JPH0411499B2 - - Google Patents

Description

[Detailed description of the invention]

``Purpose of the Invention'' [Industrial Field of Application] The present invention involves applying a glaze to the surface of a molded product obtained by extruding a mixture of raw materials mainly consisting of cement, fiber, and water, and then firing the product. The present invention relates to a method for manufacturing a glazed cement product in which a glaze layer is formed by forming a glaze layer. [Prior art] Normally, when manufacturing glazed cement products by extrusion, the main components are cement such as ordinary Portland cement, early strength cement, and blast furnace slag cement (hereinafter simply referred to as cement), fiber, and water. Aggregates and additives are added and mixed as necessary to the mixture, and the mixture is extruded and the surface of the molded body is glazed, followed by firing and hydration hardening to produce a product. In this case, the fiber is extrudable,
This is to improve shape retention, and asbestos fiber is generally used. The aggregates used include silica sand, hard sandstone, river sand, crushed ceramic tiles and sanitary ware, and the additives include plasticizers, water-reducing materials, and expansion materials. [Problems to be Solved by the Present Invention] The conventional method for manufacturing the above-mentioned glazed cement products by extrusion molding had the following drawbacks.
In other words, (1) Since the fiber used as the main component is asbestos fiber, pinholes may remain in the glaze layer of the product, which impairs the aesthetic appearance, lacks frost resistance, and significantly reduces the value of the product. It has the disadvantage of reducing the (2) Also included in asbestos fibers during firing.
When a small amount of Mg is dissolved in solid solution, α'-C <sub>2</sub> S is generated, which has the disadvantage that the development of mechanical strength during subsequent hydration hardening is delayed. The inventors investigated the cause of these shortcomings and found the following. In other words, the drawback of (1) above is that chrysotile asbestos (3MgO・2SiO <sub>2</sub>・2H <sub>2</sub> O) used as asbestos fiber does not
At around 600℃, it gradually starts dehydrating and begins to disintegrate. However, commonly used glazes begin to soften at around 600°C and melt at around 700-900°C. Since the softening temperature of this glaze and the dehydration temperature of the asbestos fibers are almost the same, the water that evaporates on the surface of the object to be fired (extruded object) due to dehydration softens and becomes a continuous layer with high viscosity. It becomes encapsulated within the glaze layer of the state. Moreover, even if the glaze is completely melted during subsequent high-temperature firing, its viscosity does not decrease like water, and the water that is once encapsulated in the softened glaze layer remains without being removed.
As a result, pinholes were generated, the aesthetic appearance was impaired, and the frost damage resistance was also poor. Furthermore, the above drawback (2) is based on the inherent properties of glazed cement products. Generally, in the case of this type of glazed cement product, when the cement extrusion molded body is glazed and fired, the cement hydrate is dehydrated and C <sub>2</sub> S and CS are generated. For this reason, the fired body has the property that although its mechanical strength once decreases, the strength is recovered by subsequent hydration hardening. However, C <sub>2</sub> S and CS have the property that strength development is slow and strength recovery takes time. This tendency differs depending on the various transformations of C <sub>2</sub> S, and in particular, α'-C <sub>2</sub> S, which is produced by a small amount of solid solution of Mg in asbestos fibers during the firing process, has a remarkable tendency. It was hot. This drawback is that when manufacturing glazed cement products by extrusion, asbestos fibers are mixed with other cements,
This was unavoidable since it is the main component along with water. In addition, recently, substances precipitated from various chemical products have become a public pollution problem. Even in the case of extrusion-molded glazed cement products using asbestos fibers, asbestos fibers have been problematic as carcinogenic substances and substances that cause silicosis, etc., and their use has not been desirable. Conventionally, when producing glazed cement products by suction molding, asbestos fibers have been used in the same way as in extrusion molding, which has the above-mentioned drawbacks. ``Structure of the Invention'' [Means for Solving the Problems] The present invention solves the above-mentioned drawbacks of the conventional technology by extrusion molding a mixture of raw materials mainly composed of cement, fiber, and water. When producing a glazed cement product with excellent mechanical strength by applying a glaze to the surface of the obtained molded body, firing it at high temperature, and then hydration hardening, the fibers are vinylon fibers. , organic fibers such as acrylic fibers, carbon fibers, pulp fibers, etc., whose burnout temperature is 500℃ lower than the melting temperature of normal glazes.
The fibers are burned out by heating the molded body once to a fiber burning temperature or heating to the fiber burning temperature during glaze firing, and then fired at a temperature of 650 to 900°C, It is an object of the present invention to provide a method for manufacturing a glazed cement product in which the fired body is hydrated and hardened. This results in
There are no pinholes in the glaze layer, making it possible to create a product with excellent aesthetics and frost damage resistance, as well as excellent early development of mechanical strength. As mentioned above, the method of the present invention can be applied to cement, fiber,
The main component is water. Therefore, the cement includes commonly used cements such as ordinary Portland cement, alumina cement, blast furnace slag cement, mixed cement, and early strength cement (hereinafter referred to as
(simply referred to as cement). In addition, fibers include organic fibers such as vinylon fibers and acrylic fibers, carbon fibers, pulp fibers, etc.
Any material that can be burnt out at a temperature of ℃ or lower is acceptable. Materials used in addition to the above-mentioned main components include thickeners, aggregates, and additives such as water reducing agents, hardening accelerators, hardening retarders, and colorants. As the thickener, methylcellulose, ethylcellulose, carboxymethylcellulose, polyethylene oxide, polyvinyl alcohol, etc. are used. Particularly preferred is methylcellulose. Furthermore, as the aggregate, those commonly used as aggregates for cement, such as sand, sieruben, and siyamoto, are sufficient.
Additives such as water reducing agents, curing accelerators, curing retarders, and coloring agents are used as necessary. In the method of the present invention, the above-mentioned materials are placed in a conventional mixer and mixed. Then, if necessary, the mixture is kneaded using a predetermined kneader. next,
The kneaded or unkneaded mixture is extruded into a predetermined shape using an extrusion molding machine. After that, the extruded product is immersed in air or water for several hours.
Perform preliminary hydration curing for several days. After preliminary hydration and hardening, a desired surface of the extruded molded product is glazed with a conventional glaze raw material containing glass powder or frit as a main component by spraying, curtaining, dipping, or the like. Next, the glazed extrusion molded body is heated to a fiber burning-off temperature to burn out the aforementioned fibers contained in the molded body. This heating may be performed separately from the later firing, or may be performed simultaneously. The heating at this fiber burning-off temperature is below the melting temperature of the glaze, and when the fibers are burned off, water does not dissolve into the glaze. In other words, it does not cause pinholes. After that, the extruded body is fired at a temperature of 650 to 900°C. In the present invention, since asbestos fibers are not used unlike in the past, α'-C ₂ S is not produced during firing. Therefore, the strength development during the full-scale hydration hardening performed later is not delayed by α'-C ₂ S, and the strength can be recovered quickly. After firing, the fired body is cooled and full-scale hydration hardening is performed by curing such as immersion in water, steam curing, and autoclave curing. Incidentally, the portion where the fibers are burned away becomes a bore, but this is not a problem because the cement hydrate during the full-scale hydration hardening that is performed thereafter fills this bore. However, if the diameter of the fibers is large, even cement hydrate may not be able to fill the above-mentioned bores, so the diameter of the fibers used is
It is desirable that the thickness is 100 μm or less. After full-scale hydration hardening is completed, it can be taken out and dried. As a result, it is possible to obtain a glazed cement product that does not have pinholes in the glaze layer and has excellent early development of strength. In order to further improve the mechanical strength, metal fibers such as steel fibers and stainless fibers, and heat-resistant fibers such as ceramic fibers may be added at the time of mixing the raw materials. This heat-resistant fiber does not melt or soften even at the firing temperature of the glaze, and does not cause pinholes or the like. Furthermore, a metal reinforcing material such as a metal wire, a material framed by metal wires, or a metal mesh may be buried during extrusion molding. If this metal reinforcing material and the above-mentioned heat-resistant fiber are used together, extremely excellent mechanical strength can be obtained. Next, specific examples will be described in which a glazed cement product manufactured by the method of the present invention is compared with a glazed cement product manufactured by a conventional method. [Example] Comparative products were manufactured using both the present invention and the conventional method.
The raw materials shown in Table 1 were mixed using a mixer OM-30 manufactured by Chiyoda Giken Kogyo Co., Ltd., and then
The mixture was kneaded using a kneader PAD-3 manufactured by Co., Ltd. Then, the mixture after kneading was extruded using an extrusion molding machine DE-100 manufactured by Honda Iron Works Co., Ltd. at a molding pressure of 100 Kgf/cm ² , and the extruded product was cured in air for 1 day to prepare a preliminary Hydration curing was performed. Thereafter, a conventional glaze containing frit as a main component was applied by spraying, and the material was fired at a firing temperature of 900°C for a holding time of 30 minutes. Then, the fired body was cured by steam curing for 3 days to perform full-scale hydration hardening. The size of the test piece after full-scale hydration hardening is 100 mm x 150 mm x 10 mm.

[Table] Table 2 shows the results of comparison between the product of the present invention manufactured in the manner described above and the conventional product.

【table】

[Table] As is clear from Table 2, the products of the present invention do not generate pinholes and are excellent in strength. In addition, α′-C ₂ S, which causes a delay in strength recovery during full-scale hydration hardening after firing, is not generated. Therefore, as shown in the drawings, the product of the present invention is excellent in terms of early development of strength. The technique of the present invention can also be applied to the production of glazed cement products using the suction molding method, and in this case as well, it is possible to obtain the same effects as in the case of extrusion molding described above. [Effects of the Invention] As explained above, according to the present invention, it is possible to obtain a product with no pinholes on the glazed surface and with excellent aesthetic appearance and frost damage resistance. Furthermore, since α'-C ₂ S is not generated during firing, early strength recovery can be achieved during full-scale hydration hardening after firing. As a result, since the present invention does not use asbestos fibers at all, pollution problems such as carcinogenicity and silicosis, which asbestos itself has, do not occur.

[Brief explanation of drawings]

The drawing shows the strength recovery status of the product of the present invention and the conventional product.

Claims (1)

[Claims] 1 A mixture of raw materials mainly composed of cement, fiber, and water is extruded and molded, and the surface of the resulting molded product is coated with glaze, fired at high temperature, and then cured by hydration, resulting in a product with excellent mechanical strength. In the case of manufacturing glazed cement products, the fibers are organic fibers such as vinylon fibers and acrylic fibers, carbon fibers, pulp fibers, etc., and the burnout temperature is 500 ° C., which is lower than the melting temperature of ordinary glazes. The following is
The fibers are burned out by heating the molded body once to the fiber burning temperature, or by heating to the fiber burning temperature during glaze firing, and then
A method for producing a glazed cement product, which comprises firing at a temperature of 900°C and hydrating and hardening the fired product.