JPS58190842A - Production of optical fiber core - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a tight structured optical fiber core having a secondary coating layer having a low coefficient of linear expansion and a high modulus of elasticity.

For the purpose of forming a highly reliable optical fiber transmission line, conventionally, optical fibers (hereinafter abbreviated as fibers) have been coated by the following two methods.

One type is a three-layer fiber core, in which the fiber is first coated with a modified silicone resin, then a buffer layer is formed with a silicone resin, and then a second layer is coated with a nylon resin. Produced by applying a subsequent coating layer. In other words, it is a fiber core wire with a tight structure.

The other type is a loose tube type fiber core, in which 1 μ of fiber coated with a primary coating or a primary coating and a buffer layer is loosely placed inside a protective plastic tube made of a material such as nylon resin or polypyrene resin. It is made by holding it in. Usually, there is an air space between the inner wall of the plastic tube and the fiber wire, but there are cases where the space is filled with Sitoeri or silicone oil, which is liquid at room temperature.

The elastic modulus of the secondary coating layer of the fiber core produced by the above two methods is several GPa, and the coefficient of linear expansion is on the order of 10-1°C-1, which is higher than the elastic modulus of the fiber itself, which is about 700 Pa, lIi! Expansion rate 10-”C””1”1 order! ...and has a much lower modulus of elasticity and a higher coefficient of linear expansion. For this reason, strength reinforcement using a tension member or the like is essential, and furthermore, an increase in transmission loss at low temperatures due to temperature shrinkage of the secondary coating layer cannot be avoided. In order to solve these problems, the plastic tube (hereinafter referred to as "tube"), which is to be the secondary coating layer, is dielectrically stretched and heated without using external heating. A method of manufacturing a fiber core wire with a linear expansion coefficient has been proposed. In this method, the fiber wire is passed through a tube with an inner diameter larger than the outer diameter of 1, while the tube is stretched, and the molecular chains are oriented in the stretching direction to achieve a high elastic modulus and a low wire. Increase the expansion rate. Therefore, the tube running speed and the fiber wire running speed 1-.degree. in the tube drawing process are different. Further, as the tube is stretched, the inner diameter of the tube decreases, and the clearance with the fiber wire becomes smaller. As the clearance decreases, the frictional force due to contact between the inner wall of the tube and the surface of the fiber strand increases, and the fiber running speed decreases.
(3) Unable to maintain constant control.

Therefore, in order to obtain a tightly structured fiber core with a high modulus of elasticity and a low coefficient of linear expansion using the above method, variations in the outer diameter of the fiber wire and the inner diameter of the tube must be kept extremely small.
Accurate control of the fiber manufacturing process and the tube extrusion process was essential.

In order to solve these problems associated with the production of tight-structured fiber cores using the dielectric heating drawing method, the present invention has been developed by filling the inside of the tube with uncured and liquid thermosetting resin or thermoplastic resin. After forming the secondary coating layer by drawing, the filling liquid is cured or solidified to form the primary coating layer, and the purpose is to provide a tight-structured fiber core with high strength and excellent transmission loss. There is a particular thing.

FIG. 1 is a schematic explanatory diagram of a vertical tight-structured fiber core manufacturing apparatus using a dielectric heating drawing method according to the present invention, and numeral 1 indicates a feeding dryer for a fiber strand.

2 is a fiber wire, 8 is a die for extruding the tube, and 4 is an uncured/liquid thermosetting or molten fiber. (4) A liquid sending pump that sends out a thermoplastic resin in a molten state - 5 is a liquid sending tube, 6 is a tube containing a fiber wire and a thermosetting or thermoplastic resin inside, 7 is a tube cooling tank, 8 is a tube feeder, 9 is a dielectric heating furnace, 10 is a tube take-up machine, 11 is a tube annealing furnace, 12 is a tube take-up machine, and 18 is a winding drum.

A constant back tension is applied to the unwinding drum 1, so that the fiber 2 is unwound under constant tension. The extrusion die 8 continuously extrudes a tube having a certain shape. The liquid feed pump 4 sends out a fixed amount of uncured, liquid thermosetting or molten thermoplastic resin. The liquid feeding tube 5 feeds an uncured liquid thermosetting resin or a molten thermoplastic resin to the extrusion die 3 . The temperature of the cooling tank 7 is controlled at Ilθ°C to 80°C, and the tube 6 extruded from the extrusion die 8 is completely solidified. The feeding machine 8 determines the speed at which the tube is extruded from the extrusion die 8 and the speed at which the tubes are fed to the dielectric heating device 9 by holding down the tube 6 with two belts rotating at a constant speed. The dielectric heating device @9 selectively heats the amorphous portion of the tube by dielectric heating combined with heating of the outer portion, and at the same time maintains the ambient temperature at which the tube 6 can be easily stretched. Collection machine 1
0 determines the tube take-up speed after stretching and the tube delivery speed to the annealing furnace 11 by holding down the tube 6 with two belts rotating at a constant speed.The annealing furnace 11 is a heating furnace with a constant temperature. This method eliminates tube shrinkage after stretching, and at the same time raises the temperature of the uncured thermosetting material to speed up curing. 1. The pulling machine 12 holds down the tube 6 with two belts rotating at a constant speed, thereby determining the tension applied to the tube 6 during annealing and at the same time determining the final manufacturing speed of the fiber core wire. do.

The winding drum 18 winds up the fiber core. FIG. 2 is a schematic diagram of the extrusion die 8, in which 14 is a tube in a molten state, and 16 is an uncured, liquid thermosetting resin or a thermoplastic resin in a molten state. The thermoset or thermoplastic resin 15 fed into the extrusion die 8 by the liquid delivery tube 6 flows down through the extrusion die 8 and accumulates inside the tube 6 at the exit 1 from the extrusion die lip. The height of the liquid level of thermosetting or thermoplastic resin 5 can be arbitrarily determined by controlling the amount of liquid fed.

In order to operate this, the speeds of the feeder 8, take-off machine 10.1 and take-off machine 12 are made approximately equal, and the external heating of the dielectric heating device 9 is raised to a predetermined temperature.

Thereafter, the tube 6 is extruded from the extrusion die 8, manually taken out, passed through each device in sequence, and then taken out by the take-up machine 1.
Supply up to 2. After that, the dielectric heating output of the dielectric heating device 9 is gradually increased, and at the same time, the
Gradually increase the take-up speed to -F to reach the target output and stretching ratio. Next, the fiber 2 is paid out from the feeding drum 1, passed through the tube 6, and supplied to the take-off machine 12.

At this time, a constant back tension of -1° is applied to the twin bar 2 by the feeding drum 1. Thereafter, the liquid feed pump 4 sends uncured, liquid thermosetting or molten thermoplastic resin to the extrusion die 8 through the tube 5 .
, 1° (7
) As shown in FIG. 2, the extruded thermosetting or thermoplastic resin is applied to the fiber at the entrance of the extrusion die 8, is fed together with the fiber, and temporarily accumulates after exiting the die lip. Thereafter, while filling the gap between the fiber 2 and the inner wall of the tube 6, the thermosetting or thermoplastic resin 15 is consumed little by little, so an amount to compensate for the consumption is constantly sent out from the liquid pump. , the height of the liquid level is kept constant.

By the above operating method, a fiber core filled with an uncured or semi-cured thermosetting resin or a thermoplastic resin in a molten state is obtained at the drawing machine 12 stage. Thereafter, as the thermosetting resin or thermoplastic resin hardens, a tight structured fiber core is formed.

The plastic tube material in the present invention can be any thermoplastic resin. Specific material names include polyolefins such as polyethylene and polypropylene, polyethers such as polyoxymethylene, polyamides such as nylon, etc. ) Polyesters such as polyethylene terephthalate, 1-polyacrylonitrile, polyvinyl alcohol, polyvinylidene fluoride, etc. can be mentioned.

In the present invention, the thermosetting resin is about 200% when uncured.
Any material having a viscosity of 0 Cps or less can be used, and the material is not particularly limited. Specific material names include silicone resin, epoxy resin, etc. In addition, as a thermoplastic resin, 2000
Any material having a viscosity of cps or less can be used, and there are no particular restrictions on the material, but examples include low molecular weight polymers and polymers that exhibit a low viscosity liquid crystal state in the molten state. . An example using the apparatus shown in FIG. 1 will be described below.

Actual Example 1 The outer diameter of the fiber wire used, including the modified silicene layer, was 0.2 mmφ. A back tension of 800 g was applied to the fiber. As a material for the tube, polyoxymethylene (density 1.41p can8, melting point 165°C,
Number average molecular weight 80,000, -... Weight average molecular weight 1
60,000) was used. The bolyoxymethylene (
Hereinafter abbreviated as POM), 20? Using a lLmφ extruder, the screw rotation speed is 8 orpm, and the cross is made into a rad die (die temperature 165℃, die lip outer diameter a, om@φ, inner diameter L
5imφ), take-up speed Pa (tube feeding speed) 1
．． Extrusion molding was performed at 14 Vmin to produce an unstretched POM tube with an outer diameter of 5.1 mmφ, an inner diameter g, and 2 mmφ. This was heated using a dielectric heating device (oscillation frequency 2.45 GHz, heating cylindrical waveguide 8crn1 inner diameter 95.6 mmφ, maximum output 1.s KW), and by external heating, the temperature at the inlet of the dielectric heating device was 40°C, and the temperature at the outlet was 40°C. Stretching was carried out at a temperature of 140° C. and a take-up speed of 23 J Vmin. The temperature of the annealing furnace was 170°C, and the take-up speed after annealing was 28.
It was set to 51m1n. The final stretching ratio in this case is 19
．． It was 7 times more. 15 A silicone resin having a viscosity of 8 Is Ocps at 26° C. was used as the thermosetting resin. The outer diameter of the obtained stretched POM tube was 1.1 mmφ,
The inner diameter is 0.5 m'mφ, and the coefficient of linear expansion is I
The tensile modulus was 25 GPa. In other words, it was possible to obtain a tight-structured fiber core with a low coefficient of linear expansion and a high modulus of elasticity of 70.

Example 2 The outer diameter of the fiber used, including the buffer layer, was 0.
It was 445 mmφ. Other materials, equipment, etc. used were the same as in Example 1. The properties of the tight structured fiber core obtained were almost the same as in Example 1.

Example 8 The outer diameter of the fiber wire used was 0.445 mmφ, including the buffer layer. The thermosetting resin consists of a main resin (viscosity 700 to 1100 cps at 25°C) and a curing agent (viscosity 90 to 1.80 cps at 25°C).
An epoxy resin containing l=1 was used. The other materials, devices, etc. used were the same as in Example 1, and were 11 in total. In this case, the modified silicone resin layer - shi, the silicone dark fat layer -
A tight structured fiber core wire having a 4N structure consisting of an epoxy resin layer and a POM secondary coating layer could be obtained.

As explained above, the present invention provides plastic parts 2. .

After the fiber is heated dielectrically using external heating and stretched to a high degree of orientation, the thermosetting or thermoplastic resin filled between the fiber strand and the inner wall of the tube is cured or solidified, resulting in high elasticity. This method has the advantage that a tightly structured fiber core wire having a low linear expansion coefficient and a low coefficient of linear expansion can be easily produced.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of a fiber core manufacturing apparatus for carrying out the present invention, and FIG. 2 is a schematic diagram of an extrusion die. 1°゛・Fiber feeding drum, 2...Fiber, 8・
...Tube extrusion die, 4...Liquid pump, 5...
Liquid feeding tube, 6...tube, 7...cooling tank,
8... Tube feeding machine, 9... Dielectric heating device, 10
...Tube pulling machine, 11...Annealing furnace, 12.
...Tube take-up machine, 18... Core wire winding drum, 1° 14... Tube in molten state, 15... Uncured/liquid thermosetting resin or thermoplastic resin in molten state.

Claims (1)

[Claims] L A plastic tube made continuously by extrusion molding of thermoplastic resin is filled with uncured, liquid thermosetting or molten low viscosity thermoplastic resin, and a certain back tension is applied. While passing the optical fiber wire through the plastic tube, the Plato-Stek tube is continuously stretched by dielectric heating combined with external heating, and in the next step, the plastic tube is held under constant tension. 1. A method for producing a cored optical fiber, the method comprising: annealing the cored optical fiber at