JPH0268503A - Production of plastic optical fiber - Google Patents

Abstract

PURPOSE:To provide the plastic optical fiber which is excellent in mechanical properties and particularly in tensile strength and elongation, flex resistance, flexibility, dimensional stability, etc., by blowing cold air to a heating furnace outlet and cooling the optical fiber while discharging a gaseous mixture composed of the cold air and a heating gas leaking out of the heating furnace. CONSTITUTION:The conjugate spun plastic optical fiber 1 passes the inside of the heating furnace continuously in an arrow direction so as to be heat treated. The heating gas in the heating furnace flows from a supply port 16 to an outflow port 17 in the direction reverse from the progressing direction of the optical fiber 1 or in the same direction. The optical fiber 1 is thus heat treated. A contactless type sealing device consisting of a cold air supply opening 24 and a discharge port, 25 which discharges the gaseous mixture composed of the cold air and the heating gas leaking out of the heating furnace is provided to the aperture part of the heating furnace outlet 19. The leakage of the heating gas from the heating furnace is, therefore, eliminated and since the impartation of the cooling effect is possible; therefore, the plastic optical fiber which is improved in the mechanical properties, is decreased in the fluctuation thereof and has excellent light transparency is produced.

Description

[Detailed description of the invention] “Industrial Application Area The present invention relates to a method of manufacturing a plastic optical fiber.

For more details, please refer to various industrial sensors, data links, etc.
The present invention relates to a manufacturing method capable of imparting good mechanical properties and dimensional stability to plastic optical fibers used in short-range communication applications.

[Prior art] Organic optical fibers, that is, plastic optical fibers, are
Glass optics I! Although it has inferior light transmittance compared to fiber, it is inexpensive and easy to handle, so it is becoming widely used for short-distance transmission.

This plastic optical fiber uses a highly transparent polymer such as polymethyl methacrylate, polystyrene, or polycarbonate 1 for the core material, and a polymer with a lower refractive index than the core material for the sheath material. The general manufacturing method is to spin two to three layers of composite material concentrically, stretch it to improve mechanical properties, heat treat it if necessary to give it dimensional stability, and then wind it up. is.

As a method for heat treatment of such plastic optical fibers, we first published Japanese Patent Application No. 6O-271754 (Japanese Unexamined Patent Publication No. 62-1999).
-131206 Publication) and Japanese Patent Application No. 13816/1983
The method proposed in No. 1, using a heating furnace in which heated gas circulates, is generally used in which a plastic optical fiber is passed through the heating furnace in a non-contact manner. Heated gas, heated air, raw steam, superheated steam, or other inert gases are used as the heating medium, but the heat treatment furnace provided for introducing and extracting the plastic optical fiber into the heating furnace is used as the heating medium. By providing a resistance in the opening and sealing it to minimize the inflow of air into the heating furnace or the outflow of heated gas from the heating furnace,
It is necessary to properly maintain the pressure inside the furnace, to make the temperature inside the furnace appropriate and uniform, and to perform appropriate heat treatment to obtain a high-quality plastic optical fiber. Of course, such sealing of the opening not only improves the quality described above, but also immediately leads to energy saving and cost reduction, and has great industrial significance.

[Problems to be Solved by the Invention] By performing such a seal, the amount of heated gas that accompanies the plastic optical fiber that has passed through the heating furnace is considerably reduced. There have been problems in that mechanical properties are likely to deteriorate or vary due to insufficient amounts.

An object of the present invention is to provide a plastic optical fiber having excellent mechanical properties, particularly tensile strength and elongation, bending resistance, flexibility, and dimensional stability, and excellent translucency. Another object of the invention is to provide a method for manufacturing plastic optical fibers that reduces the variation in quality caused by non-uniformity during heat treatment and insufficient cooling during heat treatment, which are the technical problems in manufacturing plastic optical fibers. It is in.

[Means to solve the problem] The present invention has the following configuration.

(1) When a composite spun plastic optical fiber is continuously passed through a heating furnace for heat treatment, the plastic optical fiber is heat-treated by circulating heated gas in parallel or countercurrent through the passage in the heating furnace. A method for manufacturing a plastic optical fiber, characterized in that cooling is carried out by blowing cold air into the opening of the heating furnace outlet and discharging a gas mixture of the cold air and the heated gas leaking from the heating furnace.

(2) The method for producing a plastic optical fiber according to 1, wherein the heat treatment is non-contact heating stretching of the unstretched plastic optical fiber.

(3) The method for producing a plastic optical fiber according to item 1, wherein the heat treatment is a constant length heat treatment or a relaxation heat treatment at a relaxation rate of 3% or less for imparting dimensional stability to the drawn plastic optical fiber.

Hereinafter, the present invention will be explained in detail based on the drawings.

FIG. 1 is a side sectional view showing an example of a method of composite spinning, non-contact heating drawing, non-contact heat treatment, and winding of a plastic optical fiber used in the present invention.

In the figure, 1 is a plastic optical fiber, 2 is a composite spinneret, 3 is a cooling chimney, 14 is a take-up roller for the undrawn plastic optical fiber and a supply roller to the drawing zone, 5 is a block heater and a heating fluid. a non-contact heated drawing zone equipped with a circulation fan and a fluid heater; 9 is a drawing roller, i.e. a roller for drawing out the drawn plastic optical fiber from the drawing zone;
At the same time, a supply roller to the non-contact heat treatment zone, 1° is a non-contact heat treatment zone for imparting dimensional stability to the drawn plastic optical fiber, 14 is its heat treatment roller, and 15 is driven by a torque motor while traversing. This is a winder that winds plastic optical fiber onto a flanged bobbin attached to a spindle.

FIG. 2 is a schematic cross-sectional view of a conventional heating furnace for heat treatment.
16 is a heating gas supply port, and 17 is a heating gas outlet. In this case, since the plastic optical fiber 1 to be heat-treated advances in the direction of the arrow in the figure, it can be said that the heated gas flows in the countercurrent direction.

When the heated gas is flowed in the same direction as the traveling direction of the plastic optical fiber 1, 17 is the heating gas supply port;
6 is the heated gas outlet. Further, 18 is an inlet of the heating furnace, and 19 is an outlet of the heating furnace, and both are provided with a resistor (wind direction plate) 23 at the opening to allow air to flow into the heating furnace or heated gas from inside the heating furnace. Although efforts are being made to suppress the outflow of water as much as possible, it is insufficient and inevitably occurs. 20 is the outer wall of the heating furnace, 21
2 is a heat insulator and 22 is a block heater. When this heating furnace is used, the seal is insufficient, and the heated gas that accompanies the plastic optical fiber passing through the heating furnace has a considerable amount of heat, so the plastic optical fiber that exits the heating furnace is Due to slow cooling, deterioration of mechanical properties and variations in mechanical properties are likely to occur due to insufficient cooling. Further, the leaked heated gas causes deterioration of the working environment, which is also unfavorable from the viewpoint of energy saving and cost reduction.

FIG. 3 is a schematic side sectional view of the heating furnace for heat treatment according to the present invention, and in the figure, a cold air outlet 24 is provided at the opening of the heating furnace outlet 19, and the cold air is mixed with the heated gas leaking from the heating furnace. A non-contact sealing device consisting of an exhaust port 25 for discharging gas is provided to cool the plastic optical fiber 1. 26 is a partitioning material of the non-contact type sealing device, and 27 is a cell formed by the partitioning material 26. By the way, in the case of the heating furnace method shown in this figure, inlet 1
8 is provided with a resistor (wind direction plate) 23 which is a simple sealing device.

FIG. 4 is a schematic side sectional view showing another example of the heating furnace for heat treatment of the present invention, in which a non-contact type sealing device is also provided at the heating furnace inlet 1B. 27 is a cell formed by the partition material 26.

By providing non-contact sealing devices at both the inlet 18 and outlet 19 of the heating furnace, it is possible to save energy, reduce costs, and improve the working environment.

FIG. 5 is a schematic sectional view taken along the line z-z' in FIG. 4, and the upper part of the heating furnace can be opened upward as shown by the two-dot chain line. This is to make it easier to thread the multi-filament plastic optical fiber 1 into the heating furnace, and the non-contact thread sealing device is also divided into two halves, top and bottom, just like the heating furnace, so that it can be threaded easily. has been done.

FIG. 6 is an enlarged side sectional view of the non-contact sealing device, and FIG. 7 is a schematic sectional view taken along the line YY' in FIG. The partition member 26 is provided opposite to the path of the plastic optical fiber 1, and has a honeycomb-like hexagonal cell 27 formed by upper and lower panels 28 for the purpose of providing a rectifying effect. This opposing structure provides a sealing effect. Roughly,
Cold air blown from the supply port 24 (temperature: 15 to 25
°C2 humidity: 30-65%RH, wind speed 20, 2-20m
/S).

Next, the mixed gas of heated gas and cold air, which is accompanied by the plastic optical fiber 1 and leaks from the heating furnace, is discharged from the exhaust port 25, so that the heated gas which is accompanied by the plastic optical fiber is removed. This reduces the low and uneven mechanical properties caused by slow cooling after heating. As the ejector groove for the mixed gas of heated gas and cold air provided in the non-contact type sealing device shown in this figure, a mechanism for suctioning and ejecting the mixed gas by a sirocco fan or the like can be applied.

The present invention will be explained below using examples.

[Example] Sufficiently purified commercially available methyl methacrylate was subjected to continuous bulk radical polymerization and demonomerized to have a weight average molecular weight of 8.
5,000 and a residual monomer content of 0.17% by weight was obtained. This polymethyl methacrylate was used as a core component, and a commercially available fluorinated methacrylate was used as a sheath component, which was composite-spun to produce an undrawn plastic optical fiber.

An undrawn plastic optical fiber was subjected to non-contact heating, drawing, non-contact heat treatment and winding using the process shown in Fig. 1, which includes a non-contact heating and drawing device, a non-contact heat treatment device, and a winding device. When carrying out the stretching and non-contact heat treatment, the conventional heating furnace shown in FIG. 2 and the improved heating furnace apparatus of the present invention shown in FIGS. 4 and 5 are used. The test was conducted under the following conditions, and the results shown in the table were obtained.

In the present invention, it was confirmed that a plastic optical fiber having excellent mechanical properties can be obtained because it prevents poor mechanical properties and variations in values due to slow cooling caused by the accompanying heating gas leaking from the heating furnace.

[Effects of the Invention] The method for manufacturing a plastic optical fiber of the present invention solves the drawbacks of conventional heat treatment methods for plastic optical fibers, especially the structure of the heating furnace, eliminates leakage of heated gas from the heating furnace, and further, By bringing the plastic optical fiber into contact with the cold air at the exit of the heating furnace, a cooling effect can be imparted, which can improve mechanical properties and reduce variations in mechanical properties, while also saving energy and reducing costs. .

[Brief explanation of the drawing]

FIG. 1 is a schematic side sectional view showing an example of the composite spinning-non-contact heating drawing-non-contact heat treatment winding method of the plastic optical fiber used in the present invention, and FIG. 2 is a schematic side sectional view of a conventional heating furnace for heat treatment. 3 is a schematic side sectional view of the heating furnace for heat treatment according to the present invention, FIG. 4 is a schematic side sectional view showing another example of the heating furnace for heat treatment of the present invention, and FIG. z-
6 is an enlarged sectional view of the non-contact type sealing device, and FIG. 7 is a schematic sectional view taken along the Y-Y' arrow in FIG. 6. 1 Niblast optical fiber 2: Composite spinneret 3: Cooling chimney 4: Take-up roller for undrawn plastic optical fiber and supply roller to the drawing zone 5: Non-contact heating drawing zone 6: Fan for heated fluid 7: Heater for heated fluid 8: Non-contact sealing device 9: Stretching roller 10: Non-contact heat treatment zone 11: Heated fluid fan 12: Heated fluid heater 13: Non-contact sealing device 14: Heat treatment roller 15: Winder 16: Heated gas supply port 17: Outlet of heated gas 18: Furnace inlet 19: Furnace outlet 20: Furnace outer wall 21: Heat insulating material 22 Niblock heater 23: Resistance (wind direction plate) 24: Cold air outlet 25: Cold air and leaked heated gas Mixed gas outlet 26:
Partition material 27 of non-contact sealing device: Cell 28 formed by partition material: Panel

Claims (3)

[Claims] (1) When a composite spun plastic optical fiber is continuously passed through a heating furnace for heat treatment, the plastic optical fiber is heat-treated by circulating heated gas in parallel or countercurrent through the passage in the heating furnace. A method for manufacturing a plastic optical fiber, characterized in that cooling is carried out by blowing cold air into the opening of the heating furnace outlet and discharging a gas mixture of the cold air and the heated gas leaking from the heating furnace. (2) The method for manufacturing a plastic optical fiber according to claim 1, wherein the heat treatment is non-contact heating stretching of the unstretched plastic optical fiber. (3) The method for producing a plastic optical fiber according to claim 1, wherein the heat treatment is a fixed length heat treatment to impart dimensional stability to the drawn plastic optical fiber or a relaxation heat treatment at a relaxation rate of 3% or less.