JPH0725580B2 - Extruded asbestos-free cement board - Google Patents

Description

TECHNICAL FIELD The present invention relates to an asbestos-free cement composition for extrusion molding used as a building civil engineering material.

[Prior Art] Generally, ceramic products mainly composed of cement are widely used as building civil engineering materials. Among them, the extrusion-molded cement board is highly evaluated as a high-performance outer wall material having a dense structure and freezing damage resistance.

Heretofore, for example, as seen in JP-A-55-124605, a large amount of asbestos is generally mixed in a cement composition for extrusion molding. The reason is that asbestos itself has excellent strength characteristics, fire resistance, and alkali resistance,
Especially in extrusion molding, due to the excellent water retention of asbestos,
Even when the water content is relatively high, the cement composition does not become too soft, smooth extrusion is possible, and the molded body does not lose its shape after extrusion, that is, asbestos has good extrusion moldability and shape retention in the cement composition. Is given. In addition, asbestos is inexpensive, and up to about 20% of asbestos based on solid content has been conventionally compounded.

However, with regard to the use of this asbestos, carcinogenicity due to dust has become a major social problem in recent years, and there has been a strong demand for asbestos-free construction materials.

In order to respond to this, various asbestos-free technologies for extruded cement have been studied, but up to now, in addition to asbestos, it has such an extrudability-improving effect as well as strength characteristics, fire resistance, and alkali resistance. No cheap alternative material with good performance has been found.

For example, JP-A-60-137859 discloses a technique of using chlorite instead of asbestos. Chlorite is fine flaky particles having a diameter of 20 μm or less, has good water retention and is clay-like, and therefore the effect of improving the shape retention by this is attempted to be utilized. However, the size of 20 μm or less is equal to or smaller than the cement powder as the base material. This means that if it is thoroughly mixed with the cement powder and completely dispersed in the cement powder, it loses its chlorite properties. Therefore, only when the mixing is insufficient, chlorite particles are unevenly distributed and retain their properties, and water retention and shape retention are exhibited, but for this reason, the uneven distribution of chlorite particles is weakly bonded, In building materials, it becomes the starting point of cracking and sufficient strength cannot be exhibited. Furthermore, with such a fine size, it is impossible in principle to substitute the function of cement building material composite reinforcement originally possessed by asbestos.

[Problems to be Solved by the Invention] As described above, conventionally, depending on materials other than asbestos, the cement composition can be extruded by providing good extrusion moldability and shape retention, and can be cured. It was impossible to obtain a cement building material with excellent strength and fire resistance, and we had no choice but to use asbestos, which is harmful to the human body.

The object of the invention is to make this possible, depending on materials other than asbestos.

[Means for Solving the Problem] Since there is no single material having the excellent performance of asbestos, the inventors tried to substitute the performance with a plurality of materials.

That is, in selecting an asbestos substitute material, in addition to high strength, fire resistance, alkali resistance, various properties such as water retention and shape retention during extrusion molding, lubricity, or various inorganic materials having a plurality of properties, The trial production of organic materials and their combinations was repeated.

As a result, finally, based on the solid content of the blended materials, the pulp was
It was found that a cement composition containing 0.5 to 3% by weight and mica flakes in an amount of 3 to 10% by weight is suitable for producing an asbestos-free cement board having necessary and sufficient performance as a building material.

[Operation] In the cement composition for extrusion molding according to the present invention, the pulp is 0.5 to 3% by weight and the mica is 3 to 1 based on the solid content of the compounding raw material.
It is 0% by weight and contains no asbestos at all.

Here, pulp substitutes the water retention and shape retention properties of asbestos, and the mica flakes substitute the high strength, fire resistance, alkali resistance and lubricity of asbestos.

It is important that the pulp has excellent water retention. Pulp is as fibrous as asbestos, and its water-retaining performance is far superior to that of asbestos. In general, the cement composition for extrusion molding tends to obtain a more homogeneous mixed state as the water content increases, but this simultaneously lowers the frictional resistance in the extruder required for extrusion and makes it easier to lose the shape after extrusion. Pulp improves the extrudability of a cement composition due to its excellent water retention, and also imparts shape retention to the product after extrusion.
As a result, the pulp exhibits an extrusion moldability-improving effect comparable to that of asbestos even with a smaller amount than that of asbestos. This is of critical importance in extrusion cement compositions.
When pulp is not used, lowering the water content improves apparent extrusion moldability and shape retention, but in that case it is difficult to achieve a homogeneous mixed state at the mixing stage before that. As a result, it is not possible to obtain excellent product building materials.

In this respect, there is no other economical alternative to pulp for asbestos.

Regarding the type of pulp to be used, any of waste paper pulp, hardwood pulp and softwood pulp can be applied. However, since waste paper pulp and hardwood pulp have a soft texture, they are suitable for uniform mixing.

Here, the blending amount of pulp is 0.5 to 3% by weight. If it is less than 0.5% by weight, the water retention capacity is insufficient, the cement composition becomes too soft, and the shape of the molded product after extrusion cannot be sufficiently maintained. Further, if it exceeds 3% by weight, it becomes difficult to uniformly disperse the pulp in the cement composition, which rather lowers the strength, and when it is used as an outer wall material, it absorbs water.
A dimensional change of expansion-contraction due to drying becomes large, which causes deterioration of airtightness of the aerial structure and deformation. Further, since pulp generates heat and carbonizes in a fire, the minimum required blending amount should be taken from the viewpoint of fire resistance.

Mica flakes replace the high strength, fire resistance, alkali resistance and lubricity of asbestos. The longitudinal elastic modulus of mica exceeds that of asbestos, and inherently has a composite strengthening performance superior to that of asbestos. In addition, since the shape is thin, it is easy to uniformly disperse in the powder, and since the specific surface area is large, a wide interface for bonding with cement can be secured.

Some carbon fibers, such as carbon fiber, are superior to mica in terms of strength (longitudinal elastic modulus), but it is difficult to obtain a uniform mixed state when they are mixed in a large amount. In that respect, mica is a material suitable for large-scale blending and uniform mixing, next to asbestos.
Mica is a natural mineral like asbestos, and has no difference in fire resistance and alkali resistance. In these respects, there is no other economical material that can replace asbestos with the exception of mica.

Here, the content of the mica flakes is 3 to 10% by weight. Mica flakes improve the strength of the product building material depending on the amount, as long as a uniform mixture with other powders is guaranteed,
If high strength of the product building material is not particularly required, less than 3% by weight of mica flakes may be included. However, it is possible to improve the strength of the extruded building material by blending the composite reinforcing material in a large amount and by uniformly mixing the composite reinforcing material by using mica flakes as the reinforcing material. Therefore, in the claims, the content of the mica flakes is limited to 3% by weight or more.

The upper limit of the mica flake composition is 10% by weight. This is because it is difficult to evenly mix mica flakes with cement when the content is 10% by weight or more.

There are no particular restrictions on the type of mica in terms of chemical composition, crystal structure, etc., and any of muscovite, phlogopite, biotite, scaly mica, soda mica, and synthetic mica are applicable. However,
Regarding the size, it is desirable that the flake diameter of mica is about 0.1 to 2 mm. Setting the flake diameter to 2 mm or less is
It is because if it is more than that, the surface of the product building material is likely to peel off like scales and the surface becomes rough.
The above is that a geometrical dimension more than that is required in view of the composite reinforcing effect.

In the production of raw materials, commercially available mica contains a small amount of 0.1 mm or less, but if it is 20% or less of the whole mica, there is no big problem.

As described above, the gist of the present invention is that the cement composition for extrusion molding, which conventionally uses asbestos, uses mica flakes and pulp in place of the asbestos, and its blending The ratio is 0.5 to 3% by weight for pulp and 3 to 10 for mica flakes, based on the solid content of the blended raw materials.
It is limited to the weight percent.

In addition, the binding cement mixture prepared by mixing cement, blast furnace slag fine powder, siliceous raw material and the like refers to all cements that have been generally used in extrusion molding. However, in the present invention, the optimum value of the molar ratio of CaO / SiO ₂ in the total components is 0.5 to 1.2.

For example, the cement used for this may be any one of Portland cement, blast furnace cement, fly ash cement, or a combination thereof, and further,
In addition to that, blast furnace slag fine powder and siliceous raw materials were added,
There can be various cases. Addition of blast furnace cement or blast furnace slag fine powder enhances the long-term strength of building materials, and addition of fly ash cement or siliceous raw material may help increase the strength of the product in the autoclave curing process. Their selection is determined according to the conventional technical judgment according to the cost of raw materials, the equipment used, the purpose of use of the product, etc.In any case, it is possible to use mica flakes and pulp instead of asbestos. is there.

Further, in the cement composition for extrusion molding, a small amount of additives other than asbestos, for example, 2% or less of an extrusion aid (such as methyl cellulose) and 3% or less of reinforcing fibers such as carbon fiber, ceramic fiber, glass fiber, etc. Inorganic fibers, organic fibers such as rayon, vinylon, nylon, polypropylene, hemp, and cotton, as well as pigments, paints, surfactants, water reducing agents, etc. may be added for specific purposes. Even in these uses, since there is no problem that the replacement of asbestos with the mica flakes and the pulp has a direct influence, it is natural that the present invention can be applied to the parts other than them. , Asbestos can be replaced with mica flakes and pulp without impairing their particular purpose. Therefore, the present invention includes an asbestos-free cement composition for extrusion molding containing the above-mentioned extrusion aid, reinforcing fiber, pigment, paint, surface active agent, water reducing agent and the like. Further, even if the cement composition for extrusion molding contains more than 3% of lightweight aggregates such as pearlite, shirasu balloon, and lightweight sand mainly composed of fly ash for weight reduction, the aggregate is The present invention can be applied to the removed portion, and asbestos can be replaced with mica flakes and pulp in the same manner. Therefore, the present invention includes extrusion-free asbestos-cement compositions containing these aggregates.

[Examples] Hereinafter, the present invention will be specifically described based on Examples.

The mixture having the blending ratio (weight ratio based on solid content) shown in Table 1 is mixed by a mixer, then kneaded by a kneading machine, and then formed into a hollow plate by a vacuum extrusion molding machine, which is then naturally mixed. After curing, 180 ° C. autoclave curing was performed for 6 hours.

Table 2 shows the results of extrusion moldability, surface properties, shape retention, and bending strength at this time.

As can be seen from the results in Table 2, the extrusion-molded cement board of the present invention exhibits good extrusion-moldability, surface properties, and shape-retaining properties, and also exhibits flexural strength values equivalent to those using asbestos.

[Effects of the Invention] As described above, the present invention enables the production of an extruded asbestos cement board from which asbestos whose use is being regulated due to carcinogenicity is completely eliminated, and contributes to the provision of a healthy living environment. It is a thing.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁶ Identification number Internal reference number FI Technical indication C04B 16:02) Z (72) Inventor Yuji Arao 12 Nakamachi, Muroran-shi, Hokkaido Nippon Steel Corporation Inside the Muroran Works (72) Inventor Kuniso Honjo 12 Nakamachi, Muroran City, Hokkaido Inside Nippon Steel Co., Ltd. Ironworks (72) Inventor Yoshiaki Ito 2-6-3 Otemachi, Chiyoda-ku, Tokyo Shin Nippon Steel Co., Ltd. (56) Reference JP-A-62-41785 (JP, A) JP-A-59-8653 ( JP, A) JP 1-122951 (JP, A) JP 54-96523 (JP, A)

Claims (3)

[Claims] 1. Extrusion molding using a cementitious cement mixture in which cement, blast furnace slag fine powder, siliceous raw material, etc. are mixed and the molar ratio of CaO / SiO ₂ in the total components is adjusted to 0.5 to 1.2 as the main binder. In the cement board, pulp is 0.5 to 3% by weight, mica flakes is 3 to 10% by weight, and the balance is the associative cement mixture, and contains no asbestos at all, based on the solid content of the compounding raw materials. Extruded asbestos-free cement board. 2. A compounding raw material comprising a cement, a blast furnace slag fine powder, a siliceous raw material, etc. mixed to adjust the molar ratio of CaO / SiO ₂ in the total components to 0.5 to 1.2 as a main binder. In an extrusion-molded cement board containing 2% by weight or less of an extrusion aid and 3% by weight or less of a reinforcing fiber based on the solid content, the portion other than the extrusion aid and the reinforcing fiber is the extrusion of claim (1). Extruded asbestos-cement board that has the same composition as the molded asbestos-cement board and that contains extrusion aids and reinforcing fibers. 3. An extruded asbestos-free asbestos according to claim 1 or 2, wherein an extruded asbestos cement board containing an aggregate for a specific purpose such as weight reduction is used. An extruded asbestos-free cement board that has the same composition as the cement board and contains aggregate.