Method for determining the specifications of fiber reinforcement material for marine hoses and method for manufacturing marine hoses

Abstract

To provide a method of determining specifications of a fiber reinforced material which is excellent in fatigue resistance capable of securing satisfactory pressure resistance while maintaining expansion characteristics of a marine hose properly, and a method of manufacturing the marine hose.SOLUTION: Fiber cords 10 which constitute a fiber reinforced material 9 of a rattan woven structure have specifications such that three or four lines of polyester filaments 10a are twisted, a twist coefficient K of the fiber cords 10 is set to be 1,900 or more and 2,900 or less, a correlation R between a predetermined elongation rate E2 of the fiber cords 10 of a plurality of kinds having different specifications and a hose elongation rate E1 on a predetermined expansion test of respective marine hoses 1 in which the fiber-reinforced material 9 having the respective fiber codes 10 as a constitution member is embedded as reinforcing layers 4A, 6A is grasped beforehand, a threshold Th of the predetermined elongation rate E2 is set based on a standard value of the hose elongation rate E1 and the correlation R on the predetermined expansion test, and the predetermined elongation rate E2 of the fiber cords 10 used as reinforced layers 4A, 6A is set to be the threshold Th or less.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to a method for determining specifications of a fiber reinforcing material for a marine hose and a method for manufacturing a marine hose. More specifically, the present invention relates to a method for determining specifications of a fiber reinforcing material for a marine hose, which has excellent fatigue resistance and can ensure sufficient pressure resistance while appropriately maintaining the expansion characteristics of the marine hose, and a method for manufacturing a marine hose.

Background Art

[0002] A plurality of reinforcing layers are embedded in a marine hose. For example, a fiber reinforcing material formed by weaving fiber cords in a curtain shape is used for these reinforcing layers (see, for example, paragraph 0011 of Patent Document 1 and paragraph 0023 of Patent Document 2). These reinforcing layers suppress excessive expansion of the hose body against the internal pressure applied to the marine hose by the fluid flowing through the flow path and ensure a specified pressure resistance.

[0003] As a certification test for a marine hose, a destructive test is performed in which an internal pressure is applied and the hose is destroyed after a bending test is carried out a specified number of times. In this bending test, since the fiber cords constituting the fiber reinforcing material are repeatedly bent and fatigued, if the fatigue resistance of this fiber cord is poor, it becomes difficult to ensure the specified pressure resistance required for the marine hose. To improve the fatigue resistance of the fiber cord, it is effective to increase the number of twists of the fiber cord. However, as the number of twists of the fiber cord increases, it becomes disadvantageous for suppressing the elongation of the marine hose to which an internal pressure is applied. Along with this, it becomes difficult to satisfy the expansion characteristics (standard value of hose elongation rate) required in a predetermined expansion test for the marine hose.

[0004] It has been proposed to use a twisted yarn made of two polyester filaments as a fiber cord, with a lower twist coefficient of approximately 1000 to 2500 and an upper twist coefficient of approximately 1500 to 3600 (see claims, paragraphs 0066 to 0069 of Patent Document 3). However, it is difficult to obtain sufficient cord strength with a fiber cord made by twisting two polyester filaments in this way, so in marine hoses in which a reinforcing layer using this fiber cord is embedded, it is necessary to embed more of the reinforcing layer in order to ensure the specified pressure resistance. Therefore, further improvements are needed to obtain a fiber reinforcement with excellent fatigue resistance that can ensure sufficient pressure resistance while properly maintaining the expansion characteristics of the marine hose. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 10-157016 [Patent Document 2] Japanese Patent Publication No. 2021-148193 [Patent Document 3] Japanese Patent Publication No. 2017-150105 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] The object of the present invention is to provide a method for determining the specifications of a fatigue-resistant fiber reinforcement material for marine hoses that can ensure sufficient pressure resistance while properly maintaining the expansion characteristics of the marine hose, and a method for manufacturing a marine hose. [Means for solving the problem]

[0007] To achieve the above objective, the present invention provides a method for determining the specifications of a fiber reinforcement material for marine hoses, comprising a number of parallel fiber cords and transverse cords that cross these fiber cords in a sewing-like manner, and used as a reinforcement layer for a marine hose. The method for determining the specifications of a fiber reinforcement material having a blind weave structure, used as a reinforcement layer for a marine hose, is characterized by: setting the fiber cords to be made of three or four polyester filaments twisted together; setting the twist coefficient K of the fiber cords, calculated by the following formula (1), to 1900 or more and 2900 or less; pre-determining the correlation between a predetermined elongation rate of multiple types of fiber cords with different specifications and the hose elongation rate in a predetermined expansion test of each marine hose in which the fiber reinforcement material, each of the fiber cords as constituent members, is embedded as the reinforcement layer; setting a threshold for the predetermined elongation rate based on the standard value of the hose elongation rate in the predetermined expansion test required for the marine hose and the correlation; and setting the predetermined elongation rate of the fiber cords used as the reinforcement layer to be less than or equal to the threshold. Twist coefficient K = T × D 1 / 2 ...(1) Here, T is the number of twists per 10cm of the fiber cord, and D is the total fineness of the fiber cord (dtex).

[0008] The present invention provides a method for manufacturing a marine hose, characterized in that the fiber reinforcing material having the specifications determined by the above-described method for determining the specifications of the fiber reinforcing material is embedded as the reinforcing layer between the inner layer and the cover layer to form an unvulcanized hose molded body, and then vulcanizes this hose molded body. [Effects of the Invention]

[0009] According to the method for determining the specifications of the fiber reinforcement material for marine hoses of the present invention, by specifying that the fiber cord constituting the fiber reinforcement material having a blind weave structure is made of three or four polyester filaments twisted together, and setting the twist coefficient K of the fiber cord to 1900 or more and 2900 or less, it is advantageous to improve the fatigue resistance of the fiber cord and ensure sufficient pressure resistance of the marine hose. Furthermore, based on the standard value of the hose elongation rate and the correlation, a threshold for the predetermined elongation rate is set, and the predetermined elongation rate of the fiber cord used as the reinforcement layer is set to be less than or equal to the threshold. As a result, in a marine hose in which this fiber reinforcement material, which has this fiber cord as a constituent component, is embedded as the reinforcement layer, excessive elongation of the hose body when internal pressure is applied is avoided, which is advantageous for properly maintaining the expansion characteristics of the marine hose. [Brief explanation of the drawing]

[0010] [Figure 1] This is an explanatory diagram illustrating a marine hose manufactured according to the present invention. [Figure 2] This is an explanatory diagram illustrating a magnified, longitudinal cross-sectional view of a portion of the marine hose shown in Figure 1. [Figure 3] Figure 2, section AA, is an explanatory diagram illustrating the cross-sectional structure of a marine hose. [Figure 4] Figure 1 is an explanatory diagram illustrating a reinforcing layer by cutting out a portion of the marine hose. [Figure 5] Figure 4 is an explanatory diagram illustrating the use of marine hose fiber reinforcement material as a reinforcing layer, laid flat and viewed in plan. [Figure 6] Figure 5 is an explanatory diagram illustrating a fiber cord in a side view. [Figure 7] Figure 6 is an explanatory diagram illustrating a schematic cross-sectional view of the fiber cord. [Figure 8] This graph illustrates the correlation between the elongation rate of the fiber cords of a fiber reinforcement material embedded as a reinforcing layer in a marine hose and the elongation rate of the marine hose in which this fiber reinforcement material is embedded as a reinforcing layer during a predetermined expansion test. [Figure 9]It is an explanatory drawing that illustrates an unvulcanized hose molded body with a part thereof cut out. [Figure 10] It is an explanatory drawing that illustrates the vulcanization process of the hose molded body of FIG. 9.

Embodiments for Carrying out the Invention

[0011] Hereinafter, a method for determining specifications of a fiber reinforcing material for a marine hose and a method for manufacturing a marine hose according to the present invention will be described based on the embodiments shown in the drawings.

[0012] The marine hose 1 illustrated in FIGS. 1 to 4 includes connecting fittings 2 for connecting another marine hose 1 at both longitudinal ends of a cylindrical hose body 1A. The connecting fitting 2 has a nipple 2b extending in the longitudinal direction of the marine hose 1 and a flange 2a joined to one longitudinal end of the nipple 2b. Generally, about 8 to 10 marine hoses 1 are connected and used.

[0013] As illustrated in FIGS. 2 and 3, the hose body 1A extending between the nipples 2b at both ends is configured by sequentially laminating an inner surface layer 3, an inner peripheral side reinforcing layer group 4, a body wire layer 5, an outer peripheral side reinforcing layer group 6, a buoyancy layer 7, and a cover layer 8 from the inner peripheral side to the outer peripheral side of the outer periphery of the flow path 1a. The alternate long and short dash line CL in the figure is a center line passing through the cross-sectional center of the marine hose 1 and extending in the hose longitudinal direction. In FIG. 3, a range of 1 / 4 of the cross-section of the marine hose 1 is shown, but the other range (3 / 4 range) not shown has the same structure. [[ID=二十一]]

[0014] [[ID=二十二]] [[ID=二十三]] [[ID=二十四]]

[0015] [[ID=二十五]] [[ID=二十六]]The inner peripheral side of the inner surface layer 3 becomes the flow path 1a of the fluid L. Examples of the fluid L include crude oil, gasoline, LPG, etc. The inner surface layer 3 is made of an appropriate material depending on the type of the fluid L. When the fluid L is crude oil or the like, it is made of nitrile rubber or the like having excellent oil resistance.In this embodiment, two inner peripheral side reinforcing layer groups 4 are laminated, but the inner peripheral side reinforcing layer group 4 may also be one. The inner peripheral side reinforcing layer group 4 and the outer peripheral side reinforcing layer group 6 are each composed of a plurality of reinforcing layers 4A and 6A laminated together. The number of the reinforcing layers 4A and 6A is set to an appropriate number as needed. For example, the reinforcing layer 4A is about 4 to 30 layers, and the reinforcing layer 6A is about 2 to 10 layers.

[0016] As illustrated in FIG. 4, in each of the reinforcing layers 4A and 6A, a plurality of cross cords 11 that traverse so as to sew a large number of fiber cords 10 aligned in parallel up and down are arranged at intervals in the longitudinal direction of the fiber cords 10, forming a curtain weave structure. In each of the reinforcing layers 4A and 6A, a large number of fiber cords 10 extend obliquely at a predetermined angle with respect to the center line CL. Between the reinforcing layers 4A laminated adjacent to each other vertically, in the reinforcing layer 6A, the inclination directions of the fiber cords 10 are opposite to each other and intersect. Details of the reinforcing layers 4A and 6B will be described later.

[0017] The main body wire layer 5 is formed by spirally winding metal wires at a predetermined interval around the outer rubber of the inner peripheral side reinforcing layer group 4. The inner peripheral side reinforcing layer group 4, the main body wire layer 5, and the outer peripheral side reinforcing layer group 6 are fixed to the nipple 2b by the nipple wires 4w, 5w, and 6w at one end of each and a fixing ring 2c protruding from the outer peripheral surface of the nipple 2b. Between the inner peripheral side reinforcing layer group 4 and the outer peripheral side reinforcing layer group 6, when the fluid L leaks from the flow path 1a, it becomes a space (fluid retention layer) for storing the fluid L.

[0018] The buoyancy layer 7 is made of a material that exhibits buoyancy to float the marine hose 1 such as sponge rubber or foamed polyurethane on the sea. Therefore, this marine hose hose hose 1 is of a so-called floating type. When the marine hose 1 is of a submarine type used in a state of being submerged in the sea, the buoyancy layer 7 is omitted.

[0019] The cover layer 8 is made of a water-impermeable material such as rubber, and a line pattern or the like with excellent visibility is provided on its surface. An appropriate material with excellent weather resistance and abrasion resistance is adopted for the cover layer 8.

[0020] The fiber reinforcement material 9 for marine hoses (hereinafter referred to as fiber reinforcement material 9), illustrated in Figure 5, is embedded in the hose body 1A as the respective reinforcement layers 4A and 6A. The fiber reinforcement material 9 has a woven structure consisting of fiber cords 10 arranged in parallel in the width direction W and extending in the longitudinal direction L, and transverse cords 11 that extend in the width direction W, crossing these fiber cords 10 in a manner that stitches them up and down.

[0021] The specifications of this fiber reinforcement 9 are determined by the specification determination method of the present invention.

[0022] A blind weave structure is adopted for the fiber reinforcement material 9. In a blind weave structure, interference between the fiber cords 10 and the transverse cords 11 is reduced, which is advantageous for improving the durability of the fiber reinforcement material 9 (reinforcement layers 4A, 6A). The weaving density of the fiber cords 10 is set to, for example, 30 to 70 cords / 5 cm, and the weaving density of the transverse cords 11 is set to, for example, 2 to 8 cords / 5 cm. The spacing (gap) between adjacent fiber cords 10 is set to, for example, 0.13 mm to 0.25 mm, more preferably 0.2 mm to 0.24 mm.

[0023] The fiber cord 10 is made by twisting together three or four polyester filaments 10a. The fiber cord 10 illustrated in Figures 6 and 7 is formed by twisting together three filaments 10a, but it can also be made by twisting together four filaments 10a. The fiber cord 10 is formed when each filament 10a, which is twisted downwards in one direction, is then twisted upwards in the opposite direction to the downward twist.

[0024] Forming the fiber cord 10 by twisting together three or four polyester filaments 10a is advantageous for improving the strength at break (cord strength) without compromising the fatigue resistance of the fiber cord 10. With a fiber cord 10 formed by twisting together two filaments 10a, it is difficult to improve the cord strength. Increasing the thickness of the filaments 10a to improve cord strength increases the weight, which becomes excessive for the amount used in one marine hose. Furthermore, the increased thickness of the fiber cord 10 (reinforcement layers 4A, 6A) leads to a larger diameter for the marine hose 1. Additionally, with a fiber cord 10 formed by twisting together five or more filaments 10a, the outer diameter of the cord becomes excessively large, making it more susceptible to fatigue damage. To reduce the weight of the fiber cord 10 while improving fatigue resistance, it is preferable to form it by twisting together three filaments 10a instead of four.

[0025] Furthermore, the initial break strength of the fiber cord 10 in its original state (initial cord strength) is preferably 300 N / strand or more, and more preferably 320 N / strand or more. Setting the initial cord strength to this level is advantageous for stably ensuring the pressure resistance of the marine hose 1.

[0026] The outer diameter of the fiber cord 10 should be, for example, between 0.80 mm and 0.95 mm. If the outer diameter is less than 0.80 mm, it becomes difficult to ensure sufficient cord strength in the fiber cord 10, which is detrimental to improving the pressure resistance of the marine hose 1. On the other hand, if the outer diameter exceeds 0.95 mm, it is detrimental to reducing the weight of the fiber cord 10, and the weight increase becomes excessive for the amount used in one marine hose. In addition, the thickness of the fiber cord 10 (reinforcement layers 4A, 6A) increases, leading to a larger diameter marine hose 1.

[0027] Furthermore, in this fiber reinforcement material 9, the twist coefficient K of the fiber cord 10, calculated by the following formula (1), is set to 1900 or more and 2900 or less. Twist coefficient K = T × D 1 / 2 ...(1) Here, T is the number of twists per 10cm of the fiber cord, and D is the total fineness of the fiber cord (dtex).

[0028] If the twist coefficient K of the fiber cord 10 is less than 1900, it is disadvantageous for ensuring the fatigue resistance of the fiber cord 10. On the other hand, if the twist coefficient K is greater than 2900, the decrease in cord strength of the fiber cord 10 becomes significant. Therefore, in order to ensure the fatigue resistance of the fiber cord 10 while avoiding a decrease in cord strength, it is preferable to set the twist coefficient K to 1900 or more and 2900 or less, and more preferably to 1950 or more and 2600 or less. Setting the twist coefficient K within this range is advantageous for stably ensuring sufficient pressure resistance of the marine hose 1. Furthermore, it eliminates the need to excessively laminate the reinforcing layers 4A and 6A in order to ensure sufficient pressure resistance of the marine hose 1.

[0029] For Marine Hose 1, the hose elongation rate E1 in a specified expansion test must be below the standard value. The specific method for this specified expansion test is as follows:

[0030] First, an internal pressure of 0.7 bar is applied to Marine Hose 1, and the hose length (initial hose length) is measured. Next, the internal pressure is increased from 0.7 bar to half of the rated pressure over 5 minutes and held for 10 minutes. After that, the internal pressure is reduced to 0, and then increased to the rated pressure over 5 minutes and held for 10 minutes, and the length of the hose in this state (rated pressure hose length) is measured.

[0031] The hose elongation rate E1 is calculated as (rated pressure hose length - initial hose length / initial hose length) × 100%. The standard value for this hose elongation rate E1 is 2.5% or less. If the hose elongation rate E1 is 2.5% or less, it is evaluated as passing; if it exceeds 2.5%, it is evaluated as failing.

[0032] Therefore, the manufactured marine hose 1 must have a hose elongation rate E1 in this predetermined expansion test that is less than or equal to the standard value (2.5%). If the elongation of the fiber cord 10 is large, the marine hose 1 in which the fiber reinforcement material 9, which uses the fiber cord 10 as a component, is embedded as reinforcement layers 4A and 6A tends to stretch more easily when internal pressure is applied. In other words, it is considered that there is a relatively high correlation between the predetermined elongation rate E2 of the fiber cord 10 and the hose elongation rate E1.

[0033] Therefore, in this embodiment, the correlation R between a predetermined elongation rate E2 of multiple types of fiber cords 10 with different specifications and the hose elongation rate E1 in the predetermined expansion test of each marine hose 1 in which fiber reinforcing material 9, which consists of these fiber cords 10 as constituent members, is embedded as reinforcing layers 4A and 6A is obtained in advance.

[0034] For example, multiple fiber cords 10 with different predetermined elongation rates E2 are prepared, and test samples of the marine hose 1 are manufactured using fiber reinforcement materials 9 that consist of each fiber cord 10 as a component. Then, the hose elongation rate E1 is obtained by actual measurement using each test sample of the marine hose 1. Alternatively, this hose elongation rate E1 may be obtained by computer simulation of a predetermined expansion test of the marine hose 1. As the predetermined elongation rate E2 of the fiber cord 10, for example, the elongation rate at an arbitrary tensile stress of the degree of tensile stress acting on the fiber cord 10 when the marine hose 1 is used, or a lower tensile stress, is adopted.

[0035] For example, as shown in Figure 8, the correlation R between the hose elongation rate E1 and the predetermined elongation rate E2 of the fiber cord 10 is obtained. When determining the specifications of the fiber reinforcement material 9, a threshold Th for the predetermined elongation rate E2 of the fiber cord 10 to be used is set based on the standard value of the hose elongation rate E1 (2.5%) and the obtained correlation R. Then, the predetermined elongation rate E2 of the fiber cord 10 of the fiber reinforcement material 9 used as the reinforcement layers 4A and 6A of the marine hose 1 is set to be less than or equal to the set threshold Th.

[0036] In a marine hose 1 in which fiber reinforcement material 9, consisting of fiber cords 10 with a predetermined elongation rate E2 less than or equal to this threshold Th, is embedded as reinforcing layers 4A and 6A, it becomes possible to more accurately set the hose elongation rate E1 in the above predetermined expansion test to the standard value (2.5%) or less. In other words, in this marine hose 1, excessive elongation of the hose body 1A when internal pressure is applied is avoided, which is advantageous for properly maintaining the expansion characteristics of the marine hose 1.

[0037] The inventors of this application confirmed and analyzed the correlation between the elongation rate of the fiber cord 10 at various tensile stresses, defined as a predetermined elongation rate E2, and the hose elongation rate E1. As a result, they found that there is a very high correlation between the elongation rate E2 of the fiber cord 10 at 1.3 cN / dtex and the hose elongation rate E1.

[0038] Therefore, when determining the specifications of the fiber reinforcement material 9, it is advisable to obtain the correlation R data between the hose elongation rate E1 in the predetermined expansion test described above and the elongation rate E2 of the fiber cord 10 embedded in the marine hose 1 at 1.3 cN / dtex. Then, based on the standard value of the hose elongation rate E1 (2.5%) and this determined correlation R, it is preferable to set a threshold Th for the predetermined elongation rate E2 of the fiber cord 10. By using a fiber cord 10 with a predetermined elongation rate E2 less than or equal to this threshold Th, it becomes possible to more accurately set the hose elongation rate E1 in the predetermined expansion test described above to the standard value (2.5%) or less.

[0039] When using this correlation R, by setting the elongation rate E2 of the fiber cord 10 at 1.3 cN / dtex to 6.5% or less, the hose elongation rate E1 of marine hoses 1 of various specifications can be made generally below the standard value (2.5%). Therefore, if you want to set a threshold Th simply, it is good to set the elongation rate E2 (6.5%) of the fiber cord 10 at 1.3 cN / dtex as the threshold Th.

[0040] In other words, the elongation rate E2 of the fiber cord 10 used in the fiber reinforcement material 9 embedded as reinforcing layers 4A and 6A should be 6.5% or less at 1.3 cN / dtex. To suppress the hose elongation rate E1, it is preferable to set the elongation rate E2 of the fiber cord 10 at 1.3 cN / dtex to 5.5% or less, and more preferably to 5.0% or less. The lower limit of the elongation rate of the fiber cord 10 at 1.3 cN / dtex is, for example, 3%.

[0041] The predetermined elongation rate E2 of the fiber cord 10 (e.g., elongation rate E2 at 1.3 cN / dtex) can be adjusted to a desired range by known methods. For example, the predetermined elongation rate E2 can be adjusted to a desired range by adjusting at least one of the following: the heating temperature, the tension, or the heat treatment speed (time) when heat-treating the fiber cord 10 using known methods, or by using a suitable polyester yarn.

[0042] In the fiber reinforcement material 9 (reinforcement layers 4A, 6A), the transverse cords 11 have little effect on the performance and characteristics of the fiber cords 10, so any known specification can be adopted. The outer diameter of the transverse cords 11 may be smaller than the outer diameter of the fiber cords 10.

[0043] The specified elongation E2 and breaking strength (cord strength) of the fiber cord 10 shall be the values ​​measured in accordance with JIS L1017:2002. Note that the cord strength of the fiber cord 10 changes slightly before and after vulcanization, but can be considered generally the same.

[0044] To manufacture the marine hose 1, a known method is sufficient. A connecting fitting 2 is fitted onto a cylindrical mandrel 13, and the components of the hose body 1A (inner layer 3, inner circumferential reinforcing layer group 4, main wire layer 5, outer circumferential reinforcing layer group 6, buoyancy layer 7, and cover layer 8), as illustrated in Figure 2, are sequentially laminated on the outer circumference of the mandrel 13. The fiber reinforcement material 9 is covered with a known adhesive rubber and embedded as reinforcement layers 4A and 6A between the inner layer 3 and the cover layer 8. This forms the hose molded body 12 as illustrated in Figure 9.

[0045] Next, as illustrated in Figure 10, the hose molded body 12 is placed in a known vulcanization apparatus 14 and vulcanized. In this vulcanization process, the unvulcanized rubber and adhesive rubber contained in the components of the hose molded body 12 are vulcanized, and the laminated components are joined together to form a single unit, thereby manufacturing the marine hose 1.

[0046] As described above, in the present invention, the fiber reinforcement material 9 is made of a blind-woven structure in which a large number of fiber cords 10, formed by twisting together three or four polyester filaments 10a, are arranged in parallel, and the twist coefficient K of the fiber cords 10 is set to 1900 or more and 2900 or less, and the predetermined elongation rate E2 of the fiber cords 10 is set to be less than or equal to the threshold Th described above. By simultaneously fulfilling these requirements, the fatigue resistance of the fiber cords 10 is improved while elongation is appropriately suppressed, and sufficient cord strength can be obtained. There is also a synergistic effect from simultaneously fulfilling these requirements, so in a marine hose 1 in which this fiber reinforcement material 9 is embedded as reinforcement layers 4A and 6A, excessive elongation of the hose body 1A when internal pressure is applied is avoided, which is very advantageous in properly maintaining the expansion characteristics of the marine hose 1 and ensuring sufficient pressure resistance. [Examples]

[0047] Twelve types of fiber cords were prepared, including a conventional example, Examples 1-6, and Comparative Examples 1-5, by varying the specifications of fiber cords formed by twisting polyester filaments, as shown in Table 1. The twist coefficient K in Table 1 is the value calculated by equation (1) described above. In Comparative Examples 4 and 5, where the spacing between fiber cords is a negative value in Table 1, it means that adjacent fiber cords arranged in parallel are interfering with each other. Tensile and fatigue tests were performed on each fiber cord specification as described below.

[0048] [Tensile testing of fiber cords] The breaking strength of each fiber cord was measured in accordance with JIS L1017:2002, and the elongation rate E2 at 1.3 cN / dtex was calculated from the measurement data. The results are shown in Table 1.

[0049] [Fatigue testing of fiber cords] In accordance with the disc fatigue strength (Goodrich method) specified in JIS L1017:2002 Annex 1 2.2.2, rubber test specimens embedded with each fiber cord were rotated at 1400 rpm under room temperature conditions, subjecting them to a ±15% strain for 2 million cycles over 24 hours. The break strength of the fiber cords removed from the rubber test specimens before the fatigue test (initial cord strength) and the break strength of the fiber cords removed from the rubber test specimens after the fatigue test (post-fatigue test cord strength) were measured. The cord strength retention rate was then calculated as follows: (post-fatigue test cord strength / initial cord strength) × 100%. The initial code strength standard is 300 N / string. A value above this standard indicates sufficient strength, while a value below this standard indicates insufficient strength. The standard value for code strength retention is 75%. A value above this standard indicates sufficient fatigue resistance, while a value below this standard indicates insufficient fatigue resistance.

[0050] Furthermore, using each fiber cord, twelve types of reed-woven structures (fiber cord weaving density of 48 strands / 5cm, transverse cord weaving density of 4 strands / cm) were fabricated, as illustrated in Figure 5, with only the fiber cord being different. The transverse cords were made of cotton fibers with an outer diameter of 0.30 mm.

[0051] Each fiber reinforcement was embedded as a reinforcement layer to create marine hose samples that differed only in the reinforcement layer, and the aforementioned expansion test of the specified marine hose was performed. Each marine hose sample had a structure in which two inner circumference reinforcement layer groups, a main wire layer, one outer circumference reinforcement layer group, a buoyancy layer, and a cover layer were sequentially laminated on the inner surface. The number of reinforcement layers in each inner circumference reinforcement layer group was 10, and the number of reinforcement layers in each outer circumference reinforcement layer group was 8. The hose elongation rate E1 was measured during this expansion test. The results are shown in Table 1. The standard value for the hose elongation rate E1 is 2.5%, and if it is below this standard value, the expansion characteristics of the marine hose are considered appropriate, and if it exceeds this standard value, the expansion characteristics of the marine hose are considered inappropriate.

[0052] [Table 1]

[0053] The results in Table 1 show that in Examples 1 to 6, the initial cord strength, cord strength retention rate, and hose elongation rate E1 of the fiber cord all meet the standard values. Therefore, it can be seen that the fiber cords corresponding to Examples 1 to 6 have excellent fatigue resistance, and that the marine hoses corresponding to Examples 1 to 6 can ensure sufficient pressure resistance while properly maintaining expansion characteristics. [Explanation of Symbols]

[0054] 1 Marine Hose 1A Hose body 1b channel 2 Connecting fittings 2a Flange 2b Nipple 2c fixing ring 3. Inner Layer 4. Inner circumferential reinforcing layer 4A Reinforcement layer 4w nipple wire 5. Main wire layer 5W Nipple Wire 6. Outer perimeter reinforcement layer 6A Reinforcement layer 6w nipple wire 7 Buoyancy layer 8. Cover layer 9. Fiber reinforcement 10 Fiber cords 10a filament 11 Cross-sectional code 12 Hose molded body 13 Mandrels 14. Vulcanizing apparatus L fluid

Claims

1. In a method for determining the specifications of a fiber reinforcement material having a blind weave structure used as a reinforcing layer for a marine hose, the material has multiple parallel fiber cords and transverse cords that cross these fiber cords in a sewing-like manner, The fiber cord is made of three or four polyester filaments twisted together, and the twist coefficient K of the fiber cord, calculated by the following formula (1), is set to 1900 or more and 2900 or less. The correlation between the predetermined elongation rate of multiple types of fiber cords with different specifications and the hose elongation rate in a predetermined expansion test of each marine hose in which the fiber reinforcing material, which consists of each of the fiber cords as a constituent component, is embedded as the reinforcing layer is determined in advance, and a threshold value for the predetermined elongation rate is set based on the standard value of the hose elongation rate in the predetermined expansion test required for marine hoses and the correlation, A method for determining the specifications of a fiber reinforcing material such that the predetermined elongation rate of the fiber cord used as the reinforcing layer is less than or equal to the threshold. Twist coefficient K = T × D 1 / 2 ... (1) Here, T is the number of twists per 10 cm of the fiber cord, and D is the total fineness of the fiber cord (dtex).

2. The method for determining the specifications of a fiber reinforcement material according to claim 1, wherein the elongation rate of the fiber cord at 1.3 cN / dtex is set to the predetermined elongation rate.

3. The method for determining the specifications of a fiber reinforcement material according to claim 2, wherein the elongation rate of the fiber cord at 1.3 cN / dtex is 6.5%.

4. A method for determining the specifications of a fiber reinforcement material according to any one of claims 1 to 3, wherein the twist coefficient K is set to 1950 or more and 2600 or less, and the breaking strength of the fiber cord is set to 300 N or more.

5. A method for determining the specifications of a fiber reinforcement material according to any one of claims 1 to 4, wherein the fiber cord is made of three polyester filaments twisted together.

6. A method for determining the specifications of a fiber reinforcement material according to any one of claims 1 to 5, wherein the outer diameter of the fiber cord is set to 0.80 mm or more and 0.95 mm or less.

7. A method for manufacturing a marine hose, comprising: embedding the fiber reinforcing material having the specifications determined by the method for determining the specifications of the fiber reinforcing material according to any one of claims 1 to 6 as the reinforcing layer between the inner layer and the cover layer to form an unvulcanized hose molded body; and vulcanizing the hose molded body.

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