JP2617303B2 - Optical fiber submarine cable - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an optical fiber submarine cable having excellent mechanical properties.

[Conventional technology]

Optical fibers have advantages such as low loss, wide band, small diameter, light weight, flexibility, non-induction, no crosstalk and resource saving, and are also used for submarine cables.

However, the optical fiber is made of quartz glass and is therefore inherently brittle, and transmission characteristics change when an external pressure such as a lateral pressure is applied. Therefore, a cable-forming technique different from a metal cable is required to compensate for this drawback.

For this reason, it has sufficient mechanical properties to withstand the tension applied when laying the optical fiber submarine cable on the site, and furthermore, against various stresses and strains received during long-term use of the optical fiber submarine cable in the site environment. It is important to ensure long-term reliability.

Conventionally, various types of optical fiber submarine cables have been proposed.
There are those as shown in FIG. 2, FIG. 2 and FIG.

Fig. 1 is Japanese Patent Application No. 56-75604, and Fig. 2 is Japanese Patent Application No. 53-365.
No. 80 and FIG. 3 show optical fiber submarine cables described in Japanese Patent Application No. 56-146102, respectively.

Although these optical fiber submarine cables differ in details, they are commonly used as an optical fiber unit (indicated by 1 in the figure), an inner tubular conductor (indicated by 2 in the figure), and a steel wire (in the figure). 3), an outer tubular conductor (shown by 4 in the figure), an insulating layer (shown by 5 in the figure), a jacket (shown by 6 in the figure), and the like.

Each component of the conventional optical fiber submarine cable is configured as follows to suppress the stress and strain on the optical fiber of the optical fiber submarine cable to an allowable range, and to supply power for driving the optical repeater. I have.

That is, the optical fiber unit 1 is formed by gathering at least one or more core wires around a single steel wire and forming a solid shape with an elastic body such as polyurethane or epoxy resin, so that stress relaxation does not occur even when an external force is applied. The optical fiber group is placed in the inner tubular conductor 2 so as to be protected from side pressure and water pressure, and the steel wire 3 is placed between the inner tubular conductor 2 and the outer tubular conductor 4. By inserting the cable, the cable elongation due to untwisting of the steel wire 3 is suppressed. The use of the inner tubular conductor 2 and the outer tubular conductor 4 supplies power for driving the optical repeater.

For this purpose, they are made of a material that easily conducts electricity, such as copper or aluminum. The outer tubular conductor 4 protects the optical fiber from lateral pressure and water pressure.

The insulating layer 5 insulates between the outer tubular conductor 4 and seawater, and is made of a low-density polyethylene resin usually manufactured by a high-pressure method from the viewpoint of cost, performance, coating workability and the like.

The outer cover 6 is provided to protect an insulating layer which is easily damaged by external force, and is usually made of a high-density polyethylene resin.

[Problems to be solved by the present invention]

However, as described above, in the conventional optical fiber submarine cable, although a low-density polyethylene resin by a high-pressure method is used as an insulating layer to insulate the outer tubular conductor from seawater, an outer tubular conductor made of aluminum or copper is used. Low-density polyethylene has insufficient adhesion and causes various problems.

That is, if the adhesiveness between the outer tubular conductor 4 and the insulating layer 5 is poor, when a tension or bending force is applied to the cable, the outer tubular conductor 4 and the insulating layer 5 are separated and move separately, and the insulating layer is moved by the cable. It breaks on the way or at the end of the cable, and eventually leads to breakage of the cable itself.

That is, when the cable is damaged or cut by an external force on the seabed, it takes time to pull up and repair the cable, and the adhesion between the outer tubular conductor 4 and the insulating layer 5 is poor, so that seawater enters the gap between the two. However, not only the damaged or cut portion, but also the interface between them, which is away from the damaged or cut portion, destroys the function of the cable and renders the cable unusable.

Therefore, the present invention solves the above-mentioned problem of the conventional optical fiber submarine cable having a structure in which the outer tubular conductor 4 and the insulating layer 5 have insufficient adhesion and adhesion, and is hardly damaged or cut. An object of the present invention is to provide an optical fiber submarine cable having a structure in which damage to a cable remains at a damaged or cut portion even if a break occurs, and the damage does not propagate.

[Means for solving the problem]

The present invention relates to an optical fiber submarine cable comprising an optical fiber unit 1, an inner tubular conductor 2, a steel wire 3, an outer tubular conductor 4, an insulating layer 5, an outer jacket 6, and the like shown in FIGS. 1, 2 and 3. (A) a high-pressure method low-density polyethylene resin; and (b) an unsaturated carboxylic acid or a linear ethylene-α-olefin copolymer produced by a gas-phase / low-pressure method having a density of 0.91 or more. 80 to 40% by weight of a modified ethylene-α-olefin copolymer obtained by grafting the acid anhydride and an ethylene-ethyl acrylate copolymer or the above unsaturated carboxylic acid or the acid anhydride thereof. The above problem is solved by using a resin composition comprising a modified ethylene copolymer composition comprising 20 to 60% by weight of a partially grafted copolymer.

The configuration of the optical fiber submarine cable of the present invention is shown in FIGS. 1, 2 and 3, and the like. The feature of the configuration of the present invention resides in that a specific resin composition is used as an insulating layer. The internal configuration of the tubular conductor may be slightly different from the internal configuration of FIG. 1, FIG. 2 and FIG.

Also, the jacket 6 usually uses high-density polyethylene,
The jacket 6 may not be used. As the high-pressure low-density polyethylene resin used in the present invention, low-temperature brittleness resistance, abrasion resistance, heat resistance, weather resistance, environmental stress crack resistance, bending resistance, etc. are required, so that the melt index is 0.1 to 2.0, Density 0.
It is desirable to use an 92-0.93 ethylene polymer.

The linear ethylene-α-olefin copolymer in the composition of the present invention is polymerized by a low pressure method using an organometallic catalyst, has a density of 0.91 to 0.93 g / ml, and the copolymer composition has at least 60% by weight of ethylene. % And up to 40% by weight of α-olefin, and may also contain a small amount of a third component. Generally, a copolymer having an α-olefin content of 5 to 15% by weight is commercially available. α-Olefin is preferably one having 3 to 8 carbon atoms, for example, propylene, butene-1, hexene-1, 4-methylpentene-
1 and the like.

As the organometallic catalyst, in addition to the Ziegler type, the Phillips type, and the like, a catalyst obtained by improving and modifying these is preferable.

The reaction conditions are 1/10 that of conventional high-pressure polyethylene production.
At a pressure of about 0, the temperature can be lowered by 150 ° C. or more, so it is called an energy saving process.

For the reaction, a gas phase method or a solution method is used, but in the present invention, it is preferable to use a gas phase method in which a powdery or granular copolymer can be used as it is in the modification.

The melt index (hereinafter referred to as MI) of the copolymer is desirably 0.5 to 50 as a value (g / 10 minutes) measured according to JIS K-6760.

When a compound having an M.I of 0.5 or less is used, the MI value of the obtained graft-modified product is significantly reduced, and the extrudability is extremely deteriorated.

On the other hand, when the MI is 50 or more, it is difficult to recognize the improvement of the synergistic effect of the adhesive force by mixing, which is a feature of the present invention.

As the ethylene-ethyl acrylate copolymer used in the present invention, those having an MI of 0.1 to 200 can be used, but it is preferable.
Those having a range of 0.5 to 30 are preferred. The content of ethyl acrylate in the copolymer is preferably 40% or less.

As the unsaturated carboxylic acid or its anhydride used in the present invention, acrylic acid, maleic acid, itaconic acid,
Examples thereof include fumaric acid, himic acid, citraconic acid, and acid anhydrides thereof, and it is particularly preferable to use acrylic acid or maleic anhydride.

When the amount of the unsaturated carboxylic acid or the acid anhydride to be added is less than 0.01 part by weight with respect to 100 parts by weight of the linear ethylene-α-olefin copolymer, the adhesive strength is low, and when it exceeds 30 parts by weight, the irritating odor is increased. Is strongly undesirable. Therefore 0.01 ~
Use 30 parts by weight.

In the present invention, benzoyl peroxide, di-t-butyl peroxide may be used as an organic peroxide used when adding an unsaturated carboxylic acid or an acid anhydride thereof to a linear ethylene-α-olefin copolymer. , Dicumyl peroxide, 2,5-dimethyl-2,5-di-t-butylperoxyhexane, 1,1-bis (t-butylperoxy) -3,5,5-trimethylcyclohexane and the like. . If the amount of the organic peroxide is more than 0.5 part by weight with respect to 100 parts by weight of the linear ethylene-α-olefin copolymer, a gel or a fish eye is undesirably generated in the resulting modified resin.

On the other hand, if the amount is less than 0.01 part by weight, the addition rate becomes insufficient and the adhesive strength becomes insufficient. Therefore, it is desirably in the range of 0.01 to 0.5 parts by weight.

As a method for producing the modified resin, various known modification methods can be applied.

For example, an unsaturated carboxylic acid or an acid anhydride thereof and an organic peroxide such as benzoyl peroxide, di-t-butyl peroxide, dicumyl peroxide are added to the above-mentioned linear ethylene-α-olefin copolymer. And mixed with a mixer such as a Hensiel mixer, a ribbon blender, a tumbler, and the like.
150-300 ° C. in a single or multi-screw extruder, preferably 180
Melt and knead at ~ 250 ° C. In the present invention, the mixing ratio of the high-pressure low-density copolyethylene resin of (a) and the modified polyolefin resin of (b) is determined in consideration of the electrical properties of the insulating layer and the adhesion and adhesion between the outer tubular conductor and the insulating layer. The amount of the unsaturated carboxylic acid or the anhydride thereof added to the resin composition
Must be in the range of 0.001 to 0.5% by weight, 0.001%
If the amount is less than 0.5% by weight, the adhesiveness / adhesion between the insulating layer and the outer tubular conductor becomes insufficient. If the amount is more than 0.5% by weight, the electrical properties of the insulating layer deteriorate, which is not desirable.

In the present invention, the formation of the insulating layer is carried out by extrusion-coating the resin composition used in the present invention on the outer tubular conductor and then cooling it.

[Action]

In the present invention, since the resin composition having excellent electrical properties and adhesiveness / adhesion is used, the outer tubular conductor and the insulating layer are firmly bonded.

〔Example〕

[Modified ethylene-α-olefin copolymer and ethylene-
Preparation of a mixture with an ethyl acrylate copolymer or a mixture of a modified ethylene-α-olefin copolymer and a modified ethylene-ethyl acrylate copolymer] Granular linear ethylene having a density of 0.934 g / ml at M.I5 -Α-olefin copolymer (GRSN-7149, manufactured by UCC) powdered maleic anhydride 0.5% and calcium carbonate were mixed with 2,5-dimethyl-2,5 (di-t-butylperoxy) hexane for 40%. %
The adsorbed organic peroxide-containing powder (0.08%) is mixed well with a Hensiel mixer, and the extruder to be supplied to the extruder has a screw diameter of 65 mm, L / D = 22, and a screw rotation speed of 30 rpm. The barrel temperature was set to 180 ° C. The graft polymerization reaction was performed during the heating and melting, and a modified maleic anhydride-grafted ethylene-α-olefin copolymer was obtained. This pellet and a pellet of an ethylene-ethyl acrylate copolymer (MI = 1.5 ethyl acrylate content = 15%, DPDJ-6182 manufactured by Nippon Unicar Co., Ltd.) were mixed at a predetermined ratio with a Hensiel mixer. The mixture was supplied to the above extruder to obtain a mixture of a modified ethylene-α-olefin copolymer and an ethylene-ethyl acrylate copolymer.

Further, the modified ethylene-α-olefin copolymer and the modified ethylene-α-olefin copolymer obtained by the same method as the above-mentioned method for producing the modified ethylene-α-olefin copolymer were mixed at a predetermined ratio with a Henschel mixer. Then, the mixture was supplied to an extruder and heated and kneaded to obtain a mixture of a modified ethylene-α-olefin copolymer and a modified ethylene-ethyl acrylate copolymer.

[Preparation of Resin Composition for Insulating Layer] 5 parts by weight of resin mixture prepared in Examples 1 to 6 and Comparative Examples 1 to 5 and a high-pressure low-density polyethylene resin having a density of 0.92 g / ml and MI = 0.12 g / 10 minutes 95 parts by weight were mixed by a Hensiel mixer, and then fed to an extruder to obtain granules with a pelletizer.

[Production and test results of optical fiber submarine cable] Example of an outer tubular conductor made of copper or aluminum with an outer diameter of 12.25 mm manufactured by arranging optical fiber units, inner tubular conductors, steel wires, etc. at predetermined positions. 5 to 11, Comparative Example 3
Extrusion temperature of 180 to 220
Under the condition of ° C., coating was performed to a thickness of 3.5 mm to form an insulating layer.

With respect to the test samples of these insulating layer coatings, the adhesive strength between the outer tubular conductor and the insulating layer, the durability of the adhesive strength in water, the low-temperature embrittlement of the insulating layer, the environmental stress cracking property, etc. were measured and are shown in Table 3.

 Each measuring method is as follows.

(1) Adhesion strength A 25 cm outer tubular conductor coated with an insulating layer was used as a sample, and the insulating layer was peeled off from both ends by 10 cm and 5 cm, respectively. It was measured.

(2) Durability of Bond Strength in Water After the test piece was immersed in water at 40 ° C. for 21 days, the bond strength between the insulating layer and the outer tubular conductor and the permeability of moisture to the interface between them were observed.

(3) Low-temperature embrittlement of insulating layer Measured by the method of ASTM D746.

 Shown at the temperature at which 50% destruction occurs.

(4) Environmental stress cracking property According to the method of ASTM D1693, the cracking rate of 10 test pieces was measured after 300 hours in a 100% solution of normal propanol at 50 ° C.

[Effect of the Invention] The optical fiber submarine cable of the present invention has an outer tubular conductor and an insulating layer that are firmly adhered to each other, are resistant to tension and bending force, are easily damaged or cut, and are damaged even if they are damaged or cut. Remains at that portion, and does not propagate along the interface between the outer tubular conductor of the cable and the insulating layer.

In the present invention, since the acid-modified ethylene-α-olefin copolymer and the ethylene-ethyl acrylate copolymer or the acid-modified product thereof are shared, better adhesiveness and flexibility than when each is used alone, , And the optical fiber submarine cable manufactured using the same shows excellent performance.

[Brief description of the drawings]

FIGS. 1, 2, and 3 are cross-sectional views showing examples of conventional typical optical fiber submarine cables. In the present invention, the insulating layer is replaced with a specific resin composition from conventional polyethylene. This is applicable to any of the optical fiber submarine cables shown in FIGS. 1, 2, and 3. DESCRIPTION OF SYMBOLS 1 ... Optical fiber unit 2 ... Inner tubular conductor 3 ... Steel wire 4 ... Outer tubular conductor 5 ... Insulating layer 6 ... Outer jacket

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Toru Kuwahara 1-16-10 Dogenzaka, Shibuya-ku, Tokyo Inside Japan Ocean Undersea Electric Cable Co., Ltd. (72) Inventor Satoshi Utsumi 8-1 Ukishima-cho, Kawasaki-ku, Kawasaki-shi Inside Nippon Unicar Co., Ltd. (72) Inventor Toshio Sakamoto 8-1, Ukishima-cho, Kawasaki-ku, Kawasaki City Inside Nippon Unicar Co., Ltd. (72) Kunio Kotani 8-1, Ukishima-cho, Kawasaki-ku, Kawasaki City Nippon Unicar Co., Ltd. In-house (56) References JP-A-61-53611 (JP, A)

Claims (1)

(57) [Claims] 1. An optical fiber submarine cable comprising an optical fiber unit, an inner tubular conductor, a steel wire, an outer tubular conductor, an insulating layer and a jacket, wherein the insulating layer comprises: (a) a high-pressure low-density polyethylene resin; b) A modified ethylene-α-olefin copolymer obtained by grafting an unsaturated carboxylic acid or an anhydride thereof to a linear ethylene-α-olefin copolymer produced by a gas phase / low pressure method having a density of 0.91 or more. 80 to 40% by weight of a polymer and 20 to 60% by weight of an ethylene-ethyl acrylate copolymer or a copolymer obtained by grafting a part of the above unsaturated carboxylic acid or an acid anhydride to the copolymer. A resin composition comprising a modified ethylene copolymer mixture consisting of a high-pressure low-density polyethylene resin (a) and a modified ethylene copolymer mixture (b), Characterized in that the addition amount of the carboxylic acid or the acid anhydride thereof is in the range of 0.001 to 0.5% by weight based on the resin composition. .