Seawater structure

Abstract

To provide a seawater structure capable of suppressing the adhesion of sessile organisms and having a practical strength.SOLUTION: According to one embodiment, a seawater structure 1 comprises a first porous structure 2 and second structures 2a, 4, 5 being continuous with the first structure 2 and having a lower porosity than the first structure 2.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] FIELD OF THE INVENTION An embodiment of the present invention relates to a seawater structure. [Background technology]

[0002] In the aquaculture industry, contamination of fishing gear caused by marine fouling organisms such as barnacles is unavoidable, and removing contamination from fishing gear is a labor-intensive task. In recent years, the environmental impact of marine pollution caused by petroleum-derived resins has also become a problem. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-224363 Summary of the Invention [Problem to be solved by the invention]

[0004] A seawater structure is provided that is capable of suppressing adhesion of marine fouling organisms and has practical structural strength. [Means for solving the problem]

[0005] According to an embodiment, there is provided a structure for use in seawater, comprising a porous first structural part and a second structural part that is continuous with the first structural part and has a lower porosity than the first structural part.

[0006] According to the embodiment, there is also provided a fishing tool comprising the saltwater structure of the embodiment.

[0007] Furthermore, according to an embodiment, there is provided a housing for marine submersible equipment comprising the seawater structure of the embodiment. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is an external view showing a marine floating body as an example of a seawater structure according to an embodiment; [Figure 2] Top view of the offshore floating structure shown in Figure 1. [Figure 3] A cross-sectional view of the offshore floating structure shown in Figure 2 taken along line III-III. [Figure 4] FIG. 2 is an external view showing the upper member of the marine floating body shown in FIG. [Figure 5] FIG. 10 is an external view showing another example of the marine floating body according to the embodiment. [Figure 6] 1 is a plan view schematically showing a fishing net as an example of a seawater structure according to an embodiment; [Figure 7] 1 is an external view showing a housing for marine submersible equipment, which is an example of a seawater structure according to an embodiment; DETAILED DESCRIPTION OF THE INVENTION

[0009] The seawater structure of the embodiment is a structure that can be used in a state where the whole or part of it is in contact with seawater. Examples of the seawater structure include fishing gear and a housing for marine submerged equipment. Examples of fishing gear include marine floats, fishing nets, and fishing ropes. Examples of marine submerged equipment include buoys, ICT buoys for collecting oceanographic information, underwater drones, and seawater intake facilities.

[0010] The seawater structure of the embodiment will be described with reference to the drawings.

[0011] (floating body) Examples of offshore floating bodies are shown in Figures 1 to 4. Figure 1 is an external view of the offshore floating body. In Figure 1, the axial direction of the offshore floating body 1 is parallel to the z-axis direction. Furthermore, the end faces of the joints 5 of the outer wall 2 of the offshore floating body 1 are parallel to the plane defined by the x-axis direction and the y-axis direction. Figure 2 shows a top view of the offshore floating body 1 shown in Figure 1. Figure 3 shows a cross-sectional view obtained by cutting the offshore floating body 1 along line III-III. As shown in Figure 1, the offshore floating body 1 has an upper member 1A and a lower member 1B. Figure 4 shows an external view of the upper member 1A. The upper member 1A has a dome-shaped or bell-shaped outer wall 2. The outer wall 2 has a structural portion 2a and a joint 5. A circular opening 3 is provided near the top of the outer wall 2. A cylindrical inner wall 4 extends downward along the z-axis direction from around the opening 3 of the outer wall 2. Therefore, the upper end portion of the inner wall 4 also serves as the outer wall 2. The space defined by the inner wall 4 (including the opening 3) can function as a rope insertion hole. A cavity is formed between the inner peripheral surface of the outer wall 2 and the outer peripheral surface of the inner wall 4. The joint 5 is annularly formed at the lower end portion of the outer wall 2. The structural member 2a extends radially from the upper end portion of the inner wall 4 toward the joint 5. Meanwhile, the lower member 1B is formed by turning the upper member 1A upside down. The ring-shaped end surface of the joint 5 of the upper member 1A and the ring-shaped end surface of the joint 5 of the lower member 1B are overlapped and joined. Examples of joining methods include adhesives, hot plate welding, vibration welding, and ultrasonic welding. The interior of the float defined by the upper member 1A and the lower member 1B can be protected from exposure to seawater, wind, and rain.

[0012] The outer wall 2, excluding the structural portion 2a and the joints 5, is made up of a porous first structural portion. The structural portion 2a, the joints 5, and the inner wall 4 are made up of a second structural portion having a lower porosity than the first structural portion. In Figures 1 to 4, boundaries between the structural portion 2a and the joints 5, and between the outer wall 2 and the inner wall 4 in the outer wall 2 are shown to clearly distinguish them, but the second structural portion is continuous with the first structural portion. Therefore, there is no clear boundary indicating the position of the structural portion 2a and the joints 5 in the outer wall 2. There is also no clear boundary between the outer wall 2 and the inner wall 4. The offshore floating body 1 is an integrated object composed of a continuum consisting of the first structural portion and the second structural portion.

[0013] According to the offshore floating body 1 described above, the surface of the outer wall 2 that comes into contact with seawater is made of the porous first structural part, except for the structural part 2a and the joints 5, which makes it possible to prevent the attachment of marine fouling organisms such as barnacles. In addition, the structural part 2a, the inner wall 4 into which the rope is inserted, and the joints 5 for connecting the upper and lower members are made of the second structural part that is continuous with the first structural part and has a lower porosity than the first structural part. Therefore, because the outer wall 2 is reinforced by the second structural part, the offshore floating body 1 can maintain practical structural strength even when affected by seawater and weather.

[0014] 1 to 4, an example has been described in which a cavity is formed between the inner peripheral surface of the outer wall portion 2 and the outer peripheral surface of the inner wall portion 4, but the marine floating body of the embodiment is not limited to this example. The space defined by the inner peripheral surface of the outer wall portion 2 and the outer peripheral surface of the inner wall portion 4 may be occupied by a first structural portion.

[0015] 1 to 4 illustrate an example in which a rope insertion hole is disposed inside the marine floating body, but the marine floating body of the embodiment is not limited to this example. A rope insertion hole may be provided on the outer surface of the marine floating body. An example will be described with reference to FIG. 5. The marine floating body 6 shown in FIG. 5 comprises a float body main body 7 and a fixing part 8. The float body main body 7 has a hollow, approximately spherical shape. The float body main body 7 may be made of a porous first structural part, or may have a structural part made of a second structural part with low porosity. The fixing part 8 is provided on the outer peripheral surface of the float body main body 7. The fixing part 8 has a through hole 9 for inserting a rope. The fixing part 8 is made of a second structural part with low porosity.

[0016] (fishing net) An example of a fishing net is shown in Figure 6. Figure 6 is a plan view of a fishing net. Fishing net 10 is made up of wires 11 with a core-sheath structure woven into a mesh pattern. Wires 11 have a core material 12 and a coating layer 13 that coats the surface of core material 12. Coating layer 13 is made up of a porous first structural portion. Core material 12 is made up of a second structural portion that is less porous than the first structural portion. In Figure 6, the boundary between core material 12 and coating layer 13 is shown to clearly distinguish between core material 12 and coating layer 13, but because the second structural portion is continuous with the first structural portion, there is no clear boundary between core material 12 and coating layer 13. The wires that make up fishing net 10 are a single unit composed of a continuum consisting of the first structural portion and the second structural portion.

[0017] In FIG. 6, the wires constituting fishing net 10 are composed only of wires 11 having a core-sheath structure, but this is not limited thereto. The parts of fishing net 10 that require structural strength may be composed of wires 11, and the other parts may be composed of wires made of a porous first structural part. Also, in this example, core material 12 and covering layer 13 are shown as a single rope, but these may also be twisted together. Examples of parts that require structural strength include parts where wires are joined or crossed, and parts that are attached to structures (for example, floats, ship hulls, and posts for securing the fishing net to the seabed).

[0018] According to the fishing net 10 described above, the coating layer 13 of the wires 11 comes into contact with seawater, but because the coating layer 13 is made of a porous first structural part, it is possible to prevent the attachment of marine fouling organisms such as barnacles. Furthermore, the core material 12 of the wires 11 is made of a second structural part that is continuous with the first structural part and has a lower porosity than the first structural part, and therefore has a higher structural strength than the coating layer 13. Therefore, the fishing net 10 can maintain a practical structural strength even when it is affected by seawater and weather.

[0019] (Enclosure for marine submersible equipment) An example of a marine immersion device is an underwater (undersea) drone. An example of a housing for marine immersion device is shown in Figure 7. Housing 20 shown in Figure 7 includes case 21 and lid 22. Case 21 has storage section 21a and fixing section 21b. Storage section 21a has a hollow dome shape. Storage section 21a has an opening on the opposite side to its top. Fixing section 21b is provided on the periphery of the opening of storage section 21a. Fixing section 21b is structured so that it can be screwed in from multiple points. Meanwhile, lid 22 has storage section 22a and fixing section 22b. Storage section 22a has a cylindrical shape with one side closed. Fixing section 22b is provided on the periphery of the opening of storage section 22a. Fixing section 22b is structured so that it can be screwed in from multiple points. To prevent water (seawater) from entering the housing 20, the fixing portion 22b of the lid 22 is placed on the fixing portion 21b of the case 21 via a sealant (not shown), such as rubber, and these are fixed liquid-tightly with bolts 23 and nuts 24. The functional components of the underwater (subsea) drone are housed in the space defined by the inner wall surface 25a of the case 21 and the inner wall surface 25b of the lid 22. The storage portions 21a and 22a each comprise a porous first structural portion. The fixing portions 21b and 22b require structural strength to ensure liquid-tightness. Depending on the application, they may also be used to fix the housing 20 to a target structure (e.g., a support for fixing the housing to the seabed) with screws or the like. In this case, such a structural portion may be present in addition to the interface between the storage portions 21a and 22a. The fixing portions 21b and 22b comprise a second structural portion with lower porosity than the first structural portion. In Figure 7, the boundaries between storage section 21a and fixed section 21b and between storage section 22a and fixed section 22b are shown to clearly distinguish between storage section 21a and fixed section 21b and storage section 22a and fixed section 22b. However, because the second structural section is continuous with the first structural section, there is no clear boundary between storage sections 21a, 22a and fixed sections 21b, 22b. Housing 20 is a single unit composed of a continuum consisting of the first structural section and the second structural section. Furthermore, because underwater drones must be able to withstand water pressure, it is also possible to optionally provide a low-porosity structure with high structural strength in areas requiring structural strength equal to or greater than that of fixed sections 21b, 22b, although this is not shown.

[0020] According to the marine submersible equipment housing 20 described above, the outer surfaces of the case 21 and the lid 22 come into contact with seawater, but because the storage sections 21a, 22a are made of porous first structural sections, the adhesion of marine fouling organisms such as barnacles can be suppressed. Furthermore, the fixing sections 21b, 22b are made of second structural sections that are continuous with the first structural sections and have lower porosity than the first structural sections, and therefore have higher structural strength than the storage sections 21a, 22a. Therefore, the marine submersible equipment housing 20 can maintain practical structural strength even when exposed to the effects of seawater and weather.

[0021] The structures of the embodiments are not limited to marine floats, fishing nets, and housings for marine submersible equipment, but include other examples. For example, the wire that makes up a fishing net may be used as a fishing rope. Marine floats can be applied to ICT buoys for meteorological observation and various other types of floats. The materials, microstructures, manufacturing methods, etc. of the structures of the embodiments are described below.

[0022] The structure of the embodiment is preferably formed from a material containing polylactic acid. Lactic acid eluted from polylactic acid can inhibit marine sessile organisms such as barnacles (e.g., barnacles) from attaching to the structure. It is more preferable that polylactic acid be the main component of the material constituting the structure. Here, the main component means the component that accounts for the largest proportion of the constituent materials.

[0023] The first structural portion is preferably made of a foam, which can enhance the effect of inhibiting the attachment of marine sessile organisms such as barnacles (for example, barnacles).

[0024] The average pore diameter of the first structural part can be, for example, 1 μm or more and 500 μm or less. This can enhance the effect of suppressing the adhesion of marine sessile organisms such as barnacles (e.g., barnacles). It is presumed that the reason why the adhesion suppression is promoted by setting the average pore diameter within the above range is because the antennal disc of barnacle cypris larvae has a size of approximately 30 μm.

[0025] The second structural part has a lower porosity than the first structural part, and therefore can have a higher structural strength than the first structural part. The second structural part may not have pores, in other words, may have a non-porous structure.

[0026] The following experiment was conducted to investigate the ease with which barnacle larvae attach to structures. Barnacle larvae were raised in the laboratory. Samples A to D shown in Table 1 below were prepared. Each sample was in the shape of a plate measuring 46 mm x 16 mm x 4 mm. The porosity of the expanded polylactic acid in sample A was 50%, and the pore size was 500 μm or less (average pore size 500 μm or less). The proportion of polylactic acid in the constituent materials of each of samples A to C was 50% or more.

[0027] [Table 1]

[0028] Each sample and 100 barnacle larvae were placed in a container. This was stored indoors for 12 days, and the ease of attachment (attachment rate) was evaluated by visually counting the number of larvae that had attached to the top surface of each sample. The results are shown in Table 2 below.

[0029] [Table 2]

[0030] As is clear from Table 2, Samples A to C, which have a porous structure and are primarily composed of polylactic acid, have a higher barnacle adhesion inhibitory effect than Samples D and E, which are made of ABS, a common resin, or glass plate. Of Samples A to C, Sample A, which is primarily composed of foamed polylactic acid, was superior in barnacle adhesion inhibitory effect. As shown by the above results, by constructing the structure of the embodiment from foamed polylactic acid, it is possible to improve the effect of inhibiting the adhesion of marine fouling organisms such as barnacles.

[0031] The method for producing the structure of the embodiment is not particularly limited. The structure can be produced, for example, by a foam molding method. Examples of the foam molding method include bead foaming, batch foaming, press foaming, extrusion foaming, foam blow molding, atmospheric secondary foaming, and injection foam molding. A wire having a core-sheath structure can be molded, for example, by extrusion foaming. A specific example is described below. A mold for manufacturing tubes is used, and resin is extruded into the mold to obtain a resin molded product that will serve as the core material. Polylactic acid is foamed, and the periphery of the resin molded product is covered with a polylactic acid foam. In this way, a wire having a core-sheath structure is obtained. The resin molded product may contain polylactic acid.

[0032] The marine float can be molded, for example, by injection foam molding. A specific example will be described. In injection foam molding, after filling a cavity with molten resin containing a foaming agent, the movable part is moved in the opposite direction relative to the fixed part to expand or further promote foaming, thereby obtaining a foamable resin molded product. In injection foam molding, the bubble diameter of the first structural part and the second structural part is controlled by changing the expansion ratio depending on the location in the mold. By reducing the bubble diameter of the second structural part, it is possible to make the porosity of the second structural part lower than that of the first structural part. In this way, the marine float of the embodiment can be obtained.

[0033] According to at least one of these embodiments, the seawater structure includes a porous first structural part and a second structural part that is continuous with the first structural part and has a lower porosity than the first structural part, thereby making it possible to suppress adhesion of marine fouling organisms while maintaining a practical structural strength.

[0034] The invention according to the embodiment will be described below. (1) a porous first structure portion; a second structural portion that is continuous with the first structural portion and has a lower porosity than the first structural portion; A seawater structure comprising: (2) The seawater structure according to (1), which is made of a material containing polylactic acid. (3) The structure for seawater according to (1) or (2), wherein the first structural portion has an average pore diameter of 1 μm or more and 500 μm or less. (4) The seawater structure according to any one of (1) to (3), wherein the second structural portion has a structural strength higher than that of the first structural portion. (5) A fishing gear comprising the seawater structure according to any one of (1) to (4). (6) A housing for marine submersible equipment, comprising the structure for seawater according to any one of (1) to (4).

[0035] Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, and are also included in the scope of the invention and its equivalents as defined in the claims. [Explanation of symbols]

[0036] 1...offshore float, 1A...upper member, 1B...lower member, 2...outer wall portion, 2a...structural portion, 3...opening, 4...inner wall portion, 5...joint portion, 6...offshore float, 7...float main body portion, 8...fixing portion, 9...through hole, 10...fishing net, 11...wire, 12...core material, 13...coating layer, 20...housing for marine submersible equipment, 21...case, 22...lid body, 21a, 22a...storage portion, 21b, 22b...fixing portion, 23...bolt, 24...nut, 25a...inner wall surface of storage portion 21a, 25b...inner wall surface of storage portion 22a

Claims

1. a porous first structure; a second structural portion that is continuous with the first structural portion and has a lower porosity than the first structural portion; A seawater structure comprising:

2. The seawater structure according to claim 1, which is made of a material containing polylactic acid.

3. 3. The structure for seawater according to claim 1, wherein the first structural portion has an average pore diameter of 1 μm or more and 500 μm or less.

4. The seawater structure according to claim 1 or 2, wherein the second structural portion has a structural strength higher than that of the first structural portion.

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