JPS62191513A - Production of metal oxide fiber - Google Patents

Abstract

PURPOSE:To obtain the titled fiber having high strength, by adding a water-soluble inorganic polybasic acid (salt) to an aqueous composition containing PVA and a water-soluble metallic compound and/or a water-dispersible metallic oxide, concentrating and aging the mixture and spinning the product. CONSTITUTION:A water-soluble inorganic polybasic acid and/or its salt are added to an aqueous composition containing PVA and a water-dispersible metallic oxide and/or or a water-soluble metallic compound giving desired metallic oxide by baking. The mixture is concentrated and aged. When the apparent viscosity of the aqueous composition is increased by >=10%, the composition is subjected to dry-spinning and the resultant precursor fiber is baked.

Description

[Detailed description of the invention]

TECHNICAL FIELD The present invention relates to a method for producing metal oxide mH. More specifically, the present invention relates to a water-soluble metal compound that provides a desired metal oxide by firing, or a water-dispersible gold l1lWIi compound thereof, and polyvinyl alcohol (hereinafter referred to as PV
A spinning solution containing (abbreviated as Δ) is spun by a dry method,
In the method for producing metal oxide fibers by firing, by greatly improving the spinnability of the spinning dope, dry spinning, especially continuous dry spinning, can be made extremely easy, and the general drawbacks of dry spinning can be overcome. A high-strength metal oxide I1m is provided by preventing the clogging of spinneret pores due to drying and coagulation of the spinning dope in certain pores of the spinneret, and by firing the obtained dense precursor fibers. The present invention relates to a method for producing metal oxide fibers. Prior Art The technology of producing metal oxide fibers by spinning and firing an aqueous solution containing an organic polymer and a precursor compound capable of producing a desired metal oxide has been used to produce alumina fibers and zirconia fibres, which have particularly excellent heat resistance. It's being used. The spinning method in this case includes a method in which the spinning stock solution is extruded into a moist air stream flowing at high speed and blown away (Japanese Patent Publication No. 55-36726, No. 37
610, 1983-44626), and a centrifugal spinning method in which the spinning solution is blown out of the pores by centrifugal force (Japanese Patent Laid-Open Nos. 55-20234, 1982-20239, and 1983-30467). There is. The product obtained by spinning and firing in this manner is a short tIa navy blue color with a length of several centimeters to several tens of centimeters, and has low strength, so it is mainly used as a heat insulating material. On the other hand, since the spinning dope used in the above method has insufficient spinnability for continuous dry spinning, it is difficult to industrially produce 11[ Moreover, it had the disadvantage that it could only be made with low strength. In addition, a manufacturing problem common to short m-fibers and continuous vans is that if the spinnerets are directly spun into a dry atmosphere, the raw solution will dry and coagulate in the pores of the spinneret, clogging the pores. Ta. The phenomenon of blockage of the spindle pores can be prevented by slowing down the coagulation of the spinning stock solution used. In order to obtain a spinning stock solution with slow coagulation, it is necessary to lower the solid content of the stock solution a little, add an appropriate amount of a solvent that has a higher vapor pressure than water and is difficult to dry, and change the amount of PVA added. A number of methods have been tried, such as increasing the amount by a small amount. However, if this method is used, it takes a long time for the filaments to coagulate and the filaments break during that time, making continuous spinning difficult. By the way, it is well known for organic materials that when a fiber is drawn, the constituent molecules of the fiber are oriented in the direction of tension, becoming denser and improving strength. This also applies to the production of metal oxide fibers, so whether the precursor fibers are dense or not is closely related to the strength of the metal oxide fibers. [Summary of the Invention] Summary The present invention aims to provide a solution to the above-mentioned problems, and provides a water-based compound containing a water-soluble metal compound that provides a desired metal oxide upon calcination, or a water-dispersible metal oxide, and PVA. After adding a water-soluble inorganic polybasic acid and/or a salt of an inorganic polybasic acid as a third component to the composition, the aqueous composition is concentrated to a desired concentration, aged, and then subjected to dry spinning. This goal is achieved by spinning. That is, the method for producing metal oxide fibers according to the present invention involves concentrating to a desired concentration an aqueous composition containing a water-soluble metal compound that provides a desired metal oxide by firing or a water-dispersible metal oxide, and polyvinyl alcohol. In the method for producing metal oxide fibers, which comprises forming precursor fibers by a dry spinning method and firing the same, a water-soluble inorganic polybasic acid and/or an inorganic polybasic acid is added to the aqueous composition. It is characterized in that it is concentrated after addition of salt and aged to increase the apparent viscosity of the aqueous composition by at least 10% before spinning. Effect The main effect of the present invention is that metal oxide continuous I! It is possible to easily produce crude precursor fibers using a very common dry spinning method, and there is no problem of pore clogging as mentioned above, and an excellent strong product can be obtained by firing. be. Such effects can be achieved by adding an inorganic polybasic acid or its salt as a third essential component to a conventional aqueous composition consisting of two essential components, a metal compound and an organic polymer, and also by the process of aging. It was obtained through the process. This effect of the inorganic polybasic acid or its salt is probably the result of these additives acting as a crosslinking agent in some form in the aqueous composition of the present invention (however, this does not limit the scope of the present invention). ). PV
Many substances are known that exhibit a coagulating or gelling effect on A, but as far as the present inventors know, it is not possible to perform dry spinning from an aqueous composition consisting of two components of PVA and these substances. No suitable spinning solution was obtained. Therefore, such effects of the present invention have been obtained for the first time with a composition containing three components: a metal compound, an organic polymer, and an inorganic polybasic acid (or a salt thereof). In this way, the reason why the spinning dope of the present invention exhibits excellent spinnability is simply the interaction between PVA and additives.

It must be considered that this is not due to the metal compound or only the interaction between the metal compound and the additive, but is due to the synergistic effect of the three essential components mentioned above. Now, as the aqueous spinning composition is concentrated, it gradually becomes a highly concentrated viscous liquid, and if the concentration is continued further, -7 becomes partially solidified or dissolved substances precipitate. For this reason, spinning is performed using a composition that is homogeneous and has an appropriate consistency, but with conventional two-component compositions, spinning can be carried out to the maximum extent possible while maintaining a homogeneous state. Even after concentration, it was not possible to obtain a stock solution with satisfactory stringability. If the spinning solution of the present invention is simply concentrated, it will not differ much from the conventional spinning solution, but as it is aged in an appropriate manner, it will develop excellent spinnability. In this way, inorganic polybasic acids or their salts are added as a third essential component to the conventional two components (some of which include substances that are said to have almost no coagulation or gelling effect on PVA). It may be said that it was unexpected that excellent spinnability could be imparted to the spinning stock solution by adding sulfuric acid, phosphoric acid, etc.), concentrating it, and then going through the aging process. In addition, since the m-fiber spun from the spinning dope of the present invention can be easily drawn, it is possible to form a metal oxide r with excellent strength by drawing.
aN can be obtained. In addition to the above-mentioned effects, the present invention also has the following effects. In other words, due to the excellent spinnability achieved by the action of inorganic polybasic acids, it has become possible to perform stable continuous spinning even with a stock solution that coagulates more slowly than before. The pores no longer become clogged even when extruded inside. [Detailed Description of the Invention] 1. The spinning dope used in the present invention is an aqueous composition containing a water-soluble metal compound that provides a desired metal oxide upon firing or a water-dispersible metal oxide, and PVA. A viscous aqueous solution in which an inorganic polybasic acid or a salt of an inorganic polybasic acid is added to the solution, concentrated to a desired concentration, and aged until it produces stringiness that allows continuous spinning using a dry spinning method. or a dispersion (preferably the former). It goes without saying that the type of metal targeted by the present invention is determined by the metal oxide selected as the constituent material of the fiber, and it is water-soluble and can be converted into an oxide by firing. It can be anything as long as it provides possible compounds. Examples of such metal compounds include chlorides and nitrates of aluminum, magnesium, and zirconium.
These include basic salts. These can be used alone or in combination. In addition, a water-dispersible metal oxide can be used in combination with this water-soluble metal compound if necessary, but such water-dispersible metal oxides include
A colloidal aqueous dispersion such as neutral to acidic silica gel or alumina sol is preferred. As described above, the term "metal" as used in the present invention includes silicon. Among these metal compounds, basic aluminum chloride is practically important, and in this sense, the present invention is particularly effective in producing metal oxide fibers containing alumina as a main component. Such basic aluminum chloride is an inorganic polymer compound represented by the formula (A + 2(OH).C10,)□.
It is usually obtained as an aqueous solution of about 0.1≦n≦5.1 and m≦10, but when used in the present invention, 3≦n
Particularly preferred is one in which m≦5 and m≦10 because the amount of chlorine gas generated during firing is small. PVA PVA, another essential acid in the spinning dope, can be of various types for any purpose. If only the spinnability of the spinning stock solution is to be improved, PVA with a high degree of polymerization or a high degree of saponification can be said to be superior. However, those with too high a degree of polymerization or too high a degree of saponification have poor compatibility with water-soluble metal compounds. Therefore preferred PVA
Polymerized reeds cost 500-2500. More preferably 1000
~2000. It is. In the present invention, it is possible to use PVA having a saponification degree of 99% or less and partially having residual organic acid groups (usually vinegar!!i groups). However, what is commonly called fully saponified PVA, which has a saponification degree of 98% or more, has high crystallinity.
Even in an aqueous solution, there is a large interaction between molecules, so a spinning stock solution using PVA has excellent spinnability but is difficult to stretch, making it a dense precursor! The disadvantage is that it is difficult to obtain I fibers. Therefore, particularly preferred PVA in the present invention is a partially saponified product having 2 mol% or more of residual organic acid groups, which has excellent elongation and water solubility. Salts of bases and bases are inorganic polybasic acids and salts of inorganic polybasic acids are added to improve the spinnability of the spinning dope, and are optional as long as they achieve this purpose. It's possible. For example, in the present invention, (a) dibasic acids such as sulfuric acid, sulfite, dithionic acid, polythionic acid, phosphonic acid, selenic acid, selenite, or-1-telluric acid, and (b) tribasic acids such as orthophosphoric acid and orthoboric acid. Acids, (c) tetrabasic acids such as hypophosphoric acid and diphosphoric acid, and (d) salts thereof, etc. can be used. Among these, when ripened by adding those that generate polyvalent anions such as sulfur and phosphorus oxides in an aqueous solution, the spinning stock solution slowly thickens over a long period of time, so it is possible to make appropriate threads. It is particularly preferable because it can be spun as soon as it exhibits properties. In the present invention, if at least one compound selected from these is used, J: Yes. Further, the spinning stock solution thickened with such an acid or its salt has the advantage that it exhibits excellent spinnability and is easily drawn. Sulfuric acid and phosphoric acid are particularly preferred in the present invention. Amount Ratio: As mentioned above, the amount ratio of these essential components is such that the thread has excellent spinnability and stretchability, and has an appropriate level of coagulation to the extent that the pores will not be clogged even if the pores are extruded directly into a drying atmosphere. It can be anything, provided that a spinning dope with a certain speed is obtained. The excellent spinnability of the spinning stock solution of the present invention is mainly obtained by the addition of an inorganic polybasic acid or a salt of an inorganic polybasic acid and aging. When the amount is 10 parts by weight or more per 100 parts by weight of the refill, particularly excellent stretchability can be obtained, and a suitable solidification rate can be obtained. However, if the PVA content is too large, the coagulability of the stock solution will be too low, and the strength of the fired product will be reduced due to an increase in the number of components eliminated during firing. Therefore, the preferred PV
The amount of A added is 10 to 50 parts by weight based on 100 parts by weight of the corresponding oxide of the water-soluble metal compound. Another essential component, an inorganic polybasic acid or a salt of an inorganic polybasic acid, can be added to an aqueous composition containing the metal compound and PVA to concentrate and age it. It is added to impart spinnability, and in this sense, the amount added can be arbitrary. However, like PVA, overusing it does not necessarily give good results. Therefore, in order to achieve the above object, the preferable addition amount is usually 0.1 to 10 parts by weight based on 100 parts by weight of the equivalent oxide of the water-soluble metal compound. Auxiliary Components Various additives as shown below may be added to the spinning dope of the present invention, which has the above three components as essential components, as required. (a) Water-soluble polymer compounds other than PVA, such as polyacrylamide, polyacrylic acid, polyethylene oxide, polyethylene glycol, polyvinylpyrrolidone, alkylcellulose, carboxyalkylcellulose, hydroxyalkylcellulose, starch, dextrin casein, glue, gelatin, etc. Since the present invention uses PVA as the fiber-forming polymer, the amount of these water-soluble polymer compounds should be less than that of PVA. (b) Surfactants and plasticizers for PVA, such as alcohols, glycols, glycerin,
Anionic nonionic surfactants, etc. (C) Colloidal stabilizers, such as formic acid, acetic acid, hydrochloric acid, etc. (d) Antifoaming agents, such as higher alcohol-based ones such as ocdyl alcohol and cyclohexanol, and silicone-based ones. Among these, those shown in (a) and (b) also have the effect of suppressing rapid solidification of the spinning dope. Production of spinning dope The spinning dope is usually prepared by mixing an aqueous solution or aqueous dispersion of the above-mentioned metal compound with an aqueous PVA solution, and adding an aqueous solution of an inorganic polybasic acid or a salt of an inorganic polybasic acid little by little while stirring the mixture. It is obtained by mixing, concentrating, and aging. The components can be mixed by any method that allows them to be combined all at once or stepwise in any order to finally obtain an aqueous solution or dispersion of homogeneous composition. Mixing may be performed under heating. The mixing (rice concentration) is preferably carried out at a temperature of 80°C or lower, particularly 60°C or lower. Concentration is usually carried out under heat and/or reduced pressure with the above considerations in mind. In this way, the spinning dope is concentrated until it has a viscosity of usually 100 voids or more. This viscous liquid alone has insufficient spinnability when spun using a dry method, but when it is further aged, it exhibits excellent spinnability. Aging is performed by keeping the spinning stock solution in a non-evaporated state or in a sealed state, preferably below 80°C.
In particular, it is usually stored at a temperature below 40°C. If the spinning dope is stored under these conditions for at least 12 hours or more, the spinnability will improve. When the apparent viscosity of the spinning dope increases by 10% or more from the initial viscosity immediately after concentration due to aging, it exhibits excellent spinnability. Spinning The spinning stock solution of the present invention is prepared using special spinning techniques (for example, using a special coagulating solvent bath to coagulate the fibers, or dry spinning in a special humid atmosphere to suppress coagulation). ) can be easily made into fibers by ordinary dry spinning methods. The atmosphere for spinning the spinning dope may be either a wet or dry atmosphere, but in order to easily obtain thin filaments, a dry atmosphere (especially one consisting essentially of air) with a relative humidity of 60% or less is preferred. The spinning stock solution of the present invention can also exhibit its characteristics in the so-called "blow spinning method" in which it is extruded through pores and blown away with a high-speed air stream, and in the "centrifugal spinning method" in which it is blown out by centrifugal force. The spinning stock solution has the most preferable characteristics when used when spinning continuous fibers by a continuous spinning method. In this continuous spinning method, fibers are extruded from a spinneret into a dry atmosphere (usually air) and continuously wound up according to the general dry spinning method, or passed through rotating rollers into a suitable fiber collection container. Continuous long fibers can be obtained by storage. At this time, the filaments are drawn and elongated by the tension during spinning, while drying and coagulating. When collecting the filaments, it is desirable to heat them using an appropriate method to completely dry them while collecting them. In addition, IIN collected in this manner is referred to as a precursor fiber in the present invention. Firing The firing of the precursor strip produced as described above is known per se, and therefore this step can be carried out in any convenient manner in the present invention. In the present invention, for example, the precursor fibers in a relaxed or taut state are heated in air or an inert gas atmosphere to slowly carbonize the PVA or other organic material, and then heated in an oxidizing atmosphere, preferably in air. heating to burn off carbonized organic materials and convert metal compounds to the corresponding oxides. This oxide may be further calcined in vacuum or in a hydrogen atmosphere. Moreover, the heating may be performed in one step instead of in two steps, one under an inert gas atmosphere and one under an oxidizing atmosphere. Experimental Examples Example 1 400q of polyaluminum chloride (hereinafter abbreviated as PAC) with a basicity of 80% and a content of 110.6% by weight of A1, and SiO
Phosphoric acid was added to a mixture of 100 g of acidic colloidal silica (Snowtex-OJ manufactured by Nissan Chemical Co., Ltd.) containing 20% by weight of 2 and 300 g of an aqueous solution containing 10% by weight of PVA with a degree of saponification of 88% and an average degree of polymerization of 1700. aqueous solution ioom
+(Contains 4.0.5g of 3Po) added concentrate,
A spinning dope containing 23% by weight of metal compounds based on oxide conversion was obtained. When this was stored in a sealed state at 25°C, the viscosity change and stringiness of the spinning dope were as shown in the following table = 1.The evaluation of stringability was Δ: insufficient, 0: good. ). Table 1 The stock solution aged for two weeks was extruded into air at a relative humidity of 36% through a 150-hole spinneret with a pore diameter of 100 μm to form a fiber, and the filament was coagulated while being stretched over about 2 m. Further, this was continuously wound up on a rotating drum while being dried with hot air at about 150°C. This precursor IIN was fired in air to 1200° C. to obtain silica-containing alumina continuous fibers. An X-ray diffraction pattern of this material showed that the fiber was composed primarily of gamma alumina. Ten strength measurement samples with a fiber length of 30 mm were prepared from this fiber, and the fiber diameter and tensile strength were measured, and the average diameter was 6.1 μm and the average tensile strength was 17 t/Cm 2 . Example 2 PA containing 75% basicity and 11.1% by weight A1
75 g of the colloidal silica used in Example 1 was added to 4.05 g of C4.05 and 300 g of the PVA aqueous solution, and further added with H
An aqueous solution of 804,0,6SF dissolved in 100 ml of water was added, and the total amount was concentrated to 435 g. The viscosity after 3 hours was 848 poise at 25°C. The viscosity of the stock solution after aging for 4 days was 1240 poise. This stock solution was spun and fired in the same manner as in Example 1 to obtain silica-alumina continuous filaments having an average diameter of 7.0 microns and an average tensile strength of 14 t/Cl112. [Actual] In U free gift Example 2, instead of +2so/I, HPOl,
A spinning stock solution was obtained in the same manner except that 0!7 was used. Viscosity after 3 hours is 1170 at 25℃
However, after 24 hours, it became 1390 voids, indicating excellent stringiness. This was spun in the same manner as in Example 1,
After firing, the average diameter is 6.8H1m, and the average tensile strength is 16t.
/Cl112 silica alumina continuous length #JA fiber was obtained. Comparative Example A spinning stock solution was obtained in the same manner as in Example 2 except that I'2S04 was not added. The viscosity was 690 voices at 25°C. When this was aged for 5 days, the viscosity was 710.
There was only a slight increase in viscosity. When spinning was carried out in the same manner as in Example 1, the filaments were frequently broken and continuous spinning could not be performed. 1-I N instead of "2S04 in Example 2"
A spinning stock solution was similarly obtained by adding 1.0 g of O3. 25
The viscosity at °C was 677 boids. The viscosity after aging for 5 days was 682 boids, showing only slight thickening. The results of spinning were similar to those without additives, and continuous spinning was not possible. Example 4 381 g of PAC same as Example 2 and colloidal silica 9
After thoroughly mixing 8 g of PVA aqueous solution with 300 g of the same PVA aqueous solution as in Example 1, 6.5 g of aluminum sulfate aqueous solution (A
I 2 (804,)3 (containing 2.0 g) was added and the total amount was concentrated to 65C1. The viscosity after 3 hours was 429 voices at 20°C. After aging for 20'Cr2/hour, the viscosity increased to 558 voids. This was spun and fired in the same manner as in Example 1, and the average diameter was 6.0.
Silica-alumina continuous fibers with an average tensile strength of 13 j/7 μm were obtained. A similar composition was used in Example 4 except that aluminum sulfate was replaced with sodium sulfate (Na2SO4, 2.0 g), and the same composition was concentrated to 637 g to obtain a viscous liquid with 309 voids at 20 DEG C. When aged at 20°C for 48 hours = 23 -, the viscosity increased to 416 poise. This was spun and fired in the same manner as in Example 1 to obtain a continuous length of silica-alumina with an average diameter of 5.7 μm and an average tensile strength of 13 t/cat.
! I got the navy blue. Example 6 40 g of zirconium oxychloride (ZroCI.8Ho) was dissolved in the same PAC4779 as in Example 4, and the same PVA aqueous solution 3009 as in Example 1 was added and mixed. Furthermore, 100ml of H2SO4 aqueous solution (H2S
04.04.1.0g) was added and the total amount was concentrated to 610g to obtain a viscous liquid of 170 poise at 20°C. Initially, the stringability of this liquid was insufficient, but after 48 hours, the viscosity increased to 293 voids and it began to show good stringability. This was spun in air at a relative humidity of 29% in the same manner as in Example 1, and fired in air at a temperature of 1000°C.
Alumina-zirconia continuous long fibers with excellent flexibility of μm were obtained.

Claims (1)

[Scope of Claims] 1. A dry spinning method in which an aqueous composition containing a water-soluble metal compound that provides a desired metal oxide upon firing or a water-dispersible metal oxide, and polyvinyl alcohol is concentrated to a desired concentration. A method for producing metal oxide fibers, which comprises forming precursor fibers by calcination, and adding a water-soluble inorganic polybasic acid and/or a salt of the inorganic polybasic acid to the aqueous composition. 1. A method for producing metal oxide fibers, the method comprising: concentrating the aqueous composition, aging the aqueous composition to increase the apparent viscosity of the aqueous composition by at least 10%, and then spinning the aqueous composition. 2. The method according to claim 1, wherein the content of polyvinyl alcohol is 10 parts by weight or more based on 100 parts by weight of the corresponding oxide of the water-soluble metal compound. 3. Polyvinyl alcohol contains 2 mol% of residual organic acid groups.
Claims 1 to 2 are partially saponified products having the above
The method according to any one of Item 2. 4. Claim 1, wherein the water-soluble metal compound is mainly composed of polyaluminum chloride represented by the formula [Al_2(OH)_nCl_6_-_n)_m (where 3≦n≦5, m≦10) The method according to any one of items 1 to 3. 5. Claims 1 to 4, wherein the water-soluble inorganic polybasic acid or the salt of the inorganic polybasic acid produces polyvalent anions consisting of sulfur and/or phosphorus oxides in an aqueous solution. The method described in any one of paragraphs. 6. The method according to claim 5, wherein the water-soluble inorganic polybasic acid or the salt of an inorganic polybasic acid is sulfuric acid and/or phosphoric acid or a salt thereof. 7. The content of the water-soluble inorganic polybasic acid or the salt of the inorganic polybasic acid is 0.1 to 10 parts by weight based on 100 parts by weight of the corresponding oxide of the water-soluble metal compound. The method according to any one of items 1 to 6. 8. The method according to any one of claims 1 to 7, wherein the aging is performed in a non-evaporating atmosphere of the aqueous composition at 40°C or lower for 12 hours or more.