JP2534066B2 - Manufacturing method of ceramic honeycomb structure - Google Patents

Description

The present invention relates to a method for producing a honeycomb structure made of ceramics, which is useful as a heat exchange element or a catalyst carrier.

[Conventional technology]

As a method for manufacturing a ceramic honeycomb structure having good heat resistance, a method of making from ceramic fiber paper (for example, Japanese Examined Patent Publication No. 59-15028), a flammable film supporting a powdery ceramic raw material, and a flammable material have been used. A method for obtaining a honeycomb structure using a tube and then firing it to burn off a flammable carrier and sinter it (Japanese Patent Laid-Open No. Sho 48-58009), mixing water, a plasticizer, etc. with a ceramic raw material powder. A method is known in which a clay-like material is extruded and then sintered.

Among these, the method using ceramic fiber paper as a raw material can reduce the weight of the product because the density of the base ceramic fiber paper is low, but it is difficult to obtain a high-strength product and the rigidity is high. There is also a problem that the shaping process of the ceramic fiber paper is not easy. Further, since the partition wall of the product has a high porosity, gas diffusion through the partition wall portion may become a problem. Of the other two manufacturing methods that use powdered ceramic raw materials, the former actually impregnates paper or paper tubes with the ceramic raw materials, so it is difficult to achieve a uniform impregnation amount. Therefore, the thickness unevenness of the ceramic cell partition of the product is likely to occur. Moreover, large voids are formed after the paper serving as the carrier disappears, and airtightness and strength tend to be a problem. In addition, in the method by extrusion molding, it is difficult to make the cell partition wall thin, and therefore, it is not possible to manufacture a cell that is light and has a large specific surface area.

[Problems to be solved by the invention]

The object of the present invention is that, in view of the fact that the conventional methods for manufacturing a ceramic honeycomb structure all have the drawbacks as described above, high strength, high density, low porosity, and uniformity of quality. Another object of the present invention is to provide a method for easily manufacturing the excellent ceramic honeycomb structure of

[Means for solving problems]

The manufacturing method of the present invention that succeeded in achieving the above object is to manufacture a ceramic precursor green sheet by molding a ceramic raw material mixed with a binder into a sheet, and corrugate part or all of it. And then shape it into a corrugated shape, and stack the resulting corrugated green sheets while shifting the phase of those waves, or stack the corrugated green sheets and unprocessed flat green sheets alternately to bond the contacts. By doing so, a honeycomb structure is obtained, and the obtained honeycomb structure is heated to the sintering temperature of the ceramic raw material and fired.

It is already known to produce a green sheet (also referred to as a green sheet) from a powder or other ceramic raw material and sinter it into a ceramic (Japanese Patent Laid-Open No. 58-52).
07, ibid. 59-13667, ibid. 59-213664, ibid. 59-213665, etc.). However, these are all for obtaining thin plate-shaped ceramics for electronic parts, and there is no example in which a green sheet is shaped and processed, and then a three-dimensional structure such as a ceramic honeycomb structure is made and then sintered. Absent.

The present invention has been completed by focusing on the feature that a green sheet easily produces a thin film high-density ceramic and is easily shaped.

Therefore, when a ceramic honeycomb structure is manufactured by the structural method of the present invention, a green sheet is first manufactured. A ceramic raw material for that purpose, an auxiliary raw material for enabling sheet formation, other, film thickness, production The film method or the like can be arbitrarily selected according to the characteristics required for the product.

The usual available ceramic material, alumina, cordierite, silica, zirconia, B _a TiO _2, silicon nitride, alumina nitride, other inorganic powder that gives ceramics readily sinter when heated to high temperatures, boehmite sol , Sol of various metal oxides such as silica sol and zirconia sol; alkoxides of metals such as aluminum, magnesium, calcium and zirconium, chelate compounds, chlorides, nitrates and organic acid salts. A small amount of an inorganic salt of a metal (for example, chloride such as magnesium, calcium, chromium, or nitrate) that suppresses grain growth during the firing treatment may be added to these raw materials.

Since many of these ceramic raw materials cannot form a handleable sheet even if water is added and kneaded as they are, organic binders, plasticizers, peptizers, wetting agents,
By appropriately adding a solvent or the like, the sheet forming property, the sheet strength, and the workability are improved. As the binder, methacrylic acid ester copolymer, polyvinyl alcohol, methyl cellulose, polyvinyl butyral and the like can be used. As a plasticizer, phthalate ester, polyethylene glycol, etc., and as a deflocculant, a fatty acid,
Acrylic oligomers and the like can be used, and glycerin, alcohols and surfactants can be used as the wetting agent. As the solvent, water, ketone, alcohol or the like can be used. The above is the auxiliary raw material when the film is formed by the so-called doctor blade method, but the film can also be formed by the so-called calendar method. In that case, an ethylene vinyl copolymer, polystyrene, or the like can be used as the thermoplastic resin mixed with the ceramic raw material.

In the case of using the doctor blade method, an example of raw material blending is as follows.
0 parts by weight, 0 to 10 parts by weight of plasticizer, and 20 to 60 parts by weight of solvent, which are sufficiently mixed in a ball mill or a mixing tank. The obtained paste-like mixture (slip) is defoamed and then formed into a sheet having an appropriate thickness by using a fluororesin film, a polyester film or the like as a carrier film (for example, a honeycomb structure for a heat exchange element is formed). A suitable green sheet thickness to produce is typically about 0.1.
~ 0.5 mm). It is then dried with the carrier film and peeled from the carrier film once the self-supporting sheet is formed from the raw mixture.

The green sheet obtained as described above has the strength, flexibility, shapeability, etc. necessary for forming a corrugated sheet necessary for manufacturing a honeycomb structure, if the raw material composition is appropriate. Therefore, it is possible to easily form the corrugated shape by using a corrugating machine or the like used in the production of ordinary corrugated paper.

The step of manufacturing the honeycomb structure from the corrugated green sheet may be carried out according to a conventional method for manufacturing a honeycomb structure.
That is, an adhesive is applied to the corrugated heads on both surfaces of the corrugated green sheet, and the corrugated green sheet is bonded to another corrugated green sheet in such a manner that a space is formed between the corrugated sheets by shifting the phase of the wave. . A honeycomb structure is formed by stacking a plurality of sheets while adhering them. Alternatively, the corrugated green sheets and the unprocessed flat plate-like green sheets are alternately laminated and laminated. In these cases, the relative placement of each corrugation in adjacent corrugated sheets is
Determine according to the application of the product. Further, it is also possible to wind up in a spiral shape while applying the adhesive after the corrugated sheet and the flat sheet are adhered. As an adhesive used for adhering the green sheets to each other, a slip for forming the green sheets is suitable, and it may be used after appropriately diluted with a solvent.
However, the adhesive portion may be heated and fused under pressure without using the adhesive agent.

Sintering of a honeycomb structure made from green sheets is performed by pre-firing at a temperature at which organic substances are decomposed, and then by raising the temperature to a sufficiently high temperature and firing according to the sintering start temperature of the ceramic raw material used. . For example, when alumina is used as a raw material, the organic matter is burned off at about 500 to 800 ° C., and then fired at about 1500 to 1700 ° C. to form a ceramic.

1 to 5 show examples of the honeycomb structure which can be manufactured by the manufacturing method of the present invention as described above.

〔Example〕

 Hereinafter, the present invention will be described with reference to examples.

Example 1 A slip using alumina powder as a ceramic raw material was prepared and formed into a film with a doctor blade device to produce a green sheet having a thickness of 0.2 mm after drying. The obtained green sheet was formed into a corrugated shape by a corrugating machine for producing corrugated paperboard, and a honeycomb structure having a structure shown in FIG. 5 was prepared by using the slip having the same composition as the above-mentioned slip as an adhesive.
Then, after drying at 110 ° C., the organic matter was burned off at 800 ° C., and further sintered at 1550 ° C. to obtain an alumina ceramic honeycomb structure.

Examples 2 to 3 An alumina honeycomb structure was manufactured in the same manner as in Example 1 except that the slip formulation was partially changed.

Example 4 A zirconia-based ceramic honeycomb structure was manufactured in the same manner as in Example 1 except that the slip formulation was changed to that of zirconia and the sintering was changed to 1450 ° C.

The raw material composition and the physical property values of the products in each of the above examples are summarized in Table 1.

The porosity is a value calculated by the following formula, and the thickness variation and the density variation are measured by the following method.

Porosity = [1- (Honeycomb density / original plate density)] x 100 Thickness variation: Cut the flat sheet after firing into 50 mm squares and measure the thickness at four randomly selected points with a micrometer. Ask.

Density fluctuation: Determined from the density measured by the Archimedes method for 20 samples.

[Effects of the Invention] As described above, the manufacturing method of the present invention via a green sheet is capable of manufacturing a honeycomb structure including partition walls having a thin and dense structure more accurately and easily than by a conventional manufacturing method. You can Therefore, according to the manufacturing method of the present invention, a honeycomb structure having a large porosity can be easily obtained, and therefore, a honeycomb structure having a fine cell pitch (a small specific surface area, which is conventionally difficult to manufacture, is advantageous as a catalyst carrier). Further, when used in a heat exchanger or an ion concentration cell, etc., the smaller the cell thickness is, the higher the efficiency becomes.

Further, the product according to the production method of the present invention, which has a dense partition wall by not using a fibrous material, is not only high in strength, but also has little gas permeation in the cell partition wall portion and is particularly excellent as a heat exchange element. Show performance.

[Brief description of drawings]

1 to 5 are perspective views showing examples of honeycomb structures which can be manufactured by the method of the present invention.

Claims (3)

(57) [Claims] 1. A ceramic raw material mixed with a binder is formed into a sheet to produce a green sheet which is a ceramic precursor, and a part or all of the green sheet is corrugated to obtain a corrugated shape. A honeycomb structure was obtained by stacking corrugated green sheets while shifting the phases of those waves, or by alternately stacking corrugated green sheets and unprocessed flat green sheets and adhering the contacts to obtain a honeycomb structure. A method of manufacturing a ceramic honeycomb structure, comprising heating the honeycomb structure to a sintering temperature of the ceramic raw material and firing the same. 2. The method according to claim 1, wherein an easily sinterable inorganic powder is used as a ceramic raw material. 3. The method according to claim 1, wherein a sol of metal oxide is used as a ceramic raw material.