JPS61163173A - Method for producing heat-resistant inorganic fiber molded product - 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 a heat-resistant inorganic fiber molded article, and more particularly, to a method for efficiently mass-producing a complex-shaped inorganic fiber molded article that is homogeneous and has high dimensional accuracy. It is.

As is well known, ceramic fibers, which are attracting attention as heat-resistant inorganic fibers, are widely used in various industrial technology fields due to their excellent properties such as heat insulation, lightness, flexibility, and thermal shock resistance. There is active research into application to precise and complex structures such as automobile engine exhaust systems and gas turbine engine parts. There is a strong demand for a molding technology that can efficiently mass-produce bodies with high dimensional accuracy.

Conventionally, as a manufacturing method for ceramic fiber molded bodies, ceramic fibers and a required amount of binder are uniformly dispersed in a large amount of water to form a slurry, and a wire mesh mold for forming is submerged in a tank containing the slurry. A vacuum forming method is widely used in which fibers are completely laminated on the surface of the mold by suction filtration from the inside and then dried to obtain a molded product, but this method has many spatial constraints. It is almost impossible to mass produce molded bodies with complex shapes or irregularly shaped bodies with uneven thickness.

On the other hand, in the field of ceramic powder molding technology, as a method for mass-producing molded bodies with complex shapes with high dimensional accuracy, thermolabile resins such as polyester, polyethylene, and polypropylene are used as molding aids, and after heating and cross-wiring, Injection molding method (for example, Japanese Patent Application Laid-open No. 5
5-115510, Japanese Patent Application Laid-Open No. 55-115456), and in recent years, methods related to their improvements have been proposed.

However, in the conventional injection molding method described above, the molded product tends to suffer shape defects such as softening, deformation, sagging, and blisters during the degreasing process to decompose and remove the resin, and the degreased molded product has no strength at all. Since there is no sintering process, the essential drawback is that it cannot be moved or handled without going through the sintering process. How to degrease (
Many proposals have been made, including a method of partially degreasing using a cloth or solvent (Japanese Patent Laid-Open Nos. 55-114524 and 57-47774), but none of them are suitable for degreasing. It does not solve the essential drawbacks of the process, and there are also difficulties in implementation.As a result, even if you try to obtain a heat-resistant inorganic fiber molded product with a complicated shape using the conventional injection molding method, it is difficult to degrease it. Deformed and destroyed during the process.

The present invention provides a method for manufacturing heat-resistant inorganic fiber molded articles that improves the above-mentioned drawbacks of conventional injection molding methods, and more specifically, a method for efficiently mass-producing molded articles of complex shapes that are homogeneous and have high dimensional accuracy. In addition to the heat-resistant inorganic fibers, the composition contains a solid wax as a forming aid, a colloidal inorganic binder containing solvent water, and a dispersing aid as essential components at a temperature above the melting point of the solid wax. The gist of this method is to form a solid wax by heating and kneading it, removing it from the mold by cooling it to a temperature below the freezing point of solid wax, drying it, and dewaxing it.

The technical features of the present invention include that the dispersion of the molding composition is a plastic fluid at a temperature above the melting point of the solid wax, and a hard solid at a temperature below the freezing point of the solid wax; By preparing a uniform dispersion system in which the solvent water is easily removed (dehydrated) from the molded body (green) by drying and a strong bonding force of the inorganic binder is generated, the desired molded body can be obtained. In the method of manufacturing.

The heat-resistant inorganic fibers that are constituent materials of the molding composition in this invention include alumina, silica, aluminosilicate, calcium silicate, sulfur/ljt, asbestos, zirconia, boron oxide, boron carbide, silicon nitride, and silicon carbide. Preferably, fibers made of materials such as , carbon, etc. can be used alone or as a mixture. Further, it may be made into short fibers or powdered as required. A preferable range of the required amount of the fiber material is α1 to 10 parts by weight per 1 part by weight of the molding aid.

The solid wax can be selected from mineral waxes, animal and vegetable waxes, modified waxes, synthetic waxes, synthetic hydrocarbons, hardened oils and fats, etc., singly or as a mixture, and has a melting point in the range of 40°C to 100°C. A particularly preferred example is paraffin wax.

Furthermore, in order to improve the fluidity during melting, polyethylene, ethylene-vinyl acetate copolymer, polypropylene, butyl rubber, petroleum resin, or other thermoplastic resin may be added as necessary.

The colloidal inorganic binder containing solvent water produces a strong bonding force in the composition when dried (dehydrated), and is selected depending on the purpose, fiber material, etc. Suitable examples are colloidal silica, colloidal alumina, and colloidal alumina.
These include idal zirconia, ethyl silicate hydrolyzate, water-dispersed clay, and aqueous dispersion of ultrafine metal powder, but Monoke colloidal silica is particularly preferred for general use. Add amount and solid content concentration before binding as necessary! 11! It can be arranged.

The dispersion aid is an essential component for uniformly dispersing the molding composition, especially the solid wax and solvent water. Suitable examples include surfactants such as anionic surfactants, cationic surfactants, nonionic surfactants, and amphoteric surfactants, polysaccharides such as alginic acid derivatives, starch derivatives, cellulose conductors, and proteins such as gelatin, casein, and albumin. , natural rubbers such as gum arabic and gum tragacanth, and various water-soluble polymers such as polyvinyl alcohol, polyvinyl butyral, polyethylene glycol, polyoxyethylene, polyacrylate, and lignin sulfonate, singly or in combination. However, it is particularly preferable to use a mixture of two or more. Furthermore, various resin emulsions and ceramic powders can be added as necessary.

In addition, especially when a surfactant is used together as a dispersion aid, it is preferable to add it within a range that does not excessively emulsify the solid wax and solvent water. This is because when the dispersion system becomes W2O type (water-in-oil type), it becomes difficult to dry (dehydrate) the molded body (green), and when the dispersion system becomes 0/W type (oil-in-water type), the strength of the molded body (green) decreases. This is because it becomes difficult to maintain the shape when degreasing the mold.

Next, the features and effects of the method for producing a heat-resistant inorganic fiber molded article according to the present invention will be explained in detail based on the attached production process diagram.

FIG. 1 shows the manufacturing process of the present invention, and FIG. 2 shows the conventional manufacturing process (injection molding method using ceramic powder as a raw material).

In this invention, the heating and mixing process of a composition made of heat-resistant inorganic fibers, a solid hook, a colloidal inorganic binder containing solvent water, and a dispersion aid is almost the same as in the conventional injection molding method. However, since the object to be heated is a water-containing composition, the heating temperature is preferably 100° C. or lower.

The molding process is similar to that of conventional injection molding, but
Other molding methods such as pressure molding, extrusion molding, and roller molding can also be used. After molding, the holding time ranges from several seconds to several minutes (
(water cooling if necessary) to solidify into a hard compact (green)
However, since a small amount of solvent water is sweated out during solidification, it has excellent release properties and can be easily demolded. In addition, it has excellent moldability, IIL1111I
It can be molded even with a certain thickness.

The drying process is the process that best characterizes the molding method according to the present invention, and is a process that completely dehydrates the solvent water uniformly dispersed inside the reeds and molded body (green) and creates a strong bonding force of the inorganic binding agent. It is. For this purpose, ventilation dryers are particularly preferred, drying at temperatures below the deformation temperature of the solid wax, preferably below 40°C. Although the time required varies depending on the thickness and shape of the molded product, sufficient dehydration can normally be achieved within a range of 5 to 48 hours.

The degreasing process is the process in which the effects of the molding method according to the present invention are best exhibited, and the molded product that has already undergone the drying process has sufficient shape-retaining strength due to the inorganic binder, so it is not solid. It does not deform or disintegrate due to softening or decomposition of wax or other organic substances. Therefore, it is possible to degrease complex-shaped molded bodies and irregularly shaped bodies with uneven thickness, which are difficult to degrease using conventional methods due to physical and spatial constraints, without requiring a special shaped support. In particular, since ceramic fiber molded bodies inherently have high porosity, their combustibility during dewaxing is extremely good. A heating temperature of about 800° C. is sufficient, and the wax is completely dewaxed in approximately several minutes to several tens of minutes, and a final product with a good shape can be obtained. Note that the dewaxing method may also be a method of recovering wax by thermal extraction or solvent extraction. However, complete dewaxing is difficult with these methods.

Next, examples of this invention will be shown below.

Examples Aluminosilicate fibers which are ceramic fibers were used as heat-resistant inorganic fibers, paraffin wax (melting point 60°C) gold was used as the solid wax, and colloidal silica liquid (solid content 30%) was used as the colloidal inorganic binder containing solvent water.
Nonionic activator (alkyl ether type) as a dispersion aid
and polyoxyethylene (molecular weight 1,000,000) t- selected and blended in various proportions shown in Table 1, hollow elbow-shaped molded bodies with protrusions (wall thickness 5
m) was created.

The molding conditions were: heating crosstalk temperature 80°C, kneader stirring speed 5Qr, p, m, injection temperature 70°C, injection pressure 10°C.
The temperature was 0 Kf/i and the mold temperature was 20°C.

Immediately after demolding the molded body (green), it was dried in a ventilation dryer at 40°C for 15 hours, then placed in a heating oven and demolded at 800°C for 10 minutes without any form support. I waxed it. All the dewaxed products were light and white, and the dimensional accuracy was found to be within 11% and had a good shape. In Example (5), ultrashort fibers (powdered) were used. .

As described above, according to the present invention, in addition to heat-resistant inorganic fibers, a composition containing a solid wax as a forming aid, a colloidal inorganic binder containing solvent water, and a dispersion aid is added to the solid wax. The process consists of heating and kneading at a temperature above the melting point of the solid wax, then cooling it to a temperature below the freezing point of the solid wax to dewax it, drying it, and dewaxing it. Fiber molded bodies can be efficiently mass-produced with high dimensional accuracy.

[Brief explanation of drawings]

Claims (5)

[Claims] (1) In addition to heat-resistant inorganic fibers, a composition containing a solid wax as a forming aid, a colloidal inorganic binder containing solvent water, and a dispersion aid is heated and kneaded at a temperature equal to or higher than the melting point of the solid wax. A method for producing a heat-resistant inorganic fiber molded article, comprising the steps of molding, then cooling to a temperature below the freezing point of solid wax, demolding, drying, and dewaxing. (2) Heat-resistant inorganic fibers include alumina, silica, aluminosilicate, calcium silicate, slag, zirconia, boron oxide, boron carbide, silicon nitride, silicon carbide, carbon,
The method for producing a heat-resistant inorganic fiber molded article according to claim 1, wherein the fiber is selected from glass and asbestos fibers. (3) The method for producing a heat-resistant inorganic fiber molded article according to claim 1, wherein the solid wax is selected from mineral waxes, animal and plant waxes, modified waxes, synthetic waxes, synthetic hydrocarbons, and hydrogenated oils and fats. (4) Colloidal inorganic binders containing solvent water include colloidal silica, colloidal alumina, colloidal zirconia,
The method for producing a heat-resistant inorganic fiber molded article according to claim 1, wherein the method is selected from an ethyl silicate hydrolyzate, water-dispersed clay, and an aqueous dispersion of ultrafine metal powder. (5) Dispersion aids include anionic activators, cationic activators, nonionic activators, amphoteric activators, alginic acid derivatives, starch derivatives, cellulose derivatives, gelatin, casein, albumin, gum arabic, gum tragacanth, polyvinyl alcohol, polyvinyl butyral, polyethylene. The method for producing a heat-resistant inorganic fiber molded article according to claim 1, wherein the molded article is selected from glycol, polyoxyethylene, polyacrylate, and lignin sulforate.