JPH0830289B2 - Method for producing refractory inorganic oxide fiber - Google Patents

Description

The present invention relates to a method for producing a refractory inorganic oxide fiber. Since inorganic oxide fibers such as alumina fibers, silica-alumina fibers, and zirconia fibers have excellent heat resistance, and also have high strength and high elastic modulus, they are used as refractory heat insulating materials or reinforcing fibers in metals, plastics, and ceramics. It is used for composite materials with etc.

[Conventional technology]

As one of the methods for producing such a refractory inorganic oxide fiber, the raw material of the inorganic oxide fiber is dissolved or suspended in water together with the water-soluble organic polymer, and the obtained solution has a viscosity suitable for fiberization. A method for producing an inorganic oxide fiber is known, in which the inorganic oxide fiber is adjusted, brought into contact with an air stream flowing at a high speed to be fiberized, dried and then fired. For example,
55-36726 describes a method of spinning a spinning dope by pushing it into an air stream having a relative humidity of 80% or more. Further, in JP-A-55-20234, in a method of spinning a spinning dope by a centrifugal method, droplets of the spinning dope are scattered on a rotating disc, and a large number of nozzles are arranged around this disc.
A method is disclosed in which heated compressed air is ejected from the nozzle, and thereby a droplet of the spinning dope is drawn to form a fiber. The compressed air used in this method is said to be most suitable for fiberization under a fluid condition of a gauge pressure of 6 to 7 kg / cm ² and a temperature of 100 to 180 ° C.

[Problems to be solved by the invention]

In such a method for producing an inorganic fiber, not only the composition and preparation method of the spinning dope but also the spinning conditions have a great influence on the physical properties of the fiber. That is, in such a spinning method, since the surface area of the fiber is rapidly increased during fiber formation, if the amount of water in the atmosphere is too small or the temperature is too high, rapid evaporation of water from the fiber surface may occur. The fibers may be insufficiently drawn and fibers having a diameter larger than the desired diameter may be formed. On the other hand, even if the amount of water in the atmosphere is too large, rapid evaporation of water from the fibers does not occur, and the shape of the fiber once formed collapses, forming a so-called shot.

[Means for solving problems]

In order to solve the above-mentioned problems, the present inventors have conducted intensive studies on spinning conditions, and as a result, by adjusting the temperature and humidity of the atmosphere, the amount of shot is reduced, and an inorganic oxide fiber having high strength is produced. I found a possible method. That is, in the present invention, the refractory inorganic oxide fiber spinning stock solution is contacted with a high-speed air stream to be fiberized and dried, and the obtained fiber is collected by a fiber collector and finally fired. In the method for producing a refractory inorganic oxide fiber by that the temperature of the air flow in the vicinity where the spinning dope starts contact with the air flow is 1 to 20 ° C., and the temperature of the air flow near the fiber collector. The present invention is directed to a process for producing a refractory inorganic oxide fiber, which comprises spinning under conditions of 25 ° C. or higher and relative humidity of 30% or lower. Hereinafter, the present invention will be described in detail.

The spinning dope prepared by the method of the present invention contains various metal compounds capable of forming inorganic oxide fibers and a water-soluble organic polymer. As a metal compound, as is well known, those which can form a water-soluble or colloidal solution are used.
Examples of such compounds include chlorides of metals such as aluminum, zirconium, silicon, magnesium, thorium, yttrium, calcium, and chromium, inorganic acid salts such as sulfates and nitrates, organic acid salts such as acetate, and hydroxides. Examples thereof include aluminum oxychloride, basic aluminum acetate, zirconium oxychloride, and basic zirconium acetate. These can be used alone or in combination.

Examples of the water-soluble organic polymer include polyvinyl alcohol, polyethylene glycol, polyethylene oxide, polyacrylamide, starch, acetic acid starch, hydroxyethyl starch, methyl cellulose, ethyl cellulose, hydroxyethyl cellulose, carboxymethyl cellulose and the like.

The spinning dope is appropriately prepared according to the properties of these fiber raw materials and the intended fiber. Many methods for preparing a spinning dope are known. For example, in the case of producing alumina fibers, a silicon compound such as silica sol, tetraethyl silicate or a water-soluble siloxane derivative is added to an aluminum oxychloride solution, and a water-soluble solution such as polyvinyl alcohol is further added. Organic polymer is added and concentrated to the desired solids content. The silicon compound and the water-soluble organic polymer may be added during or after the concentration. In the case of alumina fibers, the proportions of aluminum and silicon in the spinning dope are converted to Al ₂ O ₃ and SiO ₂ , respectively, and A
It is preferable that the proportion of l ₂ O ₃ is in the range of 65 to 98% by weight, particularly 70 to 98% by weight.

The stock solution for spinning is adjusted to have a viscosity suitable for spinning, usually 1 to 1000 poises. Spinning is performed by supplying the spinning dope to an air stream flowing at high speed through pores having a diameter of 0.1 to 5 mm, or by utilizing the centrifugal force of a rotating body that rotates at high speed. In the case of the former, for example, air is blown from the periphery of the spinning dope supply nozzle and the spinning dope is supplied into this air stream to perform spinning, and an appropriate number of spinning dope feed nozzles are arranged around the air blowing nozzle. There is a method of spinning by spinning, or a method of arranging an opening of a spinning stock solution supply nozzle in a high-speed air stream and drawing the spinning stock solution by an air stream for spinning.
In the latter case, the spinning dope is supplied from the central part of the rotating body, and the spinning dope is produced by blowing out an air flow from an air outlet provided annularly near the periphery of the rotating body or the periphery of the rotating body. Fiberize. The flow velocity of the air flow is usually appropriately selected between 50 and 500 m / sec.

According to the study by the present inventors, when spinning, first,
Under conditions where evaporation of water and decomposition of the spinning dope are suppressed, it is important that a sufficiently stretched fiber is formed from the spinning dope and then this fiber is rapidly dried.
That is, it is important to change the atmosphere from a state in which evaporation of water is suppressed to a state in which evaporation of water is promoted in the process in which the spinning dope is changed into fibers and reaches the fiber collector. For example, if the temperature of the atmosphere is too high at the stage where a sufficiently stretched fiber should be formed from the spinning dope,
Due to rapid evaporation of water and other reasons, fully stretched fibers are not formed. And the formed fiber has defects,
The finally obtained inorganic oxide fiber becomes brittle. On the other hand, when fibers are formed from the spinning dope in a low temperature or high humidity atmosphere to suppress evaporation, if the same atmosphere continues after the fiber formation, the fibers may adhere to each other or the liquid may be recovered due to elastic recovery. Easily drips to form shots. This phenomenon occurs even while the fibers are suspended in the air flow,
Especially when the fibers are collected on the fiber collector, they are likely to occur.

In the present invention, the temperature around the spinning dope to start contact with the air flow is 1 to 20 ° C., preferably 5 to 15 ° C., and the temperature of the air flow near the fiber collector is 25 ° C. or higher, preferably 30.
Spinning is performed under the condition that the temperature is ℃ or more and the relative humidity is 30% or less. In addition, considering energy efficiency and working environment,
The temperature of the air flow near the fiber collector should be up to 100 ° C.

In the present invention, as described above, the use of low-temperature air suppresses the evaporation of water from the spinning dope during the fiber formation process. However, even in this case, it is preferable to use air having a slight humidity. Air having a relative humidity of 10% or more is usually used. For example, temperature 10 ℃, relative humidity 90%
When 2 kg / cm ² G of compressed air is blown out from the nozzle under atmospheric pressure, a high-speed air stream having a temperature of about 10 ° C. and a relative humidity of about 30% is formed.

The temperature and relative humidity of the air flow near the fiber collector are controlled by adding air having a temperature of 30 ° C. or higher and a relative humidity of 30% or lower to the air flow containing fibers formed from the spinning dope. At this time, the temperature of the air to be added, the relative humidity, and the amount to be added are appropriately selected depending on the temperature of the air used for fiberizing the spinning dope, the relative humidity, and the temperature and the relative humidity required for the air flow near the fiber collector. . In the fiber production by the spinning method of the present invention, the stock solution must first be drawn into fibers having a desired diameter, and thereafter, the drawn fibers must maintain their shape and be sufficiently dried. In the present invention, when controlling the atmosphere, the temperature of the air flow and the relative humidity are respectively in the vicinity and after the start of the drying of the drawn fiber.
Adjust the temperature and relative humidity of the air flow so that the temperature is 30 ° C or higher and 30% or lower. Normally, the temperature of the air flow near the fiber collector is adjusted by adding an air flow with a temperature of 30 ° C or higher and a relative humidity of 30% or lower at a position 10 to 50 cm from the point where the spinning dope starts contacting with the air flow. Control so that the relative humidity is 25% or higher and the relative humidity is 30% or lower. The atmosphere control method will be described in more detail with reference to FIG. 1 showing an example of an embodiment of the present invention. In FIG. 1, the stock solution for spinning 1 is extruded toward a fiber collection chamber 4 through a spinning nozzle 3 arranged in a spinning chamber 2. Air that is compressed by an air compressor 5 near the spinning nozzle 3 and is adjusted to have a temperature of 1 to 20 ° C. and a relative humidity of 10% or more through a device 6 that adjusts the temperature, water content, and pressure in some cases. Is flowing at high speed. The extruded spinning dope is introduced into the fiber collection chamber 4 equipped with the air flow and the fiber collector 9 having the wind tunnel 7 and the screen 8 for collecting fibers. At this time, air having a temperature of 30 ° C. or higher and a relative humidity of 30% or lower is discharged from the warm air discharger 10 provided in front of the wind tunnel 7, and the temperature of the air flow near the fiber collection screen 8 is 25 ° C. or higher. The temperature and relative humidity of the airflow are controlled so that the relative humidity is 30% or less. As the air discharged from the warm air discharger 10, separately adjusted air is supplied at the start of spinning, but thereafter, after collecting the fibers, a part of the air after separating the fibers is heated by the warm air generator. It is preferable from the viewpoint of utilization of air to heat and circulate through 11. Excess airflow is exhausted through exhaust port 12. Also, if necessary,
The relative humidity of the air can be further adjusted by the dehumidifier 13 provided in the spinning chamber 2. However, in the method of the present invention, the temperature of the air flowing in the vicinity of the spinning nozzle is low, and therefore the absolute humidity thereof is low. Therefore, by adjusting the ratio of this air amount to the circulating air amount and the temperature of the circulating air, the circulation The temperature and humidity of the air near the fiber collector can be maintained at predetermined values without dehumidifying the air or the spinning chamber. Even when spinning is performed without providing a fiber collection chamber, the warm air discharger is 10 to 50 cm from the spinning nozzle.
It is preferable to arrange them at distant positions.

The fibers collected by the fiber collector are then
It is preferably fired at a temperature of 1000 to 1300 ° C. If the firing temperature is less than 500 ° C, only brittle fibers with low strength can be obtained. On the other hand, even if the firing temperature exceeds 1400 ° C., the grain growth of the crystal of the fiber proceeds and the strength of the fiber decreases. If desired, the fibers may be subjected to needling or other processing prior to firing.

Next, the present invention will be described in more detail with reference to Examples.
The present invention is not limited to the following examples unless it exceeds the gist.

Examples 1 to 3 Aqueous aluminum oxychloride solution (aluminum content
75 g / l, Al / Cl (atomic ratio) = 1.8) 1, 20% silica sol solution 275 g and 5% polyvinyl alcohol aqueous solution 315 g were added and mixed. This mixed solution was concentrated under reduced pressure at 50 ° C. to prepare a spinning dope having a viscosity of 40 poise and an alumina-silica content of 30 wt.%, Which was extruded from a spinning nozzle into a high-speed air stream for spinning. Use air whose temperature, pressure and humidity are adjusted as shown in Table-1 as the air flow near the spinning nozzle so that the temperature of the air flow near the fiber collector is 30 ° C and the relative humidity is 20%. , At a position about 30 cm away from the spinning nozzle outlet, 60 ° C,
Hot air with a relative humidity of 3.6% was introduced in parallel to the high-speed air stream flowing near the spinning nozzle. Install a fiber collector screen at a position about 4 m away from the spinning nozzle to collect the collected fibers.
It was baked at 1260 ° C. for 1 hour. Obtained fiber diameter, shot rate, bulk tensile strength (tensile strength of polymer of fiber, spacing
40 mm, ρ = 0.1 g / cm ³ ) is shown in Table-1.

Comparative Examples 1 to 3 In Examples 1 to 3, the same as the method of Examples 1 to 3 except that air adjusted to the temperature, pressure and humidity shown in Table 1 was used as the air flow flowing in the vicinity of the spinning nozzle. To produce fibers. The results are shown in Table 1.

Comparative Examples 4 to 6 Fibers were prepared in the same manner as in Examples 1 to 3 except that the temperature of the air flow near the fiber collector was 20 ° C. and the relative humidity was 40%. Was manufactured. The results are shown in Table 1.

[Advantages of the Invention] According to the present invention, it is possible to manufacture a fiber having a high strength and a small shot rate.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram showing an example of an embodiment of the present invention. 1 ... Spinning stock solution, 2 ... Spinning chamber 3 ... Spinning nozzle, 9 ... Fiber collector 10 ... Warm air discharger

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-48-14824 (JP, A) JP-A-50-18727 (JP, A) JP-A-55-20239 (JP, A) JP-A-55- 30467 (JP, A) JP47-37215 (JP, B1) JP50-502224 (JP, A)

Claims (3)

[Claims] 1. A refractory inorganic oxide fiber spinning stock solution is contacted with a high-speed air stream to be fiberized and dried, and the obtained fiber is collected by a fiber collector and finally calcined. In the method for producing a refractory inorganic oxide fiber according to, the temperature of the air flow in the vicinity where the spinning dope starts contact with the air flow is 1 to 20 ° C., and the temperature of the air flow near the fiber collector is A method for producing a refractory inorganic oxide fiber, which comprises spinning under conditions of 25 ° C or higher and relative humidity of 30% or lower. 2. The temperature of the air stream near the fiber collector is adjusted to 25 by adding air having a temperature of 30 ° C. or more and a relative humidity of 30% or less to the air stream containing fibers formed from the spinning dope.
Claim 1 in which the relative humidity is 30% or less and ℃ or more
The method described in the section. 3. A part of the air stream after the fiber collection is adjusted to a temperature of 30 ° C. or higher and a relative humidity of 30% or less and added to an air stream containing fibers formed from a spinning dope to collect the fiber. The method according to claim 1, wherein the temperature of the air flow near the collector is 25 ° C. or higher and the relative humidity is 30% or lower.