JPH0749449Y2 - Tensile body for optical cable - Google Patents

Description

TECHNICAL FIELD The present invention relates to a strength member used in an optical cable.

[Prior art and its problems]

Since the allowable elongation of the optical fiber is small, a tensile strength member is usually used for the optical cable to prevent the optical fiber from exceeding the specified elongation. It is desirable that this strength member is nonmetallic in order to take advantage of the non-induction characteristic of the optical fiber. Conventionally, G-FRP (glass fiber reinforced plastic) wire, polyaramid fiber and the like have been used as non-metallic strength members for optical cables.

Referring to the drawings, an example of using these is described. The optical cable of FIG. 2 is obtained by twisting a plurality of optical fiber core wires 2 around a G-FRP wire 1 and covering the outer circumference with a protective sheath 3. Is. The optical cable shown in FIG. 3 comprises a polyaramid fiber 4 vertically attached around the optical fiber core wire 2 and a protective sheath 3 covering the outer circumference thereof.

However, since the G-FRP wire is a glass fiber bundle integrally hardened with a thermosetting resin, the G-FRP wire has a large rigidity, and when it is used as an optical cable, it has a drawback of poor flexibility. Further, when a high tensile strength fiber such as polyaramid fiber is used, the flexibility of the optical cable is improved, but since the fiber is vertically attached as it is, there is a drawback that slack easily occurs and initial elongation occurs in the optical cable.

[Means for solving problems and their effects]

The present invention provides a strength member for an optical cable that solves the above-mentioned problems of the prior art, and has a structure in which a large number of uniaxially stretched filaments of ultra-high molecular weight polyethylene having a tensile elastic modulus (initial) of 30 GPa or more are used. The outer circumference of the main bundle of fibers is braided with the same fiber or different fibers to tighten the fiber bundle, and the fiber bundle and the braid layer are impregnated with a thermoplastic resin and solidified to integrate them. It is characterized by.

The ultra-high molecular weight polyethylene used in the present invention has an ultimate clay [η] at 135 ° C. in a decalin solvent of 5 dl / g or more, preferably 7 to 30 dl / g. When [η] is less than 5 dl / g, fiberization is easy, but even if stretched, a fiber having excellent tensile strength cannot be obtained. On the other hand, the upper limit of [η] is not particularly limited, but if it exceeds 30 dl / g, fiberization tends to be difficult. The above ultra high molecular weight polyethylene is obtained by polymerizing ethylene or ethylene and a small amount of other α-olefins such as propylene, 1-butene, 4-methyl-1-pentene, 1-hexene by a so-called medium-low pressure polymerization method. It has a much higher molecular weight than the polyethylene obtained.

The ultrahigh molecular weight polyethylene fibers used in the present invention are fibers having a high elastic modulus and high tensile strength in which the molecular chains of the above ultrahigh molecular weight polyethylene are highly oriented, tapes, or fibers defibrated from the tapes. . The method for producing fibers having such characteristics is not particularly limited, but ultrahigh molecular weight polyethylene as described in, for example, JP-A-56-15408 and JP-A-58-5228 is diluted with a solvent. After that, it can be prepared by a method of spinning and drawing, or a method disclosed in JP-A-59-108116 and JP-A-59-187614. The ultra high molecular weight polyethylene fiber used in the present invention has a tensile modulus (initial) of 30 GPa or more, preferably 50 GPa or more, more preferably about 70 GPa or more, and a tensile strength of 1.5 GPa or more, preferably 1.7 GPa or more, more preferably about 70 GPa or more. It is preferably 2.2 GPa or more and has an elongation of 6% or less, preferably 4% or less.

The method of gathering fibers is preferably rope twisting with a large twisting pitch, but they can also be gathered side by side in the same direction.

Braid tightens the fiber bundle to prevent the fiber bundle from breaking,
It is applied to give the fiber bundle an appropriate degree of rigidity,
The fiber used for this does not necessarily have a tensile modulus (initial) of 30 GP.
It need not be more than a.

Furthermore, when the voids in the fiber bundle and the braided layer are impregnated with a thermoplastic resin and solidified to integrate the whole, it is more effective in reducing the initial elongation.

〔Example〕

Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows an embodiment of the present invention. This tensile strength material for optical cables uses a uniaxially drawn filament of ultrahigh molecular weight polyethylene (Techumilon manufactured by Mitsui Petrochemical Co., Ltd.) as a fiber having a tensile elastic modulus (initial) of 30 GPa or more, and bundles a plurality of these fibers. The rope is twisted to form the fiber bundle 5,
A braid layer 6 made of polyester spun yarn is provided on the outer periphery of the braid layer 6. The tensile strength member 7 having such a structure has high tensile strength and excellent flexibility, and has an initial elongation of 0.2.
% Or less, which is very suitable for optical cables.

Further, the tensile strength member 7 having the above structure is impregnated with a thermoplastic resin [Chemipearl S-100 manufactured by Mitsui DuPont Co., Ltd. (a polyolefin aqueous dispersion, the resin is an ionomer resin)] and solidified, so that the flexibility is almost impaired. The initial elongation is 0.1% or less, which is even better.

[Effect of device]

As described above, the tensile strength body according to the present invention is obtained by braiding the same fiber bundle or different fibers on the outer periphery of a fiber bundle in which a large number of fibers having a tensile elastic modulus (initial) of 30 GPa or more are assembled. Since it has a structure in which the fiber bundle and the braided layer are fastened together and impregnated with a thermoplastic resin to be solidified and integrated, there is an advantage that the tensile strength is high, the flexibility is excellent, and the initial elongation is extremely small. It is very suitable for the strength member of the optical cable.

[Brief description of drawings]

FIG. 1 is a side view showing a part of a strength member for an optical cable according to an embodiment of the present invention in a stepped-off state, and FIGS. 2 and 3 are sectional views of a conventional optical cable. 5 ... fiber bundle, 6 ... braided layer, 7 ... tensile body for optical cable.

Claims (1)

[Scope of utility model registration request] 1. A fiber bundle comprising a large number of uniaxially drawn filaments of ultra-high molecular weight polyethylene having a tensile elastic modulus (initial) of 30 GPa or more, is braided with the same fiber or different fibers around the outer periphery of the fiber bundle, and the fiber bundle is tightened. A tensile strength body for an optical cable, characterized in that the fiber bundle and the braided layer are integrated by being impregnated with a thermoplastic resin and solidified therein.