JP3023755B2 - Calcium silicate hydrate compact and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lightweight calcium silicate hydrate compact obtained by a hydrothermal reaction between a calcareous raw material and a siliceous raw material, and a method for producing the same. The calcium silicate hydrate molded article of the present invention has good fire resistance and shape stability, is lighter in weight than conventional products, and has remarkably excellent mechanical strength, and is used as a fire-resistant coating material, fire-resistant heat insulating material, building material, and the like. Useful.

[0002]

2. Description of the Related Art Calcium silicate hydrate compacts are now widely used as refractory coatings and the like, but there is a demand for products having lighter weight and greater mechanical strength. As a method for continuously producing this calcium silicate hydrate,
After an aqueous slurry composed of calcareous raw material and siliceous raw material is preliminarily gelled to 50% or more of the total amount of raw materials, it is continuously fed into a rigid high-pressure reactor, and high-pressure heating water is introduced to carry out hydrothermal reaction. Production methods for obtaining calcium silicate hydrate have been conventionally known (JP-B-54-10956, JP-B-54-10956).
No. 10957).

According to this production method, there is an advantage that a molded body in which crystals of calcium silicate hydrate are uniformly formed can be continuously produced at low cost. However, most of the calcium silicate hydrate produced has crystals similar in shape to sea urchins and chestnut burrs. Is difficult to obtain.

[0004]

The present invention solves problems of the Invention be those in which the above-described problems of the conventional calcium silicate hydrate formed body provides lightweight and high mechanical strength calcium silicate hydrate formed body and a manufacturing method thereof According to the production method of the present invention, it is easy to control the physical properties of the compact .

[0005]

A conventional method for continuously producing calcium silicate hydrate comprises: (a) adding a caustic alkali to an aqueous slurry obtained by adding water to a mixed raw material of a calcareous raw material and a siliceous raw material; (B) a second step of introducing high-pressure heating water into the gelled slurry obtained in the first step to promote a hydrothermal reaction to generate calcium silicate hydrate; (c) a second step Comprises a third step of reducing the pressure of the product slurry obtained in the step, and extracting the slurry by adding caustic alkali to the high-pressure heated water in the second step, whereby the aqueous solution of calcium silicate formed in the high-pressure reaction vessel is reduced. We found a phenomenon in which the crystal shape of the hydrate changed, and as a result, in a slurry of calcium silicate hydrate, crystal particles similar in shape to sea urchin and chestnut iga (hereinafter referred to as iga-like crystals) and wheat ears Crystals with a shape similar to Two different types of crystals are produced, and the burrs are relatively light, unlike the conventional heavy ones, and the mixing ratio makes the mechanical strength of calcium silicate hydrate such as Findings with different physical properties were obtained.

The present invention is based on the above findings, and according to the present invention, a calcium silicate hydrate having the following constitution is provided. (1) a calcareous material and calcium silicate hydrate crystal grains of different shapes of obtained <br/> are Louis moth-like crystals and wheat spikes crystals are mixed by hydrothermal reaction with siliceous material, Molding
A calcium silicate hydrate compact having a bulk specific gravity of 0.3 or less . (2) The calcium silicate hydrate molded article according to the above (1), wherein the ratio of burrs and barley crystals (burrs: barley crystals) is 7: 3: 3-7.

Further, according to the present invention, there is provided a method for producing calcium silicate hydrate having the following constitution. (3) (a) a first step of adding a caustic alkali to an aqueous slurry obtained by adding water to a mixed raw material of a calcareous raw material and a siliceous raw material and heating and gelling, and (b) obtained in the first step A second step of introducing high-pressure heating water into the gelled slurry to promote a hydrothermal reaction to form calcium silicate hydrate; and (c) a third step of reducing the pressure of the product slurry obtained in the second step and removing the slurry. Calcium silicate hydrate in which crystal grains of different shapes of burrs and barleys are mixed by using high-pressure heated water containing caustic in the second step in the method for producing calcium silicate comprising How to manufacture. (4) The method according to (3) above, wherein the mixing ratio of burrs and barley crystals is controlled by adjusting the caustic concentration in the first step and the caustic concentration in the second step. (5) (a) In the first step, the mixed raw material CaO / S
iO ₂ molar ratio is 0.8-1.3: 1.0, caustic concentration of aqueous slurry is 0.1-0.4% by weight, heating temperature is 50-100 ° C., 40-6
0% is gelled. (B) In the second step, the caustic alkali concentration of the high pressure heating water is 0.15 to 0.4% by weight, and the gelled slurry and the high pressure heating water containing caustic are mixed in a vertical reaction vessel. Is continuously introduced from the bottom of the container, heated to 160 ° C. or higher within 5 minutes with stirring, and raised at a temperature of 180 to 210 ° C. for 1 to 4 hours at a temperature of 180 to 210 ° C. (C) The method according to (3) above, wherein the thermal reaction is advanced, and in the third step, the product slurry is continuously depressurized and taken out from the upper part of the vessel.

[0008]

[Specific description] Calcium silicate hydrate The calcium silicate hydrate of the present invention will be specifically described with reference to the drawings. FIG. 1 is an electron micrograph showing the crystal state of calcium silicate hydrate of the present invention, and FIG. 2 is an electron micrograph showing the crystal state of calcium silicate hydrate obtained by a conventional production method. In the figure, 10 and 20 are crystal particles of calcium silicate hydrate, 10 is a burr-shaped crystal, and 20 is a spikelet-shaped crystal. As shown in FIG. 1, the calcium silicate hydrate according to the present invention is composed of a mixture of a scallop crystal 10 and a wheat spike crystal 20.
The area between 0 is filled with the wheat spike-shaped crystal 20 and the two are integrally joined, and the bur-shaped crystal is relatively light in weight unlike the conventional one. On the other hand, the conventional calcium silicate hydrate has almost no spikelet crystals as shown in FIG.
Most of the burs are formed by the burrs 10, and the burrs have extremely short acicular protrusions on the surface as compared with the burrs mixed in the calcium silicate hydrate of the present invention. Is heavier and heavier.

[0009] Here, several examples of the calcium silicate hydrate compact of the present invention, in which imo-like crystals and wheat spike-like crystals are mixed in substantially equal amounts, and a conventional calcium silicate hydrate formed entirely of iga-like crystals for molded bodies, the bulk density, drying shrinkage, are as the following table a comparison of flexural strength and specific strength, although calcium silicate hydrate formed body of the present invention is drying shrinkage is slightly large, a bulk specific gravity of any Also less than 0.3
It is small and has a remarkably high bending strength. Further, as shown in the comparative example, even in the case where the swelling crystals are mixed with the squirting crystals, even if the squirting crystals are heavier, the bending strength is not so improved although the bulk specific gravity is large. As described above, the calcium silicate hydrate molded article of the present invention is a mixture of burrs and barley crystals, and the burrs are not heavier,
Lighter and more excellent in mechanical strength than conventional molded products.

[0010]

[Table 1]

Production Method A method for producing a calcium silicate hydrate having a mixture of burrs and barley crystals according to the present invention will be described below with reference to the drawings. The percentages are by weight unless otherwise specified. FIG. 3 is a process chart of the production method of the present invention. As shown in the drawing, the production method of the present invention comprises: (a) adding an aqueous slurry obtained by adding water to a mixed raw material of a calcareous raw material and a siliceous raw material; Adding, heating and gelling a first step 31, (b)
A high pressure heating water containing caustic alkali is introduced into the gelled slurry obtained in the first step to promote a hydrothermal reaction to form calcium silicate hydrate 32, and (c) obtained in the second step Third step 33 of removing the product slurry by pressure reduction
Consists of

The calcareous raw material used in the present invention is at least one kind selected from slaked lime, quick lime, and carbide slag, and the siliceous raw material is a naturally occurring amorphous silicate such as clay, diatomaceous earth, and soft silica. At least one member selected from the group consisting of powder (less than 200 mesh), white carbon, fecesilicon dust, and amorphous silica such as silica generated when cryolite is produced from sodium silicofluoride. Silicic acid or a mixture of this silicic acid and crystalline silicic acid powder (200 mesh or less).

First, in a first step, water is added to a mixed raw material of a calcareous raw material and a siliceous raw material to produce an aqueous slurry. The ratio of the calcareous material and the siliceous material differs depending on the type of calcium silicate hydrate to be produced.
It is preferred that the O / SiO ₂ molar ratio be adjusted to 0.8 to 1.3: 1.00. The amount of water to be added to the mixed raw material is suitably 2.5 to 10 times the mixed raw material. Caustic alkali is added to the aqueous slurry, and the mixture is heated to 50 to 100 ° C. and stirred to cause a gelling reaction of 40 to 60% of the raw material. The amount of the caustic added is suitably from 0.1 to 0.4% in the aqueous slurry immediately after the addition. If the concentration is less than 0.10%, the progress of the gelling reaction of the raw material is slow, and the initial reaction in the second step is fast. On the other hand, if the caustic alkali concentration exceeds 0.4%, the reaction in the first step proceeds too much and the amount of intermediate products increases, and the crystallization reaction in the second step requires a long time. The addition of alkali is not preferred. That is, the caustic alkali concentration in the first step is in the range of 0.10 to 0.4%, and the gelling reaction rate of the raw material is set to facilitate the control of the crystal shape in the high pressure hydrothermal reaction in the second step. It is better to be in the range of 40 to 60%.

Next, in a second step, high-pressure heating water is introduced into the slurry gelled in the first step to cause a hydrothermal reaction of the aqueous slurry to proceed. The amount of the high-pressure heating water is suitably 5 to 25 times the solid content (mixed raw material) in the slurry. As the high-pressure heating water, one containing caustic alkali is used. As a specific example, as shown in Embodiment 1, NaOH water and high-pressure steam are mixed and supplied. High-pressure steam may be introduced together with high-pressure heating water. As the reaction vessel, a rigid high-pressure reaction vessel is preferably used, and the aqueous slurry obtained in the first step and the high-pressure heated water are preferably continuously and separately introduced from the bottom of the vessel. The temperature inside the container is heated to 160 ° C. within 5 minutes while stirring the gelled slurry sent to the lower portion of the container, and the upper half of the container is not stirred while raising the slurry in a layer in the container. The slurry is kept at a temperature of 180 to 210 ° C. for 1 to 4 hours to advance the hydrothermal reaction.

The caustic alkali in the high-pressure heated water used in the second step determines the initial reaction of the high-pressure hydrothermal reaction and the rate of formation of the secondary crystals of calcium silicate hydrate, iga-like crystals and spike-like crystals. The concentration is suitably 0.15 to 0.4% in high-pressure heated water. If the caustic alkali concentration in the high-pressure heating water is less than 0.05%, the generated calcium silicate hydrate is rapidly crystallized, and the generated secondary crystals are increased in weight to generate a large amount of swelling crystals of 70% or more. A molded product obtained from a material having a large number of burrs has a large specific gravity and a low strength.
When the caustic alkali concentration is 0.15 to 0.25%, the crystal shape of the calcium silicate hydrate is such that the ratio of burrs is 50 to 50%.
It produces 70%. Moreover, the caustic alkali concentration is 0.25 to
When it is in the range of 0.40%, the crystals of calcium silicate hydrate to be formed have a swelling of 30% to 50%, and the proportion of spikelet-like crystals is greater than that of the swelling crystals, and the specific gravity of the compact is small. High mechanical strength can be obtained. On the other hand, when the caustic alkali concentration exceeds 0.4%, the crystallization reaction in the rigid high-pressure reaction vessel becomes extremely slow, and the unreacted crystals and spike-like crystals are slightly formed in the generated calcium silicate hydrate, The product has a large drying shrinkage and is distorted, so that an industrially effective calcium silicate molded product cannot be obtained. From the above, in order to obtain a high-strength compact, the caustic alkali concentration in the high-pressure heated water in the second step should be 0.15 to 0.40%
Is preferred.

In the second step, the aqueous slurry is raised in the vessel by high-pressure heated water containing caustic,
While staying at a temperature of 180 to 210 ° C. for 1 to 4 hours, a hydrothermal synthesis reaction proceeds, and a calcium silicate hydrate mainly composed of zonotolite is generated. In the third step, the calcium silicate hydrate slurry is reduced in pressure and continuously discharged from the upper part of the vessel.

The calcium silicate hydrate slurry obtained in the third step is subjected to a conventional method, to which reinforcing fibers are added, pressurized and dewatered, and then dried to form a molded body.

Next, examples and comparative examples of the present invention will be described. Example 1 A raw material powder (CaO: SiO ₂ molar ratio of 1.0 mixed with 100 parts of slaked lime powder (CaO: 73.5%) and 140.7 parts of amorphous silicic acid powder (SiO ₂ : 55.9%) ), Water is added so that the total amount of water becomes 4 times water with respect to the solid content, and further, N is added in such an amount that the caustic alkali concentration in the water becomes 0.10%.
An aqueous slurry was prepared by adding aOH. This aqueous slurry was reacted at 80 ° C. with stirring for 3 hours to gel. The resulting gelled slurry and 0.15% NaO
High-pressure heated water at 200 ° C adjusted to H
The aqueous slurry and the high-pressure heated water were separately and continuously fed from the bottom into a rigid high-pressure reaction vessel maintained at 00 ° C at a weight ratio of 1: 3.5. Subsequently, the lower portion of the reaction vessel was stirred, and the slurry at a height of 1/2 or more of the reaction vessel was allowed to stay for 2 hours without disturbing. Then, the generated slurry was taken out from the upper portion of the reaction vessel under reduced pressure. Next, 7 parts of glass fiber was added to 100 parts of the solid content of this calcium silicate hydrate slurry, followed by pressure dehydration molding, followed by drying to obtain a molded product (300 × 30).
0 × 25 mm). Table 2 shows the crystal state of the calcium silicate hydrate and the physical properties of the molded product obtained therefrom.

Examples 2 to 8 and Comparative Example A calcium silicate hydrate was obtained in the same manner as in Example 1 except that the concentration of the caustic alkali in the first step and the concentration of the caustic alkali in the second step were changed as shown in Table 2. Was. Table 2 summarizes the crystal state of the calcium silicate hydrate and the physical properties of the molded product obtained therefrom.

As shown in Table 2, the calcium silicate hydrate produced without adding caustic to the high-pressure heated water in the second step does not contain any caustic in the first step (Sample No. 1). ) Or in the case of adding 0.1% or less (Sample No. 6), almost all of the calcium silicate hydrate crystals formed are heavier iga-like crystals, and therefore the specific strength is remarkably large. Low. In the first step,
Even when 0.4% caustic alkali is added (sample N
o. 11, 16), the generation rate of the spike-shaped crystals is 10 to 20%, and since most of them are heavier-shaped burrs, the specific strength is at most about 130, 190 . In addition, those in which the caustic alkali was added in excess of 0.4% or more in the first step (samples Nos. 20 to 22) all had a large bulk specific gravity, and thus the specific strength was lowered. On the other hand, the calcium silicate hydrate of the present invention produced by adding caustic to the high-pressure heated water in the second step has a caustic concentration of 0.1 to 0.1 in the first step.
0.4%, caustic alkali concentration of 0.25-0.
4%, the gelation ratio of the primary gel is in the range of 40 to 60%, the bulk specific gravity is 0.3 or less, but the bending strength is 29 to 36 kgf /
cm ² , and therefore all have a specific strength of 300 or more , and some of them exceed 500 , and have excellent mechanical strength while being lightweight.

[0021]

[Table 2]

[0022]

The calcium silicate hydrate of the present invention has a structure in which burrs and barley crystals are mixed.
Compared to conventional products, they are lighter but have significantly higher mechanical strength. Further, according to the production method of the present invention, such a calcium silicate hydrate can be easily produced, and the ratio of burrs and barley crystals can be arbitrarily controlled. Calcium silicate hydrate can be produced.

[Brief description of the drawings]

FIG. 1 is an electron micrograph of a particle structure showing a crystalline state of a calcium silicate hydrate of the present invention.

FIG. 2 is an electron micrograph of a particle structure showing a crystal state of a conventional calcium silicate hydrate.

FIG. 3 is a process chart of a manufacturing method according to the present invention.

[Explanation of symbols]

10-germ-like crystal, 20-wheat-like crystal, 31-first
Step, 32-second step, 33-third step

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-1-122917 (JP, A) JP-A-56-45818 (JP, A) JP-A-56-164010 (JP, A) JP-A-53-1984 109252 (JP, A) JP-A-60-204655 (JP, A) JP-B-54-10956 (JP, B2) JP-B-54-10957 (JP, B2) (58) Fields investigated (Int. Cl. ⁷ , DB name) C01B 33/24 CA (STN) JICST file (JOIS)

Claims (5)

(57) [Claims] 1. A ne from calcareous material and siliceous calcium silicate hydrate crystal particles are mixed in the resultant Louis moth-like crystals and different shapes of wheat spikes crystal by hydrothermal reaction of the starting material
Ri, calcium silicate hydrates formed body bulk density of the molded body, characterized in that less than 0.3. 2. The formed calcium silicate hydrate product according to claim 1, wherein the ratio of the scallop-like crystals to the spikelets (spot-like crystals: spikelets-like crystals) is 7: 3: 3-7. 3. A first step of adding a caustic alkali to an aqueous slurry obtained by adding water to a mixed raw material of a calcareous raw material and a siliceous raw material, and heating and gelling, and (b) the first step. A second step of introducing high-pressure heating water into the obtained gelled slurry to promote a hydrothermal reaction to form calcium silicate hydrate; and (c) reducing the pressure of the product slurry obtained in the second step and removing the slurry. In a method for producing calcium silicate comprising three steps,
A method for producing calcium silicate hydrate in which crystal grains of different shapes of burrs and barleys are mixed by using high-pressure heated water containing caustic in the second step. 4. The method according to claim 3, wherein the mixing ratio of the burrs and barley crystals is controlled by adjusting the concentration of the caustic alkali in the first step and the concentration of the caustic alkali in the second step. 5. (a) In the first step, the mixed raw material Ca
An O / SiO ₂ molar ratio of 0.8 to 1.3: 1.0,
The aqueous slurry has a caustic concentration of 0.1 to 0.4% by weight, a heating temperature of 50 to 100 ° C.,
(B) In the second step, the high pressure heating water has a caustic alkali concentration of 0.15 to 0.4% by weight, and the gelled slurry and the caustic alkali-containing high pressure heating water are vertically It is continuously introduced from the bottom of the reaction vessel, heated to 160 ° C. or higher within 5 minutes with stirring, and raised in a layered manner toward the top of the vessel at a temperature of 180 to 210 ° C. for 1 to 1 hour.
The method according to claim 3, wherein the hydrothermal reaction is allowed to proceed for 4 hours, and (c) in the third step, the product slurry is depressurized and continuously taken out from the upper part of the vessel.