3: About, by Tsuyumi Resion,
(11! shi.

Natural fJ + 'i ring J (heat collector) The effect was evaluated.), the current ''i coating type selection 1 absorption 1 which is at a high level.
・, even when compared with ko(α0.94.ε −0,35), it is 4
~5') The result of ()'s efficiency completion knob is (j).

1゛Work 1-, 1. (Construction of the solar heat collector invented by Koi X)j ij.

('According to this, Ping l・(as, turtle and monster, compound t-1
, I'm going to make a mixture with Beerle 4 super 1 scattering) in January,
This mixture: Kosara (a paint made by adding a dispersant and mixing it with a solvent). Baking of 50"G or higher, which is higher than ffa IJj, is done by heating and curing Coating 119 at a temperature, which improves selective absorption and stability of Coating 11 (&) regarding surface treatment reliability. As a result, there are various immediate improvements such as cost reduction, energy saving effect, and improvement of equipment durability and reliability. fL can be very effective.

[Brief explanation of drawings]

FIG. 1 shows a solar collector 11 showing an embodiment of the present invention.
The heat treatment surface view, Figure 2 is the A-A' cross section of Figure 1,
FIG. 3 is an enlarged sectional view of the mounting portion on the surface of the heat collecting plate. 5...-solar heat selective absorption film, 6...metal,
(phase.

Claims (1)

[Claims] The pace polymeric resin and the pigment are Fe, Mn, Cu, Or
. Using a paint for selectively absorbing solar heat, which is made of a mixture of one or more oxides or composite oxides selected from Go, Ni0 groups, and ultrafine metal powder, to which a dispersant is added and mixed with a solvent. A method for forming a solar heat collecting surface in which a solar heat selective absorption surface is formed by coating the surface of a heat collecting plate and then heating and curing the coating film at a baking temperature of 60°C or higher, which is higher than the curing temperature of resin alone.