JPH0547803B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] This invention relates to a water-stop tape for optical fiber cables. [Prior Art] Generally, in optical fiber cables, most cable failures are due to water intrusion into the cable, resulting in adverse phenomena such as deterioration of optical fiber strength and deterioration of transmission characteristics due to freezing. For this reason,
BACKGROUND OF THE INVENTION Moisture-proofing materials are housed within optical fiber cables to provide water-blocking properties. Conventionally, as such moisture-proof materials, jewelry materials such as polybutene and petrolactam-based materials have been used. However, this type of jewelry material is sticky and has poor wiping properties, as it cannot be wiped off without using an organic solvent. This causes deterioration of workability when connecting optical fiber cables, etc. [Problems to be Solved by the Invention] In order to solve these problems, attempts have been made to use a water-absorbing and swelling tape in place of the jewelry material described above. For example, a water-absorbing swelling tape has been considered in which a water-absorbing layer made of pulp fibers containing water-absorbing polymer powder of a polymer electrolyte such as a crosslinked polyacrylate is formed on the front and back surfaces of a plastic film or the like. This water-absorbing and swelling tape does not have the stickiness and poor wiping properties of the jewelery materials, so it has excellent properties such as connection workability. However, the water-absorbing polymer made of the polymer electrolyte has different water-absorbing performance depending on the water quality, so optical fiber cables using it have a major drawback in that they cannot be installed on the coast or the seabed. In other words, polymer electrolytes such as the above-mentioned polyacrylates exhibit about 30 times the water absorption performance for fresh water, but they do not absorb ionized water such as seawater (Na ⁺ , Cl ^- ,
For water containing ions such as K ⁺ , it exhibits only about 5 times the water absorption performance. Therefore, if an optical fiber cable using this cable is installed in a place where seawater or the like may enter, a sufficient water-stopping effect cannot be obtained even if seawater enters the cable. On the other hand, it is also possible to use polyethylene oxide, which has a high water-absorbing ability, as a water-absorbing polymer powder, but although polyethylene oxide itself has a high water-absorbing ability, it melts due to changes in environmental temperature, adheres to the optical fiber, and absorbs light. By suppressing or stopping the movement of the fiber due to bending or thermal expansion, it is expected that the optical fiber will be distorted and its transmission loss will increase. This invention was made in view of the above circumstances, and does not impose restrictions on the installation location of optical fiber cables, and does not cause an increase in transmission loss after installation of the optical fiber cables.
Moreover, it is an object of the present invention to provide a water-stop tape for optical fiber cables that does not impair workability such as connection work. [Means for Solving the Problems] In order to achieve the above object, the water stop tape for optical fiber cables of the present invention is a water stop tape for optical fiber cables in which a water absorption and swelling layer is formed on at least one surface of a film-like base material. In the water-stop tape, the water-absorbing and swelling layer contains component (B) in a ratio of 0.4 to 0.4% to component (A) below.
It is composed of crosslinked polyethylene oxide which is mixed at a ratio of 2.5% by weight and subjected to a crosslinking reaction. (A) Polyethylene oxide with an average molecular weight of 20,000 or more. (B) Difunctional or trifunctional crosslinking agent. It is generally known that polyethylene oxide-based water absorbing polymers exhibit approximately the same water absorption capacity for fresh water and ionic water. Therefore, the present inventors
After focusing on ethylene oxide-based water-absorbing polymers and conducting repeated research on how to apply them to water-stopping tapes, we discovered that polyethylene oxide-based water-absorbing polymers can become solvent-soluble by appropriately adjusting their molecular weight and crosslink density. As a result of further detailed research into this molecular weight and crosslinking density, the present inventors found that when a specific amount of a specific crosslinking agent is added to polyethylene oxide with an average molecular weight of 20,000 or more and a crosslinking reaction is carried out, the resulting crosslinked polyethylene oxide Since it is soluble in various solvents, the present inventors have discovered that a water-stopping tape for optical fiber cables with excellent performance can be obtained by simply coating it directly on a film-like base material, etc., and have thus arrived at this invention. The water stop tape for optical fiber cables of the present invention is obtained using a film-like base material, polyethylene oxide having an average molecular weight of 20,000 or more, and a bifunctional or trifunctional crosslinking agent. Examples of the film-like flexible base material include plastic films such as polyethylene terephthalate film, polyethylene film, and vinyl chloride resin film. However, there is no problem in using metal foil such as aluminum foil as long as it has flexibility. The polyethylene oxide having an average molecular weight of 20,000 or more, which is the component (A) forming the water-absorbing swelling layer, is not particularly limited. Component (B), which serves as a crosslinking agent for component (A), includes isocyanate crosslinking agents such as aliphatic isocyanates and aromatic isocyanates, dicarboxylic acid crosslinking agents such as phthalic acid and succinic acid, and furthermore 1,4- Examples include diol crosslinking agents such as butanediol and polyoxypropylene glycol, and diamine crosslinking agents such as hydroxypropylethylenediamine. However, preferred are isocyanate crosslinkers. This (B) component crosslinking agent is added in an amount of 0.4 to 2.5% by weight (hereinafter referred to as "%") based on the (A) component polyethylene oxide.
It is soluble in various solvents by blending at a ratio of It is possible to obtain crosslinked polyethylene oxide with an appropriate melting point, which is not affected by the bending of optical fibers (which suppress or stop the movement of optical fibers due to bending and thermal expansion, resulting in an increase in transmission loss). If the usage rate of the above-mentioned crosslinking agent is less than 0.4%, the crosslinking density will be too small, the melting point will be low, the melt viscosity will be low, and there will be a problem that it will melt due to environmental temperature changes and adhere tightly to the optical fiber core etc. become. On the other hand, if it exceeds 2.5%, the solubility in solvents becomes poor and coating becomes impossible. Therefore, it is necessary to set the amount of the crosslinking agent used in the range of 0.4 to 2.5% based on component (A). The water stop tape for optical fiber cables of the present invention can be manufactured using the above-mentioned raw materials, for example, in the following manner. i.e. width 1.4-2.0
An organic solvent solution of the above-mentioned crosslinked polyethylene oxide is coated on one or both of the front and back surfaces of a continuous strip-shaped film substrate (hereinafter referred to as "tape body") with a thickness of 15 to 100 μm, preferably 25 μm. It can be manufactured by impregnation, etc.) and drying. The organic solvent for dissolving the crosslinked polyethylene oxide is not particularly limited, and examples thereof include chlorine-containing solvents such as dichloroethane and trichloroethane, hydrocarbons such as n-pentane, n-octane, benzene, toluene, and xylene, Examples include alcohols such as methyl alcohol and ethyl alcohol, ketones such as acetone and methyl ethyl ketone, and esters such as methyl acetate and ethyl acetate. The thus obtained water-stop tape for optical fiber cables is easy to manufacture because a water-absorbing swelling layer made of cross-linked polyethylene oxide is directly formed on one or both of the front and back surfaces of the film-like base material. . Moreover, since the water-absorbing swelling layer is made of cross-linked polyethylene oxide, it exhibits excellent water-absorbing performance for both fresh water and ionic water. Therefore, an optical fiber cable using this can also be used as a coastline cable, etc., and is not subject to restrictions on installation location. Moreover, since the cross-linked polyethylene oxide mentioned above has a specific molecular weight and is cross-linked to a predetermined degree of cross-linking using a specific cross-linking agent, it melts due to changes in the environmental temperature after the optical fiber cable is laid, and becomes an optical fiber core wire, etc. Problems such as welding and increase in transmission loss of the optical fiber do not occur. Next, examples will be described together with comparative examples. [Examples 1 to 3, Comparative Examples] First, polyethylene oxide with an average molecular weight of 20,000 or more was prepared, and a crosslinking agent shown in Table 1 below was reacted with it at the ratio shown in the same table to form a crosslinked polyethylene oxide. Manufactured. The melting point, solubility in solvents, and water absorption capacity of the obtained crosslinked polyethylene oxide are shown in the same table. The resulting crosslinked polyethylene oxide was then dissolved in an organic solvent and applied to both sides of a 25 μm thick polyethylene terephthalate film and dried to form a 50 μm thick water-absorbing swelling layer to produce the desired water stop tape. This water stop tape is shown in FIG. In the figure, 1 is a polyethylene terephthalate film, and 2 is a water-absorbing swelling layer. The adhesion of the thus obtained water stop tape to the optical fiber core wire was investigated and is shown in Table 1 below.

【table】

[Table] Note that when directly coating a polyethylene terephthalate base material with the above-mentioned organic solvent solution of crosslinked polyethylene oxide, the adhesion between the two may be poor in some cases. In such a case, as shown in FIG. 3, if an undercoat layer 2a is provided on the film-like base material 1 in advance, the adhesion between the base material 1 and the water-absorbing swelling layer made of cross-linked polyethylene oxide can be improved. I can do it. In this case, measure the contact angle between the cross-linked polyethylene oxide and the undercoat coating agent, select an undercoating agent that makes the contact angle between the polyethylene oxide and the surface of the base material 1 after undercoating within 30°, and then apply the undercoat. It is preferable to do so from the viewpoint of adhesion. Examples of the undercoating agent include polyester resins, phenolic resins, coupling agents, etc. When these are used, the contact angle becomes within 30°. Next, FIG. 4 shows a cross section of a water-absorbing waterproof cable in which the water-stop tape for optical fiber cable obtained in the above example is assembled. That is,
This optical fiber cable 5 has a tension member 6 at the center, and spacers 7 with an outer diameter of 7 mm are provided to surround this, and a width of
Four grooves 8 of 1.6 mm x 1.5 mm depth are formed.
In one of the grooves, two optical fiber core wires 10 having a structure of accommodating four optical fibers are housed one above the other, and the water stop tape 3 for optical fiber cable of the present invention is positioned and arranged between them. It is set up. Each of the other three grooves accommodates one water-absorbing string (6000 denier) 11 made of fibers of acrylic acid-acrylate-acrylonitrile copolymer. The first volume is a water-absorbing tape (0.25 m thick, 25 m wide) made of the same material as the water-absorbing string above.
mm, area weight: 101 g/m ² ) 12 was wound in a 1/4 overlapping manner. Note that 13 is an aluminum tape with a thickness of 0.2 mm, and 14 is a polyethylene sheath with a thickness of 1.2 mm. Next, FIG. 5 shows an explanatory diagram of the waterproof test of the above cable. That is, a vinyl pipe 15 is attached vertically to a 1 m long Cagle sample 5, and a water 16
was inserted to a height of 1.2 m, and after 24 hours, water seepage at the end of the cable 5' was observed. The water-absorbing tape used for this cable 5' has the ability to absorb water even in seawater.
25 each for artificial seawater and pure water with NaCl added
A cable sample test was conducted. the result,
No water seepage was observed in each of the 25 cable samples. Next, the sample was disassembled and the length of the part where water permeated was measured. The results are shown in Table 2 below.

〔Effect of the invention〕

The water-stop tape for optical fiber cables of the present invention has a water-absorbing and swelling layer made of cross-linked polyethylene oxide obtained by subjecting component (A) to a specific amount of cross-linking of component (B), so it is resistant to fresh water. It also exhibits effective water absorption performance against ionized water such as seawater. Therefore, an optical fiber cable using this can be installed not only in fresh water but also in places where it comes into contact with seawater, etc., and has a wide range of use without being restricted by the installation location. Moreover, the water-stop tape for optical fiber cables of this invention melts due to changes in environmental temperature and adheres closely to the optical fiber, suppressing movement caused by bending and thermal expansion of the optical fiber, and causing distortion to the optical fiber. This prevents a situation in which transmission losses increase due to the occurrence of problems. Moreover, it does not have poor wiping properties like traditional jewelry materials.
It becomes possible to easily connect optical fiber cables, etc.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of one embodiment of this invention, Fig. 2 is an explanatory diagram of adhesion test of water stop tape, Fig. 3 is a block diagram of another embodiment, and Fig. 4 shows the light of Fig. 1. FIG. 5 is a cross-sectional view of a fiber cable water-stop tape assembled into an optical fiber cable, FIG. 5 is an explanatory diagram of a waterproof test of the water-stop tape, and FIG. 6 is a configuration diagram of another embodiment. 1...Tape body, 2...Water absorption swelling layer, 3...
Water stop tape.

Claims (1)

[Scope of Claims] 1. A water-stopping tape for optical fiber cables in which a water-absorbing swelling layer is formed on at least one surface of a film-like base material, wherein the water-absorbing swelling layer has the following components (A) and (B). A water-stop tape for optical fibers made of crosslinked polyethylene oxide, which is made by blending components at a ratio of 0.4 to 2.5% by weight and subjecting them to crosslinking reaction. (A) Polyethylene oxide with an average molecular weight of 20,000 or more. (B) Difunctional or trifunctional crosslinking agent.