JPS61251556A - Manufacture of water-repellant calcium silicate formed body - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a water-repellent calcium silicate molded body, which is particularly useful as a heat insulating material.

Kohuangofu strained calcium silicate molded bodies are widely used as heat-resistant heat insulating materials, but due to their structure, they are made of hydrophilic calcium silicate crystal hydrate and are porous materials with continuous pores. Due to its characteristics, it easily absorbs water, and when it absorbs water, it not only deteriorates its insulation performance but also promotes the corrosion of metal materials such as tanks and piping that are in contact with it. For this reason, when used as a heat insulator for outdoor tanks, piping, etc., a strict exterior is always applied, but if there is some defect in the exterior and rainwater enters or condensation forms, After all, the above-mentioned troubles will occur.

One effective means for solving the above-mentioned problems in using calcium silicate molded bodies is a method of imparting water repellency to the molded bodies. There are various methods for making a calcium silicate molded body water repellent, but a simple method is to impregnate or apply a water repellent such as alkali methyl siliconate to the calcium silicate molded body and then dry it.

However, with this method, only the surface of the molded body becomes water-repellent, and the water-absorbing nature of the core is not eliminated. Therefore, when cutting for dimension adjustment at the construction site, water-repellent agent is applied to the non-water-repellent cut surfaces. It is a hassle to have to process it. On the other hand, JP-A-57=12385
No. 1, No. 58-2252, No. 59-92963, etc., disclose that when producing a calcium silicate molded body by a method of dehydrating and drying an aqueous slurry of calcium silicate crystal hydrate, A method is described in which silicone oil is mixed into calcium silicate slurry before molding, and according to this method, a calcium silicate molded article having water repellency to the core can be obtained. However, these methods are not suitable for manufacturing pipe covers and the like where dimensional accuracy is important because the dehydrated molded product undergoes a large amount of shrinkage when dried. There is also a problem with the uniformity of the effect of adding silicone oil, and either the surface or the core of the molded product tends to have insufficient water repellency, so it is difficult to improve the water repellency of the molded product as a whole and its reliability. There's room.

Problems to be Solved by the Invention The present invention improves the above-mentioned drawbacks of conventional means for imparting water repellency to calcium silicate molded bodies, and provides excellent water repellency throughout the molded body. It is an object of the present invention to provide a method for producing a calcium silicate molded body having the following characteristics and having good dimensional accuracy.

Means for Solving the Problems The present invention involves preparing a slurry of calcium silicate crystal hydrate by mixing calcareous raw materials and silicic acid raw materials with water and heating the mixture in an autoclave with stirring under pressure. In a method for producing a calcium silicate molded body (hereinafter sometimes referred to as the AP method) in which a dehydrated molded product of the slurry is hardened by heating, silicone oil, Portland cement, and an alkali aluminate are added to the slurry before molding. The above problem was solved by adopting a method of adding and mixing a metal salt.

The reason why polland cement and alkali metal salt of aluminate are added together with silicone oil in the present invention is as follows. First, a means to prevent product shrinkage as described above when silicone oil is added in the process of manufacturing calcium silicate molded bodies by the AP method was investigated, and it was found that it is effective in reducing drying shrinkage in the normal AP method. The addition of Portland cement F, which is known for its properties, was first investigated. As a result, when Portland cement is used in combination, although it is effective in preventing drying shrinkage, there is a strong tendency for silicone oil to migrate to the surface of the molded product during drying, perhaps because the adsorption of silicone oil by calcium silicate crystals is inhibited, and the core It was found that only products with insufficient water repellency could be obtained. It is not impossible to obtain a product with good water repellency right down to the core by increasing the amount of silicone oil added, but in that case, not only will a decrease in strength be unavoidable, but the unit consumption of expensive silicone oil will increase. This significantly increases manufacturing costs. Although the mechanism of action of alkali metal salts of aluminic acid has not yet been elucidated, it has the effect of preventing silicone oil from moving to the surface of the molded product during the drying process, thereby preventing the water repellency of the core of the molded product from deteriorating. Helpful.

The manufacturing method of the present invention will be explained in more detail below.

The step of preparing calcium silicate crystal hydrate slurry in the production method of the present invention is basically carried out in accordance with Japanese Patent Publication No. 45-257.
This is carried out in accordance with the well-known AP method as disclosed in Publication No. 71 and the like. That is, calcareous raw materials such as quicklime, slaked lime, and carbide slag, and silicic acid raw materials such as silica stone are charged into an autoclave with water and stirred under temperature conditions that produce calcium silicate crystal hydrates such as tobermorite and xonotlite. while performing hydrothermal synthesis. There are no particular restrictions on the selection of raw materials and reaction conditions in this step. However, the method of preparing calcium silicate crystal hydrate that provides a product with low specific gravity and high physical properties even when molded with additives such as Portland cement is the method that the present inventors have previously proposed. The method was invented and patented in 1986-205852 (Japanese Patent Application No. 58-205852), that is, by digesting quicklime in which the size of C&○ crystals is 0.3μ or less, the obtained milk of lime is mixed with crystalline silicate raw material and water. This is a method of mixing and heating while stirring under pressure to form a slurry of calcium silicate crystal hydrate having a sedimentation volume of 300++1 or more. Therefore, the following explanation will focus on this method, but as mentioned above, the method for preparing the calcium silicate crystal hydrate slurry in the production method of the present invention is not limited to this.

"Quicklime with a CaO crystal size of 0.3μ or less" used in the above recommended manufacturing method refers to microcrystals in the form of granules or fused particles that are observed when a freshly fractured surface is observed with a scanning electron microscope. It refers to quicklime that is fine with an average particle diameter (if the particles are found to be fused, the size of the primary particles is estimated from their shape) of 0.3μ or less. Such quicklime can most commonly be produced by calcining limestone at relatively low temperatures. Particularly suitable firing conditions are those that satisfy the following equation.

T < -5ot +1250 900 ≦T≦ 1150 t≧0.5 (T is the firing temperature [°C], t is the firing time [Hrl
) This quicklime can be digested by a conventional method using about 10 to 40 times the amount of water or hot water.

Silicic acid raw materials include crystalline materials, such as silica,
Fine powder with an average particle size of about 5 to 15 μm is used.

These raw materials are preferably CaO/S i 02
Mix at a ratio such that the molar ratio is about 0°9 to 1.1,
It is slurried with about 20 to 40 times the amount of water and reacted in an autoclave at high temperature and pressure to produce a calcium silicate crystal hydrate consisting of xonotlite and/or bamorite. Due to the excellent reactivity of slaked lime produced from quicklime as described above, this hydrothermal reaction proceeds much faster than when quicklime with coarse CaO crystals is used as a raw material. The reaction conditions may generally follow those of conventional methods, but
During the reaction, or at least during a period of the reaction, strong stirring is performed so that the sedimentation volume of the obtained calcium silicate crystal hydrate is 300 ml or more, preferably 350 ml or more.
Make sure that it is at least m1. However, here, the sedimentation volume of calcium silicate crystal hydrate means that 500 ml of calcium silicate crystal hydrate slurry adjusted to a concentration of 2% is
Place in a 0I11 500ml graduated cylinder and heat at 20°C.
This refers to the volume of the precipitated calcium silicate crystal hydrate layer when it is allowed to stand for 2 hours. A molded product can be obtained even if the sedimentation volume is less than 300 m1, but it will have a high bulk density.

In addition, after reacting the raw material mixture in the autoclave as described above, the reaction product is not rapidly cooled, but is preferably gradually cooled at a rate of about 5°C/Hr or less, and after it reaches about 100°C or less. When taken out into the atmosphere, spherical secondary particles formed by aggregation of acicular crystals of calcium silicate are formed because the acicular crystals that make up the particles extend in the direction along the surface of the spherical particles. , a spike-like product is obtained (
(Japanese Patent Application No. 59-61217), the calcium silicate crystal hydrate slurry in which such spike-shaped aggregates are formed is a normal calcium silicate crystal hydrate slurry consisting of chestnut bur-shaped crystal aggregates. It has an advantage in that it has better moldability than that of aluminum, and can be molded with high efficiency even when a high percentage of cement or aluminate is added.

Silicone oil, Portland cement, and aluminate are added to the calcium silicate crystal hydrate slurry prepared as above or obtained using any other raw materials and conditions. do.

As the silicone oil, it is possible to use those commonly used as water repellents, such as dimethylpolysiloxane, or those whose methyl groups are partially substituted with phenyl groups, hydrogen atoms, alkyl groups, mercapto groups, etc. It can be either oily or emulsion type. The appropriate amount of addition is 1.5 to 6% by weight based on the solid content in the slurry, that is, the calcium silicate crystal hydrate; if it is less than that, the water repellency of the product will be insufficient, Too much will lead to a decrease in the strength of the product.

As the Portland cement, any of ordinary Portland cement, early strength Portland cement F, ultra early strength Portland cement, moderate heat Portland cement, sulfate-resistant Portland cement, etc. specified in JIS R2510 can be used. The amount added must be 1% by weight or more, but if too much is added,
Even if an alkali metal salt of aluminic acid is used in combination, the water repellency of the core of the molded product will deteriorate. There is also the problem that the specific gravity of the molded body becomes high. Therefore, at most 20% by weight
It is desirable to keep it at a certain level.

As the alkali metal salt of aluminic acid, sodium salt or potassium salt is suitable. In addition, in order to expect a sufficient addition effect, it is desirable that the amount added be approximately 0.5% by weight or more, and approximately 30% or more of the amount of Portland cement added, but if added in large amounts, the surface of the molded product may Since it may impair water repellency or moldability, it is desirable to use it within a range of no more than 5% by weight.

In addition to the slurry of calcium silicate crystal hydrate, reinforcing Mkm materials (such as asbestos, rock wool, plus fiber,
Add appropriate amounts of ceramic fibers, bulbs, rayon cloth, cotton, polypropylene wL fibers, etc., and then add other additives as needed, and then gently stir to mix until the whole is homogeneous.

After completion of mixing, dehydration molding is performed by any method such as press dehydration molding method or extrusion method, and the obtained dehydrated molded product is heated and dried with hot air to obtain a cured water-repellent molded product.

X administration The present invention will be described below with reference to Examples and Comparative Examples.

The shrinkage rate and product properties in the drying process were tested by the following method.

Drying shrinkage rate: Percentage of length shrinkage due to drying relative to the length of the molded article before drying Density 1 Bending strength: According to JIS A9510.

Water absorption rate: * Cut the shape into 60 ml width to make 15 test pieces, and immerse them 30 m + e below the surface of room temperature water for 24 hours. The average value of the values calculated from the sample weight before and after immersion using the following formula. (This value is a guideline for the water repellency of the entire molded article, including the core.)

(W-Wo) x 1 o o /W0 where Wo: weight of the sample before immersion W: weight of the sample after immersion Surface water repellency: The test was conducted as follows according to JIS P8137.

Cut the molded body into pieces with a length of 320 mm and a width of 200 mm to form a test piece (the surface formed during manufacturing is used as the test surface), and fix this to a test piece mounting surface with an inclination angle of 45 °, A vinylet is fixed above the vinylet so that the tip of the vinylet is vertically spaced 10 degrees from the test piece and water falling from the vinylet can flow down about 300 degrees over the test piece. Bielet F
Approximately 0.1a+1 water droplets are placed on the test piece, the traces of the water droplets falling on the test piece are observed, and the water repellency is evaluated according to the following criteria.

Ro: A continuous trace with a uniform width R2: A continuous trace with a width slightly narrower than a water drop R4: A continuous trace but broken in places and clearly narrower than a water drop R6: half of the trace is wet R1: trace 174 is wet with long water droplets R,: more than 1/4 of the trace is scattered with spherical droplets R9: R1 with small spherical water droplets scattered here and there
゜: Things that completely roll off Example l Milk of lime prepared by pouring quicklime with a CaO crystal size of 0.26μ into 24 times the amount of hot water (temperature 90°C) and digesting it for 1 hour while stirring. Add silica powder with an average particle size of 10μ so that the Cab/Sin molar ratio is 1.0, and add water so that the amount of water is 30 times the total amount of quicklime and silica stone. was added to make a uniform slurry, and the mixture was reacted for 4 hours at a temperature of 197°C and a pressure of 15grCm while stirring at 50r in an autoclave.The obtained calcium silicate hydrate was made from xonotlite. The sedimentation volume was 410 ml.

To the above slurry of xonotlite crystals, 4% glass fiber and 2.5% silicone oil TSF451 (dimethylpolysiloxane, viscosity 100 ese, Toshiba Silicone Corporation) were added, and in addition, ordinary Portland cement and sodium aluminate were added. Add.

After stirring at 20 rpm for 1 hour to mix, the mixture is placed in a board molding mold with a length of 910 mm and a width of 300 m, and dehydrated and press-molded to a thickness of 75 mm. % by weight, the same on each side below). The molded product is then dried at 160° C. for 24 hours to obtain a cured molded product.

Table 1 shows the shrinkage rate during drying of the molded product and the characteristic values of the resulting molded product in Examples in which the amounts of Portland cement and aluminate added were varied in the above manufacturing method.

Comparative Examples 1 to 5 Calcium silicate molded bodies were produced in the same manner as in Example 1 except that Portland cement and/or aluminate were not added. The results are shown in Table 1.

Comparative Example 6 The same as Example 6 except that 4% glass fiber and 3% ordinary Portland cement were added to the zonotrite slurry according to Example 1, no aluminate was added, and the amount of silicone oil added was varied. Table 2 shows the results of manufacturing a molded body with a density of 0.109±0°001 in the same manner as in 1.
It was as follows.

Table 2 1.5 0.5 4.662OR.

3.0 0.4 4.2410 R.

6.0 0.4 3.1 26OR.

10.0 0,3, 1.411OR.

Example 3 Slaked lime and silica powder were mixed with a CaO/SiO2 molar ratio of 0.
8 and further added 20 times the total amount of water to make a uniform slurry, and then stirred at 2 Orpm in an autoclave at a temperature of 179°C and a pressure of 1.
The reaction was carried out at 0 Kg/am2 for 5 hours. The obtained calcium silicate hydrate consisted of tobermorite.

To the slurry of the above tobermorite crystals, 3% of lath a fiber, 3% of pulp, silicone oil/TSF48
4 (methylhydrodiene polysiloxane, Toshiba Silicone Corporation) at 3%, early strength Portland cement (
After adding 3% of Nippon Cement Co., Ltd. and 1.5% of potassium flumate and stirring at 25 rpm for 30 minutes, the mixture was put into a board molding mold with a length of 910+mm and a width of 300°C. It was dehydrated and press-molded to a thick thickness. Thereafter, it was dried at 170° C. for 20 hours to obtain a cured molded product.

Table 3 shows the shrinkage rates during drying of the molded bodies and the characteristic values of the obtained molded bodies in the above Examples and Comparative Examples, which were carried out in the same manner as above except that Portland cement and aluminate were not added.

According to the present invention, uniform repellency can be achieved from the surface to the inside of the molded product without deteriorating the dimensional accuracy or physical properties of the molded product, or the moldability in the manufacturing process. Aqueous lightweight calcium silicate molded bodies can be produced.

Table 3 Example Comparative example Density (g/cm') 0.202
0.203 Drying shrinkage rate (%)
0.2 1.4 Bending strength Kg/cm”)
6.7 6.6850°C3H
Shrinkage rate by firing (%) 1.0 1,0
Surface water repellency R1゜
R2 Therefore, even when the water-repellent calcium silicate molded body produced by the production method of the present invention is cut and used at a construction site, there is no need to treat the cut surface with a water-repellent agent. Another advantage of the production method of the present invention is that the silicone oil is uniformly distributed in the molded product and its utilization rate is high, so sufficient ice detection properties can be achieved with a small amount of use, and expensive silicone oil can be used. This means you don't have to use a large amount.

Claims (3)

[Claims] (1) A slurry of calcium silicate crystal hydrate is prepared by mixing a calcareous raw material and a silicic acid raw material with water and heating the mixture under pressure while stirring.
A water-repellent silicic acid characterized by adding and mixing silicone oil, Portland cement, and an alkali metal salt of aluminate, dehydrating the slurry after mixing, and curing the resulting dehydrated molded product by heating and drying. Method for producing calcium molded bodies. (2) 1.5 to 6% by weight of silicone oil, 1.0% by weight or more of Portland cement, and an amount of the above Portland cement within the range of 0.5 to 5% by weight based on the solid content in the slurry. The manufacturing method according to claim 1, wherein the alkali metal salt of aluminate is added in an amount of 0.3 times or more. (3) As a calcareous raw material, the size of CaO crystal is 0.3
The manufacturing method according to claim 1, which uses quicklime having a particle diameter of μ or less.