JPS6042266A - Manufacture of small free lime fiber cement board - 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 suppresses the increase in the amount of free lime accompanying cement hardening,
This invention relates to a fiber cement board that prevents deterioration of the paint film. Conventionally, fiber cement boards made by blending fibers with cement are generally known, and among these, asbestos cement boards using asbestos as the fibers have properties such as durability, weather resistance, and nonflammability.
Since it is suitable as a building material, it has been used as an interior and exterior material for various buildings.

However, conventional asbestos-cement boards have disadvantages such as deterioration of the coating film due to free lime.

That is, generally when Portland cement hardens, a large amount of slaked lime is produced as a by-product, as shown by the following equation.

acao・5i02 +bH20-+ ccao-ds
i02xH20+eCa (Of()2 a-2,5~3.Oc/d''=1.5 The amount of free lime theoretically reaches 20 to 30 parts of cement, and continues to be generated for many years.

For this reason, when a paint is applied to the light surface of a conventional asbestos cement board, the paint film deteriorates due to the strong alkali of slaked lime liberated from the asbestos cement board.

As a result, the paint becomes dull, discolored, whitened, unevenly colored, chalked, etc., and the aesthetic appearance is impaired. Even in the case of alkali-resistant paints, such as acrylic or acrylic urethane paints, deterioration of the paint film due to the combined action of ultraviolet rays and free lime is unavoidable, especially when used for exterior materials.

The present invention solves the above-mentioned conventional problems and provides a method for manufacturing fiber cement boards that prevents the need for paint films. The cement has a composition of 5 to 35% by weight and 6% by weight, and the cement is composed of blast furnace slag, 100 to 70% by weight of Portland cement, and 0 to 30% by weight of an inorganic admixture, and the weight ratio of blast furnace slag to Portland cement is 3. 0~9,
The method is characterized in that a plate-shaped body is cut out from an aqueous slurry having a composition of 0, and the plate-shaped body is dehydrated and molded under a pressure of 50 kg/cr1 or more, and then cured and hardened.

The present invention will be explained in detail below along with examples.

In the present invention, the following composition is used as the raw material for the fiber cement board.

Cement: 95 to 65% by weight Fiber material: 5 to 35% by weight The above-mentioned cement is a mixture of blast furnace slag, Portland cement, and, if necessary, an inorganic admixture.

Here, the Portland cement serves as a binder. As the Portland cement, ordinary Portland cement can be used.

Next, blast furnace slag is a slag produced in iron-making blast furnaces, and is a molten material consisting of impurities in iron ore, coke ash, and limestone.

The blast furnace slag is free lime E generated during the cement water utilization process.
The blast furnace slag itself is hydrated and self-hardens in the presence of the alkaline stimulant. The particle size of blast furnace slag usually has a specific surface area of 3000 d/
It only needs to be about P, and there is no particular restriction as long as it can be mixed uniformly.

Next, the blending ratio of blast furnace slag and Portland cement in the above cements is adjusted to a weight ratio of blast furnace slag/Portland cement) = 3.0 to 9.0. If it is less than 3.0, the curing speed and bending strength of the product will be ensured, but free lime will not be suppressed sufficiently. On the other hand, if it exceeds 9.0, free lime deposits are significantly suppressed, but the curing speed of the green board is significantly delayed, which is unfavorable in terms of life process.

Next, fibrous materials refer to inorganic and organic fibrous materials, including natural fibers and synthetic fibers.

Asbestos is the most suitable fiber material, but fiber materials other than asbestos are also suitable. For example, natural fibers such as cellulose,
Indestructible fibers such as alkali-resistant glass fibers and carbon fibers,
Synthetic fibers such as vinylon, nylon, and polypropylene can be used.

Further, the blending amount of the fiber material is adjusted to 5 to 35 times. The reason for this is that if it is less than 5% by weight, the amount of fibers will be too small and will lack holding power when raw boards are cut out from the raw material slurry, resulting in a greater tendency for cement to flow out.

On the other hand, if it exceeds 35% by weight, the binding force of the cement is insufficient, and even if the molding pressure is increased, it cannot be densified, resulting in a low density and
This is because the strength becomes low.

Incidentally, the above-mentioned various types of fiber materials may be used alone, or various types of fiber materials may be used in an appropriate combination. When organic fibers are used, the amount mixed in the raw material slurry is preferably about 5% by weight so as not to impair the nonflammability of the final product.

Next, an inorganic admixture is added when asbestos is not used as the fiber or when the amount of asbestos used is small. As mentioned above, it is possible to use materials other than asbestos as the fiber material, but even if the fiber material is made entirely of materials other than asbestos, or even if asbestos and other fiber materials are combined, the amount of asbestos is extremely small. In some cases, inorganic admixtures are added. When the amount of asbestos is at least 5% by weight, preferably 10% by weight or more, no inorganic admixture is required.

The inorganic admixture plays a role in suppressing dimensional changes in the final product at high temperatures. That is, when curing fiber cement boards, if a large number of curing boards are usually piled up for curing, the water use of the cement causes a severe temperature rise, and in summer the temperature rises to near the boiling point of water. Also, in the event of a fire, they are exposed to extremely high temperatures. Inorganic admixtures suppress dimensional changes caused by severe dehydration and drying at high temperatures when the amount of asbestos is small. As the inorganic admixture, inert calcium carbonate powder, fine silica sand powder, and other mineral powders can be used. Particularly suitable are needle-like or flake-like materials having a high aspect ratio, such as powdery materials such as olastonite, mica, and vermiculite.

Usually, the particle size of these particles should be about 300 to 40 mesh.

Calcium carbonate powder, fine silica sand powder, and other mineral powders commonly used as aggregates can be used.

Next, the fiber cement board of the present invention is produced by cutting out a plate-like body from the aqueous slurry having the above-mentioned raw material composition, and cutting out the plate-like body in 50 kl. /
It is manufactured by dehydration molding under pressure of C11 or higher and then curing and curing.

The plate-like material may be produced using a round screen, Fourdrinier, Magnani type or other paper making machine conventionally used in the field of asbestos cement.

The raw board that has been cut out is then pressed to 50 kg/c using a press machine.
Dehydrated and molded under pressure of td or more. Molding pressure is 50kg
When it is less than /cr1, the bulk specific gravity of the final product decreases, resulting in a decrease in strength, and also tends to have poor freeze-thaw resistance.

The pressure applied varies depending on the type of fibers mixed in and the expected thickness strength of the final product, but as the amount of fiber increases, it is usually necessary to increase the pressure to suppress the increase in bulk specific gravity. .

In particular, in the case of a thin plate with a large amount of fibers, for example, in the case of a thickness of 61111 or less, it is preferable to apply a pressure of 80 to 9/cr1 or more.

The pressure-formed raw board is cured uniformly and sufficiently in a humid chamber and then dried to form a product.

Regarding the above-mentioned extraction curing and curing process, since the hydration rate is slower in the method of the present invention than in conventional methods, it is preferable to carry out heat curing as appropriate depending on the manufacturing conditions.

Examples and comparative examples of the present invention are shown below.

In order to manufacture the fiber cement board of the present invention, an aqueous slurry was made using the raw materials shown in Table 1 and the mixing ratios shown in Table 2.

Next, a green board with a thickness of h 6 ram was produced using a commonly used circular mesh paper machine for producing asbestos cement boards.

Subsequently, pressure molding was performed at the molding pressure shown in Table 2, and the temperature was 30°C.
The final product was cured for two weeks in a curing chamber at 95% RH. Next, tests shown in Table 3 were conducted on the fiber cement board of the present invention.

The results are shown in Table 4 (Examples 1 to 4). On the other hand, conventional asbestos cement boards and the like were made with the compositions shown in Table 2 using the raw materials shown in Table 1, and the same actual measurements as for the fiber cement boards of the present invention were carried out. The results are shown in Table 4 as a comparative example (Comparative example 1
~4).

Table 1 Raw material blast furnace slag Component % CaO41,8,5i0234.
5. ) d3*os 15.5Mg0 O,5, Fe,
0.0.8, S 1.0 plane 3980 cM
P True specific gravity 2,90 Portland cement JIS
Specified in R5202 Asbestos Chrysotile from Canada Class 4 alkali-resistant glass fiber (ARG) High zirconia glass fiber, thickness 13 μm 1 length 12 Mica High aspect ratio mica from Canada Particle size 80 mesh Cellulose fiber NBKP Vinylon 1.8 denier , Length 6 Dragon table 3 Test items and methods Bending strength test j JIS A3403 Bulk specific gravity test and dimensional change test due to water absorption: JIS
A3418 Free lime content; Cresol method coating film stability test: Solvent-based acrylic drug at 150 f
15cm x 15crn from the test piece coated at the ratio of /-
A test piece of the size was cut out, eight test pieces were stacked with the coated side facing up, and the test pieces were left in a humidity box at 50° C. and humidity 100* for one month. Thereafter, the coating surfaces of the seven test pieces excluding the top test piece were observed.

Table 4 Test results In the same examples as above, in Example 1, the weight ratio of slag and cement was about 4, asbestos was used as the fiber reinforcement, and the amount of free lime was 0.40%.On the other hand, in comparison Example 4 is a conventional asbestos cement board in which the fibers are the same as in Example 1, but only cement is used without using slag.As is clear from Table 4 above, Comparative Example 4 has poor strength and dimensional stability. Although it was excellent, the amount of free lime was as high as 6.87 fI, and the stability of the coating film was poor.

Next, in Example 2, the same fibers as in Example 1 were used, the slag to cement ratio was about 8, and satisfactory results were obtained in terms of strength, free lime content, and coating stability.

On the other hand, in Examples 3 and 4, asbestos was not used, reinforcing fibers other than asbestos were used, and mica was added as an inorganic admixture for dimensional stabilization. As is clear from Table 4 above, the fibers of Comparative Examples 1 and 2 are the same as those of Examples 1 and 2, but since the slag cement ratio is outside the range of the present invention, the amount of free lime in Comparative Example 1 is large. There were also problems with membrane stability. Furthermore, although the amount of free lime in Comparative Example 2 is very small, it has the disadvantage that curing is slow and production is hindered.

Furthermore, Comparative Example 3 had the same formulation as Example 4, but the molding pressure was low, resulting in low strength due to low specific gravity.

As described above, according to the coating method of the present invention, it is possible to easily produce a fiber cement board with an extremely low amount of free lime and a high coating film stability.

Patent applicant: Suno Nanoshima Scissors Asahi Asbestos Industry Co., Ltd. Agent: Patent attorney: Shibu Mitsuishi (1 other person)

Claims (1)

[Claims] It has a composition of 95 to 65% by weight of cement, 5 to 35% by weight of fiber material, and the above cements include blast furnace slag and Portland cement 100 to 70% by weight, and inorganic admixtures O to 3.
An aqueous slurry having a composition of 0 slag and a ratio of blast furnace slag to portland cement of 3.0 to 9.0 is extracted, and the plate is weighed at 50 kg/cr.
A method for producing a fiber cement board containing less free lime, which comprises dehydrating and forming under one or more pressures and then curing and hardening.