JP2995920B2 - Heat treatment method and apparatus for plastic optical fiber - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat treatment method and a heat treatment apparatus effective for producing a plastic optical fiber having excellent uniformity of yarn diameter in the longitudinal direction of the fiber.

[0002] More specifically, the present invention relates to a heat treatment method and a heat treatment apparatus for suppressing the unevenness in the yarn longitudinal direction of a plastic optical fiber by optimizing the flow method of a heating fluid when heat-treating the plastic optical fiber. Things.

[0003]

2. Description of the Related Art Generally, after a thermoplastic polymer is melted, discharged from a molding die and solidified by cooling, the undrawn fiber is drawn or heat-treated.
The stretching is, for example, to orient the polymer chains in the fiber axis direction, and to impart mechanical properties, especially properties suitable for the purpose, such as to improve flexibility and bending resistance. The heat treatment after the stretching is performed for the purpose of improving dimensional stability and the like.

[0004] It is important that the drawing and heat treatment in the yarn forming process be performed without deteriorating the uniformity of the thickness of the yarn, and various attempts have been made for that purpose.

For example, various conditions such as the surface material and shape of the roller, the rotation speed, the method of supplying a heating medium (such as heated air) (temperature, flow rate, flow direction, etc.), and the material of guides are constantly determined. There is a method of making the thickness in the longitudinal direction of the yarn uniform by controlling the thickness in the longitudinal direction. This method is quite effective for general fibers such as polyamide fibers and polyester fibers, and many proposals have been made for setting their optimum conditions.

[0006] The uniformity of the yarn diameter is extremely important also in a plastic optical fiber used for optical communication, an optical sensor, a light guide, a decoration, etc. In particular, when a plastic optical fiber is inserted into an optical connector, It is strongly required when optical fibers are joined to each other, or when they are inserted into a joining base for a light guide or an optical sensor.

This plastic optical fiber uses a polymer having excellent transparency such as polymethyl methacrylate, polystyrene or polycarbonate as a core material, and a polymer having a lower refractive index than the core material as a sheath material. Is concentric 2
It is generally manufactured by a method of spinning three to three layers, stretching for the purpose of improving mechanical properties, and, if necessary, heat-treating for the purpose of imparting dimensional stability, followed by winding (FIG. 6).

In such a method for melt-spinning a plastic optical fiber, as means for improving the uniformity of the fiber diameter, for example, as described in JP-B-56-49324, a core component and a sheath component are used. The method of controlling the melt flow index at the spinning temperature in an appropriate range, and the primary side of a metering gear pump in order to obtain uniformity in the fiber length direction as described in JP-B-2-24923. Methods for keeping the polymer pressure constant have been proposed.

Further, in the drawing and heat treatment performed after the melt spinning of a plastic optical fiber, Japanese Patent Laid-Open No.
-131206, a method of stretching in a non-contact heating zone in which a heated airflow flows in a countercurrent direction, and an outlet of a non-contact heating stretching zone as described in JP-A-2-68503. A method of blowing cooling air in the vicinity, or a method of optimizing stretching conditions such as the length of a non-contact heating stretching area and the speed of passing through the heating stretching area as described in JP-A-63-303304. Etc. have been proposed.

[0010]

However, it is difficult to sufficiently control the uniformity of the plastic optical fiber in the longitudinal direction of the fiber by the above-described conventional method.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a heat treatment method and an apparatus for the heat treatment that can sufficiently suppress the yarn diameter unevenness in the longitudinal direction of the plastic optical fiber.

By obtaining a plastic optical fiber having excellent yarn diameter uniformity in the longitudinal direction of the fiber, it is possible to suppress the occurrence of trouble during high-order processing and the generation of high-order processed products having defects. It is an object of the present invention to improve the handleability of an operation of inserting a plastic optical fiber into an optical connector, an operation of joining optical fibers to each other, an operation of inserting a plastic optical fiber into a joint base, and the like.

[0013]

To achieve these objects, the present invention comprises the following arrangement.

In the heat treatment method for a plastic optical fiber according to the present invention, when the plastic optical fiber running in a non-contact manner in the heat treatment zone is heat-treated with the heating gas, the heating gas and the plastic optical fiber are countercurrently flowed in the heat treatment zone. The method is characterized in that the flow direction of the heated gas in the heat treatment zone is changed by a plurality of convex members provided in contact with each other and on the opposite inner surfaces of the heat treatment zone.

According to a second aspect of the present invention, there is provided a heat treatment method for a plastic optical fiber, wherein the heat treatment method according to the first aspect is used for heating and drawing an undrawn yarn of a spun plastic optical fiber, and the draw ratio is 1.5 to 3.0 times. And a winding speed (Vm / min) of 5 / d <V <30 / d ² (d = yarn diameter (mm) of the drawn plastic optical fiber).

According to a third aspect of the present invention, there is provided a heat treatment method for a plastic optical fiber, wherein the heat treatment method according to the first aspect is used for heat treatment of a drawn plastic optical fiber. 0.95-
1.05.

Further, in the heat treatment apparatus for a plastic optical fiber according to the present invention, the yarn path which forms the heat treatment zone of the traveling plastic optical fiber, and the plastic optical fiber is heated from the periphery of the plastic optical fiber at the exit of the plastic optical fiber in the yarn path. An outlet for discharging gas, a suction port for sucking heated gas flowing in the yarn path in a counter-current direction at a plastic optical fiber inlet portion of the yarn path, and heating to an opposing surface in the yarn path. It is characterized by comprising convex members for gas streamline conversion provided alternately along the gas flow direction.

Hereinafter, the present invention will be described with reference to the drawings showing one embodiment thereof.

FIGS. 1 and 2 are schematic longitudinal sectional views illustrating a heat treatment apparatus according to claim 4 used in the heat treatment method of the present invention.

FIG. 3 is a schematic longitudinal sectional view illustrating a part of the inside of the heat treatment zone in the heat treatment apparatus of FIGS. 1 and 2 in an enlarged manner, and FIG. 4 is a view similar to FIG. FIG. 7 is a partially enlarged view showing another embodiment of the arrangement of the convex members for gas streamline conversion.

FIG. 5 is a perspective view illustrating the shapes of the convex members 4 and 5.

In FIGS. 1 and 2, the yarn path forming the heat treatment zone is constituted by heat retaining plate heaters 1 and 2 around its periphery. A plastic optical fiber (not shown) enters the heat treatment zone through inlet 13 and
Take exit 14. The heated gas 3 is ejected from upper and lower outlets 17 and 18 provided in the vicinity of the outlet 14, and a resistance plate (rectifying plate) for rectification, a honeycomb, a filter, or the like is provided at the outlet. (Not shown).

The heating gas 3 is supplied to the heater 1 for gas heating.
6 and is blown out by the blower fan 15
Sent to The gas heater 16 may be provided after the blower fan 15 as shown in FIG.
It may be provided in front of the blower fan 15 as described above.

The heating gas 3 may be blown out from one of the upper and lower outlets, or from both upper and lower outlets as shown. Above all,
It is advantageous to adjust the ejection amount of the upper and lower jets and to jet the jet from both the upper and lower sides in order to reduce the yaw of the plastic optical fiber (bundle).

The heating gas 3 ejected from the outlets 17 and 18 flows in a direction from the outlet 14 to the inlet 13 of the heating zone, that is, a plastic optical fiber (not shown).
Flows in the countercurrent direction to the traveling direction of the
It is sucked from 9 and 20 and circulated toward the heating heater 16 or the blower fan 15. A part of the circulated heating gas 3 leaks from the inlet 13 or the outlet 14 of the heating zone. Conversely, outside air is taken in from one of the ports by the wind pressure balance, and the circulating air volume becomes constant.

The heated gas flowing in the heat treatment zone flows in a meandering manner while the streamlines are alternately changed by a plurality of convex members provided on the opposite inner surfaces of the yarn path.

The yarn path forming the heat treatment zone is preferably a rectangular parallelepiped with a rectangular cross section, since the streamline of the heated gas is alternately converted by the convex member on the inner surface thereof. It may be convex or concave. In addition, as long as there is an opposing inner surface, it may have another cross-sectional shape, for example, a hexagonal cross-section.

Next, referring to FIGS. 3, 4 and 5, which show a part of the inside of the heat treatment zone in an enlarged manner, the meandering flow of the heating gas in the method of the present invention and the gas flow line conversion in the apparatus of the present invention will be described. Will be described.

An upper convex member 4 is provided on the lower surface of the plate heater 1 provided at the upper part of the yarn path, and a lower convex member is provided at the upper surface of the plate heater 2 provided at the lower part of the path. 5 are alternately arranged along the flow direction of the heated gas as shown in FIGS. As shown in FIG. 3, one of these convex members 4 and 5 may be alternately arranged on each of the upper and lower sides. Alternatively, as shown in FIG. May be arranged. The number of the convex members may be appropriately selected according to the form of the yarn path, the type of the plastic optical fiber, the traveling speed, and the like. It may be provided alternately.

In this yarn path (in the heating zone), the plastic optical fiber (bundle) F travels rightward in the figure, while the heated gas 3 blown out from the outlet flows leftward in the figure. Therefore, they come into countercurrent contact. The heated gas 3 flowing in the left direction collides with the upper and lower convex members 4 and 5, and its streamline direction is changed. As a result, the heating fluid 3 has a meandering flow that alternately crosses the plastic optical fiber (bundle) F traveling from the left in the vertical direction in the figure.

The protruding members 4 and 5 have a length which extends over the width of the inner surface of the yarn path where the protruding members 4 and 5 are arranged. For example, a rectangular parallelepiped member as shown in FIGS.
A triangular columnar member as shown in FIG. 5B, a columnar member having concave columnar surfaces as shown in FIG. 5C, an inverted T-shaped columnar member as shown in 5D, and a half as shown in 5E. As shown in the columnar member and 5F, a member having a mesh-shaped convex portion may be used. Except for those illustrated, a pentagonal columnar member, a columnar member having a convex columnar surface, or the like may be used.

The height (h) and installation interval (d) of the convex portion of the convex member depend on conditions such as the shape of the yarn path, the inner surface interval, the flow rate of the heating fluid, and the diameter of the optical fiber (bundle). Generally, the height (h) is about 0.1 to 0.3 times the interval (A) of the inner surface of the yarn path, and the height (h) is the distance (the yarn path between the upper and lower convex members). The distance d) along the longitudinal direction of the passage may be about 0.05 to 0.4 times the entire length of the yarn path.

The conditions such as the cross-sectional shape and dimensions of the convex member in the case of actual use are determined by using the most suitable one according to the conditions such as the shape of the heating zone, the flow rate of the heating fluid, the diameter of the optical fiber (bundle) and the like. Often, it is not restricted by the illustrated member shape or the like.

This heat treatment method may be applied to the heat treatment at the time of the heat drawing, or may be applied to the heat treatment after the drawing.

FIG. 6 is an overall schematic view showing an example of a plastic optical fiber manufacturing process to which this heat treatment method is applied.

The plurality of plastic optical fibers (bundles) F discharged from the composite melt-spinning die 21 are cooled by the orthogonal cooling air 22 to be solidified, and the take-up rolls 2
4, after being wound by the heat treatment device 25,
It is wound around a stretching roll 26. The film is stretched at a stretching ratio determined by the speed ratio between the take-up roll 24 and the stretching roll 26, and then subjected to a constant-length heat treatment or a relaxation heat treatment by a heat treatment device 27 to impart dimensional stability as necessary. 28, nip roll 2
The traverse guide 31 is supplied to a winder, and the tension is controlled by a dancer roll 30 for tension control.

The heat treatment apparatus 25 for stretching the heat treatment of the present invention.
When applied to the above, the draw ratio at that time is 1.5 to 3.
0 times, and the winding speed (Vm / min) is 5 /
When d <V <30 / d ² (d = yarn diameter (mm) of the plastic optical fiber after drawing), the drawing is more uniform and highly advanced, and there is no interface irregularity or interface separation between the core and sheath components. It is preferable to obtain a plastic optical fiber having a small yarn diameter variation and excellent optical transmission properties. When the stretching ratio is less than 1.5 times or when the winding speed V is less than 5 / d, the optical fiber has poor bending resistance. Conversely, the draw ratio is 3.
When it exceeds 0 times or when the winding speed V exceeds 30 / d ² , it is not preferable in suppressing the yarn diameter fluctuation.

When the heat treatment of the present invention is applied to the heat treatment apparatus 27 after stretching, the peripheral speed ratio between the rollers arranged before and after the heat treatment zone, that is, the stretching roll 26 and the heat treatment roll 28 in FIG. Is preferably set to 0.95 to 1.05.

[0039]

When the heat treatment is performed by the method of the present invention, the heating gas 3 in countercurrent contact with the plastic optical fiber (bundle) F running in the heat treatment zone is converted into a streamline by the upper and lower convex members, and flows through the heat treatment zone. It flows meandering largely and alternately crosses the optical fiber (bundle) F in the vertical direction. By alternately traversing the traveling optical fiber (bundle) F, heat exchange between the optical fiber and the heating gas is promoted, and a sufficient heat treatment effect can be given to the optical fiber. The temperature unevenness in the width direction inside can be eliminated.

Together with these effects, the fluctuation of the yarn diameter in the longitudinal direction of the optical fiber can be greatly reduced, and a remarkable effect is exhibited particularly in the heat treatment involving non-contact drawing in the heating zone. .

That is, in the non-stretched optical fiber before the non-contact stretching, there is generally a sinusoidal yarn diameter variation due to a variation in discharge of the metering gear pump or the like. When this unstretched optical fiber is guided into the heating zone, and non-contact stretching is performed by a traction force based on the speed difference between the rollers before and after the unstretched optical fiber, the generated stretching stress is first concentrated on the small diameter portion of the optical fiber. , And then propagated to the large diameter portion. The larger the stretching stress at that time, the larger the diameter of the optical fiber /
The ratio of the small diameter becomes large, that is, the fluctuation of the yarn diameter in the longitudinal direction of the optical fiber becomes large. The heat treatment of the present invention promotes heat exchange between the optical fiber and the heated gas,
When the temperature unevenness in the heating zone is reduced, the heat treatment effect of the optical fiber is enhanced, and the stretching stress of the optical fiber can be reduced. As a result, the ratio of the large diameter / small diameter of the optical fiber can be suppressed during the heat drawing, the fluctuation of the yarn diameter in the longitudinal direction of the optical fiber can be suppressed, and a plastic optical fiber with high uniform yarn diameter can be obtained. It is.

The heat treatment according to the present invention is also effective as a heat treatment after drawing. In this case, as in the case of heating and drawing, the heat exchange between the optical fiber and the heating gas is promoted, and Is given a sufficient heat treatment effect,
Further, it is considered that the fluctuation of the yarn diameter in the longitudinal direction of the optical fiber can be suppressed by eliminating the temperature unevenness in the width direction in the heat treatment zone.

Further, in the heat treatment apparatus of the present invention, a meandering flow alternately traversing the optical fiber can be easily given to the heated gas.

[0044]

【Example】

Example 1 A radical polymerization reaction initiator and a chain transfer agent were added to sufficiently purified commercially available methyl methacrylate to carry out continuous bulk radical polymerization, and then the mixture was subjected to unmixing using a uniaxial vent-type extruder. The reaction monomer and the like were removed to produce polymethyl methacrylate having a weight average molecular weight of 83,000 and a residual monomer content of 0.24% by weight. This polymethyl methacrylate was continuously supplied as a core component, and a commercially available polyvinylidene fluoride / tetrafluoromethacrylate was used as a sheath component, followed by melt-spinning at 235 ° C. by the optical fiber manufacturing process shown in FIG. An undrawn plastic optical fiber having a thread diameter of 1414 μm on the roll 24 was produced.

Subsequently, the unstretched plastic optical fiber was introduced into a hot air circulation type heating furnace shown in FIGS. 2 and 3, and was heated at a flow rate of a heating gas of 10 m / sec, at a temperature of 165.degree. Introduced into the same hot air circulating heating furnace at 170 ° C for the purpose of imparting dimensional stability by stretching by heating, and performing non-contact constant-length heat treatment at a peripheral speed ratio of 0.995 before and after the roller. Winding was performed at a rate of 15 m / min with a constant tension winder to obtain a drawn plastic optical fiber having a yarn diameter of 1000 μm.

At this time, the yarn path of the hot-air circulation type heating furnace is in the shape of a rectangular parallelepiped, and the upper and lower surfaces thereof extend laterally in FIG.
Is provided.

The yarn diameter variation width R μm of the obtained drawn plastic optical fiber was measured using a laser diode type outer diameter measuring device manufactured by Keyence Corporation.
It was as small as 36 μm per 00 m.

Comparative Example 1 A plastic optical fiber was manufactured in the same manner as in Example 1 except that the convex members on the upper and lower surfaces of the hot air circulation type heating furnace used in Example 1 were removed. The variation width of the yarn diameter of the obtained optical fiber was as large as 47 μm per 1500 m of the yarn length.

[0049]

According to the present invention, when the heat treatment is performed, a sufficient heat treatment effect can be given to the optical fiber.
Eliminating the temperature unevenness in the width direction in the heat treatment zone, it is possible to suppress the fluctuation of the yarn diameter in the longitudinal direction of the fiber when performing non-contact heat drawing or non-contact heat treatment, and it is excellent in yarn diameter uniformity. Optical fiber can be formed. Therefore, it is possible to greatly reduce the occurrence of trouble during high-order processing and the occurrence of defects in high-order processed products, and to insert plastic optical fibers into optical connectors, and to use as joint guides for light guides and optical sensors. It is possible to improve the ease of handling in the insertion work of the device.

[Brief description of the drawings]

FIG. 1 is a schematic longitudinal sectional view illustrating a heat treatment apparatus according to claim 4 used in the present invention.

FIG. 2 is a schematic longitudinal sectional view illustrating a heat treatment apparatus according to claim 4 used in the present invention, and shows an embodiment different from FIG. 2;

FIG. 3 is a schematic longitudinal sectional view illustrating an enlarged part of a heat treatment zone in a heat treatment apparatus used in the present invention.

FIG. 4 is a schematic longitudinal sectional view illustrating an enlarged part of a heat treatment zone in the heat treatment apparatus used in the present invention, and shows an embodiment different from FIG. 3;

FIG. 5 is a perspective view showing a representative example of a convex member provided in the width direction of the upper and lower surfaces of the yarn path in the heat treatment apparatus of claim 4;

FIG. 6 is an overall schematic view showing an example of a plastic optical fiber manufacturing process to which the heat treatment method of the present invention is applied.

[Explanation of symbols]

1, 2: a member surrounding the thread passage (heat-insulating plate heater) 3: heated gas (flow direction) 4, 5: convex member F: plastic optical fiber 17, 18: heated gas outlet 19, 20: Heated gas inlet

Continuation of the front page (56) References JP-A-62-238986 (JP, A) JP-A-2-68503 (JP, A) JP-A-62-299912 (JP, A) Utility model registration 2519962 (JP, Y2) (58) Fields investigated (Int.Cl. ⁶ , DB name) G02B ⁶ /00-6/54 B29C 35/00-35/18 B29C 55/00-55/30 D02J 1/00-13/00

Claims (4)

(57) [Claims] When a plastic optical fiber running in a non-contact manner in a heat treatment zone is heat-treated with a heating gas, the heating gas and the plastic optical fiber are brought into countercurrent contact with each other in the heat treatment zone. A method for heat-treating a plastic optical fiber, characterized in that a streamline direction of a heated gas in a heat-treatment zone is changed by a plurality of convex members provided on the inner surface. 2. When the heat treatment method according to claim 1 is used for heating and drawing an undrawn yarn of a spun plastic optical fiber, the drawing ratio is 1.5 to 3.0 times, and the winding speed (Vm / (D) = 5 / d <V <30 / d ² (d = yarn diameter (mm) of the drawn plastic optical fiber). 3. When the heat treatment method according to claim 1 is used for heat treatment of a drawn plastic optical fiber, the peripheral speed ratio of the rollers disposed before and after the heat treatment zone is set to 0.
A heat treatment method for a plastic optical fiber, wherein the heat treatment temperature is 95 to 1.05. 4. A yarn path for forming a heat treatment zone of a traveling plastic optical fiber, an outlet for ejecting a heating gas from around the plastic optical fiber in the vicinity of the plastic optical fiber outlet of the yarn path, the yarn path. A suction port for inhaling the heated gas flowing in the yarn path in the counterflow direction at the plastic optical fiber inlet portion of
A heat treatment apparatus for a plastic optical fiber, comprising: convex portions for gas flow line conversion provided alternately along the flow direction of the heated gas on opposing inner surfaces of the yarn path.