JP2631304B2 - Method for manufacturing calcium silicate compact - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a novel method for producing a calcium silicate molded product.

Conventional technology and its problems Calcium silicate moldings are lightweight, have high strength, are excellent in heat insulation, have high fire resistance, and have many other properties. It is widely used in various fields such as building materials.

Thus, in order to improve the heat insulating performance of the calcium silicate molded body, the weight of the molded body has been further reduced in recent years. The disadvantage is that the body surface becomes powdery.
In particular, the drawback of powdering is remarkable in a molded article using a water repellent.

Conventionally, as a method of solving these drawbacks, a hydrothermal synthesis reaction of an aqueous slurry of a silicic acid material such as ferrosilicon dust and a lime material under stirring to form a bulky zonotlite slurry, and after mixing cement and sodium silicate, Forming and drying to form a compact (JP-B-56-16102)
It has been known. However, according to this method, although the powderiness of the molded body surface is reduced, the strength of the molded body is insufficient, and 1000 ° C.
Above, there is a problem that it becomes difficult to use due to contraction and deformation.

In addition, a method of increasing the strength of a calcium silicate molded body by the presence of a lithium compound when a lime raw material, a silicate raw material and water are subjected to a hydrothermal synthesis reaction (Japanese Patent Application Laid-Open No. 59-2695)
No. 7) is known. However, the molded article obtained by this method has a problem that it is highly corrosive to various metals and the like due to the contained lithium.

Means for Solving the Problems The inventor of the present invention has intensively studied to develop a method which can solve the above-mentioned disadvantages associated with the reduction in the weight of the calcium silicate molded article and does not cause any problems in the above-mentioned known methods. As a result, an aqueous slurry of calcium silicate crystals is prepared by subjecting a raw material slurry containing a silicate raw material, a lime raw material, and water represented by Japanese Patent Publication No. In a method for producing a calcium silicate molded product by molding and drying the same, when the reaction is carried out in the presence of a specific amount of a specific alkali silicate substance, the above-mentioned problems do not occur, and the resistance of the lightweight calcium silicate molded product is reduced. The present inventors have found that the wearability and strength are improved, the powderiness of the surface of the molded article is improved by the improvement of the wear resistance, the corrosion resistance is improved, and the like, and the present invention has been completed.

That is, in the present invention, a raw slurry containing a silicic acid raw material, a lime raw material and water is subjected to a hydrothermal synthesis reaction while heating and stirring under pressure to prepare an aqueous slurry of calcium silicate crystals, which is then formed and dried to form a silica slurry. In the method for manufacturing a calcium compact, at least one alkali silicate substance of sodium silicate and potassium silicate is converted to the content of M ₂ O (M represents sodium or potassium) in the alkali silicate substance in the raw material slurry. And a hydrothermal synthesis reaction in the presence of the substance in an amount of 0.3 to 3% by weight based on the total weight of the silicate raw material and the lime raw material.

As the silicic acid raw material used in the present invention, any of those conventionally used in the production of calcium silicate compacts can be effectively used, and silica ash, silica sand, etc., grain ash (eg, rice husk ash), silica gel And silica flower (ferrosilicon dust, etc.), white carbon, diatomaceous earth, silica obtained by reacting hydrosilicofluoric acid by-produced in the wet phosphoric acid production process with aluminum hydroxide, and the like.

In addition, as the lime raw material used in the present invention, any of those conventionally used can be used, such as quicklime,
Examples include slaked lime and carbide residue. From the perspective of producing lightweight calcium silicate compacts, the lime raw material has a settling volume
It is preferable to use it as lime milk of 5 ml or more. Particularly preferred are those with a settling volume of 10 ml or more.

The lime milk settling volume is defined as the ratio of water to lime solids.
This is the volume in ml in which lime particles settled after 50 ml of 120-fold lime milk was allowed to stand in a measuring cylinder having an inner diameter of 1.3 cm and a volume of 50 cm ³ for 20 minutes. A large sedimentation volume means that the lime is well dispersed in water, is in a stable state, and has high reactivity. By using lime milk having a large sedimentation volume, the apparent density of the obtained calcium silicate crystal becomes low, so that it becomes easy to produce a low-density lightweight body of, for example, about 0.1 g / cm ³ .

Also, the CaO / SiO ₂ molar ratio of the silicate raw material and the lime raw material is usually
It is about 0.70 to 1.30, especially about 0.70 to 0.90 when trying to synthesize tobermorite crystals, and about 0.90 to 1.15 when trying to synthesize zonotolite crystals. Further, the silicic acid content in the alkali silicate material required in the present application is:
Include in the calculation of molar ratio as it reacts with the lime raw material.

In the present invention, usually, a raw material slurry is prepared by further adding at least one alkali silicate substance of sodium silicate and potassium silicate and water to the above-mentioned silicate raw material and lime raw material. The alkali silicate may be added at any time as long as it is before the hydrothermal synthesis reaction. That is, in the present invention, it is essential to add the alkali silicate substance before the hydrothermal synthesis reaction, whereby the intended effect is exhibited. When the alkali silicate substance is added to the calcium silicate crystal slurry after the hydrothermal synthesis reaction, the abrasion resistance and strength of the obtained molded article are reduced.

As the sodium silicate in the present invention, for example, JIS
Solution sodium silicate No. 1 and 2 specified in K 1408
No. 3, No. 3, sodium metasilicate one kind, two kinds, etc., various commercially available powdered sodium silicate and the like, and potassium silicate can be various commercially available solution potassium silicate and the like, and at least one of these Add and use alkali silicate material.

The amount of the alkali silicate substance added is converted into the content of M ₂ O (M represents sodium or potassium) in the alkali silicate substance, and is 0.3 to the total weight of the silicate raw material and the lime raw material.
It is necessary that the amount be 3% by weight. If the added amount is less than 0.3% by weight, the abrasion resistance and strength tend not to be sufficiently improved, and if it is more than 3% by weight, drying shrinkage of the molded article tends to increase. Absent. A particularly preferable addition amount is such an amount that the converted value is about 0.5 to 2.5% by weight.

If necessary, an inorganic inert substance can be added to the raw material slurry in order to further improve the heat insulation performance. As the inert substance, it is preferable to use at least one of carbon substances, carbides, nitrides, silicides, and metal oxides disclosed by the present applicant in W085 / 02839. Specifically, for example, carbon materials such as activated carbon, charcoal, coal, carbon black and graphite, carbides such as silicon carbide, boron carbide and titanium carbide, nitrides such as silicon nitride, boron nitride and titanium nitride, calcium silicide and the like Silicide, iron oxide (hematite, magnetite, etc.), titanium oxide (rutile, etc.),
Examples thereof include metal oxides such as tin oxide, manganese oxide, zirconium oxide, ilmenite, zircon, and chromite, and these can be used alone or in combination of two or more. Further, the amount of the inert substance to be added is preferably not more than 70% by weight in the molded body from the viewpoint of the strength of the molded body.

Further, a conventionally known additive may be added to the raw material slurry, and examples of the additive at this time include inorganic fibers such as asbestos.

The amount of water in the preparation of raw material slurry, the solid raw slurry fraction to 5 times the weight or more, preferably 10 to 50 times by weight, when manufacturing lightweight body of about density of 0.1 g / cm ³ is
It is suitably 15 to 50 times by weight, preferably 20 to 40 times by weight.

The raw material slurry thus prepared is then subjected to a hydrothermal synthesis reaction with stirring. The reaction is usually 4 kg / cm ² or more, preferably at the saturated vapor pressure of 8~50kg / cm ^2. By this reaction, a uniform aqueous slurry of calcium silicate crystals containing tobermorite crystals and / or zonotlite crystals as a main component is obtained.

In the present invention, various additives may be further mixed as necessary before forming the aqueous slurry of calcium silicate crystals. In this case,
What has been used for the production of a calcium silicate molded product can be used in a wide range, and examples thereof include fibers, clays, cement, and various binders. Also, if necessary, from the viewpoint of imparting water repellency to reduce the water absorption of the molded body, for example, a resin such as dimethylpolysiloxane, methylhydrogenpolysiloxane or an organic resin as a silicone resin,
Various inorganic water repellents may be added and mixed. The addition of a water repellent increases the powderiness of the surface of the molded body. According to the present invention, however, the powderiness can be significantly improved also in this case.

In the present invention, then, an aqueous slurry mainly composed of calcium silicate crystals and further formed of other additives, if necessary, is formed by a conventional method such as press dehydration molding, centrifugal dehydration molding, etc., and dried to obtain the desired calcium silicate. A molded article can be obtained.

Effects of the Invention According to the present invention, in particular, a specific alkali silicate substance is added to a raw material slurry and a hydrothermal synthesis reaction under stirring is performed in the presence of the substance, thereby obtaining the following remarkable effects. The effect is achieved.

(1) Abrasion resistance and strength of the formed body, which is a problem in a formed body of calcium silicate, particularly a lightweight body, are remarkably improved.

(2) The powderiness of the surface of the molded body is improved as the wear resistance is improved. This effect is sufficiently exhibited even when a water repellent is used.

(3) The corrosion resistance of the molded body to various metals and the like is improved. This effect is particularly prominent when sodium silicate is used as the alkali silicate substance, and has a favorable effect on the suppression of stress corrosion cracking of austenitic stainless steel which becomes a problem when used as, for example, a heat insulator or a heat insulator. .

EXAMPLES Hereinafter, the present invention will be described specifically with reference to Examples and Comparative Examples. In the following examples, parts and% indicate parts by weight and% by weight, respectively, and various physical properties are measured by the following methods.

(B) Bending strength: Measured according to the method of JIS A 9510.

(B) Abrasion resistance A tumbling test was performed according to the method of ASTM-C421-77, and the weight loss rate of the test molded body was measured.

Example 1 The settled volume of lime milk obtained by slaking quicklime (CaO 95%) in warm water at 80 ° C and dispersing it in water with a homomixer is as follows:
It was 16-20 ml. A JIS No. 3 sodium silicate solution (SiO ₂ 29%, Na ₂ O 9.5%) is added to the above lime milk in a predetermined amount with respect to the total amount of the lime raw material and the silicic acid raw material. (98% SiO ₂ ) and add CaO / SiO ₂
The molar ratio was 1.00. Further, water was added thereto, and the total amount of water was adjusted so as to be 24 times the solid content to obtain a raw material slurry. This is saturated steam pressure 12kg / cm ² , temperature 191 ℃
Then, the mixture was stirred while rotating the stirring blade at a rotation speed of 154 rpm in an autoclave, and a hydrothermal synthesis reaction was carried out for 5 hours to obtain a slurry containing zonotolite crystals as a main component.

To 92 parts (solid content) of the slurry obtained above, 4 parts of glass fiber and 4 parts of Portland cement were added, followed by press dewatering and drying at 100 ° C. to obtain a molded article. The physical properties of the obtained molded body were as shown in Table 1.

In Table 1, the compacts of samples No. 3 to No. 5 were produced by the method of the present invention, and samples No. 1, 2 and 6 are shown for comparison.

Example 2 The settled volume of lime milk obtained by slaking quicklime (CaO 95%) in warm water at 80 ° C. and dispersing it in water with a homomixer is as follows:
It was 16-17 ml. Silica powder (98% SiO ₂ ) having an average particle diameter of 5.4 μm is added to the above lime milk, and various alkali silicate substances are converted to M ₂ O (M is the same as above) with respect to the total amount of the lime raw material and the silica raw material. Add a predetermined amount of 1% and mix.
The SiO ₂ molar ratio was set to 1.00. Further, water was added, and a raw material slurry was obtained by adjusting the total amount of water to 24 times the solid content. This was subjected to a hydrothermal synthesis reaction in the same manner as in Example 1 to obtain a slurry containing zonotolite crystals as a main component.
Next, glass fiber and Portland cement were added to the slurry obtained above in the same manner as in Example 1, followed by press dehydration molding to obtain a molded body. The physical properties of the obtained molded body are as shown in Table 2.

The composition of the alkali silicate substance used above was as follows.

JIS No. 1 sodium silicate solution: SiO ₂ 36.5%, Na ₂ O 18.0%.

No. 3 sodium silicate powder (manufactured by Nippon Chemical Industry Co., Ltd.): SiO ₂ 58.5%, Na ₂ O 18.5%.

Anhydrous sodium metasilicate powder (manufactured by Yoneyama Pharmaceutical Co., Ltd.): 49.0% of SiO ₂ , 50.0% of Na ₂ O.

Potassium silicate solution (Yoneyama Pharmaceutical Co., Ltd.): 29.0% SiO ₂ , 17.5% K ₂ O.

Example 3 The settled volume of lime milk obtained by slaking quicklime (CaO 95%) in warm water at 80 ° C. and dispersing it in water with a homomixer is as follows:
It was 17-18 ml. Silica powder (98% SiO ₂ ) having an average particle size of 5.4 μm and a predetermined amount of the same JIS No. 3 sodium silicate solution as in Example 1 with respect to the total amount of the lime raw material and the silicic acid raw material were added to the lime milk. The / SiO ₂ molar ratio was 1.00. Further, water was added thereto to adjust the total amount of water to 24 times the solid content to obtain a raw material slurry. This was subjected to a hydrothermal synthesis reaction in the same manner as in Example 1 to obtain a slurry containing zonotolite crystals as a main component.

Next, 3 parts of dimethylpolysiloxane (trade name "SH200 Oil", manufactured by Toray Silicone Co., Ltd.), 4 parts of glass fiber, and 3 parts of pulp were added to 90 parts (solid content) of the slurry obtained above, and mixed. A molded body was obtained in the same manner as described above. The physical properties of the obtained molded body are as shown in Table 3.

In Table 3, the chemical analysis was performed according to the method of ASTM-C871,
(Na ^{+ +} SiO ₃ ^-) soluble ion concentration (ppm) is measured with. In this analysis, it is generally stated that the higher the ion concentration, the safer it is against stress corrosion cracking of austenitic stainless steel.

In Table 3, the water absorption was measured after immersion in water for 24 hours (water head 40
mm).

In Table 3, Sample No. 2 was produced by the method of the present invention, and Sample No. 1 is shown for comparison. The sample
Both ASTM-C692 Nos. 1 and 2 passed the stress corrosion cracking test results.

Comparative Example 1 A slurry containing zonotolite crystals as a main component obtained by the same method as that used when producing sample No. 1 of Example 1 was used.
No. sodium silicate solution, 4 parts of glass fiber,
4 parts of Portland cement was added and mixed, and a molded product was obtained in the same manner as in Example 1. The physical properties of the obtained molded body are as shown in Table 4.

Table 4 shows that when sodium silicate is added to and mixed with the slurry of calcium silicate crystals after the hydrothermal synthesis reaction, the bending strength and wear resistance of the molded body are reduced.

Claims (1)

(57) [Claims] An aqueous slurry of calcium silicate crystals is prepared by subjecting a raw slurry containing a silicate raw material, a lime raw material and water to a hydrothermal synthesis reaction while heating and stirring under pressure to prepare an aqueous slurry of calcium silicate crystals. In the method for producing a molded body, at least one alkali silicate substance of sodium silicate and potassium silicate is added to the raw material slurry,
It is present in an amount of 0.3 to 3% by weight in terms of the total weight of the silicate raw material and the lime raw material in terms of the content of M ₂ O (M represents sodium or potassium) in the alkali silicate substance. A method for producing a calcium silicate molded body, comprising: performing a hydrothermal synthesis reaction on a molded product.