JPH02157116A - Production of raw material for kaolinite-based synthetic clay - Google Patents

Abstract

PURPOSE:To industrially mass-produce the subject raw material for synthetic clay almost equivalent to natural clay by mixing a specified amt. of quick lime or slaked lime into various siliceous materials, subjecting the mixture to hydrothermal reaction and exposing the formed hydrated calcium silicate compd. in an oxidizing atmosphere to convert difficult-to-react quartz to easy-to- react silica. CONSTITUTION:The powdery quick lime or slaked lime is mixed into the various siliceous material powders having a high content of silica so that the molar ratio of CaO to (SiO2+Al2O3) is controlled to 0.2-2.0. An appropriate amt. of the easy-to-react A source (e.g. AlCl3) is then mixed into the mixture, water is further added in the acidic region at about pH 2, and the mixture is subjected to hydrothermal reaction at 150-250 deg.C for several hours. The formed hydrated calcium silicate compd. is exposed in an acidic atmosphere, and the difficult-to- react quartz is converted to easy-to-react silica. By this method, the raw material appropriate for efficiently producing the kaolinite-based synthetic clay almost equivalent to natural clay is produced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for producing a raw material for industrial mass production of kaolinitic synthetic clay.

[Prior art and technical issues to be solved] Conventionally, raw materials for obtaining kaolina+-it synthetic clay include:
The following are known:

, highly crystalline silicates or aluminosilicates.

11. Amorphous or low-crystalline naturally occurring silicates, aluminosilicates, etc.

111, easily reactive high-purity artificial reagents (colloidal silica, etc.), etc.

However, the following problems have been pointed out with the conventionally known raw materials for producing kaolinitic synthetic clay.

That is, when using the silicates or aluminosilicates mentioned in 1 above, a large amount of free impurities such as quartz and mica remain as they are, and in order to completely eliminate these impurities, the temperature must be higher than 300°C. Since it is necessary to perform hydrothermal treatment at high temperatures for several tens of days at different intervals over a long period of time, there is a problem in productivity. Unfortunately, it is necessary to carefully select the raw materials by performing a troublesome and time-consuming sorting process.Furthermore, in the method using the raw materials in 111 above, the yield is low because the raw materials must be processed in a very dilute liquid form.
Moreover, the raw materials were extremely expensive and uneconomical.

The present invention was made in view of the above-mentioned difficulties in the conventional production technology for kaolinitic synthetic clay, and is suitable for the efficient production of kaolinitic synthetic clay that is similar to natural clay. The technical challenge is to provide a new method that can industrially mass-produce raw materials.

[Means for solving problems]

In order to solve the above-mentioned technical problems, the present inventors sought raw materials suitable for easily and inexpensively producing easily reactive kaolinitic synthetic clay, and tried to find a material with a trial tV error molar ratio of 0.5 to 2. 0, water is added to this mixture, a hydrothermal reaction is carried out at 150°C or higher to produce a hydrous silicate lime compound, and then by exposing the compound to an acidic atmosphere, quartz, which is difficult to react, is made to react easily. The method is to convert it into silicic acid.

Therefore, the siliceous raw material used as a starting material in this first method may be one having a large number of silicic bones (although there is no particular restriction on it. Also, as the calcareous raw material, powdered quicklime or powdered slaked lime may be used). is desirable.

The hydrous silicate lime compounds obtained in this way are crystalline materials such as zonotrite (6Ca0.6SiOzi120) and 11-tobermorite (5CaO-65iO,!, 511zO), other gel-like materials, or A1. Fe,
Although there are many types of clays with different crystal structures, such as those containing ions such as K and Na, all of them are effective as raw materials for kaolinitic synthetic clay to achieve the purpose of the present invention.

Next, the second methodological means adopted by the present invention to solve the above-mentioned technical problem is that after repeated test research on grasses, it happened that a hydrous silicate lime-based compound was exposed to an acidic atmosphere. The fact that the connective tissue of silicic acid and lime is easily destroyed and hydrated silicic acid becomes Mlllltl, 11.
500 to 900 rice husks derived from the production process of rice, wheat, etc.
We have discovered that when oxidized and calcined at ℃ and incinerated, a powder containing almost no carbon and mainly composed of amorphous silicic acid is produced.

Therefore, in search of a way to industrially utilize the new facts learned through this discovery, we proceeded with further research for practical application, and produced hydrated silicic acid obtained by the treatment in 1 above, or 11 above. As a result of adding a highly reactive aluminum compound to amorphous silicic acid and subjecting it to hydrothermal treatment, the bottlenecks in manufacturing the conventional kaolina I-quality synthetic clay mentioned above were solved at once.
This is the result of arriving at the present invention.

That is, the first method adopted by the present invention to solve the above technical problem is to add quicklime or slaked lime to various silicate raw material powders and add 50% of CaO/SiO□+AI□03 rice husk.
By burning and ashing in an oxidizing atmosphere at a temperature of 0 to 900°C, a powder containing easily reactive amorphous silicic acid as a main component is produced.

Therefore, as the rice husk of the grass family plant used as the starting material in this second method, it is preferable to use rice husk, which is produced in large quantities as a by-product through rice farming in Japan and is difficult to dispose of due to the cause of smoke pollution. High quality amorphous silicic acid with a content of 5i0290% or more can be obtained by incinerating the rice husks. In this case, the ashing conditions are 50
The temperature is preferably 0°C or higher and 900°C or lower. This is 500℃
This is because if the temperature is lower than 900° C., carbon tends to remain, and if the temperature is higher than 900° C., crystalline silicic acid derivatives such as cristobalite or tridymite are likely to be formed. In addition, during ashing, it is necessary to supply sufficient oxygen in order to prevent carbon from remaining.

In addition, when producing kaolinite synthetic clay using the raw materials obtained by the first invention method and the second invention method described above, first the composition ratio of kaolinite (Al/Si
Add an appropriate amount of easily reactive aluminum sources (e.g., aluminum chloride, aluminum nitrate, gelled aluminum hydroxide, alumina sol) to each of the above raw materials so that the atomic ratio is close to 1"), and 150~
A hydrothermal reaction is carried out at 250°C for several hours or more. By processing in this way, it is possible to easily obtain pure white, high-quality synthetic clay whose main component is kaolinite.

〔Example〕

The specific content of the present invention will be explained in more detail with reference to the drawings and examples.

Real length U As a silicate raw material, low-grade pottery stone (sample: A) from Fukui Prefecture was ground to 44 μm or less and used. The chemical composition of this chinastone powder is shown in Table 1, and the mineral composition is shown in the powder X-ray diffraction diagram in FIG.

CaO/SiO□181□ Add slaked lime to the above pottery stone powder
Mix 03 moles to 1 to make 4 g, and add the next layer 1
L ■ A waste material of a generally commercially available hydrated silicate lime compound (using the powder of Dinotri), add hydrochloric acid to it to adjust the pH to around 2, and then adjust it to a kaolinite composition ratio in the same way as in Example ■. Aluminum chloride was added to the mixture, the mixture was placed in a Teflon container, and the mixture was subjected to a hydrothermal reaction at 200°C for 48 hours in an autoclave.The obtained powder was very similar to that obtained in Example 2, and contained no impurities. It was a pure white kaolinitic synthetic clay that did not contain any substances.

Weighed 4g of rice husk ash (containing 5iOz 93%) that had been incinerated by heating at 550°C for 3 hours in an electric furnace, and added 15.2mN of a 2M aqueous aluminum chloride solution to adjust the pH.
After adjusting to around 2, add water to make the raw material to water ratio 1:4.
Place in a Teflon container and place in an autoclave for 23 hours.
Hydrothermal treatment was performed at 0°C for 96 hours. The thus obtained treated product was a white fine powder whose main component was kaolinite.

Furthermore, water was added so that the ratio of raw materials to water was 1:4 by weight, and the mixture was placed in a stainless steel container and heated in an autoclave for 18 hours.
A hydrothermal reaction was carried out at 0°C for 12 hours.

The thus obtained treated product was dehydrated by suction using a Buchner funnel and dried at 100°C (sample B). As shown in the powder X-ray diffraction diagram of No. 1V, most of this powder was converted into a hydrous silicate lime compound (in this case, the product was 11-nin tobermorite), and no free quartz remained.

Next, hydrochloric acid was added to this to make the pII around 2, and then an appropriate amount of 2 mol aluminum chloride aqueous solution was added so that the kaolinite composition ratio (Al/Si atomic ratio -1) was added, and the mixture was placed in a Teflon container and heated to 230°C. A hydrothermal reaction was carried out for 48 hours. Then, this processed material is separated into solids and liquid using a centrifugal separator.
(Sample C). This powder is pure white and, as shown in Table 1 and Figure 1, has a high content of Al2O,L and kaolinite, and is a high-quality kaolinite compound that does not contain any impurities such as free quartz, microcline, or mica. It was confirmed that it was clay.

*This data is a norm calculation value using the Geological Survey method.

[Effects of the present invention]

As described below with reference to the secondary flow side, the present invention provides the following effects.

(1) When using conventionally well-known raw materials for kaolinitic synthetic clay, in order to produce clay of a specified quality, not only did the reaction require high temperatures and long periods of time, but it also became amorphous or low-crystalline. However, in the present invention, the range of selection of raw materials was extremely limited, as in addition to having to carefully select and use quality parts, highly reactive and highly pure reagents had to be used. In addition to being able to use most silicates and aluminosilicates, such as highly crystalline and refractory raw materials and low-grade raw materials with many impurities, commercially available hydrous silicate-lime compounds and even their waste materials can be used. The selection range of raw materials is greatly expanded, and raw material costs can be extremely reduced.

(2) In the method of the present invention, the hydrothermal treatment conditions are relatively low temperature, and the treatment can be performed for a short time.

[Brief explanation of the drawing]

Figure 1 shows low-grade pottery stone (sample A) as a starting material, a hydrated silicate lime compound (sample B) obtained by hydrothermally treating it as in Example This is a powder X-ray diffraction sample measured under the same conditions to compare and explain the formation state with C). K-m-kaolinite, M--monoclinite, Q--monoquartz, S-sericite, T--11 tobermorite, P--monoslaked lime.

Claims (2)

[Claims] (1) Add quicklime or slaked lime to various silicate raw material powders.
aO/SiO_2+Al_2O_3 molar ratio is 0.5 to 2
．． Mix it so that it is in the range of 0, add water to this and make it 15
A kaolinitic synthetic clay characterized by generating a hydrated silicate-lime compound through a hydrothermal reaction at 0°C or higher, and then changing the hardly reactive quartz into easily reactive silicic acid by exposing it to an acidic atmosphere. Method for producing raw materials for use. (2) A kaori characterized by producing a powder whose main component is easily reactive amorphous silicic acid by burning and ashing the rice husks of grass plants in an oxidizing atmosphere at 500 to 900°C. A method for producing a raw material for night synthetic clay.