JPH0159083B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a method for manufacturing a carbon fiber reinforced cement board, and more particularly to a method for producing a product with high strength, simple equipment, and high productivity. [Prior art] Asbestos fiber-reinforced cement boards are widely used as interior and exterior materials, but since asbestos is said to be a carcinogen, efforts have been made to remove asbestos, and alkali-resistant glass fibers have been tried. However, it has been impossible to ensure long-term strength due to insufficient alkali resistance, so reinforcement with carbon fibers, which have excellent alkali resistance, is desired. As methods for manufacturing carbon fiber reinforced cement boards, premix methods, spray methods, paper forming methods, and extrusion methods have been tried, but each method has the following problems. The premix method is a method in which carbon fiber is mixed with cement paste or cement mortar and then molded using a mold, but it is impossible to uniformly mix carbon fiber that can develop the required strength. It was hot. The spray method is a method in which carbon fibers are cut with a cutter and simultaneously sprayed with cement paste or cement mortar.The spray suction method is a method in which water is suctioned and removed from the back side of the sprayed surface in the spray method. Although it is possible to manufacture products in which the fibers are uniformly oriented in two dimensions, it not only requires special and complicated equipment, but also makes it difficult to improve productivity. In the cylinder papermaking method, the holding power of cement particles by carbon fibers during papermaking is small, so it is impossible to form a base material using carbon fibers and cement. The extrusion molding method uses a screw-type extruder as an extruder, and has higher productivity than the cylinder papermaking method, which is the main manufacturing method for manufacturing asbestos fiber reinforced cement boards, and does not generate wastewater. This is an excellent method, but since the uncured molded body extruded from the nozzle is cured as it is and made into a product, the uncured molded body needs to be dense, so the extruder has a small opening area. Since the extruded substrate is compacted with a ratio of 0.2 to 0.4 to the area of the extrusion opening (opening ratio), the substrate in the extruder and die is subjected to strong shearing force due to high extrusion pressure, and carbon fiber is used instead of asbestos. Even if carbon fibers are used, they will be cut and will hardly contribute to the development of strength.When manufacturing a flat plate with a large change in cross-sectional shape from the base material extruded in a cylindrical shape from an extruder, cutting the carbon fibers is necessary. This is particularly noticeable. [Problems to be Solved by the Invention] The present invention solves the above-mentioned problems and provides a manufacturing method in which a product has high bending strength and impact strength, a simple device, and high productivity. [Means for Solving the Problems] In order to solve the above-mentioned problems, the present invention aims to solve the above-mentioned problems.
A base material made by kneading raw materials containing ~0.5% by weight of a retarder with water is extruded into a cylindrical shape using a screw extruder at an aperture ratio of 0.4 to 0.8, and the cylinder is cut in a direction perpendicular to the extrusion direction. Then, the upper part of the cut body is cut in the extrusion direction, developed into a flat plate, and the flat plate is rolled and then cured. [Function] The main purpose of the present invention is to reduce the shearing force of the substrate in the extruder and die to prevent cutting of the carbon fibers. Portland cement, blast furnace cement, silica cement, fly ash cement, etc. are selected as cement depending on the quality required for the product, the allowable manufacturing period, the type of curing, etc. Silica sand powder is used when curing in an autoclave, etc. are mixed. As carbon fibers, PAN or pitch type carbon fibers having a diameter of 12 to 15 μm and a length of 5 to 10 mm are used, and the amount used is 0.5 to 5% by weight based on the raw material. The base material generates heat due to friction with the extruder screw, screw casing, and die, and this heat generation promotes hydration of the cement. This is further accelerated and the substrate begins to set, progressively decreasing its plasticity and increasing shearing force. Therefore, setting retarders such as calcium lignin sulfonate and silicofluoride are used in an amount of 0.2 to 0.5% by weight of the cement. do. If it is less than 0.2% by weight, the effect is insufficient, and if it is used in excess of 0.5% by weight, the effect will not be improved. If dehydration occurs in the base material inside the extruder and the die during molding, extrusion cannot be performed stably, so in order to prevent this and at the same time reduce the shearing force of the base material to extrude the base material without distortion. It is preferable to mix thickeners such as , water-soluble cellulose, ethers, ethylene oxide polymers, acrylamide polymers, polyvinyl alcohol, etc. into the base material, and the amount to be mixed should be determined by considering other compositions of the base material, etc. It is determined by trial to develop the required optimal plasticity. Since the extrusion port of a screw type extruder is circular, it is desirable to extrude the base material in a cylindrical shape in order to extrude the base material with as low a shearing force as possible.
In order to cut the extruded uncured molded product in the extrusion direction and develop it into a flat plate, it is necessary to extrude it into a cylindrical shape. The outer and inner diameters of the cylinder are determined by the size of the extruder opening,
It is determined by taking into account the size of the product, degree of rolling, etc. If the aperture ratio of the cap is increased, the shearing force of the substrate will be reduced and cutting of the carbon fiber can be prevented, but
The solidity of the cylindrical uncured molded body may become insufficient, making it impossible to perform cutting, rolling, and rolling operations, or even if these operations are possible, the physical properties of the resulting product may be insufficient. Therefore, it should be 0.8 or less, and 0.4
If it is less than that, the cutting of carbon fiber will be noticeable.
The aperture ratio shall be 0.4 to 0.8. The extruded cylinder is cut in a direction perpendicular to the extrusion direction, taking into account the size of the product and the degree of rolling, and then the upper part of the cut body is cut in the extrusion direction and expanded to form a flat plate. Can be done. Since the cut body is uncured, it can be easily cut using a rotary saw, for example. The flat plate is rolled to the required thickness and/or density. Rolling can be carried out by a roll press or a full surface press, but rolling is easier and the method of using a roll press to gradually reduce the gap between opposing rolls and passing a flat plate between them is easier and does not damage the composition of the rolled material. preferable. The pressing force and the number of rolls of the roll press or the full surface press are determined as appropriate based on the stiffness of the flat plate, the degree of processing, etc. After rolling, it is cured by natural curing, steam curing or autoclave curing, and if necessary, it is cut into products. [Example] 55.32 parts by weight of ordinary Portland cement, 40 parts by weight of coarse sand, 4 parts by weight of pitch carbon fibers with a diameter of 10 μm and a length of 8 mm, calcium lignin sulfonate
A base material made by kneading raw materials consisting of 0.18 parts by weight and 0.5 parts by weight of methyl cellulose with 25 parts by weight of water was extruded into a cylindrical shape with an external diameter of 220 mm and an internal diameter of 100 mm by connecting a nozzle to a screw type extruder with an internal diameter of 250 mm. The cylinder was cut perpendicularly to the extrusion direction using a rotary saw to obtain a cut body having a length of 500 mm, and the upper part of this cut body was cut using a rotary saw to form a flat plate. The flat plate was rolled to a thickness of 12 mm using a roll press, and the plate was cured in an autoclave for 5 hours at a gauge pressure of 10 atg to obtain a product. The physical properties of the product are shown in the table. [Comparative Example] The same procedure was used as in Example except that 0.12 parts by weight of calcium lignin sulfonate, 0.5 parts by weight of methyl cellulose, and a flat plate mouth with an opening height of 12 mm and width of 330 mm were used, and the physical properties of the product were shown. It was shown to.

〔Effect of the invention〕

By the method of the present invention, a carbon fiber-reinforced cement board with high strength and toughness could be manufactured with high productivity using a simple device. Further, since the carbon fibers in the product are mainly oriented in a direction perpendicular to the extrusion direction, the strength in this orientation direction is higher than that of a two-dimensionally oriented product with the same amount of carbon fibers.

Claims (1)

[Claims] 1 A base material obtained by kneading a raw material containing at least cement, carbon fiber, and a retarder of 0.2 to 0.5% by weight relative to the cement with water is extruded into a cylindrical shape with a screw extrusion molding machine at an aperture ratio of 0.4 to 0.8, Cutting the cylinder in a direction perpendicular to the extrusion direction, cutting the upper part of the cut body in the extrusion direction and developing it into a flat plate,
A method for manufacturing a carbon fiber reinforced cement board, which comprises curing the flat board after rolling it.