Twisted cord for tension members

Abstract

To provide a twisted yarn cord for a tension member, which can achieve functionality of a tension member, protective property of an optical fiber, connector work efficiency, productivity, economical efficiency at high level without resin impregnation.SOLUTION: A twisted yarn cord for tension member is used for reinforcement of an optical fiber cable. The twisted yarn cord is composed of organic fibers. The organic fiber has 700 cN / dtex or more of elongation modulus measured by a method described in JIS L1013. The twisted yarn cord has 0.2 to 1.4 of twist coefficient (TM) defined by a formula (I), and 90.0% or more of retention of elongation modulus before and after twisting yarn. In the formula (I), TM: twist coefficient; T: twit number (t / 10 cm); D: total fineness (dtex).SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a twisted cord for a tension member used to reinforce an optical fiber cable. [Background technology]

[0002] Optical fiber cables are designed so that tension and thermal expansion forces applied to the cable during manufacturing, installation, or after installation are borne by tension members, preventing stress from being applied to the optical fiber.

[0003] Conventional tension members are primarily made of metal materials such as steel wire, so when lightning strikes, lightning current flows through them, causing sparks and destroying the cable, or eddy currents travel through the metal in the cable, potentially causing damage to transmission equipment.In recent years, tension members have been made of non-metallic fiber-reinforced plastic, making them suitable for lightning protection and use in strong magnetic fields.However, when fiber-reinforced plastic comes into contact with the core wire inside an optical fiber cable, the optical fiber itself, which is made of silica-based glass, can be damaged.

[0004] To address the above issues, organic fibers are nonmetallic, highly elastic, and do not damage the other components, making them an advantageous material in terms of functionality as a tension member and protecting the optical fiber. However, as shown in Figure 1, when removing the optical fiber from the optical fiber cable and connecting it to a connector, the single yarns of aramid fiber 10 can become entangled with the assembled core (core) 20, reducing work efficiency.

[0005] The above problem is particularly pronounced in optical fiber cables, particularly in multi-core cables, where many optical fibers 40 are arranged around a tension member 30 inside the cable, as shown in Figure 2. Furthermore, with the recent demand for small-diameter multi-core cables, there is also a need to reduce the space required for tension members.

[0006] Patent Document 1 proposes an optical fiber cable that does not bend or break even when bent by using a single stranded wire made by gathering multiple aramid fiber bundles and twisting them in one direction as a tension member. However, because multiple aramid fiber bundles are twisted together, there is a problem in that the diameter of the stranded wire becomes large.

[0007] Patent Document 2 proposes a tensile strength member in which the outer layer of a multifilament long fiber is coated with a thermoplastic resin of uniform thickness. However, because the thermoplastic resin is coated, it is necessary to avoid contact with the core wires in the cable, and it is also necessary to coat the resin to a uniform thickness from the extrusion molding machine, which results in poor productivity.

[0008] Patent Document 3 proposes using a core-sheath composite fiber cord, in which the core component is a molten liquid crystal polymer and the sheath component is a thermoplastic polymer, as a tension member. However, the fiber cord, which is largely responsible for the mechanical properties, has a low modulus of elasticity per cord, and therefore insufficient rigidity.

[0009] Patent Document 4 proposes that the strength members be made of non-conductive tensile fiber yarns, and that the yarns be twisted when the core wire and the strength members are covered with the resin of the cable sheath, and used as the strength members of an optical fiber drop cable. However, there is no specification for the elastic modulus of the tensile fiber, and it is unclear whether a sufficient effect can be achieved. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] Japanese Patent Application Publication No. 2019-211585 [Patent Document 2] Japanese Patent Application Laid-Open No. 2006-111999 [Patent Document 3] Japanese Patent Application Laid-Open No. 2004-270051 [Patent Document 4] Japanese Patent Application Laid-Open No. 2003-121714 Summary of the Invention [Problem to be solved by the invention]

[0011] The present invention has been made in view of the above circumstances, and aims to provide a twisted yarn cord for a tension member that can simultaneously satisfy high levels of tension member functionality, optical fiber protection, connector work efficiency, productivity, and space saving without the need for resin impregnation. [Means for solving the problem]

[0012] The present inventors have conducted extensive research to achieve the above object, and as a result have discovered that by controlling the twist factor of organic fibers having a certain or higher elongation modulus in optical fiber cables, it is possible to provide a twisted cord for tension members that is excellent in the functionality of the tension member, protection of the optical fiber, connector work efficiency, productivity, and space saving, and have arrived at the present invention.

[0013] That is, the present invention provides: A twisted cord for a tension member used to reinforce an optical fiber cable, The twisted cord is made of organic fibers selected from aramid fibers and liquid crystal polyester fibers and having a total fineness of 100 to 5,000 dtex. In a single fiber bundle of It is composed of The organic fiber has an elongation modulus of 700 cN / dtex or more as measured by the method described in JIS L1013, The twisted yarn cord has a twist factor (TM) defined by the following formula (I) in the range of 0.2 to 1.4, and the retention of the elongation modulus before and after twisting is 90.0% or more. The present invention provides a twisted yarn cord for a tension member characterized by the above-mentioned. TM=T×√D / 303 (I) Where TM: twist coefficient, T: number of twists (t / 10cm), D: total fineness (dtex) [Effects of the Invention]

[0014] According to the present invention, it is possible to provide a twisted yarn cord for a tension member in an optical fiber cable, which can achieve high levels of both the functionality of the tension member and the protection of the optical fiber without resin impregnation, and which is also excellent in terms of terminal processing workability, productivity, and space saving when extracting the optical fiber and connecting it to a connector. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 1 is a photograph showing how aramid fiber bundles are entangled with a collective core. [Figure 2] 1 is a cross-sectional schematic diagram of an example of a multi-core cable. DETAILED DESCRIPTION OF THE INVENTION

[0016] Hereinafter, embodiments of the present invention will be described in detail. The twisted yarn cord for a tension member according to the present invention is made of organic fibers, and the organic fibers have an elongation modulus of elasticity of 700 cN / dtex or more as measured by the method described in JIS L1013. The twisted yarn cord has a twist coefficient (TM) defined by the following formula (I) in the range of 0.2 to 1.4, and a retention rate of the elongation modulus before and after twisting of 90.0% or more. Characterized by

[0017] JPEG0007781104000001.jpg15160In formula (I), TM is the twist coefficient, T is the number of twists (t / 10 cm), and D is the total fineness (dtex).

[0018] <Organic fiber> Examples of organic fibers used in the present invention include those selected from aramid (wholly aromatic polyamide) fibers, polyphenylene sulfide fibers, polyimide fibers, polyparaphenylene benzobisoxazole fibers, polyparaphenylene benzobisthiazole fibers, polyether ether ketone fibers, polytetrafluoroethylene fibers, high-strength polyethylene fibers, liquid crystal polyester fibers, polyarylate fibers, etc. Long fibers of these organic fibers are used.

[0019] Among these, organic fibers having an elongation modulus of 700 cN / dtex or more, measured by the method described in JIS L1013:2021 "Testing methods for chemical fiber filament yarns" 8.9 Elongation modulus, are used. If the elongation modulus is small, when used as a tension member, there is a possibility that the fiber will break when bent to a small diameter, and the optical fiber cable may lose its tensile strength function.

[0020] The elongation modulus of the organic fiber is preferably 750 cN / dtex or more, more preferably 780 cN / dtex or more. Specifically, it is preferable to use aramid (wholly aromatic polyamide) fiber, polyparaphenylene benzobisoxazole fiber, high-strength polyethylene fiber, liquid crystal polyester fiber, or polyarylate fiber.

[0021] The aramid fiber is a fiber having at least one divalent aromatic group, which may be substituted, in the repeating unit of the polymer forming the fiber, and is not particularly limited as long as it has at least one amide bond, and includes what is called a wholly aromatic polyamide fiber or an aramid fiber. The "divalent aromatic group, which may be substituted," means a divalent aromatic group, which may have one or more identical or different substituents.

[0022] Examples of aramid fibers include para-aramid fibers and meta-aramid fibers, with para-aramid fibers being preferred due to their excellent tensile properties. Aramid fibers are also commercially available, and specific examples of para-aramid fibers include polyparaphenylene terephthalamide fibers (manufactured by DuPont-Toray Co., Ltd., trade name "Kevlar" (registered trademark)) and copolyparaphenylene-3,4'-oxydiphenylene terephthalamide fibers (manufactured by Teijin Limited, trade name "Technora" (registered trademark)).

[0023] Among the para-aramid fibers, polyparaphenylene terephthalamide fibers (hereinafter sometimes abbreviated as "PPTA") are particularly preferred because they are resistant to radial compression and suffer little loss in strength even when twisted together.

[0024] The liquid crystalline polyester constituting the liquid crystalline polyester fiber is a polyester that can form an anisotropic molten phase (liquid crystallinity) when melted. This property can be confirmed, for example, by placing a sample on a hot stage, heating it under a nitrogen atmosphere, and observing the transmitted light through the sample under polarized light.

[0025] Examples of liquid crystal polyesters include (i) polymers of aromatic hydroxycarboxylic acids, (ii) polymers of aromatic dicarboxylic acids and diols selected from aromatic diols or aliphatic diols, and (iii) copolymers of the above (i) and (ii), which are produced by conventionally known methods. Among the above (co)polymers, those composed only of aromatic compounds are preferred. A (co)polymer composed only of aromatic compounds exhibits excellent strength and elastic modulus when made into fibers.

[0026] Examples of the aromatic oxycarboxylic acid include hydroxybenzoic acid, hydroxynaphthoic acid, etc., and alkyl, alkoxy, and halogen-substituted derivatives thereof. Examples of the aromatic dicarboxylic acid include terephthalic acid, isophthalic acid, diphenyldicarboxylic acid, naphthalenedicarboxylic acid, diphenyletherdicarboxylic acid, diphenoxyethanedicarboxylic acid, diphenylethanedicarboxylic acid, etc., and alkyl, alkoxy, and halogen-substituted derivatives thereof. Examples of the aromatic diol include hydroquinone, resorcinol, dihydroxybiphenyl, naphthalenediol, etc., and alkyl, alkoxy, and halogen-substituted derivatives thereof. Examples of the aliphatic diol include ethylene glycol, propylene glycol, butanediol, and neopentyl glycol.

[0027] Examples of commercially available liquid crystal polyester fibers include "Zexion (registered trademark)" manufactured by KB Seiren Co., Ltd., "Vectran (registered trademark)" manufactured by Kuraray Co., Ltd., and "Sumikasuper (registered trademark) LCP" manufactured by Sumitomo Chemical Co., Ltd.

[0028] Furthermore, the organic fiber preferably has a tensile strength of 17 cN / dtex or more, as measured in accordance with JIS L1013:2021 "Test Methods for Chemical Fiber Filament Yarns," Section 8.5, "Tensile Strength and Elongation." By using organic fibers with these characteristics, the strength of the tension member is sufficient. The tensile strength of the organic fiber is preferably 19 cN / dtex or more, and more preferably 20 cN / dtex or more.

[0029] The organic fiber bundles constituting the twisted cord preferably have a total fineness of 50 to 10,000 dtex. In a multi-core cable, the insertion space for the tension member is small, so a relatively thin tension member is desirable. For this reason, it is desirable to use organic fiber bundles with a small total fineness. The total fineness is more preferably 100 to 5,000 dtex, even more preferably 200 to 4,000 dtex, and particularly preferably 400 to 3,300 dtex.

[0030] The twisted cord used to reinforce the optical fiber cable of the present invention is preferably composed of a single fiber bundle of organic fibers. By using a single fiber bundle, the diameter of the twisted cord can be reduced, making it easier to insert into the tension member insertion space of a multi-core cable. Furthermore, using a single fiber bundle minimizes the disruption of the yarns caused by doubling, thereby preventing the problem of the organic fiber single yarns becoming entangled with the assembled core (core wire) when the optical fiber is removed from the optical fiber cable and connected to a connector. In this regard, organic fibers with an elongation modulus of elasticity of 700 cN / dtex or more, when composed of a single fiber bundle, are suitable for use as a tension member that can accommodate small diameter multi-core cables. The number of single fibers constituting a single fiber bundle is preferably 30 to 4,500 filaments, more preferably 60 to 3,500 filaments, and particularly preferably 200 to 3,000 filaments.

[0031] The organic fiber bundles in the present invention are preferably not resin-impregnated or resin-coated, and are not composite yarns with other fiber bundles. However, if necessary, the organic fiber bundles may be air-entangled to impart a certain degree of bundling ability, or may be separated into yarns using the organic fiber bundles in order to specialize in space saving.

[0032] In the case of a resin-impregnated or resin-coated structure, the resin is present on the surface of the tension member, and if this resin comes into contact with the core wire inside the optical fiber cable, it may damage the core wire itself and impair the protective function of the optical fiber. Also, in the case of a structure made of a composite yarn with other fiber bundles, the total fineness increases, which increases the overall cord diameter and may not fit into the space in the tension member. In addition, a new production process is required to create the composite yarn, which is thought to be low in productivity.

[0033] <Twist Form> The organic fiber twisted cord used to reinforce the optical fiber cable of the present invention is preferably twisted to align the organic fiber single yarns that make up the organic fiber thread and improve connector work efficiency. It is essential that the twist factor defined by the above formula (I) be 0.2 to 1.4. If the twist factor exceeds 1.4, the increased twist angle will significantly reduce the modulus of elasticity of the twisted cord. Furthermore, if the twist factor is less than 0.2, the multifilaments that make up the fiber bundle may unravel, potentially becoming tangled with the assembled core during connector work and making it difficult to separate.

[0034] The twist coefficient is preferably 0.3 to 1.3, more preferably 0.4 to 1.2, and even more preferably 0.5 to 1.1.

[0035] The organic fibers constituting the twisted cord of the present invention must function as a tension member even after twisting. Therefore, it is desirable that the decrease in elongation modulus after twisting be minimized. It is essential that the elongation modulus be maintained at 90.0% or higher before and after twisting. The elongation modulus is preferably maintained at 92.0% or higher, and more preferably at 94.0% or higher.

[0036] The twist form is preferably single twist (twisting in one direction), and the twist direction may be either S direction or Z direction. By using single twist, the bundling ability of the organic fiber bundle can be maintained without increasing the cord diameter.

[0037] The oil applied to the surface of the organic fiber used in the present invention may be a known oil. Examples include fatty acid esters, polyoxyethylene-polyoxypropylene copolymers or derivatives thereof, and mineral oils. The oil may contain an epoxy compound. Among these, fatty acid esters can suppress the generation of scum caused by friction with each guide during the twisting process, thereby making it possible to provide a high-quality twisted cord.

[0038] The moisture content of the organic fibers constituting the twisted cord of the present invention is not particularly limited, but is usually less than 15% by mass. The moisture content of the organic fibers is preferably less than 10% by mass, more preferably less than 7% by mass. Since highly elastic materials are generally required for tension members, it is desirable to use organic fibers that have been dried at a sufficiently high temperature in the spinning process to increase the degree of crystallinity within the fibers. It is particularly preferable that the moisture content of the organic fibers be less than 5% by mass.

[0039] <Optical fiber cable> When applying the twisted yarn cord for tension members of the present invention to optical cables, the application method is not particularly limited and any known method may be followed. Among these, by adopting a slot-type structure with a tension member at the center of the cable, it is possible to realize an optical cable with excellent flexibility and no bending directionality.

[0040] The twisted cord for tension members of the present invention can be incorporated into various optical fiber cables, and the type of optical fiber cable is not particularly limited. The twisted cord, which has a high retention rate of elongation modulus, can exert sufficient tensile strength even in small-diameter cables, making it most useful for multi-fiber optical fiber cables. A multi-core optical fiber cable contains many core wires, but by using the twisted cord of the present invention, the space required for the tension member is small and there is no need to separate the core wires and tension member when connecting the connector, making it suitable for use. [Example]

[0041] The present invention will be described in more detail below with reference to examples, but the present invention is not limited thereto. In the following examples, "parts by weight" will be abbreviated to "parts" unless otherwise specified. The evaluation methods described in the examples are as follows.

[0042] (1) Moisture content of organic fibers (mass%) The mass of approximately 5 g of the sample was measured, treated at 105°C for 4 hours, and then left to stand at 24°C and 55% RH for 5 minutes. The mass was then measured again and the dry basis moisture content was calculated using the following formula. Moisture content = ([mass before drying - mass after drying] / [mass after drying]) × 100

[0043] (2) Tensile properties of organic fibers The tensile strength was measured according to 8.5 tensile strength of JIS L1013:2021 "Testing methods for chemical fiber filament yarns."

[0044] (3) Elongation modulus of twisted cord The elongation modulus was measured by pulling the yarn at a grip distance of 25 cm and a pulling speed of 30 cm / min according to JIS L1013:2021 "Testing Methods for Chemical Fiber Filament Yarns" 8.9 Elongation Modulus B. The initial load in the measurement was the cord fineness design value (dtex) x 0.45 mN.

[0045] (4) Retention of twisted cord elongation modulus According to the method of 8.9 Elongation modulus of elasticity of JIS L1013:2021 "Testing methods for chemical fiber filament yarns," the retention rate (R) is calculated using the following formula from the measured elongation modulus of elasticity before and after twisting. R = B / A × 100 A: Elongation modulus before twisting (cN / dtex) B: Elongation modulus after twisting (cN / dtex) R: Retention rate (%)

[0046] (5) Connector work efficiency The connector work efficiency was evaluated as follows based on the occurrence of entanglement between the organic fiber single yarn and the aggregate core during the connector connection process of the optical fiber cable. 〇: No entanglement with the aggregate core ×: Entanglement with aggregate core

[0047] (6) Functionality of the tension member The evaluation was made based on the magnitude of the elongation modulus (X) of the twisted yarn cord as follows: ○: The magnitude of the elongation modulus of the twisted yarn cord (X) is 700 cN / dtex or more ×: The magnitude (X) of the elongation modulus of the twisted yarn cord is less than 700 cN / dtex

[0048] [Manufacturing Example 1] 1 kg of paraphenylene terephthalamide (molecular weight approximately 20,000) obtained by a conventional method was dissolved in 4 kg of concentrated sulfuric acid, and the solution was passed through a nozzle with 768 holes of 0.1 mm diameter at a shear rate of 30,000 sec -1 The mixture was discharged so that the temperature became equal to that of the original fiber, and spun into water at 4°C. The mixture was then neutralized with a 10% by weight aqueous solution of sodium hydroxide at 10°C for 15 seconds. After that, the mixture was heated and dried at 190°C for 15 seconds, and then further heated and dried at 220°C for 10 seconds. An oil solution was then applied to the mixture, and a bundle of polyparaphenylene terephthalamide fibers (total fineness 1,270 dtex) with a moisture content of 3.5% by weight was obtained.

[0049] [Manufacturing Example 2] 1 kg of paraphenylene terephthalamide (molecular weight approximately 20,000) obtained by a conventional method was dissolved in 4 kg of concentrated sulfuric acid, and the solution was passed through a die with 1,333 holes of 0.1 mm diameter at a shear rate of 30,000 sec -1 The mixture was discharged so that the temperature became equal to that of the original fiber, and spun into water at 4°C. The mixture was then neutralized with a 10% by weight aqueous solution of sodium hydroxide at 10°C for 20 seconds. After that, the mixture was heated and dried at 200°C for 20 seconds, and then further heated and dried at 240°C for 15 seconds. An oil solution was then applied to the mixture, and a bundle of polyparaphenylene terephthalamide fibers (total fineness 3,160 dtex) with a moisture content of 3.0% by weight was obtained.

[0050] [Manufacturing Example 3] 1 kg of paraphenylene terephthalamide (molecular weight approximately 20,000) obtained by a conventional method was dissolved in 4 kg of concentrated sulfuric acid, and the solution was passed through a die with 1,000 holes of 0.1 mm diameter at a shear rate of 30,000 sec -1The mixture was discharged so that it became a fine fiber, and spun into water at 4°C. The fiber was then neutralized with a 10% by weight aqueous solution of sodium hydroxide at 10°C for 10 seconds. The fiber was then dried by heating at 180°C for 10 seconds, and an oil was then applied to the fiber to obtain a bundle of polyparaphenylene terephthalamide fibers (total fineness 1,670 dtex) with a moisture content of 7.0% by weight.

[0051] [Manufacturing Example 4] Kuraray's "Vectran UM" (liquid crystal polyester fiber; 1,580 dtex) was used.

[0052] Details of the polyparaphenylene terephthalamide fibers obtained in Production Examples 1 to 3 and the liquid crystal polyester fiber obtained in Production Example 4 are shown in Table 1.

[0053] [Table 1]

[0054] [Example 1] Using one polyparaphenylene terephthalamide fiber (Production Example 1) shown in Table 1, an aramid fiber single-twisted cord was obtained with a twist number of 4.3 (t / 10 cm) in the Z direction.

[0055] [Example 2] Using one polyparaphenylene terephthalamide fiber (Production Example 2) shown in Table 1, an aramid fiber single-twisted cord was obtained with a twist number of 5.9 (t / 10 cm) in the Z direction.

[0056] [Example 3] Using one liquid crystal polyester fiber (Production Example 4) shown in Table 1, a liquid crystal polyester fiber single twist cord was obtained with a twist number of 5.3 (t / 10 cm) in the Z direction.

[0057] [Comparative Example 1] Using one polyparaphenylene terephthalamide fiber (Production Example 1) shown in Table 1, an aramid fiber single-twisted cord was obtained with a twist number of 0.9 (t / 10 cm) in the Z direction.

[0058] Comparative Example 2 Using one polyparaphenylene terephthalamide fiber (Production Example 2) shown in Table 1, an aramid fiber single-twisted cord was obtained with a twist number of 9.7 (t / 10 cm) in the Z direction.

[0059] Comparative Example 3 Using one polyparaphenylene terephthalamide fiber (Production Example 3) shown in Table 1, an aramid fiber single-twisted cord was obtained with a twist number of 8.2 (t / 10 cm) in the Z direction.

[0060] [Examples 1 to 3, Comparative Examples 1 to 3] Table 2 shows the evaluation results for the twisted yarn cords for tension members made from each of the fiber types listed in Table 1.

[0061] [Table 2]

[0062] As shown in Table 2, a twisted cord for a tension member with a twist coefficient of less than 0.2 cannot improve connector workability (Comparative Example 1). On the other hand, if the twist coefficient exceeds 1.4, the tensile modulus of elasticity in the twisted cord drops significantly, and the functionality of the tension member cannot be fully exhibited (Comparative Example 2). On the other hand, even if the twist coefficient is within the range of 0.2 to 1.4, a twisted cord in which the tensile modulus of elasticity of the organic fiber before twisting is less than 700 cN / dtex also cannot fully exhibit the functionality of the tension member (Comparative Example 3).

[0063] In contrast, the twisted cord for tension members of the present invention uses organic fibers with a high tensile modulus, and by controlling the twist coefficient of the twisted cord, it is possible to improve the work efficiency in connector processing while maintaining the functionality of the tension member, demonstrating the usefulness of the present invention. [Industrial Applicability]

[0064] The twisted cord for a tension member of the present invention is most suitable for use as a tension member in an optical fiber cable, particularly in a multi-core cable. [Explanation of symbols]

[0065] 10 Aramid fiber 20 core wires 30 tension members 40 Optical Fiber 50 sheath

Claims

1. A twisted cord for a tension member used to reinforce an optical fiber cable, the twisted cord is composed of a single fiber bundle of organic fibers selected from aramid fibers and liquid crystal polyester fibers and having a total fineness of 100 to 5,000 dtex, The organic fiber has an elongation modulus of 700 cN / dtex or more as measured by the method described in JIS L1013, The twisted yarn cord has a twist factor (TM) defined by the following formula (I) in the range of 0.2 to 1.4, and the retention of the elongation modulus before and after twisting is 90.0% or more. A twisted cord for a tension member characterized by: TM=T×√D / 303...(I) where TM is twist coefficient, T is twist number (t / 10 cm), and D is total fineness (dtex).

2. 2. The twisted yarn cord for a tension member according to claim 1, wherein the twisted yarn cord is a single twisted cord of S twist or Z twist.

3. A tension member using the twisted yarn cord for tension members according to any one of claims 1 and 2.

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