JPS60139818A - Production of high-strength alumina based filament - Google Patents

Abstract

PURPOSE:To obtain the titled filaments with improved stringiness and haldleability, by dry spinning a spinning solution, prepared by mixing an alumina based inorganic compound with polyvinyl alcohol (PVA) at a specific ratio, and having a high viscosity under specific conditions, and heat-treating the resultant filaments. CONSTITUTION:A spinning solution, prepared by mixing (A) an alumina based inorganic compound, preferably aluminum oxychloride, with (B) polyvinyl alcohol (PVA), preferably having 600-2,000 average polymerization degree and 80-97mol% saponification degree and further containing <=2% polyoxyalkylene glycol based antifoaming agent at (95/5)-(70/30), preferably (90/10)-(80/ 20) ratio, and having 2,000-8,000 poises visocosity at 20 deg.C is dry spun by a spinning apparatus set at 35-110 deg.C, preferably 45-80 deg.C nozzle temperature and 30-60% relative humidity in the winding part at <=120, preferably <=100 spinning draft and 3-15%, preferably 5-8% moisture of the wound filaments, and the resultant filaments are then heat-treated to give the aimed filaments.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing alumina-based continuous fibers with excellent spinnability and strength.
This invention relates to a method for producing alumina precursor fiber by stably spinning a high-viscosity spinning dope prepared by mixing a high-viscosity spinning dope (abbreviated as V^) by a dry spinning method to obtain an alumina precursor fiber, and then heat-treating the same to produce a high-strength alumina-based continuous fiber. It is something.

Conventionally, there has been a method for producing alumina fibers by spinning aluminum oxychloride and PVA aqueous solution, or a stock solution of these mixed with silica, etc., as described in Japanese Patent Publication No. 55-'38726.
However, these methods are difficult to stably spin continuous fibers, and are not fully satisfactory as an industrial method for producing high-strength alumina fibers.

In addition, in the production method of alumina-based fibers, the viscosity of the spinning dope is one of the factors for obtaining a good alumina precursor mis, and even if the spinning dope is left for a required period of time during the manufacturing process, it will not maintain a constant viscosity. It is desired to maintain
For this reason, it has conventionally been considered appropriate to maintain the upper limit viscosity at 20°C at 2.000 voids. The concentration is low, which has the drawback of increasing energy loss and equipment costs in the subsequent drying process.

The present inventors have continued to research industrially more advantageous methods for manufacturing alumina fibers, and have found that the viscosity (at 20°C) is 2.
If a high viscosity alumina stock solution with . It was discovered that alumina-based continuous fibers with improved properties and stable spinnability and high strength could be obtained under specific conditions, leading to the completion of the present invention.

That is, the present invention mixes an alumina-based inorganic compound and polyvinyl alcohol in a mixing ratio of 9575 to 70/30,
Solid concentration 25-34%: Viscosity 2.0 at 20°C
A spinning stock solution prepared to have a void range of 0.00 to 8.000 was passed through a spinning trough with a spinning device set at a nozzle temperature of 35 to 110% and a winding part relative humidity of 30 to 80%. This is a method for producing high-strength alumina-based continuous fibers, which is characterized by dry spinning under spinning conditions in which the moisture content of the yarn is in the range of 3 to 15%, followed by heat treatment.

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. Examples include basic chlorides, basic acetates, and basic nitrates of aluminum, especially aluminum oxychloride (e.g., with the formula Al t (OH) 490 l +,
+ ) is preferred. If necessary, compounds of zirconium, magnesium, chromium, nickel, iron, cobalt, yttrium, and silicon can be mixed with the aluminum compound, and specifically, zirconium can be mixed with basic chloride or basic acetate. As basic nitrates, magnesium, chromium, nickel, iron, cobalt, and yttrium are used as chlorides, sulfates, nitrates, acetates, and formates alone or in mixtures thereof as additives to aluminum compounds. As a silicon compound, fine silica (Si0
A colloidal solution (silica sol) in which 2) is dispersed in water is used.

Commercially available PVA can be used as the PVA used in the present invention, but the average degree of polymerization is Boo~2,000 and the degree of saponification is 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.

In the present invention, the mixing ratio of the alumina-based inorganic compound and PVA, solid content concentration, and viscosity of the mixed stock solution are specified because these significantly affect the stability and spinnability of the spinning stock solution and the strength of the alumina fiber. .

Alumina-based inorganic compound and PV of the spinning dope in the present invention
The mixing ratio of A (alumina-based inorganic compound/PVA) is 13515 to 70/3o based on solid content, more preferably 9
0/10 to 80/20 is appropriate, and the mixing ratio is 857
If it exceeds 5, the spinnability of the spinning dope decreases, and the obtained precursor fiber becomes brittle, lacking in practicality, and 70/3.
If it is less than 0, the spinnability will improve, but the strength and flexibility of the alumina fibers will be insufficient.

The alumina-based inorganic compound referred to in the present invention refers to Az03,
It refers to oxides such as S+O2 and Zr%.

What is solid content concentration? be.

The solid content concentration of the mixed spinning stock solution of the present invention is preferably 25 to 34%, and if the solid content concentration is less than 25%, the viscosity of the stock solution (20°C) of the present invention is 2.0. In order to prepare a stock solution with <10 voids or more, it takes a long time to thicken by aging, so it is not suitable for rice use, and if it exceeds 34%, a spinning stock solution that is stable over time cannot be obtained from the stock solution.

The spinning stock solution of the present invention has a viscosity (20°C) of 2,000 to 2,000 s,
It is necessary to adjust the voids to ooo, and if the viscosity exceeds 8,000, the viscosity of the spinning dope is too high, the filtration resistance increases, and the spinnability decreases, making stable spinning impossible. Also 2
At less than 000 voids, the spinning stock solution adheres to the nozzle surface,
So-called nozzle separation becomes worse, which is unfavorable from an industrial standpoint.

The spinning stock solution of the present invention is prepared by heating and aging a stock solution with a solid concentration of 25 to 34% to thicken it to a predetermined viscosity.
The aging temperature also needs to be specified because it affects the viscosity stability of the spinning dope.

The higher the aging temperature, the faster the viscosity of the stock solution increases.However, even if a stock solution whose viscosity has been adjusted through high-temperature aging is left at a low temperature, the viscosity increases rapidly and is not practical, so the aging temperature of the present invention is set at 8.
The temperature is preferably 0°C or lower.

Although the nozzle used in the present invention may be of any shape, it is particularly preferable to use a nozzle plate having a spinning hole with protrusions on the discharge port side.

The temperature around the nozzle during spinning depends on the atmospheric humidity of the nozzle,
Although it is related to the viscosity of the spinning stock solution, the nozzle temperature is 35~
110°C, more preferably 45-80°C,
If the temperature is lower than 35℃, fractures will occur in the yarn and the yarn will break easily at the nozzle.If the temperature exceeds 110℃, the nozzle will become clogged due to deterioration of the raw solution in the nozzle, or the yarn will become too dry due to excessive drying of the yarn directly under the nozzle. There is a decrease in sexuality.

In the present invention, the spinning draft affects the spinning stability and the strength of the alumina fiber, and is preferably 120 or less, more preferably 10
A value of 0 or less is preferable; if it exceeds 120, the spun fibers will have a lot of fuzz, the shrinkage rate will be high when heat-treated to make alumina fibers, and the strength will also decrease.

In the present invention, the spinning draft is determined by the amount of stock solution extruded through the nozzle, the nozzle hole diameter, the spinning winding speed, etc., and specifically refers to the value obtained from the following formula.

The moisture content of the spun precursor fiber affects the handleability of the yarn and the strength of the alumina fiber, so it is preferable to regulate it.

Precursor fibers containing almost no water are rigid, brittle, and difficult to handle. In addition, since alumina fibers obtained from precursor fibers with a high moisture content have low strength and lose flexibility, the moisture content of the precursor fibers after spinning is 3 to 15%, more preferably 5 to 15%.
It is necessary to maintain the relative humidity at 8%, and for this purpose, the relative humidity of the atmosphere in the spinning winding section must be 30 to 60%, more preferably 40%.
It is necessary to control the content to 50%, and it is difficult to obtain the high-strength alumina continuous fiber of the present invention outside this range.

Hereinafter, it will be explained in more detail with reference to Examples.

Example 1 Aluminum powder was gradually added to a 10% aqueous hydrochloric acid solution so that the molar ratio of AIL/cu was 1.9, and the mixture was heated at 100°.
C. for 1 hour to prepare an aqueous aluminum oxychloride solution.

Colloidal silica (silica concentration 2) was added to this aqueous solution while stirring.
0%), average degree of polymerization 1700, degree of saponification 80.5 mol%
A partially saponified PVA aqueous solution (PVA concentration 10%)
M, O, /5i02/PVA (7) mixing ratio is 7011
7113 tonalium was added.

This mixed solution was concentrated under reduced pressure using a rotary evaporator at a bath temperature of 50°C for 3 to 5.6 hours, and the solid content concentration-viscosity (at 20°C) was 30.4%, 210 boids, and 34.0%, respectively. 730 boys, 35.2%-2,4
A stock solution of 80 boids, 35.8%-4,820 boids was obtained. Furthermore, when the stock solutions with solid content concentrations of 30.4% and 34.0% were aged at 70°C for 8 hours and 5.5 hours, the viscosity increased to 7.580 boids and 4,450 boids at 20°C. became.

These stock solutions were kept warm at 30°C, and the viscosity (2
Table 1 shows the results of the measurements.

From the results in Table 1, it can be seen that high viscosity stock solutions obtained by heating and aging a stock solution with a solid content concentration of 34% or less have good stability over time;
It can be seen that a stock solution with a solid content concentration of 35% or more increases in viscosity in a short time even when left at low temperatures, making it difficult to handle industrially.

Example 2 54 parts of aluminum powder was added to 500 parts of an 8% aqueous hydrochloric acid solution under stirring, kept at 84° C., and reacted under reflux for 1 hour to obtain an aqueous aluminum oxychloride solution.

Separately, the degree of saponification is 88 mol%, and the average degree of polymerization is 1.850.
100 parts of partially saponified PVA, 900 parts of water, and 1 part of a polyoxyalkylene glycol antifoaming agent were mixed and dissolved by heating to obtain a PVA aqueous solution having a concentration of 10 parts.

80 parts of colloidal silica with a concentration of 20 parts and 136 parts of a PVA aqueous solution were mixed with 445 parts of this aluminum oxychloride aqueous solution, and the mixture was stirred and concentrated under reduced pressure at 80"O for 3.5 hours, and then 60°C.
Aged for 12 hours to achieve a solid concentration of 31.5% and a viscosity of 20%.
The spinning stock solution had a void of >2.870 °C.

This spinning stock solution was placed in a spin tank, kept warm at 30°C, and a nozzle with a hole diameter of 0.10 m/m and 120 holes was used.
Nozzle discharge rate 2.4cc/min, relative humidity of nozzle part 32
Dry spinning was carried out at a winding speed of 80 m/min using a spinning device set at a temperature of 45° C., a temperature of 76° C. at the bottom of the spinning tube, and a relative humidity of 50 to 55% at the winding section, at a winding speed of 80 m/min. Precursor fibers with a moisture content of 7.5 to 8.2% in the wound yarn were spun continuously for one week, but no trouble occurred during spinning.

The strength of this precursor fiber in an atmosphere of 55% relative humidity is 0.12 g/d, and the elongation is 4.5%. This precursor fiber was heated to 1200°C at a rate of 400°C/H for 1 hour. When heated, it became an alumina-based fiber with a fiber diameter of 0.75 #L and a strength of 247 kg/layer 2 with a soft texture.

Example 3 100 parts of colloidal silica and 200 parts of PVA aqueous solution were mixed with 435 parts of the aluminum oxychloride aqueous solution of Example 2, concentrated under reduced pressure at 70°C for 4 hours with stirring, and then aged at 70°C for 6 hours to reduce the solid content. Concentration 33.8%, viscosity (20℃) 4
．． A spinning stock solution of 570 poise was prepared.

This spinning dope was kept warm at 30°C and the pore size was 0.12+am.
Using a nozzle with 120 holes, the nozzle discharge amount is 3.7cc.
/min, relative humidity of nozzle part 75-80%, temperature 42℃,
Temperature at the bottom of the spinning tube: 85°C, relative humidity at the winding section: 50-55
Winding speed by spinning device set to %? (im/min), continuous spinning was carried out for 3 days at a spinning draft of 2B, and the spinnability was good.

The moisture content of the obtained precursor fiber was 8.0%, and the strength was 0.1.
8g/d, elongation is 7.5%, this fiber is 1,200
After heat treatment at .degree. C. for 1 hour, alumina-based fibers with a diameter of 10.5 gm and a strength of 205 kg/m@2 and a soft texture were obtained.

Example 4 When performing dry spinning in the same manner using the spinning dope used in Example 2, 1. Spinning was carried out using a nozzle with a hole diameter of 0.22 cm/min, a nozzle number of 120 holes, a nozzle discharge rate of 5.0 layers/min, and a spinning draft of 115, with the other spinning conditions being the same as in Example 2.

The strength of the obtained precursor fiber was 0.19 g/d, the elongation was 3.8%, and the strength was 1115 kg/am2 when heated at 120 parts C for 1 hour. was also good, but in this case the spinning draft was set to 135
When raised to a higher temperature, yarn breakage occurred and fuzz was generated, making handling difficult.

Applicant: Nichibi Co., Ltd. Denki Kagaku Kogyo Co., Ltd. Agent Yutaka 1) Yoshio

Claims (1)

[Claims] 1) Alumina-based inorganic compound and polyvinyl alcohol are mixed at a mixing ratio of 8515 to 70/30, solid content concentration is 25 to 34%, and viscosity at 20°C is 2.000 to a, o.
o. The spinning stock solution prepared to remove the voids is processed into a spinning device with a nozzle temperature of 35 to 110°C and a winding part relative humidity of 30 to 60%, with a spinning draft of 120 or less,
A method for producing a high-strength alumina-based continuous fiber, which comprises dry spinning under spinning conditions in which the moisture content of the wound yarn is in the range of 3 to 15%, followed by heat treatment.