JPS6410752B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a solar heat collector plate for a solar heat collector as a household water heater. Conventional structure and problems Conventional plastic solar heat collector plates are manufactured by blow molding a high-density polyethylene resin filled with carbon black, etc., but the surface has a selective absorption capacity for sunlight. I was bored. Further, as a means of achieving selective absorption ability on this surface, there was a method of painting, but the high density polyethylene resin of the base material layer had a large non-adhesive property, and sufficient adhesion could not be obtained. Purpose of the Invention The present invention provides a solar heat collecting plate in which a coating layer is provided on a base layer of high-density polyethylene resin, which increases the adhesion with high-density polyethylene resin, is inexpensive, and has the ability to selectively absorb sunlight. The purpose is to provide Structure of the Invention In order to achieve the above object, the present invention provides a surface layer of a base material layer mainly composed of high-density polyethylene resin.
On this base material layer, as an uneven surface of 250 μm or less,
It is provided with a coating layer that has the ability to selectively absorb sunlight. Description of Examples Examples of the present invention will be described below. The figure shows 3
Two layers are shown, and 1 is a base material layer whose main component is high-density polyethylene resin. Two layers, a first coating layer 2 and a second coating layer 3, are formed on the surface of the base layer 1. These have the ability to selectively absorb sunlight. The base material layer 1 mainly composed of high-density polyethylene resin has an uneven surface 4 of 250 μm or less on its surface. The first coating layer 2 is a coating layer for making the surface of the base material layer 1, which is mainly made of high-density polyethylene resin with a high thermal emissivity, into a low-emissivity surface, and is made of metallic powder 5 that exhibits a leafing effect. and a chlorinated polyethylene-modified alkyd resin 6 as a binder for obtaining good adhesion with the high-density polyethylene resin of the base material layer 1. The second coating layer 3 is
The coating layer has the ability to selectively absorb sunlight, has relatively good transparency in the infrared region, and has good adhesion to the first coating layer 2. Made from a pigment made of oxide or composite oxide 8 with good transparency, 5μm
The coating thickness is formed within a range not exceeding . The operation of the coating system consisting of the first coating layer 2 and the second coating layer 3 will be explained below. The a-plane side is a sunlight receiving surface, and the b-plane side is a heat medium. A indicates sunlight incident on the surface of this solar heat collector plate. Sunlight A is absorbed by the second coating layer 3 and converted into heat. The converted heat is thermally conducted through the first coating layer 2 and the base material layer 1, and is transferred to the heat medium b side. On the other hand, regarding radiation loss from the surface, since the second coating layer 3 is sufficiently transparent to infrared rays, the metallic powder 5 of the first coating layer 2
Since it is dominated by the properties of
Sufficient selective absorption ability can be provided on the base material layer 1. Conventionally, adhesion between the high-density polyethylene resin, which is the material of the base layer 1, and the first coating layer 2 was extremely difficult, but this problem was solved by using the chlorinated polyethylene-modified alkyd resin 6. Regarding adhesion with polyethylene resin, which is difficult to adhere to,
The technology of using chlorinated polyethylene resin is
It has been put into practical use as ink, etc., but most of them are relatively low molecular weight (molecular weight in the thousands) produced by a solution method and highly chlorinated with a chlorine content of 66% or more, and have poor adhesion to low-medium pressure polyethylene resin. was good, but there was a problem with the adhesion to high-density polyethylene resin. In this example, the molecular weight was tens of thousands to tens of thousands and the chlorine content was 30 to 50%, manufactured by an aqueous suspension method.
A chlorinated polyethylene modified alkyd resin, which is a mixture of chlorinated polyethylene resin and alkyd resin, was used. Since this chlorinated polyethylene modified alkyd resin 6 has a low chlorine content, the leafing properties of the metallic powder 5 are hardly impaired. Furthermore, since it has a large molecular weight and more structural similarities with high-density polyethylene resin, it has good adhesive properties. Further, in order to maintain the leafing properties of the metallic powder 5 while sufficiently improving the adhesion of the first coating layer 2, an epoxy resin was added to the chlorinated polyethylene modified alkyd resin 6. Epoxy resin is
The metallic powder 5 itself is coated in the first coating layer 2 while maintaining good leafing properties of the metallic powder 5.
Adheres stably inside. As the metallic powder 5, metals with leafing properties such as copper and aluminum can be used, but in this embodiment, coarse-grained aluminum powder was used. The blending ratio of metallic powder 5 when no special treatment is performed on the base material is 5 to 40 wt%.
It is best to use it within the range of Preferably 10~
A range of 25wt% provides optimal leafing properties and adhesion. Further, in order to obtain a surface with low infrared emissivity by the first coating layer 2, the higher the blending ratio of the metallic powder 5, the better. On the other hand, in terms of adhesion to the base material layer 1, if the blending ratio of the metallic powder 5 is increased, the adhesion becomes worse. In order to solve this problem, if a minute uneven surface 4 with an average size of 250 μm or less is formed on the surface of the base layer 1 made of high-density polyethylene resin, the bonding area will increase and the bonding force will become stronger. Since the blending amount of metallic powder 5 was increased by the same amount, the emissivity could be lowered without lowering the adhesion. When the first coating layer 2 is formed, a surface with a low emissivity almost equivalent to that of metal is realized. A second covering layer 3 having absorption capacity can be provided. The second coating layer 3 includes Fe, Mn, Cu, Cr,
One or more oxides or composite oxides 8 selected from the group of Ni and Co, acrylic resin, fluorine resin,
The main component is a binder 7 made of one or more synthetic resins selected from the group of urethane resins and alkyd resins. The pigment made of the metal oxide or composite oxide 8 has almost no infrared absorption and has good sunlight absorption ability. These oxides or composite oxides 8 used had particle sizes ranging from 0.01 to 0.5 μm. In the case of this particle size, the effect of scattering and absorbing sunlight well is remarkable. Acrylic resin, fluorine resin, urethane resin, and alkyd resin all achieve good adhesion with the first coating layer 2. The coating thickness of the second coating layer 3 was set within a range of not exceeding 5 μm, since if it was too thick, the selective absorption ability of sunlight would deteriorate. The evaluation results of the materials used for each coating layer are shown below. Made of high-density polyethylene resin (contains 1.5wt% carbon black), 95mm x 190mm
A plate with dimensions of ×10 mm was used as a test piece.
This is hollow inside and was molded by blow molding. Regarding this test piece, we divided the front and back into four zones of 95 mm x 95 mm.
For blow molding molds, 40, 60, 80, and
Using a sandblasted mold with a grain size of 100 mesh, molding was performed with minute irregularities formed in each of the four zones on the front and back sides. When the surface unevenness was evaluated using a scanning electron microscope, it was determined that the surface roughness was 40 mesh.
350μm, 60 mesh, 250μm, 80 mesh
An uneven surface with an average of 150 μm was formed with 180 μm and 100 meshes.

【table】

[Table] The paint having the composition shown in Table 1 was dispersed and prepared on the base layer 1 for 1 hour using a ball mill, and then the paint was coated on the base layer 1 with approx.
A coating thickness of 10-20 μm was applied and dried at 60° C. for 30 minutes. Table 2 shows the evaluation results of the characteristics of this first coating layer 2. The adhesion test in the table is
A cellophane tape peeling test was carried out, where × indicates peeling,
△ indicates that point-like peeling occurred.

[Table] Next, on each of the same coating layers, a second coating layer 3 consisting of a top coat of the composition shown below was coated. After dispersing and mixing the paint in a ball mill for 24 hours, a curing agent was added and diluted with approximately twice the amount of solvent, resulting in a thickness of approximately 1.5 μm.
Coated on the coating shown in Table 2 at a coating thickness of 60
Table 3 shows the results after drying at ℃ for 30 minutes. (1) Pigment: 50 parts by weight of "Dipyroxide Color #9550-F" (trade name) manufactured by Dainichiseika Chemical Co., Ltd. was used. (2) Synthetic resin: Asahi Glass Co., Ltd. “Lumiflon LD-200”
(Product name) Use 100 parts by weight. (3) Solvent: 200 parts by weight of "methyl isobutyl ketone:xylene = 1:1" was used. (4) Hardening agent: 14.8 parts by weight of "Coronate EH" (trade name) manufactured by Nippon Polyurethane Industries Co., Ltd. was used.

[Table] Looking at the results in Table 3, the adhesion is partially improved compared to Table 2, but this is due to the binder 7 of the second coating layer 3 penetrating into the first coating layer 2. This contributed to improved adhesion. In addition, a simulation evaluation of a natural circulation solar water heater showed that the heat collection efficiency was improved by approximately 5% compared to using an untreated plastic solar heat collection plate, and the annual heat collection amount was also approximately 5% higher. The result was that the amount of heat collected increased by 5%. In addition, the above-mentioned chlorinated polyethylene resin has a large molecular weight and high solution viscosity, so its compatibility with other resins is somewhat limited, but in order to achieve stable physical properties as a coating system, it can be used by mixing it with acrylic resin. It's okay. As described above, in this example, by using a cost-effective coating method, a coating layer with highly reliable selective absorption ability was applied to the base material layer 1 of high-density polyethylene resin, which was difficult to adhere to in the past. Compared to conventional plastic solar heat collecting plates without selective absorption treatment, the radiation loss from the heat collecting plate surface was reduced by more than half, improving efficiency. Effects of the Invention As described above, the present invention provides the following various excellent effects. Improving the efficiency of the solar heat collector plate is achieved by imparting selective absorption of sunlight. Since the surface of the base layer is provided with an uneven surface of 250 μm or less, leafing properties can be improved without deteriorating the adhesion with the first coating layer. Conventional solar heat collecting plates had the disadvantage of weather resistance deterioration and tyoke, but with the present invention, this problem is completely prevented by applying a highly weather resistant coating, resulting in high reliability as a solar heat collecting plate. It will be done. Since expensive metal plates and the like are not used, an inexpensive configuration is possible. The second coating layer, which is in direct contact with the outside air, can be made of a material with good rust prevention properties, so even when used in coastal areas, it will not rust and excellent durability can be expected.

[Brief explanation of drawings]

The drawing is an enlarged sectional view showing one embodiment of the present invention. 1... Base material layer, 2... First coating layer, 3... Second
Covering layer, 4... Uneven surface, 5... Metallic powder,
6... Chlorinated polyethylene modified alkyd resin,
7... Binder, 8... Oxide or composite oxide.

Claims (1)

[Claims] 1 A base material layer whose main component is high-density polyethylene resin, with irregularities of 250 μm or less formed on the surface, and a first coating layer containing metallic powder and chlorinated polyethylene-modified alkyd resin, which has the ability to selectively absorb sunlight. A solar heat collecting plate formed with a second coating layer.