JPS61158838A - Production of quartz hollow fiber - Google Patents

Abstract

PURPOSE:To mold stably hollow optical fiber having improved fiber hollow molding properties, and especially large diameter and a small thickness, by making the pressure in a spinning furnace lower than the inner pressure of quartz tube, and carrying out spinning. CONSTITUTION:The quartz tube 1 is gradually sent to the spinning furnace 2 kept at about 1,800-2,000, and wound by the winder 5 to give the hollow fiber 4. In the operation, the outer diameter of the fiber is controlled by regulating the winding speed of the winder 5 depending upon the measured result of the instrument 6 for outer diameter of the fiber. The inner diameter of the fiber is controlled by driving the reduced pressure regulator 9 depending upon the measured result of the instrument 7 for inner diameter of the fiber and regulating the degree of reduced pressure in the spinning furnace 2. The prepared hollow fiber 4 is provided with a resin, metal, etc., as a reinforcing layer by the coater 8. Since spinning is carried out by reducing the pressure in the furnace 2 to a given degree of reduced pressure lower than the pressure (atmospheric pressure) in the quartz tube 1, the hollow fiber having improved fiber hollow molding properties, especially large diameter and small thickness can be stably molded.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention provides a method for producing quartz (silica) hollow fiber;
In particular, the present invention relates to a manufacturing method useful for manufacturing large-diameter, thin-walled quartz hollow fibers.

(Conventional technology) Conventionally, general quartz hollow fibers have been manufactured by melting and spinning a quartz tube in an open spinning furnace (the pressure inside and outside the quartz tube is the same as atmospheric pressure).

<Problems to be Solved by the Invention> In the above method, the inner diameter of the fiber is controlled mainly by controlling the furnace temperature, but the response is poor and optimal control is extremely difficult.

Therefore, in recent years, when spinning in a spinning furnace, attempts have been made to control the inner diameter by increasing the internal pressure of the quartz tubes above the furnace pressure (tube pressure control method), but the inner diameter between the quartz tubes is small, Since the internal capacity is limited, the flow rate of the supplied gas is extremely small, and the current situation is that sufficient pressure control cannot be obtained.

Means for Solving the Problems> The present invention has been made in view of the difficulty in controlling the inner diameter in the above-mentioned conventional technology, and its characteristic configuration is basically that Pressure is the pressure inside the quartz tube (atmospheric pressure)
The point is that the spinning process is performed at a lower pressure. And preferably,
The degree of vacuum in the spinning furnace is determined by measuring the inner diameter or wall thickness of the hollow fiber, and adjusting the degree of pressure reduction in the spinning furnace from 70 to 40 depending on the deviation from the set value.
It is controlled within a range of 0 mmHg.

(Function) By spinning in a reduced furnace pressure (on the outside of the quartz tube), the internal pressure (atmospheric pressure) is relatively higher than the external pressure in the quartz tube, so it has good blow formability, especially for large diameter and thin walled quartz tubes. Hollow fiber molding becomes easy, and depressurization control at this time can be easily performed by simply adjusting the degree of vacuum in a furnace with sufficient capacity.

<Example> FIG. 1 schematically shows an apparatus system used to carry out the present invention.

In the figure, 1 is a quartz tube of the fiber base material, 2 is an airtight spinning furnace, 3 is a heating heater installed in the furnace 2, 4 is a hollow fiber after spinning, and 5 is a winding of the fiber 4. 6 is a fiber outer diameter measuring device installed in the middle of the fiber traveling on the spinning exit side; 7 is a fiber inner diameter measuring device installed near the outer diameter measuring device 6; 8 is a device for coating the outside of the fiber 4 with a reinforcing layer; The coating device 9 is connected to the spinning furnace 2 and is a pressure reduction controller (for example, a vacuum pump, etc.) for controlling the degree of pressure reduction in the furnace 2.

In this device system, the winding device 5 is linked with a fiber outer diameter measuring device 6, and the winding speed is controlled based on the measurement results of the fiber outer diameter measuring device 6. Further, the pressure reduction controller 9 is a fiber inner diameter measuring device 7.
In conjunction with this, the degree of vacuum in the spinning furnace 2 is controlled based on the measurement results of the fiber inner diameter measuring device 7.

Next, the fiber manufacturing method of the present invention will be described using this apparatus system.

First, the quartz tube 1 is gradually fed into a spinning furnace 2 kept at about 1800 to 2000°C, and wound into a hollow fiber 4 by a winding device 5. At this time, the fiber outer diameter is controlled by the measurement results of the fiber outer diameter measuring device 6.
This is done by adjusting the winding speed of the winding device 5. Also, on the other hand,
The fiber inner diameter is controlled by driving the pressure reduction controller 9 and adjusting the degree of pressure reduction in the spinning furnace 2 based on the measurement result of the fiber inner diameter measuring device 7.

The hollow fiber 4 thus obtained is coated with a reinforcing layer such as resin or metal by a coating device 8 while the fiber is traveling.

In this manufacturing method, the spinning furnace 2 is
When heated at 00℃, the maximum temperature of quartz tube 1 is 1600℃.
The inner diameter/outer diameter ratio of the spinning fiber decreases due to the collapse phenomenon, and the rate of decrease increases as the temperature increases. On the other hand, the viscosity of quartz changes greatly within this temperature range, and the higher the temperature becomes, the lower the viscosity becomes.
Be sensitive to changes in pressure. Furthermore, although the collapse phenomenon can be suppressed at low temperatures, the tension during spinning increases, making stable spinning difficult.

For these reasons, the optimal holding temperature of the spinning furnace 2 is preferably about 1,800 to 2,000°C, as described above, and at this temperature, the large-diameter, thin-walled hollow fiber 4 can be formed while suppressing the collapse phenomenon most effectively. To obtain fused quartz tube 1
The pressure difference between the inside and outside of the spinning furnace 2, that is, the degree of vacuum inside the spinning furnace 2, is set to 70 to 40.
It is best to keep it within the range of 0mmHg. If the temperature is less than 7QmmHg, even at 1600℃, which is the lower limit for spinning, the collapse phenomenon will prevail and the inside of the tube will collapse.
When it exceeds 00mmHg, in the entire spinnable range,
This is because rupture occurs due to the pressure difference at the spinning start end.

When we conducted an actual manufacturing test, we found that the temperature inside the furnace was 1800℃.
In order to set the fiber inner diameter to 250 to 300 μmφ, the degree of vacuum in the furnace is preferably in the range of 70 to 15 QmmHg, and when the temperature in the furnace is 2000°C, the degree of vacuum in the furnace is preferably in the range of 200 to 400 mmHg. It was true.

<Effects of the Invention> According to the present invention, during spinning, the pressure inside the furnace is reduced to a predetermined degree of pressure reduction compared to the pressure inside the quartz tube (atmospheric pressure), so that the fiber has good hollow formability, and especially Large-diameter, thin-walled hollow fibers can be stably molded. This is ideal for, for example, manufacturing quartz columns for gas chromatograph devices. Also, the pressure reduction control at this time has the advantage that it can be performed extremely economically, as it only requires adjusting the gas flow rate (degree of vacuum) in a furnace having sufficient capacity, compared to the conventional in-pipe pressure control method.

[Brief explanation of the drawing]

FIG. 1 is a schematic vertical sectional view showing an example of an apparatus system for carrying out the method of the present invention. In the figure, 1...quartz tube, 2...spinning furnace, 4...hollow fiber, 5...winding device, 6...fiber outer diameter measuring device, 7... fiber inner diameter measuring device , 8... coating device, 9... pressure reduction controller. Figure 1

Claims (2)

[Claims] (1) In the method of heating and melting a quartz tube in a spinning furnace and drawing it to produce a hollow fiber, the pressure inside the spinning furnace is reduced from the pressure inside the quartz tube (atmospheric pressure). 1. A method for producing quartz hollow fiber, which comprises spinning the quartz hollow fiber. (2) The degree of vacuum in the spinning furnace is determined by measuring the inner diameter or wall thickness of the hollow fiber, and adjusting the degree of vacuum in the spinning furnace to 7 depending on the deviation from the set value.
2. The method for producing a quartz hollow fiber according to claim 1, wherein the quartz hollow fiber is controlled within a range of 0 to 400 mmHg.