Pillar for nori cultivation and manufacturing method thereof

Abstract

A pillar (4) for laver cultivation, which is a pillar (4) for laver cultivation with a composite structure integrally bonded, having a core layer (1) made of a thermoplastic resin, an FRP layer (2) formed on the outer periphery of the core layer (1), and a coating layer (3) formed on the outer periphery of the FRP layer (2). The FRP layer (2) has an FRP inner layer (21) and an FRP outer layer (22). The FRP inner layer (21) has long fibrous carbon fibers (2a) as the main body of the reinforcing fibers and is longitudinally arranged and bonded to the outer periphery in the length direction of the core layer (1) through a matrix component. The FRP outer layer (22) has long fibrous glass fibers (2b) as the main body of the reinforcing fibers and is longitudinally arranged and bonded to the outer periphery of the FRP inner layer (21) through a matrix component.

Description

Technical Field

[0001] The present invention relates to a support for laver cultivation and a method for manufacturing the same. Background Art

[0002] In laver cultivation, bamboo or the like is used as a support in the sea, arranged at equal intervals, a net is provided between the supports, and cultivation is carried out on the net. In recent years, due to problems such as difficulty in obtaining bamboo materials, uneven thickness and length, and durability, a support made of fiber-reinforced synthetic resin (hereinafter referred to as "FRP") that can achieve uniform thickness is used.

[0003] As a method for manufacturing an FRP support for laver cultivation, there is known a so-called draw forming method (1) in which an uncured thermosetting resin composition is impregnated into reinforcing fibers, and while being drawn into a tubular shape by a heated annular mold and cured, it is continuously drawn, and a method (2) in which reinforcing fibers impregnated with an uncured thermosetting resin composition are traversed on a longitudinal mandrel having an outer diameter corresponding to the inner diameter of the tube and wound at a predetermined winding angle to form a tube layer and cured to form a tubular support.

[0004] Furthermore, an FRP support having a structure of a fiber-reinforced resin layer has been proposed, and the fiber-reinforced resin layer is formed by winding and laminating a sheet-like fiber-reinforced resin material using epoxy resin as a synthetic resin on a mandrel for forming a support (for example, refer to Patent Document 1).

[0005] However, in the draw forming method (1) using the mold, in order to draw a cured or semi-cured FRP support from the mold, a high drawing force is required due to the frictional resistance between the mold and the device is enlarged, and the energy consumption and equipment cost have to be increased.

[0006] On the other hand, in the method for manufacturing an FRP support described in Patent Document 1, since it is formed by winding and laminating a sheet-like fiber-reinforced resin material on a mandrel for forming a support, due to the limitation of the length of the mandrel, etc., a support with a total length of about 6 m becomes the maximum length. However, as the water depth of a fishing ground for laver cultivation, there are also places with a depth of about 12 m, and it cannot be adopted as a manufacturing method for obtaining a continuously long support.

[0007] In addition, for the FRP support for laver cultivation, for the purpose of preventing a part of the FRP layer from peeling off and piercing fingers and causing injury during operation, preventing hydrolysis of the FRP layer when erected and used in seawater, preventing weathering deterioration of the FRP layer, etc., it is preferable that the outer surface of the FRP layer is coated with a thermoplastic resin or the like. Furthermore, from the viewpoint of preventing hydrolysis of the FRP layer when erected and used in seawater, it is desirable that the inner surface of the FRP layer is also coated.

[0008] The applicant has marketed the FRP column with such a function, having a three-layer structure of a thermoplastic resin core layer / FRP layer / thermoplastic resin coating layer and an outer diameter of 35 mm to 57 mm, under the trade name: "Compose (registered trademark)" as a column for seaweed cultivation. Due to its high operability, durability, advantages compared with bamboo, etc., it has received a high practical evaluation from seaweed farmers. The core layer is formed of a thermoplastic resin, the FRP layer bonds long fibrous glass fibers to the outer periphery of the core layer using a matrix resin, and a thermoplastic resin coating layer is provided on the outer periphery of the FRP layer.

[0009] However, even for the FRP column for seaweed cultivation with the above three-layer structure, the following problems can be cited.

[0010] (i) The installation of the column for seaweed cultivation is carried out by manual operation. Therefore, if it is heavy, it is difficult to carry out the operation.

[0011] (ii) When grasping the column for seaweed cultivation by hand, if it is thick, it is difficult to grasp and the operation is difficult. On the other hand, if the column is simply made thinner, the rigidity in ordinary FRP is reduced, and it is difficult to stand on its own in the sea, and the net is likely to flow.

[0012] (iii) Usually, mechanical materials such as cultivation columns are transported to the farm by ship. However, if the columns are bulky, the transportation frequency increases and the transportation operation takes more time.

[0013] (iv) To solve the above problems, it is considered to use carbon fiber as the FRP material. However, when only making an FRP column of carbon fiber, the cost becomes very high and it lacks practicality.

[0014] On the other hand, Patent Document 2 discloses a fiber-reinforced thermoplastic resin composition comprising a thermoplastic resin, 5 to 25 parts by weight of carbon fiber and 20 to 70 parts by weight of glass fiber based on 100 parts by weight of the thermoplastic resin, and the total of the carbon fiber and the glass fiber is 40 to 75 parts by weight based on 100 parts by weight of the thermoplastic resin, and proposes the application of pipe members and the like to connecting members such as T-shaped and L-shaped members. However, in the specific examples of the invention described in Patent Document 2, when producing a mixture containing polyethylene terephthalate resin as the thermoplastic resin, 7.7 parts by weight of carbon fiber and 46.2 parts by weight of glass fiber (average diameter 5 μm to 20 μm, average fiber length 100 μm to 500 μm) based on 100 parts by weight of the PET resin and the total fiber amount being 53.9 parts by weight, a pellet-like compounded material in which only carbon fiber (average diameter 1 μm to 10 μm, average fiber length 100 μm to 500 μm) is compounded in the PET resin, a pellet-like compounded material in which only glass fiber is compounded in the PET resin, and a pellet-like compounded material composed of the PET resin are respectively produced, and a mixture of the predetermined pellet-like compounded materials is obtained. Then, the mixture is injection-molded to obtain a molded article. However, the invention described in Patent Document 2 cannot be adopted in a technical method of ensuring bending strength and bending rigidity by using continuous long fiber-like reinforcing fibers such as the pillars for seaweed cultivation.

[0015] Prior Art Documents

[0016] Patent Documents

[0017] Patent Document 1: Japanese Patent Application Laid-Open No. 2007-259838

[0018] Patent Document 2: Japanese Patent Application Laid-Open No. 2019-214694 Summary of the Invention

[0019] Problems to be Solved by the Invention

[0020] The applicant has intensively studied the above problems (i) to (iv), that is, a seaweed cultivation support made of FRP that has excellent operability through manual work, can achieve both light weight and high rigidity, is relatively inexpensive and practical, and was previously applied for as Japanese Patent Application No. 2019-063246 (filed on March 28, 2019). In the invention of this application, carbon fibers are arranged on the outer peripheral side of the FRP layer formed on the outer periphery of the core layer composed of a thermoplastic resin, and glass fibers are arranged on the inner peripheral side. Arranging carbon fibers on the outer peripheral side can reduce the outer diameter and ensure rigidity, which is effective from the perspective of improving operability and workability. However, when arranging carbon fiber bundles, whose number is naturally limited due to material cost constraints, on the outer peripheral side of the FRP layer, it is difficult to arrange the carbon fiber bundles at uniform intervals in the circumferential direction, and thus uneven distribution of carbon fibers can be seen. Therefore, when bending stress is applied to the support, the bending strength varies greatly depending on the position (orientation) in the circumferential direction where the stress is applied, and there are improvement points in terms of usage functions such as the difficulty of erecting the support in the sea and the deviation in the displacement amount between each support caused by waves in a row of seaweed cultivation supports when using a seaweed net in the sea. On the other hand, to solve this improvement point, it is also possible to arrange them uniformly in the circumferential direction by reducing the fineness (average fiber diameter) of the carbon fibers and increasing the number of carbon fibers used. However, compared with carbon fibers with a large fineness, carbon fibers with a small fineness have a higher price per unit weight, so an increase in the product price of the seaweed cultivation support becomes a problem.

[0021] Therefore, the inventors of the present invention have intensively studied the uniform arrangement of carbon fibers in the circumferential direction in order to achieve uniformization of the bending strength based on the position (orientation) in the circumferential direction, and thus completed the present invention.

[0022] Solutions for Solving the Problems

[0023] That is, the present invention provides the following inventions [1] to [4].

[0024] 〔1〕A pillar for seaweed cultivation, characterized in that it is a pillar for seaweed cultivation having a composite structure in which a core layer made of a thermoplastic resin, an FRP layer formed on the outer periphery of the core layer, and a coating layer formed on the outer periphery of the FRP layer are integrally bonded. At least the outer peripheral surface of the core layer is made of a thermoplastic resin having chemical affinity with the thermosetting resin as the matrix component constituting the FRP layer. The FRP layer has an FRP inner layer and an FRP outer layer. The FRP inner layer is bonded to the outer periphery in the longitudinal direction of the core layer through a matrix component with long fibrous carbon fibers as the main body of the reinforcing fibers arranged longitudinally. The FRP outer layer is bonded to the outer periphery of the FRP inner layer through a matrix component with long fibrous glass fibers as the main body of the reinforcing fibers arranged longitudinally. The cross-sectional area ratio of the glass fiber to the carbon fiber in the FRP layer is 60:40 to 90:10. At least the inner peripheral surface of the coating layer is made of a thermoplastic resin having chemical affinity with the thermosetting resin as the matrix component constituting the FRP layer.

[0025] 〔2〕The pillar for seaweed cultivation according to the above-mentioned 〔1〕, wherein, in the FRP inner layer, a plurality of carbon fiber bundles are arranged on the circumference in a centrosymmetric manner, and the carbon fiber bundles are arranged adjacent to each other.

[0026] 〔3〕The pillar for seaweed cultivation according to the above-mentioned 〔1〕, wherein the cross-sectional area ratio of the glass fiber to the carbon fiber in the FRP layer is 70:30 to 80:20.

[0027] 〔4〕A manufacturing method of the pillar for seaweed cultivation according to any one of the above-mentioned 〔1〕 to 〔3〕, characterized in that it has the following steps (i) to (vii):

[0028] (i) Prepare the required number of carbon fiber bundles and glass fiber bundles as long fibrous reinforcing fibers, respectively penetrate the carbon fiber bundles and glass fiber bundles through the predetermined guide holes of the collective guide, and then arrange them in parallel, and guide them through the impregnation operation guide of the impregnation tank, the drawing die for longitudinally arranging them in a predetermined configuration on the outer periphery of the core layer, the melt extruder for the coating layer, and the production line, and prepare them in a manner capable of pulling the reinforcing fiber bundles.

[0029] (ii) Inject a liquid curable resin composition containing a thermosetting resin and a thermosetting agent into the impregnation tank.

[0030] (iii) Continuously extrude the thermoplastic resin forming the core layer from the core melt extruder into a circular tube of a predetermined size, and continuously draw it through the production line to manufacture the core layer.

[0031] (iv) While pulling the reinforcing fiber bundle prepared in (i) above, lower the impregnation operation guide member into the impregnation tank to impregnate the reinforcing fiber bundle with the curable resin composition, longitudinally arrange it on the outer periphery of the core layer traveling in the center of the hole portion of the drawing die, and gradually draw the remaining resin composition using the drawing die to obtain an uncured tubular product having the reinforcing fiber bundle longitudinally arranged on the core layer;

[0032] (v) Pass the uncured tubular product through the crosshead of the melt extruder for the coating layer, extrude and coat it in a circular shape with the thermoplastic resin for the coating layer, and then cool the coating layer to obtain an uncured tubular product with a coating layer;

[0033] (vi) Introduce the uncured tubular product with a coating layer into a heat curing tank to thermally cure the uncured thermosetting resin composition inside, and pull out a tubular product with a composite structure in which the core layer, FRP layer, and coating layer are integrally bonded; and

[0034] (vii) Cut the pulled tubular product into a predetermined length as a support for seaweed cultivation.

[0035] Effects of the Invention

[0036] The support for seaweed cultivation of the present invention is a support for seaweed cultivation having a composite structure in which a core layer made of a thermoplastic resin, an FRP layer formed on the outer periphery of the core layer, and a coating layer formed on the outer periphery of the FRP layer are integrally bonded. The FRP layer has an FRP inner layer and an FRP outer layer. The FRP inner layer uses long fiber-like carbon fibers as reinforcing fibers on the outer periphery in the length direction of the core layer, and the FRP outer layer uses long fiber-like glass fibers as reinforcing fibers on the outer periphery of the FRP inner layer. The cross-sectional area ratio of the glass fiber to the carbon fiber is set within a predetermined range. Therefore, a support for seaweed cultivation can be provided that can eliminate the deviation of the bending strength caused by the non-uniform circumferential arrangement of the carbon fibers. And, compared with the conventional FRP layer composed only of glass fibers, the support for seaweed cultivation of the present invention can achieve high rigidity and light weight under the same outer diameter. In addition, if the rigidity is to be set to the same level as the conventional one, the outer diameter can be made thinner, and weight reduction and improvement in operability due to the thinner diameter can be achieved.

[0037] In addition, the manufacturing method of the support for seaweed cultivation of the present invention can manufacture the support for seaweed cultivation of the present invention with excellent operability in manual work, capable of achieving both light weight and high rigidity, relatively inexpensive and practical, with good reproducibility, stability and economy. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 It is a schematic cross-sectional view of the support for seaweed cultivation of Example 2 of the present invention.

[0039] Figure 2 It is a schematic cross-sectional view of the seaweed cultivation support of Comparative Example 2 of the present invention.

[0040] Figure 3 It is an explanatory view of an example of a production line used in the manufacturing method of the seaweed cultivation support of the present invention. Detailed implementation manners

[0041] Hereinafter, preferred implementation manners of the present invention will be described. It should be noted that each implementation manner shown in the attached drawings is an example of a representative implementation manner for explaining the present invention, and dimensions and the like are not suitable for the actual object, and the scope of the present invention is not narrowly interpreted by these drawings.

[0042] The seaweed cultivation support of the present invention is characterized in that it is a seaweed cultivation support having a composite structure in which a core layer made of a thermoplastic resin, an FRP layer formed on the outer periphery of the core layer, and a coating layer formed on the outer periphery of the FRP layer are integrally bonded. At least the outer peripheral surface of the core layer is made of a thermoplastic resin having chemical affinity with the thermosetting resin as the matrix component constituting the FRP layer. The FRP layer has an FRP inner layer and an FRP outer layer. The FRP inner layer is bonded to the outer periphery in the longitudinal direction of the core layer through the matrix component with long fibrous carbon fibers as the main body of the reinforcing fibers arranged longitudinally. The FRP outer layer is bonded to the outer periphery of the FRP inner layer through the matrix component with long fibrous glass fibers as the main body of the reinforcing fibers arranged longitudinally. The cross-sectional area ratio of the glass fiber to the carbon fiber in the FRP layer is 60:40 to 90:10. At least the inner peripheral surface of the coating layer is made of a thermoplastic resin having chemical affinity with the thermosetting resin as the matrix component constituting the FRP layer.

[0043] Regarding the seaweed cultivation support 4 of the present invention, as an example of the layer structure of a cross-section orthogonal to the longitudinal direction is shown in Figure 1 As such, it is formed by a core layer 1, an FRP inner layer 21, and a coating layer 3. The core layer 1 is made of a thermoplastic resin. The FRP inner layer 21 is formed by curing a thermosetting resin 2c as a matrix component by bonding carbon fiber bundles (usually called "carbon fiber tows".) 2a and glass fiber bundles (usually called "glass fiber yarn bundles".) 2b with a predetermined cross-sectional area ratio as reinforcing fibers. The coating layer 3 is made of a thermoplastic resin and is formed on the outer periphery of the FRP outer layer 22.

[0044] For the seaweed cultivation pillar 4 of the present invention, considering the rigidity required to support the seaweed net and withstand the waves when erected in the sea, the outer diameter is approximately 35 mm to 60 mm. The seaweed cultivation pillar 4 with this outer diameter is used as the main body erected on the seabed. It has a conical front end at the seabed side, and at the sea surface side, it is connected via a joint to a front end called an antenna with an outer diameter of 10 mm to 20 mm and a length of 1 m to 2.0 m, which is used to ensure the retention of the net ropes during high tide. The present invention is an invention of the main body of the above-mentioned seaweed cultivation pillar, and its length is approximately 4 m to 15 m according to the relationship with the sea depth of the fishing ground.

[0045] (Thermoplastic resin of the core layer)

[0046] In connection with the manufacturing method of the seaweed cultivation pillar of the present invention, the core layer is manufactured by melt-extruding a thermoplastic resin. And, at least the outer peripheral surface of this core layer needs to be closely adhered (bonded) to the interface of the FRP inner layer through chemical affinity. Therefore, the thermoplastic resin used in the core layer is selected from thermoplastic resins having chemical affinity with the thermosetting resin as the matrix component constituting the FRP layer. For example, ABS (acrylonitrile-butadiene-styrene resin), AES (acrylonitrile-ethylene-propylene rubber-styrene resin), AS (acrylonitrile-styrene resin), AAS (acrylonitrile-acrylic acid-styrene resin), PS (polystyrene resin), PC (polycarbonate resin), PPE (modified polyphenylene ether resin; graft copolymer of polyphenylene and polystyrene), polyvinyl chloride resin, etc. can be cited.

[0047] The inner diameter of the core layer is approximately 30.5 mm to 50.5 mm, and the layer thickness is approximately 1.5 mm to 3.0 mm. The core layer only needs to have chemical affinity with the thermosetting resin as the matrix component constituting the FRP layer at least on the outer peripheral surface, and it can also be formed by multi-layer extrusion of the above-mentioned thermoplastic resin having compatibility with the matrix component, a thermoplastic resin copolymer modified to improve the adhesiveness, etc. only on the outer peripheral surface.

[0048] 〔FRP layer〕

[0049] The FRP layer of the seaweed cultivation pillar of the present invention has an FRP inner layer and an FRP outer layer. The FRP inner layer has long fibrous carbon fibers as the main body of the reinforcing fibers and is longitudinally arranged and bonded to the outer periphery in the length direction of the core layer through the matrix component. The FRP outer layer has long fibrous glass fibers as the main body of the reinforcing fibers and is longitudinally arranged and bonded to the outer periphery of the FRP inner layer through the matrix component. The cross-sectional area ratio of the glass fibers to the carbon fibers in the FRP layer is 60:40 to 90:10.

[0050] In connection with the manufacturing method of the seaweed cultivation pillar of the present invention described above, the FRP layer first undergoes step (iv) and then is transferred to the next step. In step (iv), a longitudinally elongated carbon fiber bundle and a glass fiber bundle, which are aggregated as reinforcing fibers at a predetermined cross-sectional area ratio, are impregnated with a curable resin composition. They are longitudinally arranged on the outer periphery of a continuously extruded core layer, and the remaining resin composition is gradually drawn by a drawing die to form an uncured tubular object composed of two layers: an FRP inner layer with carbon fiber as the reinforcing fiber on the side in contact with the core layer and an FRP outer layer with glass fiber longitudinally arranged on its outer peripheral side as the reinforcing fiber.

[0051] Next, it undergoes step (v) (melt coating step) and is formed through step (vi). In this step (v), the uncured tubular object is passed through the crosshead of a melt extruder for the coating layer, and after being extruded and coated in a circular shape with a thermoplastic resin for the coating layer, the coating layer is cooled to obtain an uncured tubular object with a coating layer. In this step (vi), the uncured tubular object with a coating layer is introduced into a heat curing tank, and the uncured thermosetting resin composition composed of two layers inside is heat cured, and a tubular object with a composite structure in which the core layer, the FRP layer composed of the FRP inner layer and the FRP outer layer, and the coating layer are closely integrated is pulled out.

[0052] (Cross-sectional area ratio of reinforcing fiber and FRP layer)

[0053] In the present invention, for the reinforcing fiber, the FRP inner layer uses carbon fiber as the main body of the reinforcing fiber, and the FRP outer layer uses glass fiber as the main body. In the present invention, "as the main body of the reinforcing fiber" means that the situation of mixing other functional fibers, etc. in the carbon fiber or glass fiber according to the purpose within the range that does not damage the reinforcing function of the carbon fiber or glass fiber is not excluded. The reinforcing fiber constituting the FRP layer can be a fiber bundle-shaped reinforcing fiber formed by bundling 1000 to 50000 single fibers with an average diameter of 5 μm to 10 μm. The specific strength of the reinforcing fiber is preferably 1000 kN·m / kg or more, and the specific elastic modulus is preferably 20000 kN·m / kg or more.

[0054] Regarding the reinforcing fibers of long fibers used in the FRP layer composed of an FRP inner layer and an FRP outer layer of the pillar for laver cultivation of the present invention, carbon fiber is used for the FRP inner layer, and glass fiber is used for the FRP outer layer, and the usage ratio of glass fiber is increased. The cross-sectional area ratio of glass fiber to carbon fiber in the FRP layer cross-section in the longitudinal direction of the pillar for laver cultivation is 60:40 to 90:10, more preferably 65:35 to 85:15, and further preferably 70:30 to 80:20. If the cross-sectional area ratio of glass fiber to carbon fiber in the FRP layer cross-section is 60:40 to 90:10, that is, the carbon fiber is 40% or less by area ratio, a cheap pillar for laver cultivation that can tolerate the increase in raw material cost brought by carbon fiber and can exhibit the improvement effects of bending strength, bending rigidity, light weight, and workability can be provided. If it is 90:10, that is, the carbon fiber is 10% or more by area ratio, the improvement effects of bending strength, bending rigidity, light weight, and workability brought by carbon fiber can be exhibited, and a pillar for laver cultivation that can easily and evenly arrange carbon fibers on the circumference of the FRP inner layer and has a small deviation in bending strength can be provided.

[0055] If the cross-sectional area ratio of glass fiber to carbon fiber in the FRP layer cross-section is set to 70:30 to 80:20, a cheaper pillar for laver cultivation with sufficient bending strength and bending rigidity in practical use can be provided.

[0056] It should be noted that the cross-sectional area ratio of the reinforcing fibers in the FRP layer cross-section can be obtained by calculating the cross-sectional areas of the glass fiber and carbon fiber used in the FRP layer from their respective usage numbers, finenesses, and densities.

[0057] Furthermore, the carbon fiber used in the FRP inner layer is preferably arranged on the outer circumference of the core layer, and a plurality of carbon fiber bundles are arranged on the circumference in a centrosymmetric manner with respect to the center axis, and the carbon fiber bundles are arranged adjacent to each other. "Adjacent" means that, as Figure 1 shown in the schematic cross-sectional view in [reference], the carbon fiber bundles are adjacent to each other and preferably form a state of a circumferential layer.

[0058] In addition, by symmetrically arranging the carbon fiber (bundle) with respect to the center of the pillar in the FRP inner layer at a substantially same central angle θ, the high elastic modulus carbon fiber is evenly located on the circumference, so there will be no drawbacks such as the pillar being biased in the longitudinal direction or anisotropy occurring during use, and the straightness and straightness recovery required in practical use can be maintained.

[0059] It should be noted that from the viewpoints of reducing the amount of carbon fiber and maintaining strength, the flatness ratio of the carbon fiber bundle is preferably 0.33 to 0.83, and the aspect ratio is preferably 3:2 to 6:1.

[0060] Examples of the glass fiber, which is the reinforcing fiber of the FRP outer layer that can be used as the pillar for laver cultivation in the present invention, include E glass fiber (for electrical use), C glass fiber (for corrosion resistance), S glass fiber, T glass fiber, etc. As the form of the fiber, a glass yarn bundle formed by bundling glass fibers (filaments) is suitable for use in the FRP layer. Examples of the glass fiber that can be used include products named RS110QL-533AH, RS220RL-510AH, RS440RR-531AH manufactured by Nitto Boseki Co., Ltd.; products named ERS2200-820 / LX, ERS4400-820 / LX manufactured by Central Glass Co., Ltd.; products named ER469-4400, ER469-2200 manufactured by Chongqing International Composite Co., Ltd. (CPIC); and products named EDR17-1150-386T, EDR22-2200-312T manufactured by Jushi Group Co., Ltd., etc.

[0061] Examples of the carbon fiber, which is the reinforcing fiber of the FRP inner layer that can be used as the pillar for laver cultivation in the present invention, include PAN-based carbon fibers made from polyacrylonitrile (PAN) fibers, pitch-based carbon fibers made from petroleum tar and petroleum asphalt, cellulose-based carbon fibers made from viscose rayon, cellulose acetate, etc., vapor-grown carbon fibers made from hydrocarbons, etc., and their graphitized fibers. Among these carbon fibers, PAN-based carbon fibers are preferably used in consideration of the excellent balance between strength and elastic modulus. Examples of the carbon fiber that can be obtained and used include products named TRW40 50L 3750tex manufactured by Mitsubishi Chemical Corporation, and products named PX35(50K) manufactured by Zoltek Companies, Inc., etc.

[0062] (Matrix component)

[0063] The matrix components of the FRP inner layer and outer layer of the pillar for laver cultivation in the present invention are formed by curing a thermosetting resin composition. Examples of the thermosetting resin include unsaturated polyester resins, unsaturated carboxylic acid-modified vinyl ester resins, epoxy resins, etc.

[0064] Among these, for thermosetting properties, unsaturated polyester resins are preferably used from the viewpoints of versatility, economy, etc.

[0065] In addition, the unsaturated polyester resin can be selected to be an unsaturated polyester resin containing styrene as a monomer component and having chemical affinity with the thermoplastic resins of the core layer and the coating layer, or an unsaturated polyester resin that integrally bonds these three layers after thermosetting.

[0066] The thermosetting resin is prepared as a thermosetting resin composition in which a thermosetting catalyst (curing agent), calcium carbonate for viscosity adjustment, etc. are added and mixed, and a thixotropic agent such as Aerosil (trade name) as ultrafine silica is added and mixed as needed. It is impregnated into the reinforcing fiber and finally thermally cured to form the matrix component.

[0067] (Coating layer)

[0068] The coating layer of the pillar for seaweed cultivation of the present invention can also be configured such that the thermoplastic resin constituting at least the inner peripheral surface of the coating layer is selected from thermoplastic resins containing styrene as a component, and the thermosetting resin constituting the matrix component of the FRP layer is in contact with an unsaturated polyester resin containing styrene monomer as a monomer component in an uncured state. Thus, after the thermosetting resin is cured by chemical affinity, the FRP layer / coating layer are bonded and integrated with each other.

[0069] [Manufacturing method of pillar for seaweed cultivation]

[0070] The manufacturing method of the pillar for seaweed cultivation of the present invention is characterized by including the following steps (i) to (vii). Hereinafter, each step will be described in turn.

[0071] (i) Preparation step of reinforcing fiber

[0072] This step is as follows Figure 3 shown: As the fibrous reinforcing fiber, the required number of carbon fiber bundles 2a for the FRP inner layer are prepared on the creel 12, and the glass fiber bundles 2b for the FRP outer layer are prepared on the creel 13. Considering the configuration in the FRP layer, an impregnation tank 11a is prepared for the carbon fiber for the FRP inner layer, and an impregnation tank 11b is prepared for the glass fiber for the FRP outer layer. The carbon fiber bundle and the glass fiber bundle are respectively passed through the predetermined guide holes (not shown) of their respective collective guides (panels) (not shown), and further, they are arranged in parallel and passed through the impregnation operation guides (not shown) of the impregnation tanks 11a and 11b, and they are passed through the drawing die 7, the coating layer melting extruder 8 for longitudinally arranging them in a predetermined configuration on the outer periphery of the core layer 1 when they are stably traveling and drawing out the remaining thermosetting resin, and the production line thereafter (downstream side), and are prepared in a manner that can be drawn. It should be noted that in the stage of this preparation step of the reinforcing fiber, the extrusion of the core layer 1, the resin impregnation operation of impregnating the resin into the reinforcing fiber bundle in the thermosetting resin impregnation tank 11, the drawing forming, and the coating using the coating layer melting extruder 8 are not performed, but the reinforcing fiber can be prepared by being arranged on the production line during stable operation.

[0073] (ii) Preparation step of curable resin composition

[0074] This process is as follows: A liquid curable resin composition containing a thermosetting resin and a thermal curing agent is injected into impregnation tanks 11a and 11b. As the thermosetting resin, it is selected and used from the aforementioned thermosetting resins. A predetermined amount of a thermal curing catalyst (curing agent), calcium carbonate for viscosity adjustment, etc., and a thixotropic agent such as Aerosil (trade name) as ultrafine silica are added as needed to the thermosetting resin and stirred and mixed. The resulting substance is used as the thermosetting resin composition, which is stirred and mixed and then injected into impregnation tanks 11a and 11b. The stirring and mixing can be carried out in advance, or after transferring to the stable production state, a predetermined amount of each substance constituting the thermosetting resin composition is metered, and while being mixed with a mixing device, it is continuously injected into the impregnation tank corresponding to the consumption amount of the thermosetting resin composition.

[0075] (iii) Core layer manufacturing process

[0076] This process is as follows: The thermoplastic resin forming the core layer 1 is continuously extruded into a circular tube of a predetermined size from the core melt extruder 5 while restricting the inner diameter with a mandrel or the outer diameter with a die, cooled in the cooling tank 6, and continuously pulled through the subsequent production line to manufacture the core layer. Through this process, the uncured thermosetting resin composition impregnated with long fiber reinforcing fibers afterwards is drawn into a predetermined outer diameter and can be coated with the coating layer melt extruder 8.

[0077] (iv) Manufacturing process of uncured tubular part

[0078] This process is as follows: While pulling the reinforcing fibers prepared in the aforementioned (i), the impregnation operation guide member (not shown) is lowered toward the impregnation tanks 11a and 11b, the curable resin composition is impregnated into the reinforcing fiber bundle, and it is longitudinally arranged on the outer periphery of the core layer 1 traveling in the center of the hole portion of the drawing die 7. The remaining resin is gradually drawn with the drawing die to obtain an uncured tubular object 14 in which carbon fibers are longitudinally arranged as reinforcing fibers on the outer periphery of the core layer and glass fibers are further longitudinally arranged as reinforcing fibers on the outer periphery of the carbon fibers.

[0079] (v) Melting coating and cooling process of uncured tubular object

[0080] This process is the following melting coating and cooling process: The aforementioned uncured tubular object 14 is passed through the crosshead of the coating layer melt extruder 8, and after being extruded and coated in a circular shape with the thermoplastic resin for the coating layer, the coating layer is immediately cooled and cured in the cooling tank 9 to obtain an uncured tubular object 15 with a coating layer.

[0081] (vi) Thermal curing and pulling process of uncured tubular object with coating layer

[0082] This process is as follows: The uncured tubular object 15 with a coating layer is introduced into the thermal curing tank 10 to thermally cure the uncured thermosetting resin composition inside, and a tubular object (composite tubular object) 16 with a composite structure in which the core layer 1, the FRP inner layer 21, the FRP outer layer 22, and the coating layer 3 are closely integrated is pulled out by a rubber belt type or caterpillar type pulling machine (not shown), etc.

[0083] (vii) A process of cutting the composite tubular object into a predetermined length

[0084] The pulled composite tubular object 16 has high rigidity and is difficult to wind around a roller or the like, so it is cut into a predetermined length according to the length during use.

[0085] (Other processes)

[0086] Since it is not the main part of the present invention, detailed description is omitted. However, the cut composite tubular object obtained as described above is used as the main body of the seaweed cultivation support. A conical front-end member (not shown) for piercing into the seabed is connected to one end side, and a composite tubular object with a small diameter and a predetermined length is connected as a front-end member (so-called "antenna") via a connecting member at the other end side, thereby providing a seaweed cultivation support. It is effective to perform the connection of these members on a production line continuous with the cutting process.

[0087] Examples

[0088] Hereinafter, the present invention will be described through examples and comparative examples, but the present invention is not limited to these examples. Hereinafter, description will also be made with reference to the drawings.

[0089] Example 1

[0090] Using the materials shown below, a composite tubular object for the main body of the seaweed cultivation support was produced.

[0091] 〔Material composition〕

[0092] (Thermoplastic resin for the core layer)

[0093] · ABS resin: manufactured by Toray Industries, Inc., TOYOLAC (registered trademark) 600 - 309N

[0094] (Thermosetting resin composition)

[0095] · 100 parts by mass of unsaturated polyester resin: manufactured by Nippon U-Pica Co., Ltd., U-Pica (registered trademark) 3464

[0096] · 10 parts by mass of calcium carbonate: manufactured by Shimizu Kogyo Co., Ltd., LW350

[0097] · Organic peroxide - 1, 4 parts by mass: manufactured by Chemische Fabrik Lamberti GmbH, Kayaester (registered trademark) O - 50E

[0098] · Organic peroxide - 2, 1 part by mass: manufactured by Chemische Fabrik Lamberti GmbH, Trigonox (registered trademark) 117

[0099] (Reinforcing fiber)

[0100] · 16 carbon fiber tows: manufactured by Mitsubishi Chemical Corporation, PYROFIL (registered trademark), TRW4050L

[0101] · 114 glass fiber yarn bundles: manufactured by Nitto Boseki Co., Ltd., RS220RL - 510AH (2200 tex)

[0102] (Thermoplastic resin for coating)

[0103] · ABS resin: manufactured by Toray Industries, Inc., TOYOLAC (registered trademark) 600 - 309N, FB - 1682 (black color masterbatch)

[0104] (Preparation of uncured thermosetting resin composition)

[0105] As the uncured thermosetting resin composition impregnated into the reinforcing fibers constituting the inner and outer layers of the FRP, the above - mentioned unsaturated polyester resin, organic peroxide, and calcium carbonate as a filler are respectively metered in a preparation tank equipped with a stirring device, stirred and mixed, and then injected into the impregnation tanks 11a and 11b.

[0106] As shown in Figure 3 the above - mentioned ABS resin is continuously extruded from the core - type melt extruder 5 in the form of a tube with an outer diameter of 37.6 mm and an inner diameter of 33.6 mm as the core layer 1.

[0107] The FRP layer formed on the outer peripheral side of the core is formed into an inner layer and an outer layer based on a two - stage drawing method of the reinforcing fibers. The FRP inner layer uses carbon fibers. In order to be disposed on the inner peripheral side of the FRP layer, the carbon fiber tows disposed on the creel 12 (detailed illustration omitted) are bundled, and the thermosetting resin composition in the impregnation tank 11a is impregnated, and it is gradually introduced into a plurality of drawing die devices 7 so that the fiber density [fiber volume / (fiber volume + thermosetting resin volume)] when only carbon fibers are disposed becomes 48% by volume. The FRP outer layer uses glass fibers. In order to be disposed on the outer peripheral side of the FRP layer, the glass fiber bundles disposed on the creel 13 (detailed illustration omitted) are bundled, and the thermosetting resin composition in the impregnation tank 11b is impregnated, and it is introduced along the outer peripheral side of the already drawn carbon fibers into a plurality of drawing die devices 7 whose inner diameters gradually finally converge to the outer diameter of the FRP layer, 41.5 mm.

[0108] That is, a layer formed of carbon fiber and a curable resin composition impregnated in the carbon fiber is longitudinally arranged on the outer periphery of the core layer, glass fiber disposed on the outer periphery of the layer, and a curable resin composition impregnated in the glass fiber are used. The final drawing die is used for forming to produce an uncured tubular object 14 with an outer diameter of 41.5 mm. Next, it is guided to the cross head of the coating layer melting extruder 8 to obtain an uncured tubular object 15 with a coating layer.

[0109] Next, the uncured tubular object 15 with a coating layer is guided to a thermal curing tank 10 using hot water as a heat medium to thermally cure the uncured FRP layer inside, and it is cooled in a cooling water tank (not shown) to obtain a composite tubular object 16 having a three-layer structure composed of a core layer, an FRP layer, and a coating layer. The FRP layer is composed of an inner layer and an outer layer, and it is cut into a length of 10 m using a cutting device (not shown). The outer diameter of the obtained pillar (composite tubular object) is 42.8 mm, and the thickness of the FRP layer is 2.0 mm. The cross-sectional area ratio of glass fiber / carbon fiber, flexural strength, etc. of the obtained pillar are summarized in Table 1.

[0110] Example 2

[0111] In Example 1, a core with an outer diameter of 41.0 mm and an inner diameter of 37.0 mm was extruded into a tube shape, and it was changed to 16 carbon fiber tows and 150 glass fiber tows. The outer diameter of the FRP layer was set to 45.1 mm, the thickness of the FRP layer was set to 2.1 mm, and the outer diameter of the coating layer was set to 46.2 mm. Except for this, using the same method as in Example 1, a pillar sample with a length of 10 m was obtained. The outer diameter of the obtained pillar is 46.2 mm. The schematic cross-sectional view of the obtained pillar is shown in Figure 1 . 16 carbon fibers (tows) 2a are disposed adjacent to the FRP inner layer 21.

[0112] Example 3

[0113] In Example 2, it was changed to 24 carbon fiber tows and 114 glass fiber tows. Except for this, using the same method as in Example 2, a pillar sample with a length of 10 m was obtained. The outer diameter is 46.2 mm.

[0114] Example 4

[0115] In Example 2, the carbon fiber tows were changed to 12, and the glass fiber tows were changed to 78 of RS440RR-531AH (4400 tex) manufactured by Nitto Boseki Co., Ltd. Except for this, using the same method as in Example 2, a pillar sample with a length of 10 m was obtained. The outer diameter is 46.2 mm.

[0116] Comparative Example 1

[0117] In Example 1, 114 glass fiber yarn bundles were prepared on the creel 12, and 16 carbon fiber tows were prepared on the creel 13. The order of impregnating them with the curable resin composition and longitudinally arranging them along the length direction of the core layer was opposite to that of Example 1. Except for this, by the same method, a pillar sample with a length of 10 m was obtained. The outer diameter was 42.8 mm.

[0118] Comparative Example 2

[0119] In Example 2, 150 glass fiber yarn bundles were prepared on the creel 12, and 16 carbon fiber tows were prepared on the creel 13. The order of impregnating them with the curable resin composition and longitudinally arranging them along the length direction of the core layer was opposite to that of Example 2. Except for this, by the same method, a pillar sample with a length of 10 m was obtained. The outer diameter was 46.2 mm.

[0120] As Figure 2 shown in the schematic cross-sectional view of, the carbon fibers in the cross-section are in a state where the carbon fiber bundles are not adjacent to each other and have gaps on the outermost peripheral side of the FRP layer.

[0121] Comparative Example 3

[0122] In Example 3, 114 glass fiber yarn bundles were prepared on the creel 12, and 24 carbon fiber tows were prepared on the creel 13. The order of impregnating them with the curable resin composition and longitudinally arranging them along the length direction of the core layer was opposite to that of Example 3. Except for this, by the same method, a pillar sample with a length of 10 m was obtained. The outer diameter was 46.2 mm.

[0123] Comparative Example 4

[0124] In Example 4, 78 glass fiber yarn bundles were prepared on the creel 12, and 12 carbon fiber tows were prepared on the creel 13. The order of impregnating them with the curable resin composition and longitudinally arranging them along the length direction of the core layer was opposite to that of Example 4. Except for this, by the same method, a pillar sample with a length of 10 m was obtained. The outer diameter was 46.2 mm.

[0125] Comparative Example 5

[0126] In Example 2, the glass fiber yarn bundles were changed to 188, and no carbon fiber tows were used. Except for this, by the same method as in Example 2, a pillar sample with a length of 10 m was obtained. The outer diameter was 46.2 mm.

[0127] <Evaluation of the pillar samples for seaweed cultivation obtained from the examples and comparative examples>

[0128] (Dimensions of the cross-section of the pillar sample)

[0129] Cut orthogonally to the longitudinal direction using a circular saw blade saw tool, and measure the inner diameter of the core layer, outer diameter of the core layer, outer diameter of the FRP layer, and outer diameter of the coating layer of the cross-section using a vernier caliper (manufactured by Mitutoyo Corporation, CD-20CPX). Set the number of measurements n to 5 points and represent it by its average value.

[0130] (Volume fraction of reinforcing fibers in the FRP layer and cross-sectional area ratio of glass fibers to carbon fibers in the FRP layer cross-section)

[0131] Calculate the cross-sectional area Sf of the FRP layer based on the above cross-sectional dimensions. For the glass fiber yarn bundles and carbon fiber tows in each example and comparative example, calculate the cross-sectional area Sg of the glass fibers and the cross-sectional area Sc of the carbon fibers based on the number of uses and their respective fineness and density, and calculate through [(Sg + Sc) / Sf]×100.

[0132] In addition, the cross-sectional area ratio of glass fibers to carbon fibers in the FRP layer cross-section is expressed using the above cross-sectional area Sg of the glass fibers and cross-sectional area Sc of the carbon fibers.

[0133] It should be noted that the density of the glass fiber yarn bundle (manufactured by Nitto Boseki Co., Ltd., RS220RL-510AH and RS440RR-531AH: E glass) is set to 2.54 g / cm 3 , and the density of the carbon fiber tow (manufactured by Mitsubishi Chemical Corporation, PYROFIL (registered trademark), TRW40 50L) is set to 1.81 g / cm 3 , and calculations are performed.

[0134] (Flexural strength)

[0135] With reference to JIS K 7074:1988, measure through a three-point bending test (n = 10) under the following conditions.

[0136] · Bending direction: Bend in the vertical direction and the direction with the shortest diameter of the fiber-reinforced resin tubular body (perpendicular to the parallel part) with respect to the longitudinal direction of the sample of the composite tubular body (fiber-reinforced resin tubular body) used as the pillar for seaweed cultivation.

[0137] · Diameter D of the test piece: Measure the width of the fiber-reinforced resin tubular body in the load direction directly below the indenter using a vernier caliper (n = 1)

[0138] · Radius of the fulcrum: 2.0 mm

[0139] · Radius of the indenter: 5.0 mm

[0140] · Distance L between the fulcrums m: (40 ± 8) × D mm (In JIS, the result calculated using the diameter D of the test piece and the solid thickness H)

[0141] · Length l of the test piece m : L m + 660 mm

[0142] · Test speed: 20 mm / min (In JIS, it is 0.01L m 2 / 6H)

[0143] · Bending strength (N): The maximum bending stress applied to the test piece

[0144] (Deviation of bending strength)

[0145] Samples of the seaweed cultivation pillars of the examples and comparative examples were measured with n = 10 by the above method, and the minimum value, maximum value, average value, and standard deviation of the bending strength (N) were obtained. The standard deviation was divided by the average value and expressed as a coefficient of variation (%) by percentage.

[0146] The outer diameter and thickness of the FRP layer, the fineness (tex) and the number of used filaments of the glass fiber bundle and carbon fiber bundle (filament bundle), the volume content ratio (%) of the reinforcing fiber in the FRP layer, the cross-sectional area ratio of the glass fiber / carbon fiber in the FRP layer, the pillar outer diameter, the configuration position of the carbon fiber in the FRP layer, and the bending strength of the seaweed cultivation pillar samples of each example and comparative example are summarized in Table 1.

[0147] [Table 1]

[0148]

[0149] As shown in Table 1, the number of used filaments of the glass fiber bundle (114) and the carbon fiber filament bundle (16) in Example 1 and Comparative Example 1 is the same. In Example 1, carbon fiber is used in the inner layer of the FRP, but in Comparative Example 1, the carbon fiber is arranged on the outer side (the outermost layer side) of the FRP layer. If the two are compared, in Comparative Example 1, the standard deviation of the bending strength is larger than that in Example 1, and the coefficient of variation is 15.1%, which is more than twice that of 7.3% in Example 1.

[0150] In Example 2 where the volume content ratio of the reinforcing fiber in the FRP layer is set to 58.8 vol% and the carbon fiber is arranged in the inner layer of the FRP, and Comparative Example 2 where the carbon fiber is arranged on the outer side of the FRP layer, the coefficients of variation are 6.0% and 11.9%, showing a difference of about twice.

[0151] In addition, in Example 3 and Comparative Example 3 where the cross-sectional area ratio of carbon fiber is increased to 33.5, in Example 3 where the carbon fiber is arranged in the FRP inner layer, the coefficient of variation is 4.7%, and in Comparative Example 3 where the carbon fiber is arranged on the outer side of the FRP layer, the coefficient of variation is 9.2%, showing a difference of about 2 times.

[0152] On the other hand, in Example 4 and Comparative Example 4 where the cross-sectional area ratio of carbon fiber is 15.6, due to the different arrangement positions of the carbon fiber as described above, the coefficients of variation are 7.3% and 13.6%, showing a difference of about 1.9 times.

[0153] On the other hand, in Comparative Example 5, carbon fiber is not used, and only glass fiber is used as the reinforcing fiber. The volume content rate of glass fiber is set to 58.7%. The volume content rate of the reinforcing fiber is approximately the same as that in Example 2 and Comparative Example 2. However, the coefficient of variation in Comparative Example 5 is 5.0%, 6.0% in Example 2, and 11.9% in Comparative Example 2. In Example 2, it can be confirmed that the deviation of the flexural strength is the same as that of the pillar sample of the seaweed cultivation pillar made of conventional glass fiber-reinforced FRP, i.e., Comparative Example 5.

[0154] In addition, in other examples, it is also confirmed that the coefficient of variation is 4.7% to 7.3%, which is a deviation of the flexural strength substantially equivalent to that of the conventional glass fiber-reinforced FRP seaweed cultivation pillar.

[0155] Industrial Applicability

[0156] The seaweed cultivation pillar of the present invention has carbon fiber arranged in the FRP inner layer. Therefore, compared with the FRP layer composed only of glass fiber in the past, in the case of the same outer diameter, it can of course be used as a high-rigidity and lightweight seaweed cultivation pillar, and it is possible to seek the uniformity of the flexural strength brought by the parts on the circumference of the cross-section in the length direction of the applied stress. Therefore, the efficiency of the setting operation in the sea is improved, and the function of the pillar when setting up the seaweed net for seaweed cultivation is also not deviated. Therefore, it can also be effectively used as a suitable seaweed cultivation pillar in the management of the cultivation operation.

[0157] In addition, if it is desired to have the same degree of rigidity as the conventional FRP pillar with only glass fiber as the reinforcing fiber, the outer diameter can be made thinner, and it can be used as a seaweed cultivation pillar that can seek lightweight and improvement in operability due to the thinner diameter.

[0158] In addition, the manufacturing method of the pillar for laver cultivation of the present invention can achieve more uniform bending strength brought by the portions on the circumference of the cross-section in the length direction where stress is applied. Therefore, it can be used as a method for manufacturing the pillar for laver cultivation of the present invention with good reproducibility, stability, and economy. The operability of the pillar for laver cultivation of the present invention in manual work and the like is excellent, and it can achieve both light weight and high rigidity. It is relatively inexpensive and practical.

[0159] Explanation of Reference Numerals

[0160] 1. Core layer; 2. FRP layer; 2a. Carbon fiber bundle (glass fiber in the comparative example); 2b. Glass fiber bundle (carbon fiber in the comparative example); 2c. Thermosetting resin cured product (matrix component); 3. Coating layer (thermoplastic resin coating layer); 4. Pillar for laver cultivation (composite tubular object); 5. Melting and extruding machine for the core; 6. Core cooling tank; 7. Drawing die device; 8. Melting and extruding machine for the coating layer; 9. Cooling tank; 10. Heat curing tank; 11. Impregnation tank; 11a. Impregnation tank for the FRP inner layer; 11b. Impregnation tank for the FRP outer layer; 12. Warp beam rack (for the reinforcing fiber bundle of the FRP inner layer); 13. Warp beam rack (for the reinforcing fiber bundle of the FRP outer layer); 14. Uncured tubular object; 15. Uncured tubular object with a coating layer; 16. Composite tubular object; 21. FRP inner layer; 22. FRP outer layer.

Claims

1. A pillar for seaweed cultivation, characterized in that, It is a pillar for seaweed cultivation with a composite structure in which a core layer made of a thermoplastic resin, an FRP layer formed on the outer periphery of the core layer, and a coating layer formed on the outer periphery of the FRP layer are integrally bonded. At least the outer peripheral surface of the core layer is made of a thermoplastic resin that has chemical affinity with the thermosetting resin that is the matrix component constituting the FRP layer. The FRP layer has an FRP inner layer and an FRP outer layer. In the FRP inner layer, long fibrous carbon fibers are the main body of the reinforcing fibers and are longitudinally arranged and bonded to the outer periphery in the longitudinal direction of the core layer through the matrix component. In the FRP outer layer, long fibrous glass fibers are the main body of the reinforcing fibers and are longitudinally arranged and bonded to the outer periphery of the FRP inner layer through the matrix component. The cross-sectional area ratio of the glass fibers to the carbon fibers in the FRP layer is 60:40 to 90:

10. At least the inner peripheral surface of the coating layer is made of a thermoplastic resin that has chemical affinity with the thermosetting resin that is the matrix component constituting the FRP layer.

2. The pillar for seaweed cultivation according to claim 1, wherein In the FRP inner layer, a plurality of carbon fiber bundles are arranged on the circumference in a centrosymmetric manner, and the carbon fiber bundles are arranged adjacent to each other.

3. The pillar for seaweed cultivation according to claim 1, wherein The cross-sectional area ratio of the glass fibers to the carbon fibers in the FRP layer is 70:30 to 80:

20.

4. A manufacturing method of the pillar for laver cultivation according to any one of claims 1 to 3, characterized in that, It has the following steps (i) to (vii): (i) Prepare the required number of carbon fiber bundles and glass fiber bundles as long fibrous reinforcing fibers, pass the carbon fiber bundles and glass fiber bundles through the predetermined guiding holes of the collective guiding member respectively, and further, arrange them in parallel, and guide them through the impregnation operation guiding member of the impregnation tank, the drawing die for longitudinally arranging them in a predetermined configuration on the outer periphery of the core layer, the melt extrusion machine for the coating layer, and the production line, and prepare them in a manner that the reinforcing fiber bundles can be drawn. (ii) Inject a liquid curable resin composition containing a thermosetting resin and a heat curing agent into the impregnation tank. (iii) Continuously extrude the thermoplastic resin forming the core layer from the core melt extrusion machine into a circular tube of a predetermined size, and continuously draw it through the production line to manufacture the core layer. (iv) While drawing the reinforcing fiber bundles prepared in (i), lower the impregnation operation guiding member to the impregnation tank, impregnate the curable resin composition into the reinforcing fiber bundles, longitudinally arrange them on the outer periphery of the core layer advancing in the center of the hole part of the drawing die, and gradually draw the remaining resin composition using the drawing die to obtain an uncured tubular body in which the reinforcing fiber bundles are longitudinally arranged on the core layer. (v) Pass the uncured tubular body through the crosshead of the melt extrusion machine for the coating layer, extrude and coat it in a circular shape using the thermoplastic resin for the coating layer, and then cool the coating layer to obtain an uncured tubular body with a coating layer. (vi) Introduce the uncured tubular body with a coating layer into the heat curing tank, thermally cure the uncured thermosetting resin composition inside, and draw a tubular body with a composite structure in which the core layer, the FRP layer, and the coating layer are integrally bonded. And (vii) Cut the pulled tubular material into a predetermined length to be used as a support for seaweed cultivation.

Images