JPS61186519A - Production of high-strength alumina-based filament yarn - Google Patents

Abstract

PURPOSE:To obtain the titled yarn having improved fiber strength, processing properties, etc., by subjecting a spinning stock solution of a mixed solution of an alumina-based inorganic compound and a polyvinyl alcohol to dry spinning, heat-treating precursor yarn having a specific water content immediately after spinning, and calcining it. CONSTITUTION:An aqueous solution containing an alumina-based inorganic compound (e.g., aluminum oxychloride, etc.) and polyvniyl alcohol is concentrated under reduced pressure, and aged to prepare a spinning stock solution, which is extruded from a spinning nozzle to a drying column and subjected to dry spinning, to give alumina-based precursor yarn having 2-12wt% water content. Then, the yarn immediately after spinning is heat-treated at 80-180 deg.C for 20 sec-30min, and calcined under heating, to give the aimed yarn.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to an improved method for producing alumina-based continuous fibers, and more specifically to a method for producing alumina-based continuous fibers, and more specifically, a method for producing alumina-based continuous fibers, and more specifically, a method for producing alumina-based continuous fibers. Production of high-strength alumina-based continuous fibers, characterized in that the precursor fibers are preheated under specific conditions in the process of heating and firing the precursor fibers obtained by dry spinning a liquid to produce alumina-based continuous fibers. It is about the method.

[Prior Art] Conventionally, methods for manufacturing alumina fibers have been disclosed, for example, in JP-A-47-29831 and JP-A-50-25822.
A number of methods have been proposed, as typified by Japanese Patent Publication No. 55-387213. In all of these methods, alumina-based fibers are produced by dry-spinning a mixture of an alumina-based inorganic compound and PVA, and heating and firing the precursor fibers as they are without any treatment.

[Problems to be solved by the invention] ゛However, in the above method, the alumina precursor fibers generally have a high hygroscopicity, and if left in a raw atmosphere, they gradually absorb moisture, and the precursor fibers that have once absorbed moisture are When alumina-based fibers are made from alumina-based fibers by heating and firing, the fiber strength decreases and stiffness is observed, so the spun precursor fibers must be handled under conditions of low atmospheric humidity and cannot be twisted and twisted. This is one of the major problems in industrial production, including workability such as weaving.

In view of the above, the present inventors have conducted research on an industrially advantageous method for handling alumina-based precursor fibers after spinning, and as a result, in the production method of alumina-based continuous fibers, precursor fibers obtained by dry spinning are used. The present invention was completed based on the finding that the above-mentioned problems can be solved by employing a preheating treatment step before heating and firing.

[Means for Solving the Problems] That is, the present invention provides an alumina precursor fiber having a moisture content of 2 to 12% immediately after spinning, which is obtained by dry spinning a mixed solution of an alumina-based inorganic compound and PVA as a spinning stock solution. is preheated at a temperature of 80-180°C for 20 seconds to 30 minutes.

This is a method for producing high-strength alumina-based continuous fibers, which is characterized in that the method is then heated and fired.

The present invention will be explained in detail below.

The alumina-based inorganic compound used in the present invention is not particularly limited as long as it forms a refractory inorganic oxide through heat treatment, but aluminum compounds consisting of known water-soluble or colloidal metal salts are used and preferred. These include basic chloride, basic acetate, and basic nitrate of aluminum.

Among these, aluminum oxychloride (for example, the formula AJ22 (OH)49 ONI, I) is particularly preferred. The aluminum compound may optionally contain zirconium, magnesium, chromium, nickel, iron, cobalt, yttrium, silicon Specifically, zirconium can be mixed as basic chloride, basic acetate, basic nitrate, magnesium, chromium, nickel, iron, cobalt, yttrium can be mixed as chloride, sulfate,
Nitrates, acetates, and formates alone or in mixtures thereof are used as additives to aluminum compounds. As the silicon compound, a colloidal solution (silica sol) in which fine silica (cstoz) 1 is dispersed in water is used.

Commercially available PVA can be used as the PVA used in the present invention, but it has an average degree of polymerization of 800 to 2,000 and a degree of saponification of 8.
Particularly preferred is 0 to 87 mol% PVA, and usually 2% polyoxyalkylene glycol antifoaming agent to PVA.
It is preferable to add the following.

Although the mixing ratio and viscosity of the alumina-based inorganic compound and PVA are not specified in the present invention, the alumina-based inorganic compound and PVA are usually
The mixing ratio of VA (alumina-based inorganic compound/PVA) is 8515 to 7α/30, more preferably 90 on a solid content basis.
/10 to 80/20 is appropriate, and the mixing ratio is 9575
If it exceeds 70/3, the spinnability of the spinning dope decreases, and the obtained precursor fiber becomes brittle, lacking in practicality.
If it is less than 0, the spinnability will improve, but the strength and flexibility of the alumina fibers will be insufficient.

In addition, the viscosity of the spinning dope (20°C) is too~4000
Poise is preferable; industrially, spinning can be carried out stably! 500 to 2000 voices are often used.

In the present invention, a normal spinning nozzle can be used for dry spinning the spinning dope.

For example, as shown in Figure 1, the thickness is 2~1! l+++m nozzle plate (metal plate) l spinning dope population 2 to diameter 2-4
A spinning nozzle having tens to hundreds of spinning holes each having a diameter of 0.1 to 1.0 mm on the spinning stock solution outlet side 3 can be mentioned.

Further, an example of a preferable nozzle is a spinning nozzle having a large number of spinning holes in which perforated needle-like protrusions 5 are protruded from the spinning solution outlet of the spinning hole 4 provided in the nozzle plate 1, as shown in the second factor. .

FIG. 3 is a partial sectional view showing one example of the spinning solution outlet shown in FIG. 7 is the protruding part of the spinning hole, d is the inner diameter of the spinning hole, D is the outer diameter of the tip of the protruding part,
D' is the outer diameter of the root portion with the protrusion, L is the length of the protrusion, and i is the length of the spinning hole. However, in FIG. 4, numeral 6 indicates the narrow diameter portion of the spinning hole at the outlet of the spinning dope, and therefore, numeral 6 indicates the length of the narrow diameter portion of the spinning hole.

In the spinning hole shown in Fig. 3, the thickness of the tip of the protrusion is (D-d
)/2, and the wall thickness of this is 0.5 mm or less, preferably 0.02 to 0.21 mm, and d is 0.
05 to 0.4 mm, and l is suitably U/d = 2 to '40.

The length L of the protrusion should be at least 0.5 times the outer diameter of the tip of the protrusion, and the outer diameter D' of the root part of the protrusion may be the same as the outer diameter of the tip of the protrusion, but (D' -D)/2 is preferably within the protrusion length L.

In the present invention, when the moisture content of the precursor fiber immediately after spinning is in the range of 2 to 12%, the temperature is 80 to 180°C.
, preferably at 120 to 150°C for 20 seconds or more in a non-tension mode.
Perform preheating treatment for 30 minutes, preferably 30 seconds to 15 minutes. If the moisture content of the precursor fiber is less than 2%, the fiber will be stiff and fluff will easily occur, making it difficult to spin and wind at high speed. Unfavorable from an industrial standpoint. Further, if the moisture content of the precursor fiber exceeds 12%, it is not preferable because the effect of the preheating treatment of the present invention is poor and it is difficult to obtain a high-strength alumina fiber after firing.

Furthermore, the temperature and time of the preheating treatment significantly affect the effect of the present invention; at temperatures below 80°C, it is difficult to reduce the moisture content of the precursor fibers to less than 3%;
Performing the heat treatment at a temperature exceeding 0° C. is undesirable because the heat treatment will be performed more excessively than necessary, and the alumina continuous fibers after firing will only have weak strength. For the same reason, the time of the preheating treatment is also specified.

In other words, the effect of the present invention cannot be improved with heat treatment for a short time of less than 20 seconds, and high-strength alumina continuous fibers cannot be obtained even if the precursor fibers that have been preheated are fired for a heat treatment time of more than 30 minutes. It is not desirable because it cannot be used.

By the above-described preheating treatment in the present invention, the moisture content of the alumina-based precursor fiber is reduced from 3 to 12% of the precursor fiber immediately after spinning to 3% or less, and excess moisture and adsorbed water are removed. Bound water is removed.

Although any conventional heating device can be used in the preheating treatment of the present invention, from an industrial standpoint, a hot air dryer in an air atmosphere is effectively used.

[Function] Although it is not yet clear why high-strength alumina-based continuous fibers are induced by firing the preheat-treated precursor fibers of the present invention, Since high-strength alumina-based continuous fibers are induced even if the fibers are allowed to dry, the adsorbed water contained in the precursor fibers can be reduced by preheating under the conditions of the present invention to the extent that the basic structure of the fibers is hardly changed. This is thought to be because the fiber structure is relatively stable due to the removal of bound water and the fiber structure does not change much even if moisture is absorbed thereafter.

[Example] Hereinafter, the present invention will be explained in more detail with reference to Examples.

EXPERIMENTAL EXAMPLE First, the influence on product strength caused by the preheating treatment in the present invention will be explained using an experimental example.

PVA with homopolymerization degree of 1700 and saponification degree of 80.5 mol%
10% aqueous solution, aluminum oxychloride (Ag101
Ab (h
/5i02 (weight ratio) 80/20, (AJ2203
+S i02 )/PVA in a weight ratio of 87/13 and reduced pressure at 80°C! By shrinking and aging, a spinning stock solution having a viscosity of 1500 voids at 20° C. was prepared. This spinning stock solution was passed through a spinning nozzle (diameter 110 mm, thickness 10 mm) having 180 holes with a hole diameter of 0.18 mg
The liquid was pumped using a gear pump using a 50°C drying tower (
A continuous alumina-based precursor fiber was obtained by extrusion into the fiber (4 layers in length). The moisture content of this precursor fiber is 7%
Met.

The precursor fibers immediately after spinning were subjected to preheating treatment under varying preheating treatment conditions, and the preheated fibers were allowed to absorb moisture under various standing conditions. Subsequently, the fibers were heated to 1200°C.
The fibers were heated and fired for 1 hour to produce alumina-based continuous fibers, and their strength was measured. The results are shown in Table 1.

These results show that precursor fibers treated within the range of the preheat treatment conditions of the present invention can become high-strength alumina-based continuous fibers after firing even if they are subsequently left in a high humidity (relative humidity) atmosphere. Recognize.

In addition, the moisture content of the precursor fiber referred to here is the degree of reduced pressure of 7eT.
It was determined by the linear equation after drying at 80° C. for 1 hour in a vacuum dryer (orr).

The strength of the medium fibers was measured using an Instron tensile strength measuring machine.

Example 1 Using the spinning stock solution used in the experimental example, the pore size was 0, lGm1
Dry spinning method using a nozzle with 160 holes at a spinning speed of 20 m.
Fineness 420d/1BOf spun at /min, strength 0.1
Precursor fibers of 5 g/d, elongation of 2.6%, and moisture content of 8% were collected in an atmosphere of 20°C and relative humidity of 40%, and then heat-treated in heated air at 120°C for 15 minutes. , the moisture content of this precursor fiber was 0%. When the previously heat-treated fibers were left in an atmosphere of 20°C and 65% relative humidity for 7 days, the moisture content of the fibers was 17% and the strength was 0.13.
3/d, and elongation was 2.8%. This M&male was heated to 1200°C at a heating rate of 300°C/hour in its whole state,
The alumina continuous fiber obtained by heating and firing at the same temperature for 14 hours has a fiber diameter of 9.21φ and a strength of 233Kg/ram2.
It had a soft texture.

Example 2 The precursor fiber (moisture content 8%) obtained in Example 1 was heated at a temperature of 150
The sample was introduced into a heating machine with a heating length of 10 m set at .degree. C., and preheated while being continuously wound at a winding speed of 18.5 Il 1 minute.

This yarn was left in an atmosphere of 20° C. and relative humidity of 63 to 88% for one day, twisted at 80 T/m using an up twister, and three yarns were twisted. 100 pieces of this doubled yarn
continuously into a heating furnace with a temperature gradient of ~450 °C,
Heat treatment is performed at 450℃ for 30 minutes, followed by 450~1
When fired for 1 hour at 1200°C in a firing furnace with a temperature gradient of 200°C, the fiber diameter was 9.2 JLra.
, an alumina-based continuous W& fiber having a strength of 202 kg/mm2 was obtained.

[Effects of the Invention] As explained above, the present invention prevents a decrease in strength after firing due to moisture absorption of the precursor fibers by preheating the precursor fibers immediately after spinning under specific conditions before heating and firing them. However, since the strength of the alumina-based continuous fibers does not decrease even if the precursor fibers are allowed to absorb moisture thereafter, storage and handling of the precursor m-fibers becomes easy, and the industrial value is extremely high.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing one example of a spinning hole used in the production method of the present invention, FIG. 2 is a sectional view showing another example of a spinning hole, and FIG. 3 is a sectional view showing another example of a spinning hole used in the manufacturing method of the present invention. FIG. 4 is a partial sectional view showing another example of the spinning solution outlet of the spinning hole shown in FIG. 2. FIG. l...Nozzle plate 2...Spinning dope inlet 3...Spinning dope outlet 4...Spinning hole 5...Hole-shaped needle-shaped projection 6...Narrow diameter portion 7...Protrusion portion

Claims (1)

[Claims] Alumina precursor fibers with a moisture content of 2 to 12% immediately after spinning obtained by dry spinning a mixture of an alumina inorganic compound and polyvinyl alcohol as a spinning stock solution are heated at a temperature of 80 to 180°C for 20 seconds to 30 minutes. A method for producing high-strength alumina-based continuous fibers, which comprises heat treatment and subsequent heating and firing.