JPS59169923A - Xonotlite-type calcium silicate and its preparation - Google Patents

Abstract

PURPOSE:To prepare a xonotlite-type calcium silicate having high crystallinity, by adding powdery lime material stepwise to a powder silicate material to effect the multi-stage batch-wise hydrothermal reaction, while specifying the ratio of CaO/SiO2 in the first-stage reaction. CONSTITUTION:A powdery silicate material is subjected to the hydrothermal reaction with a powdery lime material at a CaO/SiO2 molar ratio of 0.9-1.5. The above reaction is carried out batchwise in multistages by dividing the powdery lime material into two or more parts, and adding the material stepwise to the system. The molar ratio of CaO/SiO2 in the first-stage reaction is selected to be <=0.6, and the reaction is carried out usually at 40-200 deg.C for 3-10hr. The process yields a xonotlite-type calcium silicate having collected acicular crystal form, high crystallinity, improved physical properties such as chemical resistance as formed article, and high specific surface area in powdery state.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a crystalline xonotrite-based calcium silicate obtained by hydrothermally reacting a powdery silicic acid raw material and a powdery calcareous raw material, and a method for producing the same. Zonotlite-based calcium silicate (hereinafter referred to as "Zonotlite") is
It has superior heat resistance compared to the topamolye type, and is used as a high-temperature membrane heating material for industrial purposes and as a fire-resistant coating material for construction.

The method for producing Nnotrite is, for example, a mixture of a powdered siliceous raw material and a powdered calcareous raw material at a Can/5iOz molar ratio of -0.9 to 1.5, which is then subjected to a hydrothermal reaction in an autoclave. I was letting it happen. However, when the xonotlite obtained by this method is observed in an electron micrograph, it has a sword-like scattered crystal morphology, as shown in Figure 1, and its crystallinity is low, and in the molded state, it has poor chemical resistance. In addition, there was a problem that a product with a large specific surface area could not be obtained in a powder or granule state.

In view of the above, the present invention provides a novel crystal form of xonotlite that has a high degree of crystallinity, improves physical properties such as chemical resistance in a molded state, and has a small specific surface area in a granular state, and the production thereof. The purpose is to provide a method.

The gist of the first invention resides in xonotlite, which is characterized in that the crystal form is an acicular focused type, and the gist of the second invention is as follows:
Each unit of the powdered calcareous raw material divided into two parts or more is added stepwise to the powdered siliceous raw material to carry out the hydrothermal reaction in a multi-stage patch manner, and the first stage reaction of the hydrothermal reaction is carried out in a multi-stage patch manner. The method for producing xonotlite is characterized in that the molar ratio of CaO/5i02 is 0.6 or less.

The present invention will be explained in detail below.

Examples of the powdered silicic acid raw material used for the xonotlite of the present invention include various silica powders, diatomite powder, white carbon, ferrosilicon dust, silica, etc.
Examples of powdery calcareous raw materials include slaked lime, quicklime, and calcined F lomite.

Here, the particle size of each raw material is preferably 250 mesh (63 m) or less for the silicic acid material and 100 mesh (49 m) or less for the calcareous material from the viewpoint of the mixability and reactivity of the powder phase 77-. . Further, when powdering these raw materials, a pulverizer such as a roller mill or a vibrating ball mill, which is commonly used for pulverizing minerals, etc., is used.

L: Powdered silicic acid raw material, powdered calcareous raw material, and Cab/Si
The hydrothermal reaction is carried out at a molar ratio of 0.9 to 1.5. In the method of the present invention, each unit of the powdery calcareous raw material, which is divided into two or more parts, is divided into stages □ In addition to the steps, it is also done in a multi-stage/Hetsch style. At this time, the CaO/5i02 molar ratio in the first stage reaction is 0.6 or less (usually 0.6 or less).
5 to 0.01), and the reaction conditions are usually 140 to 200°C.
Let it be X3-10h. CaO/5i02 molar ratio is 0.6
If this value is exceeded, the reaction in the entire reaction system in the first stage becomes slow, and even if the hydrothermal reaction in the second stage and subsequent stages described below is carried out, it tends to result in the monotonous crystal form of the conventionally known four-shaped interspersed type.
The acicular focusing type xonotlite of the present invention cannot be obtained. Here, the term "acicular focused crystal" refers to a crystal in the form shown in FIG. 2 when observed by electron micrograph. For the subsequent hydrothermal reactions in the second and subsequent stages, each grade of the remaining powdery calcareous raw material is added to the reaction product of each previous stage (if it is not in powder form, use the above-mentioned known pulverizer to make it 250 mesh or less). The reaction conditions are higher temperature and longer time than the previous stage (especially in the final stage reaction), usually 180 to 230° OX for 5 to 15 hours.

In addition, in order to uniformly mix the first-stage reaction product and each unit of the calcareous raw material, the V-type mixer 1. nauta mixer,
It is preferable to use a known blender such as a ribbon mixer. The number of stages for each of the above hydrothermal reactions is not particularly limited, but is usually 2 to 3 stages, and the hydrothermal reactions are usually carried out by introducing high temperature and high pressure saturated steam into an autoclave.

When the xonotlite of the present invention thus obtained is observed by electron micrograph, the crystal morphology is needle-like focused type (Fig. 2), and the crystallinity is higher than that of the conventional needle-like scattered type (Fig. 1). The chemical resistance and other physical properties in the molded state are significantly improved, and a powdery IF with a relatively large specific surface area can be obtained. Therefore, in addition to being used as heat insulating materials and fireproof coating materials in the molded state, it is expected to be used in a wide range of applications, including as aggregate in the powdered form, fillers for paints, plastics, paper, etc., and as various adsorbents. be.

In addition, in the crystal form y fish that was reacted and produced under the conditions shown in Table 1 or observed in electron micrographs,
Both Examples 1 and 2 were of the needle-like focusing type, whereas Comparative Examples 1 and 2 were both of the needle-like focusing type. Furthermore, Table 1 shows the results of measurements by the BET absorption method for each of the obtained xonotlites having an average particle diameter of 30 gm. It can be seen that the specific surface areas of the Examples are all larger than those of the Comparative Examples.

Table 1 X-O I Crepe Live Bait 11 Steam

[Brief explanation of the drawing]

Fig. 1 is an electron micrograph (x2000x) of the sonodrite of Example 1, and Fig. 2 is an electron micrograph (x2000x) of the xonotlite of Comparative Example 1.
Applicant: “Ij Masayoshi Ki”

Claims (1)

[Scope of Claims] ] A crystalline xonotrite calcium silicate obtained by hydrothermally reacting a powdered silicic acid raw material and a powdered calcareous raw material, characterized in that the crystalline form is an acicular focused type. Xonotrite type calcium silicate. 2. Powdered silicic acid raw material and powdered calcareous raw material are mixed with CaO/S
fjJ by hydrothermal reaction at iO2 molar ratio = 0.8 to 1.5
In the method for producing crystalline tunodried calcium silicate, each middle part of the powdered calcareous raw material divided into two parts or more is added stepwise to the powdered silicic raw material to form a multistage patch. 1. A method for producing a tunodolide calcium silica, characterized in that the hydrothermal reaction is carried out according to the above formula, and the Can/5iOz molar ratio in the first stage reaction of the hydrothermal reaction is -0, 6 or less.