JP2003165782A - Method for manufacturing ceramic porous body - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a simple method for manufacturing a ceramic porous body having reduced variation in diameters of its inclined alignment pores, having low pressure loss when used as a filter, and being lightweight. <P>SOLUTION: The method comprises following processes: a process where a synthetic resin foam body 20 having inclined alignment pores is so formed that pores 23 become successively small from a lower-temperature-side heating face 21 to a higher-temperature-side heating face 22 by heating and pressing both faces of the synthetic resin foam body as providing different temperatures, a process where a carbonized foam having the inclined alignment pores is formed by impregnating the synthetic resin foam body having the inclined alignment pores with a thermosetting resin and by heating the foam body in the atmosphere of an inert gas, and a process where the ceramic porous body having the inclined alignment pores is formed by coating the framework of the carbonized foam having the inclined alignment pores with ceramics by a chemical vapor deposition method. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a ceramic porous body having inclined oriented pores whose pore diameter gradually decreases or increases from one side to the other side of the porous body.

[0002]

2. Description of the Related Art Porous ceramics are used as a sound deadening material, a heat insulating material, a heat resistant filter material such as an exhaust gas filter and the like. Since the performance of the ceramic porous body depends largely on the pore diameter of the bubbles formed inside, it is important to control the pore diameter. Therefore, the following manufacturing method has been studied.

According to the method for producing a porous ceramic body described in JP-A-10-231184 or JP-A-2000-264755, first, a known oxide-based or non-oxide-based ceramic powder, polyvinyl alcohol, etc. are prepared. A binder, water, a surfactant, etc. are added and kneaded to form a gelled ceramics slurry, or a fibrous ceramics slurry in which fibers are further mixed into the slurry to form a chemical reaction inside the slurry, or a slurry. Bubbles with different diameters are generated by blowing gas into it. Next, the air bubbles in the slurry are moved by gravity or centrifugal force to make the air bubbles have an inclined orientation according to their diameter, followed by firing and drying.

However, in order to obtain a ceramics porous body by the above method, it takes a considerable time to move the bubbles in the gelled ceramics slurry so as to be inclined and then to further dry and fire them. However, there is a problem of poor production efficiency. Further, as shown in the sectional view of FIG. 4, in the ceramic porous body 50 manufactured by the above-mentioned conventional method, the inclined orientation of the pores 51 is incomplete, and large pores 52 and small pores 53 coexist. Because there are parts
It was hard to say that the filtration performance was sufficient. In addition, in the conventional method, it is difficult to control the pore diameter, and the pore diameter is 1 μm to 10 μm.
Since it extends over a wide range of 0 μm, it is necessary to make the ceramic porous body have a considerable thickness in order to orient the pores having the pore diameters, and it is difficult to reduce the weight by reducing the thickness of the ceramic porous body.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and it is possible to reduce the variation in the pore diameter in the obliquely oriented pores and to reduce the pressure loss when used as a filter. The present invention provides a method for efficiently producing

[Means for Solving the Problems]

According to the first aspect of the present invention, both sides of a synthetic resin foam having continuous pores are hot-pressed with a temperature difference, and the pore size is gradually reduced from the low temperature side to the high temperature side. A step of forming a resin foam, and a step of impregnating a synthetic resin foam having the above-mentioned inclined orientation pores with a thermosetting resin and carbonizing by heating in an inert gas atmosphere to form a carbonized foam having an inclined orientation pores. And a step of coating the skeleton of the carbonized foam having the tilt-oriented pores with a ceramic by a chemical vapor deposition method to form a ceramic porous body having the tilt-oriented pores.

The invention of claim 2 relates to the method for producing a ceramic porous body according to claim 1, wherein the heating temperature difference between both surfaces of the synthetic resin foam during hot pressing is 25 to 175 ° C.

The invention of claim 3 relates to the method for producing a ceramic porous body according to claim 1 or 2, characterized in that the synthetic resin foam is compressed to 1/2 to 1/20 during hot pressing.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a partially enlarged view of an example of a synthetic resin foam, FIG. 2 is a schematic cross-sectional view of a synthetic resin foam having inclined orientation pores, and FIG. 3 is a schematic diagram of a chemical vapor deposition apparatus.

The present invention is for producing a ceramics porous body from a synthetic resin foam, and comprises a step of forming a synthetic resin foam of inclined orientation pores by hot pressing, a carbonization step, and a chemical vapor deposition step. . The synthetic resin foam used in the present invention is assumed to have continuous pores, and various resin foams such as melamine resin foam, phenol resin foam and urethane resin foam are used. Among them, a urethane foam having continuous pores is preferable, and further, as shown in the partially enlarged view of FIG. 1, a synthetic foam composed of a three-dimensional reticulated skeleton having continuous pores 11 with the cell membrane removed by a known method. Resin foam 10 is preferred.
Particularly, the pore diameter is 227 to 625 μm, the number of cells (the number of pores) is 40 to 110 cells / 25 mm (JIS K 640
2: 1976), density 20-140 kg / m ³ (J
A urethane foam according to IS K 6400: 1997) is preferred. In addition, this synthetic resin foam is processed by cutting or the like into a plate-like body or a block body having a predetermined thickness in consideration of the thickness of the intended ceramic porous body.

In the step of forming a synthetic resin foam having inclined orientation pores by hot pressing, the synthetic resin foam is placed between two pressure plates of a known hot pressing machine and hot pressed. At this time, a temperature difference is provided between the pressure plate on one side and the pressure plate on the other side, whereby both surfaces of the synthetic resin foam are heat-pressed with a temperature difference. The temperature difference between the two surfaces of the synthetic resin foam during the hot pressing is 25 to 175.
C., especially 50 to 100.degree. C. are preferred. The heating temperature of the synthetic resin foam during the hot pressing varies depending on the material of the synthetic resin foam used and the heating and pressing time, but in the case of the urethane foam and when the heating and pressing time is 30 to 300 seconds. Is usually set in the range of 60 to 90 ° C. In addition, the compression of the synthetic resin foam during the hot pressing is 1/2 to 1/20 of the original, and particularly 1
It is preferable to compress it to a thickness of / 3 to 1/15. After completion of the hot pressing for a predetermined time, the synthetic resin foam is cooled to room temperature in that state.

Due to the heating press in which a temperature difference is provided on both sides of the synthetic resin foam, the synthetic resin foam undergoes greater compression deformation on the high heating temperature side than on the low heating temperature side. As shown in the figure, a synthetic resin foam 20 having an inclined orientation in which the pore diameters of the pores 23 are successively reduced from the low temperature side heating surface 21 to the high temperature side heating surface 22 is obtained.

In the carbonization step, the synthetic resin foam 20 having the inclined orientation pores is impregnated with a thermosetting resin, and the synthetic resin foam impregnated with the thermosetting resin is carbonized in an inert gas atmosphere to be inclined. Form a carbonized foam of oriented pores.

The thermosetting resin to be impregnated in the synthetic resin foam 20 having the inclined orientation pores is a phenolic resin,
Furan resins, melamine resins, diallyl phthalate resins, polyimide resins, vinyl ester resins, unsaturated polyester resins, epoxy resins, methacrylic resins and the like. Among them, phenolic resins are preferable.

In the method of impregnating the thermosetting resin, the thermosetting resin is made into a thermosetting resin solution by appropriately using a solvent such as methanol, ethanol, acetone, methyl ethyl ketone, and water, and the thermosetting resin solution is filled. This can be easily carried out by a dipping method or the like in which the synthetic resin foam 20 having the inclined orientation pores is dipped in the container. The thermosetting resin solution used for impregnation has a viscosity of 5 ° C. at 20 ° C. in order to facilitate the impregnation of the synthetic resin foam 20 with the inclined orientation pores.
It is preferable to adjust the amount of the solvent so that the amount becomes 300 mPa · s. Further, the synthetic resin foam taken out from the thermosetting resin solution is compressed with a roll or the like to squeeze out the excess thermosetting resin solution, thereby adjusting the impregnated amount of the thermosetting resin solution in the synthetic resin foam. The desired impregnated synthetic resin foam can be obtained. By this impregnation, the skeleton of the inclined orientation synthetic resin foam 20 is coated with the thermosetting resin solution. The impregnated synthetic resin foam may be dried. An example of the drying temperature at that time is 70 to 210 ° C., and the drying time is 0.1 to 12 hours.

Next, the impregnated synthetic resin foam is heated to cure the thermosetting resin and carbonize both the thermosetting resin and the synthetic resin foam 20 having the graded pores. In this carbonization, the impregnated synthetic resin foam is heat-treated in a temperature range of 800 to 2000 ° C. in an atmosphere of an inert gas such as nitrogen, argon, helium, or xenon to be fired and carbonized, and a carbonized foam having a graded orientation of pores. (Carbonized porous body).

In the chemical vapor deposition step, the skeleton of the carbonized foam having the tilt-oriented pores is coated with ceramics by a chemical vapor deposition method to form a ceramic porous body having the tilt-oriented pores. The chemical vapor deposition method is generally a chemical vapor impregnation method (CV).
I: Chemical vapor infiltra
It is a known method in which a thin film is deposited and deposited on the surface of a target substrate by utilizing a chemical reaction that occurs between each gas in a gas phase.

In this step using the chemical vapor deposition method, as shown in the chemical vapor deposition apparatus 30 of FIG.
First, the carbonized foam 31 is housed in a reaction vessel 33 made of quartz glass installed in. Reference numeral 35 is a vacuum tank, 36 is a temperature controller, 37 is a reservoir tank, 38 is a silicon chloride gas saturator, 39 is a flow meter, 41 is a valve, 4
2 is a gauge. Next, the reaction container 33 is evacuated by a well-known vacuum pump 34, and the reaction container 3
The inside of 3 is set to 666 Pa or less. Then, a series of processes including a mixed raw material gas introduction step, a reaction step, and a re-vacuum step are usually repeated 2000 to 10000 times.

In the step of introducing the mixed source gas, silicon tetrachloride (SiCl ₄ ) and trichlorosilane (SiHC
l ₃ ), dichlorosilane (SiCl ₂ H ₂ ), methyltrichlorosilane (CH ₃ SiCl ₃ ), and the like, and hydrogen and methane in a mixed volume ratio of hydrogen: silicon chloride gas: methane = 70-96: 2-10: 2
The mixed raw material gas was adjusted so as to be ˜20. Also,
When methyltrichlorosilane is used as the silicon chloride gas, the mixing volume ratio is hydrogen: silicon chloride gas = 85-9.
The mixed raw material gas was adjusted to 8: 2 to 15.
The mixed raw material gas is introduced into the reaction vessel 33 whose temperature is 800 to 1300 ° C. At that time, the mixed raw material gas is 9
It is preferable to supply at a pressure of 7.4 to 111.4 kPa. Among the above, the silicon chloride gas used is preferably silicon tetrachloride or methyltrichlorosilane.

In the reaction step, the mixed raw material gas supplied into the reaction vessel 33 is allowed to react for 0.3 to 3 seconds at the above temperature (800 to 1300 ° C.). As a result, silicon carbide (SiC) as ceramics is deposited and formed on the surface of the skeleton (outer surface and internal pore skeleton) of the carbonized foam 31.

In the re-evacuating step, the reaction container 33
More residual unreacted mixed raw material gas and reaction product gas (HCl
Etc.), and the inside of the reaction vessel 33 is evacuated again (66
Up to 6 Pa). After that, the mixed raw material gas introduction step, the reaction step, and the re-vacuum step are repeated until the required number of cycles is reached, thereby depositing and forming on the skeleton (outer surface and internal pore skeleton) surface of the carbonized foam 31. The desired silicon carbide porous body is obtained by forming the above silicon carbide as a thin layer having a thickness of 2 to 20 μm.

[0022]

EXAMPLES Specific examples will be described below. -Example 1 Pore diameter is 200-300 micrometers, continuous porosity is 95%, and the number of cells is 100 cells / 25 mm (JIS K 6402: 19).
76), density 80.9 kg / m ³ (JIS K
6400: 1997) urethane foam (trade name: MF-100, manufactured by Inoac Corporation) having a three-dimensional network skeleton is cut into a length of 150 mm, a width of 150 mm and a thickness of 10 mm, and a synthetic resin foam to be used. did.

The synthetic resin foam is sandwiched between two upper and lower press plates of a heat press (trade name: SA-302-IS, manufactured by Tester Sangyo Co., Ltd.), and an upper press plate is placed at 150.
℃, set the lower pressure plate to 200 ℃, 1 / of the original volume
The synthetic resin foam was hot-pressed to No. 10, held for 180 seconds, and then cooled to room temperature in the pressed state. As a result, a synthetic resin foam having tilted pores with a gradually decreasing pore size from the low-temperature press side in contact with the upper press plate to the high-temperature press side in contact with the lower press plate was obtained.

Further, a thermosetting resin solution is prepared by diluting a phenol resin stock solution (trade name: Phenolite 5900, manufactured by Dainippon Ink and Chemicals, Inc.), which is one type of thermosetting resin, with ethanol to 50% by weight. The synthetic resin foam having the inclined orientation pores is dipped in the thermosetting resin solution, and the impregnated synthetic resin foam taken out from the thermosetting resin solution is squeezed with a roller to give an impregnation amount (basis weight) of 0.1 g / It was set to be cm ³ . After the impregnated foam was dried at 150 ° C. for 1 hour, it was baked at 1000 ° C. for 2 hours in an argon atmosphere (trade name: MTK-11-1530, manufactured by Motoyama Co., Ltd.),
Carbonized to form a carbonized foam.

The carbonized foam is cut into a length of 20 m.
m, width 50 mm, fixed to a quartz glass reaction vessel, housed in an electric furnace, the electric furnace was heated to raise the temperature of the reaction vessel to 1100 ° C. Then, the inside of the reaction vessel was evacuated by a vacuum pump until the pressure became 666 Pa or less. Then, to the reaction vessel, 110: mixed raw material gas of hydrogen: silicon tetrachloride: methane (volume ratio) = 23: 1: 1
Supply 50 ml at a pressure of kPa, react for 1 second, then exhaust the residual unreacted mixed raw material gas and reaction product gas in the reaction vessel and evacuate (666 Pa or less) a series of processes (remaining from the supply of mixed raw material gas) The process of exhausting the unreacted mixed raw material gas and the reaction product gas up to vacuuming) is repeated 4000 times to deposit and deposit ceramics made of silicon carbide on the outer surface and the inner pore skeleton surface of the carbonized foam in a thickness of 4 μm, A ceramic porous body as Example 1 of the present invention was obtained.

Example 2 In Example 1, the compression during hot pressing was set to ⅕ of the initial volume, and the impregnated amount (basis weight) of the thermosetting resin solution was 0.15 g / cm ^3. A ceramic porous body of Example 2 was manufactured by using the same materials and conditions as in Example 1 except for the above.

Example 3 In Example 1, the upper pressing plate of the heating press machine was replaced with 175.
C., the lower pressurizing plate was set to 200.degree. C., the compression at the time of hot pressing was set to 1/5 of the initial volume, and the impregnated amount (basis weight) of the thermosetting resin solution was set to 0. 15 g / c
A ceramic porous body of Example 3 was manufactured using the same materials and conditions as in Example 1 except that m ³ was used.

[0028]

[Comparative Example] -Comparative Example 1 A ceramic porous body of Comparative Example 1 was prepared using the same materials and conditions as in Example 1 except that both the upper pressing platen and the lower pressing platen of the heating press machine were set to 200 ° C. Was manufactured.

Comparative Example 2 In Example 2, the upper press plate and the lower press plate of the heating press were both set to 200 ° C., and the residual unreacted mixed raw material gas and the reaction product gas were discharged from the supply of the mixed raw material gas. With the same materials and conditions as in Example 2 except that a series of processes up to vacuumization in the reaction tube was repeated 8000 times,
A ceramic porous body of Comparative Example 2 was manufactured.

Comparative Example 3 In Example 2, the upper press plate and the lower press plate of the heating press were both set to 200 ° C., and the residual unreacted mixed raw material gas and the reaction product gas were discharged from the supply of the mixed raw material gas. A ceramic porous body of Comparative Example 3 was manufactured by using the same materials and conditions as in Example 2 except that a series of processes up to vacuumization in the reaction tube was repeated 10,000 times.

Comparative Example 4 In 100 g of distilled water, 20 g of methacrylamide which is a monofunctional monomer and N, N 'which is a bifunctional monomer.
-Dissolve 2 g of methylenebisacrylamide to give Serna D305, an ammonium polycarboxylate dispersant.
2.7 g (manufactured by Chukyo Yushi Co., Ltd.) was added, and further, alumina powder (average particle size 0.6 μm) was obtained as ceramic powder particles.
m) 500 g was added and mixed by a wet ball mill for 48 hours in a constant temperature water bath.

Next, the following work was performed in a nitrogen atmosphere. First, at room temperature, 0.2 g of ammonium persulfate as a polymerization initiator and N, N, N'as a catalyst were added to the above mixture.
0.3 g of N'-tetramethylene ethylenediamine and 0.4 g of Newlex R (manufactured by NOF CORPORATION) as a surfactant were added to prepare a ceramic slurry.

Then, a stirring rod having a stirring blade at the lower end was put into the ceramics slurry and rotated at 3000 rpm for 5 minutes so that bubbles were contained in the slurry. This bubble-containing slurry was filled in a polyfluoroethylene cylindrical container having a diameter of 30 mm and a height of 60 mm, and allowed to stand at 25 ° C. for 2 hours for gelation. Then, the gel molding was removed from the molding die.

The gel molded body was placed in an air atmosphere at 25 ° C.
95% R.S. H. (Relative humidity) to 60% R. H. Up to 5% R. H. Each time, drying for 8 days, then degreasing at 700 ° C for 2 days, then 1550 ° C
And was fired for 2 hours to obtain a porous ceramic body of Comparative Example 4.

The sample thickness (mm), pressure loss (kPa), and
Maximum pore size (μm), average pore size (μm), bending strength (MP
a), initial porosity (%) and residual porosity (%) were measured by the following methods. The measurement results are shown in Table 1. In addition,
The thickness (μm) of the deposited and formed silicon carbide layer was measured by a scanning electron microscope. Pressure loss (kPa): Measured according to ASTM F316. Maximum pore size and average pore size (μm): AS for final product
Measured according to TMF 316. Bending strength (MPa): Three-point bending strength test JIS R
Measured according to 1609. The initial porosity and the residual porosity (%) were determined by the following calculation formulas (1) to (3).

[0036] _{P S = P 0 -F · P} 0/100 ...... (1) F = (W Sic -W c) / (ρ sic · V c · P 0/100) · 100 ...... (2) P ₀ = {1- (W _c / V _c / ρ _c )} · 100 (3) However, P _S : Residual porosity (%) P ₀ : Initial porosity (%) F: Carbonized foam (base material) ) Skeleton (outer surface and inner pore skeleton skeleton) shows the proportion of silicon carbide deposited and formed on the surface (%) W _Sic : total weight of deposited silicon carbide and carbonized foam (base material) (g) W _c : Carbonized foam (base material) weight (g) ρ _sic : Density of silicon carbide deposited and formed (3.1 g / c
m ³ Quoted from Iwanami Physics and Chemistry Dictionary 3rd Edition) V _c : Carbonized foam (base material) volume (cm ³ ) ρ _c : Carbonized foam (base material) density (1.8 g / cm ³
(Calculated from JIS R 1634)

[0037]

[Table 1]

[0038]

As shown and described above, according to the manufacturing method of the present invention, a step of hot pressing by providing a temperature difference on both sides of a synthetic resin foam, and carbon impregnation and heating of thermosetting resin Since a ceramic porous body can be obtained by the step of forming a foamed foam and the step of coating the skeleton of the carbonized foam with a ceramic by a chemical vapor deposition method, a ceramics slurry as exemplified in the prior art is kneaded to form a slurry. It is possible to reduce the time for moving bubbles generated therein to perform molding, drying, firing, etc., and it is possible to rationally manufacture a porous ceramic body.

Further, unlike the case where the pores are inclined and oriented according to the pore diameter by gravity or centrifugal force, the variation of the pore diameter in the inclined orientation (mixing of large pores and small pores) can be reduced, and the porous ceramic body can be formed. When used as a filter, the filter performance can be improved.

Further, as is clear from Table 1, the maximum pore diameter can be made smaller than that of the porous ceramic body of the prior art (Comparative Example 4), and the flexural strength is high.
Even if the thickness is reduced, good filter performance and strength can be obtained, and the weight can be reduced.

[Brief description of drawings]

FIG. 1 is a partially enlarged view of an example of a synthetic resin foam.

FIG. 2 is a schematic cross-sectional view of a synthetic resin foam having inclined orientation pores.

FIG. 3 is a schematic diagram of a chemical vapor deposition device.

FIG. 4 is a schematic cross-sectional view of a conventional ceramic porous body.

[Explanation of symbols]

10 synthetic resin foam 20 Synthetic resin foam with inclined orientation pores 21 Low temperature side heating surface 22 High temperature side heating surface 23 pores

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) C23C 16/30 C23C 16/30 (72) Inventor Kaneyasu Nakane 2-chome, Kamino-cho, Atsuta-ku, Nagoya, Aichi Prefecture 70 Address Inoac Corporation Kano Works (72) Inventor Hideo Suzuki 380-5 Horiyamashita, Hadano City, Kanagawa Prefecture Inoac Research Institute Ltd. (72) Inventor Souko Nakajo 380-5, Horiyamashita, Hadano City, Kanagawa F-term in the Inoac Research Institute Co., Ltd. (reference) 4K030 AA03 AA06 AA10 AA17 BA37 CA01 CA07 CA11 DA02 FA10 HA01

Claims (3)

[Claims] 1. A synthetic resin foam having inclined pores in which both sides of a synthetic resin foam having continuous pores are heat-pressed with a temperature difference and the pore diameter is gradually reduced from the low temperature side to the high temperature side. And a step of impregnating the synthetic resin foam of the inclined orientation pores with a thermosetting resin and carbonizing by heating in an inert gas atmosphere to form a carbonized foam of the inclined orientation pores, the inclined orientation A method for producing a ceramic porous body, comprising the step of coating a skeleton of a carbonized foam of pores with a ceramic by a chemical vapor deposition method to form a ceramic porous body having an obliquely oriented pore. 2. The method for producing a ceramic porous body according to claim 1, wherein the heating temperature difference between the both surfaces of the synthetic resin foam during hot pressing is 25 to 175 ° C. 3. A synthetic resin foam is halved at the time of hot pressing.
It compresses to 1/20, The claim 1 or 2 characterized by the above-mentioned.
The method for producing a ceramic porous body according to 1.