JPH0248410A - Production of swelling synthetic hectolite-type clay mineral - Google Patents

Abstract

PURPOSE:To obtain the subject clay mineral having excellent transparency, water-swelling property and thickening speed by the hydrothermal treatment of a uniform suspension composition containing basic MgCO3, an SiO2-Na component and LiOH and/or Li2CO3 at specific ratios. CONSTITUTION:Hectolite 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 CaCO3, an SiO2-Na component (e.g., sodium silicate) and LiOH and/or Li2CO3 at compositional ratios shown in the formula is prepared beforehand. The composition is charged in an autoclave especially at pH8.5-10 generally in a state of aqueous slurry and subjected to hydrothermal treatment at 110-200 deg.C for 0.5-10hr under a pressure of 0.5-15.5kg/cm<2>-G. A swelling hectolite-type clay mineral free from F component can be produced in high yield at a low cost by this process.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a method for producing synthetic hectorite, and more particularly, to a method for producing synthetic hectorite which has excellent transparency when made into an aqueous dispersion. .

(Prior art and its problems) Synthetic hectorite has great water-swelling gel-forming properties and the ability to clathrate organic and inorganic compounds, and is widely used as a thickener, gelling agent, and coating agent. It has several uses. Conventionally, many proposals have been made regarding the manufacturing method.

For example, U.S. Pat. Nos. 3,586,478 and 3,6
No. 71゜190 discloses water-soluble magnesium salts,
Synthetic hectyl silicates, sodium carbonate or sodium hydroxide, and a compound capable of releasing both fluorine ions and lithium ions are mixed in a certain ratio and the aqueous slurry formed is hydrothermally treated. A method of manufacturing a light is disclosed.

Furthermore, in JP-A-52-130499, magnesium oxide, water, hydrofluoric acid and lithium hydroxide are mixed, silica sol is added thereto, heated and mixed to form a gel, and this gel is mixed with water. A method for synthesizing hectorite by heat treatment is described.

Furthermore, JP-A-59-21517 discloses that after mixing sodium silicate and magnesium salt to form a homogeneous mixed solution of the two, both components were precipitated with alkali, and by-product solutes were removed by washing with water. It is described that hectorite-type minerals are synthesized by subsequently adding -valent or divalent cations and fluorine ions and subjecting this to a hydrothermal reaction.

However, these synthetic methods generally require a large amount of alkaline agents or require reaction operations to be carried out in multiple stages, and are still not fully satisfactory in terms of production cost. Hectorite itself requires an extremely long time to obtain a sufficient thickening effect, and its properties as a thickening agent and gelling agent are still not fully satisfactory.

In JP-A-61-275126, the present inventors used activated aluminosilicate obtained by acid-treating natural clay minerals such as acid clay under certain conditions as a silica raw material for hectorite synthesis. As a result, synthetic hectorite could be obtained under extremely mild reaction conditions and with simple operations.
Moreover, the resulting synthetic hectorite has a chemical composition in which a part of the silica content is replaced by alumina content, and as a result, it exhibits unique X-ray diffraction characteristics, as well as excellent water swelling properties and thickening speed. We have discovered the fact that

Furthermore, the present inventors have proposed in JP-A No. 62-59518 a manufacturing method that improves the transparency of the aqueous dispersion of synthetic hectorite obtained in the earlier JP-A No. 61-275126. .

However, all of these methods require the use of activated aluminosilicate, which is obtained by acid treatment of natural clay minerals such as acid clay, as the silica raw material for hectorite synthesis. Because it contains fluorine ions as an ingredient, it is still not fully satisfactory in terms of raw material cost, and it also contains fluorine ions as an anion ingredient, so it is difficult to prevent the effects of these ingredients on the human body or living organisms. Its use is limited.

(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 conventional method of hectorite synthesis can be performed without containing fluorine ions, which is an essential component. Moreover, by using water-soluble raw materials of sodium silicate, lithium hydroxide, or lithium carbonate as the silica component and the lithium component, respectively, and forming a homogeneous suspension of the three, it is not possible to use a large amount of alkali agent as in the conventional method. We have found a method for synthesizing hectorite minerals in substantially stoichiometric amounts without the need for hectorite minerals, under significantly milder hydrothermal reaction conditions than conventional methods, and by a one-step reaction operation.

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.

That is, an object of the present invention is to provide a method for easily producing synthetic hectorite having excellent transparency, ζ water swelling properties, and thickening speed without using fluorine ions or large amounts of alkali.

Another object of the present invention is to provide a method for easily producing synthetic hectorite with uniform particle size 5 and excellent washing and washing properties.

Still another object of the present invention is to provide a method for producing synthetic hectorite which can be produced at low raw material costs and by simple reaction operations.

(Means for Solving the Problems) According to the present invention, the metal component consists of commercially available magnesium, silica, sodium, and lithium, and substantially has the following formula: a Na20 (bJOCL120) [8SlOdnL
O...” (1) where a, b, c and n are numbers that satisfy the formula 0<a<2.4<b<6.0<c<1 and n≧2, expressed as In synthesizing hectorite, which has a composition of
a) basic magnesium carbonate; and (b) selected from the group consisting of (1) sodium silicate, (ii) a combination of sodium silicate and amorphous silica, (iii) a combination of amorphous silica and sodium hydroxide. producing a homogeneous suspension composition containing a silica-sodium component and (c) lithium hydroxide and/or lithium carbonate in a composition ratio substantially represented by the above formula, and hydrothermally treating the composition. A method for producing a synthetic swellable hectorite clay mineral is provided.

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

Hectorite basically has a basic skeleton represented by the following formula. It is known that some conventional hectorites do not contain fluorine ions, but most of the ones that can be obtained in practical use contain fluorine ions, and those that do not contain fluorine ions require more severe hydrothermal synthesis during hydrothermal synthesis. conditions are required.

In other words, the Mg ions that form the 3-octahedral smectite structure are quite 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, It is thought that the ions become smaller and a 3-octahedral structure is more likely to be formed. In addition, J 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 the reason why it is easier to create a 4A structure. Conceivable.

On the other hand, the reason why heclite is easily synthesized without the presence of fluorine ions according to the invention may be as follows. That is, basic magnesium carbonate, such as hydromagnesite (4MgC(h・Mg(OH) 2 ・4H20), has a higher degree of hydration than conventional magnesium salts, e.g. Also, when this raw material is used, carbon dioxide gas is generated during the reaction as shown in the formula % formula %, and M, g
It seems that O-Mg (0+() 2) is generated and effectively participates in the reaction. Also, Mg (OH) 2 etc. have not yet become macromolecules, and have regularity with the tetrahedral layer of (StO4). Although it takes time to arrange, the above Mg0-Mg
(Of+) 2 is in the form of small fragments, and the degree of freedom of Mg ions is high, making it easy to arrange them. From these, it is recognized that according to the present invention, synthetic hectorite can be easily obtained without the presence of fluorine ions.

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

By selecting basic magnesium carbonate as the magnesium raw material, it is possible to synthesize hectorite without containing fluorine ions, which is an essential component in conventional methods.
Furthermore, production with high yield and high purity becomes possible. Any basic magnesium carbonate can be used, but
High yield and high purity production of hectorite cannot be expected by using magnesium carbonate, magnesium hydroxide, or a mixture thereof.As the basic magnesium carbonate, it is particularly desirable to use hydromagnesite. This product has a chemical composition represented by the following formula % (4) and an X-ray diffraction image assigned to STM No. 25-513.

As raw materials for Si and Na components, sodium silicate water (
Part 8 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 35. Further, as the amorphous silica, silica hydrosil, hydrogel, xerogel, wet amorphous silica, vapor phase amorphous silica, etc. are used.

As the lithium source, lithium hydroxide is advantageously used, but it is of course possible to use lithium carbonate and combinations thereof as desired.

The ratios of the above components (a), (b) and (c) are determined to give the chemical composition of hectorite. According to the present invention, a remarkable feature is that synthetic hectorite can be easily obtained using stoichiometric amounts of each raw material. The pH of the reaction mixture is generally preferably in the range 8-11, particularly 85-10. The pH is adjusted by adding an alkali metal hydroxide or carbonate to the reaction system, if necessary.

Although the hydrothermal reaction is generally carried out in the form of an aqueous slurry, it is advantageous in terms of operability to set the solid content concentration in the range of 1 to 30% by weight, particularly 5 to 15% by weight. The hydrothermal treatment is performed by charging the above raw materials into an autoclave and heating them. As for reaction conditions, generally a treatment time of 0.5 to 10 hours at a temperature of 110 to 200°C is sufficient. On this occasion,
The pressure of the reaction system is maintained at 0.5 to 15.5 Kg/cm2 gauge.

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 preferably used in an amount of 0.01 to 10% by weight based on the aqueous slurry.

In addition, the solid content concentration in the aqueous mixture is generally 1 to 30
It is desirable that the amount is in the range of 5 to 15% by weight.

This mixture is placed in an autoclave and subjected to hydrothermal treatment. 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/
crn2 (gauge), especially 6 to 40 Kg/cm”G
It is best to do this under pressure. A reaction time of the order of 0.5 to 20 hours is generally sufficient. The synthetic stevensite obtained by the reaction is separated into solid and liquid from the mother liquor, washed with water, and dried to obtain a product.

According to the present invention, the desired hectorite can be easily obtained in a high yield in the second stage of the reaction (hydrothermal treatment), and the synthesis conditions may be relatively mild compared to conventional methods. This is one advantage. Moreover, the obtained hectorite is not only in the state of the obtained slurry or filtered cake,
Even after washing with water, it is actually in a non-swelling state, and by drying it, it becomes a synthetic hectorite that has remarkable characteristics of excellent swelling properties and transparency when made into an aqueous dispersion. Moreover, this newly generated hectorite is
It has the advantage that it has excellent suitability and that purification operations such as washing with water can be carried out very easily.

The synthetic hectorite according to the present invention generally meets the JIS-0069 chemical sieve residue test method (dry method).
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
, a cation exchange capacity of 0.2 milliequivalents/g or more, a BET specific surface area of 150 m27 g or more, and the crystal grains are fine in relation to being obtained by the synthetic method. The crystal size in the b-axis direction is 200 Å or less,
Moreover, the content of impurities is small, and its 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 hectorite 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 hectorite clay mineral was synthesized by the following method using commercially available basic magnesium carbonate, No. 3 sodium silicate, and lithium hydroxide as raw materials for magnesium, silica, and aluminum components, respectively.

Commercially available basic magnesium carbonate (Tokuyama Soda TT) 103
Put 3g (430g of magnesia) in about 62ml of water,
A slurry was obtained by stirring. No. 3 sodium silicate 4292
g (silica content: 9sig), about 10
0 g was added and stirred to prepare a dispersion slurry. on the other hand,
Dissolve 58 g of lithium hydroxide monohydrate in 151 parts of water,
The remaining No. 3 sodium silicate was added. A magnesium dispersion slurry was added to the solution and thoroughly stirred to form a homogeneous suspension consisting of the three raw materials, which was then divided into three parts and placed in an autoclave each having an internal volume of 10J. 15 while stirring
Hydrothermal treatment was carried out at 0°C, 170°C and 190°C for 5 hours each while occasionally exhausting the gas generated during the process.

After completion of the reaction, purification and drying were carried out to give 1.80.1.8 respectively.
8 and 1.90 Kg of product were obtained.

The whiteness of the powder obtained by pulverizing this product using a sample mill was 85 to 92%. In addition, the cation exchange capacity is 0.44 to 0.52 meq/g, and BE
The T specific surface area was 210 to 250 m'/g, and the crystallite size in the b-axis direction was 125 to 145.

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 Automatic BET specific surface area measuring device (cARLOERBA company I
J Sorptomatic 5eries 1800
).

3. Hunter whiteness Measured according to JIS K-8123.

4. Crystallite size The crystallite size of the powder sample is determined by the surface index [06] according to the X-ray diffraction method described in Experimental Chemistry Course 4'°, page 238 (1956) published by Marukubi Co., Ltd. The diffraction peak was measured, and the crystallite size in the b-axis direction was determined in units of individuals.

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

2146g of No. 3 sodium silicate (4 as SiCh content)
80 g) The solution was added dropwise to a 50% sulfuric acid solution heated to 60° C. under stirring, and after sufficiently stirring and aging, the solution was washed with water to obtain an amorphous silica hydrogel. This gel was then made into a homogeneous slurry with a 5in2 concentration of 5% by weight in a household mixer.

To this tail slurry, the same amount of basic magnesium carbonate slurry used in Example 1 and the remaining No. 3 sodium silicate,
Lithium hydroxide was added and a small amount of sodium hydroxide was added to make a homogeneous suspension composition, which was then hydrothermally treated in the same manner as in Example 1 to obtain a dried product of 1.90 g of synthetic hectorite. .

The whiteness of this product is 89%, C, E, (:, is 0.46 milliequivalent/g, and the BET specific surface area is 290 m2.
7g, and the b-axis crystallite size was 170.

Example 3 A hectorite clay mineral was synthesized in the same manner as in Example 2, except that half of the lithium component of the raw material was replaced with commercially available lithium carbonate.

Note that the whiteness of this product is 90%, and C, E, and C are 0.
45 milliequivalent/g, BET specific surface area is 250 m27g
.

The b-axis crystallite size was 160.

Example 4 In Example 1, commercially available silica hydrosil was used as the silica component of the raw material in the same amount as the silica (S10□) in No. 3 sodium silicate used in Example 1, and the sodium component was A homogeneous suspension of the three raw materials was obtained in the same manner as in Example 1, except that sodium hydroxide was used as (Na20) in an amount equal to the number of moles of silica.
Hydrothermal treatment was carried out at 70° C. for 5 hours to obtain 1.86 kg of a dried synthetic hectorite product.

The whiteness of this product is 87%, and C, E, and C are 0.
．． 43 milliequivalents/g, BET specific surface area 230 m27
g.

The b-axis crystallite size was 165.

Claims (3)

[Claims] (1) Substantially the following formula, aNa_2O(bMgOcLi_2O)[8SiO_2
] a, b, c and n in the nH_2O formula are numbers satisfying the formulas 0<a<2, 4<b<6, 0<c<1 and n>=2, and have a composition represented by In addition, in synthesizing hectorite, which belongs to the 3-octahedral smectite clay mineral, (
a) basic magnesium carbonate; 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. producing a homogeneous suspension composition containing a silica-sodium component and (c) lithium hydroxide and/or lithium carbonate in a composition ratio substantially represented by the above formula, and hydrothermally treating the composition. A method for producing a swellable synthetic hectorite clay mineral characterized by: (2) The manufacturing method according to claim (1), wherein the basic magnesium carbonate is hydromagnesite. (3) Magnesium content and silica content in the homogeneous suspension composition,
The method according to claim 1, wherein the sodium and lithium components are used in substantially stoichiometric amounts.