Float and method for manufacturing float

Abstract

To provide a float with a structure that has a long service life and can be manufactured by reusing a used float.SOLUTION: A float 10 includes: a core part 11 including polystyrene foam; an outer peripheral part 12 covering the periphery of the core part and made of hard polyurethane foam; and a protection part 13 for protecting the surface of the outer peripheral part. The protection part is preferably made of a polyurea resin.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a float used in fisheries, and particularly to a float suitable for use in a cultivation raft for oysters, cultured fish, etc.

Background Art

[0002] For floats (buoys) used in oyster cultivation rafts, etc., those made mainly of polystyrene foam are mainly used. However, polystyrene foam floats are deteriorated by ultraviolet rays and seawater, and are damaged by contact with raft members and ships, and there is concern about the outflow of their fragments into the ocean. Also, because of their short service life, the disposal of a large amount of used floats has become a problem.

[0003] Regarding these problems, Patent Document 1 describes protecting a cultivation buoy made of foamed polystyrene, etc. by covering it with a protective cover formed by molding a cloth laminated with a polyolefin-based film into a bag shape. Patent Document 2 describes a float whose strength is improved by applying polyurea to expanded polystyrene or the like.

[0004] Regarding the disposal of used floats, Patent Document 3 describes an apparatus for peeling off the surface layer portion to which shellfish such as barnacles and seaweeds are attached when disposing of used expanded polystyrene floats by heat melting or incineration. Also, attempts have been made to reduce the volume of used expanded polystyrene floats to make them into solid fuel and use them as fuel for boilers, or to utilize the exhaust heat thereof.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, even when using the protective cover described in Patent Document 1, barnacles such as attached barnacles may break through the cover. In that case, the crushed polystyrene foam will flow into the ocean. Further, in the float of Patent Document 2, it is considered that physical properties such as bending strength are improved by applying a polyurethane resin. However, in the polyurethane resin film, it is impossible to prevent the internal expanded polystyrene from being dented or damaged by an impact such as contact with a ship. Regarding the treatment of used floats, even if it is possible to recover thermal energy by solid fuelization or the like, there are also problems such as the cost of reprocessing. It is more desirable if it can be reused as a material.

[0007] The present invention has been made in consideration of the above, and an object thereof is to provide a float having a structure with a long service life and capable of manufacturing using a used float by reusing it.

Means for Solving the Problems

[0008] The float of the present invention has a core part containing polystyrene foam, an outer peripheral part covering the periphery of the core part and made of rigid polyurethane foam, and a protective part covering the surface of the outer peripheral part.

[0009] Here, the rigid polyurethane foam includes isocyanurate foam.

[0010] With this configuration, the service life of the float can be extended. Further, with this configuration, it is also possible to reuse a used float as the core part.

[0011] Preferably, the protective part is made of a polyurethane resin. The polyurethane resin has high durability and can maintain the waterproof function for a long time. Also, due to the tough physical properties of the polyurethane resin, the protective part is less likely to be damaged by impacts such as contact with ships or raft members, and can protect the interior.

[0012] Preferably, the core part is a used float. By reusing the used float, the number of floats to be discarded can be reduced.

[0013] When the core part is a used float, preferably, the outer peripheral part is made of an injected rigid polyurethane foam. Thereby, even if the shape of the used float is distorted due to wear, a float having the same shape as a new one can be obtained.

[0014] Alternatively, the core part may be formed by molding fragments of polystyrene foam or expanded polystyrene beads. Also in that case, preferably, the outer peripheral part is made of an injected rigid polyurethane foam.

[0015] Another float of the present invention has a core part formed by molding fragments of rigid polyurethane foam, an outer peripheral part that covers the periphery of the core part and is made of rigid polyurethane foam, and a protective part that covers the surface of the outer peripheral part. Preferably, the protective part is made of a polyurethane resin. Also, preferably, the outer peripheral part is made of an injected rigid polyurethane foam.

[0016] The method for manufacturing the float of the present invention includes a step of preparing a used float, a step of setting the used float in a foam mold, a step of injecting a rigid polyurethane foam stock solution into the foam mold, foaming and curing it to form an outer peripheral part that covers the periphery of the used float, a step of demolding a molded body composed of the used float and the outer peripheral part, and a step of providing a protective part on the surface of the outer peripheral part.

[0017] Another method for manufacturing the float of the present invention includes a step of preparing a core made of polystyrene foam, a step of spraying a hard polyurethane foam stock solution onto the surface of the core, foaming and curing it to form an outer peripheral portion covering the periphery of the core, and a step of providing a protective portion on the surface of the outer peripheral portion.

[0018] Still another method for manufacturing the float of the present invention includes a step of setting in a foam mold a molded product formed from fragments of polystyrene foam or fragments of hard polyurethane foam, a step of injecting a hard polyurethane foam stock solution into the foam mold, foaming and curing it to form an outer peripheral portion covering the periphery of the bag, a step of demolding the molded body composed of the bag and the outer peripheral portion, and a step of providing a protective portion on the surface of the outer peripheral portion.

Advantages of the Invention

[0019] According to the float of the present invention, the protective portion protects the core portion and the outer peripheral portion from sunlight and seawater. Further, the outer peripheral portion made of hard polyurethane foam absorbs impacts caused by contact with a ship or the like, and attenuates the impacts transmitted to the core portion, thereby suppressing damage to the expanded polystyrene. As a result, the service life of the float can be extended. Further, even if the protective portion may be torn, the outer peripheral portion can prevent the outflow of the polystyrene foam. Furthermore, according to the float of the present invention, since the used float can be reused as the core portion, the number of floats to be discarded can be reduced.

Brief Description of the Drawings

[0020]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Best Mode for Carrying Out the Invention

[0021] As a first embodiment of the float of the present invention, a float obtained by reusing a used float will be described.

[0022] Referring to FIG. 1, the float 10 of this embodiment is cylindrical. The float 10 has a core portion 11, an outer peripheral portion 12 that covers the periphery of the core portion 11, and a protective portion 13 that covers the surface of the outer peripheral portion 12. The size of the float 10 can be determined according to the application, but it is preferably about 200 to 1000 mm in diameter and about 400 to 1500 mm in length. For use in a culture raft, typically, the diameter is about 600 to 850 mm and the length is about 1000 to 1200 mm.

[0023] The core portion 11 is a used float and is a part for providing sufficient buoyancy to the float 10. The used float may be dented or worn as a result of long-term use on a culture raft or the like. The core portion 11 contains polystyrene foam. Further, the core portion 11 preferably consists essentially of polystyrene foam. Existing floats may be blended with resins other than polystyrene foam to improve various properties, and the core portion 11 may be a used product of such a float. That the core portion 11 consists essentially of polystyrene foam means that the core portion 11 has polystyrene foam as the main component and can obtain sufficient buoyancy according to the application of the float 10. For example, it contains 80% by mass or more of polystyrene foam.

[0024] The outer peripheral portion 12 covers the entire core portion 11, absorbs an impact from the outside, and attenuates the impact transmitted to the core portion 11. The outer peripheral portion 12 is made of a closed-cell rigid polyurethane foam. The rigid polyurethane foam includes an isocyanurate foam. The rigid polyurethane foam is obtained by reacting a polyol and a polyisocyanate as main raw materials in the presence of a catalyst, a foaming agent, a foam stabilizer, and other auxiliaries.

[0025] The rigid polyurethane foam that constitutes the outer peripheral portion 12 of the present embodiment is a poured rigid polyurethane foam. The density of the outer peripheral portion 12 is not particularly limited, but the core density inside the outer peripheral portion is usually 8 to 60 kg / m 3 and preferably 15 to 50 kg / m 3 and more preferably 20 to 40 kg / m 3 If the density of the outer peripheral portion is too low, it will be too soft, and conversely, if the density is too high, it will be too hard. In either case, it cannot sufficiently absorb the impact from the outside, and the impact transmitted to the core portion 11 will increase. Note that the density of the poured rigid polyurethane foam can be slightly adjusted by changing the overpack (overfilling) rate into the mold.

[0026] The thickness of the outer peripheral portion 12 varies depending on the location if the shape of the core portion 11 is irregular, but preferably, the thinnest part is 5 mm or more. If the thickness of the outer peripheral portion 12 is 5 mm or more, it has sufficient durability and can sufficiently attenuate the impact from the outside.

[0027] The protective portion 13 covers the entire outer peripheral portion 12 and protects the inside from seawater. The protective portion 13 is made of a polyurea resin. The polyurea resin is formed by mixing and stirring a polyisocyanate prepolymer as the main agent and a polyamine as the curing agent. The polyurea resin has high durability and can maintain the waterproof function for a long time. Also, the polyurea resin has high strength and toughness and is difficult to break even against a large impact. Further, the polyurea resin also has good adhesiveness to the rigid polyurethane foam that constitutes the outer peripheral portion 12.

[0028] The thickness of the protective portion 13 is preferably 0.5 mm or more, more preferably 1.5 mm or more. This is to obtain sufficient strength so that the protective portion does not tear. On the other hand, the thickness of the protective portion is preferably 10 mm or less, more preferably 5 mm or less. This is because if the protective portion is too thick, it will reduce the buoyancy of the float 10 and also increase the manufacturing cost of the float.

[0029] Note that a primer resin layer may be provided between the core part 11 and the outer peripheral part 12, or between the outer peripheral part 12 and the protective part 13. In that case, the thickness of the primer resin layer is typically about 50 μm. Further, a top coat layer may be provided as an additional protective layer outside the protective part 13. Also, a colorant may be incorporated into the protective part or the top coat layer.

[0030] Next, a method for manufacturing the float 10 of the present embodiment will be described.

[0031] First, a used float 11 is prepared as the core part. When shells such as barnacles or seaweeds are attached to the surface of the used float 11, it is preferable to remove them by scraping the surface layer of the used float 11. Further, it is preferable to apply an adhesion aid (primer agent) for enhancing the adhesiveness between the cured rigid polyurethane foam and the core part 11 to the surface of the used float.

[0032] Referring to FIG. 2, a jig 15 for support is pierced into the central axis Z of the used float 11, and the position and orientation of the jig 15 are adjusted so that the used float 11 is positioned slightly above the lower mold and set so as to be located at substantially the center of the mold (foaming mold) 16. Note that the installation position of the jig 15 is not limited to this, and it may be pierced into the used float from a direction orthogonal to the central axis Z.

[0033] The mold 16 is provided with a plurality of inlets 17 for injecting the rigid polyurethane foam stock solution and a plurality of gas vents (not shown). Preferably, the mold 16 is sized to fit a new float. Preferably, a mold release agent such as silicone resin or silicone oil is applied to the inner surface of the mold 16. Alternatively, preferably, the inner surface is coated with a fluororesin. Alternatively, the used float 11 may be placed in a bag made of synthetic resin or the like and set, and the rigid polyurethane foam stock solution may be injected into the bag for foaming and curing so that the mold can be removed together with the bag. Note that the inlet may also be used as a gas vent. Also, the position and number of the inlets and gas vents may be appropriately changed according to the size and shape of the mold and the characteristics of the raw material.

[0034] Cover the lower mold with the upper mold or close the mold 16 by aligning the left and right molds split vertically. Using a urethane injection foaming machine, mix and stir polyol and polyisocyanate to prepare a raw solution of rigid polyurethane foam, and inject it into the mold 16 from the injection port 17.

[0035] The raw solution of rigid polyurethane foam is usually premixed with a catalyst, a foaming agent, a foam stabilizer, and other auxiliaries on the polyol side. Since the raw solution of rigid polyurethane foam for injection needs to flow into the gap between the mold 16 and the used float 11, it is preferable to use a material with a relatively long cream time of about 10 to 60 seconds and a rise time of about 100 to 300 seconds. The cream time is the time from mixing the raw materials until the liquid mixture starts to foam, and the rise time is the time from mixing the raw materials until foaming ends, that is, until the expansion of the foam stops. The raw solution of rigid polyurethane foam injected into the mold 16 fills the space between the used float 11 and the mold 16 while foaming and expanding, and then hardens.

[0036] When the rigid polyurethane foam has hardened, open the mold 16 and demold the molded body. The molded body consists of the used float 11 and the outer peripheral part 12 of the rigid polyurethane foam covering the whole of it. If air pockets are found on the surface of the molded body, it may be repaired by filling it with the raw solution of rigid polyurethane foam. Hold the molded body and step on the handle part of the jig 15 with your foot to remove the jig 15, and then inject the raw solution of rigid polyurethane foam into the hole left after removing the jig and seal it with the rigid polyurethane foam. Or, instead of sealing it at this stage, it may be sealed with a polyurea resin in the process of forming the protective part. If the jig 15 is inserted again when spraying the urea resin, it is more efficient.

[0037] When the used float 11 is put into a bag and set and demolded together with the bag, the bag may be broken and the molded body consisting of the used float 11 and the outer peripheral part 12 may be taken out, or the molded body may be left in the bag and the polyurea resin may be sprayed on the outer surface of the bag.

[0038] Onto the entire surface of the outer peripheral portion 12 of the demolded molded body, a polyurethane resin is sprayed and dried to form a protective portion 13. As the polyurethane resin, one used for construction at a construction site or the like for waterproofing can be used. Since the reaction between the polyisocyanate prepolymer as the main agent and the polyamine as the curing agent of the polyurethane resin is extremely fast, immediately before coating, they are generally collision-mixed and sprayed in a mist form. As a coating method, for example, the molded body is placed on a turntable with the central axis Z perpendicular, the polyurethane resin is sprayed onto the side surface while rotating the molded body, and after drying, the molded body is removed from the turntable and the urethane resin is sprayed onto both bottom surfaces of the cylinder and dried.

[0039] Note that for the formation of the protective portion 13, a primer resin may be applied to the surface of the outer peripheral portion 12, dried to form an underlayer of about 50 μm, and then the polyurethane resin is sprayed thereon and dried. By providing the underlayer of the primer resin, the adhesive force between the rigid polyurethane foam of the outer peripheral portion 12 and the polyurethane resin of the protective portion 13 is further improved. In addition, the underlayer of the primer resin can also be expected to have a function of preventing water intrusion in case the protective portion 13 is damaged accidentally.

[0040] According to this embodiment, since the used float can be reused, the number of floats to be discarded can be reduced.

[0041] As a second embodiment of the float of the present invention, a float manufactured as new is described. In this embodiment, mainly the parts different from the first embodiment are described, and detailed descriptions of the same parts are omitted.

[0042] Referring to FIG. 3, the float 20 of this embodiment is cylindrical, like the float 10 of the first embodiment, and has a core portion 21, an outer peripheral portion 22 covering the periphery of the core portion 21, and a protective portion 23 covering the surface of the outer peripheral portion 22. The size of the float 20 is the same as that of the float 10 of the first embodiment.

[0043] The core part 21 is a part for providing sufficient buoyancy to the float 20. The core part 21 contains polystyrene foam, preferably consists essentially of polystyrene foam, and more preferably consists only of polystyrene foam.

[0044] The outer peripheral part 22 covers the whole of the core part 21, absorbs impact, and attenuates the impact transmitted to the core part 21. The outer peripheral part 22 is made of rigid polyurethane foam. The rigid polyurethane foam includes isocyanurate foam.

[0045] The rigid polyurethane foam of this embodiment is spray rigid polyurethane foam. The density of the outer peripheral part 22 is not particularly limited, but the core density is usually 8 - 60 kg / m 3 and preferably 15 - 50 kg / m 3 and more preferably 18 - 35 kg / m 3 is more preferable.

[0046] The thickness of the outer peripheral part 22 is preferably uniform throughout and is 5 mm or more. If the thickness of the outer peripheral part 22 is 5 mm or more, it has sufficient durability and can sufficiently attenuate the impact from the outside. On the other hand, the thickness of the outer peripheral part 22 is preferably 30 mm or less, more preferably 15 mm or less. This is because the rigid polyurethane foam constituting the outer peripheral part 22 has a greater specific gravity than the polystyrene foam constituting the core part 21, so the greater the thickness of the outer peripheral part 22, the smaller the buoyancy of the float 20 when compared in the same volume.

[0047] The protection part 23 is made of polyurea resin, covers the whole of the outer peripheral part 22, and protects the inside from seawater. The protection part 23 is the same as the protection part 13 of the first embodiment, and all the explanations for the protection part 13 of the first embodiment are also applicable to the protection part 23 of this embodiment. Also, it is the same regarding that a layer of primer resin may be provided between the outer peripheral part 22 and the protection part 23, a top coat layer may be provided further outside the protection part 23, and a colorant may be blended in the protection part 23 or the top coat layer.

[0048] Next, a method for manufacturing the float 20 of the present embodiment will be described.

[0049] First, a core part 21 made of polystyrene foam is prepared. A hard polyurethane foam stock solution is sprayed onto the entire surface of the core part 21 using a urethane spray foaming machine. Specifically, for example, the core part 21 is placed on a turntable with the central axis vertical, and while rotating the core part 21, the hard polyurethane foam stock solution is sprayed onto the side surface to foam and cure. After that, the core part 21 is removed from the turntable, and the hard polyurethane foam stock solution is sprayed onto both bottom surfaces of the cylinder to foam and cure. As the hard polyurethane foam stock solution for spraying, it is preferable to use one with a short cream time of about 2 to 8 seconds and a rise time of about 8 to 30 seconds in order to prevent liquid dripping after spraying.

[0050] A polyurea resin is sprayed onto the entire surface of the outer peripheral part 22 and dried to form a protective part 23. The method for forming the protective part 23 is the same as that of the protective part 13 in the first embodiment. Also, preferably, forming an underlayer made of a primer resin on the surface of the outer peripheral part 22 and spraying a polyurea resin thereon is the same as that of the protective part 13 in the first embodiment.

[0051] As a third embodiment of the float of the present invention, a float in which waste materials of polystyrene foam are crushed and reused will be described. In this embodiment, mainly the parts different from the first embodiment will be described, and detailed descriptions of the same parts will be omitted.

[0052] Referring to FIG. 4, the float 30 of the present embodiment is cylindrical, similar to the float 10 of the first embodiment, and has a core part 31, an outer peripheral part 12 covering the periphery of the core part 31, and a protective part 13 covering the surface of the outer peripheral part 12. The outer peripheral part 12 and the protective part 13 are the same as those in the first embodiment. Also, the size of the float 30 is the same as that of the float 10 in the first embodiment.

[0053] The core part 31 is formed into a substantially cylindrical shape by packing pieces 34 of polystyrene foam into a bag 35. Instead of or in addition to the pieces of polystyrene foam, expanded polystyrene beads may be used. From the perspective of recycling, it is preferably to use pieces of waste polystyrene foam. The type of waste polystyrene foam is not particularly limited, and in addition to used floats, transportation boxes, cold storage boxes, heat insulation boxes, cushioning materials for packaging, food packaging materials, heat insulation boards, etc. can be used.

[0054] These waste materials are crushed and preferably made into crushed pieces with a diameter (the longest span) of about 1 to 150 mm and then packed into the bag 35. The opening of the bag 35 filled with the waste materials may be closed by tying it with a string or sticking an adhesive tape. The bag 35 is preferably a cylindrical or barrel-shaped one when expanded, so as to suppress the variation in the thickness of the outer peripheral part 12. The bag 35 only needs to be able to hold the pieces 34 of polystyrene foam during the manufacture of the float 30, and its material is not particularly limited. As the bag 35, those made of synthetic resin, for example, those made of polyolefin can be preferably used. Note that the bag 35 does not necessarily need to have water resistance. Also, the forming method of the core part 31 is not particularly limited. As long as the pieces 34 of polystyrene foam can be held during the manufacture of the float 30, in addition to packing the pieces 34 into a bag, methods such as packing the pieces 34 into a net, tying them with a string or an adhesive tape, or adhering them with an adhesive can also be used.

[0055] The manufacturing method of the float 30 of this embodiment is the same as that of the float 10 of the first embodiment, except that as the core part 31, instead of the used float (11 in FIG. 1), pieces of polystyrene foam or expanded polystyrene beads are formed and used.

[0056] In this embodiment, if waste polystyrene foam is used, the amount of waste materials to be discarded can be reduced. Also, when using a used float as the waste material, by crushing it and packing it into a bag, the core part 31 can be made into a neater cylindrical shape and the thickness of the outer peripheral part 12 can be made more uniform than when using it as the core part without crushing.

[0057] As a fourth embodiment of the float of the present invention, a float made of recycled crushed waste rigid polyurethane foam will be described. In this embodiment, differences from the third embodiment will be mainly described.

[0058] 5, the float 40 of this embodiment, like the float 30 of the third embodiment, is cylindrical and has a core portion 41, an outer peripheral portion 12 that covers the periphery of the core portion 41, and a protective portion 13 that covers the surface of the outer peripheral portion 12. The outer peripheral portion 12 and the protective portion 13 are the same as those in the third embodiment. The size of the float 40 is the same as that of the float 30 of the third embodiment.

[0059] The core 41 is formed by packing fragments 44 of rigid polyurethane foam into a bag 35 and molding them into a substantially cylindrical shape. From the viewpoint of recycling, it is preferable to use waste rigid polyurethane foam. The type of waste rigid polyurethane foam is not particularly limited, and it is possible to use scraps of insulation boards generated at construction sites, pieces of spray insulation material that are too thick, urethane powder collected by cleaning, and cushioning material. If these waste materials are already fragments of an appropriate size, they can be used as they are, and if they are too large, they are crushed into a size that is easy to mold and then packed into the bag 35. The bag 35 is the same as that of the third embodiment. The size of the fragments is preferably about 1 mm to 150 mm in diameter in the case of a lump shape, and preferably about 10 mm to 500 mm in length in the case of a long or flaky shape. The bag 35 is the same as that of the third embodiment. The molding method of the core 41 may be a method other than packing into a bag, as in the case of the core 31 of the third embodiment.

[0060] The manufacturing method of the float 40 of this embodiment is the same as that of the float 30 of the third embodiment, except that crushed waste material of rigid polyurethane foam is used as the core 41 by stuffing it into a bag 35 instead of fragments of polystyrene foam.

[0061] According to this embodiment, waste rigid polyurethane foam can be recycled, so the amount of waste material to be discarded can be reduced. EXAMPLES

[0062] As Example 1, the float 10 of the first embodiment was fabricated.

[0063] For the core part, a used float 11 made of polystyrene foam was used. Mollusks and seaweeds attached to the surface of the used float were removed, but resins, dents, and damaged parts attached to the surface were used as they were. The used float 11 was set, using the jig 15, at approximately the center of the mold 16 coated with a mold release agent such that the gap with the inner surface of the mold was 5 mm or more even at the narrowest part. The mold 16 was closed, and a hard polyurethane foam stock solution for injection (Kurashiki Boseki Co., Ltd., Claraform R for injection) was injected to form the outer peripheral part 12. The cream time of the stock solution was 20 seconds, the rise time was 180 seconds, and the core density of the hard polyurethane foam used was 28 kg / m 3 ³. After the hard polyurethane foam foamed and cured, the mold was split in half for demolding, and the hard polyurethane foam stock solution was further injected into the hole from which the jig 15 was removed, foamed, and cured. Then, the hard polyurethane foam protruding from the injection port 17 and the gas vent part was cut, and the surface of the outer peripheral part 12 was made flat. A primer resin base layer made of an aqueous epoxy resin was provided on the entire surface of the outer peripheral part 12, and a polyurea resin (pure polyurea) was sprayed thereon to a thickness of at least 1.5 mm or more to form the protection part 13. Thus, a float 10 having a cylindrical shape, a diameter of approximately 670 mm, and a length of approximately 1120 mm was fabricated. Note that it is preferable in terms of ease of use that the size of the completed float is the same as that when using an unused (new) buoy. For example, it is advisable to design the mold size so as to be the same size as the float 20 having a diameter of approximately 690 mm and a length of approximately 1190 mm fabricated in Example 2 described later.

[0064] The float 10 of Example 1 produced was floated in seawater, and a test was carried out for about 14 months. As a result, it was found that it was more difficult to sink compared to the existing floats. This result is considered to be due to the fact that the waterproof function was maintained for a long time by the protective part of the polyurea resin and the buoyancy did not decay. From this, by using the float of this example, there is a possibility that the number of floats used for aquaculture rafts can be reduced. In addition, there is a possibility that the float of this example can be used as a float for a heavier oar (offshore workplace) or the like.

Example

[0065] As Example 2, the float 20 of the above-described second embodiment was produced.

[0066] For the core part 21, a newly produced unused polystyrene foam block was used. The polystyrene foam block was cylindrical with a diameter of about 670 mm and a length of about 1170 mm. The entire surface of the core part 21 was sprayed with a sprayable rigid polyurethane foam stock solution (Kurashiki Boseki Co., Ltd., Claraform R for spray) using a collision-mixed high-pressure spray foaming machine, foamed, and cured to form an outer peripheral part 22 with a thickness of about 10 mm. The cream time of the stock solution was 4 seconds, the rise time was 10 seconds, and the core density of the rigid polyurethane foam used was 30 kg / m 3 ³. Surface irregularities peculiar to spray foaming were observed on the surface of the outer peripheral part 22. An underlayer of a primer resin made of an aqueous epoxy resin was provided on the entire surface of the outer peripheral part 22, and polyurea resin (pure polyurea) was sprayed thereon to a thickness of at least 1.5 mm or more to form a protective part 23. Thus, a float 20 having a cylindrical shape, a diameter of about 690 mm, and a length of about 1190 mm was produced.

[0067] Regarding the produced float 20 of Example 2, it was also floated in seawater and a test was carried out for about 18 months, and the same results as those of the float 10 of Example 1 were obtained.

[0068] The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the technical idea thereof.

[0069] For example, the materials of the protective parts 13 and 23 are not limited to polyurethane resin, and any material that can maintain water resistance for a long time and has excellent impact resistance is acceptable. Such materials include water-resistant fiber-reinforced resins and the like.

Explanation of Reference Signs

[0070] 10 Float 11 Used Float (Core Part) 12 Outer Periphery 13 Protective Part 15 Fixture 16 Mold (Foaming Mold) 17 Injection Port 20 Float 21 Core Part 22 Outer Periphery 23 Protective Part 30 Float 31 Core Part 34 Polystyrene Foam Fragments 35 Bag 40 Float 41 Core Part 44 Rigid Polyurethane Foam Fragments Z Central Axis of Used Float

Claims

1. a core including polystyrene foam; An outer peripheral portion covering the periphery of the core portion and made of a rigid polyurethane foam; A protective portion that covers a surface of the outer periphery; A float having

2. The protective part is made of a polyurethane resin.

2. The float of claim 1.

3. The core is a used float.

3. A float according to claim 1 or 2.

4. The outer periphery is made of injected rigid polyurethane foam; 4. The float of claim 3.

5. The core is made of molded polystyrene foam chips or expanded polystyrene beads.

3. A float according to claim 1 or 2.

6. A core made of rigid polyurethane foam fragments; An outer peripheral portion covering the periphery of the core portion and made of a rigid polyurethane foam; A protective portion that covers a surface of the outer periphery; A float having

7. The protective part is made of a polyurethane resin.

7. The float of claim 6.

8. A step of setting the used float in a foaming mold; A step of injecting a rigid polyurethane foam stock solution into the foaming mold, foaming and curing the liquid to form an outer periphery that covers the periphery of the used float; a step of demolding a molded body including the used float and the outer circumferential portion; providing a protective portion on the surface of the outer periphery; A method for manufacturing a float having the above structure.

9. A step of spraying a hard polyurethane foam concentrate onto the surface of a core portion made of polystyrene foam, foaming and curing the core portion to form an outer periphery that covers the periphery of the core portion; providing a protective portion on the surface of the outer periphery; A method for manufacturing a float having the above structure.

10. placing molded pieces of polystyrene foam or rigid polyurethane foam in a foaming mold; a step of injecting a rigid polyurethane foam stock solution into the foaming mold, foaming and curing the liquid, and forming an outer periphery that covers the periphery of the bag; a step of demolding a molded body consisting of the bag and the outer periphery; providing a protective portion on the surface of the outer periphery; A method for manufacturing a float having the above structure.

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