JP2012045926A - Green mold - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a green compact suitable for manufacturing a honeycomb structural body with high productivity in which a partitioning wall of a sealing part and through-holes is fully sintered.SOLUTION: This green compact 100 is provided with a honeycomb-shape columnar body 70 having a plurality of roughly parallel through-holes 70a, and a sealing material 70b which seals one end of the through-holes 70a. The columnar body 70 has a first end and a second end roughly perpendicular to the through-holes 70a, some of the through-holes 70a are sealed by the sealing material 70b at the first end and are open at the second end, and the other through-holes 70a are sealed by the sealing material 70b at the second end and open at the first end. The sealing material 70b contains ceramic, and the columnar body 70 contains ceramic raw material powder, and the ceramic is aluminum titanate-based ceramic and/or cordierite-based ceramic, and the sealing material shrinkage ratio during sintering is the 80 to 100% of shrinkage rate of the partitioning wall.

Description

  The present invention relates to a green molded body.

  2. Description of the Related Art Conventionally, a honeycomb made of porous ceramics is used as a ceramic filter (DPF: Diesel Particulate Filter) for collecting fine particles such as carbon particles contained in exhaust gas discharged from an internal combustion engine such as a diesel engine. A (honeycomb) structure is used (see Patent Document 1 below).

JP 2008-119663 A

  A honeycomb structure for DPF is usually a columnar body. The columnar honeycomb structure is formed with a plurality of through holes penetrating between the opposing end faces. On one end surface (first end surface) of the honeycomb structure, the end portions of the open through holes and the end portions of the through holes closed by the sealing portions are alternately arranged in a lattice pattern. The through hole whose end is open on the first end surface is closed with a sealing portion on the second end surface opposite to the first end surface. Further, the through hole whose end is closed by the sealing portion on the first end surface is open on the second end surface. Therefore, also on the second end surface, the end portions of the open through holes and the end portions of the through holes closed by the sealing portions are alternately arranged in a lattice pattern.

  In order to manufacture a honeycomb structure in which the through hole is closed by the sealing portion as described above, the raw columnar body is fired, and one end of the through hole of the fired columnar body is closed with the raw sealing material. A process (hereinafter referred to as “sealing process”) is required. Furthermore, the process of forming a sealing part by sintering a raw sealing material by baking again the columnar body after a sealing process is also needed. As described above, the manufacturing method of the conventional honeycomb structure is low in productivity in that the two firing steps are essential with the sealing step interposed therebetween. Moreover, even if it implements the 2nd baking process after a sealing process, a sealing part and the partition of a through-hole may not fully sinter. In this case, a gap is formed between the sealing portion and the partition wall, or the sealing portion is dropped from the through hole. As a result, the capture rate of fine particles by the honeycomb structure decreases.

  The present invention has been made in view of such problems of the prior art, and has high productivity, and is a green molding suitable for manufacturing a honeycomb structure in which a sealing portion and a partition wall of a through hole are sufficiently sintered. The purpose is to provide a body.

  In order to achieve the above object, one embodiment of the green molded body according to the present invention includes a honeycomb-shaped columnar body having a plurality of through-holes that are substantially parallel to each other and having partition walls separating the plurality of through-holes, and a through-hole. A sealing material that closes one end of each of the plurality of through holes, wherein some of the through holes are sealed at the first end surface of the first end surface and the second end surface of the columnar body substantially orthogonal to the through hole. The other through-hole is closed with a sealing material at the second end surface and open at the first end surface, the sealing material contains ceramics, and the columnar body is closed with a material. A ceramic raw material powder is included, and the ceramic is aluminum titanate ceramic and / or cordierite ceramic, and the sealing material is sintered. Of shrinkage, relative shrinkage during sintering of the partition walls, from 80 to 100%.

  In addition, a green molded object means the raw molded object before baking. The sealing material may include not only ceramics but also its raw material powder. Ceramics are, for example, powders or particles of aluminum titanate ceramics or cordierite ceramics. The ceramic raw material powder is a ceramic that is formed by firing.

  In one embodiment of the present invention, the through hole of the raw (unsintered) columnar body is already closed with the sealing material. Therefore, only by firing one embodiment of the green molded body of the present invention, the sintering of the columnar body and the sealing material proceeds substantially simultaneously, and the honeycomb structure is completed. Therefore, the method for manufacturing a honeycomb structure using one embodiment of the green molded body of the present invention has higher productivity than a conventional manufacturing method that requires two firing steps.

  In the above aspect of the present invention, since the shrinkage rate during sintering of the sealing material is 80 to 100% with respect to the shrinkage rate during sintering of the partition walls, the through hole is relatively formed with respect to the sealing material. Shrinkage improves the adhesion and sintering properties between the columnar body (the partition wall of the through hole) and the sealing material.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to provide the green molded object with high productivity and suitable for manufacture of the honeycomb structure in which the sealing part and the partition of the through-hole were fully sintered.

Fig.1 (a) is a perspective view of the green molded object which concerns on one Embodiment of this invention, FIG.1 (b) is a front view of the 1st end surface of the columnar body of Fig.1 (a). Fig.2 (a) is a perspective view of the honeycomb structure formed by baking the green molded body shown to Fig.1 (a) and 1 (b), FIG.2 (b) is FIG.2 (a). It is a front view of the 1st end surface of this honeycomb structure. FIG. 3 (a) is a photograph of the first end face of the honeycomb structure of Example 1, FIG. 3 (b) is a photograph of the first end face of the honeycomb structure of Example 3, and FIG. 6 is a photograph of the first end face of a honeycomb structure of Example 5. FIG.

  Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the drawings. However, the present invention is not limited to the following embodiments. In addition, the same code | symbol is attached | subjected about the same or equivalent element. In addition, although the positional relationship between the top, bottom, left and right is as shown in the drawing, the ratio of dimensions is not limited to that shown in the drawing.

<Green molded body>
As shown in FIGS. 1 (a) and 1 (b), the green molded body 100 is a cylindrical body (columnar body 70) having a honeycomb structure. The columnar body 70 has a plurality of partition walls 70c that are parallel to a central axis (a straight line that is perpendicular to the circular cross section of the columnar body 70 and passes through the center of the circular cross section) and orthogonal to each other. That is, the columnar body 70 has a lattice structure in a cross section perpendicular to the central axis direction. In other words, the columnar body 70 is formed with a large number of through holes 70a (flow passages) extending in the same direction (center axis direction), and the partition walls 70c separate the through holes 70a. Each through hole 70 a is perpendicular to both end faces of the columnar body 70. In addition, the angle which the some partition 70c which the columnar body 70 has mutually is not specifically limited, For example, 120 degrees may be sufficient.

  Some of the plurality of through holes 70a are closed with a sealing material 70b on the first end surface orthogonal to the through holes. On the first end surface, the end portions of the through holes 70a closed by the sealing material 70b and the end portions of the open through holes 70a are alternately arranged in a lattice pattern. The through-hole 70a closed with the sealing material 70b on the first end surface is open on the second end surface opposite to the first end surface. The through-hole 70a opened on the first end surface is closed with a sealing material 70b on the second end surface (not shown). Therefore, also on the second end face, the end portions of the through holes 70a closed by the sealing material 70b and the end portions of the open through holes 70a are alternately arranged in a lattice pattern. In this manner, the plurality of through holes 70a are closed with the sealing material 70b on either the first end surface or the second end surface.

(Columnar)
The columnar body 70 is obtained by molding a raw material mixture prepared by mixing an inorganic compound source powder (raw material powder), a pore former, an organic binder, a solvent, and the like with a kneader or the like. The inorganic compound source powder includes a titanium source powder and an aluminum source powder as a raw material powder of an aluminum titanate ceramic. The inorganic compound source powder may further include a magnesium source powder and a silicon source powder. The raw material mixture may include the aluminum titanate ceramic itself. Thereby, the shrinkage rate of the green molded object 100 accompanying sintering is reduced. The aluminum titanate ceramic is, for example, aluminum titanate or aluminum magnesium titanate.

[Aluminum source]
The aluminum source is a compound that becomes an aluminum component constituting the aluminum titanate sintered body. Examples of the aluminum source include alumina (aluminum oxide). Examples of the crystal type of alumina include γ-type, δ-type, θ-type, and α-type, and may be indefinite (amorphous). Of these, α-type alumina is preferably used.

  The aluminum source may be a compound that is led to alumina by firing alone in air. Examples of such a compound include an aluminum salt, aluminum alkoxide, aluminum hydroxide, and metal aluminum.

  The aluminum salt may be an inorganic salt with an inorganic acid or an organic salt with an organic acid. Specific examples of the aluminum inorganic salt include aluminum nitrates such as aluminum nitrate and ammonium aluminum nitrate, and aluminum carbonates such as ammonium aluminum carbonate. Examples of the aluminum organic salt include aluminum oxalate, aluminum acetate, aluminum stearate, aluminum lactate, and aluminum laurate.

  Specific examples of the aluminum alkoxide include aluminum isopropoxide, aluminum ethoxide, aluminum sec-butoxide, aluminum tert-butoxide, and the like.

  Examples of the crystal type of aluminum hydroxide include gibbsite type, bayerite type, norosotrandite type, boehmite type, and pseudoboehmite type, and may be amorphous (amorphous). Examples of the amorphous aluminum hydroxide include an aluminum hydrolyzate obtained by hydrolyzing an aqueous solution of a water-soluble aluminum compound such as an aluminum salt or an aluminum alkoxide.

  As an aluminum source, only 1 type may be used and 2 or more types may be used together.

  Of the above, alumina is preferably used as the aluminum source, and more preferably α-type alumina. The aluminum source may contain trace components derived from the raw materials or inevitably contained in the production process.

  The particle size of the aluminum source powder is not particularly limited. For example, the particle diameter of the aluminum source powder corresponding to a volume-based cumulative percentage of 50% measured by a laser diffraction method may be in the range of 20 to 60 μm. This particle diameter is also called D50 or average particle diameter. From the viewpoint of reducing shrinkage during firing, it is preferable to use an aluminum source powder having a D50 in the range of 30 to 60 μm.

  An alumina sol or a silica sol described later can be added to the raw material mixture. Thus, by adding alumina sol, silica sol, etc., fine particles in the raw material mixture are adsorbed to each other, and the amount of particles having a particle diameter of 0.1 μm or less in the green molded body is reduced to the inorganic compound source powder (solid content ) Of 1 to 5 parts by weight, whereby the strength of the molded body after degreasing at 500 ° C. can be made 0.2 kgf or more, for example.

  The alumina sol is a colloid using fine particle alumina as a dispersoid and a liquid as a dispersion medium. Alumina sol can be used alone as an aluminum source, but is preferably used in combination with other aluminum sources. The dispersion medium of alumina sol is removed by evaporation or the like at the time of mixing or calcination, for example.

Examples of the dispersion medium for the alumina sol include aqueous solutions and various organic solvents such as aqueous hydrochloric acid, aqueous acetic acid, aqueous nitric acid, alcohol, xylene, toluene, and methyl isobutyl ketone. As the alumina sol, a colloidal alumina sol having an average particle diameter of 1 to 100 nm is preferably used. By using an alumina sol having such an average particle size, there is an advantage that particles in the raw material mixture can be adsorbed. Examples of commercially available products of alumina sol include “Alumina sol 100”, “Alumina sol 200”, “Alumina sol 520” manufactured by Nissan Chemical Industries, Ltd., “NanoTekAl ₂ O ₃ ” manufactured by CI Kasei. Among these, it is preferable to use "Alumina sol 200" manufactured by Nissan Chemical Industries.

  The alumina sol can be used in an amount of 0 to 10 parts by weight, preferably 0 to 5 parts by weight, based on 100 parts by weight of the inorganic compound source powder (solid content). Two or more kinds of alumina sols may be mixed and used.

[Titanium source]
The titanium source is a compound that becomes a titanium component constituting the aluminum titanate sintered body, and examples of such a compound include titanium oxide. Examples of titanium oxide include titanium (IV) oxide, titanium (III) oxide, and titanium (II) oxide. Among these, titanium (IV) oxide is preferably used. Examples of the crystal form of titanium (IV) oxide include anatase type, rutile type, brookite type and the like, and may be indefinite (amorphous). More preferred is anatase type or rutile type titanium (IV) oxide.

  The titanium source may be a compound that is led to titania (titanium oxide) by firing alone in air. Examples of such compounds include titanium salts, titanium alkoxides, titanium hydroxide, titanium nitride, titanium sulfide, titanium metal and the like.

  Specific examples of the titanium salt include titanium trichloride, titanium tetrachloride, titanium sulfide (IV), titanium sulfide (VI), titanium sulfate (IV), and the like. Specific examples of titanium alkoxide include titanium (IV) ethoxide, titanium (IV) methoxide, titanium (IV) t-butoxide, titanium (IV) isobutoxide, titanium (IV) n-propoxide, titanium (IV) tetraiso Examples thereof include propoxide and chelates thereof.

  As a titanium source, only 1 type may be used and 2 or more types may be used together.

  Among the above, as the titanium source, titanium oxide is preferably used, and titanium (IV) oxide is more preferable. In addition, a titanium source can contain the trace component contained unavoidable in the raw material origin or manufacturing process.

  The particle size of the titanium source powder is not particularly limited. For example, the particle diameter (D50) of the titanium source powder corresponding to a volume-based cumulative percentage of 50% as measured by a laser diffraction method may be in the range of 0.5 to 25 μm. In order to achieve a sufficiently low firing shrinkage ratio, the D50 of the titanium source powder is preferably in the range of 1 to 20 μm. The titanium source powder may show a bimodal particle size distribution. When using a titanium source powder showing such a bimodal particle size distribution, the particle size distribution measured by the laser diffraction method is used. It is preferable that the particle diameter of the peak with a larger particle diameter is in the range of 20 to 50 μm.

  The mode diameter of the titanium source powder measured by the laser diffraction method is not particularly limited as long as it is in the range of 0.3 to 60 μm.

[Magnesium source]
The raw material mixture may contain a magnesium source. The honeycomb structure 170 manufactured from the green molded body 100 containing a magnesium source is a sintered body of aluminum magnesium titanate crystals.

  Examples of the magnesium source include magnesia (magnesium oxide) and a compound that is led to magnesia by firing alone in air. Examples of the latter include magnesium salt, magnesium alkoxide, magnesium hydroxide, magnesium nitride, metal magnesium and the like.

  Specific examples of magnesium salts include magnesium chloride, magnesium perchlorate, magnesium phosphate, magnesium pyrophosphate, magnesium oxalate, magnesium nitrate, magnesium carbonate, magnesium acetate, magnesium sulfate, magnesium citrate, magnesium lactate, magnesium stearate, Examples include magnesium salicylate, magnesium myristate, magnesium gluconate, magnesium dimethacrylate, and magnesium benzoate.

  Specific examples of the magnesium alkoxide include magnesium methoxide and magnesium ethoxide. In addition, a magnesium source can contain the trace component contained unavoidable in the raw material origin or manufacturing process.

As the magnesium source, a compound serving both as a magnesium source and an aluminum source can also be used. An example of such a compound is magnesia spinel (MgAl ₂ O ₄ ).

  As a magnesium source, only 1 type may be used and 2 or more types may be used together.

  The particle size of the magnesium source powder is not particularly limited. For example, the particle diameter (D50) of the magnesium source powder corresponding to a volume-based cumulative percentage of 50% measured by a laser diffraction method may be in the range of 0.5 to 30 μm. From the viewpoint of reducing shrinkage during firing, it is preferable to use a magnesium source powder having a D50 in the range of 3 to 20 μm.

The molar amount of the magnesium source in terms of MgO (magnesia) in the green molded body is based on the total molar amount of the aluminum source in terms of Al ₂ O ₃ (alumina) and the titanium source in terms of TiO ₂ (titania). 0.03 to 0.15, and more preferably 0.03 to 0.12. By adjusting the content of the magnesium source within this range, an aluminum titanate sintered body having a large pore diameter and an open porosity with improved heat resistance can be obtained relatively easily.

[Silicon source]
The raw material mixture may further contain a silicon source. The silicon source is a compound that becomes a silicon component and is contained in the aluminum titanate sintered body. By using the silicon source in combination, it becomes possible to obtain an aluminum titanate sintered body with improved heat resistance. Examples of the silicon source include silicon oxides (silica) such as silicon dioxide and silicon monoxide.

  The silicon source may be a compound that is led to silica by firing alone in air. Examples of such compounds include silicic acid, silicon carbide, silicon nitride, silicon sulfide, silicon tetrachloride, silicon acetate, sodium silicate, sodium orthosilicate, feldspar, and glass frit. Among them, feldspar, glass frit and the like are preferably used, and glass frit and the like are more preferably used in terms of industrial availability and stable composition. Glass frit means flakes or powdery glass obtained by pulverizing glass. As the silicon source, a powder made of a mixture of feldspar and glass frit can also be used.

  When the silicon source is a glass frit, it is preferable to use one having a yield point of 700 ° C. or higher from the viewpoint of further improving the thermal decomposition resistance of the obtained aluminum titanate sintered body. The yield point of the glass frit is defined as a temperature (° C.) at which the expansion of the glass frit is measured from a low temperature by using a thermo mechanical analyzer (TMA), and the expansion stops and then the contraction starts.

As the glass constituting the glass frit, a general silicate glass containing silicate (SiO ₂ ) as a main component (50% by weight or more in all components) can be used. The glass constituting the glass frit includes other components such as alumina (Al ₂ O ₃ ), sodium oxide (Na ₂ O), potassium oxide (K ₂ O), calcium oxide ( CaO), magnesia (MgO) and the like may be included. The glass constituting the glass frit may contain ZrO ₂ in order to improve the hot water resistance of the glass itself.

  As a silicon source, only 1 type may be used and 2 or more types may be used together.

  The particle size of the silicon source powder is not particularly limited. For example, the particle diameter (D50) of the silicon source corresponding to a volume-based cumulative percentage of 50% measured by laser diffraction method may be in the range of 0.5 to 30 μm. In order to further improve the specific gravity of the green molded body and obtain a fired body having higher mechanical strength, it is preferable that D50 of the silicon source is in the range of 1 to 20 μm.

When the raw material mixture contains a silicon source, the content of the silicon source in the raw material mixture is 100 parts by weight of the total amount of the aluminum source in terms of Al ₂ O ₃ (alumina) and the titanium source in terms of TiO ₂ (titania). On the other hand, it is usually 0.1 to 10 parts by weight, preferably 5 parts by weight or less in terms of SiO ₂ (silica). Further, the content of the silicon source in the raw material mixture is more preferably 2% by weight or more and 5% by weight or less in the inorganic compound source contained in the raw material mixture. The silicon source may contain trace components that are derived from the raw materials or inevitably contained in the production process.

As a composite oxide such as magnesia spinel (MgAl ₂ O ₄ ), a compound containing two or more metal elements among titanium, aluminum, silicon, and magnesium can be used as a raw material.

  When the content of particles having a particle size of 0.1 μm or less in 100 parts by weight of the inorganic compound source powder in the raw material mixture is 1 to 5 parts by weight, as described above, alumina sol and / or silica sol is added to the raw material mixture. It is preferable to mix. Silica sol is a colloid using fine particle silica as a dispersoid and liquid as a dispersion medium. The silica sol can be used alone as a silicon source, but is preferably used in combination with other silica sources. The dispersion medium of silica nasol is removed by evaporation or the like at the time of mixing or calcination, for example.

  Examples of the dispersion medium for silica sol include aqueous solutions and various organic solvents such as an aqueous ammonia solution, alcohol, xylene, toluene, and triglyceride. As the silica sol, a colloidal silica sol having an average particle diameter of 1 to 100 nm is preferably used. By using a silica sol having such an average particle size, there is an advantage that particles in the raw material mixture can be adsorbed and melted and bonded during firing.

  Examples of commercially available silica sols include “Snowtex 20, 30, 40, 50, N, O, S, C, 20L, OL, XS, XL, YL, ZL, QAS-40, LSS manufactured by Nissan Chemical Industries, Ltd. -35, LSS-45 "," Adelite AT-20, AT-30, AT-40, AT-50, AT-20N, AT-20A, AT-30A, AT-20Q, AT-300, manufactured by Asahi Denka Co., Ltd. "AT-300Q", "Cataloid S-20L, S-20H, S-30L, S-30H, SI-30, SI-40, SI-50, SI-350, SI-500, SI-" manufactured by Catalyst Kasei Kogyo Co., Ltd. 45P, SI-80P, SN, SA, SC-30 "," Ludox HS-40, HS-30, LS, SM-30, TM, AS, AM "manufactured by DuPont. Among these, it is preferable to use “Snowtex C” that is stable in a colloidal state in a neutral region.

  Content of the silica sol in a raw material mixture should just be 0-10 weight part by solid content with respect to 100 weight part of inorganic compound source powder (solid content), Preferably it may be 0-5 weight part. Two or more kinds of silica sols may be mixed and used.

[Organic binder]
As the organic binder, a water-soluble organic binder is preferable. Examples of the water-soluble organic binder include celluloses such as methylcellulose, hydroxypropylmethylcellulose, and hydroxyethylmethylcellulose; alcohols such as polyvinyl alcohol; salts such as lignin sulfonate.

  The amount of the organic binder is usually 20 parts by weight or less, preferably 15 parts by weight or less, more preferably 6 parts by weight with respect to 100 parts by weight of the inorganic compound source powder. The lower limit amount of the organic binder is usually 0.1 parts by weight, preferably 3 parts by weight.

[solvent]
As the solvent, for example, alcohols such as methanol, ethanol, butanol and propanol, glycols such as propylene glycol, polypropylene glycol and ethylene glycol, and polar solvents such as water can be used. Of these, water is preferable, and ion-exchanged water is more preferably used from the viewpoint of few impurities. The amount of the solvent used is usually 10 to 100 parts by weight, preferably 20 to 80 parts by weight, based on 100 parts by weight of the inorganic compound source powder. A nonpolar solvent may be used as the solvent.

[Other additives]
The raw material mixture can contain an organic additive other than the organic binder. Other organic additives are, for example, pore formers, lubricants and plasticizers, and dispersants.

  Examples of the pore-forming agent include carbon materials such as graphite, resins such as polyethylene, polypropylene, and polymethyl methacrylate, plant materials such as starch, nut shells, walnut shells, and corn, ice, and dry ice. The addition amount of the pore-forming agent is usually 0 to 40 parts by weight, preferably 0 to 25 parts by weight with respect to 100 parts by weight of the inorganic compound source powder. The pore former disappears when the green molded body is fired. Therefore, in the aluminum titanate sintered body, micropores are formed at locations where the pore-forming agent was present.

  Examples of the lubricant and plasticizer include alcohols such as glycerin, caprylic acid, lauric acid, palmitic acid, higher fatty acids such as alginate, oleic acid and stearic acid, and stearic acid metal salts such as Al stearate. The addition amount of the lubricant and the plasticizer is usually 0 to 10 parts by weight, preferably 1 to 5 parts by weight with respect to 100 parts by weight of the inorganic compound source powder.

  Examples of the dispersant include inorganic acids such as nitric acid, hydrochloric acid and sulfuric acid, organic acids such as oxalic acid, citric acid, acetic acid, malic acid and lactic acid, alcohols such as methanol, ethanol and propanol, ammonium polycarboxylate, Surfactants such as oxyalkylene alkyl ethers are listed. The addition amount of the dispersing agent is usually 0 to 20 parts by weight, preferably 2 to 8 parts by weight with respect to 100 parts by weight of the inorganic compound source powder.

(Sealing material)
The sealing material 70b shown in FIG. 1b includes an aluminum titanate ceramic powder. Moreover, the sealing material 70b may contain the pore forming agent, the organic binder, the solvent, and the like, like the columnar body 70. By mixing these components at a predetermined ratio, a pasty sealing material 70b is obtained. It should be noted that ceramic powder obtained by pulverizing ceramic scraps or damaged honeycomb structure obtained in the manufacturing process of the honeycomb structure may be reused as ceramic powder for the sealing material 70b. Thereby, the raw material cost of the honeycomb structure is reduced. The sealing material 70 b may or may not contain the aluminum titanate ceramic raw material powder (inorganic compound source powder), like the columnar body 70. In order to reduce the shrinkage rate of the sealing material 70b that accompanies the sintering, it is preferable that the sealing material 70b contains ceramic powder and does not contain ceramic raw material powder. The average particle size of the ceramic powder is not particularly limited, but may be about 5 to 50 μm. In order to prevent solid-liquid separation of the sealing material 70b, it is preferable that the sealing material 70b is a viscous liquid. Therefore, when the total of the mass of the ceramic powder contained in the sealing material 70b and the mass of the pore-forming agent is 100 parts by mass, the mass of the binder in the sealing material 70b is 0.3 to 3 parts by mass, and the lubricant. Is preferably 3 to 20 parts by mass, and the viscosity of the sealing material 70b is preferably 20 to 200 Pa · s.

The shrinkage rate Rc1 during sintering of the sealing material 70b is 80 to 100% with respect to the shrinkage rate Rc2 during sintering of the partition wall 70c. In addition, Rc1 may be calculated from the following formula (1), for example. Rc2 may be calculated from the following formula (2), for example. In the calculation of Rc1 and Rc2, the shrinkage rates of the sealing material 70b and the partition wall 70c may be measured at a plurality of locations according to the number of cells of the green molded body 100, and the measured values may be averaged.
Rc1 = (S1-S2) / S1 (1)
Rc2 = (T1-T2) / T1 (2)

  In Formula (1), S1 is the magnitude | size of the sealing material 70b with which the edge part of the through-hole 70a of the columnar body 70 was filled. In other words, S1 is the dimension of the sealing material 70b in the direction perpendicular to the wall surface of the partition wall 70c. Therefore, S1 is substantially equal to the inner diameter of the through hole 70a before the firing step. S2 is the size of the sealing portion 170b (sealing material 70b after the firing step) that closes the through hole 70a of the honeycomb structure 170 obtained after the firing step. In other words, S2 is the dimension of the sealing portion 170b in the direction perpendicular to the wall surface of the partition wall 70c after firing. In Formula (2), T1 is the thickness of the partition 70c of the green molded object 100 before a baking process. In formula (2), T2 is the thickness of the partition walls of the honeycomb structure 170 obtained after the firing step. S1, S2, T1, and T2 may be measured by the following method, for example. First, a sample for measurement is arbitrarily cut out from the end face side of the green molded body 100 before the firing step. This sample includes a cell (through hole 70a), a partition wall 70c surrounding the cell, and a sealing portion 170b for closing the cell. In this sample, two opposing portions of the partition wall 70a surrounding the cell are peeled off. Next, the thickness of the partition wall 70c remaining in the sample is measured as T1. Further, the maximum diameter of the sealing portion 170b in the direction perpendicular to the wall surface of the partition wall 70c is measured as S1. After the measurement of S1 and T1, the sample is baked. The thickness of the partition wall 70c after firing is measured as T2. The maximum diameter of the sealing portion 170b (sealing material 70b after firing) in the direction perpendicular to the wall surface of the partition wall 70c is measured as S2. For the measurement of S1, S2, T1, and T2, for example, an optical microscope (manufactured by Keyence Corporation, VHX-1000 digital microscope) may be used.

  When the shrinkage ratio Rc1 during sintering of the sealing material 70b is less than 80% with respect to the shrinkage ratio Rc2 during sintering of the partition wall 70c, the partition wall 70c is deformed so as to be pushed by the sealing portion 170b. It becomes. Further, when Rc1 is less than 80% with respect to Rc2, there is a problem that a part of the partition wall 70c around the sealing portion 170b is cracked. When Rc1 exceeds 100% with respect to Rc2, the shrinkage rate during sintering of the sealing material 70b becomes larger than the shrinkage rate of the columnar body 70, and a gap is generated between the sealed sealing portion 170 and the partition wall. .

  In order to set Rc1 to 80 to 100% with respect to Rc2, the ceramic content in the sealing material 70b may be higher than that of the columnar body 70 (partition wall 70c). Specifically, the content of the ceramic in the sealing material 70b is preferably about 60 to 100 parts by mass and about 75 to 95 parts by mass when the entire sealing material 70b is 100 parts by mass. More preferred. What is necessary is just to adjust the content rate of the ceramic in the columnar body 70 (partition 70c) to a value smaller than this numerical range suitably according to desired Rc2. When the content of ceramics in the sealing material 70b is too small, Rc1 becomes too large, and the adhesion / sinterability between the sealing portion 170 and the partition walls tends to decrease.

  Further, in order to set Rc1 to 80 to 100% with respect to Rc2, the content of the ceramic raw material powder in the sealing material 70b may be lower than that of the columnar body 70 (partition wall 70c). Specifically, the content of the ceramic raw material powder in the sealing material 70b is preferably 0 to 40 parts by mass with respect to 100 parts by mass in total of the ceramic raw material powder, the ceramic powder, and the pore former. What is necessary is just to adjust the content rate of the raw material powder of the ceramic in the columnar body 70 (partition 70c) to a value larger than this numerical range suitably according to desired Rc2. When the content of the ceramic raw material powder in the sealing material 70b is too large, Rc1 becomes too large, and the adhesion between the sealing portion 170 and the partition walls tends to decrease.

  In order to make Rc1 80 to 100% with respect to Rc2, the content of the pore former in the sealing material 70b may be made smaller than that of the columnar body 70 (partition wall 70c). Specifically, the content of the pore former in the sealing material 70b is preferably 0 to 6 parts by mass with respect to a total of 100 parts by mass of the ceramic raw material powder, the ceramic powder, and the pore former. What is necessary is just to adjust the content rate of the pore making material in the columnar body 70 (partition 70c) to a value larger than this numerical range suitably according to desired Rc2. When the content of the pore-forming agent in the sealing material 70b is too small, Rc2 becomes too larger than Rc1, and the partition wall 70c compresses the sealing portion 70b, and the partition wall 70 tends to be deformed. When the content of the pore-forming agent in the sealing material 70b is too large, Rc1 becomes too large, and the adhesion / sinterability between the sealing portion 170 and the partition walls tends to decrease. Thus, the pore-forming agent functions as a cushioning material for forming pores and matching the shrinkage rates of the sealing material 70b and the partition wall 70c.

<Honeycomb structure>
By firing the green molded body 100, the ceramic powder and the ceramic raw material powder included in the columnar body 70 and the sealing portion 70b are sintered. The sealing material 70b is sintered and integrated with the partition wall 70a to form the sealing portion 170b. As a result, as shown in FIGS. 2A and 2B, a honeycomb structure 170 (multi-cell ceramic monolith) made of porous aluminum titanate-based ceramics is obtained. In addition to the crystal pattern of aluminum titanate (Al ₂ TiO ₅ ) or aluminum magnesium titanate (Al _{2 (1-x)} Mg _x Ti _{(1 + x)} O ₅ ), the honeycomb structure 170 has alumina in the X-ray diffraction spectrum. In addition, a crystal pattern such as titania may be included. The honeycomb structure 170 may contain silicon. The honeycomb structure 170 has the same structure as the green molded body 100 and is suitable for the DPF.

  In particular, DPF made of aluminum magnesium titanate sintered body has an extremely small coefficient of thermal expansion, a high melting point, and excellent thermal shock resistance during reproduction, compared to DPF made of SiC, cordierite or aluminum titanate alone. It is excellent in that the limit accumulation amount of soot is large. A platinum-based metal catalyst supported on a carrier such as alumina or a promoter such as ceria or zirconia may be attached to the partition wall surface of the honeycomb structure 170 for DPF.

  Although the aluminum content rate in an aluminum titanate ceramic is not specifically limited, For example, it is 40-60 mol% in conversion of aluminum oxide. The titanium content in the aluminum titanate-based ceramics is not particularly limited, but is, for example, 35 to 55 mol% in terms of titanium oxide. The magnesium content in the aluminum titanate-based ceramics is preferably 1 to 5% by mass in terms of magnesium oxide. The silicon content in the aluminum titanate-based ceramics is preferably 2 to 5% by mass in terms of silicon oxide. In addition, what is necessary is just to adjust suitably the composition of aluminum titanate ceramics with the composition of a raw material mixture. In addition to the above components, the aluminum titanate-based ceramics can contain components derived from raw materials or trace components that are inevitably mixed into work-in-process in the manufacturing process.

The inner diameter (the length of one side of the square) of the cross section perpendicular to the longitudinal direction of the through hole 70a is not particularly limited, and is, for example, 0.8 to 2.5 mm. The length of the honeycomb structure 170 in the direction in which the through hole 70a extends is not particularly limited, and is, for example, 40 to 350 mm. Further, the outer diameter of the honeycomb structure 170 is not particularly limited, but is, for example, 10 to 320 mm. Although the length of the sealing part 170b in the direction where the through-hole 70a is extended is not specifically limited, For example, it is 1-20 mm. The number (cell density) of the through holes 70a opened in the end face of the honeycomb structure 170 is not particularly limited, and is, for example, 150 to 450 cpsi. The unit of cpsi means “/ inch ² ” and is equal to “/(0.0254m) ² ”. Although the thickness of the partition of the through-hole 70a is not specifically limited, For example, it is 0.15-0.76 mm. The effective porosity of the honeycomb structure 170 is about 30 to 60% by volume. The average diameter of the pores formed in the honeycomb structure 170 is about 1 to 20 μm. The pore size distribution (D ₉₀ -D ₁₀ ) / D ₅₀ is about less than 0.5. D ₁₀ , D ₅₀ , and D ₉₀ are pore diameters when the cumulative pore volume is 10%, 50%, and 90% of the total pore volume, respectively.

<Method for producing green molded body>
(Raw material mixture preparation process and molding process)
In order to form the columnar body 70, a raw material mixture is prepared by mixing an inorganic compound source powder, a pore former, an organic binder, a solvent, and the like with a kneader or the like. The columnar body 70 is formed by molding the raw material mixture using an extruder having a die having a grid-like opening. In addition, you may knead | mix the raw material mixture before extrusion molding.

(Sealing material preparation process)
A sealing material is prepared in the same manner as the raw material mixture for the columnar body 70. However, the content rates of the aluminum cetitanate ceramics, the raw material powder, and the pore former in the sealing material are adjusted to values suitable for setting Rc1 to 80 to 100% with respect to Rc2, as described above.

(Sealing process)
In the sealing step, the first mask is attached to the first end surface of the columnar body 70 where the plurality of through holes 70a are open. In the first mask, a mask portion having substantially the same dimensions as the through hole 70a and a plurality of openings are arranged in a staggered manner. A first mask is affixed to the first end surface of the columnar body 70 so that each through-hole 70a overlaps each mask portion and opening. A second mask is attached to the second end surface of the columnar body 70 opposite to the first end surface. The arrangement relationship between the opening and the mask portion of the second mask is opposite to that of the first mask. Therefore, the through hole 70a closed by the mask portion of the first mask on the first end surface side overlaps the opening portion of the second mask on the second end surface side. The through hole 70a closed by the mask portion of the second mask on the second end surface side overlaps with the opening portion of the first mask on the first end surface side. Therefore, all of the plurality of through holes 70a formed in the columnar body 70 are opened at one of the first end surface and the second end surface, and are closed by the mask portion at the other.

  In the sealing step for the first end surface, the sealing material is introduced into the end portion of each through-hole 70a that overlaps the opening of the first mask. In addition, after introducing the sealing material into the through hole 70a, the entire columnar body 70 may be vibrated by a vibrator. As a result, the sealing material is easily filled in the gaps at the end portions of the through holes 70a.

  After the above sealing step for the first end surface, the sealing step for the second end surface to which the second mask is attached is performed in the same manner as the sealing step for the first end surface. After performing the sealing step on both end faces, each mask is peeled off from each end face. Thereby, the green molded object 100 shown to FIG. 1 (a), 1 (b) is completed.

<Manufacturing method of honeycomb structure>
The green molded body 100 produced by the above method is calcined (degreasing) and fired, whereby a honeycomb structure 170 shown in FIGS. 2A and 2B can be obtained. The honeycomb structure 170 substantially maintains the shape of the green molded body 100 immediately after extrusion molding.

  The calcination (degreasing) is a process for removing the organic binder in the green molded body 100 and the organic additive blended as necessary by burning or decomposing. A typical calcination process corresponds to an initial stage of the firing process, that is, a temperature raising stage (for example, a temperature range of 300 to 900 ° C.) until the green molded body 100 reaches the firing temperature. In the calcination (degreasing) step, it is preferable to suppress the temperature increase rate as much as possible.

  The firing temperature of the green molded body 100 is usually 1300 ° C. or higher, preferably 1400 ° C. or higher. The firing temperature is usually 1650 ° C. or lower, preferably 1550 ° C. or lower. By heating the green molded body 100 in this temperature range, the inorganic compound source powder and the ceramic powder in the green molded body 100 are surely sintered. The rate of temperature increase up to the firing temperature is not particularly limited, but is usually 1 ° C./hour to 500 ° C./hour.

  Firing is usually performed in the atmosphere, but depending on the type and usage ratio of the raw material powder used, that is, aluminum source powder, titanium source powder, magnesium source powder and silicon source powder, an inert gas such as nitrogen gas or argon gas. The firing may be performed in a reducing gas such as carbon monoxide gas or hydrogen gas. Further, the firing may be performed in an atmosphere in which the water vapor partial pressure is lowered.

  Firing is usually performed using a conventional firing furnace such as a tubular electric furnace, a box-type electric furnace, a tunnel furnace, a far-infrared furnace, a microwave heating furnace, a shaft furnace, a reflection furnace, a rotary furnace, or a roller hearth furnace. Firing may be performed batchwise or continuously. Moreover, you may carry out by a stationary type and may carry out by a fluid type.

  The time required for firing is sufficient as long as the green molded body 100 transitions to the aluminum titanate-based crystal, and varies depending on the amount of the green molded body 100, the type of firing furnace, the firing temperature, the firing atmosphere, and the like. Usually, it is 10 minutes to 24 hours.

  Note that the green molded body 100 may be calcined and fired individually or continuously. In the calcination step, the green molded body 100 may be heated at a temperature equal to or higher than the thermal decomposition temperature of the organic binder and other organic additives and lower than the sintering temperature of the inorganic compound source powder. In the firing step, the green molded body 100 after the calcination step may be heated at a temperature equal to or higher than the sintering temperature of the inorganic compound source powder.

  As mentioned above, although one suitable embodiment of the present invention was described in detail, the present invention is not limited to the above-mentioned embodiment.

  For example, the columnar body 70 and the sealing material 70b may include ceramics such as cordierite ceramics and silicon carbide instead of aluminum titanate ceramics. Further, the columnar body 70 and the sealing material 70b may include these ceramic raw material powders. As the raw material powder for cordierite-based ceramics, the above-described aluminum source powder, silica source powder and magnesium source powder may be used. The shape of the honeycomb structure 170 is not limited to a cylinder, and can take any shape depending on the application. For example, the shape of the honeycomb structure 170 may be a polygonal column, an elliptical column, or the like.

  The use of the honeycomb structure is not limited to DPF. The honeycomb structure includes an exhaust gas filter or catalyst carrier used for exhaust gas purification of an internal combustion engine such as a gasoline engine, a filter used for filtering food and drink such as beer, and gas components (for example, carbon monoxide, carbon dioxide, etc.) generated during petroleum refining. , Nitrogen, oxygen, etc.) can be suitably applied to ceramic filters such as a selective permeation filter. In particular, when used as a ceramic filter or the like, aluminum titanate-based ceramics have a high pore volume and an open porosity, so that good filter performance can be maintained over a long period of time.

  EXAMPLES Hereinafter, although an Example demonstrates this invention still in detail, this invention is not limited to these Examples.

Example 1
In order to form a columnar body, a raw material powder of aluminum magnesium titanate (Al ₂ O ₃ , TiO ₂ , MgO), a ceramic powder having a composite phase of SiO ₂ , aluminum magnesium titanate, alumina and aluminosilicate glass (preparation) Composition formula at the time: 41.4 Al ₂ O ₃ -49.9 TiO ₂ -5.4 MgO-3.3SiO ₂ , the numerical values in the formula represent molar ratios.), Organic binder, lubricant, pore former, plasticizer A raw material mixture containing a dispersant and water (solvent) was prepared. The content of each component in the raw material mixture was adjusted to the following values.
Al ₂ O _3: 37.3 parts by weight.
TiO ₂ : 37.0 parts by mass.
MgO: 1.9 parts by mass.
SiO ₂ : 3.0 parts by mass.
Ceramic powder: 8.8 parts by mass.
Pore-forming agent: 12.0 parts by mass of starch having an average particle size of 25 μm obtained from potato.
Organic binder: 7.8 parts by mass.
Plasticizer: 0.4 parts by mass.
Dispersant: 4.6 parts by mass.
Water: 28.3 parts by mass.

The raw material mixture is kneaded and extruded using a die for producing a lattice-shaped opening having six hexagons deformed so as to surround a regular hexagon. A cylinder (columnar body) in which a through hole was formed was produced. The length of one side of the regular hexagonal through-hole formed in the columnar body was 0.8 mm. The number of through holes (cell density) opened in the end face of the columnar body was 0.4 / mm ² . The length of the columnar body in the direction in which the through hole extends was 171 mm. Moreover, the outer diameter of the end surface of the columnar body was 162 mm.

The sealing material 70b of Example 1 was prepared by mixing ceramic powder, a pore former, an organic binder, a lubricant, and a solvent. As the ceramic powder, powder prepared by pulverizing scraps and defective products obtained in the manufacturing process of the honeycomb structure was reused. This ceramic powder is a powder having a composite phase of aluminum magnesium titanate, alumina, and aluminosilicate glass (composition formula at the time of preparation: 41.4 Al ₂ O ₃ -49.9 TiO ₂ -5.4 MgO-3.3SiO ₂ , The numerical value in the formula represents the molar ratio.). The average particle size of the ceramic powder was adjusted to 22 μm. As the pore-forming agent, starch having an average particle size of 44 μm obtained from potato was used. As the organic binder, hydroxypropylmethylcellulose (manufactured by Samsung Precision Chemical Co., Ltd .: PMB-15UFF) was used. Glycerin was used as the lubricant. Water was used as the solvent. The compounding ratio of the ceramic powder, pore former, organic binder, lubricant and solvent in the sealing material was adjusted to the values shown in Table 1.

  After performing the sealing process of the 1st end surface of a columnar body using the sealing material, the sealing process with respect to the 2nd end surface was implemented. Thereby, some through-holes of the plurality of through-holes are blocked by the sealing material at the first end surface of the columnar body, open at the second end surface, and the other through-holes are blocked by the sealing material at the second end surface. The green molding of Example 1 is open at the first end face, and the end portions of the through holes closed by the sealing material and the end portions of the open through holes are alternately arranged in a lattice pattern on each end face Got the body.

  The green molded body was dried and fired at 1530 ° C. for 5 hours to obtain a honeycomb structure of Example 1 made of a sintered body of porous aluminum magnesium titanate.

(Examples 2 to 6)
The honeycomb structures of Examples 2 to 6 are the same as Example 1 except that the compounding ratio of the ceramic powder, pore former, organic binder, lubricant and solvent in the sealing material was adjusted to the values shown in Table 1. Were prepared.

  The shrinkage rate Rc1 during sintering of the sealing materials of Examples 1 to 6 and the shrinkage rate Rc2 during sintering of the partition walls were determined. Each shrinkage rate is shown in Table 1. In the calculation of Rc1 and Rc2, values measured at five locations were averaged.

  The photograph of the 1st end surface of each honeycomb structure of Example 1, 3, 5 is shown in FIG. U0918-R in FIG. 3A corresponds to the first embodiment. U0920-T in FIG. 3B corresponds to the third embodiment. U0922-W in FIG. 3C corresponds to the fifth embodiment.

  In any of the honeycomb structures of Examples 1 to 6, it was confirmed that the sealing portion and the partition wall of the through hole were sufficiently sintered and there was no gap between them.

  According to one aspect of the green molded body of the present invention, a honeycomb structure (for example, DPF) in which the sealing portion and the partition wall of the through hole are sufficiently sintered can be manufactured with high productivity.

  70 ... Columnar body, 70a ... Through hole, 70b ... Sealing material, 70c ... Partition, 100 ... Green molded body, 170b ... Sealing part, 170 ... Honeycomb structure.

Claims (1)

A plurality of through-holes substantially parallel to each other, and a honeycomb-like columnar body having partition walls separating the plurality of through-holes;
A sealing material for closing one end of the through hole;
With
Among the plurality of through-holes, some of the through-holes are blocked by the sealing material at the first end surface of the first end surface and the second end surface of the columnar body substantially orthogonal to the through-hole, Open at the two ends,
The other through hole is closed with the sealing material at the second end surface, and is open at the first end surface,
The sealing material includes ceramics;
The columnar body includes the ceramic raw material powder,
The ceramic is an aluminum titanate ceramic and / or cordierite ceramic,
The shrinkage rate during sintering of the sealing material is 80 to 100% with respect to the shrinkage rate during sintering of the partition walls.
Green molded body.