JPS6126495B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention provides a novel method for producing fibrous calcium potassium silicate. Specifically, it is a method of preparing fibrous calcium potassium by charging silicon dioxide or a compound containing silicon dioxide, potassium hydroxide, and a water-soluble calcium compound at a specific charging ratio, and causing a hydrothermal reaction under pressure. Conventionally, various studies have been conducted on the reactions of silicon dioxide, alkali metal salts, and calcium compounds, but there is almost no knowledge that the reaction products become fibrous. The present inventors have been diligently researching the synthesis of calcium silicate compounds for many years, and found that by reacting silicon dioxide, potassium hydroxide, and a water-soluble calcium compound at a specific charging ratio under specific conditions, They discovered that fibrous calcium potassium silicate could be obtained and completed the present invention. In the present invention, silicon dioxide or a compound containing silicon dioxide, potassium hydroxide, and a water-soluble calcium compound are reacted when K ₂ O in these raw materials is X moles, SiO ₂ is Y moles, and CaO is Z moles. Therefore, if potassium salt is by-produced, the raw material charging coefficient T calculated by the following formula (A), and if no potassium compound is by-produced by the reaction, by the following formula (B), is 1.0 to 2.5, and X/ In this method, fibrous calcium potassium silicate is produced by charging the mixture so that Z is 1.5 to 6, and carrying out a hydrothermal reaction under pressure at a temperature of 150 to 250°C. T=9Y-32Z/9X-12Z...(A) T=9Y-32Z/9X-3Z...(B) Here, X, Y, and Z are of course positive numbers, and formulas (A) and (B) The denominator and numerator in are also positive numbers, respectively, as will be shown in the examples below. Through chemical analysis, it is estimated that the fibrous calcium potassium silicate obtained in the present invention has a general formula of approximately 3K ₂ O・9CaO・32SiO ₂・nH ₂ O (where n is a number from 0 to 20). It is a new compound. In general, the general formula of each type of crystal can be determined by chemical analysis. However, for the silicates and the like that are the object of the present invention, it is difficult to obtain an accurate general formula for the following reasons, and it can only be estimated on the assumption that there are some fluctuations in the coefficients. The first is that impurities that are difficult to separate are often incorporated into the crystal below the solid solubility limit. The second problem is that in a crystal having ion exchange ability, each ion is contained in the crystal according to the ion exchange equilibrium, so the composition changes depending on the pH and liquid composition. For example, in the general formula estimated in the present invention, there are examples in which a part of K is ion-exchanged with Na or Ca, and a part of Ca is ion-exchanged with Na, K, or the like. The fact that the general formula of silicate is difficult to specify is explained in Japanese Patent Application Laid-Open No. 114397/1983, for example, 0.9±0.2M2/ _o O:A.
₂ O ₃ :2.5±0.5SiO ₂ .0 to 8H ₂ O (where M is a metal cation and n is its valence) This is also understood from the other descriptions. The fibrous calcium potassium silicate obtained in the present invention has ion exchange ability due to K ₂ O contained in the molecule.
Furthermore, although fibrous calcium potassium silicate generally has water of crystallization after production, the water of crystallization separates at 250 to 300°C, and has the property of condensing when it comes into contact with water. Utilizing these properties, the fibrous calcium potassium silicate is a substance that can be widely used as an ion exchanger or a desiccant. Further, when the crystallization water is dried at 100° C. for 8 hours, the crystallization water generally becomes about 12%. As mentioned above, this water is separated at 250 to 300°C, but since it has the property of condensing, the properties of calcium potassium silicate remain unchanged even if all or part of the water is removed. Therefore, it can be said that the crystallization water of calcium sodium silicate obtained by the present invention has the properties of fluorite water. The raw materials of the present invention are at least three components: silicon dioxide or a compound containing silicon dioxide, potassium hydroxide, and a water-soluble calcium compound. As the silicon dioxide, wet-processed silicon dioxide obtained by reacting an alkali silicate with a mineral acid, that is, hydrated silicic acid, is generally preferably used. Further, the compound containing silicon dioxide is not particularly limited as long as it is soluble in the reaction system, and any known compound can be used, and in general, natural substances such as clay and quartz, or compounds such as silicon dust can be suitably used. Furthermore, the water-soluble calcium compound is not particularly limited as long as it is water-soluble, and any known compound can be used. Typical examples that are commonly used are calcium hydroxide, calcium oxide,
These include calcium chloride, calcium nitrate, and calcium sulfate. That is, water-soluble calcium compounds are
For example, calcium sulfate, which has a relatively low solubility in water, can be used, but only the amount consumed to produce calcium potassium silicate during the reaction dissolves, so it can be used as a raw material for industrial purposes. . However, since water-insoluble calcium compounds such as calcium carbonate hardly dissolve in water, fibrous calcium silicate cannot be obtained industrially. It is necessary to use at least the above-mentioned three components as raw materials in the present invention, but when attempting to obtain fibrous calcium potassium silicate industrially, it is necessary to select the following specific raw material charging coefficients. . That is, K ₂ O in the raw material is X mol, SiO ₂ is Y mol, and
When CaO is Z moles, if potassium salt is by-produced by the reaction, use the formula (A) below, and if potassium salt is not by-produced by the reaction, calculate the raw material charging coefficient T by the formula (B) below. It is necessary to charge the raw materials so that the ratio is in the range of 1.0 to 2.5, preferably 1.2 to 1.9, and X/Z is in the range of 1.5 to 6. T=9Y-32Z/9X-12Z...(A) T=9Y-32Z/9X-3Z...(B) (However, X, Y, and Z are of course positive numbers, and (A),
(The denominator and numerator in formula (B) are also positive numbers, respectively, as shown in the examples below.) When potassium salt is produced as a by-product by the above reaction, and when the water-soluble calcium compound is calcium chloride, calcium sulfate, etc. In some cases, these anions combine with potassium to produce potassium salts such as potassium chloride, potassium nitrate, potassium sulfate, etc. as by-products. In addition, the case where potassium salt is not produced as a by-product in the above reaction corresponds to the case where calcium hydroxide, calcium oxide, etc. are used as the water-soluble calcium compound, and the case where potassium salt is not produced by reacting with potassium. It is. When the raw material charging coefficient T is smaller than the lower limit value, even if fibrous calcium potassium silicate is produced, the reaction requires a long time, for example, several days to a few days, so it cannot be selected industrially. Moreover, when the raw material preparation coefficient T is larger than the above upper limit value, fibrous calcium potassium silicate is produced, but
At the same time, a large amount of potassium silicate represented by crystalline K ₂ O.4SiO _{2.H 2} O may be produced as a by-product, and it may not be possible to separate it from the fibrous calcium potassium silicate. Further, it is preferable that the silicon dioxide component and the potassium component in the raw materials are present in excess of the amount necessary for producing fibrous calcium potassium silicate. Generally, it is necessary to select the above-mentioned excess amount so that the molar ratio of K ₂ O/CaO in the raw material, ie, the above-mentioned X/Z, is in the range of 1.6 to 6, preferably 2 to 4. If X/Z is smaller than the above lower limit, the production rate of fibrous calcium potassium silicate may be slow, which may be industrially disadvantageous. On the other hand, if X/Z is larger than the above upper limit, the desired product, fibrous calcium potassium silicate, can be obtained, but the amount of unreacted potassium silicate recovered will be large, which will be disadvantageous in terms of equipment, so it is not suitable for industrial use. It cannot be said that it is advantageous. In the above, the raw material preparation coefficient T and K ₂ O in the raw material /
Although suitable criteria for the CaO molar ratio have been explained, these values vary depending on the type of raw materials, reaction conditions, etc., and cannot be determined unconditionally. Therefore, it is preferable to determine a suitable value in advance depending on the type of raw materials, reaction conditions, etc. before carrying out the reaction. The water-soluble calcium compounds in the raw materials in the present invention are digested to produce nearly 100% fibrous calcium potassium silicate. This will be clear from the examples described below, but after filtering off the fibrous calcium potassium silicate produced by the reaction, it becomes clear that almost no calcium component is observed in the filtrate. Therefore, the calcium content is approximately 100
% The composition of the raw material charge can be determined by considering that the above-mentioned calcium potassium silicate is formed. More specifically, the determination of the raw material charging ratio can be explained by citing an example as follows. As mentioned above, it is clear that almost all of the water-soluble calcium compound is digested into fibrous calcium potassium silicate, so once the amount of calcium potassium silicate to be obtained is determined, the amount of water-soluble calcium compound required can be determined. The amount of is determined. That is, the required CaO mole in the raw material (the above Z
mole) is determined. Next, the K ₂ O/CaO molar ratio, ie, the value of X/Z, is determined as appropriate. If K ₂ O/CaO
If the molar ratio is set to 3, the necessary K ₂ O
The moles are determined. Since K ₂ O is derived only from the raw material potassium hydroxide, the amount of potassium hydroxide required is determined. Next, ₂ moles of SiO 2 can be calculated according to the formula for calculating the amount T of raw material charged. From this result, the silicon dioxide or 2
The amount of the compound containing silicon oxide to be used may be determined. The preparation of raw materials in the present invention is not particularly limited except for the necessary requirements described above, and the order of addition of each component is also not particularly limited. Generally, each raw material may be added to an aqueous solution, or an aqueous solution or slurry solution may be prepared for each raw material, and these liquids may be mixed. Fibrous calcium potassium silicate can be obtained by subjecting the aqueous solution containing the above-mentioned at least three raw materials to a hydrothermal reaction under pressure. If the reaction temperature under hydrothermal conditions is too low, the reaction time may become extremely long; on the other hand, if the temperature is high, not only is there a loss of thermal energy, but the production of a pressure-resistant container becomes expensive, making it uneconomical. Generally 150-250
It is most preferable to select the temperature within the range of ℃. It is generally sufficient to carry out the reaction at a vapor pressure at the reaction temperature, and it is usually preferable to carry out the reaction in a sealed container, such as an autoclave. If the reaction is carried out under such conditions, fibrous calcium potassium silicate can usually be obtained in a reaction time of about 10 to 40 hours. The fibrous calcium potassium silicate obtained by the hydrothermal reaction under pressure can be separated by filtration. The fibrous calcium potassium silicate separated by filtration may be washed with water and dried as required to obtain a product. In addition, the filtrate obtained by separating the fibrous calcium potassium silicate by filtration contains unreacted silicon dioxide and potassium hydroxide, so it can be recycled as it is or after removing other by-products, part or all can be recycled as a raw material. I can do it. In general, when calcium hydroxide or calcium oxide is used as a water-soluble calcium compound, no by-products are usually generated and it can be recycled as is.However, as a water-soluble calcium compound, calcium chloride, calcium nitrate,
When calcium sulfate or the like is used, potassium salt is produced as a by-product as described above. If potassium salts are produced as a by-product, it is preferable to remove these potassium salts before circulating the filtrate as a raw material. EXAMPLES In order to explain the present invention more specifically, the present invention will be described below with reference to Examples, but the present invention is not limited to these Examples. Example 1 1.0 mol/potassium hydroxide solution 100 c.c. and 0.25
Mix 100 c.c. of slaked lime slurry and add hydrated silicate Toxil Gu (trade name) to this slurry.
17.65 g (SiO ₂ content: 85%) was added and stirred well.
In this case, the raw material charging coefficient T calculated from the above formula (B) was 1.76. This slurry was placed in an autoclave, sealed, and reacted at a temperature of 200° C. for 20 hours. The reaction product was filtered, washed three times with 100 c.c. of ion-exchanged water, and then dried at 100°C for 8 hours. The yield of this dried product was 8.6 g. According to chemical analysis, this product is approximately
The composition was estimated to be 3K ₂ O・9CaO・32SiO ₂・20H ₂ O. Observation using an electron microscope reveals that the length is approx.
It was confirmed that it was a fibrous material with a diameter of 220μ and an aspect ratio of 120. Incidentally, the filtrate obtained by filtering the reaction product contained almost no calcium. Example 2 The same procedure as in Example 1 was carried out except that the raw material ratio and reaction conditions in Example 1 were changed as shown in Table 1. The results are shown in Table 1.
The total charging volume was 200 c.c. as in Example 1.

[Table] Although it was confirmed that No. 7 contained a small amount of K ₂ O・4SiO ₂・H ₂ O, X-ray diffraction and chemical analysis showed that the main component was calcium potassium silicate. confirmed. It was confirmed that all samples other than No. 7 were calcium potassium silicate with almost no impurities. Example 3 Potassium hydroxide solution, the above-mentioned hydrated silicic acid, and calcium chloride solution were mixed as shown in Table 2 so that the total volume was 200 c.c., and after stirring strongly, the mixture was placed in an autoclave and sealed. The reaction was carried out at 200° C. for 20 hours. The charging conditions and results were as shown in Table 2. In all cases, it was confirmed that the fibers were almost 100% calcium potassium silicate fibers.

[Table] Example 4 The same preparation conditions and the same treatment were carried out except that the No. 2 raw material of Example 3 was changed, and the results shown in Table 3 were obtained. It was confirmed that calcium-potassium silicate fibers could be synthesized with good yield in both cases.

[Table] The hydrated silicic acid is the one mentioned above, and the white clay is Beppu white clay.
The quartz used had a SiO ₂ content of 90% and a 325-mesh structure, and the quartz had a SiO ₂ content of 99.1% and a 325-mesh structure. Example 5 1.4 g of calcium oxide was ground into 100 meshes and poured into 100 c.c. of water. This slurry is 1.0
Mix with 100 c.c. of mol/potassium hydroxide solution. This slurry is further added with hydrated silicate Toxil Gu.
(Product name, SiO ₂ content 85%) 17.65 g was added and stirred well. In this case, the raw material charging coefficient T calculated from the above formula (B) was 1.76. This slurry was treated in the same manner as in Example 1. The product in this case was found to be calcium potassium silicate as a result of chemical analysis, and was confirmed to be fibers with a length of 200 μm using a microscope. The yield was 8.6g.

Claims (1)

[Scope of Claims] 1. Silicon dioxide or a compound containing silicon dioxide, potassium hydroxide, and a water-soluble calcium compound, in which K ₂ O in these raw materials is X moles, SiO 2 is Y moles, and SiO ₂ is Y moles,
When CaO is Z moles, if potassium salt is by-produced by the reaction, use the formula (A) below, and if potassium salt is not by-produced by the reaction, calculate the raw material charging coefficient by formula (B) below. T is 1.0 to 2.5, and X/
Prepare so that Z is 1.5~6, under pressure, 150~
A method for producing fibrous calcium potassium silicate characterized by reaction at a temperature of 250°C T=9Y-32Z/9X-12Z...(A) T=9Y-32Z/9X-3Z...(B) However ( In formulas A) and (B), X, Y, Z, denominator, and numerator are each positive numbers. 2. The method according to claim 1, wherein the silicon dioxide is hydrated silicic acid. 3. The method according to claim 1, wherein the compound containing silicon dioxide is clay or quartz. 4. The method according to claim 1, wherein the water-soluble calcium compound is one selected from the group consisting of calcium hydroxide, calcium oxide, calcium nitrate, and calcium sulfate. 5. The method according to claim 1, wherein the raw material charging coefficient T is 1.2 to 1.9. 6. The method according to claim 1, wherein the reaction temperature is 150 to 250°C.