Tunnel cultivation supports

Abstract

To provide a post for plastic tunnel cultivation that is less prone to seizing.SOLUTION: A post for plastic tunnel cultivation 10 comprises a core 30 coated with a resin composition comprising a thermoplastic synthetic resin, forming a coating layer 40. The resin composition of the coating layer 40 comprises inorganic matter 20-50 wt.%. The surface roughness Ra of the coating layer 40 is 1 μm or more, and the skewness of the roughness curve is smaller than 0, ensuring that adhesion of a film 20 to the post 10 is reduced, and the seizing of the post 10 can be prevented.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a tunnel cultivation support used for agricultural and horticultural purposes. [Background technology]

[0002] Tunnel cultivation involves creating a tunnel-shaped frame made of resin-coated metal pipe supports on top of the ridges and covering it with film, which is expected to have the effects of preventing pests from entering and also providing heat retention and protection from rain, etc. Generally, a greenhouse for tunnel cultivation has a tunnel-shaped frame made of multiple arc-shaped supports arranged in a row at predetermined intervals, and these supports are covered with a resin film made of polyolefin such as polyethylene or polypropylene, or polyvinyl chloride.

[0003] In tunnel cultivation, if the temperature inside becomes too high, it is necessary to fold up part of the film to ventilate and maintain the appropriate temperature. When the film is folded up, discoloration may occur in the resin coating (coating layer) of the support where the film was in contact, a condition known as pole burning. Burning of the coating layer is thought to occur due to a combination of factors, including the migration of additives in the film, high temperatures, and deterioration of the coating layer. In particular, film made from soft polyvinyl chloride is prone to burning, as it contains a relatively high content of additives such as plasticizers.

[0004] The present applicant has also proposed a tunnel cultivation support in which the arch-shaped support that forms the framework of a tunnel cultivation greenhouse is formed by coating the outer surface of a core material with a synthetic resin layer to form a support body with a circular cross section, and lattice-like protrusions are provided on the surface of the synthetic resin layer that comes into contact with the resin film that covers the greenhouse, and the lattice-like protrusions extend in a direction that intersects with the longitudinal direction of the support body with a circular cross section, and the support body is bent in an arc shape. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 11-56125 Summary of the Invention [Problem to be solved by the invention]

[0006] In such tunnel cultivation supports, the aforementioned tunnel cultivation supports can suppress seizure of the support by reducing the contact area between the support and the resin film. However, such supports are usually made by extruding a resin onto a metal tube as a core material, and a special molding device is required to form lattice-shaped protrusions on the surface of the resin coating. Another method involves molding a sheet with lattice-shaped protrusions and attaching it to the metal tube, but this creates a seam in the sheet along the longitudinal direction of the metal tube. Since such supports are typically bent into an arc when used, there is a risk of the sheet peeling off at the seam.

[0007] Incidentally, seizure of the support occurs near the point where the film and the covering layer of the support are in contact, and it is thought that the more likely the adhesion between the two is to continue, the more likely it is to occur. In other words, the more likely it is that the more likely it is that the adhesion between the film and the support is to continue, the more likely it is that seizure of the support will occur.

[0008] In tunnel cultivation greenhouses, the supports are covered with a film, resulting in partial contact. However, it was found that in the morning, morning dew adheres to the inside of the film, forming a water film near the contact point, causing the film and the support (covering layer) to adhere tightly to each other. The water film persists until it evaporates, so the longer the water film persists, the more closely the film and covering layer adhere to each other. Furthermore, on sunny days, the support tends to become hotter from morning to noon, making it easier for additives such as plasticizers to bleed out onto the film surface. Once the water film evaporates, the adhesion is resolved, but the additives that bleed out onto the surface migrate to the support due to physical contact between the film and the support caused by wind, etc. This repeated migration of additives and the high temperature of the support are thought to make the support more susceptible to seizure.

[0009] One condition that makes it easy for a water film to form between the film and the support is that the surface of the support's coating layer is easily absorbed by water, that is, the surface roughness of the coating layer is relatively rough. However, as a result of extensive research, we have discovered a tunnel cultivation support that makes it difficult for the aforementioned water film to form and for the film to adhere to the surface by coating a metal tube with a resin containing a specified inorganic substance and by ensuring that the surface roughness of the coating resin has specified characteristics. [Means for solving the problem]

[0010] In order to achieve the above object, the present invention has the following configuration: That is, the support for tunnel cultivation according to the present invention is a support for tunnel cultivation in which a core material is coated with a resin composition containing a thermoplastic synthetic resin to form a coating layer, and the resin composition of the coating layer is calcium carbonate The coating layer has a surface roughness Ra of 1 μm or more and a skewness of the roughness curve of less than 0. [Effects of the Invention]

[0011] According to the present invention, by providing the coating layer with a surface roughness having a predetermined characteristic, it is possible to prevent the film from sticking to the support posts, and prevent the support posts from seizing. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a front view showing an embodiment of a support for tunnel cultivation according to the present invention.

[0023] FIG. [Figure 2] FIG. 2 is an enlarged cross-sectional view taken along the line AA in FIG. [Figure 3] FIG. 1 is a perspective view showing a state in which the tunnel cultivation support according to the present invention is used. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[0014] In the drawings, reference numeral 10 denotes a tunnel cultivation support according to the present invention, 20 denotes a film, and a plurality of tunnel cultivation supports 10 are provided at predetermined intervals as shown in Fig. 3, and a synthetic resin film 20 is placed over the tunnel cultivation supports 10 to form a tunnel cultivation house 100. In Fig. 3, reference numeral 50 denotes a connecting cord for connecting the tunnel cultivation supports 10, and 60 denotes a stake that secures the end of the film 20.

[0015] Figure 1 is a front view showing one embodiment of a tunnel cultivation support 10. The tunnel cultivation support 10 is bent in an arc, with both ends tapered. As shown in Figure 3, the tunnel cultivation support 10 is used by burying both ends in the ground.

[0016] Figure 2 is an enlarged cross-sectional view taken along line AA in Figure 1. The tunnel cultivation support 10 has a circular cross section, with the outer circumferential surface of the core material 30 being coated with a resin composition containing a thermoplastic synthetic resin to form a coating layer 40. The core material 30 is generally made of a steel wire or steel pipe with a circular cross section, but other hollow or solid elongated bodies such as fiber-reinforced synthetic resin may also be used.

[0017] The coating layer 40 is formed from a resin composition containing an inorganic substance in a thermoplastic synthetic resin such as a polyolefin (e.g., polyethylene or polypropylene) or polyvinyl chloride. In this embodiment, calcium carbonate is used as the inorganic substance. The content of calcium carbonate as the inorganic substance is 20 to 50% by weight. If the resin composition of the coating layer 40 is colored white, it can suppress the absorption of heat from sunlight, etc. Furthermore, if it is colored green, it becomes similar in color to the leaves of the cultivated plants and is less noticeable. To form the coating layer 40 on the core material 30, it is preferable to coat it by extrusion molding.

[0018] Examples of synthetic resins used for the film 20 include polyolefins such as polyethylene and polypropylene, and polyvinyl chloride. When a polyolefin-based resin is used as the resin composition for the coating layer 40, it is preferable that a different synthetic resin such as polyvinyl chloride be used for the film 20. This makes it easier to prevent the tunnel cultivation support 10 from seizing.

[0019] Next, an embodiment of a support for tunnel cultivation according to the present invention will be described.

[0020] Example 1 A long support pole was fabricated by extruding a resin composition onto a steel pipe with a diameter of 12.7 mm and a thickness of 0.5 mm to form a coating layer. The resin composition consisted of 100 parts by weight of polyethylene, 100 parts by weight of an inorganic composition (17% by weight of polypropylene, 80% by weight of calcium carbonate, and 3% by weight of additives), and 6 parts by weight of a pigment composition containing a white pigment. The coating layer was approximately 0.9 mm thick. This support pole was cut to a length of 3 m, and the central section was bent into an arc with a curvature of 250° to form a support pole for tunnel cultivation. The blending ratio of the resin composition is shown in Table 1.

[0021] [Table 1]

[0022] (Water film evaluation) The tunnel cultivation supports were set up approximately every 90-100 cm along the ridges, and a soft polyvinyl chloride film was placed over them to create a tunnel cultivation greenhouse. In the morning, morning dew adhered to the inside of the film, forming a water film near the contact point. Since the water film dissipates as the temperature rises, if the water film remained after 10:00 AM on a sunny or cloudy day, it was judged that the water film remained and was rated as "×." If the water film dissipated by 10:00 AM, it was judged that the water film was unlikely to remain and was rated as "○." The evaluation results are shown in Table 1.

[0023] (surface roughness measurement) The surface roughness of the coating layer of the prepared tunnel cultivation supports was measured. The measurement parameters for surface roughness were the arithmetic mean roughness (Ra) and the skewness of the roughness curve (Rsk). The measurement conditions are described below. The measurement results are shown in Table 1.

[0024] (Surface roughness measurement conditions) Equipment name: Surface roughness and shape measuring instrument (Tokyo Seimitsu Co., Ltd.) Model: Surfcom 130A Measurement method: stylus type Measurement type: Roughness measurement Measurement speed: 0.300mm / s Cutoff value: 0.250 mm Evaluation length: 5.0 mm Measurement range: ±40 μm Calculation standard: ISO4287:1997 Tilt correction: Straight line λc filter: Gaussian λs filter: cutoff ratio 300

[0025] Example 2 Similar tunnel cultivation supports were produced using resin compositions with different blending ratios compared to Example 1. The blending ratios of the resin compositions, the water film evaluation, and the measurement results of surface roughness are shown in Table 1.

[0026] (Comparative Example 1) Similar supports for tunnel cultivation were produced using resin compositions with different blending ratios compared to Example 1. The blending ratios of the resin compositions are shown in Table 1.

[0027] In Comparative Example 1, the Rsk value is positive, so it is expected that there are few peaks and the contact area between the film and the coating layer is small. However, when moisture penetrates between the film and the coating layer, coupled with the small Ra value, a water film is formed over a wide area, including the valleys of the coating layer, rather than only between the peaks of the coating layer and the film, and the water film is difficult to dissolve.

[0028] On the other hand, in Examples 1 and 2, the Rsk values ​​are negative, so there are many peaks, and it is expected that the contact area between the film and the coating layer is large. However, if moisture penetrates between the film and the coating layer, the large Ra value means that the moisture is likely to spread to the periphery. Therefore, when moisture from the peripheral area evaporates with rising temperatures, the water is likely to be transferred to the peripheral area through the valleys of the coating layer, and even in the water film, some of the moisture in the valleys flows to the peripheral area, creating areas where the water film is partially interrupted. This results in the formation of areas where no water film is formed, and the force holding the film and coating layer together in those areas is weak, making them more likely to peel off, which is thought to make the water film more likely to dissolve. [Explanation of symbols]

[0029] 10 Tunnel cultivation support 20 Film 30 Core material 40 Covering layer 50 Connecting string 60 stakes 100 Tunnel cultivation house

Claims

[Claim 1] A support for tunnel cultivation in which a core material is coated with a resin composition containing a thermoplastic synthetic resin to form a coating layer, the resin composition of the coating layer contains 20 to 50% by weight of calcium carbonate, A tunnel cultivation support characterized in that the surface roughness Ra of the coating layer is 1 μm or more and the skewness of the roughness curve is less than 0.

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