JPS5921517A - Synthetic swellable silicate and its manufacture - Google Patents

Abstract

PURPOSE:To obtain a novel synthetic swellable silicate having superior gel forming capacity by preparing a homogeneous precipitate consisting of silicon and magnesium, adding an exchangeable cation to the precipitate, carrying out a hydrothermal reaction, drying the reaction product, and pulverizing it. CONSTITUTION:A homogeneous mixed soln. contg. silicic acid and a magnesium salt is prepared by mixing a silicic acid soln. with an aqueous magnesium salt soln. in a proper ratio, and an alkali soln. such as an aqueous ammonia soln. is added to the mixed soln. to form a precipitate. Soluble by-products are sufficiently removed from the precipitate by filtration and washing. The hydroxide or the like of a uni- or bivalent cation is added to the resulting homogeneous precipitate, and after adding fluorine ion as required, a hydrothermal reaction is carried out at 100-350 deg.C. The reaction product is dried at <=about 200 deg.C and pulverized to obtain a synthetic swellable silicate represented by the general formula (where 0<a<10, 0<b<=1, 0<c<=2/3a+b, 1<=y<=2, and M is at least 1 kind of cation selected from alkali metallic ions, alkaline earth metallic ions, ammonium ion and amine).

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a novel synthetic swellable silicate having a structure similar to a 3-octahedral smectite that swells in water and has excellent gel-forming ability, and a method for producing the same.

Stevensite and hectorite are naturally known as swelling clay minerals that contain magnesium and silicon and contain almost no aluminum. According to McEwan, the model chemical formulas of stevensite and hectorite are represented by formulas (I) and (II) (Montmorillonite miner
als by D. M. C. MacEwan, The
X-ray identification and
crystal structures of clay
Minerals edited by G. Bro
wn, Mineralological Society,
London, 1972, pp 143-207).

Here, M+ is a monovalent exchangeable cation present between the layers. Stevensite and hectorite belong to 3-octahedral smectites, with silicon located in the tetrahedral layer and magnesium located in the octahedral layer.

The source of the interlayer charge in stevensite is thought to be based on the deficiency of magnesium in the octahedral layer, and the number of exchangeable cations is higher than that of other species of smectite when compared on the basis of O20(OH)4. It's small, almost half the size. On the other hand, in the case of hectorite, a portion of the magnesium in the octahedral layer is replaced with lithium, and cations enter between the layers in a manner that maintains the negative charge and electrical neutrality.

As a result of many years of intensive research into the synthesis of swellable silicates with excellent cation exchange ability or gel-forming ability, we have developed a new synthetic swellable silicate that does not exist in nature and a method for producing the same. This led to the invention.

That is, this invention is based on the general formula (the values of a, b, c and y in the formula are 0<a<100<b
≦1, 0≦c≦2/3a+b and 1≦y≦2, and M
is at least one cation selected from the group consisting of alkali metal ions, alkaline earth metal ions, ammonium ions, and amines) and a method for producing the same. be.

In this general formula (III), silicon is located in the tetrahedral layer and magnesium is located in the octahedral layer. It is thought to be smectite. Stevensite is the only known naturally occurring smectite that is composed of chemical components similar to the synthetic swellable silicate of the present invention. The source of the interlayer charge in stevensite is thought to be based on the deficiency of magnesium in the octahedral layer, and the number of exchangeable cations is smaller than that of other species of smectite, almost half. As revealed by Sakamoto et al. in the Journal of the Japanese Society of Rock and Mineral Science, the number of ions in the octahedral layer of stevensite produced in Japan is between 5.44 and 5.74, assuming the value of silicon is 8. There is no big difference from 5.84 in formula (I), and the value of cation exchange capacity is 41.0 to 45.4 milliequivalents/100g. On the other hand, in the synthetic swellable silicate of the present invention, when the number of silicones is 8, the number of magnesium constituting the octahedral layer shows a wide range of values from 3 to 10, and the cation exchange capacity is from 60 to 10. 120 milliequivalent/
It shows a high value of 100g. That is, the source of the layer charge of the synthetic swellable silicic acid of the present invention cannot be explained by the structural formula of stevensite shown by formula (I), and there are considerable differences in the chemical composition or cation exchange capacity value. Apparently, this synthetic swellable silicate is considered to be a smectite different from 4 stevensite.

When the number of silicon atoms is 8, the synthetic swellable silicate of the present invention can be synthesized even with a magnesium value between 6 and 10, where no magnesium deficiency is considered, and the source of interlayer charge is due to other factors. This can be easily inferred. In hectorite, which belongs to the 3-octahedral smectite, divalent magnesium in the octahedral layer is replaced with monovalent lithium, and in savonite, tetravalent silicon in the tetrahedral layer is replaced with trivalent aluminum. It is known that interlayer charges are generated by the above, but in the synthetic swellable silicate of the present invention, there are no atoms such as lithium or aluminum that can be substituted in the octahedral or tetrahedral layers. Cation substitution is not considered. In 3-octahedral smectites, the number of cations in the octahedral layer is usually 5.
．． The synthetic swellable silicates of the present invention can also be synthesized with magnesium amounts significantly lower than 6. The general formula (III) is based on the above-mentioned several facts that cannot be satisfactorily explained by the usual model formula of 3-octahedral smectite for the synthetic swellable silicate of the present invention, and contradicts these facts. It can be explained rationally. That is, in the synthetic swellable silicate of the present invention, the charge balance between magnesium and the oxygen, hydroxyl group, or fluorine coordinated to it in the octahedral layer is negative due to the slightly excessive presence of hydroxyl groups or fluorine. This shows that the layer charge is generated by shifting to the side. The amount of coordinating oxygen, hydroxyl, or fluorine changes in proportion to the amount of magnesium present in the octahedral layer, and the ratio of oxygen and hydroxyl groups is the same as the ratio in the ideal structure of 3-octahedral smectite. It is made on the assumption that the ratio is 1:1 when the charge is zero. Fluorine can be introduced into the structure to replace some or all of the hydroxyl groups. When the product of the present invention is chemically analyzed and applied to general formula (III), for example, a) (SiO2)8(MgO2/3)3.32(OH)2
．． 72K0.51a=3.32, b=0.51, C. E
．． C. = 68 meq/100g) (SiO2) 8(
MgO2/3)5.53(OH)4.43Na0.74
a=5.33, b=0.74, C. E. C. =88 milliequivalent/100gc)(SiO2)8(MgO2/3)6
．． 55(OH)5.04Na0.12K0.55a=6
．． 55, b=0.67, C. E. C. =82 milliequivalent/
Equivalent to 100g. Although it is very difficult to accurately quantify the hydroxyl groups coordinated in the octahedral layer, 50
The value of heating loss between 0°C and 850°C is (a) = 3.17
wt. %, (b) = 4.13wt%, (c) = 4.85
wt%, and when converted to the amount of hydroxide, each (a) =
2.66, (b) = 4.09, (c) = 5.01, and the amount of hydroxyl groups calculated from general formula (III) (a) = 2
．． 72, (b) = 4.43, and (c) = 5.04, which proves that general formula (III) has validity.

A method for achieving the present invention will be described below. The method for producing a synthetic swellable silicate of the present invention consists of the following steps. First, a homogeneous precipitate of silicon and magnesium is prepared; second, exchangeable cations and optionally fluoride ions are added to the homogeneous precipitate to form a starting crude slurry; and third, the slurry The product of the present invention can be obtained by hydrothermally reacting the silicate to produce a synthetic swellable silicate, and then drying and pulverizing the hydrothermally reacted product.

In the first step, a homogeneous solution of silicic acid and a magnesium salt is made into a homogeneous precipitate with an alkaline solution, and by-product solutes are removed by filtration and water washing to prepare a homogeneous precipitate. A homogeneous solution of silicic acid and a magnesium salt can be obtained by mixing a silicic acid solution and an aqueous magnesium salt solution or by directly dissolving a magnesium salt in a silicic acid solution. The mixing ratio of silicic acid and magnesium salt may be as long as the value of a is within the range that satisfies the general formula (III), but the usually preferred value of a is 3 to 3.
Between 10 and 10. A silicic acid solution is obtained by mixing sodium silicate and a mineral acid and making the pH of the solution acidic. As the sodium silicate, any of commercially available No. 1 to No. 4 water glass and sodium metasilicate can be used. Nitric acid, hydrochloric acid, sulfuric acid, etc. are used as mineral acids. When mixing sodium silicate and mineral acid, it is necessary to select the ratio of sodium silicate and mineral acid so that the pH of the solution is 5 or less, since gelation often occurs if the amount of mineral acid is small. In addition, if the amount of mineral acid is large, the pH of the silicic acid solution will drop too much, and if a homogeneous precipitate is to be generated using an alkaline solution in a later operation, a large amount of alkaline solution will be required, and furthermore, a large amount of by-product salt will be produced. It is desirable to adjust the ratio of sodium silicate and mineral acid so that the pH of the silicic acid solution is between 1 and 3. Next, a homogeneous mixed solution of silicic acid and magnesium salt and an alkaline solution are mixed at room temperature to obtain a homogeneous precipitate. As the alkaline solution, ammonia water, sodium hydroxide solution, potassium hydroxide solution, etc. are used. The amount of alkaline solution is p after mixing
It is desirable to select an amount such that H is 10 or more. When a homogeneous mixture of silicic acid and magnesium salt is mixed with an alkaline solution, the homogeneous mixture may be dropped into the alkaline solution to cause precipitation, or the mixture may be added dropwise in the reverse order. A homogeneous precipitate can also be obtained by instantaneously mixing both solutions. Although stirring is not particularly required during mixing, stirring is absolutely prohibited. Next, filtration and washing with water are repeated to sufficiently remove by-product electrolytes.

The starting material slurry for the second step is prepared by adding an aqueous solution of cationic hydroxide, fluoride, or a mixture thereof to the homogeneous precipitate obtained in the first step, or by adding hydrofluoric acid if necessary. be done.

The amount of exchangeable cations added is given by c in general formula (III), and the usually preferred value is 0.5 to 0.9, but addition of up to about 4 times the amount is permitted. Although the addition of fluorine is not particularly necessary, depending on the manufacturing conditions, its addition can help increase the hydrothermal reaction rate and positively influence the viscous properties of the product.

In the third step, the hydrothermal reaction, the starting material composition slurry obtained in the second step is charged into an autoclave and reacted at a temperature of 100°C to 350°C under autogenous pressure to produce the synthetic swellable silicate of the present invention. urge Although stirring is not particularly required during the reaction, stirring is absolutely prohibited. In general, the higher the reaction temperature, the faster the reaction rate, and the longer the reaction time, the better the crystal formation.
Under these conditions, a reaction time of at least 12 hours, preferably 24 hours or more is required; under the conditions of 41 kg/cm2 and 250 DEG C., 1 to 6 hours is sufficient.

In the fourth step, after the completion of the hydrothermal reaction in the third step, the contents of the autoclave are taken out, dried at a temperature of 60° C. or higher and 200° C. or lower, and pulverized to obtain a final product.

The novel synthetic swellable silicate produced by carrying out the present invention was determined by X-ray diffraction, differential thermal analysis, infrared absorption spectrum, chemical analysis, cation exchange capacity (C.E.C.), and viscosity. It can be evaluated by measuring characteristics.

The novel synthetic swellable silicate of the present invention has a diffraction angle (2θ) of (35,
06), it appears at about 61 degrees, and is found to be a 3-octahedral smectite. The X-ray diffraction pattern is similar to that of hectorite or savonite, but the peaks are generally somewhat broader compared to other 3-octahedral smectites. Usually 70-10 in aqueous solution
It exhibits a high cation exchange capacity of 0 meq/100g,
Alternatively, it exhibits excellent swelling and dispersibility in water, and is characterized by producing an aqueous gel with almost no coloration.
Because it has thixotropic properties, it is extremely useful as an additive for cosmetics, pharmaceuticals, water-soluble paints, etc., a suspension stabilizer for solid particles, and a thixotropic agent. In addition, since it is synthesized from reagents, it essentially contains almost no heavy metal ions, making it suitable for applications in the food field, such as removing cloudiness from vinegar and wine. Furthermore, it can be used as a lipophilic clay by forming an organic composite, or by forming an interlayer composite with a metal polynuclear complex, it is useful as a catalyst, catalyst carrier, adsorbent, etc.

Next, an example will be given and explained.

Example 1 Put 400 ml of water into a 1 liter beaker and place it in a No. 3 water glass (
SiO2 28%, Na2O 9%, molar ratio 3.22) 86
g was dissolved, and 25 ml of 12N hydrochloric acid solution was added at once with stirring to obtain a silicic acid solution. Next, 55 g of magnesium hydrochloride hexahydrate first class reagent (98% purity) was added to 100 ml of water.
Silicic acid prepared by adding a solution of silicic acid to a silicic acid solution.
The homogeneous magnesium salt solution is added dropwise to 380 ml of 2N sodium hydroxide solution over 5 minutes with stirring. Immediately, the reaction precipitate obtained is filtered and thoroughly washed with water, and then 20 ml of an aqueous solution containing 3 g of sodium hydroxide is added to form a slurry, and the slurry is transferred to an autoclave. 41kg/cm
2. React at 250°C for 3 hours. After cooling, the reaction product is taken out, dried at 80° C., and then pulverized using a grinder.

This product corresponds to a=5.33 and b=0.90, contains sodium as a cation, and has a cation exchange capacity of 88 milligram equivalents/100 g. The X-ray powder diffraction diagram is 3-
It shows a pattern similar to hectorite or saponite, which are octahedral smectites, but each peak is broad overall, and the d value of the (35,06) reflection peak is 1.
．． It was 534 Å. The 2% aqueous solution formed a solid gel with thixotropic properties after being left for a day and night.

Example 2 A reaction precipitate was prepared in the same manner as in Example 1. However, the magnesium chloride hexahydrate first-class reagent used (purity 98
%) amount is 67.4 g, and 350 ml of 20% aqueous ammonia is used as the alkaline solution. Next, 20 ml of an aqueous solution containing 3 g of sodium hydroxide is added to the obtained reaction precipitate to form a slurry, and the slurry is transferred to an autoclave having an internal volume of 1 liter. React at 41 kg/cm2 and 250°C for 3 hours. After cooling, the reaction product was taken out, dried at 80° C., and then crushed using a grinder.

This product corresponds to a=6.55 and b=0.80, contains sodium as a cation, and has a cation exchange capacity of 80 milligram equivalents/100 g. The X-ray powder diffraction diagram is from Example 1.
It shows a pattern similar to that of the product of (35, 06)
The d value of the reflection peak was 1.528 Å.

When 3 g of this product was dispersed in 97 ml of water, a large thixotropic solid gel was formed.

The results of comparing the viscosity of the aqueous dispersions of the products of the present invention obtained in Examples 1 and 2 with the aqueous dispersions of Kunivia F and Osmos N, which are commercially available purified bentonites, are as follows. It is recognized that it has an extremely high thickening effect.

Viscosity of aqueous dispersion* (centipoise/25°C) *Measured using a rotational viscometer, Pisco Tester, 62.5 rpm Since the products of the present invention obtained in Examples 1 and 2 do not contain fluorine, they can be used in foods, cosmetics, etc. It is useful for use in fields such as medicine.

Example 3 A reaction precipitate was prepared in the same manner as in Example 1. However, the mineral acid used is 23 ml of 16N nitric acid, and the amount of magnesium chloride hexahydrate first-class reagent (98% purity) is 31 g.
350 ml of 20% ammonia water is used as the alkaline solution. Next, 1.47 g of sodium hydroxide and 20 ml of 10% hydrofluoric acid are added to the obtained reaction precipitate to form a slurry, and the slurry is transferred to an autoclave having an internal volume of 1 liter.

React at 41 kg/cm2 and 250°C for 3 hours. After cooling, the reaction product is taken out, dried at 80° C., and then pulverized using a grinder.

This product corresponds to a = 3.34, b = 0.58, c = 20, contains sodium as a cation, and has a cation exchange capacity of 78 milligram equivalents/100g. The X-ray powder diffraction pattern shows a similar pattern to that of the product of Example 1, but
(001) The reflection peak is slightly sharp. (
35,06) The d value of the reflection peak was 1.516 Å.

When 2 g of this product was dispersed in 98 ml of hot water, a large solid gel with extremely thixotropic properties was formed.

The measurement results of the viscosity of the 2% aqueous dispersion of this product at various temperatures are as follows, and it is recognized that the product of the present invention has an extremely high thickening effect at high temperatures, and is particularly useful for use at high temperatures.

Viscosity of 2% aqueous dispersion * (centipoise) * Measured using rotational viscometer Pisco tester at 625 rpm Example 4 Put 90 ml of 4N nitric acid solution into a 1 liter beaker, and mix with No. 3 water glass (SiO2 28%, Na2O 9%, molar ratio 3). ．．
22) 400 ml of an aqueous solution in which 86 g of silicic acid was dissolved was slowly added dropwise while stirring to obtain a silicic acid solution. Add magnesium chloride hexahydrate first class reagent (98% purity) to this silicic acid solution.
A homogeneous solution of silicate-magnesium salt obtained by dissolving 3 g of the silicic acid-magnesium salt was added dropwise to 350 ml of 20% aqueous ammonia over 3 minutes with stirring. A raw material slurry is prepared from the reaction precipitate left to ripen overnight in the same manner as in Example 1. However, the reagent to be added is 20ml of an aqueous solution containing 21g of potassium hydroxide.
shall be. Transfer raw material slurry to autoclave, 41k
g/cm2 and react at 250°C for 3 hours. After cooling, the reaction product is taken out, dried at 80° C., and then pulverized using a grinder.

This product has a=8.05. It corresponds to b=0.74, contains potassium as a cation, and has a cation exchange capacity of 68 milliequivalents/100 g. The X-ray powder diffraction diagram is from Example 1.
It shows a pattern similar to that of the product, but each peak is broader overall, and the (001) reflection peak in particular is not prominent. (35,06) The d value of the reflection peak is 1.
It was 539 Å. When 4 g of this product was dispersed in 96 ml of hot water, a large solid gel with extremely thixotropic properties was formed.

Patent applicant Seiichi Ishizaka, Director of the Agency of Industrial Science and Technology Designated agent Manabu Izumi, Director of Tohoku Industrial Technology Testing Institute, Agency of Industrial Science and Technology

Claims (1)

[Claims] 1) General formula (in the formula, the values of a, b, c and y are 0<a<10, 0<
b≦1, 0≦c≦2/3a+b and 1≦y≦2,
M is at least one cation selected from the group consisting of alkali metal ions, alkaline earth metal ions, ammonium ions and amines). 2) A homogeneous mixed solution of silicic acid and magnesium salt is precipitated with an alkaline solution, by-product solutes are removed by filtration and washing with water, and then monovalent or divalent cations and, if necessary, fluorine ions are added, It has a structure similar to 3-octahedral smectite, which is characterized by carrying out a hydrothermal reaction under conditions of 100 to 350 °C, then drying and pulverizing. The value of y is 0<a<10, 0<
b≦1, 0<c≦2/3+b and 1/≦y≦2,
M is at least one cation selected from the group consisting of alkali metal ions, alkaline earth metal ions, ammonium ions, and amines.