JPH0154305B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention provides a fire-resistant molded article containing inorganic fibers,
In particular, the present invention relates to extrusion molding of inorganic fiber molded products suitable for applications where scale resistance, wind speed resistance, etc. are important, such as backup materials for glass tank kilns, setters for ceramic firing, ladles and tundishes for steel manufacturing. [Prior Art] When manufacturing inorganic fiber molded articles, vacuum forming methods are generally widely used. In this method, short fibers obtained by chopping bulk inorganic fibers are dispersed in water together with an inorganic or organic binder to form a slurry, which is then vacuum-suctioned using a filtration mold made of fine mesh, and deposited on the surface of the mesh. The inorganic fiber layer is removed from the mold and dried to form a molded product. However, this method hardly suppresses the compressive recovery properties of inorganic fibers, so the density of the finished product is relatively light at 0.1 to 0.3 kg/, and although it has excellent heat insulation properties, it has poor strength. is insufficient. Therefore, such molded products are generally used for applications that do not require much strength, while devising a construction method. However, depending on the application, it may be difficult to supplement the strength of inorganic fiber molded products through construction methods alone. Conventional inorganic fiber molded products could not be used, and there was a desire to develop a product that combines the heat insulation and spalling resistance of inorganic fibers with the high strength of refractories. In order to produce such high-strength inorganic fibrous molded products, press molding or cast molding methods are currently being used, albeit in small quantities. However, in either method, it is necessary to reduce the moisture content as much as possible to prevent sagging and deformation after molding, and it is sometimes necessary to adjust the raw material composition to a semi-dry state. At such a high concentration, the fibers become entangled with each other and are not evenly dispersed or mixed and are molded as they are, so the resulting molded product is likely to have uneven density and unbalanced strength. Since it is a formula, it has drawbacks such as low manufacturing efficiency. Extrusion molding methods are being considered as an alternative to such press molding and cast molding methods, but inorganic fibers are not only non-plastic raw materials, but also like sponges, they easily dent when external pressure is applied. It has been thought that extrusion molding of a raw material composition containing a large amount of inorganic fibers is impossible because it has the property of restoring to almost its original state when external pressure is released. [Problems to be Solved by the Invention] The present invention aims to provide a method for continuously manufacturing high-quality molded products from inorganic fibrous raw materials by extrusion molding, which was previously considered impossible. purpose. [Means for Solving the Problems] In order to achieve the above object, the present inventor has conducted intensive research on the plasticization of inorganic fibers, and has arrived at the present invention. The production method is to add 100 parts by weight of actual fibers to inorganic fibers with an average fiber diameter of 1 to 10 μm and an average fiber length of 0.5 to 20 mm, 24 to 50 parts by weight of bentonite, and 0.6 to 3.2 parts by weight of bentonite.
It is characterized in that parts by weight of a thickener and 120 to 360 parts by weight of water are added and mixed, the mixed raw material composition is extruded, and then dried. The inorganic fibers used in the present invention include aluminosilicate fibers, which are generally called ceramic fibers, alumina fibers, mullite fibers, zirconia fibers, aluminoborosilicate fibers, silica fibers, and mineral fibers, depending on the purpose of the molded product. Two or more types can be selected as appropriate. The inorganic fibers are crushed in advance using a hammer crusher, de-sinter, etc. to give an average fiber diameter of 1 to 10 μm and an average fiber length of 0.5 to 20 mm. Bentonite is used as a plastic raw material for plasticizing inorganic fibers to make them suitable for extrusion molding. Bentonite is preferably added to the inorganic fibers as a dry fine powder to achieve uniform mixing. Other clays such as kaolin and ball clay are not effective in plasticizing inorganic fibers unless they are blended in large quantities, and therefore the resulting molded product has a high density and does not have good spalling resistance. Furthermore, binders that are commonly used to improve strength can be used in small amounts without losing the characteristics of the fibers, but colloidal silica migrates to the surface of the molded product when it dries after molding, making it especially hard. In the case of boards, it is preferable to avoid its use as it may cause surface cracks. As the deviscosity agent, sodium polyacrylate, polyvinyl alcohol, carboxymethyl cellulose, methyl cellulose, hydroxyethyl cellulose, etc. can be used, and sodium polyacrylate is preferred. The thickener is a low concentration aqueous solution of about 0.5 to 1.0%, and it is especially convenient to supply the entire amount of water to be added and blended as the thickener aqueous solution. The raw materials are mixed by dry mixing the inorganic fibers and bentonite for 1 to 60 minutes, and then adding an aqueous thickener solution and mixing for 1 to 60 minutes. As for the mixer, you can use a mullet type, ribbon type, or screw type mixer, but if you leave it for at least 24 hours after mixing is completed, then extrusion molding will not only make the molding itself easier, but also improve the quality. It is. There is no problem in drying immediately after extrusion molding, and there are no special conditions for drying. Further, a firing treatment can be performed after drying if necessary. [Function] If the average fiber diameter of inorganic fibers exceeds 10 μm, the bulk density will vary depending on the degree of kneading, and the strength and spalling resistance of the molded product will decrease.
The thickness is suitably 10 μm or less, preferably 5 μm or less.
In addition, if the average fiber length exceeds 20 mm, the dispersion of the fibers will deteriorate, resulting in variations in bulk density and deteriorating the strength and spalling resistance of the molded product.
mm or less is appropriate, and 10 μm or less is preferable. If the bentonite content is less than 24 parts by weight for an inorganic fiber with an actual fiber weight part of 100 parts by weight, the plasticity will be insufficient and extrusion molding will be difficult. Shrinkage and cracks occur, bulk density increases, spalling resistance is lost, and the heat resistance of the molded product also decreases. Instead of keeping the amount of bentonite to a relatively small amount,
Use 0.6 to 3.2 parts by weight of thickener, but if the thickener
If it exceeds 3.2 parts by weight, sagging and deformation during molding and cracking during drying are likely to occur, while if it is less than 0.6 parts by weight, extrusion molding is difficult, and even if molding is possible, the molding efficiency will be significantly reduced. Note that the weight part of real fiber means the weight part of the real fiber portion excluding non-fibrous spherical particles (shot) present in the inorganic fiber. [Example] Examples 1 to 8 Average fiber diameter 2.8 μm, composition Al ₂ O ₃ 47% - SiO ₂ 52%
- Ceramic fiber containing 1% oxide (trade name: Kao Wool, manufactured by Isolite Babkotsu Fireproofing Co., Ltd.) with an average fiber length of 4 to 10 mm using a hammer crusher, 180 parts by weight (100 parts by weight of actual fiber)
Then, 28 parts by weight of bentonite was mixed with 3 parts by weight in a Muller type mixer.
Dry mix for 1 minute, then add sodium polyacrylate.
280 parts by weight of a 0.5% aqueous solution was added and mixed for 5 minutes.
After the mixed raw material composition was left to rest for 48 hours, a board with a length of 600 mm x width of 300 mm x thickness of 20 mm was formed using a vacuum extrusion molding machine, and immediately dried to obtain a hard ceramic fiber board. The quality of this product is shown in Table 1 below, as well as ignition loss of 1.6%, and thermal conductivity.
It was 0.17Kcal/mh℃ (average temperature 600℃). Examples 2 to 8 and Comparative Examples 1 to 3 were carried out in the same manner as Example 1, except that the amounts of bentonite and sodium polyacrylate were changed, and the formulations and qualities are shown in Table 1.

[Table] Examples 9 to 11 26 parts by weight of bentonite was dry mixed with 180 parts by weight (100 parts by weight of actual fibers) of the same ceramic fiber as in Example 1 with an average fiber length of 2 to 7 mm using a de-sinter. Then, 180 parts by weight of a 0.5% aqueous solution of sodium polyacrylate was added and mixed. After the mixed raw material composition was left to rest for 48 hours, it was molded into a cylinder with an outer diameter of 40 mm x an inner diameter of 30 mm x a length of 300 mm using a vacuum forming machine, and dried to produce a hard ceramic fiber sleeve. The quality of this product is shown in Table 2 below, as well as a loss on burning of 1.6% and a compressive strength at room temperature.
The weight was 23.6Kg/cm ² and 40Kg/cm ² after firing at 1000°C for 24 hours. Examples 10 to 11 and Comparative Examples 4 to 7 were carried out in the same manner as Example 9, except that the amounts of bentonite and sodium polyacrylate were changed, and the formulations and qualities are shown in Table 2.

〔Effect of the invention〕

According to the present invention, it is possible to continuously and efficiently manufacture inorganic fibrous molded products by extrusion molding, and the obtained inorganic fibrous extrusion molded products have heat resistance,
It has both spalling resistance and high strength, and can be fully used in applications where scale resistance and wind speed resistance are important, expanding the range of applications for inorganic fiber products. be.

Claims (1)

[Scope of Claims] 1. Inorganic fibers having an average fiber diameter of 1 to 10 μm and an average fiber length of 0.5 to 20 mm, with an actual fiber weight part of 100 parts by weight, 24 to 50 parts by weight of bentonite, and an addition of 0.6 to 3.2 parts by weight. A method for producing an inorganic fibrous extruded product, which comprises adding and mixing a sticky agent and 120 to 360 parts by weight of water, extruding a mixed raw material composition, and drying the mixture. 2. The method for producing an inorganic fibrous extrusion molded product according to claim 1, wherein the thickener is sodium polyacrylate.