JPS58125653A - Manufacture of calcium silicate shape - 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 calcium silicate molded body. Specifically, the present invention relates to a method for producing a calcium silicate molded body that has a low bulk density and excellent heat resistance, mechanical strength, and dimensional stability, and is therefore suitable as a heat insulating material or a heat insulating material.

Calcium silicate molded bodies, especially those containing xonotlite as a main component, have a heat resistance of 70,000 or higher and are therefore suitable as heat insulating materials and heat insulating materials.

Generally, calcium silicate molded bodies used for heat insulating materials and heat insulating materials are required to have low thermal conductivity and high mechanical strength.

However, in order to lower the thermal conductivity, it is necessary to produce a molded product with a low bulk density, but as the bulk density decreases, the strength also decreases, so the molded product has a low bulk density and a high mechanical strength. is extremely difficult to manufacture.

Some of the present inventors have found that an effective method for producing such compacted bodies is to dehydrate and mold an aqueous slurry containing a specific calcium silicate aqueous product, followed by steam curing. I proposed to the headliner that this is the case. (Japanese Patent Application No. 5-2-6362/) This method is extremely advantageous, but since the calcium silicate hydrate during dehydration molding is very bulky, the molding pressure is high and the molding process takes time. . In addition, there was a further problem that the molded body contracts in the direction of the molding pressure, which should be improved.

In view of this, the present inventors conducted a loading study and found that if wollastonite is added to a slurry containing a specific calcium silicate hydrate, molded, and then steam-cured, moldability is good, compared to conventional methods. Compared to the calcium silicate molded body obtained by the above method, a calcium silicate molded body having the same bulk specific gravity has a higher bending strength, and a similar bending strength has a lower bulk specific gravity. Heading The present invention has been arrived at.

That is, the gist of the present invention is an aqueous slurry containing a calcium silicate hydrate having a sedimentation volume of / j crd / 9 or more obtained by reacting a calcareous raw material and a silicate raw material dispersed in water under heating. A method for producing a calcium silicate molded body by dehydrating and molding and then curing with steam, characterized by adding wollastonite to the aqueous slurry so that the molded body contains t-6θ weight. The present invention relates to a method for producing a calcium silicate molded body.

In the 3- method, the siliceous raw materials include natural products such as diatomaceous earth and silica stone, silicon dust, and silica obtained by reacting hydrosilicofluoric acid and aluminum hydroxide, which are by-produced in the wet phosphoric acid production process (hereinafter referred to as silica). Industrial by-products such as wet brown phosphoric acid by-product silica) are used. Further, as the calcareous raw material, any of the well-known materials such as quicklime, slaked lime, and carbide slag can be used, but quicklime is particularly suitable.

Mixing molar ratio of siliceous raw material and calcareous raw material (Oak/EIi
O, ) is usually θ,,! when xonotlite is desired as the calcium silicate hydrate crystal in the final molded product. r~
If crystalline tobermorite is desired, it is usually within the range of 0.2 to θ.

The amount of water for dispersing both of the above raw materials is / based on the solid content of the raw materials.
It is sufficient that the amount is at least twice the weight of the yoke, and a range of 17 to yo times the weight is particularly preferable.

Of course, if the water in the calcareous material-containing slurry is insufficient to disperse both materials, more water may be added.

By reacting the above-mentioned raw materials dispersed in water under heating, an aqueous slurry containing silica calcium hydrate crystals can be obtained.

The sedimentation volume of calcium silicate hydrate crystals in the aqueous slurry is /1all/f or more, preferably /r~3θcd/
It is necessary that f. Sedimentation volume / s crl
/v, a molded article with high strength cannot be obtained.

Here, the sedimentation volume is a value calculated by the following equation (11).

In formula (n), W is the total weight of the solid content of the raw material (for example, quicklime decasilicate raw material) (if a calcareous raw material other than quicklime is used, calculate the total weight by converting it to quicklime), and ■
is the volume occupied by the solid content that settled after the slurry obtained after the reaction was left undisturbed for 29 hours. In practice, it is usually determined as follows. First, the total weight W obtained after the reaction. Collect W and f from the slurry in step 2 into a graduated cylinder, and add this to 2'1.
The volume occupied by the settled solids after being allowed to stand for a period of time is measured, and calculated using the following formula (1).

■ In the table, W has the same meaning as in the formula and indicates the total weight of the raw materials.

As a method for increasing the sedimentation volume to 11,771 or more, there is a method in which the reaction is carried out under stirring at a temperature of /3θC or higher, particularly 75θ to 23θC, most preferably 16θ to 210C. In this case, the reaction system must be kept in a liquid state, and therefore the reaction is carried out under pressure.

Furthermore, the calcium silicate hydrate in the slurry needs to be a tobermorite group compound.

Various types of calcium silicate hydrate crystals are known, and they are generally described in the book by Taylor (H3P, *, The Chemistry Opcement).
fOemθntθ)-1 Volume 1, Volume 1! It is lpl according to the classification shown in the table ■ on the page. Compounds of the tobermorite group include tobermorite kel, O-8-H(1), a-s-
Hm and crystalline tobermorite are included, but any of them may be used. Calcium silicate hydrate crystals are produced by tobermorite gel→0-S-I((IT)→0-8-)1(1
) → / / W, it's enough to just take the time. In other words, if the reaction temperature is increased or the reaction time is increased, the crystals will transition in the direction of the arrow (→).

If the reaction is carried out in a temperature range to achieve the first condition, compounds of the tobermorite group are usually obtained. However, if the reaction temperature is particularly high or the reaction time is particularly high, Xonotolyte X may be obtained, so in that case, the temperature may be lowered or the reaction time [111] may be shortened. In addition, when crystalline l.bamorite is desired as crystals in the final molded product, the calcium silicate hydrate in the slurry is tobermorite gel, O-0-8-H or 0-8-H ([1 It is necessary that

In the present invention, wollastonite is added to the aqueous slurry. Wollastonite here is a general term for those explained in Nodobook 1 (edited by the Gypsum and Lime Society), p. 27-, p. 27, and can be classified as follows.

That is, wollastonite (chemical formula 〇aO-5in2) has a low temperature type (β-C!ao 1181.02) and a high temperature type (α
-Oa, 0-81, O,) is classified as 211'i. The low-temperature type changes to the high-temperature type at temperatures above about 2°C. Low-temperature types include natural products and synthetic products obtained by heating and dehydrating xonotlite, while high-temperature types are mainly synthetic products.

The wollastonite used in the present invention may be any of the types mentioned above, but a low-temperature type natural product with significant fibrous crystals is particularly preferred. In addition, the amount of wollastonite to be added is approximately 60%, preferably 10%, and 10% in the final molded product.
It is preferable to use it in such a way that it contains a weight of 10%, particularly preferably 1%, /θ~35%, and if it is less than 10% it will not give a sufficient effect in terms of moldability. Moreover, if it exceeds the θ weight coefficient, the quantification of the molded product is inhibited, and the amount of calcium silicate hydrate forming the matrix is relatively reduced, so that the mechanical strength of the molded product decreases, which is not preferable.

In the present invention, reinforcing fibers are usually added to the aqueous slurry. As reinforcing fibers, any of a variety of well-known reinforcing fibers may be used; for example, asbestos, rock wool, glass fiber, etc. may be used. Usually, O35~/θ weight-II in the final molded product
%.

The above-mentioned aqueous slurry thus obtained is shaped in a conventional manner by depressurization. The pressure at that time is usually /~λ
The range is θθkP/cdtG, and the bulk ratio of the molded body is adjusted by adjusting the piston stroke of the pressure molding machine.

Next, the obtained molded body is subjected to steam curing under pressure, so-called autoclave curing, according to a conventional method.

By this steam curing, the crystals of the molded body are spread over tobermorite gel, a-s-H (I) or O-8-H (■) (in the case of crystalline tobermorite) and xonotlite, in the case of crystalline tobermorite. It is necessary to transfer to xonotlite. The crystal transformation caused by this steam curing makes it possible to obtain a molded article with low bulk density and excellent mechanical strength. Water vapor pressure can generally be reduced to a high degree over time, but is usually in the range θky/ti G from evening to night.

If xonotlite is desired as the crystal of the final molded product, 7.2 to θkq/crll a, and if crystalline tobermorite is desired, 6 to 30 kg/cyll.
() Water vapor is preferred. Under these conditions, the above-mentioned transformation is usually easily carried out. If the transformation does not occur as desired, which is extremely rare, for example, if xonotlite is desired but crystalline tobermorite is obtained, increasing the steam pressure or extending the steam curing time will solve the problem. If you want crushed crystalline tobermorite and can obtain xonotlite, you can conversely lower the steam pressure or shorten the steam curing time.

In applications requiring high heat resistance, it is preferable to transform it into xonotlite.

The present invention has been described in detail above, and according to the method of the present invention, a material with a bulk density θ, lr f /cA has a bending strength of 10 kg, a material with a bending strength of 10 kg or more, and a material with a bending strength of θ8.2 Obtain a calcium silicate molded body that has an af of 1 or more and a bending strength that is about 1 times higher than that obtained by conventional methods at the same bulk density, with excellent moldability in terms of molding pressure and molding speed, and good dimensional stability. be able to.

In addition, the resulting molded product has excellent heat resistance due to the intertwining of heat-resistant wollastonite and matrix calcium silicate hydrate crystals, so it can be used as a general heat insulating material, heat insulating material, etc. It can be expected to have a wide range of applications as a fireproof insulation material for various industrial applications in furnaces, drying furnaces, ducts, and the aluminum industry.

EXAMPLES Next, the present invention will be explained in more detail with reference to examples, but the present invention is not limited to the following examples as long as the gist of the invention is exceeded.

In addition, 1 part 1 and [person 1] indicate husband [weight part 1 [weight 1←].

Examples/~A and Comparative Examples/~3 Quicklime (Rin 6.2 Section OaO) Add warm water to 9.6 parts of St, digest 17, and add silica stone (Rini, Ribeak 11102)
) After adding 5019 parts of water, the total water was 2% of the solid content.
Water was added to make 7.5 parts. The h fc @ 7a solution thus obtained was 15 to 9 in an autoclave.
/CrflG When stirred and reacted for 2.0 hours under the condition of 2θθC, the sedimentation volume, O8 of 2/f/crfr
An aqueous slurry containing H was obtained. To this aqueous slurry, 3 parts of alkali-resistant glass fiber and wollastonite were added in the types and amounts shown in the table/comparative example 3, in which alumina was added). The slurry was adjusted so as to have the following properties, and was dehydrated under pressure at a pressure of 10 kg/crfl to the dimensions of 3θθ x 300 x 0 (length x width x thickness).Then, the obtained molded body was placed in an autoclave, Water vapor/i ky/at/IG/z
After steam curing for 7 hours, /! It was dried in OC for 1 hour.

Table 1 shows the pressing time, thickness shrinkage rate after drying, bulk density, bending strength, residual shrinkage rate and weight loss after heating at 10θθC for 3 hours.

Comparative example d~j 4t 6.7 parts of quicklime (RI63.2 CIq, O) was digested by adding warm water, and 2 parts of silica (wet phosphoric acid by-product silica SXO, ?7.r4) was added to this. After that,
Water was added so that the total amount of water was %J L /θ weight times the solid content. The suspension solution thus obtained was stirred at θC for λ hours to react, and then allowed to stand at room temperature for 29 hours to ripen. The settling volume of this aqueous slurry is ♂ge/1
and the product was a gel. 3 parts of alkali-resistant glass fiber was added to this aqueous slurry, and only in Comparative Example Z, natural β-0aO* Si, 0. was added in an amount of 3θ weight % based on the total solid content. The subsequent steps were carried out in the same manner as in Example 1 to obtain the results shown in Table 2.

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Claims (1)

[Claims] (1) After dehydrating and molding an aqueous slurry containing calcium silicate hydrate with a sedimentation volume of 1 crll/r or more obtained by reacting a calcareous raw material and a silicic raw material dispersed in water under heating, steam curing is performed. A method for producing a calcium silicate molded body by adding wollastonite to the aqueous slurry so that the molded body contains j -4θ weight -1 t%. Method.