JPS6050728B2 - Production method of alkali metal titanate fiber - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a novel method for producing alkali metal titanate fibers.

Typical inorganic fibers that have been used in the past include asbestos and glass fiber, but both of these have 500'
It cannot withstand long-term use under high temperature conditions of C or higher.

On the other hand, alkali metal titanate fibers are inorganic fibers that have a heat resistance of 100°C or higher, low thermal conductivity, excellent heat insulation properties, and excellent chemical stability. It is used as a material in various fields. Various methods have been proposed for producing such alkali metal titanate fibers, but they can generally be divided into hydrothermal synthesis methods, flux methods, and calcination methods.

As a hydrothermal synthesis method, for example, an aqueous solution containing an alkali metal is added to titanium oxide or titanium hydroxide, and the
and 2 (4) atmospheres or more (see US Pat. No. 2,833,622), melting and solidifying a mixture containing titanium oxide and alkali metal oxides (oxides of potassium, sodium, rubidium, cesium, etc.) There is a method in which a substance is added to water and subjected to a hydrothermal reaction at 350° C. or higher and 1 concave pressure or higher (see US Pat. No. 39520(4) and JP-A-51-49924). As a fluxing agent method, a method is generally known in which an alkali metal halide such as potassium chloride or potassium fluoride is added to a mixture of titanium oxide and calcium carbonate as a fluxing agent, but potassium molybdate or potassium tungstate is also used as a fluxing agent. A method of using it as a fluxing agent has also been proposed (U.S. Pat.
(Refer to the issue publication). As a firing method, a method is known in which an oxygen-containing titanium compound and an oxygen-containing alkali metal compound are mixed, molded, and fired at 200 to 1150°C, but in order to obtain a product with a long fiber length, a flux and a It is said that it is preferable to coexist with an alkali metal halide (U.S. Pat. No. 3,328,117 and Japanese Patent Publication No. 42
(Refer to Publication No.-27264). Also known is a method of firing titanium oxide and alkali metal salts in a sulfate melt (U.S. Pat. No. 3,760,068 and Japanese Patent Laid-Open No.
6-4370). The three methods for producing alkali metal titanate fibers described above all involve growing fibers using a liquid as a medium.

In other words, in the hydrothermal synthesis method, an aqueous solution is the medium;
In the flux method, fluxes such as alkali metal halides and alkalis are used. A molten liquid such as a metal tungstate or molybdate is the medium. Also, in the firing method, in order to obtain the desired fiber length, it is necessary to use an alkali metal halide such as potassium chloride as a fluxing agent. is used as a medium. However, these manufacturing methods in which fibers are grown using liquid media have the following problems.

In other words, hydrothermal synthesis requires the use of expensive and dangerous high-pressure generators and high-pressure reaction vessels, and is not only complicated to operate and difficult to produce continuously, but also produces products with a wide range of compositions. The disadvantage is that it is difficult to produce products of uniform length. Due to the use of potassium chloride or potassium fluoride as a flux in the flux method, a large amount of harmful and corrosive gas containing chlorine and fluorine is generated, and a large amount of potassium chloride, etc. sublimates. In addition to requiring equipment to remove these gases, it is also necessary to use expensive corrosion-resistant materials in the manufacturing equipment.Furthermore, there is a problem in treating the waste liquid produced during the defibration and washing processes, which requires expensive waste liquid disposal equipment. There is a problem in that the manufacturing and manufacturing equipment is expensive.

Furthermore, using a large amount of flux or using expensive potassium molybdate or potassium tungstate as a flux increases costs, and therefore a flux recovery device is required, which increases equipment costs. As a result, higher costs cannot be avoided. Furthermore, the flux method has the disadvantage of low homogeneity of quality, such as large variations in fiber length. The sintering method is considered to be an industrially advantageous method.
Although there have been examples of this being carried out on a large scale in the United States in the past, the calcination method generally has the disadvantage that fibers with longer lengths cannot be obtained than other methods.

Although this drawback has been overcome to some extent in the firing method that uses the alkali metal halide as a flux,
This method still uses alkali metal oxides such as potassium chloride, so a large amount of toxic and corrosive gas is generated as in the flux method, and a large amount of potassium chloride etc. sublimates. Therefore, it is necessary to use an expensive non-corrosive material for the manufacturing equipment, and a device for removing the gas is also required.Furthermore, expensive wastewater treatment equipment is required, making the equipment expensive. There is a problem. In addition, the method of firing in a molten sulfate has problems with quality homogeneity, such as large variations in fiber length, and problems with sulfate separation, recovery, and drainage treatment, which makes it unsuitable. This is not a good method. In view of the above points, the inventors of the present invention have conducted intensive studies to find an industrially advantageous manufacturing method for alkali metal titanate fibers. They discovered an extremely superior method in terms of equipment and other aspects.

That is, the present invention provides, when producing an alkali metal titanate fiber having a composition represented by the general formula M2O(TiO2)n (wherein M is an alkali gold metal and n is 2 to 12),
(4) Titanium oxide, (B) an alkali metal carbonate, and (C) a compound that separates, vaporizes, or burns at 500°C or below (hereinafter referred to as a cavitation agent), and is obtained by mixing one or more of them. The alkali metal titanate fiber is characterized in that the mixture is heated to 100 to 500'C to decompose, vaporize or burn the cavitation agent to form cavities in the mixture, and then heated and fired at 600 to 1200C. Concerning the manufacturing method.

In the manufacturing method of the present invention, when heating and firing (600 to 1200°C) component (4) and (B) component, the cavitation agent decomposes, vaporizes, or burns at 500°C or lower and is generated in the mixture. It is presumed that alkali metal titanate fibers grow in the cavities, and this is a completely different manufacturing method from conventional methods in which fibers are grown using a liquid as a medium. The titanium oxide which is the component (4) used in the present invention may be either anatase type titanium dioxide or rutile type titanium dioxide.

Examples of the alkali metal carbonate as component (B) include carbonates of sodium, potassium, rubidium, cesium, and the like.

Examples of the cavitation agent (C) include alcohols, sugars, grains, celluloses, and urea derivatives.

Examples of alcohols include methanol, ethanol, amyl alcohol, allyl alcohol, probagyl alcohol, ethylene glycol, propylene glycol, erythrol, 2-butene-1,4-diol, glycerin, pentaerythritol, arabite, sorbitol, peptides, Examples include polyethylene glycol, polypropylene glycol, polyglycerin, and polyhydric alcohols such as ethylene glycol, erythrol, glycerin, pentaerythritol, sorbitol, polyethylene glycol, polypropylene glycol, and polyglycerin are particularly preferred.

Examples of sugars include erythrose, ribose, xylose, allose, glucose, galactose, abiose, maltose, lactose, sucrose, manninotriose, cellotriose, cellotetrose, stachyose, starch, dextrin, etc. Among them, xylose and glucose , galactose, sucrose, starch and dextrin are preferred.

Examples of starch include corn starch and potato starch. Examples of grains include wheat flour, rice flour, rice flour, and rice bran, and wheat flour is particularly preferred.

Examples of cellulose include methylcellulose, viscose, lignin, lactone, vanillin, xylan,
Examples include mannan, wood flour, bulb powder, and natural fiber powder, with wood flour, bulb powder, and natural fiber powder being particularly preferred.

Examples of the natural fiber powder include momen thread powder. Examples of urea derivatives include urea, biuret, urazol, cyanuric acid, uracil, methylurea, butylurea, acetylurea, oxalate urea, thiourea, semicarbazide, guanidine carbonate, aminoguanidine, nitroguanidine, biurea, azodicarbonamide, barium azo Among them, urea, biurea, semicarbazide, guanidine carbonate, aminoguanidine, azodicarbonamide and the like are preferred. It is also possible to add water in addition to the above, but water does not act as a cavitation agent and the mixture cannot be made into a spongy form.

However, by using it in combination with other cavitation agents, it is possible to promote uniform dispersion of the cavitation agent, so there is no hindrance to adding it in addition to the cavitation agent. The above (4) component and (
The blending ratio of component B) is preferably 1:0.3-17 (weight ratio), and the blending ratio of the cavitation agent is 0.5-40% ( % by weight (hereinafter the same), preferably 1 to 20%.

As for the form in which it is heated, it may be heated while it is in a container, or it may be heated in a molded form.

The temperature required to form cavities in the mixture obtained by mixing component (4), component (B), and cavitation agent is:
This is the temperature at which the cavitation agent can be decomposed, vaporized, or burned, and although it varies depending on the type of cavitation agent, 100 to 500°C is sufficient.

As a matter of course, it is necessary to select a cavitation agent that is safe to handle, has little odor, does not contain heavy metals, and does not emit harmful gases when heated.

The mixture in which the cavities have been formed is then heated continuously or stepwise to the firing temperature.

The heating and firing temperature varies depending on the melting temperature of component (B), but 600 to 1200°C is sufficient. One preferred embodiment of the heating operation is to heat the mixture of component (4), component (B) and cavitation agent at a heating rate of, for example, about 200° C./hour to form cavities in the mixture; 800
After heating and firing at ~1100°C, approximately 200'
An example is a method of cooling at C/hour.

In this case, the firing time may be approximately 3 to 6 hours. The fired body thus obtained is a lump of alkali metal titanate fibers.

The higher the porosity of this lump, the easier the subsequent defibration treatment will be, but a porosity of about 10 to 80% is usually sufficient. Defibration treatment can be easily carried out underwater,
It is also easy to isolate. Next, steps when the method of the present invention is scaled up will be explained in order.

First, regarding the step of mixing the raw materials, titanium oxide, alkali metal carbonate, and cavitation agent can be mixed sufficiently uniformly using a normal mixer, and there is no need to take particular precautions.

Next, for the heating and firing process, electric heating is performed. Both heat and combustion heating using heavy oil, liquefied petroleum gas, city gas, etc. are used.

The heating device is preferably one with a mechanism that allows the temperature increase rate and firing holding time to be freely controlled. Since the method of the present invention does not use a flux, sublimation of the flux is avoided! There is no need for a special furnace or exhaust gas treatment equipment that takes measures against corrosive gases, and heating and firing can be carried out in a commonly used tunnel furnace that can continuously supply raw materials. The raw material mixture may be supplied to the tunnel furnace by placing the mixture in a container such as a high-purity aluminium crucible, but this method requires extra thermal energy to heat the container, and the mixture is This is not a very preferred method because it is difficult to heat the mixture uniformly, and it is preferable to feed the mixture directly to the tunnel furnace without putting it in a container.

For a long time, the manufacturing of bricks, roof tiles, ceramics, etc. has been carried out by placing pre-formed materials on a tray or cart and continuously feeding them.The method of the present invention also takes uniform heating into consideration. It is preferable to supply a molded mixture to the extent that it does not lose its shape, and then heat and bake it. In addition, in the firing method that uses a flux together, it is difficult to manufacture by the method using the molded body.

This is because the flux remains in a molten state even after heating and firing, but when it solidifies, the fired body sticks to the tray or cart, making it difficult to take out the fired body and reducing workability. At the same time, the flux sublimes during heating and firing, but after a long period of operation, the flux adhering to the tunnel furnace wall may swell up and come into contact with trays or carts, causing problems such as This is because the exhaust fan and air circulation holes for control become clogged, making it difficult to control the temperature. However, in the method of the present invention in which a cavitation agent is added, the fired bodies do not stick to the tray or cart as described above, and not only can the fired bodies be easily taken out, but also the fired bodies do not stick to each other. Since this does not occur, it is possible to supply molded raw materials in a stacked manner, thereby minimizing heat loss in the tunnel, which is excellent in terms of both workability and productivity. The raw material mixture supplied into the tunnel is continuously heated to 100 to 500°C, and the cavitation agent decomposes, vaporizes, or burns to form countless cavities, which are then heated and fired at 600 to 1200°C. It becomes a lump of alkali metal titanate fiber.

Next, talking about the defibration process, in the conventional firing method, special equipment was required or it took a long time to defibrate the obtained fired body, but in the method of the present invention, The obtained fired body immediately absorbs water and crumbles easily, making it extremely easy to defibrate.

As mentioned above, the reason for this is thought to be that countless cavities are formed in the fired body, giving it a spongy shape.
Next, the effects of the manufacturing method of the present invention will be described in comparison with conventional methods, especially fired products using a flux.

(1) Alkali metal titanate fibers with long fiber length can be obtained.

When a fired product using a conventional fluxing agent is used, it is possible to obtain a product with an average fiber length of about 10 to 20 μm at most, but when using the manufacturing method of the present invention, a product with an average fiber length of up to 150 μm can be obtained.

This is thought to be because the fibers can grow freely in the countless cavities formed in the mixture. (2) The heating and firing temperature can be lowered, and the firing time can be shortened, resulting in energy savings.

Although the reason for this is not certain, it is thought that the combustion of the cavitation agent causes a rapid temperature rise of the mixture during firing and provides a uniform heating rate. (3) Uniform fiber length can be achieved and yield can be increased.

As shown in (2) above, the temperature of the mixture increases rapidly during firing, and at the same time a uniform heating rate is obtained, thereby making it possible to obtain fibers with uniform fiber length.

When using conventional firing methods that use fluxing agents, it is thought that the mixture is not heated uniformly during heating and firing, for example, the heating rate differs between the surface and the inside, resulting in non-uniform fiber length. It will be done. The longer the fiber length of the alkali metal titanate fiber obtained by the production method of the present invention, the thicker the fiber diameter tends to be.
~3.0μ and lengths ranging from 10 to 500μ, of uniform quality.

Furthermore, when the production method of the present invention is used, the theoretical yield reaches as high as 98%, which is a significant improvement over the 65% obtained using the conventional calcination method using potassium chloride as a fluxing agent.

(4) Poisonous gases and toxic sublimates are generated, and the waste liquid produced during the fibrillation process can be easily disposed of.

As mentioned above, when an alkali metal halide is used as a flux, a large amount of halogen gas, hydrogen halide gas, and sublimate are released, but since these are all highly corrosive, it is difficult to use the material of the reactor at high temperatures. It is difficult to select
In addition, expensive exhaust gas treatment equipment is required.

In addition, a large amount of water is used to separate the alkali metal titanate fibers in the fibrillation process, and it is necessary to remove by-product acids and fluxes, and this waste liquid is discharged outside the factory untreated. This is undesirable and requires drainage treatment.
On the other hand, in the present invention, the blended cavitation agent burns during heating and firing, so the gases generated are only water vapor and carbon dioxide, and the waste liquid from the defibration process does not contain particularly harmful substances. Since it does not contain any pollutants, there is no need for special equipment to treat exhaust gas or waste liquid, which can reduce equipment costs.

]) The obtained alkali metal titanate fiber agglomerates can be easily defibrated.

The defibration operation of a fiber mass consists of pouring it into an appropriate amount of water, stirring after soaking, and separating the defibrated fibers by repeating decantation using a trowel, but a flux is used. The fired body produced by this firing method is dense and extremely hard.
Therefore, it is difficult to defibrate using normal defibration processing methods that use water, and a special defibration processing method must be adopted.
This has the disadvantage that the fibers are cut during defibration, resulting in a shortened fiber length, further promoting non-uniformity of the fiber length.

On the other hand, the fiber aggregate obtained in the present invention has countless cavities formed by the hollowing agent, and the aggregate itself is expanded, so it has a spongy shape that is convenient for defibration. It is very easy to defibrate simply by adding it to water.

Therefore, a special defibration process is required, and the fiber length does not become nonuniform during the defibration process, and the effect is that alkali metal titanate fibers with uniform long fibers can be obtained at a high yield. It is played. As described above, the manufacturing method of the present invention is completely different from the conventional method of growing fibers using a liquid as a medium, and instead grows fibers using a cavity created by decomposition, vaporization, or combustion of a cavitation agent as a medium. Moreover, it is an extremely industrially superior manufacturing method for alkali metal titanate fibers that achieves homogenization of quality, reduction of equipment costs, and does not generate toxic gases.

Next, the present invention will be explained in detail with reference to Examples and Comparative Examples.

! ζ Examples 1 to 11 and Comparative Examples 1 to 2 30 da of anatase-type titanium oxide as a captive ingredient and 15 y of potassium carbonate as a component (B) were placed in a mortar, and 5 y of the additives shown in Table 1 were added thereto. Mix well with a pestle.

The obtained sample was placed in a high-purity alumina crucible with a capacity of 100 m1, and placed in an electric furnace (furnace chamber width: 2507177 mm, height: 2 mm).
After heating and firing in a 50Tf0n1 depth 50'' under the conditions of a temperature increase rate of 200° C./hour, a holding temperature of 970° C., and a holding time of 3 hours, it was cooled at a temperature decreasing rate of 200° C./hour. The heated and calcined sample was placed in 500 mt of water in a beaker and heated for 10 minutes.
After being immersed for a minute, the mixture was stirred at 200 rpm for 20 minutes, and then separated into fibrous parts and aggregates by decantation. The aggregate was again stirred and fractionated in 500 mL of fresh water in the same manner as above. Collect the 3 parts of the fibrous material and pass it through suction.
Potassium titanate fibers were obtained by drying at 50°C for 3 hours. Table 1 shows the yield and average fiber length of the potassium titanate fibers obtained.

The average fiber length was calculated from the QL value obtained using Luzex Model 5 (4) manufactured by Nippon Regulator Co., Ltd.

The Luzex Model 5 (4) is a system that projects a sample set on a microscope onto a television, observes the image, and measures it. In Table 1, PEG represents polyethylene glycol, and the numbers following it are average molecular weights.

From Table 1, when PEG is added (Examples 1 to 11)
) is when potassium chloride or water is added (Comparative Example 1)
It can be seen that the fiber yield is better and the fiber length is significantly longer than those of 2).

Differences in the yield of defibrated fibers indicate to some extent the difficulty of defibration. Of course, the difficulty in defibrating is also related to the fiber length, and the longer the fiber length, the easier it is to defibrate. Comparative example 1~
Since it was difficult to stir and defibrate the fired body obtained in step 2 in a heater as it was, it was crushed into stirrable chunks and stirred and defibrated. Examples 12-21 Anatase titanium oxide 50y and potassium carbonate 25
Add PEGlOOOO or wood flour to y in the amount shown in Table 2,
Mix well in a mortar.

The obtained sample was filled into a cylindrical mold having an inner diameter of 60 WrIn1 and a height of 4 h, and was molded under a press pressure of 100 kg Icd to produce a disc-shaped molded product with a diameter of about 60 Tr$11 and a thickness of about 2 mm. This molded article was heated, fired and defibrated in the same manner as in Example 1 to obtain potassium titanate fibers. The results are shown in Table 2. Examples 22-40 and Comparative Examples 3-7 Potassium titanate fibers were obtained in the same manner as in Example 12, except that 5y of the additives shown in Table 3 were used.

Examples 41-60 Potassium titanate fibers were obtained in the same manner as in Example 1, except that the types and amounts of additives and the firing temperature and time were changed as shown in Table 4.

The results are shown in Table 4. In Table 4, -*HS-5
00N is polypropylene glycol with an average molecular weight of 500, DlOL, -2000 is polypropylene glycol with an average molecular weight of 2000, and f-3050 is polypropylene glycol with an average molecular weight of 30.
00 polypropylene glycol, both manufactured by Mitsui Nisso Urethane Co., Ltd. Example 61 Anatase type titanium oxide 500k9, potassium carbonate 25k9 and PEG4OOO 6k9 were mixed in a super mixer ~ Srl
V4B2OO type [manufactured by Kawada Seisakusho Co., Ltd.] and 40
Mixed for 3 minutes at 0 rpm.

The temperature of the powder reached 75°C, and PEG4OOO melted and became liquid, resulting in a homogeneous mixture. The mixture was molded into 9k9 pieces using a vertical automatic press molding machine at a press pressure of 100k91d (gauge pressure) to an outer diameter of 200 m. n1 inner diameter 100m
A cylindrical molded body with a height of m1 and a mark of 1 was produced. 500T
! Anti-spall D on the trolley in the order of UrL x 1000
(made of high-purity alumina) tray (size 240TmIn
x45-) 4 sheets, and on top of that, 2 rows per cart x
A total of 32 molded bodies were stacked in 4 rows and 2 tiers (total weight 28
8k9) Stacked and lined up.

The carts loaded with the molded bodies in this manner were automatically fed one after another into a micro kiln (manufactured by Takasago Kogyo Co., Ltd.) at a rate of 7 pieces per cart. The micro kiln used has a total length of 14 rn, accommodates 14 carts, and is divided into a preheating zone, a firing zone, and a cooling zone, and is designed to automatically control temperature using a liquefied petroleum gas burner combustion method. The molded body was heated and fired in the firing zone at 970°C for 4 hours and 40 minutes. The carts supplied to the micro kiln are discharged approximately 30 minutes after being supplied. The weight of the molded bodies discharged after heating and firing was 7.5k9 on average per piece, and the volume increased by 28.2%.

The discharged compacts were crushed by a simple crusher, transported by a packet conveyor, and continuously poured into 5Tr1 water to be stirred and defibrated. The slurry after defibration was sequentially sent to a storage tank by a pump. The slurry in the storage tank was sent to a classifier, classified, and then supplied to an automatic centrifuge. Aggregates that have not been defibrated by the classifier are classified and automatically returned to the stirring defibration process, but the amount thereof is only 1 to 2% of the total. The potassium titanate fibers separated by the centrifuge were quantitatively fed to a conventional rotary dryer and dried at 250°C.

The potassium titanate fiber thus obtained is K2O (Tl
O2)4 (has a composition of 0, average fiber length is 56.5μ
The average yield was 104.5 kg per truck, and the average yield was 98.8%.

The obtained potassium titanate fiber powder was analyzed by X-ray diffraction. Table 5 shows the results in comparison with the data (JCPDS powder diffraction data collection) of the standard product (4.potassium titanate standard). X-ray diffraction was performed by Rigaku Denki Co., Ltd.
It was obtained using Geigerflex RAD-11A model manufactured by Manufacturer. FIG. 1 also shows a microscopic photograph of the potassium titanate fibers obtained. The minimum spacing of the scale graduations shown laterally in the photograph represents 5μ.

[Brief explanation of the drawing]

FIG. 1 is a microscopic photograph of potassium titanate fibers obtained in Example 61 according to the present invention, and the minimum interval of the scale graduations shown in the horizontal direction in the photograph represents 5 μ.

Claims (1)

[Claims] 1. When producing an alkali metal titanate fiber having a composition represented by the general formula M_2O(TiO_2)n (wherein M is an alkali metal and n is 2 to 12), (A) titanium oxide , (B) alkali metal carbonate and (C) 500°C
One or two compounds that decompose, vaporize or burn:
The resulting mixture is heated to 100-500°C to decompose, vaporize or burn the component (C) to form cavities in the mixture, and then heated to 600-1200°C.
A method for producing alkali metal titanate fibers characterized by heating and firing at °C. 2 The component (C) is polyhydric alcohol, sugar, grains,
The manufacturing method according to claim 1, which is a cellulose or a urea derivative. 3. The method according to claim 2, wherein the polyhydric alcohol is ethylene glycol, erythrol, glycerin, pentaerythritol, sorbitol, polypropylene glycol or polyglycerin. 4 Claim 2 in which the saccharide is xylose, glucose, galactose, sucrose, starch or dextrin
Manufacturing method described in section. 5. The manufacturing method according to claim 2, wherein the grains are wheat flour, soybean flour, rice, or bran. 6. The manufacturing method according to claim 2, wherein the cellulose is wood flour, natural fiber powder, or pulp powder. 7 Urea derivatives include urea, biurea, semicarbazide,
3. The method according to claim 2, wherein guanidine carbonate, aminoguanidine or azodicarbonamide is used. 8. The manufacturing method according to claim 1 or 2, wherein the blending ratio of component (C) is 0.5 to 40% by weight based on the total amount of components (A), (B), and (C). 9. The manufacturing method according to claim 1, wherein the porosity after heating and firing is 10 to 80%.