JPH0718661B2 - Method for manufacturing lightweight heat-resistant tray for firing ceramics - Google Patents

Description

The present invention relates to a method for manufacturing a lightweight heat-resistant tray for firing thin plate-shaped molded products of ceramics, glass, and various metal oxides.

[Conventional technology]

In the recent information and electronics industries, functional parts such as sensors, capacitors, and IC substrates are shifting to ceramics. Among them, fine ceramics such as alumina and silicon nitride, dielectric elements such as barium titanate and magnetic materials such as iron, barium and strontium are considered promising. These ceramics and metal oxides are excellent in the properties of electrical insulation, semiconductivity, heat resistance, wear resistance, high strength, and high magnetic force, and their applications are expanding more and more in the future. After mixing the raw materials, these functional parts are molded into various shapes by an extrusion molding method, an injection molding method, etc., and then placed on a baking tray and baked to be manufactured. For this firing tray, mullite, alumina, zirconia, cordierite, silicon carbide and silica refractories are used.

[Problems to be solved by the invention]

Conventionally, all of the trays for firing functional parts such as ceramics are formed by a method such as pressing and further fired at a high temperature. However, since the baking trays used in the past have a high bulk density, it requires a large amount of energy to heat itself, and since they are heavy, there is a limit to stacking them when stacking them in multiple stages. there were. Further, it was difficult to make the temperature distribution uniform in the upper and lower stages in the furnace. When the firing speed was further increased or the cooling / heating cycle was accelerated, the firing tray was cracked, resulting in poor productivity. Further, in order to reduce the firing zone to improve the thermal efficiency, the volume occupied by the firing tray should be reduced, but the conventional firing tray could not be manufactured with a certain thickness or less due to problems such as warpage. On the other hand, a lightweight molded article is known in which heat-resistant inorganic fibers such as ceramics fibers and an inorganic binder (for example, silica sol, clay, sepiolite, etc.) are formed into a slurry with a large amount of water and are formed by a wet papermaking method. However, this molded product has not only the smoothness of the surface but also the fact that the inorganic binder is only filled between the lattices of the heat-resistant inorganic fiber (Fig. 2). It is not suitable as a tray for firing ceramics with high precision, because the fiber is weakened, the strength is weak, or the fibers themselves fall off and become powdered.

Further, in JP-A-60-231453, SiO ₂ , Al ₂ O ₃ , Al ₂ O ₃ is disclosed.
Fused with a composition comprising the intersection of the fibers of the -SiO ₂ fiber aggregated in coalesced from SiO _2, B ₂ O _3, it has been proposed for porous refractories having improved strength of the shaped body. However, since the molded body in this publication depends on the strength of the fiber itself, it is still weaker than conventional refractory materials, and therefore softens and deforms during use as a tray or has low surface abrasion resistance and is powdered. There was a problem that it was easy.

Further, a composite ceramics compact reinforced by a ceramic fiber having a recrystallization temperature higher than the firing temperature of the mother phase as proposed in JP-A-59-128273 has a low porosity, It is not lightweight and excellent in thermal shock resistance, and is completely different from the object of the present invention.

As described above, conventional firing trays made of refractory materials and firing trays made of heat-resistant inorganic fibers not only occupy a large weight in energy costs and consumables costs for products, but also lack the strength of the trays themselves. It powdered and deteriorated the working environment and was unsuitable for precise ceramic firing.

The refractory material, as described in JP-A-53-43713 and JP-A-59-88378, is formed by sintering heat-resistant inorganic fibers, refractory powder, and an inorganic binder. However, in these refractory materials, the heat-resistant inorganic fibers cannot be uniformly dispersed, the smoothness of the surface of the molded product is poor, the abrasion resistance and strength of the tray surface are not sufficient, and the powder is pulverized. There is a problem that the softening deformation cannot be prevented.

In order to solve these problems, an object of the present invention is to provide an energy-saving, lightweight, heat-resistant, lightweight heat-resistant tray for firing precision ceramics which is extremely thin and excellent in heat change.

[Means and Actions for Solving Problems] The present invention comprises a heat-resistant inorganic fiber in which the non-fibrous substance in the heat-resistant inorganic fiber is 20% by weight or less, and Al ₂ O ₃ is 40 to 60% by weight. Amorphous silica-alumina fiber or Al ₂ O ₃
Of 70 to 99% by weight and SiO ₂ of 1 to 30% by weight,
Heat-resistant inorganic fiber made of crystalline alumina fiber whose crystals are γ-, η-, δ-, and θ-type transition type alumina.
20-85% by weight, 15-80% by weight of refractory powder crushed to 50 μm, and 1-30% by weight of inorganic binder crushed to 50 μm are dispersed in water to form a slurry solution, and then the mold vacuum is applied. Pressing and compression molding, which is formed by suction or papermaking and further compressed to approximately 30 to 60%, is fired at a temperature range of 1200 to 1600 ° C and at a temperature at which the heat-resistant inorganic fiber is recrystallized or crystallized. Thereby forming uniform and fine voids between the heat-resistant inorganic fibers, filling and sintering the refractory powder in the voids, and utilizing the recrystallization or crystal transition of the heat-resistant inorganic fibers to form the refractory powder. Is a method for producing a heat-resistant tray for firing ceramics, characterized in that the sintering is promoted.

The constituent factors of the present invention and their respective actions will be described below. The main actions are as follows.

(1) A heat-resistant inorganic fiber is dispersed in an inorganic binder such as a fire-resistant powder or an easily sinterable auxiliary agent to form uniform fine voids, which is a structure that is lightweight and has excellent thermal shock resistance.

(2) Alumina, alumina-silica, zirconia, magnesia, and titania refractory powders are filled in the gaps of the heat-resistant inorganic fibers and sintered to obtain a high-strength structure.

(3) Utilizing recrystallization and crystal transition of the heat-resistant inorganic fiber to promote the sintering of the refractory powder filled between the fibers,
High strength and lightweight structure.

The heat-resistant inorganic fiber in the present invention is amorphous silica.
At least one of alumina fiber (hereinafter abbreviated as CF) and alumina crystalline fiber (hereinafter abbreviated as AF) is effective. CF is usually composed of 40-60 wt% of Al ₂ O _{3 and} 40-60 wt% of SiO ₂ , and mullite crystals precipitate near 900 ° C and cristobalite crystals around 1200 ° C, causing grain growth. In the present invention, it is particularly preferable. Also, AF
Is composed of 70 to 99 wt% of Al ₂ O _{3 and 1} to 30 wt% of SiO ₂ , and is a γ-, η-, δ-, θ-type transition type alumina or α-type stable alumina. It is composed of. The above-mentioned transition type alumina is preferable in the present invention because it is transformed into α-form by firing at about 1400 ° C and grain growth occurs. Further, CF is the most suitable because it is low in cost and the fibers are thin so that finer voids can be formed. However,
The non-fibrous substance in these heat-resistant inorganic fibers not only loses the smoothness of the surface of the molded body but also becomes heavy in weight, so that it is necessary to set the content to 20% by weight or less in order to obtain the lightweight heat-resistant tray of the present invention. . At least 20 of these heat-resistant inorganic fibers
~ 85 wt% is required, and preferably 30-60 wt%. If it is less than 20% by weight, the amount of the inorganic binder is relatively large, the voids are small, and it is heavy, and cracks are likely to occur.
Also, if it exceeds 85% by weight, it becomes lighter but its strength is small and deformation occurs.

As the refractory powder of the present invention, any one or more selected from alumina, alumina / silica, zirconia, magnesia, and titania has a high fire resistance temperature and is suitable. Specifically, alumina, mullite, kaolinite, kibushi clay, frog eye clay, sillimanite, steatite, forsterite, zirconia, magnesia, spinel, titania, etc. are preferable, and the compounding amount is preferably 15 to 80% by weight. . If it is less than 15% by weight, the bonding strength of the molded product will be weak, and if it exceeds 80% by weight, it is heavy and easily cracked, which is not preferable.

Further, the inorganic binder of the present invention is preferably one or more selected from silica / soda-based, calcium borate-based, and silica-based frits. For example, feldspar,
Mica powder, boric acid, limestone, petalite, glass powder,
Silica or the like is preferable, and the compounding amount is preferably 1 to 30% by weight. If it is less than 1% by weight, it loses its function as a binder.
If it exceeds 30% by weight, the fire resistance temperature of the molded article becomes low, which is not preferable.

These refractory powders and inorganic binders are mixed in advance with a composition that sinters at a predetermined temperature, and then pulverized to about 50 μm by a pulverizer such as a ball mill before use.

The heat-resistant inorganic fibers and the refractory powder and the inorganic binder, after being dispersed in water to form a slurry solution,
Molding is carried out by a method such as mold vacuum suction, cast molding, and papermaking. Preferred is a method of forming a slurry solution and then molding by vacuum suction or papermaking because the fibers can be uniformly dispersed.

In order to improve the yield of the composition consisting of the heat-resistant inorganic fiber, the refractory powder, and the inorganic binder in vacuum suction or papermaking, a general polyacrylamide-based material,
Alternatively, a coagulant such as polyvalent basic aluminum is added. Further, in order to improve the handling strength at room temperature, general organic binders such as starch and latex are suitable, and organic fibers such as pulp and hemp can also be used. Furthermore, when preparing a kneaded product, a small amount of a thickening agent such as CMC or sodium alginate can be added.

The above composition is molded by a press molding method that compresses approximately 30 to 60% by a flat plate press having a hydraulic cylinder,
After drying, it has a bulk density of 0.4 to 1.5 g / cm ³ and has a small restorability and excellent dimensional accuracy. This compact can be fired in a heating furnace equipped with a heating element or a burner at a temperature of 1200 to 1600 ° C. for 2 hours or more, and after cooling, the lightweight heat-resistant tray of the present invention shown in FIG. 1 can be obtained. The firing temperature can be arbitrarily changed depending on the blending ratio of the inorganic binder,
It is necessary that the temperature is equal to or higher than the temperature actually used for firing ceramics, or higher than the recrystallization or transition temperature of the heat resistant inorganic fiber, and at least 12
00 ° C or higher is required. Desirably, a calcination temperature of 1400 to 1500 ° C is economically preferable, but a calcination temperature of 1600 ° C may be required depending on the composition.

The method for manufacturing the ceramics lightweight heat-resistant tray of the present invention will be described in detail in the following examples.

〔Example〕

Example 1 225 g of calcined alumina powder and 40 g of calcium borate were mixed,
JISZ-8801 is crushed for 24 hours with a commercially available ball mill crusher.
After passing through the standard sieve 250 mesh specified in 1., 400g of AF and 30ml of acrylonitrile butadiene latex (42% solution) were mixed and stirred in 20 of water as an inorganic binder. Then add 240 ml of sulfuric acid band (10% solution),
This was a slurry-like mixed liquid. 35 × 40 cm of this slurry liquid
Was transferred to a rectangular paper making machine of No. 1 and the excess water was dehydrated with a Nash pump to obtain a forming plate having a thickness of 10 mm. The formed plate was inserted into a hydraulic flat plate press and pressed at a pressure of 20 kg / cm ² to obtain a formed body having a thickness of 6 mm. The dry density of the molded body was 0.80 g / cm ³ . After polishing the surface of this compact 140
Baking was performed in a furnace at 0 ° C. for 24 hours. The physical properties of the obtained molded product were as shown in Table 1.

Example 2 300 g of calcined alumina, 185 g of kaolin, 115 g of glass frit
The mixture consisting of was pulverized and selected in the same manner as in Example 1 to obtain an inorganic binder. Separately from this, CFg and 40 ml of cationized starch (20% solution), which had been treated to have a non-fibrous substance content of 18% by washing with water, were mixed in 20 n of water and stirred. Next, a polyacrylamide type coagulant (0.5% solution) was added and coagulated to prepare a slurry-like mixed liquid. The slurry-like mixed liquid was subjected to papermaking and pressing in the same procedure as in Example 1 to obtain a molded product having a thickness of 6 mm. After the surface of this formed body was polished, it was baked in a furnace at 1300 ° C. for 24 hours. The physical properties of the obtained molded product were as shown in Table 1.

Example 3 As in Example 1, the inorganic binder was 110 g of kaolin and quartz.
AF200g as a crushed product of a mixture of 60g and soda feldspar, 200g of CF used in Example 2 and 30ml of styrene-butadiene rubber latex (solid content 42%) were mixed and stirred in 20 water. Then add 80 ml of polyacrylamide solution (15% solution) and 200 ml of aluminum sulfate solution (10% solution),
This was a slurry-like mixed liquid. Papermaking and pressing were performed from this slurry-like mixed liquid in the same procedure as in Example 1 to obtain a molded product having a thickness of 5 mm. After surface polishing this molded body in a furnace at 1350 ℃
It was baked for 24 hours. The physical properties of the obtained molded product are as shown in Table 1.

Example 4 As in Example 1, as the inorganic binder, calcined alumina fine powder 20
0g, Kibushi clay 120g, calcium borate 80g crushed product and AF400g and cationized starch (20% solution) 40ml
Mix into 20 water and stir. Next, 180 ml (0.5 solution) of a polyacrylamide-based coagulant was added to form a slurry mixed liquid, and papermaking and pressing were performed in the same procedure as in Example 1 to obtain a molded product having a thickness of 6 mm. This molded body is placed in a furnace at 1400 ° C for 10
The physical properties after the time calcination were as shown in Table 1.

Example 5 As in Example 1, using 400 g of kaolin, 10 g of montmorillonite, and 35 g of calcium borate as an inorganic binder, which had been mixed and pulverized, 400 g of CF and nitrile butadiene latex (42%) obtained in the same manner as in Example 2 were used. Solution) 30ml and 20
Was dispersed in water and mixed and stirred. Then, 240 ml of aluminum sulfate (10% solution) was added to form a slurry-like mixed liquid, and then a 6 mm molded body was obtained by the same procedure as in Example 1. After firing this formed body in a furnace at 1350 ° C., a formed body having physical properties as shown in Table 1 was obtained.

Example 6 A ground product of 355 g of alumina powder, 270 g of kibushi clay and 70 g of calcium borate as the same inorganic binder as in Example 1 and Example 2
The CF (450 g) used in Example 1 and styrene-butadiene rubber latex (solid content 42%) 80 ml were mixed and stirred in 20 water.
Then, 600 ml of a polyacrylamide solution (7.5% solution) and 670 ml of an aluminum sulfate solution were added to prepare a slurry-like mixed solution. Papermaking / pressing was performed from this slurry-like mixed liquid in the same procedure as in Example 1 to obtain a molded body having a thickness of 10 mm. After the surface of this formed body was polished, it was baked in a furnace at 1400 ° C. for 24 hours. The physical properties of the obtained molded product are as shown in Table 1.

Example 7 Easily sinterable alumina powder as an inorganic binder as in Example 1.
170 g of the pulverized product and 545 g of CF used in Example 2 which had been previously pulverized to shorten the CF were mixed and stirred in 20 l of water. Then add 970 ml of polyacrylamide solution (7.5% solution) and 1090 ml of aluminum sulfate solution (10% solution),
This was a slurry-like mixed liquid. Papermaking and pressing were performed from this slurry mixture by the same means as in Example 1 to obtain a molded body having a thickness of 10 mm. The dry density of this molded body was 1.3. After the surface of this formed body was polished, it was baked in a furnace at 1400 ° C. for 24 hours. The physical properties of the obtained molded product were as shown in Table 1.

Example 8 As in Example 1, easily sinterable alumina powder as an inorganic binder
925 g of the ground product and 615 g of CF used in Example 7 were mixed and stirred in 20 water. Then polyacrylamide solution (7.5
% Solution) 820 ml and aluminum sulfate solution (10% solution) 9
25 ml was added to obtain a slurry-like mixed liquid. Papermaking and pressing were performed from this slurry mixture by the same means as in Example 1 to obtain a molded body having a thickness of 10 mm. The dry density of this molded body was 1.1. After polishing the surface of this compact 1400 ℃
Baking was performed in the furnace for 24 hours. The physical properties of the obtained molded product are as shown in Table 1.

Comparative Example 1 20 g of methylcellulose powder and 120 g of water were added to 2 kg of a mixture consisting of 13% by weight of calcined alumina fine powder, 48% by weight of kaolin and 39% by weight of talc, and the mixture was sufficiently kneaded in a kneading machine. The kneaded product thus obtained was transferred into a mold prepared by plastering with gypsum, press-formed and dried to obtain a molded product having a thickness of 10 mm. The molded product was heated in a furnace at 1350 ° C. for 24 hours and then gradually cooled to room temperature to obtain a baking tray. The physical properties of the molded product thus obtained are as shown in Table 1.

Comparative Example 2 To 1 kg of a mixture consisting of 13% by weight of calcined alumina fine powder, 48% by weight of kaolin and 39% by weight of talc, 10 g of methylcellulose powder, 160 g of sufficiently fine sawdust and 540 g of water were added and kneaded in a kneader. The kneaded material thus obtained was transferred into a preformed mold with gypsum and press-formed to obtain a molded product having a thickness of 10 mm after drying. This molded product
It was heated in a furnace at 1350 ° C. for 24 hours and gradually cooled to room temperature to obtain a tray for baking. The physical properties of the molded article thus obtained are as shown in Table 1. Table 1 is shown below.

As described above, the ceramic lightweight heat-resistant tray obtained in Example 1 was coated with a coating mainly composed of zirconia oxide, and the tray obtained in Comparative Example 1 was used. The ceramic parts for electronics molded by hot pressing with the addition of an organic binder were fired for 10 hours in an electric furnace at a furnace temperature of 1350 ° C. The results are shown in Table 2.

Similarly, an alumina substrate formed by a doctor blade method from a slurry obtained by adding a little magnesia and an organic binder to alumina powder was fired for 12 hours in an electric furnace at a furnace temperature of 1400 ° C. The results are shown in Table 2. As a result, compared with the conventional heat-resistant tray, the weight is reduced by 3.3 to 1.4 times as much as the firing amount per time. Furthermore, the amount of heat carried out by the tray itself is about 1/5, which is also effective in saving energy, and the cost can be reduced as a consumable item because a product can be produced by about 1.1 to 2.8 times per tray.

Table 2 is shown below.

[Effects of the Invention] As described above, according to the present invention, the following effects occur.

(1) The ceramics heat-resistant tray is reduced in weight to reduce the heat capacity, and the firing cost is reduced.

(2) The thermal shock resistance of the ceramic baking heat resistant tray is improved, the life is extended, and the cost of consumables is reduced.

(3) Ceramic firing It is possible to prevent powdering of the heat-resistant tray, improve the working environment, and fire ceramics precisely.

(4) The heat-resistant inorganic fibers can be uniformly dispersed, the surface of the molded article can be made excellent in smoothness, and the wear resistance and strength of the surface of the lightweight heat-resistant tray for firing ceramics can be improved.
It is possible to prevent pulverization and softening deformation of the tray.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing the bonding state of the fiber, the refractory powder and the inorganic binder after the high temperature firing of the shaped plate of the lightweight heat resistant tray for firing ceramics of the present invention, and FIG. 2 is the fiber of the conventional heat resistant fiber molded plate. It is a schematic diagram which shows the mixed state of a binder. Explanation of symbols 1 ... Heat-resistant inorganic fiber 2 ... Inorganic or organic binder 3 ... Sinter-bonded inorganic binder 4 ... Refractory powder

Claims (1)

[Claims] 1. The non-fibrous material in the heat-resistant inorganic fiber is 20% by weight.
The following heat-resistant inorganic fibers, 40 to 60% by weight of Al ₂ O ₃
Amorphous silica-alumina fiber consisting of, or
Al ₂ O ₃ is 70 to 99% by weight and SiO ₂ is 1 to 30% by weight, and the crystal thereof is crystalline alumina fiber composed of γ-, η-, δ-, θ-type transition type alumina. 20 to 85% by weight of heat-resistant inorganic fiber, 15 to 80% by weight of refractory powder ground to 50 μm, and 1 to 30% by weight of inorganic binder ground to 50 μm are dispersed in water to form a slurry solution. After that, the press-compression molded body which is molded by vacuum suction or papermaking and further compressed to about 30 to 60% is in the temperature range of 1200 to 1600 ° C, and the heat resistant inorganic fiber is recrystallized or crystallized. By firing above the temperature, uniform and fine voids are formed between the heat-resistant inorganic fibers, the refractory powder is filled and sintered in the voids, and recrystallization or crystal transition of the heat-resistant inorganic fibers is used. The sintering of the refractory powder Fired ceramic heat resistant tray manufacturing method characterized by comprising by advancing.