JPS60139817A - Production of alumina based inorganic fiber precursor - Google Patents

Abstract

PURPOSE:To obtain the titled precursor having improved stringiness, handleability and processability and a high strength, by dry spinning a spinning solution prepared by adjusting an alumina based inorganic compound and polyvinyl alcohol (PVA) based polymer to a specific mixing ratio and viscosity under specific conditions. CONSTITUTION:A spinning solution prepared by adjusting (A) an alumina based inorganic compound, preferably aluminum oxychloride, and (B) a polyvinyl alcohol (PVA) based polymer, preferably PVA having >=600 average polymerization degree and 80-97mol% saponification degree to a mixing range with (70/ 30)-(50/50) range and a viscosity within 200-4,500 poises range, preferably 800-3,500 poises range at 50 deg.C is dry spun by a spinning apparatus set at 35- 150 deg.C, preferably 60-120 deg.C nozzle temperature at <=30 spinning draft to afford the aimed precursor.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing an alumina-based inorganic fiber precursor having excellent spinnability and processability.

In 1994, as the usefulness of inorganic fibers was recognized, various patents for their manufacturing methods were proposed, and inorganic fibers with various performances began to be produced on an industrial scale.・ Is the production method of these inorganic Ml 16 developed in the 1970s? -29
E131, JP Moe 4B-56÷, JP 50-2582
2. Tokuko Sho 51-12738, Tokuko Moe 55-38728
These are all represented by inorganic compounds of various compositions alone or mixed with various organic polymers in a range of 10% or less to prepare a spinning stock solution, which is then extruded into an air stream through a nozzle to shorten the spinning stock. The fibers or □ are continuous fibrous precursor fibers, which are then heat-treated to produce a perilla-free fiber.

Conventionally, the precursor fibers produced by any of the manufacturing methods have many disadvantages in terms of brittleness and handling. Heat treatment improves the tensile strength and makes it a little easier to handle, but it has low elongation and lacks flexibility, so if continuous fiber is used for casting, it will be difficult to process textiles. There are shortcomings.

The present inventors have conducted extensive research into methods for producing continuous inorganic fibers, particularly alumina-based inorganic fiber precursors, that improve the handling and processability drawbacks involved, and have identified a method for preparing a spinning dope. By adopting these spinning conditions, we have discovered that a precursor fiber with excellent spinnability and handling properties can be produced, and that alumina-based fibers with high strength can be obtained from this, and have completed the present invention.

That is, in the present invention, an alumina-based inorganic compound and a polyvinyl alcohol (hereinafter abbreviated as PVA)-based polymer are mixed at a mixing ratio of 7.
Mix in the range of 0/30 to 50150 to determine the viscosity (50℃
) Prepare a spinning stock solution of 200 to 4,500 poise and dry-spun it with a spinning tube with a nozzle temperature set at 35 to 150°C under conditions of a spinning draft of 30 or less to obtain a continuous fiber precursor fiber. and, if necessary, relative humidity 3
Processes such as twisting and weaving are performed in an atmosphere of 0 to 50%, followed by heat treatment to produce alumina fibers or molded products thereof. The greatest feature of the present invention is the excellent spinnability and handling properties of the precursor fiber.

The alumina-based inorganic compound used in the present invention is not particularly limited as long as it forms a refractory inorganic oxide by heat treatment, but aluminum compounds consisting of known water-soluble or colloidal metal salts are used and are preferred. Examples include basic chlorides, basic acetates, and basic nitrates of aluminum, and among these, oxyaluminum chloride is particularly preferred. The aluminum compound may contain zirconium, magnesium, chromium, nickel,
Compounds of iron, cobalt, yttrium, and silicon can be mixed, specifically zirconium can be mixed with basic chloride,
Basic acetates, basic nitrates, magnesium, chromium, nickel, iron, co-salts, acetates, and formate salts may be used singly or in mixtures thereof as additives to aluminum compounds. As a silicon compound, fine silica (S
The PVA polymer used in the colloidal solution (silica sol) in which i02) is dispersed in water is particularly preferably PVA with an average degree of polymerization of 800 or more and a degree of saponification of 80 to 87 mol%. PVA containing a partially modified group may be used, or a water-soluble polymer such as polyethylene oxide may be partially mixed and used.

In the present invention, the mixing ratio of the alumina-based inorganic compound and the PVA-based polymer and the viscosity of the mixed stock solution are determined based on the spinnability, handling properties of the obtained precursor fibers, and the alumina-based fibers derived therefrom. This is because the alumina-based inorganic compound and PV in the spinning dope of the present invention significantly affect the physical properties of
Mixing ratio with A-based polymer (alumina-based inorganic compound/P
VA polymer) is 70/30 to 50150 based on solid P content.
is preferable; if the mixing ratio exceeds 70/30, the resulting precursor mixture is brittle and has little effect on improving handling properties.
In addition, in the case of 50150 W4tp, the handling of the precursor fiber is good, but the strength of the inorganic fiber obtained from this is low;
The effect of the present invention is halved.

The viscosity (50'C) of the spinning stock solution is preferably 200 to 4,500 poise; if it is less than 200 poise, it will be difficult for the stock solution extruded from the nozzle to separate from the nozzle, and if it exceeds 4,500 poise, the filtration pressure will increase. The deterioration of stringability and threadability becomes significant, and both are impractical. In addition, in the present invention, 800
A stock solution viscosity of ~3,500-j drops (50°C) is particularly preferred from the viewpoint of spinning stability.

The nozzle part temperature is related to the nozzle part atmospheric humidity, the viscosity of the stock solution, etc., but the nozzle part temperature needs to be set at 35 to 150°C, more preferably 60 to 120°C, and 30°C.
If C is not used, fractures will occur in the fibers and the strength will decrease, and if the temperature exceeds 150°C, the viscosity of the raw solution will rapidly increase due to the deterioration of the alumina-based inorganic compound, which will easily cause nozzle clogging and increase the Part of the period is stable spinning.

: , i , , / , ;/ The atmospheric humidity of the Jb section is not an essential factor in the present invention 1, but the relative humidity around the nozzle section is 7.
If it is maintained at 0% or more, good threadability and properties are exhibited, which is advantageous for stable spinning.

The nozzle used in the present invention may have any shape, but it is particularly preferable to use a nozzle plate having a protrusion and a protruding spinning hole on the discharge port side.

The spinning draft affects the dimensional stability of the obtained precursor fibers, and fibers spun with a high draft have a high shrinkage rate due to moisture absorption, which poses problems in processability such as weaving. A-free fibers derived from body fibers have low throat strength. Therefore, in the present invention, it is necessary to regulate the spinning draft to 30 or less.

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.

Precursor fibers with a spinning draft of 30 or less are heated to a relative humidity of 30 to 5
When handled in a 0% atmosphere, the fibers absorb moisture to an appropriate degree, exhibit flexibility, exhibit little dimensional change due to moisture absorption, and are easy to process such as weaving, thereby fully demonstrating the characteristics of the present invention.

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

Example 1 450 g of aluminum hydroxide in 1,380 g of 35% hydrochloric acid
was added and dissolved at 90℃, and while maintaining that temperature, 2.4 g of water and 720 g of aluminum powder were gradually added while stirring.
A solution with an L/c1 molar ratio of 1.8 was prepared. Add colloidal silica (silica concentration 20%) to this solution while stirring (kept at 50°C).
) 3,800g, degree of saponification 80 mol%, average degree of polymerization 1
．． 700 (7) PVA solution (PVA concentration 10%) 1
, 950g and concentrated under reduced pressure to form A203 and SiO□
An alumina spinning dope having a total concentration of 34.2% and a viscosity (50° C.) of 2.100 poise was prepared.

Separately, the degree of saponification is 94.5 mol%, and the average degree of polymerization is 1.7.
Mix 1,800 g of 00 PVA and 3.21 g of water and dissolve by heating to obtain a PVA concentration of 38% and viscosity (80°C) 1.
A PVA spinning stock solution of 580 voids was prepared.

Both of these spinning stock solutions are pumped using metering gear pumps,
Static mixer (15 elements) just before the nozzle part
By dry spinning, precursor fibers in the form of continuous fibers having various mixing ratios of the two stock solutions and different spinning drafts were obtained.

The mixing ratio of both stock solutions was prepared by arbitrarily selecting the rotation ratio of the gear pump, and the spinning draft was prepared by appropriately combining the amount of stock solution extruded through the nozzle, the nozzle hole diameter, and the spinning winding speed.

The spinning conditions were a relative humidity of 85% at the nozzle and a temperature of 80°C.
1 Relative humidity at the bottom of the spinning cylinder 30%, temperature 120°C □, used, size □ and hole diameter. , 08-0. '14mm, number of holes. . Table 1 shows the strength and elongation of the precursor fibers obtained in this example with various mixing ratios and of alumina-based fibers obtained by heat-treating the same fibers at 1000°C (heating rate 200°C har). This is a compilation of the measurement results.

Table 1 (Note) 1) The mixing ratio is 7) Iy Mi+ (Alx08+
S+0. L) /pvA mixing ratio 2) Precursor fiber, spinning trough) 4. m degrees 2 to 7 d/f 3) Alumina fiber diameter is 8 to 1 lt L 4) Each strength and elongation were measured in a humidity controlled atmosphere at 20°C and relative humidity 50% Based on the results in Table 1, the alumina/PVA mixing ratio It can be seen that the precursor fiber with a ratio of 80/20 and the alumina fiber with a mixing ratio of 40/flIO have low strength and are poor in handleability or practicality.

Table 2 also shows various precursor fibers with different spinning drafts obtained in this example (the precursor fibers are fibers with a fineness of 3 to 3.2 d/f(1) obtained from an alumina/PVA mixing ratio of 60/40).
Equilibrium shrinkage rate when left in an atmosphere with a temperature of 20°C and a relative humidity of 50% to absorb moisture and the precursor fibers before and after absorbing moisture (t)
, heat treatment at ooo°C (heating rate 200”O/hr)
1. The results of measuring the strength of alumina fibers are shown.

From the results shown in Table 2, the precursor fibers with a high spinning draft have a high shrinkage rate due to moisture absorption, and the alumina fibers derived from the shrinked fibers have low strength.

I understand.

Example 2 550 g of aluminum powder was gradually added to 4000 g of 10% mM, kept at 80 to 100° C., and reacted under reflux for 1 hour to form a solution. Add 1550g of colloidal silica with a concentration of 20% to this and concentrate under reduced pressure at 50"O to form A2.
An alumina solution (alumina/silica mixed solution) with a total concentration of 03 and Sing of 32.5% was prepared.

In addition, the degree of saponification is 88.5 mol%, and the average degree of polymerization is 1.7.
00 (7) Mix 380g of PVA and 620g of water,
A PVA solution was prepared by heating and dissolving. - 1,540 g of this alumina solution and 1,320 g of the PVA solution were stirred and mixed at room temperature for 1 hour to prepare a spinning stock solution with an alumina/PVA mixing ratio of 50,150 and a viscosity (50° C.) of 1,840 voids. This stock solution was stable at room temperature without any change in viscosity.

Using a nozzle with a hole diameter of 0.1a and a number of holes of 90, this spinning dope was heated at a relative humidity of 80% and a temperature of 100°C.
1 With a spinning tube with a relative humidity of 45% at the bottom of the spinning tube and a temperature of 140 °C, the spinning winding speed was 8 h/min, and the spinning draft was 5.5.
Dry spun with fineness 270d/90f, 8 strength 0.24
, God precursor fibers were obtained. The dry spinnability was good, and there was no yarn breakage during 31 consecutive spinning cycles.

This precursor fiber was twisted with a number of twists of 1 in an atmosphere with a relative humidity of 50%.
After heating to 00T/M, string is made, IJlocm, fabric weight 220
It was made into a tape shape of g/a2.

This was heated to 450°C at a temperature rate of A of 00°C/hr, and then heated to 1,000°C at a temperature of 300°C/hr.
A tape-like string with a thickness of 6 cm and a weight of 1140 g/m2 was obtained, which was made of alumina thread #lt.

Example 3 2270 g of alumina solution of Example 2 and 114 g of PVA solution
A spinning stock solution having an alumina/PVA mixing ratio (pair 0/30, viscosity (50°C) of 1.280 poise) was prepared by stirring and mixing 0 g at room temperature.

Using a nozzle with a hole radius of 10.07 mm and 60 holes, this spinning stock solution was wound through a spinning tube with a relative humidity of 70% at the nozzle, a temperature of 6° C1, a relative humidity of 30% at the bottom of the spinning tube, and a temperature of 100°C. Take-up speed 50+w 7 minutes, spinning draft 30
Dry spinning was performed under two spinning conditions to obtain a precursor fiber with a fineness of 150 d/60 f and a strength of 0°L4 g/d. The spinning stability was such that there was almost no yarn breakage during continuous spinning for 3 days.

After weaving this precursor fiber into a flat moth tissue in an atmosphere with a relative humidity of 30% to form a fabric with a basis weight of 110 g/m2, t.
It was heat-treated at 00° C. to obtain a woven fabric made of alumina fibers with a basis weight of 72 g/112. Alumina fiber strength expert 1
It was 75 kg/ll112.

Applicant: Nichibi Co., Ltd. Denki Kagaku Kogyo Co., Ltd. Agent Fyo 11J 14 Male

Claims (1)

[Claims] 1) Viscosity (50"C 200-4,500) prepared by mixing an alumina-based inorganic compound and a polyvinyl alcohol-based polymer at a mixing ratio of 70/30 to 50150
Add the Poise spinning dope to the nozzle temperature of 35 to 150. '
C! With the spinning device set within the range of , the spinning draft 3
A method for producing an alumina-based inorganic fiber precursor, comprising dry spinning at a temperature of 0 or less.