JP3456662B2 - Method for producing tobermorite - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to tobermorite, a highly crystalline calcium silicate hydrate used for heat insulating materials, plastic fillers, catalyst carriers, building materials and the like. For a very short time in an autoclave. [0002] Conventional tobermorite (Ca ₅ (Si ₆ O
_{16 (OH) 4) · 2H} 2 O) is generally quartz,
It is synthesized by an autoclave reaction at 180 ° C. and 10 atm from a crystalline silicic acid raw material and lime having low solubility such as silica stone. This reaction, by the reaction of calcium ions eluted from the silicic acid ion and calcareous material eluted from the siliceous material in the autoclave initial reaction which is an intermediate product of amorphous-like CaO-SiO 2 _-H 2 _O Gel (hereinafter C -SH gel), and the CSH gel is crystallized by the autoclave reaction. [0003] In this method, a raw material having low solubility is used.
It takes a long time of 10 to 15 hours under high pressure and high pressure. On the other hand, when an amorphous silicic acid raw material having high solubility is used as a silicic acid raw material, the dissolution of the silicic acid raw material in the autoclave is fast, and the C-S-C is faster than when a crystalline silicic acid raw material having a slow dissolution rate is used. -H gel is generated, but only the CSH gel is generated, the subsequent reaction does not proceed, and high-crystalline tobermorite is hardly generated, and the reaction time is rather long. I can't get it. [0005] In order to solve this problem, there has been proposed a method of adding an aluminum compound to an amorphous silicic acid raw material and a calcareous raw material and performing autoclave. As compared with the case where the aluminum compound is not added, the aluminum compound promotes the crystal formation reaction and generates tobermorite crystals. However, it takes as long as 10 hours to obtain a highly crystalline tobermorite without CSH gel which is an intermediate product. (Annual Report of the Cement Technology 35, Showa 46) Therefore, the time is not significantly reduced as compared with the case where a crystalline silica raw material is used. A part of the Si atoms in the silica chain in the tobermorite crystal structure is isomorphously substituted by aluminum (Al) atoms, and in order to compensate for the charge generated by this substitution, part of Ca between the layers is replaced by K or Na. The synthesis of substituted aluminum-substituted tobermorites has also been reported. This aluminum-substituted tobermorite is obtained by adding an aluminum compound and an alkali compound to a calcareous raw material and a silicic acid raw material,
Direct autoclave curing and synthesis methods have been proposed, but it takes a long time to obtain crystalline tobermorite (J. Am. Ceram. Soc. 74 [2] 274-79 (1991), Annual Report on Cement Technology 38 (Showa 62). Further, a blast furnace slag containing an aluminum component in its composition and a hydroxide of an alkali metal are added to a calcareous raw material and an amorphous silicic acid raw material, so that tobermorite can be obtained under normal pressure of 100 ° C. or less regardless of autoclave reaction. A method for producing crystals (Japanese Patent Application Laid-Open No. 4-139017) has been invented.
The reaction takes a long time, that is, from 45 hours to 45 hours, and its crystallinity is not so high as judged from the X-ray diffraction chart. At present, as the only report for producing high-crystal tobermorite in a short time, there has been reported a reaction example using a calcareous raw material and a special zeolite, clinobutyrite, as a source of siliceous, aluminum and alkali (Mineralogical).
Journal vol.6 No.3 1970). Clinobutyrolite is
Low crystalline zeolite containing alkali and aluminum. It is thought that the unique structure shows high reactivity, whereas hydrogarnet is generated in other zeolites, whereas when using clinobutyrolite, hydrogarnet is not generated and tobermorite crystals are generated. Reporting. In this method, a special raw material, clinbutyrolite, must be used as a main raw material, and a versatile and inexpensively available amorphous silicic acid raw material cannot be used as a main raw material. Therefore, in the prior art, when an amorphous silicic acid raw material having a high dissolution rate is used, the generation of tobermorite crystals becomes extremely slow. A crystalline silica material having a slow dissolution rate had to be used. In addition, even if the reaction is promoted by adding an aluminum compound to the amorphous silicic acid raw material, the time for tobermorite crystal formation is improved only to the same extent as when a crystalline silicic acid raw material having a slow dissolution rate is used. There is a disadvantage that there is no method for obtaining tobermorite crystals in a short time other than using raw materials. In the process of producing calcium silicate building materials, there is an urgent need to further improve the productivity, and for that purpose, there was a problem that tobermorite crystals were produced in a shorter time using versatile and inexpensive raw materials. . [0010] The present invention relates to a calcareous raw material and an amorphous silicic acid raw material, an aluminum compound and an alkali metal water.
Oxide and co-existence, primary reaction below 100 ° C and 100
The inventors have found that by combining a secondary reaction with an autoclave at a temperature of not less than ° C, tobermorite can be obtained in an extremely short time, and have completed the present invention. That is, the present inventors have studied in detail the formation mechanism of tobermorite crystals, and have studied the conventional hydrothermal reaction conditions (for example, 180
In the case of using a crystalline silicic acid raw material, a tobermorite crystallization reaction easily occurs from a CSH gel which is an intermediate product of the reaction, and an amorphous silicic acid raw material is used. Focused on that the tobermorite crystallization reaction hardly occurs from the CSH gel. That is, the C-S-H gel, which is a reaction intermediate product, gives the same diffraction pattern from the bulk structure analysis by X-ray diffraction, but the C-H gel, which is an intermediate product generated when each raw material is used, It was assumed that the microstructure of the SH gel was different. Therefore, C—S—H gels were synthesized by various methods, and the reactivity to tobermorite crystals was examined. As a result, C-S-H containing aluminum and alkali obtained by a primary reaction in which an aluminum compound and an alkali metal hydroxide coexist in an amorphous silicic acid raw material and are preliminarily reacted with a calcareous raw material at a temperature of 100 ° C. or less. It has been found that tobermorite can be obtained in a very short time by obtaining a gel and then performing a secondary reaction at a temperature of 100 ° C. or higher by an autoclave. [0011] Namely, the present invention is in the preparation of calcium silicate hydrate to hydrothermal reaction of calcareous material and the amorphous silicic acid starting material, the aluminum-containing compound to a該石ash feedstock and the amorphous silicate material Al / Si + Al 0.01 in molar ratio
To 0.2 and an alkali metal hydroxide in an R / Al molar ratio of 0.01 to 10;
The reaction is carried out for 0 minute to 8 hours, and a secondary reaction is carried out in an autoclave at a temperature of 100 ° C. or more, whereby 30 minutes to 6 hours.
This is a production method for producing tobermorite in a very short time, such as about an hour. Originally, tobermorite is 18
Although calcium silicate hydrate is stable at 0 ° C,
Produced by the following reaction. Aluminum and alkali-containing CSH with a structure that is extremely easy to crystallize into tobermorite
The tobermorite can be produced in a very short time by introducing the gel into this stable region, that is, by performing a hydrothermal reaction in an autoclave at 100 ° C. or higher thereafter. The calcareous raw material used in the present invention is cement,
A calcareous material generally used for synthesizing calcium silicate hydrate such as lime can be used. As the amorphous silicic acid raw material, silicic acid, silica fume, fly ash, colloidal silica, diatomaceous earth, shirasu, obsidian, and other pozzolanic substances can be used. [0013] As the aluminum-containing compounds, aluminum hydroxide, aluminum oxide, aluminum sulfate, aluminum compounds aluminum chloride and metallic aluminum, bauxite, boehmite, Daiasuboa natural mineral containing cement clay, aluminum, such as 10% or more, Industrial by-products containing 10% or more of aluminum, such as silica fume, fly ash, and blast furnace slag, can be used alone or in combination. Alkali metal
As the hydroxide , lithium hydroxide, sodium hydroxide, potassium hydroxide, rubidium hydroxide, alkali metal hydroxide of cesium hydroxide can be used in principle, but when using an alkali metal hydroxide From the viewpoint of economy, lithium hydroxide, sodium hydroxide, and potassium hydroxide are desirable. In addition to alkali metal hydroxides, any alkali-containing substance that easily dissolves into a basic aqueous solution can be used in principle. In some cases, an aluminum or alkali compound such as sodium aluminate can be used. Further, the alkali metal hydroxide used in excess can be separated and recovered from the tobermorite crystals after the reaction, and used again. These can be used alone or in combination in consideration of economy. The aluminum-containing compound has an Al / Si + Al molar ratio of 0.01 to 0.20, preferably 0.01 to 0.1.
So that it becomes 6. When the content is 0.01 or less, the effect of the present invention is not exhibited. When the content is 0.20 or more, by-products such as hydrogarnet are generated, and the generation of tobermorite is suppressed. The alkali metal hydroxide has an R / Al molar ratio of 0.01.
To 10, preferably 0.1 to 3.0. Where R
Represents an alkali metal of Li, Na, K, Rb, and Cs. If it is 0.01 or less, the effect of the present invention is not exhibited, and 10
No promotion effect is seen above. Water / solids ratio (W /
S) is desirably 20 or less, more desirably 10 or less when a molded article is to be obtained, but is not limited to this range when a slurry of tobermorite crystals is desired. The raw material is first heated at a temperature of 100 ° C. or lower, preferably 60 to 90 ° C., and the added raw material is reacted to obtain a CaO—SiO ₂ — containing aluminum and alkali.
This is performed until an H ₂ O gel (CSH gel) is generated. Usually, a CSH gel containing aluminum and alkali is formed at 100 ° C. or lower for 30 minutes to 8 hours. The reaction apparatus is not particularly limited, and may be any apparatus capable of controlling a desired temperature by heating with a heater or a heat medium, and it is desirable that the relative humidity in the container is maintained at 65% or more. The form of the reaction raw material may be either a slurry state or a solid state depending on the water / solid content ratio (W / S). In the case of a slurry, stirring may or may not be performed. Therefore, it is desirable to perform stirring. This CSH containing aluminum and alkali
The gel is subjected to a hydrothermal reaction using an autoclave under a saturated steam pressure of 100 ° C. or higher. Tobermorite can be obtained in a curing time of 30 minutes to 6 hours, depending on the temperature and pressure conditions of the autoclave reaction. For example, 180 ° C1
When autoclaving at 0 atm, highly crystalline tobermorite can be obtained in a very short time of about 30 minutes to 2 hours. The hydrothermal reaction can be performed in principle under conditions where saturated steam at 100 to 250 ° C is present. From the viewpoint of shortening the reaction time and economy, preferably, the temperature around 180 ° C. on the high temperature side is an appropriate temperature, but the temperature is not limited to this. The reaction is not limited to a specific reactor as long as a saturated steam atmosphere at 100 to 250 ° C. can be formed. For example, regarding the heating method, a method of externally heating with a heater or a heat medium such as oil, a method of blowing steam, or a method of performing a hydrothermal reaction by heating with a high frequency generator or the like can be used. The time required for the reaction at 100 ° C. or lower and the reaction in the autoclave vary depending on the composition of the raw materials, but it can be said that the longer the reaction time at 100 ° C. or lower, the shorter the time required for the autoclave reaction. In the present invention, as described above, an aluminum compound and an alkali metal hydroxide are added to the main raw materials of the calcareous raw material and the amorphous silicic acid raw material, and the primary reaction is performed at a temperature of 100 ° C. or less. And Ca containing aluminum and alkali
After generating the O—SiO ₂ —H ₂ O gel, one more
Since the secondary reaction is performed in an autoclave at 00 ° C or higher, 3
Tobermorite can be produced in a very short time of 0 minutes to 6 hours. EXAMPLE A specific example of the method for producing tobermorite according to the present invention will be described below. In this example, in order to confirm tobermorite crystallinity, 2θ (Cukα) = 7.8, 1 in X-ray diffraction method (hereinafter referred to as XRD).
The background of each peak of 5.9, 28.7, 29.9, and 31.6 was removed, and after performing smoothing, the intensities were integrated and compared. The measurement conditions are: measurement angle 5 to 45 degrees (2θ), step sampling 0.02 / degree, scan speed 2 degrees / min, voltage 30 kv, current 15 m
A, The measurement point was CPS. [0020] [Example 1] Calcium hydroxide as calcareous material, silicate and aluminum hydroxide as aluminum-containing compound as an amorphous silicic acid starting material, the composition shown in Table 1 of lithium hydroxide as the alkali metal hydroxide The mixture was mixed as above, 250 parts by weight of water was added, and the mixture was stirred and kept at 80 ° C. for 6 hours to be reacted. Subsequently, the product obtained by the above reaction was reacted in an autoclave under high-temperature and high-pressure conditions of 180 ° C. and 10 atm for 30 minutes. This was rapidly cooled with room temperature water. Next, take out the composite from the micro cylinder,
It was dried at 60 ° C. overnight in a vacuum dryer.
As a result of measuring the synthesized product by XRD, it was found that the product was tobermorite crystals. The sum of diffraction line intensities of the obtained tobermorite crystals was 2251 cps, and it was found that the crystallinity was extremely high. The diffraction pattern obtained by the XRD measurement is shown in FIG. [0021] In Example 2 and 3 TABLE weight composition ratio shown in 1, to give a compound subjected to other similar processes as in Example 1 with sodium and potassium hydroxide as the alkali metal hydroxide Was. The sum of diffraction line intensities of the obtained synthesized product is 2146 cp.
s and 2189 cps. Examples 4 and 5 A was prepared at a weight composition ratio shown in Tables 1 and 2.
The l / (Si + Al) molar ratio is 0.06 and 0.03
Other than that described above, the same treatment as in Example 1 was performed to obtain a synthesized product. The sum of diffraction line intensities of the obtained compound is 2096 cps.
And 1983 cps. Examples 6 and 7 Li / A at the weight composition ratio shown in Table 2.
The same treatment as in Example 1 was performed except that the molar ratio was changed to 0.8 and 3.0, to obtain a synthesized product. The sum of the diffraction line intensities of the obtained composite was 2001 cps and 2177 cp.
s. Examples 8 and 9 The same treatment as in Example 1 was carried out except that boehmite and aluminum oxide were used as aluminum compounds at the weight composition ratios shown in Table 3, to obtain a synthesized product. The sum of diffraction line intensities of the obtained compound is 2305 cp.
s and 2145 cps. [0025] In the weight composition ratio shown in Example 10 of Table 3, sodium hydroxide as an amorphous silicic acid starting material silica fume, as alkali metal hydroxides, except for using the metallic aluminum powder as the aluminum compound in Example 1 The same treatment as described above was performed to obtain a synthesized product. The sum of diffraction line intensities of the obtained synthesized product was 1980 cps. Example 11 A composite was obtained by performing the same treatment as in Example 1 except that colloidal silica was used as a raw material of the specific crystalline silicic acid at the weight composition ratio shown in Table 3. The sum of diffraction line intensities of the obtained synthesized product was 2026 cps. Example 12 A synthetic product was obtained by performing the same treatment as in Example 1 except that fly ash was used as an amorphous silicic acid raw material at the weight composition ratios shown in Table 4. The sum of diffraction line intensities of the obtained synthesized product was 2242 cps. Example 13 A synthetic product was obtained by performing the same treatment as in Example 1 except that a reaction at 100 ° C. or lower was carried out at 60 ° C. for 12 hours at a weight composition ratio shown in Table 4. The sum of diffraction line intensities of the obtained synthesized product was 2356 cps. Example 14 The same treatment as in Example 1 was carried out except that the reaction at 100 ° C. or less was carried out at 90 ° C. for 3 hours at the weight composition ratio shown in Table 4, to obtain a synthesized product. The sum of diffraction line intensities of the obtained synthesized product was 2437 cps. [0030] In the weight composition ratio shown in Comparative Example 1 in Table 5, the alkali metal hydrosulfide
Potassium hydroxide was used as the oxide, and after mixing the raw materials, one micro cylinder was directly used without performing a reaction at 100 ° C. or less.
Except for heating to 80 ° C. and performing the autoclave reaction, the same treatment as in Example 1 was performed to obtain a synthesized product. The sum of diffraction line intensities of the obtained synthesized product was 1390 cps. [0031] In the weight composition ratio shown in Comparative Example 2] Table 5, the alkali metal hydrosulfide
Using sodium hydroxide as the oxide, a reaction was performed at 100 ° C. for 120 hours after mixing the raw materials, and the same treatment as in Example 1 was performed except that the autoclave reaction at 180 ° C. was not performed, to obtain a synthesized product. The sum of diffraction line intensities of the obtained synthesized product was 558 cps. [0032] In the weight composition ratio shown in Comparative Example 3 Table 5, the alkali metal hydrosulfide
A process similar to that of Example 1 was performed except that no oxide was added, to obtain a synthesized product. The sum of diffraction line intensities of the obtained synthesized product was 998 cps. As shown in Tables 1 to 5, in a method for producing tobermorite mainly composed of an amorphous siliceous raw material and a calcareous raw material, an aluminum-containing compound and an alkali metal hydroxide are added to the raw material and reacted at 100 ° C. or lower. After performing the above, the sample that has been subjected to the autoclave reaction can obtain tobermorite with good crystallinity in a very short autoclave time.
(Hereinafter referred to as “margin”) [Table 2] [Table 3] [Table 4] [Table 5] The tobermorite manufacturing method according to the present invention, as described above, siliceous raw material by using the amorphous ones,
Since the autoclave reaction is performed after the reaction at 100 ° C. or less after adding the aluminum-containing compound and the alkali metal hydroxide to the raw materials, high quality tobermorite can be produced in a very short time. Furthermore, by carrying out the present invention in this way, tobermorite can be produced in a very short time, so that calcium silicate building materials such as lightweight cellular concrete (ALC) containing tobermorite as a main component can be mass-produced efficiently in a short time. It has features such as being able to do.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an explanatory diagram showing a diffraction pattern obtained by XRD measurement.

Continuation of the front page (56) References JP-A-53-63425 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C01B 33/20

Claims (1)

(57) [Claims] [Claim 1] Silicic acid, silica fume, fly ash
, Colloidal silica, diatomaceous earth, shirasu, obsidian,
In a method for producing tobermorite, which comprises a hydrothermal reaction between an amorphous silicic acid raw material and a calcareous raw material comprising at least one of other pozzolanic substances, the amorphous silicic acid raw material and the calcareous raw material include Al / (S
i + Al) 0.01 to 0.2 in molar ratio, Li, Na,
An alkali metal hydroxide selected from K, Rb and Cs is represented by R
/ Al (R = Li, Na, K, Rb, Cs) added in a molar ratio of 0.01 to 10 and reacted at a temperature of 100 ° C. or lower to obtain CaO— containing an aluminum compound and an alkali metal compound. A method for producing tobermorite, which further comprises performing an autoclave reaction at 100 ° C. or more after generating the SiO ₂ —H ₂ O gel.