JP3967678B2 - Manufacturing method of spacer for optical cable - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for manufacturing a spacer for an optical cable, and more particularly to a technique for improving the surface smoothness in the optical fiber housing groove and the moldability of the groove shape in a thin spacer having a diameter of 5 mm or less.
[0002]
[Prior art]
As this type of optical cable spacer, a spacer body is formed by coating the outer periphery of a tensile body with a thermoplastic resin, and a plurality of spiral grooves continuous in the longitudinal direction are provided on the outer periphery of the spacer body. .
[0003]
In such a conventional optical cable spacer, a single steel wire or a steel stranded wire is generally used as the tensile body, and polyethylene is generally used as the coating resin for forming the spacer body.
[0004]
However, when polyethylene is used as the main body resin, when manufacturing very thin spacers with an outer diameter of 5 mm or less, when the number of optical fiber storage grooves is relatively large, such as 3 or 4 grooves, In this case, the base thickness of the ribs separating the spiral grooves becomes very thin, the compression resistance is lowered, and it becomes unusable.
[0005]
On the other hand, in the optical cable spacer disclosed in Patent Document 1, it is proposed to use polybutylene terephthalate (PBT) / polycarbonate (PC) as a resin material for forming the spacer body in order to improve compression resistance. Has been.
[0006]
However, this patent document 1 discloses that the outer diameter exceeds 10 mm. When considering downsizing as it is and applying it to a thin spacer having an outer diameter of 5 mm or less, three grooves or four When designing a relatively multi-groove such as a groove, the rib base thickness is very thin, and therefore rib collapse is very likely to occur during manufacturing, and it is difficult to secure the groove shape.
[0007]
On the other hand, as a cooling method of such a profile extrusion molding, for example, as disclosed in Patent Document 2, for example, when the thermoplastic resin molding melt-extruded in the vertical direction is cooled, the thermoplastic resin There is known a method in which a resin aqueous solution is guided to a cooling cylinder in which a cooling aqueous solution to which a surfactant is added is opposed to the traveling of the thermoplastic resin molded product and presents an upward flow from the lower side to the upper side.
[0008]
However, with the method disclosed in Patent Document 2, when the actual production speed is a low speed of about 3.5 m / min, a product having a desired performance can be obtained. However, these conventional techniques have the following technical problems especially when manufacturing an optical cable spacer having an outer diameter of 5 mm or less.
[0009]
[Patent Document 1]
JP-A-6-258558 [0010]
[Patent Document 2]
JP 61-199921 A
[Problems to be solved by the invention]
That is, in a small optical cable spacer such that the outer diameter of the spacer main body coating layer is 5 mm or less, the outer diameter of the preliminary coating layer and the groove It was necessary to make the groove bottom thickness of the spacer body coating layer as thin as possible by making the outer diameter of the groove bottom determined by the inscribed circle of the bottom as close as possible.
[0012]
However, when the optical cable spacer having such a shape is manufactured, in the coating with the rotary die, the gap between the crest of the rotary die hole and the outer periphery of the preliminary coating layer supplied while being held by the nipple is narrowed. Further, surface roughness or the like may occur at the bottom of the groove of the main body coating layer formed thereon so that surface smoothness may be hindered.
[0013]
In addition, the tensile body used for the optical cable spacer of such dimensions is often the same size as the groove shape formed in the main body coating layer, so that the tensile body is close to the groove bottom of the spacer body. Thus, there is a risk that the transmission performance of the optical fiber to be accommodated may be deteriorated by affecting the groove shape, such as pushing up the groove bottom and raising the groove bottom.
[0014]
Further, as a cooling means in the manufacture of such an optical cable spacer, when the body coating resin melt-extruded in the vertical direction is cooled by a cooling cylinder using water as a refrigerant, the variation in water temperature in the cooling cylinder or the upper part of the cooling cylinder There were problems in terms of moldability and surface smoothness of optical cable spacers, balance between cooling and production speed, such as the interface state of the water surface affecting the molding conditions.
[0015]
The object of the present invention is to form the spacer main body covering layer for an optical cable from PBT resin or a mixture of it and PC resin, the outer diameter of the main body covering layer is as small as 5 mm or less, and the thickness of the groove bottom portion of the main body covering is thin. In such a case, an object of the present invention is to provide a method for manufacturing an optical cable spacer with improved surface smoothness in the optical fiber housing groove.
[0021]
In order to achieve the above object, the present invention provides a tensile body, a preliminary coating layer made of a thermoplastic resin that covers the outer periphery of the tensile body, and a thermal groove so as to form a spiral groove on the outer periphery of the preliminary coating layer. A main body coating layer coated with a plastic resin, and the main body coating layer is made of polybutylene terephthalate (PBT) resin or a mixture of PBT resin and polycarbonate (PC) resin, and the preliminary coating layer is made of the main body coating layer. And a method for producing a spacer for an optical fiber cable, wherein the outer periphery of the preliminary coating layer and the inner periphery of the main body coating layer are fused and bonded, and formed of an adhesive polyester-based thermoplastic resin having a high compatibility with The cooling of the main body coating layer is performed by using a thermoplastic resin extruded vertically downward, with a distance between the water surface and the rotary die of 10 mm or less, and cooling water adjusted to a temperature of 30 ° C. or less. It is conducted by guiding it into a cooling cylinder that circulates as an upward flow facing the traveling direction of the thermoplastic resin. At this time, the running speed of the thermoplastic resin extruded vertically downward is V0, and the flow speed of the opposing cooling water the speed ratio Vw / V0 in the case of the Vw is 0.02 or more and 0.3 or less.
[0022]
In this case, the PBT resin and the mixture of the PBT resin and the PC resin that form the spacer main body coating layer have a higher crystallization speed and a lower thermal shrinkage rate at the time of molding than the conventionally used polyethylene resin. It has been found that the target shape can be obtained more easily when it is cooled rapidly.
[0023]
Therefore, the tensile strength member coated with the preliminary coating layer is introduced into the rotary die cross head by vertical pulling, the cooling cylinder is filled with cooling water, and the distance between the upper surface of the water surface and the rotary die is set to 10 mm or less to cool rapidly. .
[0024]
A surfactant is added to the cooling water, and the thermoplastic resin and wettability of the extruded main body coating layer are improved, so that cooling solidification progresses from a uniform position and the optical fiber spacer has a stable size. Is obtained.
[0025]
In addition, since the spacer extruded from the rotary die is very hot, bumping occurs at the interface between the main body coating layer and the cooling water, and cooling is caused by splashing into the thermoplastic resin of the rotary die or main body coating layer. If water adheres, the shape of the spacer may be adversely affected.
[0026]
Therefore, the cooling cylinder is heated from below to above 30 ° C., preferably from 5 ° C. to 25 ° C., more preferably from 10 ° C. to 20 ° C. Always supply a laminar flow.
[0027]
The flow rate and flow rate of the cooling water flowing through the cooling cylinder depend on the extrusion molding temperature and the amount of extrusion. When the flow rate is Vw, the ratio Vw / V0 to the travel speed V0 of the molded product is 0.02. The range is -0.3.
[0028]
Here, when Vw / V0 is less than 0.02, the coolant temperature rises due to the introduced high-temperature molded product, the molded product becomes insufficiently cooled, rib collapse occurs, and molding stability decreases. To do.
[0029]
On the other hand, if Vw / V0 exceeds 0.3, the water surface on the top of the cooling cylinder undulates due to the excessive increase in the counter flow velocity in the cooling cylinder. The surface cannot be formed smoothly.
[0030]
The present invention can also be applied to an SZ twist slot in which the twist direction of the optical fiber housing groove is twisted in one direction or alternately reversed at a predetermined angle.
[0031]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described based on examples. FIG. 1 shows an example of an optical cable spacer obtained by the manufacturing method according to the present invention. The spacer 10 shown in the figure includes a strength member 12, a preliminary coating layer 14, and a main body coating layer 16.
[0032]
The strength member 12 is a linear body having a substantially circular cross section, and is made of, for example, a single steel wire. The preliminary coating layer 14 covers the outer periphery of the strength member 12 and is made of a thermoplastic resin. The main body coating layer 16 is formed by coating with a thermoplastic resin so as to form a plurality of spiral grooves 18 on the outer periphery of the preliminary coating layer 14.
[0033]
In the case of the present embodiment, the main body coating layer 16 is composed of polybutylene terephthalate (PBT) resin or a mixture of PBT resin and polycarbonate (PC) resin.
[0034]
The preliminary coating layer 14 is formed of an adhesive polyester thermoplastic resin having a high compatibility with the main body coating layer 16, and the outer periphery of the preliminary coating layer 14 and the inner periphery of the main body coating layer 16 are fused and bonded. Yes.
[0035]
The distance between the groove bottom assumed outer diameter D1 determined by the inscribed circle of the groove bottom of the spiral groove 18 and the outer diameter D2 of the preliminary coating layer is the groove bottom thickness d. In the case of the present embodiment, the outer diameter of the main body coating layer 16 is 5 mm or less, and the groove bottom thickness d is set in the range of 0.15 to 1.0 mm. The center line average surface roughness of the groove bottom of the spiral groove 18 is 0.8 μm or less.
[0036]
FIG. 2 shows an embodiment of a manufacturing method for manufacturing the optical cable spacer 10 having the above-described configuration. In the spacer 10 having the cross-sectional shape shown in FIG. 1, first, an adhesive polyester resin is extrusion coated on the outer periphery of the strength member 12 to form a preliminary coating layer 14, thereby producing a coated strength member 15.
[0037]
Next, the coated tensile body 15 is preheated to a predetermined temperature, and passed through the crosshead die 20 having a spacer-shaped mold having spiral grooves and rib portions at a speed of V0 m / min, Then, PBT resin or mixed C resin in which this and PC resin are mixed at a predetermined ratio is extruded and coated while rotating the die in a molten state to form the main body coating layer 16.
[0038]
The spacer 10 on which the main body coating layer 16 is formed is inserted into the cooling cylinder 22 and cooled. The cooling of the main body coating layer 16 is performed by a cooling cylinder in which a cooling water W whose temperature has been adjusted to 30 ° C. or less is circulated as an upward flow opposite to the traveling direction of the thermoplastic resin. This is done by inserting it into 22.
[0039]
At this time, the speed ratio Vw / V0 is 0.02 or more and 0.3 or less when the traveling speed of the thermoplastic resin extruded vertically downward is V0 and the flow speed of the opposing cooling water W is Vw. Like that.
[0040]
The cooling cylinder 22 is circulated and supplied with the cooling water W by the pump P, the cooling water W overflows from the upper end side, the cooling cylinder 22 is filled with the cooling water W, the upper end of the water surface in the cylinder and the rotary die 26. When the distance l is set to 10 mm or less, the cooling is rapidly performed. 2 is a support portion of the cooling cylinder 22, and the support portion can be adjusted in the distance l by operating the handle.
[0041]
By adding a surfactant to the cooling water W to improve the wettability and the thermoplastic resin of the extruded body covering layer 16, the solidification of cooling progresses from a uniform position and light with a stable size. A fiber spacer 10 is obtained.
[0042]
Further, since the spacer 10 extruded from the rotary die 26 has a very high temperature immediately after extrusion, bumping occurs at the interface between the main body coating layer 16 and the cooling water W, and the rotary die 26 or the main body coating layer is generated. If the cooling water W scattered by bumping on the 16 thermoplastic resin adheres, the shape of the spacer 10 may be adversely affected.
[0043]
In order to avoid this, the cooling cylinder 22 is supplied with cooling water W whose temperature is adjusted to 30 ° C. or less, preferably 5 ° C. to 25 ° C., more preferably 10 ° C. to 20 ° C., inside the cooling cylinder 22. It is always supplied so as to become a laminar flow in an upward flow from the lower side to the upper side facing the traveling.
[0044]
More specific examples of the manufacturing method for obtaining the optical cable spacer 10 having the above-described configuration will be described below together with comparative examples.
[0045]
Example 1 (PBT resin: PC resin = 5: 5)
A precoating layer is formed by extrusion coating an adhesive polyester resin (Toyobo Co., Ltd .: Byron GA1300) on the outer periphery of a blueing steel wire (strength body) having a wire diameter of 1.2 mm, and an outer diameter of 1.3 mm. A coated steel wire was obtained.
[0046]
Next, this coated steel wire is preheated until the surface temperature reaches 60 ° C., and is passed through a crosshead die having a spacer-shaped mold having a spiral groove and a rib portion at a speed of 10 m / min. PBT / PC resin (manufactured by Teijin: H7500) in which PBT resin and PC resin were mixed at a ratio of 5: 5 was extrusion coated while rotating the die in a molten state at 260 ° C., and this was immediately put into a tube having an inner diameter of 70 mm. In addition, 0.1% of a surfactant (manufactured by Matsumoto Yushi Seiyaku: Marpon FL-30) was added and cooling water adjusted to 15 ° C. was supplied at an upward flow rate of 3 L / min and overflowed from the upper end. It was introduced into the cooling cylinder and cooled and solidified (distance 7 mm from the rotating die to the cooling water surface) to obtain an optical cable spacer in which a unidirectional twisted spiral groove was formed.
[0047]
In this case, the speed ratio Vw / V0 was 0.078 when the traveling speed of the thermoplastic resin extruded vertically downward was V0 and the flow speed of the opposing cooling water was Vw.
[0048]
The resulting optical cable spacer has a spiral shape of three U-shaped cross-sections with an outer diameter of the rib portion of 4.8 mm, a groove width of 1.6 mm, a groove depth of 1.2 mm, and a groove bottom thickness of 0.3 mm. The pitch with one groove was 300 mm. The centerline average roughness Ra of the groove bottom of the spacer thus obtained was measured and found to be 0.24 μm.
[0049]
Example 2 (PBT resin)
An optical fiber spacer having a unidirectional twisted spiral groove was obtained under the same conditions as in Example 1 except that PBT resin (manufactured by Teijin: C-7000FN) was used as the main body coating resin.
[0050]
The dimensions of the optical cable spacer are three spiral U-shaped cross-sections 18 having a rib portion outer diameter of 4.8 mm, a groove width of 1.6 mm, a groove depth of 1.2 mm, and a groove bottom thickness of 0.3 mm. The pitch for one rotation was 300 mm. The centerline average roughness Ra of the groove bottom of the spacer thus obtained was measured and found to be 0.28 μm.
[0051]
Comparative Example 1 (PBT resin: PC resin = 5: 5, turbulent flow)
A pre-coating layer is formed by extrusion coating an adhesive polyester resin (Toyobo Co., Ltd .: Byron GA1300) on the outer periphery of a blueing steel wire having a wire diameter of 1.2 mm, and a coated steel wire having an outer diameter of 1.3 mm is formed. Obtained.
[0052]
Next, this coated steel wire is preheated until the surface temperature reaches 60 ° C., and is passed through a crosshead die having a spacer-shaped mold having spiral grooves and rib portions at a production rate of 10 m / min. PBT / PC resin (manufactured by Teijin: H7500) was extrusion coated while rotating the die in a molten state at 260 ° C., and this was immediately applied (distance 7 mm from the rotating die to the cooling water surface) in a 70 mm diameter tube with surface activity. In a cooling cylinder overflowing from the upper end of the coolant (Matsumoto Yushi Seiyaku Co., Ltd .: Marpone FL-30) with 0.1% added and cooling water adjusted to 15 ° C. at a flow rate of 20 L / min. And solidified by cooling to obtain an optical cable spacer in which a unidirectional twisted spiral groove was formed.
[0053]
In this case, the speed ratio Vw / V0 was 0.52 when the running speed of the thermoplastic resin extruded vertically downward was V0 and the flow speed of the opposing cooling water was Vw.
[0054]
The dimensions and shape of the obtained optical cable spacer are three strips having an outer diameter of the rib portion of 4.7 to 4.9 mm, a groove width of 1.6 mm, a groove depth of 1.2 mm, and a groove bottom thickness of 0.3 mm. It had a helical groove with a letter-shaped cross section, and the pitch for one rotation was 300 mm.
[0055]
On the surface of the spacer thus obtained, there was a portion where the outer diameter of the spacer was not stable because the water surface above the cooling cylinder was undulated and the cooling start point was not constant.
[0056]
Comparative Example 2 (PBT resin: PC resin = 5: 5, insufficient cooling)
A pre-coating layer is formed by extrusion coating an adhesive polyester resin (Toyobo Co., Ltd .: Byron GA1300) on the outer periphery of a blueing steel wire having a wire diameter of 1.2 mm, and a coated steel wire having an outer diameter of 1.3 mm is formed. Obtained.
[0057]
Next, this coated steel wire is preheated until the surface temperature reaches 60 ° C., and a crosshead die having a spacer-shaped die having a spiral groove and a rib portion is passed at a speed of 20 m / min. PBT / PC resin (manufactured by Teijin: H7500) was extruded and coated in a molten state at 260 ° C. while rotating the die, and immediately (distance 7 mm from the rotating die to the cooling water surface) in a 70 mm diameter tube, the surfactant (Matsumoto Yushi Seiyaku Co., Ltd .: Marpon FL-30) is added to 0.1% cooling water temperature adjusted to 15 ℃, is supplied at an ascending flow rate of 0.5 L / min, and the cooling cylinder overflows from the upper end It was introduced into the inside and cooled and solidified to obtain an optical cable spacer in which a unidirectional twisted spiral groove was formed.
[0058]
In this case, the speed ratio Vw / V0 was 0.006 when the traveling speed of the thermoplastic resin extruded vertically downward was V0 and the flow speed of the opposing cooling water was Vw.
[0059]
The resulting optical cable spacer has a spiral shape of three U-shaped cross-sections with an outer diameter of the rib portion of 4.8 mm, a groove width of 1.6 mm, a groove depth of 1.2 mm, and a groove bottom thickness of 0.3 mm. The pitch with one groove was 300 mm.
[0060]
Under such cooling conditions, when the cooling water supplied at 15 ° C. from below the cooling cylinder overflowed above the cooling cylinder, the water temperature rose to 42 ° C. The surface state of the obtained optical cable spacer was very rough because it was fluttered under the influence of bumping generated on the water surface above the cooling cylinder. Such a spacer is not suitable for housing an optical fiber.
[0061]
Comparative Example 3 (PBT resin: PC resin = 5: 5, cooling water 40 ° C.)
A pre-coating layer is formed by extrusion coating an adhesive polyester resin (Toyobo Co., Ltd .: Byron GA1300) on the outer periphery of a blueing steel wire having a wire diameter of 1.2 mm, and a coated steel wire having an outer diameter of 1.3 mm is formed. Obtained.
[0062]
Next, this coated steel wire is preheated until the surface temperature reaches 60 ° C., and is passed through a crosshead die having a spacer-shaped mold having a spiral groove and a rib portion at a speed of 10 m / min. PBT / PC resin (manufactured by Teijin: H7500) was extruded and coated in a molten state at 260 ° C. while rotating the die, and immediately (distance 7 mm from the rotating die to the cooling water surface) in a 70 mm diameter tube, the surfactant (Matsumoto Yushi Seiyaku Co., Ltd .: Marpon FL-30) is added in 0.1% and the cooling water temperature-controlled at 40 ° C. is supplied in an ascending flow with a flow rate of 3 L / min. And solidified by cooling to obtain an optical cable spacer in which a unidirectional twisted spiral groove was formed.
[0063]
In this case, the speed ratio Vw / V0 was 0.078 when the traveling speed of the thermoplastic resin extruded vertically downward was V0 and the flow speed of the opposing cooling water was Vw.
[0064]
The surface state of the obtained optical cable spacer was very rough because it was fluttered under the influence of bumping generated on the water surface above the cooling cylinder. Such a spacer is not suitable for housing an optical fiber.
[0065]
Comparative Example 4 (PBT resin: PC resin = 5: 5, thin groove bottom thickness, Ra = defect)
A precoated layer is formed by extrusion coating an adhesive polyester resin (Toyobo Co., Ltd .: Byron GA1300) on the outer periphery of a blueing steel wire having a wire diameter of 1.6 mm, and a coated steel wire having an outer diameter of 1.7 mm is formed. Obtained.
[0066]
Next, the coated steel wire is preheated until the surface temperature reaches 60 ° C., and is passed through a crosshead die having a spacer-shaped mold having a spiral groove and a rib portion, and a PBT / PC resin ( Teijin: H7500) was extruded and coated in a molten state at 260 ° C. while rotating the die, and immediately (distance 7 mm from the rotating die to the cooling water surface) in a 70 mm diameter tube (made by Matsumoto Yushi Seiyaku) : Marpone FL-30) is added at 0.1% and the temperature is adjusted to 15 ° C. The cooling water is supplied at an upward flow rate of 3 L / min, and is introduced into the cooling cylinder overflowed from the upper end to cool and solidify. Thus, an optical cable spacer having a unidirectional twisted spiral groove was obtained. (Production speed 10m / min)
[0067]
In this case, the speed ratio Vw / V0 was 0.078 when the traveling speed of the thermoplastic resin extruded vertically downward was V0 and the flow speed of the opposing cooling water was Vw.
[0068]
The resulting optical cable spacer has a spiral shape with three U-shaped cross sections each having an outer diameter of 4.8 mm, a groove width of 1.6 mm, a groove depth of 1.2 mm, and a groove bottom thickness of 0.1 mm. The pitch with one groove was 300 mm.
[0069]
The centerline average roughness Ra of the spacer groove bottom thus obtained was 1.80 μm. When the groove bottom state is not smooth as described above, there is a concern that the optical fiber disposed in the groove of the spacer is affected to cause microbending and increase transmission loss.
[0070]
Comparative Example 5 (PBT resin: PC resin = 5: 5, groove bottom thickness is thin, groove bottom shape = defect)
A pre-coating layer is formed by extrusion coating an adhesive polyester resin (Toyobo Co., Ltd .: Byron GA1300) on the outer periphery of a blueing steel wire having a wire diameter of 1.2 mm, and a coated steel wire having an outer diameter of 1.3 mm is formed. Obtained.
[0071]
Next, this coated steel wire is preheated until the surface temperature reaches 60 ° C., and is passed through a crosshead die having a spacer-shaped mold having a spiral groove and a rib portion at a speed of 10 m / min. PBT / PC resin (manufactured by Teijin: H7500) was extruded and coated in a molten state at 260 ° C. while rotating the die, and immediately (distance 7 mm from the rotating die to the cooling water surface) in a 70 mm diameter tube, the surfactant (Matsumoto Yushi Seiyaku Co., Ltd .: Marpon FL-30) is added to the cooling cylinder, which is 0.1% added and supplied at a flow rate of 3 L / min. It was introduced and solidified by cooling to obtain an optical cable spacer in which a unidirectional twisted spiral groove was formed.
[0072]
In this case, the speed ratio Vw / V0 was 0.078 when the traveling speed of the thermoplastic resin extruded vertically downward was V0 and the flow speed of the opposing cooling water was Vw.
[0073]
The target size and shape of the optical cable spacer is a spiral of three U-shaped cross-sections with an outer diameter of the rib portion of 4.8 mm, a groove width of 1.6 mm, a groove depth of 1.4 mm, and a groove bottom thickness of 0.1 mm. However, the obtained optical cable spacer was raised by the effect of the coated steel wire introduced as a strength member, and the actual groove bottom thickness was 0.15 mm.
[0074]
If the groove bottom shape is not flat in this way, when assembling the optical fibers, the optical fibers are biased in the spacer grooves, and stress is applied to the optical fibers to cause microbending, which increases transmission loss. There is a fear.
[0075]
【The invention's effect】
As described above in detail in the embodiments, according to the method for manufacturing an optical cable spacer according to the present invention, the main body covering layer is made of PBT resin or a mixture of it and PC resin, and the outer surface of the main body covering layer is formed. When the diameter is as small as 5 mm or less and the thickness of the groove bottom portion of the main body coating is thin, the surface smoothness in the optical fiber housing groove can be improved.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing an embodiment of an optical cable spacer according to the present invention.
FIG. 2 is an explanatory view showing an example of a manufacturing method of an optical cable spacer according to the present invention.
[Brief description of symbols]
DESCRIPTION OF SYMBOLS 10 Optical cable spacer 12 Strength member 14 Preliminary coating layer 16 Main body coating layer 18 Spiral groove

Claims (1)

A tensile body, a preliminary coating layer made of a thermoplastic resin covering the outer periphery of the tensile body, and a main body coating layer coated with a thermoplastic resin so as to form a spiral groove on the outer periphery of the preliminary coating layer ,
The main body coating layer is composed of polybutylene terephthalate (PBT) resin or a mixture of PBT resin and polycarbonate (PC) resin,
For an optical fiber cable in which the preliminary coating layer is formed of an adhesive polyester thermoplastic resin having a high compatibility with the main body coating layer, and the outer periphery of the preliminary coating layer and the inner periphery of the main body coating layer are fused and bonded. A method for manufacturing a spacer, comprising:
The cooling of the main body covering layer is performed by using a thermoplastic resin extruded vertically downward, and a cooling water whose temperature between the water surface and the rotating die is 10 mm or less and whose temperature is adjusted to 30 ° C. or less is the thermoplastic resin. In the case where the flow rate of the thermoplastic resin extruded vertically downward is V0 and the flow rate of the opposite cooling water is Vw. Speed ratio Vw / V0 is 0.02 or more and 0.3 or less, The manufacturing method of the spacer for optical cables characterized by the above-mentioned.

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