JPS6247807B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a fibrous mineral material made of crystalline hosiyayite 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, hosiyayite is a substance that can be synthesized relatively easily using silicate raw materials and calcareous raw materials, and the raw materials are abundant in Japan and can be obtained at low cost, and its characteristics are similar to those of calcium silicate. Because it is mainly mineral, it has excellent insulation properties,
It also has excellent affinity with water, and several attempts have been made to make fibers from its composites.

For example, we added alkali and other various additives to the three-component system of CaO--SiO ₂ -- H ₂ O, and considered the temperature, pressure, time, composition, etc., but unless we made the hydrothermal reaction conditions harsh, it would take a long time for the hydrothermal reaction to occur. It was not possible to make textile materials.

Hoshiyaite, which can currently be produced industrially, is
Since it is a fine crystal with a crystal length of several μm and tends to aggregate, it has the disadvantage of high overresistance.

The present inventors added an alkali metal hydroxide to amorphous calcium silicate hydrate and caused a hydrothermal reaction to produce monofilamentous crystalline hosiyayite with a crystal length of 50 μm or more and a crystal diameter of 5 μm or less. It is possible to produce a fibrous mineral material mainly composed of They discovered that it can also be used as a filler and reinforcing material, and completed the present invention.

Amorphous calcium silicate hydrate-containing materials include concrete, mortar, Slurry, autoclaved aerated concrete, etc., CaO-
It refers to a SiO ₂ --H ₂ O-based substance, and a CaO/SiO ₂ molar ratio of 0.8 to 1.3 is sufficient for the starting material containing calcium silicate hydrate.

Alkali metal hydroxides are lithium hydroxide,
It refers to alkaline substances such as sodium hydroxide and potassium hydroxide, and an alkaline concentration of 0.05 to 2 normal is sufficient.

The amount of the alkaline aqueous solution present in the hydrothermal reaction system is preferably at least an amount that exhibits fluidity when mixed with the calcium silicate hydrate-containing material as a starting material and the alkaline aqueous solution. It is sufficient to use at least 5 parts by weight, preferably 10 parts by weight or more of the alkaline aqueous solution per 1 part by weight of calcium silicate hydrate.

In this invention, the hydrothermal reaction used to form the fibrous hosiyayite crystals is carried out at a temperature of 200°C or higher and under saturated steam pressure (the critical temperature of saturated steam is 374°C due to the physical properties of water), preferably around 240°C. .

After the completion of the hydrothermal reaction, the solid content of fibrous hosiyayite crystals is taken out from the autoclave as a slurry suspended in water and separated separately, and the dried product is in the form of bulky white powder or flakes and water is removed from the autoclave. It is a fibrous mineral material that easily penetrates. This fibrous mineral material is a highly pure hosiyayite 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 long fibrous material with a length of 50 μm or more, it can be used as a filler with a reinforcing effect, as a catalyst carrier, as a filter material, as an adsorbent, etc.

Example 1 The starting materials containing calcium silicate hydrate were diatomaceous earth (SiO ₂ = 90%), slaked lime (CaO = 73%),
%, Blaine value 800cm ² /g) was prepared so that the CaO/SiO ₂ molar ratio = 1.3 and the water/total solids weight ratio = 10, and after pouring into an autoclave, it was heated at 120°C under saturated water vapor pressure for 1 hour. The mixture was stirred and left to stand for 2 hours to obtain a slurry.

An X-ray diffraction diagram of this substance is shown in FIG. 1, a differential thermal analysis diagram is shown in FIG. 2, and a scanning electron micrograph is shown in FIG. As seen in Figures 1-3, this material was an amorphous calcium silicate hydrate, commonly referred to as a C--S--H gel.

10 parts by weight of the solid content of this three and 90 parts by weight of a 2N aqueous potassium hydroxide solution were placed in a silver-lined autoclave, and allowed to stand for 3 days under saturated steam pressure at 230 to 260°C to undergo a hydrothermal reaction.

After the completion of the hydrothermal reaction, the solid fibrous hosiyayite crystals are suspended in water in the form of a slurry and taken out from the autoclave, separated and dried to form a bulk of 10 parts by weight of crystalline hosiyayite crystals with a crystal length of 50 μm or more and a crystal diameter of 5 μm or less. A high fiber mineral material 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 Figures 4 to 6,
This material was mostly crystalline hosiyayite with a crystal length of 50 μm or more.

In addition, as seen from the results of differential thermal analysis, approximately
There is almost no weight loss up to 640℃, and the weight loss is only 4.5% at about 800℃, indicating that it has excellent heat resistance and is also excellent as a filler and reinforcing material for synthetic resin molded products.

Furthermore, since it is a highly crystalline hoshyajite, it can be transformed into wollastonite without damaging its crystalline form through topotactics, and it is found to have excellent heat-resistant dimensional stability.

The measurement conditions for X-ray diffraction are as follows: anticathode Cu
(Ni), tube voltage 15mA, full scale counting
1000cps, time constant 2 seconds, scanning speed 2θ degrees/minute,
Recording speed 2cm/min, divergence slit/mm, receiving slit 0.3mm.

The measurement conditions for differential thermal analysis are: sample weight 10 mg;
DTA range ±100μV, heating rate 10℃/min.

The measurement conditions of the scanning electron microscope were gold evaporation, magnification 1
It's ten thousand times more.

[Brief explanation of the drawing]

Figure 1 is an X-ray diffraction diagram of calcium silicate hydrate, Figure 2 is a differential thermal analysis diagram of the same hydrate, Figure 3 is a scanning electron micrograph of the same hydrate, and Figure 4 is a book. FIG. 5 is an X-ray diffraction diagram of the invention crystalline hosiyayite, FIG. 5 is a differential thermal analysis chart of the same hosiyayite, and FIG. 6 is a scanning electron micrograph of the same hosiyayite.

Claims (1)

[Claims] 1. A 0.05 to 2 N aqueous solution of an alkali metal hydroxide is added to a hydrated amorphous calcium silicate with a CaO/SiO ₂ molar ratio of 0.8 to 1.3, which is produced using calcareous substances and silicic substances as raw materials. Add at least 5 parts by weight per 1 part by weight of calcium hydrate,
1. A method for producing a fibrous hoshyayite mineral material, which comprises producing fibrous crystalline hoshyayite having a crystal length of 50 μm or more through a hydrothermal reaction at a temperature of 200° C. or higher and a saturated steam pressure.