JPS6033244A - Manufacture of inorganic fiber formed body - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing an inorganic fiber molded article,
More specifically, the present invention relates to a method for producing an inorganic fiber molded article with a good yield of colloidal silica.

In general, inorganic fiber molded products obtained by using colloidal silica aqueous solution as a binder for inorganic fibers have excellent heat resistance, heat insulation properties, and thermal shock resistance, so they are widely used as heat-insulating materials for high temperatures. ).

Conventionally, such inorganic fiber molded articles are produced by placing inorganic fibers in an aqueous solution of colloidal silica dispersed in water, defibrating and dispersing them, forming a slurry or paste into a predetermined shape, and then drying. It is manufactured by a hardening method. However, in such conventional methods, a phenomenon known as migration occurs, where the colloidal silica component moves from the half-dried molded product during drying and collects only in the surface layer. After drying, only the surface layer hardens, while the inner layer remains soft. Only formations such as Naru can be obtained.

Therefore, the above-mentioned conventional method leaves many problems in the processability of the molded product and its handling during processing.

Therefore, in order to solve the above-mentioned problem, various studies have been made to prevent migration of colloidal silica as a binder.

For example, in the invention described in Japanese Patent Publication No. 37-8590, gentle hot air drying is performed at a low temperature of 43 to 49°C.
This method requires a long time for drying and is unfavorable in terms of process.

Moreover, in the invention described in JP-A-53-27618,
A molded body is made by adding calcium silicate or magnesium silicate as a hardening agent for colloidal silica, and the colloidal silica and hardening agent are reacted during firing to suppress migration of colloidal silica.
It has the disadvantage that the yield of colloidal silica is poor and stability is insufficient when reusing the slurry liquid. Furthermore, in the invention described in JP-A-58-104059,
Aluminum sulfate is added as a hardening agent for colloidal silica, and then high molecular weight polyethylene oxide is added to fix colloidal silica to inorganic fibers to suppress migration, but this method has a poor yield of colloidal silica. In addition, it has many drawbacks such as poor filterability of the slurry liquid.

The present invention improves the drawbacks of the prior art described above, and relates to a method for uniformly and firmly bonding colloidal silica to inorganic fibers, improving the yield of colloidal silica, and obtaining an inorganic molded body suitable for high-temperature applications. It is.

That is, the present invention adds a coagulant to a slurry liquid formed by dispersing inorganic fibers and colloidal silica in a dispersion medium, and promptly adjusts the pi of the slurry liquid to 4°5 or less to produce a colloidal silica coagulate, Next, preferably, after adjusting the pH of the slurry liquid to 4.5 to 8.5, a polymer flocculant is added to the slurry liquid to fix the colloidal silica coagulant to the inorganic fibers. This provides a method for producing an inorganic fiber molded article, which is characterized by molding and processing a slurry liquid, and the product can be made undried, or it can be dried or fired to remove flammable substances. It also includes a method for obtaining a molded body.

Furthermore, the present invention also includes a method for producing a molded article, in which a required amount of filler such as sand, clay, mineral powder, etc. is added to the slurry liquid as necessary, and the slurry liquid is molded and processed. It is.

According to the method of the present invention, the slurry liquid for inorganic fiber molded bodies has good filterability during molding and processing, the yield of colloidal silica is significantly improved, and migration does not occur during drying of the obtained molded bodies. A molded article with high strength and high hardness can be obtained.

The present invention will be explained in detail below.

Inorganic fibers used in the present invention include ceramic fibers, alumina fibers, zirconia fibers, quartz wool, rock wool, flag wool, glass wool, asbestos, titanate fibers, boron carbide fibers, silicon carbide fibers, and silicon nitride fibers. , various whiskers, etc., and can be selected from the group consisting of each of these fibers and mixtures thereof, but ceramic fibers are most suitable in terms of fiber heat resistance and economical efficiency.

Furthermore, colloidal silica (commonly known as silica sol) used in the present invention is an aqueous colloidal dispersion solution of 5i02 (silica), which can be processed by various methods such as neutralization of sodium silicate, ion exchange treatment of sodium silicate, etc. Products that can be obtained include Snowtex (Nissan Chemical Products), Applied (Asahi Denka Products), and Ludox (Dupont Products), and the colloid size is usually 5 to 100.
mμ, 5i02 (silica) having an S degree of 20 to 50% by weight is used.

Water is suitable as the dispersion medium necessary to make a slurry of #B-free fibers, colloidal silica, and fillers added as necessary, but methanol, ethanol, ethylene glycol, diethylene glycol, propylene glycol, glycerin, and mixtures thereof, alone,
Alternatively, it can be used as a mixture with water. The amount of dispersion medium is adjusted depending on the amount of inorganic fibers used and the amount of colloidal silica, but it is necessary to have a small amount (in which the fibers are sufficiently dispersed, for example, the weight of the dispersion medium and inorganic fibers). The ratio is too:o, i~10:1, more preferably 1
00:1 to 100:4.

In the present invention, the quantitative relationship between the colloidal silica used as a binder and the TA-free fiber is preferably such that the solid content of 5i02 in the colloidal silica is preferably 100:1 to ioo:3o, more preferably 100:1 to inorganic fiber. :
3 to 100,720; if it is less than this, the strength of the intended molded product tends to decrease, and if it is too much, it tends to be difficult in terms of filterability.

Coagulants used in the present invention include acids (e.g., hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, organic acids), salts (e.g., chlorides, sulfates, nitrates), alumina sol, and sodium aluminate. Particularly preferred are acids, aluminum sulfate, aluminum chloride, polyaluminum chloride, and alumina sol. The function of the coagulant here is to adhere to the surface of colloidal silica and coagulate colloidal silica particles, and in order to complete the coagulation more quickly, the slurry liquid is adjusted to pH 4,
It is necessary to make the coagulant work under conditions of 5 or less. This is because if the pH exceeds 4.5, the coagulating effect of the coagulant will not be fully demonstrated.For example, if an acidic salt such as aluminum chloride is used as a coagulant, most of the aluminum chloride will turn into aluminum hydroxide and will not be used as a coagulant. This is because it eliminates the function of The method for making the slurry liquid p) 14.5 or less is as follows:
Although it is appropriate to use a mineral acid, if the alkalinity of the slurry is low, an acid salt can be used instead as a coagulant. In any case, the reaction conditions for the colloidal silica and the coagulant are such that the slurry liquid has a pi of 4.5 or less, more preferably a pH of 3 to 4.5.

The mixing ratio of colloidal silica and coagulant is preferably 100:0.5 to 10:2 in terms of solid content weight ratio.The reaction time is
Stirring for about 1 to 10 minutes at room temperature is sufficient.

Next, a polymer flocculant is added, and at this time, it is preferable to return the pH of the slurry liquid to pH 4.5 to 8.5. This makes the colloidal silica coagulate produced by the reaction between colloidal silica and coagulant more stable, improves filterability, and further improves the yield of colloidal silica. in this case,
If pn is 8.5 or more, re-dissociation of colloidal silica condensation occurs, which is not preferable. The pH of the slurry liquid is 4.5.
Metal hydroxides and alkaline salts are suitable as the chemical solution for returning the temperature to 4°5 to 8.5°, but for example, caustic soda, soda carbonate, alkali silicate salts, and sodium aluminate are more preferable.

The important point in the present invention is to produce a floc of inorganic fibers on which colloidal silica aggregates are fixed using a polymer flocculant. By using this polymer flocculant, the colloidal silica coagulates firmly adhere to the inorganic fibers, resulting in a slurry liquid with good filterability and a good yield of colloidal silica. The polymer flocculant referred to here is a polymer flocculant generally used in the water treatment field, and due to differences in raw materials and manufacturing methods, it may differ from natural polymers and their derivatives.
It can be divided into synthetic polymers. Natural polymers and their derivatives include starch and its derivatives, cellulose and its derivatives, sodium alginate, protein, konjac, agar, pectic acid, chitosan, etc. Synthetic polymers include polymerized Polymerization types include, for example, modified products of polyacrylic acid, polyacrylamide, maleic acid condensates, and their copolymers, and generally nonionic, anionic, and cationic types are manufactured. The condensed type is, for example, a polycation.

Among these, synthetic polymer flocculants having a molecular weight of 100,000 or more are more preferred. Commercial products of this polymer flocculant include, for example, Flonac (Kyowa Yushi Products), Diafloc (Diafloc Products), Sumifloc (Sumitomo Chemical Products), Azocafloncar (Jiryuka Products), and the like. These polymer flocculants are mixed and stirred with the above-mentioned solvent in advance and used as a solution at the required concentration. The amount used varies depending on each flocculant, but it is approximately 0.1
Preferably, 0.02 to 1.0% by weight is added in the form of a solution to the slurry liquid as a solution of 0.5% to 0.5% by weight. 0.0
If it is less than 2% by weight, its effect will not be exhibited very much,
Moreover, if the amount is 1.0% by weight or more, there is a risk that the generated flocs will be redispersed.

The form of the molded article produced according to the present invention may be vapor, board, cloak, tube, rod, block, etc.

For example, in the case of manufacturing paper or boards, the specific molding method is to use a slurry liquid (composition slurry) in which colloidal silica aggregates are fixed to inorganic fibers.
It is dried on a wire mesh, and the water is removed by a compression roller, or the water is removed by suction dehydration, and then the product is shaped. For other molded bodies, the composition slurry can be filtered into a cake and molded into a suitable mold. On the other hand, the filtered filtrate is almost completely transparent, contains almost no active ingredients such as colloidal silica, coagulants, polymer flocculants, and other inorganic fibers, and only contains a small amount of inorganic salts, making it an ideal resource for recycling. Alternatively, direct discharge into rivers is possible.

In addition, in order to increase the density of the inorganic fiber molded article of the present invention, to further increase heat resistance and heat retention, and to improve processing,
In addition, for the purpose of increasing the amount, sand or similar products (for example, silica sand, zircon sand, alumina sand, molten glass sand, etc.) and clay minerals (for example, kaolin, bentonite, talc, mica, etc.) are used in the present invention. Even if it is added to the slurry liquid and dried in molding, it is possible to obtain a high-strength, high-hardness inorganic fiber molded product that prevents migration, which is the objective of the present invention, and at the same time, a good yield of colloidal silica and a clean filtrate can be obtained. .

Hereinafter, the present invention will be described in detail based on Examples, but the present invention is not limited to these Examples.

Example 1 Colloidal silica (5i0230%,
15 g of Na200.3%, particle size 10~jOmμ) and 20 g of ceramic fiber (Japan Asbestos ■; Fine Ceramic Fiber 1300) were added, and a homogeneous slurry liquid was prepared using a mixer.

The pH of this slurry liquid was 10.3. Next, 3 g of a 20% aluminum sulfate aqueous solution was added thereto, and the pH of the slurry liquid was adjusted to 3.8. After stirring this for 5 minutes, 10% NaOH aqueous solution was added to reduce the pH of the slurry liquid.
H was set to 6.3. To this slurry liquid, 1 g of a 0.1% aqueous solution of Azocaflocker (Jiryuka, 20A-80, anionic) was added to prepare a final slurry liquid. This final slurry liquid was subjected to suction dehydration molding in a metal mold provided with a wire mesh to obtain a molded product. This molded body was dried at 110 to 140°C for 6 hours, and the diameter was On+s+ and the height was 4 as shown in Figure 1(a).
A cylindrical inorganic fiber molded body 1 of 0++++w was obtained.

This inorganic fiber molded article 1 was cut as shown in Fig. 1) to obtain a test piece 1'. Each measurement point H on test piece 1゛,
M (H is the center point of the top surface, M is the center point of all cross sections, the first
In the figure), the strength during compression was measured using an autograph (manufactured by Shimadzu Corporation, model 15-2000). The measurement results are shown in Table 1 and Figure 2.

In addition, for the above measurements, a compressed metal rod with a diameter of 5+
A nm steel rod was used and the steel rod was lowered at a lowering speed of 1 mm/min and the recording paper was moved at a speed of 20+wm/min. Furthermore, Table 1 shows that the compressed metal rod was 0.
．． 2 ml11<The compressive strength when immersed is defined as hardness, and 0.5 m++<The compressive strength when immersed is defined as strength, and each is expressed in units of Kg/cd. Further, FIG. 2 shows a graph showing the relationship between the compressive strength at measurement point M and the amount of penetration of the compressed metal rod into the test piece.

In addition, the rate of decline of the final slurry liquid and the properties of the filtrate were measured. The results are shown in Table-2.

Example 2 20 g of colloidal silica, 3 g of 20% aluminum chloride as an activator, and 0.1% aqueous solution 1 of Azocafloncar 1ON-40 (anion) as a polymer flocculant.
An inorganic fiber molded article was obtained in the same manner as in Example 1, except that g was used, and the same measurements as in Example 1 were performed on this inorganic fiber molded article.

The results are shown in Table 1 and Table 2.

Example 3 An inorganic fiber molded article was obtained in the same manner as in Example 1 except that 1 g of a 0.1% aqueous solution of Azocafloncar 30G-60 (cation) was used as the polymer flocculant. Example 4 The amount of coagulant added was 2 g. , Azocaf i as a polymer flocculant
ff, Carr 10N-40 (/Nio 7) (7) 0.1%
An inorganic fiber molded article was obtained in the same manner as in Example 1 except that an aqueous solution was used, and the same measurements as in Example 1 were performed on this inorganic fiber molded article. The results are shown in Table-1 and Table-2.

Example 5 Polyaluminum chloride aqueous solution (resident aluminum products,
An inorganic fiber molded body was obtained in the same manner as in Example 1 except that 4 g of PAC, Al103 10% product) was used, and the same measurements as in Example 1 were performed on this inorganic fiber molded body. The results are shown in Table-1 and Table-2.

Example 6 A molded article was obtained in the same manner as in Example 1, except that the pH was not adjusted. The results are shown in Table-1 and Table-2.

Comparative Example 1.2.3 In Example 1, Comparative Example 1 is a case in which no coagulant is added, the pH is adjusted to 111, and a polymer flocculant is not added. Comparative Example 2 was defined as Comparative Example 2, and Comparative Example 3 was defined as the case where no polymer flocculant was added. Inorganic fiber molded bodies were obtained in the same manner as in Example 1,
The same measurements as in Example 1 were performed for each of these inorganic fiber molded bodies.

The results are shown in Table-11 and Table-2.

Table-1 As is clear from the results shown in Table-1, Table-2, and Figure 2, the inorganic fiber molded product obtained by the method of the present invention has high strength and high hardness without migration. It can be seen that during its production, the yield of colloidal silica is high and its filterability is excellent, and that it is also very excellent in terms of the production process.

[Brief explanation of drawings]

FIG. 1(a) is a perspective view of an inorganic fiber molded product obtained in an example of the present invention, and FIG. 1(a) is a perspective view of a test piece formed by cutting the inorganic fiber molded product. Fig. 2 is a graph showing the relationship between the compressive strength at measurement point M and the amount of penetration of the compressed metal rod into the test specimen. Patent applicant Asahi Denka Kogyo Co., Ltd. Figure 2:1

Claims (1)

[Claims] A coagulant is added to a slurry liquid obtained by dispersing inorganic fibers and colloidal silica in a dispersion medium, and the pH of the slurry liquid is immediately adjusted to 4.5 or less to produce a colloidal silica coagulate, and then to this slurry liquid, A method for producing an inorganic fiber molded article, which comprises adding a polymer flocculant to fix the colloidal silica coagulate to inorganic fibers, and then molding and processing the slurry liquid.