JPH0135790B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a calcium silicate molded body having excellent water repellency. Specifically, it has a low bulk density, good fire resistance, heat resistance, mechanical strength, and dimensional stability, and is uniformly water-repellent to the inside, making it suitable for fire-resistant coatings, fire-resistant insulation materials, or heat retention. The present invention relates to a method for producing a calcium silicate molded body suitable as a cold insulating material. In general, calcium silicate molded bodies used as fireproof coating materials, fireproof insulation materials, and heat/cold insulation materials are required to have low thermal conductivity, and in recent years, products with low bulk density and high strength have been produced. . However, reducing the weight of the product inherently increases the porosity and thus increases the potential water absorption. Therefore, once water is absorbed, there is a significant increase in thermal conductivity, which has the disadvantage of reducing its function as a heat insulating material and a heat/cold insulating material. For this reason, various attempts have been made to obtain water-repellent calcium silicate molded bodies. For example, a water repellent containing alkali methyl siliconate is brushed onto the surface of a calcium silicate molded body, and then
There are known drying methods. However, even when such conventional methods are applied to calcium silicate molded bodies with a particularly low bulk density, the surface water repellency is still not sufficient, and the cutting process performed at the construction site for dimension matching, etc. However, if a new surface is created due to a break or the like, the water repellent agent must be applied to that surface again and dried, which is extremely inconvenient and time consuming. As a result of intensive studies on this point, the present inventors discovered that the intended purpose could be achieved by adding and mixing a specific emulsion to an aqueous slurry containing calcium silicate hydrate, and developed the present invention. It has come to completion. That is, the gist of the present invention is to emulsify an aqueous slurry containing calcium silicate hydrate obtained by reacting a calcareous raw material and a silicate raw material dispersed in water under heating with an anionic surfactant. The present invention relates to a method for producing a water-repellent calcium silicate molded article, which comprises adding and mixing an emulsion of dimethylpolysiloxane and/or its derivatives, dehydration molding, drying or steam curing, and then drying. The present invention will be explained in detail below. As the calcium silicate hydrate slurry used in the present invention, one obtained according to a known method can be used. That is, a calcium silicate hydrate obtained by reacting a silicic acid raw material and a lime raw material dispersed in water under heating, preferably with a sedimentation volume of
An aqueous slurry containing 15 cm ³ /g or more of calcium silicate hydrate consisting of a compound of the tobermorite group can be used. Silicic acid raw materials include natural products such as diatomaceous earth and silica stone, silicon dust, and silica obtained by reacting hydrosilicic acid, a by-product of the wet phosphoric acid manufacturing process, with aluminum hydroxide (hereinafter simply referred to as wet phosphoric acid by-product silica). Industrial by-products such as These silicic acid raw materials may be amorphous or crystalline, but
Amorphous materials such as diatomaceous earth, wet phosphoric acid by-product silica, and silicone ducts are preferred because it is easier to produce calcium silicate hydrate with a sedimentation volume of 15 cm ³ /g or more. As the lime raw material, conventionally known materials such as quicklime, slaked lime, and carbide slag can be used. Mixing molar ratio of silicic acid raw material and lime raw material (CaO/
SiO ₂ ) is usually selected from the range of 0.7 to 1.2. When these two raw materials are dispersed in water at least 15 times the weight of the solid raw materials and subjected to a hydrothermal reaction at 80 to 230°C for 30 minutes to 10 hours according to a conventional method, an aqueous slurry containing calcium silicate hydrate is obtained. is obtained. Calcium silicate hydrate is generally produced by Taylor (H.
FWTaylor) "The Chemistry of Cements" Vol. 1, page 182. In the present invention, tobermorite gel, C-S-H (),
It may be a tobermorite group compound selected from C-S-H() and crystalline tobermorite, or xonotrite. In the present invention, the calcium silicate hydrate in the aqueous slurry preferably has a sedimentation volume of 15 cm ³ /g or more. Here, the sedimentation volume is a value calculated by the following equation (). Sedimentation volume = V/W... () In formula (), W is the total weight of the raw materials (lime raw material + silicic acid raw material), and V is the solid content that settled after leaving the aqueous slurry obtained after the reaction for 24 hours. It is the volume it occupies. In practice, it is usually determined as follows. First, from the aqueous slurry with a total weight of Wog obtained after the reaction, ₁ g of W was collected into a graduated cylinder, and this was left to stand for 24 hours to calculate the volume occupied by the settled solids.
Measure V ₁ cm ³ and calculate from the following formula (). Sedimentation volume=V ₁ /W ₁ ×W/W ₀ () Note that W has the same meaning as in formula () and indicates the total weight of the raw materials. The method of increasing the sedimentation volume to 15 cm ³ /g or more is as follows:
The reaction is carried out under stirring at 130°C or higher, especially between 150 and 230°C.
Optimally, a method carried out at 160 to 210°C is suitable. In this case, the reaction system must be kept in a liquid state, and therefore the reaction is carried out under pressure. An emulsion of dimethylpolysiloxane and/or its derivative emulsified with an anionic surfactant is added and mixed to the aqueous slurry thus obtained. As the dimethylpolysiloxane and its derivatives, those having a clay content at 25° C. of 0.5 to ^{10 10} centistokes, preferably 10 ² to ^{10 8} centistokes are used. Specifically, SH-200 (trade name, manufactured by Toray Silicone Co., Ltd., dimethylpolysiloxane), KF-54 and
KF-99 (trade name, manufactured by Shin-Etsu Chemical Co., Ltd., methyl phenyl polysiloxane and methyl hydrodiene polysiloxane), SF-8418 (trade name, manufactured by Toray Silicone Co., Ltd., methyl carboxy polysiloxane), both Examples include modified dimethylpolysiloxane and aminomethylpolysiloxane having an OH group at the end. As an anionic surfactant, the formula −COOM
Carboxylate salts of the formula -SO ₃ M, sulfonate salts of the formula -OSO 3 M and sulfonate salts of the formula -OSO ₃ M

[expression] or

A phosphoric acid ester salt having an anionicity-imparting group arbitrarily selected from the phosphoric acid ester salts represented by the formula is used. In the formula, M represents K, Na, NH ₄ or triethanolamine. Specifically, for example, Diprozin K-25 (trade name, manufactured by Toho Chemical Industry Co., Ltd., potassium dehydroabietate), Perex OTP, Neo Perex F
-25, Perex NB, Demol NL, Levenol WX, Levenol WZ, Electro Stripper K and Demol EP (the above products, Kao Atlas
Co., Ltd., sodium dialkyl sulfosuccinate, sodium dodecylbenzene sulfonate, sodium alkylnaphthalene sulfonate, sodium naphthalene sulfonate formalin condensate, sodium polyoxyethylene alkyl ether sulfate, sodium polyoxyethylene alkyl phenyl ether sulfate, polyoxy Potassium ethylene dialkyl ether phosphate and sodium polyacrylate), NIKKOL SMD-10 (trade name, manufactured by Nikko Chemicals Co., Ltd., sodium salt of styrene-maleic acid copolymer), and the like. The emulsion of the present invention contains 0.1 to 30 parts by weight of anionic surfactant, preferably 0.1 to 30 parts by weight, based on 100 parts by weight of the dimethylpolysiloxane or its derivative.
Add and mix 1 to 15 parts by weight and follow the usual method.
homomixer, homogenizer, colloid mill,
It can be easily obtained by emulsifying using an emulsifying machine such as an ultrasonic emulsifying machine. Furthermore, the emulsion of the present invention is
By emulsion polymerizing cyclic siloxane monomers such as {(CH ₃ ) ₂ SiO} ₃ and {(CH ₃ ) ₂ SiO} ₄ with the above anionic surfactant in the coexistence of an acidic catalyst such as dodecylbenzenesulfonic acid. You can even get it. In the present invention, SH-490, SM-8701 and SM-7060, which are commercially available as emulsions of dimethylpolysiloxane or its derivatives (all of which are manufactured by Toray Silicone Co., Ltd., are anionic emulsions of dimethylpolysiloxane). Roussillon), SM−
8706 (trade name, manufactured by Toray Silicone Co., Ltd., dimethylpolysiloxane double-terminated OH group-modified anion emulsion) and the like can also be advantageously used. The amount of the emulsion of the present invention added to the aqueous slurry affects the water repellency of the resulting molded product, but
If the amount added is too large, the organic content (hydrocarbon groups) contained in the emulsion will reduce the fire retardancy, fire resistance, heat resistance, etc. It is added in an amount of 20% by weight or less, preferably 1 to 15% by weight. The mixture of the aqueous slurry and emulsion thus obtained is pressurized and dehydrated after adding reinforcing fibers in a conventional manner. Of course, the reinforcing fibers may be added in advance before producing the slurry. The temperature and pressure at that time are usually 30 to 80℃ and 1 to 200℃.
Kg/cm ² G, and the bulk density of the molded product is adjusted by adjusting the piston stroke of the pressure molding machine. Any of a variety of well-known reinforcing fibers can be used, such as asbestos, rock wool, glass fiber, pulp, etc. It is usually added to the final molded product in an amount of 0.5 to 10% by weight. Next, the obtained molded body is subjected to steam curing under pressure, so-called autoclave curing, according to a conventional method.
Through this steam curing, calcium silicate hydrate,
Tobermorite gel, C-S-H () or C-
In the case of S-H(), the transition is made to crystalline tobermorite or xonotlite, and in the case of crystalline tobermorite, it is transferred to xonotrite. The crystal transformation caused by this steam curing makes it possible to obtain a molded article with low bulk density and excellent mechanical strength. Generally, the higher the water vapor pressure, the shorter the reaction time, but it is usually in the range of 5 to 50 kg/cm ² G. 12 to 40 if xonotlite is desired as crystals in the final molded product
Kg/cm ³ G, and if crystalline tobermorite is desired, 6 to 30 Kg/cm ³ G water vapor is suitable. Under such conditions, the above-mentioned transfer is usually easily carried out. If the transfer does not occur as desired,
Such cases are extremely rare, but if, for example, you want xonotlite but crystalline tobermorite is obtained, you can increase the steam pressure or extend the steam curing time; If xonotlite can be obtained, conversely, the steam pressure should be lowered or the steam curing time should be shortened. In applications requiring high heat resistance, it is preferable to transform it into xonotlite. Then, by drying, a desired calcium silicate molded body can be obtained. In the case of a molded article obtained by dehydrating and molding a mixture of an aqueous slurry containing xonotlite and the emulsion, drying treatment may be performed immediately without performing the steam curing. In this way, a calcium silicate molded body having a low bulk density, good fire resistance, heat resistance, mechanical strength, and dimensional stability, and which is uniformly water-repellent to the inside can be obtained. Next, the present invention will be explained in more detail with reference to Examples. In the examples, "parts" indicate "parts by weight."
Further, the water repellency (contact angle) of the core portion of the free fracture surface was measured as follows. That is, the molded body was placed so that the fractured surface was horizontal, and a water droplet of about 0.05 to 0.1 ml was gently dropped from above, and the angle formed by the tangent between the fractured surface of the molded body and the outer peripheral edge of the water droplet was measured. Examples 1 to 13 and Comparative Examples 1 to 5 43.2 parts of quicklime (CaO 98%) was digested by adding warm water, and silica stone (SiO ₂ 97%, Al ₂ O ₃ 1.2%,
After adding 46.8 parts of Fe ₂ O ₃ (0.09%), water was added so that the total amount of water was 30 times the solid content. The suspension thus obtained was placed in an autoclave for 15
Kg/cm ³ G and 200° C. for 2.5 hours with stirring, an aqueous slurry consisting of tobermorite group compounds with a sedimentation volume of 23 cm ³ /g was obtained. To this aqueous slurry, 90 parts of the dimethylpolysiloxane or its derivative shown in Table 1 was emulsified with 10 parts of an anionic surfactant in a homomixer, and an emulsion obtained was added to the emulsion, which was 10 parts by weight of the molded weight in terms of non-volatile content. Alkali-resistant glass fiber 3%
The bulk density of the molded product is 0.10g/
The liquid volume was adjusted so that the volume was 3 cm ³ and pressure dehydration molding was performed. The obtained molded bodies were placed in an autoclave, steam-cured for 7 hours at a steam pressure of 10 Kg/cm ² G and 180° C., and then dried to obtain molded bodies each having a thickness of 30 m/m. The bulk density of these molded bodies was within the range of 0.10±0.02 g/cm ³ and the bending strength was within the range of 5 ± 1.5 Kg/cm ^{2 .} The water repellency was excellent as shown in Table 1. On the other hand,
The molded bodies obtained in Comparative Examples 1 to 5 did not exhibit water repellency and absorbed water droplets.

【table】

[Table] Examples 14 to 17 and Comparative Examples 6 to 7 The same procedure as in Example 1 was carried out except that the emulsion of dimethylpolysiloxane or its derivative shown in Table 2 was used, and the thickness was 30 m/m and the bulk density was 30 m/m.
A molded article having a weight of 0.10±0.02 g/cm ³ and a bending strength of 5±1.5 Kg/cm ² was obtained. Among them, the water repellency of the core portion of the free fracture surface of the molded bodies obtained in Examples 14 to 17 was excellent as shown in Table 2. In contrast, the molded bodies obtained in Comparative Examples 6 and 7 did not exhibit water repellency and instantly absorbed water droplets.

【table】

Claims (1)

[Claims] 1 Dimethylpolysiloxane and/or its dimethylpolysiloxane obtained by emulsifying with an anionic surfactant into an aqueous slurry containing calcium silicate hydrate obtained by reacting a calcareous raw material and a silicic raw material dispersed in water under heating. 1. A method for producing a water-repellent calcium silicate molded article, which comprises adding and mixing an emulsion of a derivative, dehydrating it, molding it, drying it or drying it after steam curing.