JPH09175857A - Ceramic product and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a ceramic product having excellent strength, resistance to thermal shock and low thermal conductivity by including respectively specific amount of zircon and cordierite in the product. SOLUTION: This ceramic product contains 5-70wt.% of zircon and 95-30wt.% of cordierite. The objective ceramic product is one of an adiabatic insulating bush of an oxygen sensor measuring O2 concentration in an exhaust gas of an automobile, a burner nozzle, an insulator of a heating element or a light emitter, and a heater cover. The ceramic product is produced by combining a process mixing zircon powder with cordierite powder, preferably having 0.2-4.0μm average particle diameter, so as to become 5-70wt.% of zircon and 95-30wt.% of cordierite, with a process adding a binder to the resultant mixed powder and subjecting to injection molding to obtain a molded material.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ceramic product and a method for manufacturing the same, and more particularly to a ceramic product excellent in thermal shock resistance, strength and thermal conductivity and a method for manufacturing the same.

[0002]

2. Description of the Related Art In the manufacture of heat insulating insulation bushes up to now,
A product is obtained by forming a simple and large molded body in advance by CIP (Cold Isostatic Pressing) molding or extrusion molding, processing the molded body with a cutting machine into a desired shape, and then firing the molded body. Steatite is mainly used as the material of the above products.

In the conventional manufacture of burner nozzles, CI
A product having a desired shape such as a screw shape or a hole shape was obtained by making a simple and large molded body in advance by P molding, press molding or cast molding and processing the molded body with a cutting machine. . Low purity alumina, porous alumina and cordierite are mainly used as the material of the above products.

In the conventional manufacturing of insulators for heating elements and light-emitting elements, press molding and extrusion molding have been used in order to simplify the product and make it more than one. Steatite and cordierite are mainly used as materials for the above products.

[0005]

At present, steatite is often used mainly for the heat insulating and insulating bush. However, steatite has a poor thermal shock resistance and is used in a place where a thermal cycle is repeated. And cracks may occur. Further, since the material is single, it is difficult to adjust the physical properties thereof, and steatite is not always satisfying the required characteristics of the product. Since the product is made by consolidating the granular material by CIP molding or by extruding and drying the kneaded material by the extrusion molding method, only a simple shape with poor dimensional accuracy can be made. Therefore, it is necessary to cut the molded body into a desired shape, which increases the cost. Moreover,
Complex shaped products cannot be made. In addition, there is a problem that the working environment is deteriorated by the dust generated during cutting.

At present, low-purity alumina, porous alumina and cordierite are mainly used for burner nozzles. However, in these materials, if the strength is increased, the thermal shock resistance decreases, and if the thermal shock resistance is increased, the strength decreases. Thus, none of these materials are optimal materials that satisfy both good strength and thermal shock resistance. Further, in the CIP molding method, the press molding method, and the casting molding method, the screw portion and the hole portion are post-processed, and the cost becomes high.

At present, steatite and cordierite are mainly used for insulators of heating elements and light-emitting elements, and simple shaped products are manufactured by press molding or extrusion molding. Depending on the shape, this insulator is manufactured by dividing it into a plurality of parts. Steatite has relatively high strength but low thermal shock resistance. On the other hand, cordierite has high thermal shock resistance but low strength. For this reason, there is no material that has good strength and thermal shock resistance and is optimal for the insulator of the heating element and the light emitting element. Further, in the case of being divided into a plurality of parts to be formed, the cost becomes high due to the complexity of the manufacturing process.

Therefore, an object of the present invention is to provide a ceramic product having both very good strength and thermal shock resistance.

Another object of the present invention is to provide a manufacturing method capable of manufacturing a ceramic product having a complicated shape at a low cost by using a material most suitable for the required characteristics.

[0010]

The ceramic product of the present invention contains zircon in an amount of 5 to 70% by weight and cordierite in an amount of 95 to 30% by weight.

In the above aspect, a ceramic product is manufactured by using a raw material in which cordierite having excellent thermal shock resistance and low thermal conductivity is mixed with zircon having high strength. Therefore, a ceramic product having high strength and very good thermal shock resistance can be obtained.

When the content of zircon is less than 5% by weight or the content of cordierite is more than 95% by weight, the strength (bending strength) value is lower than that of the existing steatite. I will end up. On the other hand, zircon is 7
More than 0% by weight or 3 cordierite
If it is less than 0% by weight, the value of thermal shock resistance will not satisfy the appropriate value required for the above-mentioned ceramic products, or will be lower than the thermal shock resistance of the existing steatite or alumina.

The ceramic product contains zircon 2
0 to 30% by weight and 80 to 7 cordierite
It is desirable to have 0% by weight.

Since the ceramic product has zircon and cordierite in the above weight%, the characteristic values of steatite can be improved in terms of thermal conductivity and resistivity.

If the zircon content is more than about 30% by weight or the cordierite content is less than about 70% by weight, the thermal conductivity will be higher than that of steatite.

In the above aspect, preferably, the ceramic product is any one of a heat insulating and insulating bush of an oxygen sensor for measuring an oxygen concentration in exhaust gas of an automobile, a burner nozzle, an insulator of a heating element or a light emitting element, and a heater cover. is there. The heater cover is defined as a cover that covers the heat source in order to separate the heat source from the fluid to which heat is applied from the heat source.

Even when the above-mentioned ceramic products are used for these purposes, the ceramic products sufficiently satisfy the high strength required for these purposes and, at the same time, have very good thermal shock resistance and low thermal conductivity. Have. In addition, the thermal shock resistance, thermal conductivity, and strength can be arbitrarily changed by changing the compounding ratio of cordierite and zircon, so that it is possible to easily select a material suitable for the intended use.

In the method for producing a ceramic product of the present invention, zircon powder and cordierite powder are mixed and mixed so that zircon is 5 to 70% by weight and cordierite is 95 to 30% by weight. A powder is obtained. Then, a binder is added to this mixed powder and injection molding is performed to obtain a molded body.

In the manufacturing method of the present invention, the mixed powder and the binder are mixed and kneaded, for example, and then formed into a molded body by an injection molding method. For this reason, the two powder raw materials are uniformly dispersed in this molded body, and can be sintered densely. As a result, a ceramic product having high strength and very good thermal shock resistance can be obtained.

Further, if the injection molding method is used, a molded article having a high precision and a complicated and fine shape can be obtained, so that post-processing is eliminated, material loss can be reduced, and a clean working environment can be maintained.

In the above aspect, preferably, the zircon powder has an average particle size of 0.2 μm or more and 4.0 μm or less.

By using fine particles of zircon having an average particle diameter of 4.0 μm or less, a ceramic product having higher strength can be obtained. Further, due to the limitation of the current apparatus, the average particle size of zircon is 0.2 μm or more.

Since zircon has a square particle shape, the cylinder, screw and mold of the molding machine are easily worn. For this reason, zircon has been unsuitable for press molding and injection molding. However, this problem can be solved by using fine particles of zircon as described above.

Fine particle zircon is used in large quantities as a glaze emulsion for ceramics and a raw material for ceramics.
It is always cheap and available. In addition, cordierite is used in large quantities in honeycombs for catalyst frames, etc., and can be obtained at low cost at any time.

[0025]

Embodiments of the present invention will be described below.

Example 1 First, the following raw materials A to E were prepared.

Raw material A: zircon powder raw material having an average particle diameter of 5.89 μm and specific surface area of 0.696 m ² / g (see FIG. 1) Raw material B: average particle diameter of 3.85 μm, specific surface area 0.805 m
² / g zircon powder raw material (see FIG. 2) Raw material C: average particle size 1.47 μm, specific surface area 1.697 m
² / g zircon powder raw material (see FIG. 3) Raw material D: average particle size 1.06 μm, specific surface area 1.915 m
² / g zircon powder raw material (see FIG. 4) Raw material E: average particle size 0.87 μm, specific surface area 2.135 m
^2- / g zircon powder raw material (see FIG. 5) Each of these zircon powder raw materials A to E has a synthetic cordierite powder raw material (see FIG. 6) with an average particle diameter of 5.62 μm and a specific surface area of 0.688 m ² / g. 50 wt
% Mixed.

1 to 6 show the particle size distribution of zircon powder raw material or cordierite powder raw material, where the vertical axis represents the particle size and the horizontal axis represents the ratio of the number of particles. The ratio of the number of particles is shown as a ratio with the ratio of the number of particles having the largest number of particles being 100. Each of FIGS. 1 to 5 shows the particle size distribution of the raw materials A to E, and FIG. 6 shows the particle size distribution of the synthetic cordierite powder raw material.

The mixing method used was a dry mixing method in which zircon, cordierite and media were placed in a tumbler and mixed by stirring for 4 hours.

The mixed powder obtained by the above method was kneaded with a binder for injection molding by heating and kneading uniformly, and then pelletized to form a cavity having a width of 4.7 mm, a thickness of 3.5 mm and a length of 50 mm. An injection molded body having the above was made by using a bending test piece mold. After degreasing, firing, and polishing the injection-molded body, bending strength, bending elastic modulus,
Bulk specific gravity and water absorption were measured. The results are shown in Table 1 below.

[0031]

[Table 1]

From the results shown in Table 1, it was found that the smaller the average particle size of zircon, the higher the bending strength, the bending elastic modulus, and the bulk specific gravity, and the lower the water absorption. The particle size of zircon powder is 3.85 μm (about 4.0 μm).
m) or less, the strength of steatite (163MP
It was found that a higher strength than that of a) was obtained.

Example 2 Zircon powder raw material E (see FIG. 5) having an average particle size of 0.87 μm and a specific surface area of 2.135 m ² / g and an average particle size of 5.6.
A synthetic cordierite powder raw material (see FIG. 6) having a particle size of ² μm and a specific surface area of 0.688 m ² / g was mixed at 50 wt%. The mixing method is a wet mixing method in which zircon, cordierite, water and media are placed in a ball mill and stirred and mixed for 24 hours and then pulverized, and a dry mixing method in which zircon, cordierite and media are placed in a tumbler and mixed for 4 hours. Using.

The mixed powders obtained by both of the above mixing methods are uniformly kneaded with a binder for injection molding by heating in a pressure kneader, then pelletized, and the width is 4.7 mm and the thickness is 3.5 m.
An injection molded body having a cavity of m and a length of 50 mm was made by using a bending test piece mold. After degreasing, firing, and polishing the injection-molded body, bending strength, bending elastic modulus, bulk specific gravity, and water absorption were measured. The results are shown in Table 2 below.

[0035]

[Table 2]

From the results shown in Table 2, it was found that the dry mixing method had higher bulk specific gravity, flexural strength and flexural modulus than the wet mixing method.

Further, these samples were observed by SEM. FIG. 7 shows an SE obtained by enlarging the structure of a sample (ceramics) obtained through the wet mixing method by 1500 times.
It is an M photograph. In addition, FIG. 8 shows an S of a sample (ceramics) obtained through the dry mixing method which is magnified 1500 times.
It is an EM photograph. Referring to FIG. 7 and FIG. 8, the darker colored portion is cordierite and the lighter colored portion is zircon. Thus, there was no difference in the grain boundary state of these fired bodies, and there was no great difference in the dispersion state of the particles of the fired bodies obtained through the wet method and the dry method.

From the above, even in the dry mixing method, zircon and cordierite can be uniformly dispersed by a process of producing an injection molding material that can sufficiently apply shear stress, which is a practical problem. I knew it wasn't.

Example 3 Using the same raw materials as in Example 2, the weight mixing ratios of zircon and cordierite were 100: 0 and 95: 5, respectively.
80:20, 70:30, 60:40, 50:50, 4
After mixing the raw materials at 0:60, 30:70, and 0: 100 by the dry mixing method, the bulk specific gravity, water absorption rate, bending strength, and bending elastic modulus were measured in the same manner as in Example 2. The results are shown in Table 3 below. The physical properties of steatite obtained by the CIP molding method are shown in Table 4 below.

[0040]

[Table 3]

[0041]

[Table 4]

From the results shown in Tables 3 and 4, the bending strength of the mixture of zircon and cordierite is better than that of steatite when the mixing ratio of zircon and cordierite is 5:95 to 100: 0. It was great. The bulk specific gravity is such that the mixing ratio of zircon and cordierite is 30 :.
In the range of 70 to 0: 100, it was equal to or smaller than the bulk specific gravity of steatite.

Example 4 A bending test piece having a weight mixing ratio of zircon and cordierite of 20:80 was prepared in the same manner as in Example 3 and the high temperature bending strengths at 500 ° C. and 800 ° C. were measured. Compared to that of steatite. The results are shown in Table 5 below.

[0044]

[Table 5]

From the results of Table 5, 500 ° C and 800 ° C
In both cases, the bending strength of the zircon and cordierite mixture was higher than that of steatite.

Example 5 In the same manner as in Example 3, a test piece having a diameter of 10 mm and a thickness of 1 mm was mixed at a weight mixing ratio of zircon and cordierite of 80:20, 60:40, 50:50, 30: 7.
It was prepared from a mixed material of 0 and 20:80 and a material of 100% cordierite, and the thermal conductivity was measured. A similar test piece was prepared using steatite by the CIP molding method, and the thermal conductivity was measured. The results are shown in Table 6 below.

[0047]

[Table 6]

From the results shown in Table 6, the weight ratio of zircon and cordierite was about the same as that of steatite in the calcined body of 30:70, and the weight ratio of cordierite was about 70% or more. (When the zircon weight mixing ratio is about 30% or less), the thermal conductivity becomes smaller than that of steatite. From this, if importance is placed on heat insulation, the weight mixing ratio of cordierite should be 70% or more,
It was found that the weight mixing ratio of zircon should be 30% or less.

Further, as compared with dense alumina, the thermal conductivity was much smaller than that of dense alumina, regardless of the mixing ratio of zircon and cordierite.

Example 6 In the same manner as in Example 3, a test piece having a width of 4 mm, a thickness of 3 mm and a length of 30 mm was mixed with a mixture of zircon and cordierite at a weight mixing ratio of 50:50 and 20:80. And the coefficient of thermal expansion from room temperature to 700 ° C. was measured.
For steatite, a test piece was prepared by the CIP molding method and measured in the same manner. The results are shown in Table 7 below, along with literature values for zircon, cordierite and dense alumina.

[0051]

[Table 7]

From the results in Table 7, the coefficient of thermal expansion of the mixture of zircon and cordierite was significantly lower than that of steatite and dense alumina at the measured weight mixing ratio of zircon and cordierite.

Example 7 In the same manner as in Example 3, the diameter is 20 mm and the thickness is 0.5 m.
A test piece of m was prepared from a mixed material having a weight mixing ratio of zircon and cordierite of 50:50 and 20:80, and the resistivity at room temperature and 500 ° C. was measured. The results are shown in Table 8 below, along with literature values for zircon, cordierite and steatite.

[0054]

[Table 8]

From the results shown in Table 8, it was found that the resistivity of the mixture of zircon and cordierite had no problem in electrical insulation.

Example 8 Using the same raw materials as in Example 3, the weight mixing ratio of zircon and cordierite was 70:30 and 50: 5, respectively.
The raw materials were mixed by a dry mixing method at 0, 30:70 and 20:80. Then, the mixture was kneaded by heating with a pressure kneader together with a binder for injection molding, and then pelletized. A molded body was manufactured by an injection molding method using an injection molding die, and a heat insulating and bushing molded body 1 having a desired shape shown in FIG. 9 was obtained through degreasing and firing steps.

The heat shock resistance of this fired body and the fired body of steatite having the same shape obtained by the CIP molding method were compared by a water cooling method. The results are shown in Table 9 below.

[0058]

[Table 9]

From the results shown in Table 9, the ΔT of the steatite fired body is only 160 ° C. On the other hand, in the case of the mixed material of zircon and cordierite according to the present method, even if the mixing ratio of zircon and cordierite is 70:30, ΔT
Is 200 ° C, and at 20:80 it is more than doubled to 360
It was also found that the mixed material produced by this method had excellent thermal shock resistance, as it was at ℃.

Embodiment 9 As shown in FIGS. 10 (a) and 10 (b), taking advantage of the injection molding method, a meat stab is provided on the outside of the heat insulating and insulating bush 1a,
It was possible to reduce the heat conduction to both ends by reducing the single area.

Incidentally, FIG. 10 (b) shows A of FIG. 10 (a).
It is a schematic sectional drawing which follows the -A line. Example 10 A heat-insulating insulating bush fired body shown in FIG. 9 was manufactured by this method and incorporated in an automobile exhaust gas oxygen sensor as shown in FIG.

Referring to FIG. 11, adiabatic insulation bush 1
Are arranged immediately below the detection element 2 covered with the protector 3. This heat insulating and insulating bush 1 is covered with an outer cap 4 and is screwed to an exhaust pipe 10 by a holder 5.

In this automobile exhaust gas oxygen sensor, + (plus) and-(minus) terminals are connected to the detection element 2, and an electromotive force is generated due to the difference in oxygen concentration between the inside and outside of the exhaust pipe 10. The amount of oxygen is measured by measuring this potential difference.

Further, the heat insulating insulation bush 1 is used for the exhaust pipe 10
And since the temperature of the exhaust gas flowing therein becomes several hundreds of degrees Celsius, the heat insulating insulation bush 1 is required to have heat resistance.

In such an oxygen sensor for automobile exhaust gas,
Incorporating a heat insulating insulation bush fired body manufactured by this method,
As a result of mounting tests, very good results were obtained.

Embodiment 11 FIG. 12 schematically shows an example of a hot water supply device 20 for supplying hot water to a bathtub or the like. As shown in FIG. 12, the hot water supply device 20 includes a casing 21 and a heater 22 arranged in the casing 21. A heater cover 23 made of the above-described ceramic product according to the present invention is provided so as to cover the heater 22. At the bottom of the heater cover 23 is a sealant 24.
Is provided, and packing 25 for sealing is attached between the heater cover 23 and the casing 21.

In the hot water supplier 20 having the above structure,
For example, relatively low-temperature hot water is fed in according to the arrow 26a, and the low-temperature hot water is heated by the heater 22 in the hot-water supplier 20 to become relatively high-temperature hot water.
It is sent from the hot water supplier 20 according to b. And
This relatively high temperature hot water is sent into the bathtub.

By using the ceramic product according to the present invention as the heater cover 23, thermal shock resistance,
It is possible to obtain the heater cover 23 having excellent mechanical strength, electrical insulation, and heating performance due to the far-infrared effect. Since the heater cover 23 made of a metal is generally used in the past, the heater cover 23 according to the present invention is superior to the one made of such a metal particularly in terms of the electric insulation and the corrosion resistance. Can be said to be

The ceramic product according to the present invention is
It can also be used as a heater cover for a toilet bowl hot water washer. Further, other than the above, the ceramic product according to the present invention can be used as a cover for covering the heat source in order to separate the heat source from the fluid to which heat is applied.

It should be considered that the embodiments disclosed herein are illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

[Brief description of the drawings]

FIG. 1 is a diagram showing a particle size distribution of a zircon powder raw material A in Example 1 of the present invention.

FIG. 2 is a diagram showing a particle size distribution of zircon powder raw material B in Example 1 of the present invention.

FIG. 3 is a diagram showing a particle size distribution of a zircon powder raw material C in Example 1 of the present invention.

FIG. 4 is a diagram showing a particle size distribution of zircon powder raw material D in Example 1 of the present invention.

FIG. 5 is a diagram showing a particle size distribution of a zircon powder raw material E in Example 1 of the present invention.

FIG. 6 is a diagram showing a particle size distribution of a cordierite powder raw material in Example 1 of the present invention.

FIG. 7 is a 1500 × SEM photograph showing the structure of a fired body (ceramics) formed through the wet mixing method.

FIG. 8 is a 1500 × SEM photograph showing the structure of a fired body (ceramics) formed through a dry mixing method.

FIG. 9 is a schematic perspective view showing a structure of a heat insulating insulation bush molded body according to an eighth embodiment.

FIG. 10 is a perspective view and a cross-sectional view schematically showing the configuration of a heat insulating insulation bush molded body according to a ninth embodiment.

FIG. 11 is a cross-sectional view schematically showing a configuration of an automobile exhaust gas oxygen sensor using a heat insulating insulation bush fired body formed by the present method.

FIG. 12 is a sectional view schematically showing an example in which the ceramic product according to the present invention is used as a heater cover.

[Explanation of symbols]

 1,1a Insulated insulation bush firing body

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Chiharu Katsuyama 1370 Onna, Atsugi City, Kanagawa Prefecture, Unisia Jecs Co., Ltd. In-house (72) Inventor Masao Ogawa 1-16-25 Komatsu, Higashiyodogawa-ku, Osaka City Miyagawa Kasei Kogyo Co., Ltd.

Claims (4)

[Claims] 1. A ceramic product comprising 5 to 70% by weight of zircon and 95 to 30% by weight of cordierite. 2. The ceramic product is any one of a heat insulating insulation bush of an oxygen sensor for measuring oxygen concentration in exhaust gas of an automobile, a burner nozzle, an insulator of a heating element or a light emitting element, and a heater cover. And
The ceramic product according to claim 1. 3. A step of mixing zircon powder and cordierite powder to obtain a mixed powder so that zircon is 5 to 70% by weight and cordierite is 95 to 30% by weight, A method of manufacturing a ceramic product, comprising the step of obtaining a molded body by adding a binder to mixed powder and performing injection molding. 4. The average particle size of the zircon powder is 0.2.
The method for manufacturing a ceramic product according to claim 3, wherein the ceramic product has a size of not less than μm and not more than 4.0 μm.