JP2001220246A - Honeycomb molding product and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a honeycomb molding product mass-producible without impairing qualities of product, having thin thickness of partition and to provide a method for producing the same. SOLUTION: This honeycomb molding product is obtained by extrusion molding a mixture of raw material powder and a molding binder. The honeycomb molding product contains no open pores and the molding binder is constituted of a thermoplastic material in a molten state at a molding temperature. This method for producing the honeycomb molding product comprises heating the mixture of the raw material powder and the molding binder to the molding temperature, melting the molding binder, extrusion molding the mixture and cooling and solidifying the molded material.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a honeycomb extruded product used as a catalyst carrier for purifying automobile exhaust gas and a method for producing the same.

[0002]

2. Description of the Related Art In recent years, due to consideration of environmental issues, exhaust gas regulations have tended to be strengthened year by year, and in order to cope with this, improvement in purification performance of exhaust gas purification catalysts has been required. On the other hand, from the aspect of engine development, fuel economy and high output have been markedly emphasized.
Exhaust gas purification catalysts are also required to reduce pressure loss.

[0003] In order to solve such a problem, the thickness of the partition walls of the honeycomb structure is reduced to increase the air permeability and reduce the pressure loss, and also reduce the weight of the exhaust gas purification catalyst itself to reduce the heat capacity. In addition, there is a growing movement to improve purification performance during warm-up. Specifically, conventionally,
While 6 mil products with a partition wall thickness of 150 μm were mainstream, 2 mil products with a partition wall thickness of 50 μm are now becoming mainstream. Note that the honeycomb structure refers to a structure in which a large number of cells are partitioned by partition walls.

The honeycomb structure is usually formed by mixing raw material powders such as ceramic powders and metal powders with a binder and the like, and is formed by extrusion using a die having a grid-like slit. Next, it is manufactured by drying and firing. Conventionally, a water-soluble thermosetting methylcellulose-based binder has been used as a binder used for extrusion molding of a honeycomb structure.

However, since the width of the lattice-shaped slits formed in the die is also reduced with the thinning of the partition walls, the flow of the fluid into the die can be rapidly performed in forming the honeycomb structure. It is necessary to use a binder having high properties. In addition, as the partition walls become thinner, the strength of the molded product that has just come out of the die decreases, and the molded product is easily deformed by its own weight. Must be used.

Therefore, it is necessary to form a honeycomb structure using a clay having high hardness and excellent shape retention, or to form a honeycomb structure using a clay having low hardness and high fluidity. I have been.

[0007]

Problems to be Solved by the Invention However, kneaded clay having high hardness is poor in fluidity, so that it does not easily flow into a die, and it is not possible to improve production efficiency, and molding pressure is increased. During stacking, there was a problem that the base was deformed or worn.

In the case of using a clay having a low hardness,
In order to give strength to the molded product coming out of the die, it is necessary to solidify the binder by thermal drying by dielectric drying.
However, the transfer to the dielectric dryer is performed while applying an air current from below the molded product so that the molded product is not deformed by its own weight. There was a problem.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a honeycomb formed body having a thin partition wall and a method of manufacturing the same, which can be mass-produced without impairing product quality. It is in.

[0010]

That is, according to the present invention, there is provided a honeycomb formed body formed by extruding a mixture of a raw material powder and a formed binder, which does not have open pores and has a formed binder. Provided is a honeycomb formed body made of a thermoplastic material that is in a molten state at a temperature.

In the above-mentioned honeycomb formed body, the forming binder is preferably insoluble in water, and is preferably a wax, a thermoplastic resin, or a mixture thereof. At this time, the mixing ratio of the thermoplastic resin in the molding binder is 35 to 80% by weight, more preferably 4 to 80% by weight.
It is preferably 0 to 70 wt%, more preferably 45 to 60 wt%, and the raw material powder used may be a ceramic powder such as cordierite or a metal powder.

The above-mentioned honeycomb formed body may be used as a catalyst carrier for removing harmful substances and dust from automobile exhaust gas.

Further, according to the present invention, there is provided the above-mentioned method for producing a honeycomb formed body, wherein a mixture of a raw material powder and a forming binder is extruded, wherein the mixture is heated to a forming temperature to melt the forming binder. Thereafter, there is provided a method for producing a honeycomb formed body, which is extruded and then cooled and solidified.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, a honeycomb formed body is produced by extruding a mixture of a raw material powder and a forming binder, and the forming binder includes a thermoplastic material which is in a molten state at a forming temperature. Is used. The thermoplastic material is melted by applying heat, but the viscosity of the molding binder can be freely changed depending on the temperature condition. Therefore, by selecting an appropriate temperature condition, a desired fluidity can be obtained, and the production efficiency can be improved. The honeycomb molded body can be mass-produced without deteriorating the quality.

Further, since the molten thermoplastic material is cooled and solidified, the molded product coming out of the die is immediately quenched with cold water, cold air, etc., so that the molded product can be easily deformed by its own weight before being deformed. The solidified binder can secure the shape retention of the molded article.

In the present invention, since a water-insoluble molding binder is used, it is not necessary to dry the molded body. In the case of extrusion molding using a water-soluble binder, a mixture of a raw material powder and a molding binder (hereinafter, referred to as a raw material mixture).
The air bubbles inside must be removed by vacuum defoaming.However, while hard soil generated by local drying during vacuum defoaming causes clogging of the die, a water-insoluble molding binder is used. In this case, since drying does not occur, clogging of the base does not occur, and the production efficiency can be improved from this viewpoint. When a water-insoluble molding binder is used, the vacuum removal method is not essential.

In the present invention, specifically, it is preferable to use a wax or a thermoplastic resin as the water-insoluble molding binder, and as the wax, paraffin wax, microcrystalline wax, or the like is suitably used. As the plastic resin, general thermoplastic resins such as EVA, polyethylene, polystyrene, liquid crystal polymer and engineering plastic are preferably used. In the present invention, the above-mentioned molding binder is
A single species alone may be used, or two or more species may be used in combination. Further, auxiliary agents such as a coupling agent, a lubricant and a dispersant may be added to the above-mentioned molding binder and used.

In the present invention, when a mixture of wax and a thermoplastic resin is used as the molding binder, the mixing ratio of the thermoplastic resin in the molding binder is 35 to 80 wt%, more preferably 40 to 70 watts.
t%, more preferably 45 to 60 wt%.

This is because the amount of the thermoplastic resin added to the molding binder affects the shape retention and molding pressure during molding, the amount of expansion during degreasing / firing, the amount of cracks generated, and the adhesiveness with the tomato. Because there is. Incidentally, the molding binder, as the addition amount of the thermoplastic resin increases,
This has the effect of improving the shape retention during molding, increasing the molding pressure, and reducing the amount of expansion and the amount of defects during degreasing and firing.

From the above, in the present invention, the upper limit of the mixing ratio of the thermoplastic resin of the molding binder is 80 wt%, more preferably 70 wt%, and further preferably 60 wt%.
%, It is possible to suppress the rise in the molding pressure while maintaining the shape retention, so that the honeycomb molded body having a small wall thickness and a large cell density can be formed without deforming the die for extrusion molding. , Can be suitably molded. Also,
If the mixing ratio of the thermoplastic resin of the molding binder is excessively increased, the temperature of the molded article increases, and the thermal stress increases.
Handling properties also deteriorate.

In the present invention, the lower limit of the mixing ratio of the thermoplastic resin in the molding binder is 35 wt%, more preferably 40 wt%, and even more preferably 45 wt%. It is possible to reduce the amount of cracks generated and the adhesiveness with the tochi.

In the present invention, a mixture of the raw material powder and the molding binder is extruded. The amount of the molding binder to be added in the mixture varies depending on the type of the molding binder used, and is an amount capable of obtaining a desired fluidity. Is added.

In the present invention, ceramic powder or metal powder is preferably used as a raw material powder used for manufacturing a honeycomb formed body. In the case of ceramic powder, oxide such as cordierite, alumina, mullite, silicon nitride, Ceramic powder which is a nitride such as silicon carbide or aluminum nitride can be used. F for metal powder
Powders of e, Cr, Ni, Al and the like can be used.

In the present invention, the honeycomb formed body is manufactured by extrusion molding. However, the kneading equipment is not particularly limited as long as it can perform heating and pressurization. A kneading extruder or the like can be used. The molding apparatus used in the present invention is not particularly limited as long as it can be heated and pressurized and has an extrusion function, and a plunger type extruder, a clay extruder, an injection molding machine, a single-screw continuous extruder,
A twin-screw continuous kneader or the like can be used. Further, in the present invention, kneading and molding can be simultaneously performed at the same time by a twin-screw continuous kneading extruder or the like capable of simultaneously performing kneading and molding. In continuous molding, it is necessary to atomize the binder, but as the atomization method, for example, spray dryer,
Freeze grinding can be applied. There is no particular limitation on the heating means of the molding apparatus. For example, the heating means may be heated by a heater or may be heated by circulation of a heat medium using oil or the like.

The honeycomb forming binder is appropriately selected depending on the cell structure of the honeycomb. The thinner the wall,
In addition, as the cell density decreases, the shape retention strength of the molded body is required, and therefore, the ratio of the amount of the thermoplastic resin added to the wax increases. For example, in the case of a wall thickness of 12 mils and a cell density of 300 cells / inch ² , it can be molded with wax alone, but a wall thickness of 4 to 1 mil and a cell density of 500 to 500 mil.
In the case of 1200 cells / inch ² , the mixing ratio of the thermoplastic resin in the mixed binder of the wax and the thermoplastic resin is 35 to 80 wt%, preferably 40 to 70 wt%.
More preferably, the range is 45 to 60 wt%.
Naturally, a good honeycomb can be formed even with 100 wt% of the thermoplastic resin.

The forming temperature of the honeycomb formed body, that is, the temperature at the time of forming the raw material mixture itself is determined depending on the type of the forming binder selected. For example, wax alone or a mixture of wax and EVA is used. If so, the temperature is about 60C to 100C. In the case of high melting point thermoplastic resin, polyethylene is about 280 ° C.
The temperature is about 350 ° C. for a liquid crystal polymer. In consideration of the handling and thermal stress of the molded body, it is more advantageous to use a binder having a low melting point. The kneading and molding temperatures need to be at temperatures that do not degrade the binder. The viscosity of the raw material mixture is determined by the type and amount of the binder selected and the molding conditions including the molding temperature and pressure, and is in the range where the honeycomb can be molded. The addition amount of the binder can be appropriately set depending on the type of the raw material powder.

In the present invention, the molded product coming out of the die is cooled and solidified to prevent the molded product from being deformed. However, the cooling method is not particularly limited. For example, a method such as air cooling or water cooling by spraying is used. Can be used. Alternatively, the molded product may be dropped into water and rapidly cooled. Incidentally, depending on the molding temperature, forcible cooling is not particularly necessary. Also, usually,
Although the molded product is extruded in the horizontal direction from the extruder, the molded product may be extruded downward by a vertical molding machine.

The cooling temperature may be a temperature at which the molding binder is solidified. From the viewpoint of reducing the stress during cooling, the difference between the molding temperature and the cooling temperature is preferably small, and the cooling rate is preferably low. .

In the present invention, the cross-sectional shape of the cells of the honeycomb formed body is not particularly limited, and may be a polygon such as a triangle, a quadrangle, a hexagon, or a circle. Further, the cell density may be 300 to 2000 cells / inch ² .

The firing of the molded body is performed in a low temperature range.
In consideration of the scattering curve of the molding binder, conditions are selected so as not to cause cell depletion, and in a high temperature region, conditions capable of imparting target characteristics such as porosity and coefficient of thermal expansion are selected. The degreasing and firing of the honeycomb formed body may be appropriately selected from the group consisting of air, an inert atmosphere, and a vacuum depending on the type of the raw material powder. For example, in the case of cordierite powder which is an oxide, after degreasing in the air, baking is performed in the air, and usually degreasing and firing are simultaneously performed in a single furnace or a continuous furnace such as a tunnel.

When the honeycomb structure manufactured as described above is used as a catalyst for automobile exhaust gas, a γ-alumina layer is formed on the inner surface of the cell passage, and a catalyst component is contained in pores of the γ-alumina layer. After supporting a noble metal component such as platinum, rhodium, and vanadium, the catalyst is baked at a temperature of about 600 ° C.

[0032]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples.

Examples 1 to 6 Using a cordierite powder as a raw material powder and a wax as a molding binder, a honeycomb formed body having a circular end face shape and a square cross section of a cell was manufactured. The cell density and the thickness of the partition walls of the honeycomb formed article were set to the values shown in Table 2.

First, a molding binder having an average particle size of 100 μm is added to cordierite powder so that the content of the molding binder in 100% by weight of the raw material mixture becomes 22% by weight, and the mixture is put into a continuous kneading extrusion molding apparatus. , Kneading and molding. The molding temperature was set at 60 ° C. in consideration of the material and the structure of the cell. The weight composition ratio of the molding binder is 9
0, microcrystalline wax (manufactured by Nippon Seiwa Co., Ltd.) 6, and oleic acid (manufactured by Katayama Chemical Co., Ltd.) 4.

Next, the molded body coming out of the die was cooled by standing to cool. With respect to the obtained honeycomb formed body, the roundness of the cell shape and the outer diameter was visually examined. Table 2 shows the results. Next, the above-mentioned formed body was fired at 1430 ° C. for 3 hours to obtain a honeycomb structure.

(Examples 7 to 12) Wax and EVA
The use of a molding binder mixed at a weight ratio of 1: 1 and
Except that 75 ° C was used as the molding temperature.
The same honeycomb formed body as in Examples 1 to 6 was manufactured as in Examples 1 to 6.
It was manufactured by the method described above. The weight composition ratio of the molding binder is as follows:
Paraffin wax 45 (manufactured by Nippon Seiwa Co., Ltd.)
Crocrystallin wax (Nippon Seiro Co., Ltd.) 3,
EVA (Mitsui DuPont Chemical Co., Ltd.) 48, I
Inic acid (manufactured by Katayama Chemical Co., Ltd.) 4 was used. Honeycomb molding
The cell density of the body and the thickness of the partition wall were set to the values shown in Table 2.
Also, measure the viscosity of the molding binder with a flow tester
did. The measurement conditions were as follows: temperature 60 ° C, 65 ° C, 70 ° C, 7 ° C.
5 ° C., capillary diameter 1 mm, load 100 and 200
kgf / cm ^TwoAnd Table 1 shows the results. Obtained c
The roundness of the cell shape and outer diameter of the honeycomb formed body was measured.
It investigated similarly to Examples 1-6. Table 2 shows the results. next,
The above molded body was fired under the same conditions as in Examples 1 to 6.
A honeycomb structure was obtained.

[0037]

[Table 1]

(Examples 13 to 18) Except that EVA was used as the molding binder and 110 ° C was employed as the molding temperature, the same honeycomb molded bodies as Examples 1 to 6 were used. It was manufactured in the same manner as described above. The weight composition ratio of the molding binder was 100 EVA (manufactured by DuPont-Mitsui Chemicals) and 5 oleic acid (manufactured by Katayama Chemical Co., Ltd.). The cell density and the thickness of the partition walls of the honeycomb formed article were set to the values shown in Table 2. With respect to the obtained honeycomb formed body, the roundness of the cell shape and the outer diameter was examined in the same manner as in Examples 1 to 6. Table 2 shows the results. Next, the above-described molded body was fired under the same conditions as in Examples 1 to 6 to obtain a honeycomb structure.

(Comparative Examples 1 to 6) Using cordierite powder as a raw material powder and methylcellulose (manufactured by Shin-Etsu Chemical Co., Ltd.) as a molding binder, a honeycomb having a circular end face shape and a rectangular cell cross section is used. A molded body was manufactured. The cell density and the thickness of the partition walls of the honeycomb formed article were set to the values shown in Table 2.

First, a molding binder and water are added to cordierite powder so that the content of the molding binder in 100% by weight of the raw material mixture is 7% by weight and the content of water is 30% by weight, and the mixture is continuously kneaded. Into the extrusion machine,
Kneading and molding were performed. The molding temperature was 20 ° C.

Next, the molded product coming out of the die was dried. With respect to the obtained honeycomb formed body, the roundness of the cell shape and the outer diameter was examined in the same manner as in Examples 1 to 6. Table 2 shows the results
Shown in Next, the above-described molded body was fired under the same conditions as in Examples 1 to 6 to obtain a honeycomb structure.

[0042]

[Table 2]

As shown in Table 2, unlike the comparative example, the example does not include a drying step, and has a dimensional accuracy equal to or higher than that of the comparative example despite the small number of steps in the manufacturing process. It can be seen that a molded article could be manufactured. Further, no difference was observed between the thermal expansion coefficient and the open porosity of the honeycomb sintered body between the example and the comparative example.

(Examples 19 to 25, Comparative Example 7) Using a cordierite powder as a raw material powder and a wax as a molding binder, a honeycomb formed body having a circular end face shape and a square cross-sectional cell shape was obtained. Manufactured. The honeycomb formed body had a cell density of 600 cells / inch ² and a wall thickness of 2.0 mil.

[0045] First, the cordierite powder, as the content of the molding binder in the raw material mixture 100 weight percent is 22% by weight, was added forming binder having an average particle size of 100 [mu] m, pressure 1.0 × 10 ⁵ Heat kneading with a pressure kneader of Pa, after cooling, crushed with a jaw crusher,
Using a single-screw extruder, each of the honeycomb formed bodies was formed at a forming temperature and a forming pressure shown in Table 3. The above-mentioned molding binder was a mixture of wax and EVA (manufactured by Mitsui DuPont Chemical Co., Ltd.), and was used by mixing with EVA as shown in Table 3. The weight composition ratio of the above wax was paraffin wax (manufactured by Nippon Seiwa Co., Ltd.) 90, microcrystalline wax (manufactured by Nippon Seiwa Co., Ltd.) 6, and oleic acid (manufactured by Katayama Chemical Co., Ltd.) 4.

Next, after the molded body coming out of the die was allowed to cool by cooling, the obtained honeycomb molded body was evaluated. Table 3 shows the results.

[0047]

[Table 3]

Further, the above-mentioned honeycomb formed body is kept at room temperature to 5
50 ° C / h to 00 ° C, 100 to 500 to 1200 ° C
C./h, the temperature was raised from 1200 to 1430 ° C. at 50 ° C./h, and then maintained at 1430 ° C. for 3 hours to degrease
Firing was performed to obtain a honeycomb structure. The obtained honeycomb structure was evaluated for its expansion coefficient, fired cracking, and adhesion to tochi. Table 4 shows the results.

[0049]

[Table 4]

From the results in Table 3, Examples 19 to 25
Mixing ratio of thermoplastic resin of molding binder is 35-80w
By setting the content within the range of t%, it is possible to suppress an increase in molding pressure while maintaining shape retention during molding.
A honeycomb formed body having a small wall thickness and a large cell density could be suitably formed. In addition, from the results in Table 4, Examples 19 to 25 were able to reduce the amount of expansion, the amount of cracks generated, and the adhesion to tochi during degreasing and firing.

[0051]

According to the present invention, a honeycomb formed body having a thin partition wall of 25 to 100 μm can be efficiently mass-produced without generating a crack or deforming a die for extrusion molding. . Further, in the present invention, by using a water-insoluble molding binder,
Drying of the molded body is not required, and clogging of the die due to vacuum defoaming can be eliminated. Further, degreasing is facilitated, which can further contribute to improvement of production efficiency.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) B22F 3/20 C04B 35/00 108 B28B 3/26 B01D 53/36 ZABC C04B 35/195 C04B 35/16 A F-term (reference) 4D048 AA02 AA06 AA14 AA18 BA10X BA10Y BB02 4G030 AA07 AA36 AA37 BA34 CA10 GA14 PA21 4G054 AA05 AA06 AA11 AA19 AB09 AC00 BD19 DA03 4G069 AA01 AA08 BA13A BA13B BA22ABA18 EB18 BA22ABA18BA18 BA22ABAEBA22 CA08 CA32 HA08 KA22

Claims (15)

[Claims] 1. A honeycomb formed body obtained by extruding a mixture of a raw material powder and a forming binder, wherein the forming binder has no open pores and is formed of a thermoplastic material which is in a molten state at a forming temperature. A honeycomb formed body characterized by being formed. 2. The honeycomb formed article according to claim 1, wherein the formed binder is water-insoluble. 3. The honeycomb formed article according to claim 2, wherein the forming binder is a wax. 4. The honeycomb formed article according to claim 2, wherein the forming binder is a thermoplastic resin. 5. The honeycomb formed article according to claim 2, wherein the forming binder is a mixture of a wax and a thermoplastic resin. 6. The honeycomb formed article according to claim 5, wherein a mixing ratio of the thermoplastic resin in the forming binder is 35 to 80% by weight. 7. The honeycomb formed article according to claim 5, wherein a mixing ratio of the thermoplastic resin in the forming binder is 40 to 70 wt%. 8. The honeycomb formed article according to claim 5, wherein the mixing ratio of the thermoplastic resin in the forming binder is 45 to 60 wt%. 9. The honeycomb formed body according to claim 1, wherein the raw material powder is a ceramic powder. 10. The honeycomb formed article according to claim 9, wherein the raw material powder is cordierite. 11. The raw material powder is a metal powder.
The honeycomb formed article according to any one of Items 1 to 8, wherein: 12. The honeycomb formed article according to claim 1, wherein the thickness of the partition wall is 25 to 100 μm. 13. The honeycomb formed article according to any one of claims 1 to 12, which is used as a catalyst carrier for purifying automobile exhaust gas. 14. The method for producing a honeycomb formed body according to claim 1, wherein a mixture of the raw material powder and the forming binder is extruded, wherein the mixture is heated to a forming temperature to form the mixture. A method for manufacturing a honeycomb formed body, comprising: extruding a formed binder after melting the formed binder; and cooling and solidifying the formed product. 15. The method for producing a honeycomb formed article according to claim 14, wherein the extrusion is a continuous kneading extrusion method.