JPS6159280B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing fibrous alkali metal titanates. More specifically, an alkali metal molybdate or alkali metal tungstate represented by the general formula M ₂ MoO ₄ or M ₂ WO ₄ (in the formula, M is an alkali metal, the same applies hereinafter) is used as a catalyst,
In addition, production of an alkali metal titanate that can form a composition corresponding to an alkali metal titanate represented by the general formula M ₂ O・nTiO ₂ (in the formula, M is an alkali metal, and n is 1 to 7, the same applies hereinafter) Blending raw materials or alkali metal titanates at a ratio of 70 to 95 mol%,
The present invention relates to a method for producing a fibrous alkali metal titanate, which is characterized by heating and melting the fibrous alkali metal titanate in a temperature range of 900 to 1350°C to react and grow the fibrous alkali metal titanate in at least a molten solution of a catalyst. Conventionally, methods for producing fibrous alkali metal titanates include a flux method, a hydrothermal synthesis method, and a calcination method. Industrially, the flux method or the sintering method is considered advantageous in terms of large-scale production and continuous production. However, since the calcination method is based on a solid phase reaction, although it is a simple manufacturing method, it has the disadvantage that only short fibers with a short fiber length can be obtained. On the other hand, the flux method uses alkali metal halogen compounds such as potassium fluoride and potassium chloride for the flux, so its vapor pressure is extremely high, and therefore the reaction temperature cannot be maintained high.
Although fiber lengths larger than those of alkali metal titanate obtained by the above-mentioned calcination method can be produced, there are still many practical difficulties. The present inventors theoretically elucidated the production reaction of fibrous alkali metal titanates in the flux method. As a result, they used an alkali metal tungstate or an alkali metal molybdate as a flux, and the general formula M ₂ O was used for this flux.・
A raw material (i.e., titanium oxide and alkali metal compound) capable of forming a composition of alkali metal titanate represented by nTiO ₂ or its constituent components TiO ₂ and M ₂ O is blended in a range of 5 to 50 mol%, and 700 ~
By heating and melting the flux at a temperature of 1350°C and growing the alkali metal titanate produced in the flux melt, it is extremely pollution-free, the flux used can be recovered, and it can be made with a large fiber length. It has been discovered that fibrous alkali metal titanate can be produced continuously (Japanese Patent Application Laid-open No. 122700/1983).
(see publication). However, this manufacturing method has the following industrial problems. That is, the production method described above is as follows: (1) Since the growth reaction of fibrous alkali metal titanate is carried out in a large amount of flux melt, although the vapor pressure of the melt is low, the corrosivity of the reaction vessel is extremely high; In the case of industrial production, there is no suitable material for the container, and a new one must be developed. (3) When a large amount of flux is used, the reaction occurs rapidly at the start of the reaction, causing short fibers and long fibers to separate. (4) If there is a large amount of flux, a large amount of water is required to defibrate the fibrous alkali metal titanate, which is disadvantageous. . There are many difficult questions that need to be solved, such as: Therefore, the present inventors conducted further intensive research in order to eliminate the above-mentioned drawbacks and develop an industrial manufacturing method for fibrous alkali metal titanate. As a result, the following new fibrous alkali metal titanate was developed. We have discovered a growth reaction method and the catalytic effect of flux that promotes the reaction. That is, in the composition system forming alkali metal titanate (M ₂ O.nTiO ₂ ),
In order to produce an alkali metal tetratitanate (M ₂ O.4TiO ₂ ) phase which naturally becomes long fibers, an alkali metal hexatitanate (M ₂ O.4TiO 2 ) phase is first produced as an initial product.
6TiO ₂ ) phase is formed, and then this alkali metal hexatitanate and the M ₂ O component are subjected to an association reaction to form an alkali metal tetratitanate. This reaction mechanism is described in the above-mentioned JP-A-51-122700 The alkali metal titanate produced by the dissolution-precipitation reaction described in the publication (i.e., the solid-liquid interface reaction between titanium oxide in the solid phase and the alkali metal oxide in the liquid phase) dissolves in the flux melt, It was determined that this reaction was not a reaction of precipitation and growth, but a dissociation-association reaction shown by the following reaction formula. 2M ₂ Ti ₆ O ₁₃ +M ₂ O3M ₂ Ti ₄ O _9This dissociation-association reaction depends on the temperature, raw material composition, degree of basicity of the catalyst, etc. Generally, at high temperatures, the dissociation reaction is predominant; When a large amount of an acid alkali metal phase is produced and slow cooling is performed from a high temperature, an association reaction becomes dominant, and an alkali metal tetratitanate phase is produced to form long fibers. Therefore, since the purpose of using the flux is to have a catalytic effect to promote this reaction, fibrous alkali metal titanate can be obtained even if the amount of flux used is extremely small. The catalyst is also more active when used in the molten state. The present invention was completed based on many such findings. A first object of the present invention is to provide a method for producing fibrous alkali metal titanate using a non-polluting and recoverable flux and using conventional reaction vessel materials. A second object of the present invention is to provide a method for producing fibrous alkali metal titanates that does not require large-scale flux recovery equipment and is inexpensive to produce. Another object of the present invention is to provide a method for producing a long fibrous alkali metal titanate which is particularly useful as a heat-resistant, heat-insulating material and a plastic reinforcing material. That is, the present invention comprises a mixture of a titanium oxide component and an alkali metal compound capable of forming an alkali metal oxide component, and whose composition has the general formula M ₂ O.
A raw material for producing an alkali metal titanate formed by blending titanium oxide, which is a constituent component of an alkali metal titanate, and an alkali metal oxide represented by nTiO ₂ or the alkali metal titanate and a catalyst of the general formula M ₂ Alkali metal molybdate represented by MoO ₄ or alkali metal tungstate represented by the general formula M ₂ WO ₄ in mol%.
Mix at a ratio of 70:30 to 95:5 and at a temperature of 900 to 1350.
heating and melting the reaction system at °C or at least melting the catalyst component, and growing the alkali metal titanate as a single crystal through a dissociation-association reaction between the alkali metal titanate and alkali metal ions produced in the molten mixture. By employing this method, the above-mentioned drawbacks can be eliminated and the object of the present invention can be achieved, which is a very remarkable effect. Specifically, the method of the present invention is made of a mixture of titanium oxide (i.e., TiO ₂ ) and an alkali metal compound capable of forming an alkali metal oxide (i.e., M ₂ O), and whose composition ratio is common. A raw material for producing an alkali metal titanate, or the alkali metal titanate and a _catalyst , which are blended to have a constituent composition of titanium oxide and alkali metal oxide, which are the constituent components of the alkali metal titanate represented by the _formula M 2 O.nTiO 2 The mixture is mixed with an alkali metal molybdate or an alkali metal tungstate in a ratio of 70:30 to 95:5 (mol%), and the mixture is heated at a melting temperature of 900 to 1350°C, preferably 1000 to 1350°C, for 1 to 10 hours, preferably. This is carried out by heating the reaction system for 3 to 5 hours or melting at least the catalyst component, and then carrying out a dissociation-association reaction between the alkali metal titanate and alkali metal ions produced in the molten mixture. The means for carrying out the dissociation-association reaction between the alkali metal titanate and the alkali metal ions include, for example, a method of holding the molten mixture at a temperature within the range of the melting temperature for usually 3 to 5 hours, or a method of holding the molten mixture at a certain temperature within the range of the melting temperature, or Methods of slow cooling from temperature to around 900℃ (e.g. at a slow cooling rate of 4 to 20℃/hr), evaporation method, method of locally cooling a part of the melt, and methods of cooling the melt at the top and bottom of the melt. A method of giving or a method of combining these methods is adopted, whereby the desired type of alkali metal titanate is produced as a single crystal and made into long fibers. Increasing the melting temperature higher than 1350°C is thermally uneconomical, and it is also difficult to select the material for the reaction vessel.
General formula _M2 as a catalyst when lower than 900℃
The alkali metal molybdate represented by MoO ₄ or the alkali metal tungstate represented by the general formula M ₂ WO ₄ does not melt or is in an insufficient molten state, making it difficult for dissociation-association reactions to occur and only extremely short fibers can be obtained. , and the yield of fibrous alkali metal titanate is extremely reduced, both of which are unfavorable. In the present invention, as described above, the raw material for producing alkali metal titanate or the alkali metal titanate and the catalyst (i.e., flux) are mixed in a mole% range of 70 to 95% of the former and 30 to 5% of the latter. As a result, conventional container materials can be used, and expensive flux can be recovered using relatively small-scale equipment, making it possible to use industrial alkali metal titanates with large fiber lengths. A very remarkable effect can be achieved in that manufacturing is possible. The amount of catalyst added is 30 mol%
If it is made larger than 5 mol%, the reaction will occur rapidly at the start of the reaction, and problems such as the phenomenon of short fibers and long fibers mixed together will occur, and if it is made smaller than 5 mol%, The dissociation-association reaction becomes difficult to occur, which affects the fiber length and yield of potassium titanate, both of which are unfavorable. The general formula M ₂ MoO ₄ or M ₂ used in the present invention
Examples of the alkali metal molybdate or alkali metal tungstate represented by WO ₄ include alkali metal molybdates or alkali metal tungstates in which the alkali metal is sodium, potassium, rubidium or cesium. The fibrous alkali metal titanate produced by the method of the present invention has a general formula M ₂ O.nTiO ₂ in which the alkali metal (i.e. M) is sodium, potassium, rubidium or cesium, and n is 1 to 7 (preferably 2 to 6), which has a cylindrical shape with a diameter of 0.1 to 10μ and a fiber length of about 0.01 to 5 mm, and is an industrially usable heat insulating material.
It can be effectively used as a refractory material, a carrier for pigments and catalysts, a plastic filler, a cement composite, etc. In the present invention, the ratio of titanium oxide, which is a component of the fibrous alkali metal titanate, and the alkali metal compound capable of forming an alkali metal oxide is determined according to the composition ratio of the target type of alkali metal titanate. This is because the stability in the production of alkali metal titanates is significantly affected by the basicity in the melt.
For example, if titanium oxide is in excess or if the alkali metal compound is in excess, the fiber length of the product will be markedly reduced, which is undesirable. As the alkali metal compound used in the present invention,
For example, the alkali metals are sodium, potassium,
Examples include carbonates, hydroxides, and nitrates of rubidium or cesium, and one or more of these may be used. On the other hand, the alkali metal titanate used as a raw material for producing the fibrous alkali metal titanate is an amorphous or crystalline powder non-fibrous material that has the same composition as the alkali metal titanate to be produced. By the method of the invention, a fibrous alkali metal titanate having a large fiber length is formed. The heating and melting of the catalyst (i.e., flux) and the powdered non-fibrous alkali metal titanate is naturally determined by setting the upper limit to the melting temperature or decomposition temperature of the fibrous alkali metal titanate to be produced and the lower limit to the melting temperature of the catalyst. As mentioned above, the temperature at which fibrous alkali metal hexatitanate is generated is also important. Therefore, its preferred temperature is 900-1350
℃ range, the catalyst is in a molten state, and the molten mixture is maintained at a certain temperature within the above temperature range for a certain period of time or is slowly cooled to a specified temperature. When implementing the method of the present invention industrially,
A specific composition of a catalyst and an alkali metal titanate production raw material or powdered non-fibrous alkali metal titanate is rapidly heated to a predetermined temperature (for example, 1150°C), and then kept at that temperature for a certain period of time (for example, 4 hours). ) It is easy to adopt the holding method, and it is possible to control the fiber length of the fibrous alkali metal titanate produced by appropriately changing the holding temperature. However, it has been difficult to scale up this type of synthetic reaction, but by employing the method of the present invention, it has become easy to scale up and industrialization has become possible. Next, the method of the present invention will be specifically explained with reference to Examples and Reference Examples, but the present invention is not limited only to these Examples. Reference example 1 This reference example has the reaction formula: 2K ₂ Ti ₆ O ₁₃ +K ₂ O
The purpose of this study was to demonstrate the dissociation-association reaction according to 3K ₂ Ti ₄ O ₉ and to investigate the temperature dependence of the reaction. As potassium titanate with the desired composition, K ₂ O.
To produce 4TiO ₂ , TiO ₂ (rutile type, 325 mesh pass) and K ₂ CO ₃ (325 mesh pass) were mixed at a molar ratio of 4:1, and then this and K ₂ MoO ₄ as a catalyst were mixed. They were blended at a ratio of 90:10 (mol%) and thoroughly shaken to mix. Approximately 1 g of this mixture was filled into 7 ml platinum crucibles and heated and melted using a silicon carbide heating element electric furnace (5 kW). At this time, the reaction temperature is
950℃, 1000℃, 1050℃ and 1100℃, and the reaction time was 5 minutes, 15 minutes for each reaction temperature.
minutes, 30 minutes, 60 minutes and 240 minutes, respectively. The crucible containing the melt treated under the predetermined melting conditions was then taken out into the atmosphere and rapidly cooled on a cloth containing cold water. The rapidly cooled sample was then removed from the crucible by dissolving the catalyst with water, washed with water, dried, and the product was identified by powder X-ray diffraction. Both products are K ₂ O.
It is a fibrous material of phases of 4TiO ₂ and K ₂ O・6TiO ₂ ,
The mixing ratio was determined by the relative intensity ratio of the strongest line. Although both phases are different phases, they exhibit the same crystal system and fiber shape extending in the coaxial direction and have the same crystal habit, so the relative strength method can be applied. The results are shown in Table 1 (temperature dependence of dissociation-association reaction).

[Table] The yield of the sample heated at 950° C. for 5 minutes and rapidly cooled was about 95% (weight %, the same applies hereinafter). When observed under a microscope, this material was in the form of fibers, and as shown in Table 1, it was found that approximately 65% of the material was composed of K ₂ O.4TiO ₂ phase and approximately 35% was K ₂ O.6TiO ₂ phase. . In such a production reaction with a small amount of K ₂ MoO ₄ and an extremely short time, the production mechanism of alkali metal titanate cannot be explained by a dissolution-precipitation reaction due to a solvent effect. This can be well explained by the dissociation-association reaction that occurs in the solid-liquid interface reaction system. Next, regarding the relationship between the synthesis phase and reaction temperature, the lower the temperature, the more stable the K ₂ O.4TiO ₂ phase is, and the higher the temperature, the more stable the K _{2 O.}
O.6TiO ₂ phase is stable. Particularly at low temperatures, potassium hexatitanate and K ₂ O
The association reaction with This means that K ₂ at high temperatures
This shows that an O.6TiO ₂ phase is formed, and when the melt is slowly cooled to a low temperature, a K ₂ O.4TiO ₂ phase is predominantly formed due to an association reaction. The alkali metal tetratitanate phase produced by the association reaction at a constant temperature is generally short fibers with a fiber length of about 10 to 100μ, especially about 10 to 50μ. Reference Example 2 In this reference example, the formation of long fibers from potassium tetratitanate (K ₂ O.4TiO ₂ ) was studied based on the knowledge of the temperature dependence of the dissociation-association reaction in Reference Example 1. TiO ₂ (rutile type, 325 mesh pass) and K ₂ CO ₃ (325 mesh pass) were mixed in a molar ratio of 4:1 to produce K ₂ O・4TiO ₂ as potassium titanate.
and then mix this with K ₂ as a catalyst.
MoO ₄ was blended in a ratio of 90:10 (mol%) and mixed by shaking well. Approximately 25 g of this mixture was filled into a 50 ml platinum crucible and heated and melted using a silicon carbide heating element electric furnace (5 kW). At this time, the reaction temperature was 1150°C and the reaction time was 4 hours. The crucible containing the melt treated under the above conditions was then taken out into the atmosphere and rapidly cooled on a cloth containing cold water. This sample was taken out from the crucible after dissolving and removing the catalyst with water, washed with water and dried, and the product (referred to as product A) was identified by powder X-ray diffraction. On the other hand, approximately 25 g of the above mixture was placed in a 50 ml platinum crucible and melted in the same manner as above, followed by cooling at a cooling rate of 4°C/hr to 1100°C (12.5 hours slow cooling time) and 1050°C (25 hours slow cooling time). ), respectively, to 1000°C (slow cooling time: 37.5 hours) or 950°C (slow cooling time: 50 hours) to obtain products (referred to as products B, C, D and E, respectively) in the same manner as above. . The product obtained was identified as described above.
The results are shown in Table 2 (relationship between association reaction and fiber growth during slow cooling process).

[Table] As is clear from Table 2, under high temperature conditions, a potassium hexatitanate phase is first formed, and when the association reaction is promoted by slow cooling and a potassium tetratitanate phase is formed, long fibers are formed. When the temperature is kept at 1150°C for 4 hours and then rapidly cooled, the yield is over 95% and the generated phase is mostly potassium hexatitanate. However, when it is slowly cooled, the potassium tetratitanate phase is formed due to the association reaction. is produced, and the average fiber length increases in proportion to the amount produced. Generally, when a small amount of potassium molybdate or potassium tungstate is used as a catalyst, the fiber length of the fibrous potassium titanate produced is smaller than when a large amount of potassium molybdate or tungstate is used as a flux. Examples 1 to 4 TiO ₂ (rutile type, 325 mesh pass) and K ₂ CO ₃ (325 mesh pass) were mixed in a molar ratio of 4:1 to produce K ₂ O.4TiO ₂ as potassium titanate.
and then mix this with K ₂ as a catalyst.
MoO ₄ is blended in the proportions shown in Table 3 in mol%,
Shake well to mix. Approximately 50 g of this mixture was filled into each 100 ml platinum crucible, heated and melted at 1140°C for 2 hours using a silicon carbide heating element electric furnace (5 kW), and from this temperature
Slowly cool to 1000°C at a cooling rate _of 20°C/hr and
A single phase fiber of _4TiO2 was grown. This melt was then removed from the crucible after dissolving the catalyst with water. The fibers were washed with water and then dried, weighed to determine the yield, and the synthesized phase was identified by powder X-ray diffraction. The results are shown in Table 3.

[Table] As is clear from Table 3, in consideration of the fiber length and yield of the fibrous potassium titanate produced, 5 to 10 mol% of K ₂ MoO ₄ is sufficient as a catalyst; There is no need to use it. Note that this yield can be recovered industrially,
The actual production amount was more than 95% in bulk. Therefore, emphasis is placed on the dissociation-association reaction between the alkali metal titanate and the alkali metal ion, which produces a growth reaction of the fibrous alkali metal titanate (i.e., the molten product is kept at a certain temperature within the range of the melting temperature). Hold time or from melting temperature
Adopting an operating method that gradually cools down to 900℃),
In addition, by using a small amount of alkali metal molybdate or alkali metal tungstate as a catalyst, the problems of corrosion of the reaction vessel and enlargement of equipment can be solved, and highly safe continuous operation is possible. Furthermore, a low-cost fibrous alkali metal titanate can be obtained, which is industrially advantageous.

Claims (1)

[Scope of Claims] 1 Consists of a mixture of a titanium oxide component and an alkali metal compound capable of forming an alkali metal oxide component, and has a composition having the general formula M ₂ O·nTiO ₂ (wherein, M
is an alkali metal; An alkali metal molybdate represented by the general formula M ₂ MoO ₄ (wherein M is the same as above) or a general formula M ₂ as an acid alkali metal and a catalyst.
alkali metal tungstate represented by WO ₄ (wherein M is the same as above) in mol% of 70:30 to
The mixture is mixed at a ratio of 95:5 and the reaction system is heated to melt at a temperature of 900 to 1350°C, or at least the catalyst component is melted, and the alkali metal titanate and alkali metal ion produced in the molten mixture are dissociated and associated. A method for producing a fibrous alkali metal titanate, which comprises growing the alkali metal titanate as a single crystal through a reaction. 2. The manufacturing method according to claim 1, wherein the molten mixture is maintained at a certain temperature within the range of 900 to 1350°C for a certain period of time. 3. The manufacturing method according to claim 1, characterized in that the molten mixture is slowly cooled from the melting temperature to 900°C.