JPS60179219A - Extrusion molding method of external coating to optical fiber made of plastics - Google Patents

Abstract

PURPOSE:To prevent softening of a fiber due to heat at the time of extrusion molding, by making a heat insulating and heat resisting material interpose between the fiber passing through a nipple and the inside of the nipple. CONSTITUTION:A heat insulating and heat resisting tube 8 to be obtained by making a plaited tube made of a crosslinking fiber made of phenol formaldehyde impregnated with heat resisting paints, for example, silicon series heat resisting paints is fitted in the inside of a nipple 6 and a nipple holder. The size of the heat insulating and heat resisting tube 8 to be used hereupon is selected appropriately according to thickness of the fiber 5. After the heat insulating and heat resisting tube 8 has been fitted in the nipple 6 and adjustment of non-uniform thickness has been performed by inserting the fiber 5 through the nipple 6 and a die 4, high concentration polyethylene external coating 10 is molded through extrusion. As softening of the fiber at the time of piercing of the fiber through the nipple is prevented by insulating the inside of the nipple thermally, outlet work of the extrusion molding becomes easy and generation of extension and a flaw on the fiber at the time of the extrusion molding does not occur.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a method for extruding a jacket onto a plastic optical fiber (hereinafter simply referred to as fiber).

(b) Prior art and its problems Conventionally, as a method for coating the outer surface of fibers with synthetic resin, extrusion molding method has been commonly used.
To explain with reference to the figure, the extruder 1 melts the resin 2.
It passes around the nipple 3 and extrudes into the die 4, and at the same time, it passes through the nipple 3, passes through the fiber 5 and extrudes it into the die 4.
The outer surface of the fiber 5 is coated with the synthetic resin 2 using a die 4.

By the way, the softening temperature of the optical fiber 5 is approximately 1
20° C., whereas the extrusion temperature of the synthetic resin 2, for example polyethylene, used for the jacket is the same or higher. For this reason, during the cutting process, the fiber 5 becomes soft and weak and bends, causing the die 4,
There is a problem in that a lead wire must be used to pass through the nipple 3.

In addition, in extrusion molding, the extrusion temperature of the jacket is higher than the softening temperature of the fiber 5, so the fiber 5 softens and is stretched by the pull-up tension, causing scratches on the surface and the outer diameter in the length direction. Variations may occur.

Furthermore, even if we tried to keep the extrusion temperature as low as possible to prevent the fibers 5 from softening, we could not lower the extrusion temperature to below the welding temperature of the outer sheath, or below 120°C, and the extrusion pressure would increase, resulting in severe elongation of the fibers 5. In some cases, this may lead to wire breakage.

For this reason, various studies have been made to extrude an outer covering onto the fiber 5, but no effective technique has been introduced so far.

In addition, the outer diameter variation σ of the actually produced products is 0.
．． It is about 01.

(c) Object of the present invention and means for solving the above-mentioned problems The present invention was developed in view of the situation in the north, and the present invention was developed in view of the situation in the north, where fibers are softened by the heat during extrusion molding when the outer jacket is extruded into fibers. It is an object of the present invention to provide a method for forming a jacket on a fiber without causing any damage, and which does not cause spreading or scratches during extrusion molding.

In order to achieve this objective, in the present invention, in the extrusion molding of the jacket onto the fiber, a heat insulating and heat resistant material is interposed between the fiber passing through the nipple and the inner surface of the nipple. .

Embodiments of the present invention will be described below with reference to the drawings.

(Gradient Example 1 In FIG. 2, as mentioned above, 4 is the die holder 9.
6 is a nipple attached to a nipple holder 7, and inside the nipple 6 and the nipple holder there is a heat insulating material made of a braided tube of cross-linked fibers of phenol formaldehyde impregnated with a heat-resistant paint, such as a silicone-based heat-resistant paint. A heat-resistant tube 8 is inserted.

The size of the heat-insulating heat-resistant tube 8 used here is appropriately selected depending on the thickness of the fiber 5, but in this example, the outer diameter is 4.1 wnφ, the outer diameter is 2.7 rranφ, and the thickness is 0.
．． Two pieces from Sankaku are used.

Although a braided tube made of organic fibers was used in this embodiment, a braided tube made of inorganic fibers may also be used, or these may be used in combination.

After inserting the heat-insulating heat-resistant tube 8 into the nipple 6 in this way, the fiber 5 is inserted into the nipple 6 and the die 4 to adjust the uneven thickness, and then a high-density polyethylene jacket 10 is extruded in the usual manner. .

(e) Example 2 In this example, the nipple 6 and the nipple holder -
A fluororesin tube 8 of the same size as in Example 1 was inserted into the inside of Example 7, and the method of molding the outer cover was the same as in Example 1.

(f) Example 3 In this example, a ceramic tube 8 having pores was molded and this was inserted into the inside of the nipple 6, and the method of molding the outer cover was the same as in Example 1. Next, in order to confirm the effects of the invention, fibers 5 having a diameter of 1.0 mm were subjected to jacket extrusion molding using the methods of Examples 1 to 3, and the results are shown in Table 1.

From this result, compared to the conventional method where the variation σ in the outer diameter was about 0.01, according to the method of the present invention, the variation σ was about 0.003, and the elongation was also small. Moreover, there were no scratches, indicating that the present invention is superior.

In each of the above embodiments, the tube 8 is inserted over the entire length of the nipple 6 and holder 7, but the tube 8 may be inserted only into the tip portion of the nipple 6 and holder 7, around which the molten resin 2 moves. good.

(G) Effects As explained above, according to the present invention, the inside of the nipple is insulated to prevent the fiber from softening when it passes through the nipple, making the extrusion molding work easier, and the fibers are not softened during extrusion molding. There is no elongation or damage, and there is very little variation in the outer diameter in the length direction, so good products can always be obtained.

[Brief explanation of drawings]

Figure 1 is a schematic diagram of the machine for extruding the jacket into fibers, Figure 2
The figure is a longitudinal cross-sectional view of a main part of an embodiment during extrusion molding according to the present method. 2...Synthetic resin, 3,6...Nipple, 4...Dice, 5...Fiber, 7...Holder, 8...
・Insulating heat-resistant tube, 10...outer cover. Patent Applicant: Tac Electric Cable Co., Ltd. Agent: Kama 1) Statement: Two Procedural Amendments (Mr. Kazuo Wakasugi, Commissioner of the Self-Responsive Patent Office, 1, Indication of the Case, Patent Application No. 38178, filed in 1982, 2, Name of Invention: Plastic Optical Fibers) Outer sheath extrusion molding method 3, relationship with the amended case Patent applicant address 2-3-1 Iwata-cho, Higashiosaka-shi, Osaka Name (1)
Tac Electric Cable Co., Ltd. 5゜Showa year, month, day, shipping date) 6. Amendment '° Increased power 6 inventions 0 ・As shown in the appendix Contents of amendment to method 6 1, [ on page 3, line 1 of the specification] Correct "Polyethylene Synthetic Resin 2" to "Polyethylene Composition 2". 2. Table 1 on page 6 of the same book will be amended as follows (this correction will be made by adding "30
). Table 1

Claims (4)

[Claims] (1) A plastic characterized by interposing a heat-insulating and heat-resistant material between the plastic optical fiber passing through a nipple and the nipple and nipple holder, or the inner surface of the nipple, in the case of extrusion molding the outer jacket of a plastic optical fiber. Extrusion molding method for outer coating on manufactured optical fiber. (2) A method for extruding an outer covering onto a plastic optical fiber according to claim (1), characterized in that a fiber braided tube coated with a heat-resistant paint is used as the heat-insulating and heat-resistant material. (3) A method for extruding a jacket onto a plastic optical fiber according to claim (1), characterized in that a heat-resistant plastic tube is used as the heat-insulating and heat-resistant material. (4) A method for extruding a jacket onto a plastic optical fiber according to claim (1), characterized in that a ceramic tube having pores is used as the heat-insulating and heat-resistant material.