JPS6247808B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a xonotrite-based fibrous mineral material having a crystal length of 50 μm or more.

Conventionally, asbestos has been a typical inorganic fiber, and it has long fiber length and is of high industrial significance, but as it is naturally occurring, it is predicted that it will be depleted in the future, and in recent years It is suspected of being a carcinogen, and has come to be considered an undesirable material from the standpoint of environmental conservation. Glass fiber and rock wool, which are commonly known inorganic fibers other than asbestos, are used as heat insulating materials, but because they have poor alkali resistance, they are not necessarily versatile as fillers and reinforcing materials. Furthermore, although ceramic fibers have various excellent properties, they are too expensive and cannot be put to practical use as general-purpose industrial materials such as reinforcing materials and fillers.

On the other hand, xonotlite is a substance that can be synthesized relatively easily using silicic acid raw materials and calcareous raw materials, and its raw materials such as silica stone, silica sand, and limestone are abundant in Japan and can be obtained at low cost. Since it is a mineral mainly composed of calcium silicate, it has excellent heat insulation properties and has an excellent affinity with water, and several attempts have been made to make fibers from its composite. For example, CaO―SiO ₂ ―
Although we added alkali and various other additives to the ternary H ₂ O system and investigated temperature, pressure, time, composition, etc., we were unable to make a long fibrous material from xonotlite. Normally, industrially obtained xonotlite fibers are fine, on the order of several micrometers, and are cohesive, so they have the disadvantage of increased overresistance.

As a result of intensive research, the present inventors have invented a method for producing a xonotrite-based fibrous mineral material, which is a crystalline xonotrite and has a crystal length of 50 μm or more and a crystal diameter of 5 μm or less.

In the present invention, a 0.05 to 1 N aqueous solution of an alkali metal hydroxide is added to a calcium silicate hydrate-containing product with a CaO/SiO ₂ molar ratio of 0.8 to 1.0, which is produced using calcareous substances and silicic substances as raw materials. At least 5 parts by weight of a tobermorite-based calcium silicate hydrate-containing porous material is added to 1 part by weight of calcium hydrate, and the mixture is subjected to a hydrothermal reaction under saturated steam pressure at 150°C or higher to form crystals with a crystal length of 50 μm or more. This is a method for producing a xonotlite-based fibrous mineral material that produces crystalline xonotrite with a diameter of 5 μm or less.

The xonotrite-based fibrous mineral material obtained by the present invention has excellent properties such as a bulk density of 0.1 to 0.2 and good transient properties, so it can be used not only as a heat-resistant material but also as a filler and reinforcing material for synthetic resin molded products. is also a material that can be used.

Calcium silicate hydrate-containing materials produced from calcareous materials and silicic materials used as starting materials in the present invention are obtained by curing silicic materials and calcareous materials under saturated steam pressure at room temperature to high temperature and high pressure. Concrete, mortar, slurry, autoclave-cured aerated concrete CaO-SiO ₂ -H ₂ O-based substances containing calcium silicate hydrate as a starting material.
CaO/ _SiO2 (molar ratio) is 0.8-1.0.

Alkali metal hydroxides are lithium hydroxide,
It refers to alkaline substances such as sodium hydroxide and potassium hydroxide, and is an aqueous solution with an alkaline concentration of 0.05 to 1N. The amount of the alkaline aqueous solution to be present in the hydrothermal reaction system is preferably at least an amount that exhibits fluidity when mixed with the alkali aqueous solution and the content of calcium silicate hydrate as a starting material. About 5 parts by weight, preferably 10 parts by weight or more, of the alkaline aqueous solution is used per 1 part by weight of the content of calcium silicate hydrate.

The hydrothermal reaction used to form the fibrous xonotrite crystals in this invention is carried out at a temperature of 150°C or higher under saturated steam pressure (the critical temperature of saturated steam is 374°C due to the physical properties of water), preferably around 240°C.

A porous material containing tobermorite-based calcium silicate hydrate is a material that does not dissolve even when impregnated with an alkaline solution and subjected to a hydrothermal reaction, has sufficient voids for crystal growth of fibrous xonotlite, and does not inhibit crystal growth. Refers to porous materials such as autoclaved lightweight cellular concrete.

After the completion of the hydrothermal reaction, the solid content of fibrous xonotrite crystals is taken out of the autoclave as a slurry suspended in water and separated separately.
The dried material is a white powder or flake-like fibrous mineral material with a bulk specific gravity of 0.1 to 0.2 that easily permeates water. This fibrous mineral material is a highly pure xonotlite with excellent crystallinity, as shown in the X-ray diffraction diagram in the examples described later, and has excellent heat resistance and alkali resistance. Since it is a relatively long fibrous material of 50 μm or more, it can be used as a filler with a reinforcing effect in catalyst carriers, filter materials, adsorbents, etc.

Example 1 (A) The starting material, calcium silicate hydrate, was diatomaceous earth (SiO ₂ = 90%), slaked lime (CaO = 73%,
(Brain value 8000cm ² /g) was prepared so that CaO/SiO ₂ (mole ratio) was 1.0 and water/total solids (weight ratio) = 10, poured into an autoclave, and stirred for 1 hour at 120°C under saturated steam pressure. (100 rpm) for 2 hours to obtain a slurry.

The X-ray diffraction diagram of this substance is shown in Figure 1, the differential thermal analysis diagram is shown in Figure 2, and the scanning electron micrograph is shown in Figure 3.
As shown in the figure.

As is clear from Figures 1 to 3, this substance is an amorphous calcium silicate hydrate, usually C-
It was called S--H gel.

(B) The porous materials of tobermorite-based calcium silicate hydrate containing materials are silica (SiO ₂ = 95%, Blaine value 3000cm ² /g), cement (ordinary Portland cement SiO ₂ = 22%, CaO 65%, Blaine value 3000cm ² /g), quicklime (CaO = 95%, Blaine value 6000cm ² /g) and CaO/SiO ₂ (molar ratio) =
0.7, cement/quicklime (weight ratio) = 3, metal aluminum (particle size 30 μm or less)/total solids (weight ratio) = 0.001, and after kneading, inject into a mold and mold it, then autoclave. It was prepared by curing for 10 hours at 180°C under saturated water vapor pressure. The X-ray diffraction diagram of this molded body is shown in FIG. As is clear from FIG. 7, this material was mainly composed of plate-shaped crystalline tobermorite with a width and length of 1 to 5 μm, and some unreacted quartz remained. Also, this substance has a bulk density
0.5, and the pore volume by mercury intrusion method was 0.8 cm ² /g.

(C) Solid content of 5 parts of the calcium silicate hydrate slurry prepared in (A) above, and 2 parts of the porous material of the tobermorite-based calcium silicate hydrate-containing slurry prepared in (B) above, which was roughly crushed and classified. ~5 parts of 5 mm and
90 parts of a 0.5N potassium hydroxide aqueous solution was placed in a silver-lined autoclave and the vacuum level was 50.
After degassing for 30 minutes at less than mmHg and impregnating with an alkaline aqueous solution, it was left to stand for 2 days under saturated steam pressure at a temperature of 210°C to 230°C to allow a hydrothermal reaction, and then the soul of the porous material was separated using a 1 mm sieve. I got it. Crystal length is 50μm or more and crystal diameter is 5μm by hydrothermal synthesis.
5 parts by weight of crystalline xonotlite produced below,
A fibrous mineral material with a high bulk was obtained. An X-ray diffraction diagram of this substance is shown in FIG. 4, a differential thermal analysis diagram is shown in FIG. 5, and a scanning electron micrograph is shown in FIG.
As is clear from FIGS. 4 to 6, the products of the present invention were mostly fibrous minerals mainly composed of crystalline xonotrite with a crystal length of 50 μm or more and a crystal diameter of 5 μm or less.

This fibrous mineral had a bulk density of 0.13 to 0.18 and low hyperresistance, so it could be used as a filler.

Note that the measurement conditions for X-ray diffraction in (A), (B), and (C) of Example 1 are anticathode Cu (Ni), tube voltage 30 KV, and tube current.
15mA, full scale counting 1000cps, time constant 2
scanning speed 2 degrees/min, recording speed 2 cm/min, divergent slit 1 mm, receiving slit 0.3 mm, and the same measurement conditions for differential thermal analysis are sample weight 10 mg,
DTA range: ±100μV, heating rate: 10°C/min; measurement conditions for the scanning electron microscope are gold deposition and 10,000x magnification.

Example 2 As a result of repeating the method of Example 1 by replacing the 0.5N aqueous potassium hydroxide solution with a 0.05N aqueous sodium hydroxide solution, 5 parts by weight of crystalline xonotlite, most of which had a crystal length of 50 μm or more and a crystal diameter of 5 μm or less, was obtained. Obtained. The material properties of the product of the present invention were similar to those of the product obtained in Example 1.

[Brief explanation of the drawing]

Figure 1 is an X-ray diffraction diagram of a product containing calcium silicate hydrate, Figure 2 is a differential thermal analysis diagram of the same content, Figure 3 is a scanning electron micrograph of the same content, and Figure 4 is a book. An X-ray diffraction diagram of the invention crystalline xonotlite, Figure 5 is a differential thermal analysis diagram of the same xonotlite, Figure 6 is a scanning electron micrograph of the same xonotlite, and Figure 7 is a tobermorite-based calcium silicate hydrate-containing product. X
It is a line diffraction diagram.

Claims (1)

[Claims] 1. Calcium silicate hydrate-containing product with a CaO/SiO ₂ molar ratio of 0.8 to 1.0 produced from calcareous substances and silicic substances as raw materials, and an alkali metal hydroxide.
At least 5 parts by weight of a 0.05 to 1N aqueous solution is added to 1 part by weight of the calcium silicate hydrate, and a porous material containing tobermorite-based calcium silicate hydrate is added, and the mixture is heated hydrothermally at a saturated water vapor pressure of 150°C or higher. A method for producing a xonotrite-based fibrous mineral material, which comprises reacting to produce crystalline xonotrite having a crystal length of 50 μm or more and a crystal diameter of 5 μm or less. 2. The manufacturing method according to claim 1, wherein the porous material of the tobermorite-based calcium silicate hydrate-containing material is autoclave-cured lightweight cellular concrete.