JPH0155221B2 - - Google Patents

Description

[Detailed description of the invention]

TECHNICAL FIELD The present invention relates to a highly heat-resistant and high-strength fibrous molded article and a method for producing the same. Conventional technology Conventionally, heat-resistant fibrous molded products have been produced by adding inorganic binders, organic binders, inorganic fillers, etc. alone or in combination to inorganic fibers such as ceramic fibers and rock wool, molding them in a dry or wet method, drying, and firing. things are commonly used. Among these molded bodies, for example, those in which inorganic fibers are bonded with an organic binder do not have sufficient strength at high temperatures, and in the case of inorganic binders, the binder effect is small, so the density of the molded body must be increased considerably. Otherwise, it will be difficult to obtain strength at room temperature and high temperature. In addition, there are those that impair heat resistance, such as alkali silicates, and those that cause a significant decrease in strength at high temperatures, such as alumina cement and Portland cement.Also, even colloidal silica, alumina sol, and aluminum phosphate, etc.
It also has drawbacks such as migration that occurs during drying after molding, making it difficult to obtain uniform strength. Even if an inorganic filler is used, it has the effect of slightly improving strength and heat resistance, but it is difficult to significantly improve it, and it also has the disadvantage of increasing density. SUMMARY OF THE INVENTION An object of the present invention is to obtain a fibrous molded article that does not have the above-mentioned drawbacks, has high heat resistance, and has extremely good strength. That is, the present invention treats siliceous fibers with acid,
The surface layer is dealkalized to form a silica layer, and the fiber is dispersed in an aqueous boron oxide solution, dehydrated, and then dried and fired to form a borosilicate glass coating on the fiber surface. and has high heat resistance and fused contact points between fibers.
A high-strength fibrous molded article is provided. Preferred embodiment of the invention The silicic acid fiber that can be used in the present invention contains 40% SiO ₂
It must have heat resistance above the temperature (at least 500°C) at which the contact points of fibers are fused together by firing. Examples include ceramic fiber, rock wool, and glass fiber. These fibers are then treated with an acid, for example hydrochloric acid, sulfuric acid, nitric acid, etc. can be used for this treatment. Specifically, the treatment is performed using a 3-50% acid solution, preferably at a temperature of 10-80°C for 1-48 hours. By this acid treatment, the surface layer portion of the siliceous fiber is dealkalized and a siliceous layer is formed. However, if the thickness of the surface layer to be treated is less than 0.1μ, the effect will be weak, so the thickness of the surface layer must be 0.1μ or more. After acid treatment, the fibers with a siliceous surface layer are washed with water, optionally dried or fired, and then
Disperse in boron oxide aqueous solution. Here, boron oxide acts as a binder. That is, in the subsequent firing step, it reacts with the siliceous layer on the surface of the fibers to form borosilicate glass, which firmly fuses the contact points between the fibers. Further, boron oxide has the effect of preventing crystallization of silicic acid fibers when exposed to temperatures around 1000°C. During this boron oxide aqueous solution treatment, it is also possible to add an inorganic filler to improve heat resistance and strength. Furthermore, various additives may be added to improve dispersibility and moldability. Furthermore, it is also possible to add a binder to improve the dry strength after molding. The boron oxide aqueous solution used contains 0.5 to 10% _{B2O3 .}
The water content is reduced by dehydration molding.
Obtain a compact of 50-300%. Next, the fibers treated in this way are dried, but because the fibers have a porous silica layer on their surface, they cannot be dried by normal hot air drying.
B ₂ O ₃ adheres uniformly with almost no migration. In order to obtain a more uniform adhesion, it is advantageous to carry out high frequency drying. After drying, the molded body is preferably fired at a temperature of 500 to 1500°C for 1 to 20 hours. The molded product finally obtained in this way has a structure in which only the surface layer is converted to borosilicate vitrification while the heat-resistant fiber skeleton remains, and the contact points between the fibers are fused together. Hereinafter, the present invention will be explained in detail with reference to Examples. Example 1 100 parts of ceramic fiber was dissolved in a 10% aqueous solution of hydrochloric acid.
Pour into 3000 parts, heat to about 60℃, and stir while stirring.
After processing and washing the fibers thoroughly with water,
After heating and drying at ℃ for 10 hours, this fiber was further heated to B ₂ O ₃ 2
After uniformly dispersing the mixture in an aqueous solution containing 200%, it was dehydrated and molded to a water content of 200%, dried in a high-frequency dryer, and further baked at 1100°C for 10 hours to obtain a fibrous molded body. Examples 2-3 and Comparative Examples 1-2 Molded bodies of Examples 2-3 and Comparative Examples 1-2 were obtained by applying the raw materials and conditions shown in the following table. The physical properties of the molded bodies according to each of the above Examples and Comparative Examples are summarized in the following table.

[Table] As shown in the above table, according to the present invention, a fibrous molded product having extremely excellent strength at room temperature and high temperature can be obtained, and the fibrous molded product has a structure that is resistant to heat shrinkage at high temperatures. The remaining original fibers are small and in good condition, and the fiber surface is made of borosilicate glass, which suppresses crystallization of the fiber skeleton during high-temperature heating and prevents embrittlement of the molded product. At the same time, there is little decrease in strength after heating, and the thermal shock resistance is good.

Claims (1)

[Scope of Claims] 1. Siliceous fibers are treated with acid to dealkalize their surface layer to form a siliceous layer, and the fibers are dispersed in an aqueous boron oxide solution, dehydrated, and then dried. A highly heat-resistant, high-strength fibrous molded product in which a borosilicate glass film is formed on the fiber surface by firing, and the contact points between the fibers are fused. 2. The molded article according to claim 1, wherein the siliceous fiber contains 40% or more of SiO ₂ . 3 Claim 1 in which the siliceous fiber is silica fiber, rock wool or glass fiber
The molded article according to item 1 or 2. 4 A process of acid-treating the siliceous fibers, and dispersing the acid-treated fibers in an aqueous boron oxide solution, followed by dehydration and
A method for producing a highly heat-resistant and high-strength fibrous molded body, which comprises a molding step and a step of drying and then firing the obtained molded body. 5. The method according to claim 4, wherein the acid used is a 3-50% solution of hydrochloric acid, sulfuric acid or nitric acid. 6 The boron oxide aqueous solution used is 0.5 to 10%
The method according to claim 4, which contains B ₂ O ₃ . 7. The method according to claim 4, wherein a molded article having a moisture content of 50 to 300% is obtained by dehydration molding. 8. The method according to claim 4, wherein the drying is carried out by hot air drying or high frequency drying. 9 After drying, the molded body is heated at a temperature of 500 to 1500°C.
4. The method according to claim 4, wherein the baking is performed for 20 hours.