JPH0248411A - Production of swelling synthetic saponite-type clay mineral - Google Patents

Abstract

PURPOSE:To obtain the subject swelling synthetic saponite-type clay mineral having excellent transparency, water-swelling property and thickening speed by the hydrothermal treatment of a uniform suspension composition containing basic Mg, an SiO2-Na component and Al2O3-Na component at specific ratios. CONSTITUTION:The above saponite-type clay mineral containing metal components essentially consisting of Mg, SiO2, Na and Li, having the composition expressed by formula and belonging to a 3-octahedral smectite clay mineral is produced by the following process. A homogeneous suspension composition containing basic Mg, sodium silicate, a combination of sodium silicate and amorphous SiO2, etc., and an Al2O3-Na component containing sodium aluminate, etc., at compositional ratios shown in the formula is prepared beforehand. The composition is charged in an autoclave especially at pH8.5-10 in a state of aqueous slurry and subjected to hydrothermal treatment under a relatively mild condition compared with conventional process, i.e., at 100-300 deg.C under a pressure of 0-100kg/cm<2>-G to obtain the objective swelling synthetic saponite- type clay mineral.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for producing synthetic saponite, and more particularly, to a method for producing synthetic saponite that has excellent transparency when made into an aqueous dispersion.

(Prior art and its problems) Saponite clay mineral is a 3-octahedral smectite clay mineral similar to hectorite and stevensite, but differs from hectorite in that it does not contain lithium in the octahedral layer, and it also contains aluminum. differs from stevensite in that it may be accompanied by substitution of silicon in the tetrahedral layer or magnesium in the octahedral layer, but as a 3-octahedral clay mineral, saponite is similar to hectorite. Synthetic saponite has a structure similar to that of synthetic hectorite and stevensite, so like synthetic hectorite and synthetic stevensite, synthetic saponite has high water swelling properties, gel-forming properties, and inclusion functions for organic and inorganic compounds. It has many uses as a gelling agent and coating agent. Conventionally, the following proposals have been made as the manufacturing method.

For example, as a synthetic silicate having a structure similar to the clay mineral saponite, Japanese Patent Publication No. 63-6486 discloses that a hydrated gel is precipitated from a mixture of sodium silicate, magnesium salt, and aluminum salt with excess alkali, especially ammonia. After removing by-product solutes by washing with water, -valent or divalent cations and fluorine ions are added, and this is subjected to a hydrothermal reaction to form ((Si(h) a. (MgO)b・(A12O3)
c/2・(OH)4-d・Fd) −・My″″8/y
...(1) Here, the numbers in parentheses are crystal lattice components, and M is at least one selected from the group consisting of alkali metal cations, alkaline earth metal cations, and ammonium ions.
ions, a, b, c, d%X and y have the following values:

6 ≦a ≦7.5 4.5 ≦b≦6 0.5 ≦C≦3.5 0 ≦d≦4 0.5 ≦X ≦1.0 1 ≦y≦2 Synthesize the saponite-type mineral represented It is stated that.

However, this method first prepares oxide hydrates of silica, magnesium and aluminum, and then
An exchangeable cation component and optionally fluoride ions are added to the gel to prepare a starting gel composition slurry, and third the slurry is subjected to a hydrothermal reaction to form a saponite-type synthetic silicate. The first step, which is the most important, is to first drop ammonia water glass onto water-soluble magnesium salt, then drop water-soluble aluminum salt, leave it to mature day and night, and then repeat defiltration and washing to remove by-products. It is described that the method consists of an operation for removing salts, that ammoniacal water glass is essential in order to obtain the hydrated gel with the desired molar ratio, and that the above reaction sequence must be followed.

Therefore, this synthesis method uses a large amount of ammonia or alkali, resulting in a large amount of by-product salts, requires multiple reaction steps, and the preferred conditions for the hydrothermal reaction are 300°C, which requires 20 hours. However, it is still not completely satisfactory in terms of manufacturing cost.

(Problems to be Solved by the Invention) The present inventors have discovered that by using basic magnesium carbonate as the magnesium component of the starting material, the present inventors can eliminate the fluorine ions that are an essential component in the conventional method of saponite synthesis. Using water-soluble raw materials of sodium silicate for the silica component and sodium aluminate for the aluminum component, a homogeneous suspension of the three components is formed, and the reaction process is performed under significantly milder hydrothermal reaction conditions than conventional methods, and in one stage. discovered a method of synthesizing saponite minerals.

It has also been found that, as long as basic magnesium carbonate is used as the magnesium component, a homogeneous suspension containing an amorphous gel as the silica component and an amorphous hydrogel as the alumina component can be used as the starting material.

An object of the present invention is to provide a method for easily producing synthetic saponite with excellent transparency, water swelling properties, and thickening rate without using fluorine ions.

Another object of the present invention is to provide a method for easily producing synthetic saponite with uniform particle size and excellent susceptibility and washability.

Still another object of the present invention is to provide a method for producing synthetic saponite that is inexpensive due to low raw material costs and simple reaction operations.

(Means for Solving the Problems) According to the present invention, the metal component substantially consists of magnesium, silica, sodium and lithium, and substantially has the following formula: a Na, 0(6MgO) [bSiO2cAp2O.
]n) a, b, c, and n in the 12O formula satisfy the formula 0 < a
<2゜6<b<8. c= (b-6)/2 and n≧2
In synthesizing saponite which has a composition represented by and which belongs to the 3-octahedral smectite clay mineral, (a
) basic magnesium; (b) (+) sodium silicate; (ii) a combination of sodium silicate and amorphous silica; (lii) a combination of amorphous silica and sodium hydroxide. silica-sodium component, (c) (i) sodium aluminate, (
ii) producing a homogeneous suspension composition containing an alumina-sodium component selected from the group consisting of sodium aluminate and amorphous alumina in a composition ratio substantially represented by the above formula; Provided is a method for producing a swellable synthetic saponite-type clay mineral, which is characterized by hydrothermal treatment.

(Function) The present invention is based on the knowledge that synthetic saponite can be easily synthesized without the presence of fluorine ions when basic magnesium carbonate, especially hydromagnesite, is used as a starting material for the magnesium component of synthetic saponite. It is based on

Saponite basically has a basic skeleton represented by the following formula. Some conventional saponites do not contain fluorine ions, but
Most of the materials obtained in practical use contain fluorine ions, and those that do not contain fluorine ions require more severe hydrothermal conditions during hydrothermal synthesis.

In other words, the Mg ions that form the 3-octahedral smectite structure are highly constrained in terms of position, and it is necessary that the Mg ions be small and have a degree of freedom that allows them to easily shift to the extent that they form. Seem. When comparing hydroxide ions and fluorine ions, the electronegativity of fluorine ions is large, so when fluorine ions surround Mg ions, the electrons of Mg ions are attracted to fluorine, and the Mg ions It is thought that this makes it easier to form a 3-octahedral structure. In addition, Mg ions are easily hydrated, so the apparent ionic radius becomes quite large, but when fluorine ions are around, hydration is naturally suppressed, which is also thought to be the reason why it is easier to form structures. .

On the other hand, the reason why saponite is easily synthesized without the presence of fluorine ions according to the present invention is considered to be as follows. That is, for example, hydromagnesite (4
Basic magnesium carbonate such as MgCO3.
It exists in a form with a significantly lower degree of hydration than g (OH) 2. In addition, when this raw material is used, carbon dioxide gas is generated during the reaction as shown in the formula % formula %, and Mg0 is generated during the highly active nascent stage.
It is thought that -Mg (OH) 2 is produced and effectively participates in the reaction. In addition, Mg (OH) 2 etc. are made into macromolecules, and it takes time to arrange them regularly with the tetrahedral layer of (Sin4), but the Mg0-Mg (
0) 1) 2 is divided into small pieces, and M
The degree of freedom of g ions is also high, and it is thought that it is easy to arrange them. From these, it is recognized that according to the present invention, synthetic saponite can be easily obtained without the presence of fluorine ions.

(Preferred Embodiment of the Invention) According to the present invention, the synthetic saponite is obtained by hydrothermally treating a homogeneous suspension composition comprising a combination of basic magnesium carbonate, sodium silicate, etc., and sodium aluminate, etc.

By selecting basic magnesium carbonate as the magnesium raw material, saponite can be synthesized without containing fluorine ions, which is an essential component in conventional methods, and can be produced in high yield and purity. Any basic magnesium carbonate can be used, but if magnesium carbonate, magnesium hydroxide, or a mixture thereof is used, saponite cannot be produced in high yield and purity. As the basic magnesium carbonate, it is particularly desirable to use hydromagnesite, which has a chemical composition represented by the following formula % (4) and a chemical composition according to ASTM No. 25-513.
It has an X-ray diffraction image assigned to .

As the raw material for the St and Na components, an aqueous sodium silicate solution is advantageously used, but a combination of amorphous silica and sodium hydroxide can also be used. As sodium silicate, sodium silicate of the formula % (5) is used, where n is a number from 1 to 5, in particular from 2.0 to 3.5. Further, as the amorphous silica, silica hydrosil, hydrogel, xerogel, wet amorphous silica, vapor phase amorphous silica, etc. are used.

As the raw material for the Affi component, an aqueous sodium aluminate solution is advantageously used, but a combination of amorphous alumina and sodium hydroxide can also be used.

As sodium aluminate, the ortho form (Na3Afo
Both the s) and meta-type (Na AffiO2) are used. Further, as the amorphous alumina, alumina hydrosil, hydrogel, etc. are used.

The usage ratios of the above components (a), (b) and (C) are determined so as to give the chemical composition of saponite. According to the present invention, a remarkable feature is that synthetic saponite can be easily obtained using each raw material in a composition ratio close to the stoichiometric amount. It is desirable that pi of the reaction raw material mixture is generally in the range of 8 to 11, particularly 8.5 to 10.Adjustment of pH is as follows:
This is carried out by adding an alkali metal dihydroxide or carbonate to the reaction system, if necessary.

Prior to the hydrothermal reaction, the raw materials used are mixed as uniformly as possible to form a homogenized aqueous slurry.
Desirable from the standpoint of improving yield and purity. This homogeneous mixing is preferably carried out under strong shear stirring, and for this purpose, a high-shear mixer, ball mill, sand mill, colloid mill, ultrasonic irradiation, etc. can be used.

In addition, a small amount of sodium silicate has the effect of uniformly dispersing basic magnesium carbonate in an aqueous solution, so even if you prepare a dispersion slurry in which sodium silicate is dispersed as a raw material and then add the remaining raw materials, it will be uniform. Can achieve the purpose of mixing. The sodium silicate used in this case is desirably used in a range of 0.001 to 10% by weight based on the aqueous slurry.

Also, the solid content concentration in the aqueous mixture (well, generally 1 to 3
It is preferably in the range of 0% to 1% by weight, particularly 5 to 15% by weight.

This mixture is placed in an autoclave and subjected to hydrothermal treatment. The hydrothermal treatment conditions may be relatively mild compared to conventional methods, for example, generally at a temperature of 100 to 300°C, particularly 150 to 200°C, and at a temperature of 0 to 100 Kg/
cm2 (gauge), especially 6 to 40 Kg/crn2G
It is best to do this under pressure. The reaction time is generally 0.5
A time on the order of 20 to 20 hours is sufficient. The synthetic saponite obtained by the reaction is separated from the mother liquor into solid and liquid, washed with water,
Dry to make a product.

According to Ki and Akira, the desired saponite cannot be easily obtained in a good yield in the -stage reaction (hydrothermal treatment), and the synthesis conditions may be relatively mild compared to conventional methods. This is one advantage. Moreover, the slurry or "overcake" obtained in the process of synthesizing saponite is of course in a non-swelling state even after washing with water, and by drying it, it can be made into a swellable and aqueous dispersion. The result is a synthetic saponite with outstanding transparency. Moreover, this newly generated saponite...
It has the advantage that it has excellent permeability and that purification operations such as washing with water can be carried out very easily.

The synthetic saponite according to the present invention is generally JIS-K
0069 Chemical sieve residue test method (dry method): 1
00 mesh passing remaining 10% or less, 55 mesh passing remaining 5
% or less of particles.

In addition, this powder is generally 0.8 to 2.0 g/m, g
It has a bulk density of 0.2 meq/g or more, a cation exchange capacity of 0.2 meq/g or more, a BET specific surface area of 150 m27g or more, and the crystal grains are fine in relation to being obtained by the synthetic method. The crystallite size in the b-axis direction is 200 Å or less, the content of impurities is small, and the Hunter whiteness is generally 80% or more, particularly 85% or more.

(Effects of the Invention) According to the present invention, by using basic magnesium carbonate as the starting material for the magnesium component, water-swellable smectite-type synthetic saponite that does not contain a fluorine component and can be obtained at low cost and in high yield is produced. could provide the law.

Example 1 A saponite clay mineral was synthesized by the following method using commercially available basic magnesium carbonate, No. 3 sodium silicate, and ortho-type sodium aluminate as raw materials for magnesium, silica, and aluminum components, respectively.

First, 750 mJ of diluted sodium silicate (liquid A) was prepared by adding water to 426 g of 444 g (St (99.og as h minute) of No. 3 sodium silicate solution while cooling it with ice. Then, sodium aluminate 93 g (
7.5g of Al2O for 5 minutes) was added to 750mJ in the same way.
After preparing a diluted sodium aluminate solution (liquid B), liquid B was slowly poured into liquid A while cooling and stirring to obtain a transparent homogeneous solution (liquid C).

Next, 144 g of basic magnesium carbonate (manufactured by Tokuyama Soda) prepared in advance (59.0 g as MgO content) was added.
After slurrying 4g) with 600mp water, the remaining 3g)
A homogeneous slurry of the magnesium component to which 18 g of sodium silicate No. 1 was added was poured into the above liquid C with stirring to obtain a homogeneous suspension consisting of the three raw materials.

This composition was divided into three equal parts, each of which was placed in an autoclave having an internal volume of 11. 145℃ while stirring,
Hydrothermal treatment was performed at 170°C and 190°C for 5 hours. Gas generated during the process was occasionally exhausted. After the reaction was completed, the contents were allowed to cool and then taken out, filtered and dried to give 74g and 7g, respectively.
7g and 78.5g of product were obtained.

The whiteness of the powder obtained by pulverizing this product in a sample mill was 90 to 95%. In addition, the cation exchange capacity is 0.45 to 0.51 meq/g, and the BET specific surface area is 300 to 400 m2/g.
The b-axis crystallite size was 130 to 170 crystallites.

The test method used in the present invention is shown below.

1. Cation exchange capacity (C, E, C,) Japan Foundry Association,
Test method TIKS- published by Tokai Branch, Inorganic Sand Mold Research Group
413.

2. BET specific surface area Measured using an automatic BET specific surface area measuring device (Sorptomatic 5eries 1800 manufactured by CARLOERBA).

3. Hunter whiteness Measured according to JIS-8123.

4. Crystallite size The crystallite size of the powder sample is determined from “Experimental Chemistry Course 4” No. 23.
X listed on page 8 (1956) published by Marukubi Co., Ltd.
The diffraction peak of plane index [06] was measured by a line diffraction method, and the crystallite size in the b-axis direction was determined in units of individuals.

Example 2 A saponite-type clay mineral was synthesized in the same manner as in Example 1, except that amorphous silica obtained by the following method was used as half of the No. 3 sodium silicate raw material.

67 g of No. 3 sodium silicate (1 as Si02 min.
The solution (5.14 g) was added dropwise to a 50% sulfuric acid solution heated to 60° C. under stirring, and after sufficiently stirring and aging, filtered and washed with water to obtain an amorphous silica hydrogel. This gel was then made into a homogeneous slurry with a 5f02 concentration of 5% by weight in a household mixer.

Add 6g of No. 3 sodium silicate solution to this slurry (S
1.36 g (1.36 g) was added under cooling and stirring. Next, 2.5 g of solution B of sodium aluminate as the AlxOs portion was slowly poured into the solution while stirring while cooling to obtain a translucent homogeneous sol.

Next, Mg prepared in advance in the same manner as in Example 1
Example 1 A homogeneous slurry of basic magnesium carbonate containing 19.8 g of O content and 6 g of No. 3 sodium silicate solution was poured into the above sol together with 2.5 g of a 40% concentration sodium hydroxide solution. A homogeneous suspension similar to that was obtained.

This suspension was then placed in 12 autoclaves,
Hydrothermal treatment was carried out at 170° C. for 5 hours, and 73.4 g of a dry product was obtained in the same manner.

Note that the whiteness of this product is 90%, and C, E, and C are 0.
．． 44 milliequivalent 7g, BET specific surface area 335 m2/
g.

The b-axis crystallite size was 140.

Example 3 The same procedure as in Example 1 was carried out, except that commercially available silica hydrosil was used as the silica component of the raw material, and sodium hydroxide was used in an amount equivalent to 1.3 times the mole of Na2O with respect to the Sin content in this sol. A homogeneous suspension consisting of the three raw materials was prepared, and the entire amount of this suspension was placed in a 102 autoclave.
Hydrothermal treatment was carried out at .degree. C. for 5 hours to obtain 225 g of a dried synthetic saponite product.

In addition, the whiteness of this product is 88%, C, E, (:, is 0.42 milliequivalent/g% BET specific surface area is 310 m2
7g.

The b-axis crystallite size was 210.

Comparative Example 1 Saponite was synthesized in the same manner as in Example 1, except that magnesium hydroxide obtained by the following method was used instead of basic magnesium carbonate for the magnesium component of the raw material.

First, commercially available gnesium chloride (19.8 as MgO content)
The water diluted solution of g) was poured into a sodium hydroxide solution containing ammonia heated to 80° C. under stirring.

Next, the obtained magnesium hydroxide slurry with a pH of 1005 was aged with stirring for 1 hour under heating, and after washing thoroughly with warm water containing 0.5% ammonia, the cake was mixed with a household mixer. It was crushed to make a slurry of magnesium hydroxide.

Next, 33.0 g of liquid A and Alz0 were added as SfO□.
For 3 minutes, 2.5g of B solution was evenly mixed with C solution,
6 g of the above magnesium hydroxide slurry and No. 3 sodium silicate solution were poured into the solution with stirring to obtain a suspension consisting of the three raw materials.

This suspension was placed in an autoclave for 12 hours and heated to 190℃ for 5 hours.
Hydrothermal treatment was carried out for several hours, and the dried reaction product obtained in the same manner as in Example 1 was identified by X-ray diffraction and chemical analysis, but it was not found to be a saponite clay mineral.

Claims (3)

[Claims] (1) Substantially the following formula, aNa2O(6MgO)[bSiO_2cAl_2O_
3] a, b, c, and n in the nH_2O formula are numbers that satisfy the formulas 0<a<2, 6<b<8, c=(b-6)/2, and n≧2. In synthesizing saponite having the composition shown and belonging to the 3-octahedral smectite clay mineral, (a
) basic magnesium; and (b) selected from the group consisting of (i) sodium silicate, (ii) a combination of sodium silicate and amorphous silica, and (iii) a combination of amorphous silica and sodium hydroxide. A composition comprising a silica-sodium component and an alumina-sodium component selected from the group consisting of (c) (i) sodium aluminate, (ii) sodium aluminate and amorphous alumina substantially represented by the above formula. producing a homogeneous suspension composition containing at a ratio of
A method for producing a synthetic swellable saponite-type clay mineral, which comprises subjecting the composition to a hydrothermal treatment. (2) The method according to claim (1), wherein the basic magnesium carbonate is hydromagnesite. (3) Magnesium content and silica content in the homogeneous suspension composition,
The manufacturing method according to claim (1), wherein the alumina content, sodium content, etc. are used in substantially stoichiometric amounts.