JPS61191535A - Method and device for drawing glass rod - Google Patents

Abstract

PURPOSE:To obtain a small-diameter glass fiber having high strength and high quality without surface flaws by heating a glass rod to soften under the pressure and drawing the same in an inert gaseous atmosphere in a specific hermetic pipe. CONSTITUTION:The small-diameter resin-coated glass fiber is obtd. by heating the top end part of the glass rod of which the top end is hermetically grasped by means of an O-ring at the top end of a freely expandable and contractable hermetic pipe 3 and is thereby set in said pipe by a heating means 9 in the pipe 3 into which an inert gas such as Ar or N2 is introduced from a gas introducing pipe 11 through a pressure regulating valve 12 and is regulated to 1atm pressure or above, an upper metallic pipe 10, a furnace core pipe 6 and a lower hermetic pipe 4, drawing the rod to a glass fiber 1' and coating a resin thereon while preventing the intrusion of O2 by the resin. On the other hand, the rod 1 is lowered along with the progression of the drawing by shrinking the pipe 3 without moving relatively the gripped part of the rod with respect to the rod 1, then the drawing is continued.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method and apparatus for producing high-strength glass fibers. More specifically, the present invention relates to a method and apparatus for drawing a glass rod that can maintain a high heating softening temperature and produce high-strength glass fibers without surface flaws.

BACKGROUND OF THE INVENTION Glass fibers made from quartz glass are manufactured by heating and softening rod-shaped glass rods at a high temperature of 2000° C. or higher in a drawing furnace to form fibers, and then drawing the fibers out of the drawing furnace. At this time, the glass rod is heated to a predetermined temperature by a drawing furnace, that is, a heating furnace of a drawing device.

However, if the heating temperature is low, if there are flaws on the surface of the glass rod, the flaws will remain in an elongated form on the surface of the glass fiber after drawing, forming a glass fiber with low strength.

On the other hand, when the heating temperature is high, the flaws on the surface of the glass rod are melted and smoothed, so that no flaws caused by the surface flaws of the glass rod remain on the glass fiber after drawing.

However, when heated to high temperatures, the glass from the surface of the glass rod progresses to evaporation, and the reaction between the heating furnace material and the atmospheric gas in the heating furnace and the vaporized gas progresses, producing fine particles that adhere to the surface of the glass fiber. adhere to.

Furthermore, if foreign matter such as dust adheres to the surface of the glass fiber, its strength will be significantly reduced, so the glass fiber is coated with resin after drawing.

The sources of dust that adhere to bare glass fibers in the furnace include the fine particles generated by the reaction between the atmospheric gas and vaporized gas mentioned above, as well as the generation of fine particles due to oxidative wear and tear of the furnace heater and furnace core tube. . As a method for preventing the generation of this type of dust, for example, as described in JP-A-58-161939, metal carbide or the like is coated on the surface of the furnace core tube material of a drawing furnace to prevent oxidative consumption. It is proposed that

However, when carbon is used as the furnace core tube material, carbon has extremely high reactivity with oxygen, so even the presence of a small amount of oxygen in the heating furnace causes oxidative consumption and generates dust, causing the above-mentioned problems. Metal oxide coatings are also not a decisive factor in preventing oxidative wear when oxygen is present.

Therefore, it is important to create an oxygen-free atmosphere inside the heating furnace. As a means of creating an oxygen-free atmosphere inside a heating furnace, a method has been proposed in which the inside of the heating furnace is purged with an insoluble gas such as N2. However, since a heating furnace must have a glass loft insertion port and a glass fiber withdrawal port, it is unavoidable that several tens of ppm of oxygen will enter the drawing furnace from both ends of the opening. This was not a measure to create an oxygen-free atmosphere.

For this reason, in order to produce high-strength glass fibers, it was necessary in the prior art to select an appropriate temperature that is rather low.

For example, in the case of a quartz-based glass rod, it is 2000 to 23
Temperatures in the range of 00°C were employed.

Problems to be solved regarding hydrogen generation An object of the present invention is to provide a method and apparatus for manufacturing high-strength glass fiber by simple means.

More specifically, the present invention provides a method for producing high-strength glass fibers in which the reaction between the atmospheric gas in the heating furnace and the vaporized gas hardly progresses even when softened by heating at high temperatures, and therefore has no surface flaws. The purpose is to provide such equipment.

It goes without saying that the term "glass fiber" as used herein also includes optical fiber.

Means for Solving the Problems The present inventors have completed the present invention as a result of various experiments and studies in order to solve the above-mentioned problems of the prior art and achieve the purpose of the present invention. be.

According to the present invention, in the method for drawing a glass rod in which a glass rod is softened by heating in a heating furnace and stretched into a fiber shape to obtain a thin glass fiber, the heating softening is performed at a pressure exceeding 1 atm, preferably 1.5 atm. A method for drawing a glass rod is provided, which is characterized in that the drawing method is carried out under a pressure equal to or higher than atmospheric pressure.

According to a preferred embodiment of the invention, the pressurized gas is N2He5
It is an inert gas such as Ar.

Furthermore, according to the present invention, there is provided a glass rod drawing apparatus in which the inside of the heating furnace is configured to be airtight and the pressure inside the furnace can be adjusted.

That is, according to the present invention, the airtight leakage of the glass rod insertion port at the upper end of the heating furnace of the glass rod drawing furnace, that is, the heating furnace of the drawing device, can be solved by providing a sealed tube in the upper part of the heating furnace. This problem can be solved by, for example, providing an O-ring or the like at the upper end to grip the upper part of the glass rod while completely sealing it. Preferably, this upper closed tube is telescopic. Conventionally, when a glass rod is tightly held at the top of a heating furnace in contact with an external pipe connected to the heating furnace, as the glass rod descends as drawing progresses, the tightly held and fixed part of the glass rod It was not possible to completely seal the glass rod with an external pipe because it moved while scratching the surface, causing scratches on the surface of the glass rod.

In the present invention, by performing high-temperature heating and softening, and by using a telescopic sealed tube, it has become possible to completely seal the external pipe. That is, even if a flaw occurs on the glass rod, the surface flaw disappears due to high temperature heating and does not become a surface flaw in the glass fiber. Also,
By using a telescopic sealed tube, contact scratches only occur in the non-effective part of the upper part of the glass rod that is not drawn, and since the upper sealed pipe is telescopic, the contact part descends as the glass rod descends. Therefore, new unnecessary scratches will not be generated. On the other hand, airtight leakage at the glass fiber draw-out port below the heating furnace of the drawing device can be solved by connecting the lower part of the heating furnace to the resin coating means, such as a coating die, using another sealed pipe.

Furthermore, it is necessary to avoid contact of bare glass fibers with external solids to prevent strength deterioration of the glass fibers. To this end, conventionally, the diameter of the glass fiber outlet was made much larger than the diameter of the glass fiber, and the purge gas was flowed from the inside of the drawing furnace to the outside to prevent oxygen from entering the drawing furnace. Although it was not possible to completely prevent oxygen from entering from the mouth, in the present invention, the space between the glass fibers and the glass fiber outlet is sealed with a resin for covering the glass fibers, so it is completely possible to prevent the ingress of oxygen from the outside. It is possible to prevent oxygen from entering the drawing furnace, and the strength of the glass fibers does not deteriorate due to contact between the drawing port and the glass fibers.

A wire drawing apparatus having such a structure is further provided with a gas, preferably an inert gas introduction pipe, and a pressure regulating valve to regulate the pressure inside the heating furnace.

[January] The invention aims to reduce the evaporation of the glass rod at high temperatures by increasing the pressure inside the heating furnace, thereby preventing the generation of reaction product particles and preventing a decrease in strength due to particle adhesion to the fiber surface. On the other hand, the present invention provides a method for producing high-strength glass fiber by smoothing surface flaws on a glass rod by high-temperature heating.

That is, evaporation of the glass rod occurs because the saturated vapor pressure of the glass rod at the heating temperature is higher than the pressure of the drawing atmosphere, but in the present invention, the pressure of the drawing atmosphere is defined as the vapor pressure of the glass rod at the drawing temperature. By holding the glass rod higher, evaporation of the glass rod is prevented1, and as a result, the generation of reaction product particles between the vaporized glass and atmospheric substances is suppressed, making it possible to manufacture high-strength glass fibers.

Furthermore, in the glass rod drawing device of the present invention,
After the glass rod in the wire drawing device is drawn, it can be a completely closed system until it is coated with resin. Therefore, the atmosphere inside the drawing apparatus can be made into a highly oxygen-free atmosphere.

Therefore, even if the furnace core tube material is a substance that is easily oxidized, such as carbon, no dust is generated in the drawing device, especially in the heating furnace, due to oxidative consumption. In addition, there is no risk of foreign matter such as dust entering the closed system inside the drawing device from the atmosphere outside the drawing device, so even if the furnace core tube material is easily oxidized, dust due to oxidation will not be present. There is no fear of this occurring, and the effects of the present invention are significant. Therefore, the present invention is not limited to a furnace core tube made of a specific material. Of course, in the glass rod drawing apparatus of the present invention, the furnace core tube material may be non-oxidizing.

According to the present invention, glass fibers drawn from glass rods are coated with resin while maintaining a clean and smooth surface, and as a result, high quality glass fibers can be manufactured.

Embodiment FIG. 1 attached herewith is a schematic sectional view of a glass rod drawing apparatus according to an embodiment of the present invention.

As shown in the figure, the glass rod drawing device consists of a glass rod 1 supported vertically, a heating furnace 2 disposed concentrically with the glass rod 1, and a retractable closed tube 3 connected above the heating furnace 2. , a sealed tube 4 connected below the heating furnace 2, and a resin-coated die 5 disposed below the sealed tube 4.

The heating furnace 2 is arranged concentrically with the glass rod l, and includes a furnace core tube 6 made of, for example, graphite, a sealing cover 7 made of metal, for example, that surrounds the furnace core tube 6, and a furnace core tube 6 inside the sealing cover 7. and a heating means 9 arranged so as to surround the glass rod 1 via the heating means 9. The heating means 9 may be resistance heating or induction heating. Needless to say, the furnace core tube 6 and the sealing cover 7 are connected airtightly, and the furnace core tube 6 is also airtightly connected to the metal vibrator 1O above it and the sealing tube 4 below.

To give an example of the dimensions of the device, the furnace core tube 6 has an inner diameter of 80 mm.
φ and length 300n+n+. Also, the lower sealed tube 4
is made of quartz and has an inner diameter of 80 mmφ and a length of 100 mm.

According to the invention, above the heating furnace 2, i.e. the pipe 10
A preferably telescopic closed tube 3 is connected in an airtight manner. The telescopic sealed tube 3 may have a bellows structure as shown in the figure, or may be a pre-inserted type. Such an airtight grip can be easily achieved by using an O-ring, for example.

The telescopic sealed tube 3 has an inner diameter of 80 mm, for example, and is telescopic within a length range of 0.3 to 1 m.

Further, according to the present invention, a resin coating die 5 is provided in airtight connection with the lower sealed tube 4.

This resin-coating die is arranged with the glass fiber 1'' inlet facing the inside of the sealed tube 4 and the outlet opening facing the outside.

Furthermore, according to the invention, a gas inlet pipe 11 is provided, in which N2,
An inert gas such as Ar5He is introduced into the heating furnace. The flow rate of the inert gas is adjusted by the pressure regulating valve 12, and the pressure within the heating furnace is adjusted to a desired value.

Next, the operation of the glass rod drawing apparatus shown in FIG. 1 will be explained.

The glass rod 1 is set so that its upper end is hermetically held by the upper end of the telescopic airtight tube 3. The interiors of the expandable and retractable airtight tube 3, furnace core tube 6, and lower airtight tube 4 are filled with inert gas introduced from the gas introduction tube 11, and maintained in an oxygen-free state. The pressure in the heating furnace is adjusted by the pressure regulating valve 12 to a pressure higher than the saturated vapor pressure of the glass rod at the heating temperature, for example, a pressure exceeding 1 atmosphere, preferably 1.5 atmospheres or higher.

On the other hand, a glass fiber 1' is drawn from the glass rod 1 whose tip part is heated by the heating means 9, and the glass fiber 1' is coated with resin by the resin coating die 5 in an oxygen-free state without dust. .

Therefore, the glass fiber 1' is maintained in an oxygen-free state without coming into contact with foreign matter until it is coated with resin in the drawing device, so that its strength is extremely high.

Furthermore, as the drawing progresses, the glass rod 1 descends, and in synchronization with this descent, the telescopic sealed tube 3 contracts, so that the upper end of the telescopic sealed tube 3 grips the glass rod. There is no relative movement with respect to the rod 1, and there is no fear of scratches on the surface of the glass rod.

Production Example A glass rod made of pure silica subjected to the pretreatment shown in Table 1 was made into glass fiber with a diameter of 125 μmφ using the drawing device shown in FIG. Coated with silicone resin using a die to make a diameter of 40 mm.
A resin-coated glass fiber with a diameter of 0 μm was used.

The atmosphere in the heating furnace was set to He atmosphere, and the pressure in the furnace was measured, and is shown in Table 1 together with the heating temperature.

The four types of glass fibers obtained in Table 1 were each subjected to a tensile test using a sample length of 10 m, a tensile speed of 1 m/min, and 20 samples. The results are shown in FIG. In FIG. 2, the circle mark indicates the measurement result of A1, the mark indicates the measurement result of 810, the mark indicates the measurement result of C1, and the mark indicates the measurement result of D.

As is clear from the results shown in Figure 2, the glass fiber D produced at a furnace pressure of 2 atmospheres contains low-strength parts, even though the surface treatment of the glass rod was simply chemical etching. It shows no high strength.

Effects of the Invention The present invention maintains the inside of the heating furnace of the glass rod drawing device at high pressure, that is, a pressure exceeding 1 atm, preferably at least 1.5 atm, so that glass rods can be drawn at high temperatures. It reduces evaporation and prevents the generation of reaction product particles, making it possible to draw glass rods at high temperatures.
The present invention provides a method for producing high-strength glass fiber by smoothing surface flaws on a glass rod by high-temperature heating.

Furthermore, the glass rod drawing device of the present invention includes:
It is characterized by having a completely closed system between the time the glass rod in the drawing device is drawn and before it is coated with resin, and the inside of the heating furnace being under high pressure.

According to the present invention, it is possible to manufacture high-strength and high-quality glass fibers.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view of a glass rod drawing apparatus according to an embodiment of the present invention. FIG. 2 is a graph showing the results of a tensile test of glass fibers in this production example. (Main reference numbers) 1...Glass rod, 1゛...Glass fiber, 2...
・Heating furnace, 3. Shrinkable sealed tube, 4. Lower sealed tube, 5. Resin coating die, 6. Furnace core tube, 11
...Gas inlet pipe 12...Pressure adjustment valve, Patent applicant Sumitomo Electric Industries, Ltd. Agent Masahiko Arai Figure 1 12: Pressure adjustment rod 1

Claims (6)

[Claims] (1) A glass rod drawing method in which a glass rod is softened by heating in a heating furnace and stretched into a fiber shape to obtain a thin glass fiber, characterized in that the heating softening is performed under a pressure exceeding 1 atmosphere. How to draw a glass rod. (2) The method for drawing a glass rod according to claim 1, wherein the pressurized gas is an inert gas. (3) The method for drawing a glass rod according to claim 1 or 2, wherein the pressurizing pressure is 1.5 atmospheres or more. (4) In a glass rod drawing device that heats and softens a glass rod in a heating furnace and stretches it into a fiber shape to make glass fiber, a sealed tube is airtightly connected to the upper part of the heating furnace, and the heating furnace The upper end of the hermetically sealed tube at the top of the heating furnace is configured to hermetically surround the glass rod, and a resin coating means is hermetically provided at the lower end opening of the heating furnace via the hermetically sealed tube. A glass rod drawing device characterized in that an inert gas introduction pipe and an in-furnace pressure regulating valve are provided in the upper part or the lower sealed pipe. (5) The glass rod drawing apparatus according to claim 4, wherein the sealed tube airtightly connected to the upper part of the heating furnace is expandable and retractable. (6) The glass rod drawing device according to claim 5, wherein the glass rod is tightly held by the upper end of the telescopic closed tube using an O-ring.