JPS62867B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing calcium silicate or a calcium silicate-gypsum composite having a petal-like aggregate structure and having a very large bulk volume and oil absorption amount from gypsum and an alkali silicate. Research on production methods for calcium silicate has been conducted for a long time, and in particular, there has been much research on tobermorite and zonotrite for use as building materials. The present inventors first developed an alkali silicate (sio ₂ /R ₂ O (where R is
Na or K) in a molar ratio of 1.55 to 6.5) and a water-soluble calcium compound at a temperature of 150 to 250°C, and the solvent ratio to calcium silicate is 5 to 5.
The reaction was carried out in a range of 100 parts by weight to form a petal-like aggregate represented by the general formula 2CaO・3siO ₂・nSiO ₂・mH ₂ O (A) (where n and m are positive numbers and n=0.1 to 10). It was discovered that calcium silicate having a petal-like structure (hereinafter simply referred to as petal-like) could be obtained, and this was proposed as Na patent application No. 160031/1983. Calcium silicate represented by the above general formula (A) is diairolite type calcium silicate, that is, 2CaO.
3SiO ₂ 2H ₂ O and amorphous silicon dioxide, nSiO ₂ .
Amorphous silicon dioxide, which is composed of mH ₂ O, is not simply a blended form, but is formed by containing amorphous silicon dioxide when diailolite type calcium silicate is produced. Even if gyrolite-type calcium silicate and amorphous silicic acid are mechanically mixed, the petal-like structure described above cannot be obtained. The shape of this calcium silicate can be confirmed by taking an electron micrograph. Generally 3000~
The petal-like shape and thickness can be clearly seen in the 10,000x electron micrograph. The size, shape, etc. of petals vary depending on the type of raw materials used, raw material mixing ratio, manufacturing conditions, etc., and cannot be absolutely limited, but generally the average diameter in the longitudinal direction is 0.1 to 30μ, and the thickness is 0.005 to 0.1
Many of them are circular or elliptical in shape, with many of them resembling the petals of a rose flower. However, Japanese Patent Application No. 160031 (Sho 52-160031)
29643) is a petal-like compound, that is,
It is made up of aggregates in which flakes grow not in a fixed direction but in multiple directions. Patent Application No. 52-160031 (Japanese Patent Publication No. 60-29643) was characterized by the use of a water-soluble calcium compound as a raw material, but this time, gypsum, which is water-soluble but relatively sparingly soluble, was used as a raw material. It was discovered that a petal-shaped calcium silicate-gypsum complex similar to that shown by the above formula (A) can be obtained by selecting the addition order and addition conditions even when using a calcium compound of It came to this. The present invention uses an alkali silicate (SiO ₂ /R ₂ O (where R is Na or K) molar ratio 1.55 to 6.5) (hereinafter also simply referred to as an alkali silicate) in a gypsum suspension.
A method for producing calcium silicate with a petal-like aggregate structure or a calcium silicate-gypsum composite with a petal-like aggregate structure, which comprises gradually adding a solution and heat-treating the mixture under pressure at a temperature of 150 to 250°C. . What is important in the present invention is to add the alkaline silicate solution to the gypsum suspension and to do this addition as gradually as possible. Under these considerations, when the molar ratio of gypsum/alkali silicate is around 1, a petal-shaped calcium silicate is mainly obtained, and when the molar ratio is 1.1 to 1.5, a petal-shaped calcium silicate-gypsum composite is obtained. The alkali silicate used as the raw material for the present invention is theoretically
The SiO ₂ /CaO molar ratio is in the range of 1.55 to 6.5. The SiO ₂ /CaO molar ratio here refers to excess gypsum CaO.
is not included. As mentioned above, the molar ratio of SiO ₂ /CaO can be controlled by controlling the type of raw materials, reaction temperature, reaction time,
This will vary slightly depending on the water ratio, etc., so please prepare the amount in the product in advance.
SiO ₂ /CaO molar ratio and SiO ₂ / in raw material preparation
It is preferable to confirm the relationship with the CaO molar ratio before use. The general formula shows that as the molar ratio of SiO ₂ /CaO in calcium silicate increases, depending on the formation conditions, amorphous 2
Since silicon oxide may form a spherical shape, it is necessary to prepare a suitable SiO ₂ /
It is preferable to predetermine the CaO molar ratio. As the alkali silicate used as a raw material in the above, it is preferable to use one represented by the following formula R ₂ O·lSiO ₂ (R is Na or K, l is 1.5 to 6.5), and gypsum and the alkali silicate The usage ratio of gypsum/alkali silicate is 1.0.
A range of ~1.5 is advantageous. In the present invention, first, gypsum is placed in water and stirred thoroughly to form a slurry. As will be explained later, the slurry concentration at this time is preferably lower. However, if the concentration is set too low and water is added at least 100 times the weight of the finally obtained calcium silicate, the obtained calcium silicate cannot become petal-shaped, which is not preferable. An alkali silicate such as sodium silicate or potassium silicate or an aqueous solution thereof is gradually added to this slurry, generally under atmospheric pressure, to form a slurry. What is important here is the addition time, and it is preferable to add as slowly as possible. The amount of time required is not absolutely limited depending on the particle size, crystal shape, etc. of the gypsum, but it is generally best to add as much time as possible, at least 10 minutes. If the addition time of the alkali silicate is too short, it is difficult to form a calcium silicate or a calcium silicate-gypsum complex having a petal-like structure and a high bulk specific volume, which is undesirable because it tends to become lumpy. It is currently not clear why the addition time of alkali silicate is important, but although gypsum has a low solubility, its dissolution rate is relatively high, and as soon as slightly dissolved gypsum and alkali silicate react, Since new gypsum is dissolved in the process, we believe that if the addition time is long enough, the result will be the same as reacting a highly water-soluble calcium compound with an alkali silicate. On the other hand, if the addition time is too short, the reaction between the alkali silicate and the gypsum will occur on the gypsum solid, and the resulting gypsum will become very non-uniform and cannot form a petal shape. Furthermore, the order of addition of the above-mentioned raw material components is also important, and if the order is reversed, that is, when an aqueous slurry of gypsum is added to an alkali silicate or its aqueous solution, the resulting calcium silicate is unlikely to be petal-shaped. That is, when a gypsum slurry is added to an alkali silicate, most of the resulting calcium silicate tends to be lump-like rather than petal-shaped even if the addition rate is sufficiently slow. Next, by reacting the mixture of the gypsum slurry and the alkali silicate under pressure at 150 to 250°C using, for example, an oaklave, the desired calcium silicate or calcium silicate-gypsum composite can be obtained. In the present invention, the petal-shaped calcium silicate or calcium silicate monogypsum complex can be obtained by separating it from the solvent, but it can also be purified by washing with water if necessary. The petal-shaped calcium silicate thus obtained may be dried in a conventional manner and used as it is or, if necessary, pulverized to form a product. In the present invention, when obtaining calcium silicate, the molar ratio of gypsum/alkali silicate may be selected to be around 1, and when obtaining a calcium silicate-gypsum composite, the molar ratio is 1.1 to 1.5. Just choose it so that it falls within the range of . Common sense says that the molar ratio is
If the value is greater than 1.0, the chemical reaction equation suggests that the excess gypsum will not participate in the reaction at all, but surprisingly, the excess gypsum does not act as a mere impurity in the obtained calcium silicate. , microblended in calcium silicate to form a calcium silicate-gypsum complex, 10,000
It became impossible to distinguish between calcium silicate and gypsum even under a magnified electron microscope, and it was found that the bulk specific volume and oil absorption were extremely large. The mechanism of action behind this phenomenon is not clear, but even if calcium silicate is first synthesized and then gypsum is added and hydrothermally treated in an autoclave, such a composite will not work. Considering that it was not obtained, we speculate that gypsum may be involved in some way during the crystal growth of calcium silicate. However, when the molar ratio exceeds 1.6, gypsum and calcium silicate can be clearly distinguished even under a microscope. The calcium silicate-gypsum composite obtained as described above exhibits excellent performance when used as an adsorption carrier, a matting agent, a filter aid, etc., similar to the petal-shaped high bulk specific volume calcium silicate described above. do. EXAMPLES In order to explain the present invention in more detail, Examples and Comparative Examples will be given below, but the present invention is not limited to these Examples. In addition, various measured values in the following Examples and Comparative Examples were determined as follows. (a) Bulk specific volume Calcium silicate was ground in a mortar to a particle size that could pass 80% through a 200 mesh sieve. The pulverized calcium silicate was used to measure bulk specific gravity according to JIS K6220 Section 6.8. (b) Oil absorption amount Calcium silicate was ground in a mortar to a particle size that could pass 80% through a 200 mesh sieve. The pulverized calcium silicate was used to measure oil absorption according to JIS K6220, item 19. Example 1 4.56g of B type hemihydrate gypsum (100 meshes) was 98
Pour into cc water and stir for 20 minutes. While stirring the slurry, 100 c.c. of 0.3144 mol/l sodium silicate (SiO ₂ /Na ₂ O molar ratio 2.6) was added at a rate of 5 c.c./min over 20 minutes at 25° C. under atmospheric pressure. Ta. In this case, the charged CaSO ₄ /Na ₂ O·nSiO ₂ molar ratio was 1.00. The resulting slurry was placed in an autoclave, sealed and reacted at 200°C for 5 hours. The reaction product was filtered, washed twice with 100 c.c. of ion-exchanged water, and then dried at 100°C for 8 hours. The yield of this dry product was 7.35g. The bulk specific volume was 21 cc/g, and the oil absorption was 6.3 cc/g. Furthermore, the result of X-ray diffraction showed a pattern of diairolite type calcium silicate. The results of chemical analysis were: CaO2 4.4%, SiO ₂ 66.2%, loss on ignition 9.4%. From this result, it was found that the calcium silicate obtained in the above operation was 2CaO.3SiO ₂ .2.06SiO ₂ .2.39H ₂ O. Figure 1 shows an electron microscope photo taken at 10,000 times magnification, and it was confirmed that the petal was composed of an aggregate of petals with an average longitudinal diameter of about 2u and a thickness of less than 0.1μ. Example 2 6.5 g of dihydrate gypsum (100 meshes) is poured into 98 c.c. of water and stirred for 20 minutes. While stirring this slurry, 100 c.c. of 0.3144 mol/l sodium silicate (SiO ₂ /Na ₂ O molar ratio 2.6) was added to 6 c.c./l at 25°C under atmospheric pressure.
The mixture was added over a period of 16 minutes and 40 seconds at a rate of 1 minute. In this case, the charged CaSO ₄ /Na ₂ O·nSiO ₂ was 1.34. The subsequent operations were carried out in the same manner as in Example 1 to obtain 8.2 g of powder. The results of X-ray diffraction of this powder showed a mixture of peaks of anhydrite-type anhydrite and gyrolite-type calcium silicate. From the results of chemical analysis, (2CaO・
3SiO ₂ .2.05SiO ₂ .2.37H ₂ O) (0.20CaSO ₄ ). Figure 2 shows a photograph taken with an electron microscope at 10,000 times magnification, and it was confirmed that the flower was composed of petals with a diameter of 2μ in the longitudinal direction and a thickness of 0.1μ or less.
It should be noted that crystals that appeared to be type anhydrite could not be visually identified. Bulk specific volume is 19.5cc/g oil absorption
It was 63.2cc/g. Example 3 Same as Example 1 except that the amount of B-type gypsum hemihydrate, SiO ₂ /CaO molar ratio of sodium silicate, concentration, autoclave reaction temperature and reaction time were changed as shown in Table 1. Treated in the same way. Preparation
Both CaSO ₄ /Na ₂ O and nSiO ₂ were 100.
In each case, it was confirmed by X-ray diffraction, electron microscopy, and chemical analysis that it was petal-shaped calcium silicate. The results are also shown in Table 1.

[Table] Example 4 The second test was conducted in the same manner as in Example 2, except that the amount of dihydrate gypsum in Example 2 was changed as shown in Table 2.
The results shown in the table were obtained. According to observation using an electron microscope at a magnification of 10,000 times, it was confirmed that No. 3, No. 4, and No. 5 contained a mixture of petal-like materials and plate-like anhydrite.
In No. 1 and No. 2, there were only petal-like objects, and the substance that appeared to be plaster could not be identified.

[Table] Example 5 The same procedure as in Examples 1 and 2 was carried out except that potassium silicate was used instead of sodium silicate in Examples 1 and 2. The results of chemical analysis X-ray diffraction and electron microscopy were almost the same as those of Examples 1 and 2, and the results obtained in the same manner as in Example 1 were 2CaO・3SiO ₂・2.05SiO ₂・2.33H ₂ A petal-like object with a length of 2μ in the longitudinal direction, denoted by O, was prepared in the same manner as in Example ₂ .
It was confirmed that it was a petal-like substance made of a calcium silicate-gypsum complex represented by 2.05SiO ₂ .2.34H ₂ O) (0.20CaSO ₄ ). Comparative Example 1 1.45 g of a-type gypsum hemihydrate (CaSO ₄ 1/2 H ₂ O) was mixed with 0.2 mol/l of sodium silicate (sodium silicate ratio
2.6) Add to aqueous solution 50c.c. and autoclave 200
The reaction was carried out at ℃ for 20 hours. The obtained result is shown in Example 1.
It was dried in the same manner. An electron micrograph (10,000 times magnification) of this material revealed that it was a mass of particulate matter as shown in FIG. That is, it is clear that it is completely different from the calcium silicate of the present invention shown in FIGS. 1 and 2.

[Brief explanation of the drawing]

Figure 1 is an electron micrograph (10,000 times) of the calcium silicate of the present invention, Figure 2 is an electron microscope photograph (10,000 times) of the calcium silicate-gypsum composite of the present invention, and Figure 3 is a comparative example. This is an electron micrograph (10,000 times magnification) of the calcium silicate shown.

Claims (1)

[Claims] 1. Calcium silicate or calcium silicate with a petal-like aggregate structure characterized by gradually adding an alkaline silicate solution to an aqueous suspension of gypsum and hydrothermally treating the mixture under pressure at a temperature of 150 to 250°C. A method for producing a calcium silicate-gypsum composite with a petal-like aggregate structure. 2. The method according to claim 1, wherein the alkali silicate is sodium silicate. 3. The method according to claim 1, wherein the reaction is carried out at a molar ratio of gypsum/alkali silicate in the range of 1.0 to 1.5.