Rubber article and method of manufacturing the same

Abstract

The present invention provides a rubber product in which the number of reinforcing layers of a cylindrical portion is reduced while ensuring sufficient pressure resistance to internal pressure, thereby suppressing a reduction in productivity and molding processability, and a manufacturing method thereof. In a rubber product having a cylindrical portion (3a) manufactured by molding a cylindrical shaped body (1A) in which a plurality of reinforcing layers (5) are coaxially stacked between an inner layer (4) and an outer layer (10), and subjecting the shaped body (1A) to vulcanization, each reinforcing layer (5) is composed of a fabric (6) in which a plurality of fiber cords (7) are laid up and subjected to a prescribed bonding treatment, and coating rubber layers (9) covering both surfaces of the fabric (6), and is formed in a twill structure in which the fiber cords (7) of the reinforcing layers (5) extend in intersecting directions, and as each fabric (6), a fabric having a tensile strength in the fiber cord extension direction of 4320 N / cm or more and a weight of 950 g / m 2 the following specifications, and the bending stiffness after the prescribed bonding treatment is 30 g / cm or less, and the thickness of each coating rubber layer (9) is 0.2 mm or more and 1 mm or less.

Description

TECHNICAL FIELD

[0001] The present application relates to a rubber product and a manufacturing method thereof, and more particularly to a rubber product having a cylindrical portion in which a plurality of reinforcing layers are embedded in a coaxial manner between an inner layer and an outer layer, and a manufacturing method thereof. BACKGROUND

[0002] In a rubber product such as an air-filled fender or a marine hose, reinforcing layers are embedded in a cylindrical portion thereof. The reinforcing layers are embedded in order to resist internal pressure acting on the rubber product. For example, reinforcing layers composed of a fabric having a plurality of pull-plied fiber cords and coated rubber layers covering both surfaces thereof are used (see Patent Document 1). Generally, a plurality of reinforcing layers are embedded in a laminated manner between an inner layer and an outer layer of the cylindrical portion, and the fiber cords of the adjacent laminated reinforcing layers extend in crossing directions (become a so-called twill structure). The coated rubber layers sandwiched between the adjacent laminated fabric layers are set to respective layer thicknesses to ensure sufficient joint strength.

[0003] If the number of laminated reinforcing layers embedded in the cylindrical portion is increased in order to resist greater internal pressure, the time required for the laminating work of the reinforcing layers is prolonged, and thus it is not favorable for improving the productivity of the rubber product. If the number of laminated reinforcing layers is increased, the weight also increases, and thus the moldability is also deteriorated. In addition, if the layer thickness of the coated rubber layer is too large, the moldability is deteriorated. On the other hand, if the layer thickness of the coated rubber layer is too small, the joint strength between the reinforcing layers or the joint strength between the reinforcing layers and the adjacent members is insufficient, and thus it is not favorable for ensuring sufficient pressure resistance. Therefore, there is room for improvement in terms of ensuring sufficient pressure resistance against internal pressure while reducing the number of laminated reinforcing layers embedded in the cylindrical portion to improve the productivity, and suppressing deterioration of the moldability.

[0004] PRIOR ART DOCUMENTS

[0005] PATENT DOCUMENTS

[0006] Patent Document 1: Japanese Patent Laid-Open No. 10-157016 SUMMARY

[0007] PROBLEMS TO BE SOLVED BY THE INVENTION

[0008] The present application relates to a rubber product and a manufacturing method thereof, and more particularly to a rubber product having a cylindrical portion in which a plurality of reinforcing layers are embedded in a coaxial manner between an inner layer and an outer layer, and a manufacturing method thereof.

[0009] MEANS OF SOLVING THE PROBLEM

[0010] To achieve the above object, the rubber product of the present application is characterized in that it has a cylindrical portion in which a plurality of reinforcing layers are embedded in a coaxial stack between an inner layer and an outer layer, each of the reinforcing layers is composed of a cord fabric in which a plurality of fiber cords are aligned and a coating rubber layer which covers both surfaces of the cord fabric and is subjected to a prescribed adhesion treatment, and is a twill structure in which the fiber cords of the reinforcing layers extend in intersecting directions with each other, wherein, as each of the cord fabrics, a cord fabric of a specification in which the tensile strength in the fiber cord extension direction is 4320 N / cm or more and the weight is 950 g / m 2 the following specification, and the bending stiffness of each of the cord fabrics after the prescribed adhesion treatment is 30 g / cm or less, the layer thickness of each of the coating rubber layers is 0.2 mm or more and 1 mm or less in a neutral state in which the cylindrical portion is not inflated.

[0011] The manufacturing method of the rubber product of the present application is characterized in that a cylindrical shaped body in which a plurality of reinforcing layers are stacked coaxially between an inner layer and an outer layer is formed, each of the reinforcing layers is composed of a cord fabric in which a plurality of fiber cords are aligned and a coating rubber layer which covers both surfaces of the cord fabric and is subjected to a prescribed adhesion treatment, and is formed as a twill structure in which the fiber cords of the reinforcing layers extend in intersecting directions with each other, and the shaped body is vulcanized, thereby manufacturing a rubber product having a cylindrical portion in which a plurality of the reinforcing layers are embedded in a coaxial stack between the inner layer and the outer layer, wherein, as each of the cord fabrics, a cord fabric of a specification in which the tensile strength in the fiber cord extension direction is 4320 N / cm or more and the weight is 950 g / m 2 the following specification, and the bending stiffness of each of the cord fabrics after the prescribed adhesion treatment is 30 g / cm or less, the layer thickness of each of the coating rubber layers is 0.2 mm or more and 1 mm or less.

[0012] Effects of the Invention

[0013] According to the present application, by using a cord fabric of a specification in which the tensile strength in the fiber cord extension direction is 4320 N / cm or more as each of the cord fabrics, even if the number of layers of the reinforcing layers embedded in the cylindrical portion is reduced, it is easy to ensure sufficient pressure resistance against internal pressure acting on the rubber product. Thus, it is advantageous to improve the productivity of the rubber product. In addition, by making the weight of each of the cord fabrics 950 g / m 2 the following, and the bending stiffness of each of the cord fabrics after the prescribed adhesion treatment is 30 g / cm or less, it is advantageous to suppress a decrease in moldability when manufacturing the rubber product. Furthermore, by setting the layer thickness of each of the coating rubber layers to be 0.2 mm or more and 1 mm or less, it is easy to ensure sufficient joint strength while suppressing an increase in weight, and thus it is more advantageous to ensure pressure resistance while suppressing a decrease in moldability. Attached Figure Description

[0014] Figure 1 This is an explanatory diagram illustrating an inflatable fender material, which is a partial cut of the cylindrical part in its neutral state without expansion, and shown from a side view as an example of an embodiment of a rubber product.

[0015] Figure 2 Examples are given from a positive perspective. Figure 1 An explanatory diagram of the internal structure of the hemispherical part.

[0016] Figure 3 It is Figure 1 An explanatory diagram showing a partial enlargement of the cylindrical part and illustrating it from a cross-sectional perspective.

[0017] Figure 4 This is an illustrative diagram illustrating the reinforcing layer from a cross-sectional perspective that is orthogonal to and crosses the fiber cord.

[0018] Figure 5 This is an illustrative diagram showing curtain fabric from a top-down perspective.

[0019] Figure 6 (A) An example illustrates the manufacturing process of fiber cords. Figure 6 (B) is an illustrative diagram that schematically illustrates fiber cords from a cross-sectional perspective.

[0020] Figure 7 This is an illustrative diagram illustrating the vulcanization process of a molded body.

[0021] Figure 8 This involves cutting open a portion of the cylindrical section and illustrating it from a side view. Figure 1 An explanatory diagram of an inflatable fender that is pressurized to a specified internal pressure and expands into a specified shape.

[0022] Figure 9 This is an explanatory diagram showing a partially enlarged example of the improved cylindrical section from a cross-sectional perspective.

[0023] Figure 10 This is an explanatory diagram illustrating a marine hose as an example of a rubber product, showing a partial cut of the cylindrical portion and viewed from the side.

[0024] Figure 11 This is illustrated using a cross-sectional view. Figure 10 A partial explanatory diagram of the cylindrical section. Detailed Implementation

[0025] The following description, using the case of a rubber product as an inflatable fender material, will illustrate the rubber product and its manufacturing method according to the present invention based on the embodiments shown in the figures.

[0026] Figures 1 to 3 The pneumatic fender 1 (hereinafter referred to as fender 1) exemplified as an embodiment of a rubber product is provided with a main body 2 having a cylindrical portion 3a and hemispherical portions 3b connected to both ends of the cylindrical portion 3a, and a joint portion 11 provided on the main body 2. In this embodiment, the joint portion 11 is provided on only one of the hemispherical portions 3b, but can be provided on both of the hemispherical portions 3b. A single-dot chain line CL in the drawing indicates a cylinder axis of the cylindrical portion 3a, and an extension direction of the single-dot chain line CL is a cylinder axis direction.

[0027] In the cylindrical portion 3a, a plurality of cylindrical reinforcing layers 5 are embedded in a coaxial manner between a cylindrical inner layer 4 and a cylindrical outer layer 10. In this embodiment, six reinforcing layers 5 are laminated. That is, in the cylindrical portion 3a, the inner layer 4, each reinforcing layer 5, and the outer layer 10 are laminated in a coaxial manner. The number of laminated reinforcing layers 5 is determined by a required pressure resistance to internal pressure of the fender 1, and is, for example, about four or more and about twelve or less.

[0028] As Figure 4 , Figure 5 As exemplified, each reinforcing layer 5 is composed of a cord fabric 6 in which a plurality of fiber cords 7 are aligned, and a coating rubber layer 9 that covers both surfaces of the cord fabric 6. The fiber cords 7 are in a state of being filled with rubber of the coating rubber layer 9. As described later, the extension directions of the fiber cords 7 of the cylindrical portion 3a and each hemispherical portion 3b are different, and the cylindrical portion 3a is a twill structure, and each hemispherical portion 3b is a radial structure.

[0029] The cord fabric 6 is joined to the coating rubber layer 9 after a prescribed adhesion treatment. The prescribed adhesion treatment is a known adhesion treatment for improving the adhesion of the fiber cords 7 to rubber. Specifically, after an epoxy treatment liquid is applied to the fiber cords 7 and dried, a resorcinol-formaldehyde-latex (RFL) mixed liquid is applied and dried. The conditions of the adhesion treatment (the attached amounts of each liquid, the drying temperature, and the like) are set to an appropriate range in which a target adhesion (an adhesion that does not cause a problem in actual use) can be obtained by a preliminary test or the like.

[0030] As Figure 5 As exemplified, in the cord fabric 6, a plurality of fiber cords 7 extend in parallel, and a traverse cord 8 that traverses the fiber cords 7 is disposed at intervals in the extension direction of the fiber cords 7. The density (embedding density) of the fiber cords 7 is, for example, about 30 cords / 5 cm or more and about 70 cords / 5 cm or less.

[0031] Each of the cross cords 8 extends, for example, above and below the plurality of fiber cords 7 and extends in a direction orthogonal to the extending direction of the fiber cords 7. The density (embedding density) of the cross cords 8 arranged adjacent to each other is very small compared to the density of the fiber cords 7, for example, 2 or more and 8 or less per 5 cm.

[0032] As each of the cord fabrics 6, a fiber cord 7 having a tensile strength F in the extending direction of 4,320 N / cm or more and a weight W of 950 g / m 2 The following specifications of the cord fabric. The tensile strength F is measured based on the tensile strength test (A method) prescribed in JIS L1096, is a value obtained by dividing the breaking load of a test piece (300 mm long, 50 mm wide) of the cord fabric 6 by the width of the test piece. In this test, the tensile speed is 200 mm / min, and the clamping interval is 200 mm. Since the tensile strength F of a conventional cord fabric is less than 3,000 N / cm, the tensile strength F is greatly improved in this embodiment. The upper limit of the tensile strength F of the cord fabric 6 is, for example, 5,500 N / cm, and the lower limit of the weight W is, for example, 700 g / m 2 .

[0033] In addition, the bending stiffness H of each of the cord fabrics 6 after the above-described prescribed bonding treatment is 30 g / cm or less, more preferably 25 g / cm or less, and further preferably 20 g / cm or less. The lower limit of the bending stiffness H is, for example, 9 g / cm. In the present application, the bending stiffness H is a stiffness measured according to the Gurley bending test method prescribed in JIS L1096. Specifically, a test piece obtained by cutting the cord fabric 6 after the prescribed bonding treatment to a prescribed width is measured with the extending direction of the fiber cords 7 as the length direction, the measured value X (mg / cord) is multiplied by the embedding density (cords / 5 cm) of the fiber cords 7, the unit is set to (g / cm), and the bending stiffness H is calculated. The calculation formula of the bending stiffness H is as follows.

[0034] Bending stiffness H (g / cm) = Measured value X (mg / cord) x Embedding density (cords / 5 cm) / 5 / 1000 Figure 1As illustrated, in the cylindrical portion 3a, the extension direction of each fiber cord 7 is inclined relative to the cylindrical axis CL and is set to a predetermined cord angle A. Furthermore, the cylindrical portion 3a is formed as a diagonal weave structure in which the fiber cords 7 of the reinforcing layers 5 extend in intersecting directions. In this embodiment, in adjacent stacked reinforcing layers 5, the fiber cords 7 extend in intersecting directions. Specifically, in adjacent reinforcing layers 5, the cord angle A of the fiber cords 7 is substantially the same, and the inclination direction is set to opposite directions. Furthermore, in the stacked reinforcing layers 5, where one layer is spaced apart, the angle A of the fiber cords 7 is substantially the same, and the inclination direction is also set to the same direction. Therefore, the inclination direction of the fiber cords 7 in the 1st, 3rd, and 5th reinforcing layers 5 from the inner circumference side is the same, and the inclination direction of the fiber cords 7 in the 2nd, 4th, and 6th reinforcing layers 5 from the inner circumference side is the same.

[0035] In the neutral state where the cylindrical portion 3a is not expanded, the cord angle A of the fiber cords 7 of each reinforcing layer 5 is set to 25° or more and 45° or less. More preferably, the cord angle A is set to 30° or more and 35° or less.

[0036] Each hemispherical portion 3b is formed into a radial structure in which multiple fiber cords 7 extend radially around the cylindrical axis CL of the cylindrical portion 3a, and the multiple fiber cords 7 extend concentrically around the cylindrical axis CL of the cylindrical portion 3a.

[0037] As the fiber cord 7, known fiber cords such as polyester and nylon can be used. In the neutral state where the cylindrical part 3a is not expanded, the outer diameter of the fiber cord 7 (the thickness h of the fabric 6) is, for example, about 1 mm or more and about 1.5 mm or less.

[0038] The neutral state of the unexpanded cylindrical portion 3a refers to a state in which the fiber cords 7 of the cylindrical portion 3a are substantially without tension, and the interior of the main body 2 is filled with air, with an internal pressure slightly higher than atmospheric pressure (e.g., 10 kPa). Furthermore, this neutral state means that the cylindrical portion 3a maintains its cylindrical shape and the hemispherical portion 3b maintains its hemispherical shape. The outer diameter of the cylindrical portion 3a in this neutral state is, for example, approximately 2 m or more and 10 m or less.

[0039] like Figure 6As illustrated in the example, the fiber cord 7 is a twisted cord formed by twisting multiple strands 7a together. In this embodiment, the fiber cord 7 is formed by twisting multiple strands 7a with a fineness of 1670 dtex together. Two strands 7a are initially twisted in the same direction, and then three sets of these initially twisted two strands 7a are combined and re-twisted in the opposite direction, thereby forming the fiber cord 7. That is, the fiber cord 7 has a 1670 / 2 / 3 structure, and the total fineness D is 10020 (=1670×6 strands) dtex. The fiber cord 7 is not limited to this structure, as long as the fabric 6 meets the specifications of weight W, tensile strength F, and bending stiffness H mentioned above.

[0040] Because the fiber cord 7 has a multi-twist structure, it exhibits better fatigue resistance compared to a single-twist structure. The initial twist and subsequent twist can also be set to different twist values, but for stability, it is preferable to set them to the same or approximately the same twist value. Considering tensile strength, softness, etc., the total fineness D of the fiber cord 7 is approximately 10,000 dtex or more and 15,000 dtex or less, and the number of strands 7a to be twisted is, for example, 4 or more and 8 or less.

[0041] Preferably, the twist coefficient K is approximately 1300 or more and 2500 or less, as specified by the following formula (1). When the twist coefficient K is less than 1300, it is difficult to ensure sufficient durability, and when it exceeds 2500, it is difficult to ensure sufficient tensile strength. As a specific example, the twist coefficient T is approximately 10 or more and 20 or less.

[0042] Twist coefficient K = T × D 1 / 2 · · · (1)

[0043] T: Twist of fiber cord 7 (twist / 10cm)

[0044] D: Total fineness (dtex) of fiber cord 7

[0045] It should be noted that in this embodiment, the specifications of the transverse cord 8 are the same as those of the fiber cord 7, but they can also be set to different specifications.

[0046] The coated rubber layer 9 is formed of a known rubber, such as natural rubber, butyl rubber, butadiene rubber, styrene-butadiene rubber, acrylonitrile-butadiene rubber, or a mixture thereof. Adjacent stacked reinforcing layers 5 are bonded to each other via opposing coated rubber layers 9. The innermost reinforcing layer 5 and the inner layer 4 are bonded via the coated rubber layer 9 of the reinforcing layer 5. The outermost reinforcing layer 5 and the outer layer 10 are bonded via the coated rubber layer 9 of the reinforcing layer 5.

[0047] The thickness t of each coated rubber layer 9 is 0.2 mm or more and 1 mm or less in the neutral state of the cylindrical portion 3a without expansion. If the layer thickness t is less than 0.2 mm, it is difficult to ensure sufficient bond strength. If the layer thickness t exceeds 1 mm, the weight becomes too large and the molding processability is reduced. The layer thickness t is more preferably set to 0.2 mm or more and 0.6 mm or less.

[0048] For example, natural rubber, butyl rubber, styrene-butadiene rubber, acrylonitrile-butadiene rubber, etc., can be used as the rubber forming the outer layer 10. For example, natural rubber, styrene-butadiene rubber, acrylonitrile-butadiene rubber, ethylene propylene rubber, etc., can be used. In the neutral state where the cylindrical portion 3a is not expanded, the thickness of the inner layer 4 is, for example, about 2 mm or more and about 5 mm or less, and the thickness of the outer layer 10 is, for example, about 3 mm or more and about 12 mm or less.

[0049] Next, an example of the steps for manufacturing the fender 1 will be described.

[0050] By sequentially stacking components as outer layer 10, reinforcing layer 5, and inner layer 4 on the inner side of a known molding die, a structure is formed that... Figures 1 to 3 The example shown is a molded body 1A identical to the fender material 1. That is, a cylindrical molded body 1A is formed with multiple reinforcing layers 5 stacked coaxially between the inner layer 4 and the outer layer 10. Unlike the fender material 1, the molded body 1A contains uncured rubber.

[0051] Next, as Figure 7 As illustrated, the formed bag-shaped molded body 1 is placed inside a vulcanizing apparatus 14, such as a vulcanizing box. Next, the unvulcanized rubber constituting the molded body 1A is vulcanized through a vulcanization process performed by the vulcanizing apparatus 14 for a predetermined time, thereby firmly bonding the constituent parts of the molded body 1A together to form a single unit. As a result, a product is manufactured. Figures 1 to 3 Example of fender material 1.

[0052] When forming the molded body 1A, as described above, each curtain fabric 6 uses a tensile strength F of 4320 N / cm or more in the extension direction of the fiber cord 7 and a weight W of 950 g / m. 2 The following specifications are used for the curtain fabric. Furthermore, the bending stiffness H of the curtain fabric 6 after the above-specified bonding treatment is 30 g / cm or less. This bending stiffness H can be adjusted, for example, by changing the amount of RFL mixture adhered to the fiber cord 7. Additionally, the thickness t of each coated rubber layer 9 is set to 0.2 mm or more and 1 mm or less. This thickness t remains almost unchanged before and after the vulcanization process.

[0053] In this fender 1, since each fabric 6 is made of a cord fabric with a tensile strength F of 4320 N / cm or higher in the direction of fiber cord 7 extension, it is easy to ensure sufficient pressure resistance to the internal pressure acting on the fender 1 even if the number of reinforcing layers 5 embedded in the cylindrical portion 3a is reduced. That is, in order to obtain the same pressure resistance, the number of reinforcing layers 5 can be reduced compared to conventional fenders. For example, in the past, when using a cord fabric 6 with a tensile strength F of 2500 N / cm, in order to obtain the same pressure resistance, if a cord fabric 6 with a tensile strength F of 5000 N / cm is used, it may be necessary to set the number of reinforcing layers 5 to about half. In the molding process of the molded body 1A, the more reinforcing layers 5 are stacked, the more working time is required. Therefore, according to this embodiment, it is very advantageous to improve productivity while ensuring sufficient pressure resistance to the internal pressure of the fender 1.

[0054] In addition, by making the weight W of each curtain fabric 6 950g / m 2 Furthermore, by ensuring that the bending hardness H after the specified bonding treatment is 30 g / cm or less, the workload of moving and deforming the reinforcing layer 5 is reduced during the molding process of the molded body 1A. Increasing the thickness h (coarseness of the fiber cord 7) of the cord fabric 6 to ensure pressure resistance would lead to a decrease in molding processability, but by keeping the weight W and bending hardness H within the above-mentioned range, it is easy to stack the reinforcing layer 5 in the specified position to form a cylindrical shape, thus suppressing the decrease in molding processability.

[0055] Furthermore, by setting the thickness t of each coated rubber layer 9 to be 0.2 mm or more and 1 mm or less, it is easy to ensure sufficient bonding strength while suppressing weight increase. If the thickness t is large, it will be difficult to fully press the reinforcing layers 5 together, the reinforcing layers 5 and the inner layer 4, and the reinforcing layers 5 and the outer layer 10 during the molding process of the molded body 1A, and the uncured coated rubber layers 9 are prone to deformation. As a result, the molding processability will be reduced, but by keeping the thickness t within the above range, it is more beneficial to ensure pressure resistance while suppressing the reduction in molding processability.

[0056] When the fender 1 is not in use, such as during storage, handling, or installation, the internal pressure should be set to a low pressure, for example, around 10 kPa, and if... Figure 1 As illustrated, it is placed in a neutral state where the cylindrical portion 3a is not expanded. Furthermore, the air inside the main body 2 is expelled, causing it to fold.

[0057] When the fender 1 is installed at the installation site, such as Figure 8As illustrated, the cylindrical portion 3a is expanded and maintained in a predetermined shape. Specifically, air is introduced into the interior of the main body 2 through a valve located at the joint portion 11, raising the pressure to a predetermined internal pressure P used when the fender 1 is employed. The predetermined internal pressure P is, for example, approximately 50 kPa or more and 100 kPa or less.

[0058] During the process of filling the interior of the main body 2 with air to achieve a specified internal pressure P, in the cylindrical part 3a, the cord angle A of each reinforcing layer 5 is increased to a stable rest angle of about 54° to 55°. During this process, shear force acts on the coated rubber layer 9 sandwiched between the reinforcing layers 5 (cord fabric 6) where the fiber cords 7 extend in the intersecting direction, causing shear deformation.

[0059] When the cylindrical section 3a is in a neutral state, if the cord angle A is less than 25°, excessive shear stress will be generated in the coated rubber layer 9 in order to increase the cord angle A to about the stationary angle, which is not preferable. Therefore, the cord angle A is set to 25° or more, and more preferably to 30° or more. When the cord angle A is greater than 45°, the expansion of the diameter of the cylindrical section 3a will be smaller when the cylindrical section 3a is pressurized from the neutral state to the specified internal pressure P. Therefore, the cord angle is set to 45° or less, and more preferably to 35° or less.

[0060] When the pressure is increased to the specified internal pressure P, the outer diameter of the cylindrical part 3a can be approximately 120% to 150% of that in the neutral state. In addition, when the pressure is increased to the specified internal pressure P, the axial length of the main body 2 (cylindrical part 3a) is approximately 95% to 80% of that in the neutral state.

[0061] When the thickness t of the rubber coating layer 9 is less than 0.2 mm, the load on the rubber coating layer 9 caused by shear force during the expansion of the cylindrical part 3a will become too large. Furthermore, when the thickness t of the rubber coating layer 9 is 1 mm or more, the weight of the fender material 1 will become too large. Therefore, the thickness t of each rubber coating layer 9 is preferably set to 0.2 mm or more and 1 mm or less.

[0062] exist Figure 9 In the example fender 1, two stacked and adjacent reinforcing layers 5 form a group S (S1 to S4), and there are multiple groups S. In this embodiment, eight reinforcing layers 5 are stacked on the cylindrical portion 3a, forming four groups S. Each group S is composed of different reinforcing layers 5. The number of groups S is, for example, about three to six, and preferably multiple groups.

[0063] In each group S of the reinforcing layers 5, the fiber cords 7 of each reinforcing layer 5 extend in the same direction at a predetermined cord angle A. In stacked and adjacent groups S, the fiber cords 7 of the reinforcing layers 5 of both sides extend in a cross direction at a predetermined cord angle A. That is, in groups S1 and S2, the fiber cords 7 of the reinforcing layers 5 of both sides extend in a cross direction; in groups S2 and S3, the fiber cords 7 of the reinforcing layers 5 of both sides extend in a cross direction; and in groups S3 and S4, the fiber cords 7 of the reinforcing layers 5 of both sides extend in a cross direction. Therefore, in groups S1 and S3, the fiber cords 7 of the reinforcing layers 5 of both sides extend parallel; and in groups S2 and S4, the fiber cords 7 of the reinforcing layers 5 of both sides extend parallel. That is, on a unit S, the fiber cords 7 of the cylindrical portion 3a have a diagonal weave structure. When manufacturing the fender 1, a structure and Figure 9 The example shown is a molded body 1A with the same structure.

[0064] In this fender 1, during the process of filling the interior of the main body 2 with air to achieve a specified internal pressure P, in the cylindrical portion 3a, the cord angle A of the fiber cords 7 of each reinforcing layer 5 is increased to a stable rest angle of about 54° to 55°. In each group S, the fiber cords 7 of each reinforcing layer 5 extend in the same direction with a specified cord angle A, so the shear force does not actually act on the coated rubber layer 9 sandwiched between these reinforcing layers 5 (cord fabric 6).

[0065] On the other hand, since the fiber cords 7 of the reinforcing layers 5 of the stacked and adjacent groups S in the cylindrical portion 3a extend in a cross direction, shear force acts on the coated rubber layer 9 sandwiched between the groups S, causing shear deformation. As a result, when the cylindrical portion 3a is pressurized from a neutral state to a specified internal pressure P, the cord angle A of the fiber cords 7 of each reinforcing layer 5 in the cylindrical portion 3a increases to a stable rest angle of about 54° to 55°, causing the cylindrical portion 3a to expand and maintain a specified shape.

[0066] That is, when the cylindrical portion 3a expands, the shear force actually only acts on the coated rubber layers 9 sandwiched between the stacked and adjacent groups S. Therefore, compared with the case where the shear force acts on all the coated rubber layers 9, the resistance to expansion of the cylindrical portion 3a is reduced, which is conducive to the smooth expansion of the cylindrical portion 3a.

[0067] The implementation of rubber products is not limited to fender material 1, such as... Figure 10 , Figure 11As illustrated by the example, there is also a case where it is a marine hose 12. The marine hose 12 has flanges 13 at both ends in the longitudinal direction, and a cylindrical portion 3a extends between the flanges 13. In the cylindrical portion 3a, a plurality of reinforcing layers 5 are coaxially stacked and embedded between the inner layer 4 and the outer layer 10. The specifications of each reinforcing layer 5 are the same as in the previous embodiment. In the marine hose 12, the inner circumferential region of the inner layer 4 forms a flow path 12a. In a floating marine hose 12, a buoyancy layer is provided between the outer layer 10 and the reinforcing layers 5.

[0068] The marine hose 12 can be manufactured by forming a cylindrical body using the aforementioned components through known methods, and then vulcanizing the formed body using known methods. Similar to the embodiment of the fender 1, in this marine hose 12, even with a reduction in the number of layers of the reinforcing layer 5 embedded in the cylindrical portion 3a, sufficient pressure resistance to internal pressure is easily ensured, which is beneficial for improving the productivity of the marine hose 12. Furthermore, it helps to suppress the reduction in processability during the manufacture of the marine hose 12.

[0069] Example

[0070] As illustrated in Table 1, eight different types of curtain fabrics (conventional examples, Examples 1 to 5, and Comparative Examples 1 to 3) were prepared. After the aforementioned bonding treatment was performed, a reinforcing layer was manufactured by covering both surfaces of the curtain fabric with a rubber coating. Furthermore, each fiber cord 7 was a multi-twist structure with the same initial twist number and retwist twist T. The tensile strength F in the extension direction of the fiber cord 7 of each curtain fabric was measured, and the flexural stiffness H of each curtain fabric after the specified bonding treatment was measured. Additionally, for each reinforcing layer manufactured, fatigue resistance was evaluated using test pieces prepared under the same vulcanization conditions, as described below. The measurement and evaluation results are shown in Table 1.

[0071] [Table 1]

[0072]

[0073]

[0074] [Fatigue Resistance]

[0075] The fatigue strength of the disc was evaluated according to the Goodrich method as specified in Annex 1, Section 2.2.2 of JIS L1017 (2002). Fatigue tests were conducted using test pieces made from vulcanized reinforcing layers, i.e., rotating at 2400 rpm for 24 hours at room temperature with a strain ±10%. After the fatigue test, the fiber cords were removed from the test piece, and the tensile strength was measured. The retention rate of the tensile strength relative to the pre-fatigue test strength was calculated. A higher retention rate indicates better fatigue resistance.

[0076] Regarding the compressive strength in Table 1, when the tensile strength F is less than 4100 N / cm, it is evaluated as difficult to ensure sufficient compressive strength for each reinforcing layer, indicated by ×. When it is 4100 N / cm or higher, it is evaluated as sufficient compressive strength for each reinforcing layer, indicated by 〇. Furthermore, regarding the processability in Table 1, an operation was performed to adhere an unvulcanized reinforcing layer of a specified width to a forming roller of a specified outer diameter, evaluating the ease of adhesion and the deformation of the coated rubber layer after adhesion. A case where the adhesion operation can be performed very smoothly with minimal deformation of the coated rubber layer is evaluated as excellent processability, indicated by ◎. A case where the adhesion operation can be performed with minimal problems and the deformation of the coated rubber layer is at a level that is not problematic in practical use is evaluated as generally good processability, indicated by 〇. A case where at least one of the adhesion operation or the deformation of the coated rubber layer is at a level that is problematic in practical use is evaluated as poor processability, indicated by ×. In other words, the order of excellent processability is ◎, 〇, ×.

[0077] As can be seen from the results in Table 1, the reinforcing layers corresponding to Examples 1 to 5 exhibit excellent compressive strength and good formability. Furthermore, it can be seen that the fatigue resistance of the reinforcing layers corresponding to Examples 1 to 5 is equal to or better than that of the conventional examples, demonstrating good fatigue resistance.

[0078] Explanation of reference numerals in the attached figures

[0079] 1: Inflatable fender material

[0080] 1A: Molded body

[0081] 2: Main body

[0082] 3a: Cylindrical section

[0083] 3b: Hemispherical part

[0084] 4: Inner layer

[0085] 5: Reinforcement Layer

[0086] 6: Curtain fabric

[0087] 7: Fiber cord

[0088] 7a: Stock line

[0089] 8: Crossing the curtain wire

[0090] 9: Apply rubber layer

[0091] 10: Outer layer

[0092] 11: Connector

[0093] 12: Marine hoses

[0094] 12a: Flow path

[0095] 13: Flange portion

[0096] 14: Vulcanizing unit

[0097] A: Curtain angle

[0098] S(S1, S2, S3, S4): Group of enhancement layers

Claims

1. A rubber article comprising a cylindrical portion having a plurality of reinforcing layers coaxially stacked between an inner layer and an outer layer, each of the reinforcing layers comprising a fabric in which multiple fiber cords are aligned, transverse cords passing through the fiber cords are spaced apart and subjected to a predetermined bonding treatment, and a coated rubber layer covering both surfaces of the fabric, and having a diagonal weave structure in which the fiber cords of the reinforcing layers extend in a cross direction, wherein... As for each of the aforementioned curtain fabrics, the tensile strength in the extension direction of the fiber cords is 4320 N / cm or higher, and the weight is 950 g / m. 2 The curtain fabrics of the following specifications, wherein the bending hardness of each curtain fabric after the specified bonding treatment is less than 30 g / cm, and in the neutral state where the cylindrical portion is not expanded, the thickness of each of the coated rubber layers is more than 0.2 mm and less than 1 mm.

2. The rubber product according to claim 1, wherein, The rubber product is an inflatable fender or a marine hose.

3. The rubber product according to claim 1, wherein, The rubber product is an inflatable fender material. In the neutral state where the cylindrical part is not expanded, the cord angle of each fiber cord relative to the cylinder axis direction of the cylindrical part is set to be more than 25° and less than 45°. When the specified internal pressure is applied to the cylindrical part during the use of the rubber product, the cord angle of each fiber cord is more than 54° and less than 55°, causing the cylindrical part to expand and deform.

4. A method for manufacturing a rubber article, comprising forming a cylindrical body having a plurality of reinforcing layers coaxially stacked between an inner layer and an outer layer, each of the reinforcing layers consisting of a cord fabric in which multiple fiber cords are aligned, transverse cords are arranged at intervals in the extending direction of the fiber cords and subjected to a predetermined bonding treatment, and a coated rubber layer covering two surfaces of the cord fabric, and forming a diagonal weave structure in which the fiber cords of the reinforcing layers extend in a cross direction, and vulcanizing the article to produce a rubber article having a cylindrical portion having a plurality of reinforcing layers coaxially stacked and embedded between the inner layer and the outer layer, wherein... As for each of the aforementioned curtain fabrics, the tensile strength in the extension direction of the fiber cords is 4320 N / cm or higher, and the weight is 950 g / m. 2 The curtain fabrics are of the following specifications, and the bending hardness of each of the curtain fabrics after the specified bonding treatment is less than 30 g / cm, and the thickness of each of the coated rubber layers is more than 0.2 mm and less than 1 mm.

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