JP2003183086A - Porous material and its production method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a porous material which has a sufficient heat resistance without firing at a high temperature, is improved in strength and is excellent in low pressure loss, acid resistance and heat resistance in the case of being used as a filter material, and also to provide a production method therefor. <P>SOLUTION: This porous material is composed by binding aggregate with a calcium silicate-based material and has the Mode fine pore size of 10% or more of an aggregate particle diameter. The method for production thereof comprises adding water of 5-20 wt.% in an outer addition percentage to the aggregate and a binder of a predetermined amount, kneading, forming the moisture-controlled kneaded material, and then hydrothermally synthesizing the formed body at a temperature of 150-300°C for 4-100 hr. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a porous material and a method for producing the same.

[0002]

2. Description of the Related Art A porous material carries a filter for collecting and removing particulate matter in a dust-containing fluid such as diesel engine exhaust gas, and a catalyst component for purifying harmful substances in exhaust gas. It is preferably used in the field of a catalyst carrier or a filter for solid-liquid separation. The above-mentioned porous material is usually a fired body obtained by molding the starting material into a desired shape, drying and firing at high temperature.

However, as interest in environmental problems and energy saving is increasing, efforts to reduce the emission amount of carbon dioxide and energy consumption generated by firing are further required. Therefore, for example, it is conceivable to use a technique for producing a bulk body by low temperature solidification using a hydrothermal synthesis method. However, when a porous material is manufactured using this, the aggregate forming the porous material is locally Since the tissue is not controlled so as to be bonded mechanically, it cannot be used as it is as a porous material for a filter because of its high pressure loss.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the conventional techniques, and an object of the present invention is to control the crystal phase of a bonding portion that bonds aggregates. However, by hydrothermally synthesizing, sufficient heat resistance can be imparted without firing at high temperature, and by adjusting the humidity during molding, the Mode pore size can be increased to the atmospheric pore size and the bonding area can be increased. Therefore, it is an object of the present invention to provide a porous material having improved strength and excellent low pressure loss, acid resistance, and heat resistance when used as a material for a filter, and a method for producing the same.

[0005]

[Means for Solving the Problems] That is, according to the present invention (first invention), a porous material in which aggregates are bonded with a calcium silicate-based material, and a Mod having a particle diameter of 10% or more of the aggregate is used.
Provided is a porous material having an e-pore size. At this time, it is preferable that the joint area for joining the aggregates has a joint area of 20 to 90% of the surface area of the aggregate.

In the present invention, with respect to 100% by weight of aggregate,
It is a porous material containing 2 to 50% by weight of a binder as an outer layer, having an open porosity of 20 to 40% and a Mode pore diameter of 1 to 2.
It is preferably in the range of 0 μm.

Further, in the present invention, the calcium silicate-based material is preferably a CaO—SiO ₂ —H ₂ O-based material, and the main crystal phase is preferably tobermorite or xonotlite.

Further, in the present invention, the calcium silicate-based material is preferably a CaO—SiO ₂ -based material,
It is preferable that the main crystal phase is wollastonite.

Further, according to the present invention (second invention),
5 to 20% by weight of water is added to the aggregate and a predetermined amount of binder by external distribution to form a kneaded product whose humidity has been adjusted, and the obtained formed body is heated to 150 to 300 ° C. for 4 to 100 ° C. There is provided a method for producing a porous material, which comprises performing hydrothermal synthesis for a period of time. At this time, the aggregate is one of Si, Al, and Zr.
It is preferably composed of an oxide containing a seed and a non-oxide,
The binder is preferably Ca (OH) ₂ .

Next, according to the present invention (third invention), an aggregate containing no SiO ₂ and a predetermined amount of Ca / Si
5 to 20 wt% by external distribution to a binder prepared by mixing a Ca source and a Si source so that the ratio becomes 0.9 to 1.1 (molar ratio).
The method for producing a porous material is characterized in that the kneaded product whose moisture has been added and the humidity is adjusted is molded, and the obtained molded product is hydrothermally synthesized at 250 to 300 ° C. for 10 to 100 hours. To be done.

Further, according to the present invention (fourth invention),
The aggregate containing no SiO ₂ and a binder prepared by mixing a Ca source and a Si source so that the Ca / Si ratio of a predetermined amount is 0.9 to 1.1 (molar ratio), are externally distributed to 20% by weight of water is added, a kneaded product whose humidity has been adjusted is molded, and the obtained molded product is hydrothermally synthesized at 250 to 300 ° C. for 10 to 100 hours and then heat-treated to obtain an aggregate. There is provided a method for producing a porous material, characterized in that a crystalline phase of a bonding portion between the phases is transformed into wollastonite. At this time, the heat treatment is preferably performed at 800 ° C. or higher in the atmosphere.

In the present invention (third to fourth inventions), the aggregate is made of one of oxides and non-oxides containing any one of Si, Al and Zr and containing no SiO _2. And the binder is Ca (OH) ₂ /
It is preferably SiO ₂ .

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The porous material of the present invention is a porous material in which aggregates are bonded with a calcium silicate-based material,
It has a Mode pore size of 10% or more of the aggregate particle size. Here, the greatest feature of the porous material of the present invention is that it is produced by hydrothermal synthesis without firing. As a result, the emission of carbon dioxide and energy consumption due to firing can be suppressed, so that it is possible to newly construct a manufacturing process in consideration of the environment and energy saving.

Further, in the porous material of the present invention, it is preferable that the bonding portion for bonding the aggregates has a bond area of 20 to 90% of the surface area of the aggregate.

Further, the porous material of the present invention is an aggregate 10
It is a porous material containing 2 to 50% by weight of a binder as an external component relative to 0% by weight, and has an open porosity of 20 to 40% and a Mod.
e The pore size is preferably in the range of 1 to 20 μm.
Here, the Mode pore size is a pore size distribution obtained by measuring a pore size distribution by a mercury porosimeter, and represents the pore size having the largest amount of pores.

In the porous material of the present invention, the calcium silicate-based material forming the bonding portion that bonds the aggregates is C
is preferably aO-SiO ₂ -H ₂ O-based material, the main crystal phase is preferably a tobermorite (porous material I) or xonotlite (porous material II). In particular,
In the case of zonotolite (porous material II), heat resistance of 800 ° C can be imparted (in the case of tobermorite (porous material I), heat resistance is about 600 ° C), so application of porous material The range can be further expanded.

In addition, the porous material of the present invention (porous material
In III), the calcium silicate material is CaO-SiO ₂
It is preferable that the main crystalline phase is wollastonite whose main crystal phase is phase transition by heat treatment of zonotolite.
Acid resistance can also be imparted.

From the above, the porous material of the present invention has a hydrothermal synthesis temperature of 300 ° C. or lower and a temperature higher than the hydrothermal synthesis temperature (300 to 800) by controlling the crystal phase of the bonding portion.
It has heat resistance of (° C.), realizes atmospheric pore size of Mode, and increases bonding area, and when used as a material for a filter and a filter, can contribute to low pressure loss.

Next, the respective methods for producing the porous material of the present invention will be described. The main manufacturing steps of the porous material of the present invention include weighing, mixing, humidity control, molding and hydrothermal synthesis. Weighing process: Determine the type and composition of the aggregate and binder that are the raw materials of the porous material. Mixing step: The aggregate and the binder, which are the materials of the porous material, are mixed. Humidification step: A predetermined amount of water is added to the mixture of the aggregate and the binder to determine the water content of the molded body during molding. Molding step: molding the resulting mixture. Hydrothermal synthesis step: The obtained molded body is subjected to hydrothermal reaction involving hot water under high temperature and high pressure (in the state of high temperature and high pressure hot water or steam, which has extremely high reactivity) to form a porous material. Hydrothermally synthesize.

Here, the main feature of the method for producing a porous material of the present invention is that when it is produced by hydrothermal synthesis without firing, it is prepared by adding 5 to 20% by weight of water by external distribution. It is to form a molded body using a wet kneaded material (aggregate + binder). As a result, the binder is localized between the aggregates in the molded body, and the localized binder is dissolved in hot water or steam at high temperature and high pressure during hydrothermal synthesis, and the dissolved substance precipitates as a crystalline phase. Then, since the aggregates can be locally bonded to each other, it is possible to contribute to making the Mode pore diameter into the atmospheric pore diameter and improving the strength.

First, a porous material (porous material I) in which the main crystalline phase of the joint between the aggregates is tobermorite is 5% to 20% by weight of the aggregate and the predetermined amount of the binder. Moisture is added to the kneaded product, the humidity of which has been adjusted, and the obtained molded product is hydrothermally synthesized at 150 to 300 ° C. for 4 to 100 hours. At this time, the aggregate is one of Si, Al, and Zr.
Species-containing oxides and non-oxides (eg, alumina [Al
₂ O ₃ ], mullite [3Al ₂ O ₃ .2SiO ₂ ], zirconium oxide [ZrO ₂ ] etc.), and the binder is preferably Ca (OH) ₂ .

Further, a porous material (porous material II) in which the main crystal phase of the joint between the aggregates is zonotolite is Si
And aggregate containing no O _2, a predetermined amount of Ca / Si ratio of 0.
9 to 1.1 (molar ratio) so that Ca source and Si
To the binder prepared by adding the source, 5 to 20% by weight of water is added by external distribution to form a kneaded product whose humidity has been adjusted, and the obtained formed body is heated at 250 to 300 ° C. for 10 to 100 hours. Heat synthesis.

At this time, since the above-mentioned porous material II uses xonotlite as the main crystal phase of the joint between the aggregates, the aggregate species does not have SiO ₂ and the Ca / Si ratio of the binder is 0.
A molded body is molded from the kneaded mixture prepared to 9 to 1.1, and the obtained molded body is heated at 250 to 300 ° C. for 10 to 10.
It is important to carry out hydrothermal synthesis for 100 hours. At this time, the aggregate is one of oxides and non-oxides containing any one of Si, Al, and Zr that does not contain SiO ₂ (for example, alumina [Al ₂ O ₃ ] or zirconium oxide [Z].
rO ₂ ]), and the binder is Ca
It is preferably (OH) ₂ / SiO ₂ .

Furthermore, a porous material (porous material III) in which the main crystalline phase of the joint between the aggregates is wollastonite
Is obtained by subjecting the porous material II to a heat treatment to cause the crystal phase of the joint between the aggregates to undergo a phase transition from zonotolite to wollastonite. At this time, the heat treatment is
It is preferable to perform it in the air at 800 ° C. or higher.

[0025]

EXAMPLES The present invention will be described in more detail based on examples, but the present invention is not limited to these examples. (Examples 1 to 11 and Comparative Examples 1 to 6) Predetermined amounts of the aggregates and binders shown in Table 1 were weighed so that the compounding ratios (weight ratios) shown in Table 1 were obtained (weighing step). Table 1 shows the case where only Ca (OH) ₂ (average particle size 1 μm) is used as the binder and quartz glass (average particle size 1 μm) or quartz (average particle size 1 μm) is used for Ca (OH) _2. The composition (Ca (OH) ₂ / SiO ₂ ) thus blended was used.

After dry-mixing the weighed aggregate and binder, the resulting dry-mixed powder was sprayed with distilled water.
Was added as shown in (1) and further mixed (mixing / humidification step).

The obtained kneaded product is pressed by a press molding machine.
Press molding was performed at a molding pressure of 5.0 × 10 ⁷ Pa (500 kgf / cm ² ) (molding process).

Next, distilled water is put into the autoclave, a setter is set therein, and the above-mentioned molded body is set. Further, the autoclave was placed in a dryer and heated to the temperature of the hydrothermal treatment conditions shown in Table 1, and then the above-mentioned molded body was hydrothermally treated under the hydrothermal treatment conditions shown in Table 1 (hydrothermal synthesis step).

After the hydrothermal treatment, it was allowed to cool, it was confirmed that the container was sufficiently cooled, the autoclave was opened, and the sample was taken out. The following measurements were performed on each of the obtained samples, and the results are shown in Table 1. Open porosity: Measured by Archimedes method. Mode Pore size: Measured by mercury porosimetry. Bond part crystal phase (main phase): measured by powder X-ray diffraction method. Bonding area: From the results obtained by two-dimensional SEM observation, the area of the bonding portion that bonds the aggregates to 100 of the aggregate surface.
Shown as a fraction. Bonded area = (sum of areas where each aggregate contacts the bonded part) /
(Sum of aggregate surface area) x 100

[0030]

[Table 1]

Example 1 (see FIG. 2), Example 2, Example 3 (see FIG. 3), Example 4 (see FIG. 1) and Example 6
As shown in Table 1, the aggregate is mullite, and the binder is Ca (OH) ₂ (average particle size 1 μm).
20% by weight of water was added, and the kneaded product whose humidity was adjusted was press-molded, and the obtained molded body was heated at 150 to 300 ° C.
By performing hydrothermal synthesis for 100 hours, it is possible to locally bond the aggregates by the precipitated crystal phase,
It was confirmed that the Mode pore diameter was changed to the atmospheric pore diameter and the strength was improved.

On the other hand, in Comparative Example 1 (see FIG. 4), since the water content of the molded body was less than 5% by weight, it was confirmed that the strength of the porous material was decreased due to the decrease in the average bonding area.

Further, in Comparative Example 6 (see FIG. 5), since the binder exceeds 50 wt% in the external distribution, it was not possible to obtain sufficient open porosity and Mode pore size.

Further, in Comparative Examples 2 to 5, the porous materials could not be obtained because they did not harden even after the hydrothermal treatment.
This is because the hydrothermal treatment temperature was insufficient at less than 150 ° C. (Comparative Example 2), the water content of the molded body was too large (Comparative Example 3), and the retention time during hydrothermal treatment was insufficient (Comparison). Example 4), insufficient binder (Comparative Example 5)
Is thought to be the cause.

In Example 5, as shown in Table 1, the aggregate was alumina containing no SiO ₂ and the binder was Ca /
Ca (OH) whose Si ratio is 0.9 to 1.1 (molar ratio)
₂ / SiO ₂ (average particle size 1 μm), 5-20% by weight of water was added externally, and the humidity-controlled kneaded product was press-molded to obtain a molded product at 250-300 ° C. 10 to 10
By performing hydrothermal synthesis for 0 hours, the main crystal phase of the joint between the aggregates can be zonotolite, so Mo
In addition to increasing the de pore size to the atmospheric size and improving the strength,
It was possible to impart heat resistance of 00 ° C.

On the other hand, in Examples 7 to 11, zonotolite could not be used as the main crystal phase of the joint between the aggregates, and therefore heat resistance at 800 ° C. could not be imparted. This is because the aggregate (mullite) contained SiO ₂ (Example 7), the holding time during hydrothermal treatment was insufficient (Example 8), and the hydrothermal treatment temperature was too low (Example 9). ), The Ca / Si ratio of the binder is not appropriate (Examples 10 to 11).

(Heat Resistance Test) Samples of Example 5 and Example 7 were respectively subjected to 800 ° C. for 2 hours in the atmosphere (heating rate 2
A heat resistance test at 00 ° C./h) was performed. The results are shown in Table 2.

[0038]

[Table 2]

In Example 5, as shown in FIG. 6, by using zonotolite as the main crystal phase of the joint between the aggregates, no structural change occurred before and after the heat resistance test.
On the other hand, in Example 7, as shown in FIG. 7, since the main crystal phase of the joint between the aggregates was not zonotolite, the microstructural change occurred before and after the heat resistance test.

Example 8 The sample of Example 5 was heat-treated in air at 800 ° C. for 2 hours (temperature rising / falling rate of 200 ° C./h), and the heat-treated product thus obtained was analyzed by powder X-ray diffraction to measure It was confirmed that the main crystal phase of the joint part of was wollastonite. Next, the sample of Example 5, the obtained heat-treated product (Example 12), and the acid resistance test of Example 7 were respectively performed. The results are shown in Table 3. The acid resistance test is a measurement of the rate of change in weight after immersion in a 2% by weight citric acid solution for 16 hours. Weight change rate = {(weight before test)-(weight after test)} /
(Weight before test) x 100

[0041]

[Table 3]

As shown in Table 3, it was confirmed that Example 5 has not only excellent heat resistance as compared with Example 7, but also excellent acid resistance. In addition, it was confirmed that Example 12 is not only superior in acid resistance as compared with Example 5, but also has the heat resistance of Example 5.

[0043]

[Effects of the Invention] As described above, in the porous material and the method for producing the same of the present invention, firing is performed at a high temperature by hydrothermally synthesizing while controlling the crystal phase of the joint portion that bonds the aggregates. In addition to being able to impart sufficient heat resistance, it is possible to realize the improvement of strength and the material for the filter because it is possible to realize the atmospheric pore diameter of the Mode pore diameter and increase the bonding area by the treatment such as humidity control during molding. When used as, it is also excellent in low pressure loss, acid resistance, and heat resistance. Further, the production method of the present invention can suppress carbon dioxide emissions and energy consumption due to firing,
It is possible to build a new manufacturing process that considers the environment and energy conservation.

[Brief description of drawings]

FIG. 1 is an SEM photograph showing a microstructure of a porous material obtained in Example 4 of the present invention.

FIG. 2 is an SEM photograph showing the microstructure of the porous material obtained in Example 1 of the present invention.

FIG. 3 is an SEM photograph showing the microstructure of the porous material obtained in Example 3 of the present invention.

FIG. 4 is an SEM photograph showing the microstructure of the porous material obtained in Comparative Example 1 of the present invention.

FIG. 5 is a SEM photograph showing the microstructure of the porous material obtained in Comparative Example 6 of the present invention.

FIG. 6 shows the results of a heat resistance test of the porous material obtained in Example 5 of the present invention, (a) before the heat resistance test,
(B) is an SEM photograph showing the microstructure after the heat resistance test.

FIG. 7 shows the results of heat resistance test of the porous material obtained in Example 7 of the present invention, (a) before heat resistance test,
(B) is an SEM photograph showing the microstructure after the heat resistance test.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) B01J 32/00 B01J 32/00 F01N 3/02 301 F01N 3/02 301B 3/28 3/28 Q F term (Reference) 3G090 AA02 3G091 BA39 GA16 GB10X GB17X 4D019 AA01 BA05 BB06 CB04 CB06 4G019 FA15 GA02 GA04 LA03 LD02 4G069 AA01 AA08 BA02A BA02B BA13A BA13B BB04A BB04B BC09A BC09B DA05 EC22X EC22X

Claims (17)

[Claims] 1. A Modem material which is a porous material in which aggregates are bonded with a calcium silicate-based material and has a particle size of 10% or more of the aggregate particle size.
A porous material having a pore size. 2. The porous material according to claim 1, wherein the bonding portion for bonding the aggregates has a bond area of 20 to 90% of the surface area of the aggregate. 3. A porous material containing 2 to 50% by weight of a binder as an external component relative to 100% by weight of an aggregate, and having an open porosity of 20 to 40% and a mode pore diameter of 1 to 20 μm. The porous material according to claim 1 or 2, wherein 4. The calcium silicate material is CaO--Si.
The porous material according to claim 1 which is O ₂ -H ₂ O-based material. 5. The main crystal phase of the CaO—SiO ₂ —H ₂ O-based material is tobermorite or xonotlite.
The porous material according to. 6. The calcium silicate material is CaO--Si.
The porous material according to any one of claims 1 to 3, which is an O ₂ -based material. 7. The porous material according to claim 6, wherein the main crystal phase of the CaO—SiO ₂ material is wollastonite. 8. The aggregate and the predetermined amount of the bonding material are externally distributed by 5-2.
0% by weight of water was added to form a kneaded product whose humidity was adjusted, and the obtained molded product was heated at 150 to 300 ° C. for 4 to 100 ° C.
A method for producing a porous material, which comprises hydrothermally synthesizing for a period of time. 9. The aggregate is one of Si, Al, and Zr.
The method for producing a porous material according to claim 8, comprising an oxide and a non-oxide containing a seed. 10. The method for producing a porous material according to claim 8, wherein the binder is Ca (OH) ₂ . 11. An aggregate containing no SiO ₂ and a binder prepared by mixing a Ca source and a Si source so that a predetermined amount of Ca / Si ratio is 0.9 to 1.1 (molar ratio). 5 out
To 20% by weight of water is added to form a kneaded product whose humidity has been adjusted, and the obtained molded product is heated at 250 to 300 ° C. for 10 to 1
A method for producing a porous material, which comprises performing hydrothermal synthesis for 00 hours. 12. The method for producing a porous material according to claim 11, wherein the aggregate is made of an oxide and a non-oxide containing any one of Si, Al and Zr and containing no SiO ₂ . 13. The method for producing a porous material according to claim 11, wherein the binder is Ca (OH) ₂ / SiO ₂ . 14. An aggregate containing no SiO ₂ and a binder prepared by mixing a Ca source and a Si source so that a predetermined amount of Ca / Si ratio is 0.9 to 1.1 (molar ratio), 5 out
To 20% by weight of water is added to form a kneaded product whose humidity has been adjusted, and the obtained molded product is heated at 250 to 300 ° C. for 10 to 1
A method for producing a porous material, characterized in that a crystal phase of a joint portion between aggregates is phase-transformed to wollastonite by hydrothermally synthesizing for 00 hours and then heat treatment. 15. The method for producing a porous material according to claim 14, wherein the heat treatment is performed in the air at 800 ° C. or higher. 16. The production of a porous material according to claim 14 or 15, wherein the aggregate is made of one of oxides and non-oxides containing any one of Si, Al and Zr and containing no SiO _2. Method. 17. The method for producing a porous material according to claim 14, wherein the binder is Ca (OH) ₂ / SiO ₂ .