JPH09296327A - Heat treatment of silicon carbide continuous filament - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the occurrence of yarn breakage by heat-treating a silicon carbide continuous filament in a state thereof covered with a heat-resistant spherical material so as to embed the silicon carbide continuous filament therein and smoothing the winding of the resultant treated fiber useful as a reinforcing material for a matrix such as a plastic or ceramics onto a bobbin. SOLUTION: A silicon carbide-based continuous filament is unwound from a bobbin, placed in a receiver for heat treatment and heat-resistant spherical materials such as beads made of graphite are then placed in the receiver so as to cover the silicon carbide-based continuous filament thereunder to carry out the heat treatment. The heat-resistant spherical materials enter interstices among the silicon carbide-based continuous filaments to prevent the continuous filaments from being entangled when winding thereof onto a bobbin.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for heat treating a silicon carbide-based continuous fiber.

[0002]

2. Description of the Related Art Silicon carbide fibers have excellent heat resistance and mechanical properties and are used as a reinforcing material for matrices such as plastics and ceramics. A method for further improving the above properties of the silicon carbide-based continuous fiber has also been proposed.

One example of the proposed method is the journal of the
Material Science Vol. 26, page 970 (1991)
Year)) and heat-treating silicon carbide fibers in a carbon monoxide atmosphere to improve the strength of the fibers. Another example of the proposed method is disclosed in Japanese Patent Laid-Open No. 6-
As disclosed in Japanese Patent No. 184828, a method of heat-treating a silicon carbide fiber in an atmosphere containing a volatile sintering aid such as boron to further improve the elastic modulus and heat resistance of the fiber. .

In the method proposed above, in order to heat-treat the silicon carbide fiber to improve the properties of the fiber, generally a long residence time, for example, 1 hour or more, preferably 3 hours or more is required. To be done. Several methods are conceivable as specific means for specifically operating the proposed method.

One of them is a method of rewinding continuous fibers from a bobbin, introducing them into a heat treatment apparatus, and winding the treated fibers around the bobbin. In this method, the treatment efficiency is significantly deteriorated due to the long residence time required for the heat treatment.

Another method is a method in which continuous fibers are unwound from a bobbin and heat-treated in the form of being wound into a heat resistant tube. In this case, the sizing agent attached to facilitate the unwinding of the continuous fiber is thermally decomposed during the heat treatment, and when wound on the bobbin after the heat treatment,
The treated fibers may become entangled with each other, making it difficult to wind them up and causing yarn breakage.

As another method, a method of arranging continuous fibers in a loop shape on a heat-resistant receiver and subjecting them to heat treatment can be considered. Also in this case, like the second method,
Due to the thermal decomposition of the sizing agent, when the treated fiber is wound from the receiver to the bobbin, the treated fiber is entangled with each other, which makes it difficult to wind the treated fiber and may cause yarn breakage.

[0008]

DISCLOSURE OF THE INVENTION According to the present invention, when heat-treating a silicon carbide-based continuous fiber to improve its characteristics, the continuous fiber after the heat-treatment is wound around a bobbin without the problem of yarn breakage. , Provide a method that can be done smoothly.

[0009]

According to the present invention, there is provided a method for heat treating a silicon carbide based continuous fiber, which comprises immersing the silicon carbide based continuous fiber in a heat resistant spherical material and heat treating the same.

Specific examples of the silicon carbide fiber used in the present invention include silicon carbide fibers composed of carbon-silicon-oxygen, for example, Nicalon (registered trademark), carbon-titanium and Alternatively, a silicon carbide fiber composed of zirconium-silicon-oxygen, for example, Tyranno fiber (registered trademark) manufactured by Ube Industries, Ltd. may be mentioned.

The above-mentioned silicon carbide-based fiber is formed by spinning an organosilicon polymer such as polycarbosilane, polytitanocarbosilane or polyzirconocarbosilane, and heating the spun fiber in an oxygen-containing gas atmosphere. Irradiation of the ionizing radiation fiber makes it infusible.
It can be prepared by heating to a temperature in the range of 00 to 1400 ° C.

The heat-resistant spherical substance used in the present invention is selected from those having heat resistance sufficient to maintain its shape at the heat treatment temperature in the present invention and not reacting with the silicon carbide fiber. There are no particular restrictions on the material, but typically, alumina, silicon carbide, ceramics such as silicon nitride, and graphite are mentioned. Among these, graphite has the smallest specific gravity of 1.6 to 1.8,
It can be preferably used because there is almost no possibility of damaging the heat-treated fiber when the silicon carbide-based continuous fiber is wound on a bobbin after being heat-treated.

The diameter of the heat resistant spherical material is preferably in the range of 0.1 to 2 mm. When the diameter is smaller than 0.1 mm, the heat-resistant spherical substance enters between the filaments constituting the silicon carbide based fiber, and it becomes difficult to remove it from the fiber after the heat treatment. On the other hand, if the diameter is larger than 2 mm, the weight of each heat-resistant spherical substance becomes large, which may damage the silicon carbide fibers.

In one aspect of the present invention, continuous silicon carbide fibers are unwound from a bobbin and placed in a receiver for heat treatment. At this time, it is preferable that one end of the continuous fiber is taken out of the receiver in order to easily wind the continuous fiber after the heat treatment onto the bobbin. . Then, the heat-resistant spherical substance is put into this receiver. The heat-resistant spherical substance enters the gap between the continuous fibers. The heat-resistant spherical substance is preferably filled in the receiver so that the continuous fibers are hidden during the heat treatment. The material of the receiver may be any as long as it retains its shape at the heat treatment temperature and does not react with the silicon carbide-based fibers, but is generally ceramics or graphite.

Then, the receiver filled with the silicon carbide-based continuous fibers and the heat-resistant spherical substance is placed in a heat treatment apparatus, for example, a heating furnace, and the silicon carbide-based continuous fibers are heat-treated. The atmosphere in the heat treatment device is appropriately selected depending on the purpose of the treatment.

When a carbon coating layer is formed mainly on the surface of the silicon carbide-based continuous fiber and the strength is improved, the atmosphere of the carbon monoxide-containing gas is preferably used. The heat treatment temperature is usually in the range of 1200 to 1500 ° C. The heating time is usually 3 to 5 hours.

In order to further improve the elastic modulus and heat resistance of the silicon carbide-based continuous fiber, it is preferable to use an atmosphere of a substance that is a sintering aid for silicon carbide and that volatilizes at the heat treatment temperature. Examples of this volatile sintering aid include compounds of iron, magnesium, lithium, beryllium, boron, aluminum, thorium, yttrium, lanthanum and cerium. Among these, boron compounds such as boron and boron oxide, and aluminum compounds such as aluminum and aluminum oxide are preferably used. The temperature at which the silicon carbide-based continuous fiber is heated in a volatile sintering aid atmosphere is usually 1500 to 2000 ° C.,
The heating time is usually 1 to 10 hours.

After the heat treatment is finished, the treated fiber is wound on a bobbin. As described above, if one end of the silicon carbide-based continuous fiber is taken out of the receiver prior to the heat treatment, it is easy to find the cue when winding the treated fiber around the bobbin.

In the present invention, when the treated fiber is wound on the bobbin, the treated fiber does not become entangled with each other and the occurrence of yarn breakage is suppressed due to the heat-resistant spherical substance put in the receiver. It

[0020]

【Example】

Example 1 Tyranno fiber (registered trademark) manufactured by Ube Industries (average filament diameter 11 μm, 1600 filaments / bundle, length 100)
0 m, tensile strength 330 kg / mm ² ), diameter 300 m
m, 50 mm deep into the graphite receiver while being unwound from the bobbin, and then dropped into a graphite bead with a diameter of 0.3 mm.
I put them in the receiver until the fibers were hidden. At that time, one end of the fiber was exposed outside the receiver.

Ten receivers containing fibers and beads made of graphite were stacked and placed in an electric furnace, and the atmosphere in the furnace was replaced with carbon monoxide. 0.5 m ^{3 of} carbon monoxide in the furnace
1400 at a heating rate of 400 ° C / hour while flowing for an hour
The temperature was raised to 0 ° C. and the temperature was maintained for 3 hours for heat treatment.

After the electric furnace was allowed to cool, the fibers were pulled out from the receiver and wound on a paper tube by utilizing one end of the fibers that had been taken out of the receiver. All 1000 m of fibers could be wound up without the fibers becoming entangled and the fibers not breaking. Tensile strength of heat treated fiber is 395k
g / mm ² .

Comparative Example 1 The same procedure as in Example 1 was repeated except that the graphite beads were not placed in the receiver. When trying to wind the heat-treated fiber around a paper tube, the fiber was entangled every several m, and the entanglement had to be unraveled each time.

Claims (5)

[Claims] 1. A heat treatment method for a silicon carbide-based continuous fiber, which comprises immersing the silicon carbide-based continuous fiber in a heat-resistant spherical material and heat-treating it. 2. The heat treatment method according to claim 1, wherein the heat treatment atmosphere comprises a carbon monoxide-containing gas. 3. The heat treatment method according to claim 1, wherein the heat treatment atmosphere comprises a gas containing a volatile silicon carbide sintering aid. 4. The heat treatment method according to claim 1, wherein the heat-resistant spherical substance is spherical graphite. 5. The heat treatment method according to claim 1, wherein the heat-resistant spherical substance has a diameter in the range of 0.1 to 2 mm.