WO2021075211A1 - Structure céramique en nid d'abeilles et procédé de fabrication associé - Google Patents

Structure céramique en nid d'abeilles et procédé de fabrication associé Download PDF

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Publication number
WO2021075211A1
WO2021075211A1 PCT/JP2020/035603 JP2020035603W WO2021075211A1 WO 2021075211 A1 WO2021075211 A1 WO 2021075211A1 JP 2020035603 W JP2020035603 W JP 2020035603W WO 2021075211 A1 WO2021075211 A1 WO 2021075211A1
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pore
volume
pore volume
less
pore diameter
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PCT/JP2020/035603
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Japanese (ja)
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清水　健一郎
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日立金属株式会社
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Priority to JP2021552281A priority Critical patent/JP7501540B2/ja
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D39/00—Filtering material for liquid or gaseous fluids
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D39/00—Filtering material for liquid or gaseous fluids
    • B01D39/14—Other self-supporting filtering material ; Other filtering material
    • B01D39/20—Other self-supporting filtering material ; Other filtering material of inorganic material, e.g. asbestos paper, metallic filtering material of non-woven wires
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D46/00—Filters or filtering processes specially modified for separating dispersed particles from gases or vapours
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B38/00—Porous mortars, concrete, artificial stone or ceramic ware; Preparation thereof
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B38/00—Porous mortars, concrete, artificial stone or ceramic ware; Preparation thereof
    • C04B38/06—Porous mortars, concrete, artificial stone or ceramic ware; Preparation thereof by burning-out added substances by burning natural expanding materials or by sublimating or melting out added substances
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
    • F01N3/02—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust
    • F01N3/021—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters
    • F01N3/022—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters characterised by specially adapted filtering structure, e.g. honeycomb, mesh or fibrous

Definitions

  • the present invention is a ceramic honeycomb for purifying exhaust gas by removing particulate matter (particulate matter (hereinafter, may be referred to as "PM")) in exhaust gas emitted from an internal combustion engine such as a diesel engine.
  • the present invention relates to a ceramic honeycomb structure used for a filter, particularly a ceramic honeycomb filter for removing fine particles (so-called nanoparticles) having a particle size of 50 nm or less.
  • Diesel engine exhaust gas contains PM (Particulate Matter) whose main components are soot composed of carbonaceous material and SOF component (Soluble Organic Fraction: soluble organic component) composed of high-boiling hydrocarbon components. If it is released into the atmosphere, it may adversely affect the human body and the environment. Therefore, it has been customary to install a ceramic honeycomb filter for collecting PM in the middle of the exhaust pipe of a diesel engine. It is done.
  • Fig. 1 and Fig. 2 show an example of a ceramic honeycomb filter for collecting PM in the exhaust gas and purifying the exhaust gas.
  • the ceramic honeycomb filter 10 includes a ceramic honeycomb structure composed of a porous partition wall 2 forming a plurality of flow paths 3 and 4 and an outer peripheral wall 1, and exhaust gas inflow side end faces 8 and outflow side end faces of the flow paths 3 and 4. It consists of an inflow side sealing portion 6a and an outflow side sealing portion 6c that alternately seal 9 in a checkered pattern.
  • the ceramic honeycomb filter 10 is fixed so as not to move during use by gripping the outer peripheral wall 1 with a gripping member (not shown) formed of a metal mesh or a ceramic mat or the like, and is a metal storage container (not shown). (Not shown) is placed inside.
  • the exhaust gas is purified as follows. As shown by the dotted arrow in FIG. 2, the exhaust gas flows into the ceramic honeycomb filter 10 from the outflow side sealing flow path 3 opened in the exhaust gas inflow side end face 8, passes through the partition wall 2, and the exhaust gas flows out. It flows out from the inflow side sealing flow path 4 opened in the side end surface 9 and is released into the atmosphere. When the exhaust gas passes through the partition wall 2, PM in the exhaust gas is collected in the communication holes existing on the surface and inside of the partition wall 2, and the exhaust gas is purified.
  • the communication holes on the surface and inside of the partition wall are clogged by the PM, and the pressure loss when the exhaust gas passes through the ceramic honeycomb filter, that is, when the PM is collected. Pressure loss rises. Therefore, it is necessary to burn and remove the PM to regenerate the ceramic honeycomb filter before the pressure loss when the PM is collected reaches a specified value. If the pressure loss when PM is collected reaches the specified value more often, that is, if the pressure loss characteristics when PM is collected are not good, the frequency of regeneration increases, and the ceramic is burned by regeneration. The melting damage of the honeycomb filter may be accelerated and the life may be shortened.
  • the ceramic honeycomb filter needs to satisfy the high collection rate and low pressure loss of fine particles, but since they are in a contradictory relationship, the porosity, the pore volume, the size of the pores existing on the partition surface, etc. Conventionally, a technique for controlling and satisfying both of them has been studied.
  • nanoparticles with a particle size of 50 nm or less in PM.
  • the deposition rate in the respiratory system is higher than when larger particles of the same mass are inhaled.
  • nanoparticles may become PM particles with stronger toxicity when a toxic chemical substance is adsorbed on the particle surface. Since the amount of nanoparticles contained in PM is small in terms of mass, the current PM mass standard regulations are not sufficient, and future emission regulations will suppress the emission of nanoparticles, which greatly affect the number of emitted particles. Standards for this (PM particle number standard) are being introduced.
  • the honeycomb filter In order to satisfy this standard, it is important for the honeycomb filter to have excellent pressure drop characteristics, especially when PM is collected, rather than the initial pressure loss at the start of use. In addition, it is necessary to improve the collection rate based on the number of PM particles, especially the number of nanoparticles, instead of the current collection rate based on the PM mass.
  • Patent Document 1 International Publication No. 2016/152709 is a ceramic honeycomb structure having a large number of flow paths partitioned by a porous partition wall, and the partition wall has (a) a porosity of 50 to 60%. , (B) In the pore distribution measured by the mercury intrusion method, (i) the pore diameter d5 at which the cumulative pore volume is 5% of the total pore volume is 22 ⁇ m or more and less than 55 ⁇ m, and the pore diameter d10 at which it is 10%.
  • the body is disclosed, and this ceramic honeycomb structure effectively collects nano-sized PM, which greatly affects the number of particles in the exhaust gas, even in the state before PM is deposited at the beginning of use. It is stated that the collection rate based on the number of PM particles is improved, and the pressure loss characteristic when PM is collected does not decrease.
  • the "state before PM is deposited at the initial stage of use” means when the ceramic honeycomb filter is used from an unused state or when it is used again after being regenerated.
  • Patent Document 2 International Publication No. 2016/152727 is a ceramic honeycomb structure having a large number of flow paths partitioned by a porous partition wall, and the partition wall has (a) a porosity of 50 to 63%. , (B) In the pore distribution measured by the mercury intrusion method, (i) the pore diameter d2 at which the cumulative pore volume is 2% of the total pore volume is more than 180 ⁇ m and 250 ⁇ m or less, and the pore diameter d5 is 5%.
  • nano-sized PM that greatly affects the number of particles in the exhaust gas is effectively used even in the state before PM is deposited at the initial stage of use. It can be collected, and the effects of improving the collection rate based on the number of PM particles and not reducing the pressure loss characteristics when PM is collected are recognized.
  • the ceramic honeycomb structures described in Patent Document 1 and Patent Document 2 have a high porosity of 50% or more, further improvement in strength against impact in handling and the like is desired.
  • an object of the present invention is a PM collection rate that effectively collects nano-sized PM, which greatly affects the number of particles in the exhaust gas, even in a state before PM is deposited at the initial stage of use, and a honeycomb.
  • the present inventors have found that in the pore distribution of the ceramic honeycomb structure, the pore volume having a pore diameter of 5 ⁇ m or more and less than 8 ⁇ m affects the strength of the ceramic honeycomb structure.
  • a pore volume having a pore diameter of 1 ⁇ m or more and less than 4 ⁇ m affects the pressure drop characteristics when PM is collected, and came up with the present invention.
  • the ceramic honeycomb structure of the present invention has a large number of flow paths formed in the axial direction separated by a porous partition wall, and the partition wall has (a) a porosity of 52 to 63% and (b).
  • the pore volume with a pore diameter of 100 ⁇ m or more is 2.2 to 3.0% of the total pore volume
  • the pore volume with a pore diameter of 40 ⁇ m or more is 4.2 to 5.0% of the total pore volume.
  • the pore volume with a pore diameter of 30 ⁇ m or more is 5.8 to 6.5% of the total pore volume
  • the pore volume with a pore diameter of 5 ⁇ m or more and less than 8 ⁇ m is 8 to 12% of the total pore volume
  • the pore volume with a pore diameter of 1 ⁇ m or more and less than 4 ⁇ m Is more than 9.6% and 13% or less of the total pore volume
  • the pore volume with a pore diameter of less than 3 ⁇ m is 8 to 12% of the total pore volume
  • the pore volume with a pore diameter of less than 2 ⁇ m is 4.5 to 7.0 of the total pore volume.
  • Porosity d10 with a pore volume of less than 1 ⁇ m is 1.7 to 4.0% of the total pore volume, and cumulative pore volume is 10% of the total pore volume is 18 to 22 ⁇ m, and pore diameter d25 is 25%. 13.0 to 15.5 ⁇ m, 50% pore diameter (median pore diameter) d50 is 10 to 13 ⁇ m, 75% pore diameter d75 is 6 to 9 ⁇ m, and cumulative pore volume is 20% of the total pore volume.
  • the difference ⁇ log (d20) -log (d80) between the logarithm of the pore diameter d20 and the logarithm of the pore diameter d80 which is 80% is 0.45 or less.
  • the porosity is preferably 54 to 61%.
  • the coefficient of thermal expansion in the flow path direction between 40 and 800 ° C. is preferably 3 ⁇ 10 -7 / ° C. to 11 ⁇ 10 -7 / ° C.
  • a step of extruding a clay containing a pore-forming material composed of a ceramic raw material powder and hollow resin particles into a predetermined molded body, and drying and firing the molded body is performed.
  • the ratio of the pore-forming material contained in the clay is 1 to 8 parts by mass with respect to 100 parts by mass of the ceramic raw material powder, and the ceramic raw material powder is 15 to 22% by mass of silica, 40.
  • the silica Containing ⁇ 43% by mass of talc, 15-30% by mass of alumina, and 1 to 13% by mass of kaolin, the silica has a median diameter of 13 to 25 ⁇ m, D10 of 1 to 5 ⁇ m, and D90 of 30 to 40 ⁇ m.
  • the proportion of particles with a particle size of 10 ⁇ m or less is 20 to 35% by mass
  • the proportion of particles with a particle size of 100 ⁇ m or more is 2% by mass or less
  • the talc has a median diameter D50 of 5 to 15 ⁇ m
  • the alumina has a median diameter D50 of 3 to 6 ⁇ m
  • the pore-forming material has a median diameter D50 of 20 to 55 ⁇ m.
  • the particle size D10 at the cumulative volume corresponding to 10% of the total volume is 15 to 30 ⁇ m
  • the particle size D90 at the cumulative volume corresponding to 90% is 60 to 80 ⁇ m.
  • nano-sized PM that greatly affects the number of particles in the exhaust gas can be effectively collected even in the state before PM is accumulated at the initial stage of use, and PM is collected and accumulated. It is possible to provide a ceramic honeycomb structure having good strength and improved strength, and a method for manufacturing such a ceramic honeycomb structure.
  • FIG. 5 is a cross-sectional view schematically showing a corner radius formed at a partition wall intersection in a cross section of the ceramic honeycomb structure of the present invention.
  • the ceramic honeycomb structure of the present invention has a large number of flow paths formed in the axial direction separated by a porous partition wall, and the partition wall has (a) a porosity of 52 to 63. %, (B) In the pore distribution measured by the mercury intrusion method, the pore volume with a pore diameter of 100 ⁇ m or more is 2.2 to 3.0% of the total pore volume, and the pore volume with a pore diameter of 40 ⁇ m or more is the total pore volume.
  • pore volume of pore diameter 30 ⁇ m or more is 5.8-6.5% of total pore volume
  • pore volume of pore diameter 5 ⁇ m or more and less than 8 ⁇ m is 8-12% of total pore volume
  • pore diameter 1 ⁇ m or more 4 ⁇ m Porosity less than 9.6% and 13% or less of total pore volume
  • pore volume less than 3 ⁇ m 8-12% of total pore volume pore volume less than 2 ⁇ m total pores
  • Porosity d10 with a volume of 4.5 to 7.0%, a pore volume of less than 1 ⁇ m is 1.7 to 4.0% of the total pore volume, and a cumulative pore volume is 10% of the total pore volume is 18 to 22 ⁇ m, 25%.
  • the pore diameter d25 is 13.0 to 15.5 ⁇ m
  • the pore diameter (median pore diameter) d50 is 10 to 13 ⁇ m
  • the pore diameter d75 is 6 to 9 ⁇ m
  • the cumulative pore volume is the total pore volume.
  • the difference ⁇ log (d20) -log (d80) between the log of the pore diameter d20 which is 20% and the log of the pore diameter d80 which is 80% is 0.45 or less.
  • the ceramic honeycomb structure has such a structure, it is possible to effectively collect minute PMs that greatly affect the number of discharged particles even in a state before PMs are deposited at the initial stage of use. It is possible to have a ceramic honeycomb structure having improved strength while maintaining good PM collection rate based on the number of PM particles and pressure loss characteristics when PM is collected and accumulated.
  • the porosity of the partition wall is 52 to 63%. When the porosity is less than 52%, it becomes difficult to maintain a low pressure loss when PM is collected and accumulated, while when the porosity exceeds 63%, the nano-sized PM collection rate decreases. ..
  • the upper limit of the porosity is preferably 61%, more preferably 60%, and the lower limit is preferably 54%, further preferably 55%.
  • the porosity of the partition wall is measured by the mercury injection method described later.
  • the pore distribution of partition walls is limited to a narrower range than before in order to obtain the above effects.
  • the pore distribution curve has different slopes of the pore distribution curve between the fine pore region and the coarse pore region and the region in between, and thus (i) pores in a specific pore diameter range.
  • the pore distribution was defined using two methods: a method of defining the volume ratio and (ii) a method of defining the pore diameter that gives a specific pore volume ratio.
  • (I) was used for the fine pore region having a pore diameter of less than 4 ⁇ m and the coarse pore region having a pore diameter of 30 ⁇ m or more, and (ii) was used for the intermediate region.
  • the pore volume having a pore diameter of 100 ⁇ m or more is 2.2 to 3.0% of the total pore volume
  • the pore volume having a pore diameter of 40 ⁇ m or more is 4.2 to 5.0% of the total pore volume
  • the pore diameter is 30 ⁇ m or more.
  • the pore volume is 5.8 to 6.5% of the total pore volume, the pore volume of 5 ⁇ m or more and less than 8 ⁇ m is 8 to 12% of the total pore volume, and the pore volume of 1 ⁇ m or more and less than 4 ⁇ m is the total pore. Pore volume of more than 9.6% and 13% or less of the volume, pore volume of less than 3 ⁇ m is 8 to 12% of the total pore volume, pore volume of less than 2 ⁇ m is 4.5 to 7.0% of the total pore volume, pore diameter The pore volume less than 1 ⁇ m is 1.7-4.0% of the total pore volume.
  • the pore size distribution curve of the partition wall measured by the mercury intrusion method is, for example, a curve (cumulative pore volume curve) in which the cumulative pore volume is plotted against the pore diameter, as shown in FIG. It is integrated from the side with the larger pore diameter to the side with the smaller pore diameter, and FIG. 4 shows the total pore volume as 100% based on the cumulative pore volume curve shown in FIG. It is a graph.
  • the ratio of the pore volume having a pore diameter of 100 ⁇ m or more to the total pore volume ⁇ the ratio of the pore volume having a pore diameter of 40 ⁇ m or more to the total pore volume ⁇ the pore volume having a pore diameter of 30 ⁇ m or more is total fine.
  • the pore volume of 100 ⁇ m or more is 2.2 to 3.0% of the total pore volume.
  • the pore volume of 100 ⁇ m or more exceeds 3.0% of the total pore volume, the nano-sized PM collection rate decreases and the proportion of coarse pores increases, so that the mechanical strength of the ceramic honeycomb structure increases. It may not be good.
  • the pore volume of 100 ⁇ m or more is less than 2.2% of the total pore volume, it becomes difficult to keep the initial pressure loss at the start of use low.
  • the upper limit of the pore volume of 100 ⁇ m or more is preferably 2.9%.
  • the pore volume of 40 ⁇ m or more is 4.2 to 5.0% of the total pore volume.
  • the pore volume of 40 ⁇ m or more exceeds 5.0% of the total pore volume, the proportion of coarse pores increases, so improvement in the strength of the ceramic honeycomb structure may not be expected, and nano-sized PM is used. It becomes difficult to collect effectively.
  • the pore volume of 40 ⁇ m or more is less than 4.2% of the total pore volume, it becomes difficult to keep the pressure loss after PM collection low.
  • the upper limit of the pore volume of 40 ⁇ m or more is preferably 4.9%, and the lower limit is preferably 4.3%.
  • the pore volume of 30 ⁇ m or more is 5.8 to 6.5% of the total pore volume.
  • the pore volume of 30 ⁇ m or more exceeds 6.5% of the total pore volume, the proportion of coarse pores increases, so improvement in the strength of the ceramic honeycomb structure may not be expected, and nano-sized PM is used. It becomes difficult to collect effectively.
  • the pore volume of 30 ⁇ m or more is less than 5.8% of the total pore volume, it becomes difficult to keep the pressure loss after PM collection low.
  • the upper limit of the pore volume of 30 ⁇ m or more is preferably 6.4%, and the lower limit is preferably 5.9%.
  • the pore volume of 5 ⁇ m or more and less than 8 ⁇ m is 8 to 12% of the total pore volume.
  • nano-sized PM that greatly affects the number of particles in the exhaust gas can be effectively used even in the state before PM is deposited at the beginning of use. It can be collected, and the pressure loss characteristics when PM is collected and accumulated can be maintained well, and the strength can be improved.
  • the pore volume of 5 ⁇ m or more and less than 8 ⁇ m is more than 12% of the total pore volume, improvement in the strength of the ceramic honeycomb structure may not be expected.
  • the pore volume of 5 ⁇ m or more and less than 8 ⁇ m is less than 8% of the total pore volume, the proportion of relatively coarse pores increases, and it becomes difficult to effectively collect nano-sized PM.
  • the upper limit of the pore volume of 5 ⁇ m or more and less than 8 ⁇ m is preferably 11.5%, more preferably 11.0%, and the lower limit is preferably 8.5%, further preferably 9.0%.
  • the pore volume of 1 ⁇ m or more and less than 4 ⁇ m is more than 9.6% of the total pore volume and 13% or less.
  • nano-sized PM that greatly affects the number of particles in the exhaust gas can be effectively used even in the state before PM is deposited at the beginning of use. It can be collected, and the pressure loss characteristics when PM is collected and accumulated can be maintained well, and the strength can be improved.
  • the pore volume of 1 ⁇ m or more and less than 4 ⁇ m is more than 13% of the total pore volume, it becomes difficult to keep the initial pressure loss at the start of use low.
  • the upper limit of the pore volume of 1 ⁇ m or more and less than 4 ⁇ m is preferably 12.5%, more preferably 12.0%, and the lower limit is preferably 9.8%, further preferably 10%.
  • the pore volume less than 3 ⁇ m is 8-12% of the total pore volume.
  • the upper limit of the pore volume of less than 3 ⁇ m is preferably 11%, more preferably 10.5%, and the lower limit is preferably 8.2%.
  • the pore volume less than 2 ⁇ m is 4.5 to 7.0% of the total pore volume.
  • the upper limit of the pore volume of less than 2 ⁇ m is preferably 6.5%, more preferably 6.2%, and the lower limit is preferably 4.7%, further preferably 4.9%.
  • the pore volume less than 1 ⁇ m is 1.7 to 4.0% of the total pore volume.
  • the upper limit of the pore volume of less than 1 ⁇ m is preferably 3.5%, more preferably 3.0%.
  • the pore size distribution curve of the partition wall measured by the mercury intrusion method is a curve in which the cumulative pore volume is plotted against the pore diameter as described above (cumulative pore volume curve; see, for example, FIG. 3). Since it is expressed by integrating from the side with the larger pore diameter to the side with the smaller pore diameter, d10>d25>d50> d75.
  • the pore diameter d10 at which the cumulative pore volume is 10% of the total pore volume is 18 to 22 ⁇ m. If the pore diameter d10 is less than 18 ⁇ m, it becomes difficult to keep the initial pressure drop at the start of use low, and if it exceeds 22 ⁇ m, the nano-sized PM collection rate decreases.
  • the upper limit of d10 is preferably 21.5 ⁇ m, more preferably 21.0 ⁇ m, and the lower limit is preferably 18.5 ⁇ m, even more preferably 19.0 ⁇ m.
  • the pore diameter d25 where the cumulative pore volume is 25% of the total pore volume, is 13.0 to 15.5 ⁇ m. If the pore diameter d25 is less than 13.0 ⁇ m, it becomes difficult to keep the initial pressure loss at the start of use low, and if it exceeds 15.5 ⁇ m, the nano-sized PM collection rate decreases.
  • the upper limit of d25 is preferably 15.0 ⁇ m, more preferably 14.5 ⁇ m, and the lower limit is preferably 13.5 ⁇ m, even more preferably 14.0 ⁇ m.
  • the median pore diameter d50 is 10 to 13 ⁇ m.
  • the upper limit of the median pore diameter d50 is preferably 12.5 ⁇ m, more preferably 12.0 ⁇ m, and the lower limit is preferably 10.5 ⁇ m, further preferably 11.0 ⁇ m.
  • the pore diameter d75 where the cumulative pore volume is 75% of the total pore volume, is 6-9 ⁇ m. If the pore diameter d75 is less than 6 ⁇ m, it becomes difficult to keep the initial pressure drop at the start of use low, and if it exceeds 9 ⁇ m, the nano-sized PM collection rate decreases.
  • the upper limit of d75 is preferably 8.5 ⁇ m, more preferably 8.0 ⁇ m, and the lower limit is preferably 6.5 ⁇ m, even more preferably 7.0 ⁇ m.
  • ⁇ 2 exceeds 0.30, it becomes difficult to maintain good pressure drop characteristics when PM is collected and accumulated.
  • ⁇ 2 is preferably 0.29 or less, and more preferably 0.28 or less.
  • ⁇ 2 is less than 0.20, the proportion of fine pores is relatively small and the proportion of coarse pores is large, so that it may not be possible to improve the strength of the ceramic honeycomb structure. It becomes difficult to effectively collect nano-sized PM.
  • ⁇ 2 is preferably 0.21 or more, and more preferably 0.22 or more.
  • the logarithm means a common logarithm having a base of 10.
  • the cumulative pore volume measured by the mercury injection method can be measured using Autopore III 9410 manufactured by Micromeritics. This measurement is performed when a test piece (10 mm ⁇ 10 mm ⁇ 10 mm) cut out from a ceramic honeycomb structure is stored in a measurement cell, the inside of the cell is depressurized, and then mercury is introduced and pressurized. This is done by determining the volume of mercury pushed into the pores present in the piece. At this time, the larger the pressing force, the more mercury infiltrates into the finer pores. Therefore, from the relationship between the pressing force and the volume of mercury pushed into the pores, the pore diameter and the cumulative pore volume (maximum).
  • the relationship of the cumulative value of the pore volume from the pore diameter to the specific pore diameter can be obtained.
  • the infiltration of mercury is carried out sequentially from the one having a large pore diameter to the one having a small pore diameter, and the pressure is converted into a pore diameter, and the cumulative pore volume (corresponding to the volume of mercury) integrated from the side having a large pore diameter to the side having a small pore diameter.
  • the pressure at which mercury is introduced is 0.5 psi (0.35 ⁇ 10 -3 kg / mm 2 , equivalent to a pore diameter of about 362 ⁇ m), and the pressure applied by mercury is 1800 psi (1.26 kg / mm 2 , pore diameter of about 0.1).
  • the cumulative pore volume when it reaches (corresponding to ⁇ m) is defined as the total pore volume.
  • the porosity can be calculated from the total pore volume and the true specific gravity of the partition wall material. For example, when the material of the partition wall of the ceramic honeycomb structure is cordierite, if the true specific gravity of cordierite is 2.52 g / cm 3 and the total pore volume is V, then [2.52 V / (1+) Calculate from 2.52V)] x 100 (%).
  • the ceramic honeycomb structure preferably has a thermal expansion coefficient of 13 ⁇ 10 -7 / ° C or less in the flow path direction between 40 and 800 ° C. Since the ceramic honeycomb structure having such a coefficient of thermal expansion has high thermal shock resistance, it can sufficiently withstand practical use as a ceramic honeycomb filter for removing fine particles contained in the exhaust gas of a diesel engine. ..
  • the coefficient of thermal expansion is preferably 3 ⁇ 10 -7 / ° C to 11 ⁇ 10 -7 / ° C, and more preferably 5 ⁇ 10 -7 / ° C to 10 ⁇ 10 -7 / ° C.
  • the ceramic honeycomb structure has an average partition thickness of 9 to 15 mil (0.229 to 0.381 mm) and an average cell density of 150 to 300 cpsi (23.3 to 46.5 cells / cm 2 ). Is preferable.
  • the pressure loss can be kept low at the start of use, the PM collection rate based on the number of particles can be improved, and the pressure loss characteristic when PM is collected and accumulated. Is improved. If the average bulkhead thickness is less than 9 mils, the bulkhead strength will be reduced, while if it exceeds 15 mils, it will be difficult to maintain low pressure drop.
  • the flow path shape in the cross section orthogonal to the flow path direction of the ceramic honeycomb structure may be any of polygons such as quadrangles, hexagons and octagons, circles, ellipses and the like, and the inflow side end face and the outflow side end face are large.
  • Asymmetric shapes with different sheath shapes for example, inflow side octagon, outflow side quadrangle may be used.
  • the fan-shaped convex portion is preferably an arc shape formed so as to overlap the circle 16 centered on the center C W of the partition wall intersection, and the protruding length X of the fan-shaped convex portion is 0.05 to 0.5 times the partition wall thickness. Is preferable. Further, all of the fan-shaped convex portions 15a, 15b, 15c, and 15d do not have to have the same protrusion length, and as shown in FIGS. 6 (b) and 6 (c), the center of the partition wall intersection.
  • a fan-shaped convex portion 15a, 15b, 15c, 15d having arcs 16a, 16b, 16c, 16d formed so as to overlap a circle 16 centered on a point C R separated from C W by a distance S may be formed.
  • So-Sc F 1 ⁇ ⁇ X [where F 1 is a constant of 0.05 to 0.4, ⁇ X Is the distance (mm) from the center of the axial cross section of the ceramic honeycomb structure to the outer peripheral portion], because the strength against impact from the outer peripheral side is improved, which is more preferable.
  • the distance S can be measured by an image measuring machine (Quick Vision manufactured by Mitutoyo Co., Ltd.) from the image data of the optical microscope taken by observing with the optical microscope.
  • (e) Material of partition wall As the material of the partition wall, since the ceramic honeycomb structure is used as a filter for purifying the exhaust gas emitted from the diesel engine, heat-resistant ceramics, that is, alumina, mullite, and cordy. Ceramics having mullite, silicon carbide, silicon nitride, zirconia, aluminum titanate, lithium aluminum silicate or the like as main crystals are preferable. Among them, those having low thermal expansion cordierite or aluminum titanate having excellent thermal shock resistance as the main crystal are preferable. When the main crystal phase is cordierite, it may contain other crystal phases such as spinel, mullite, and sapphirine, and may further contain a glass component. When the main crystal phase is aluminum titanate, elements such as Mg and Si may be dissolved in the aluminum titanate crystal phase, other crystal phases such as mulite may be contained, and grains may be contained. A glass component may be contained as the boundary phase.
  • the ceramic honeycomb filter alternately seals the exhaust gas inflow side or the exhaust gas outflow side of the flow path of the ceramic honeycomb structure of the present invention. Is preferable.
  • the ceramic honeycomb structure of the present invention it is possible to maintain a low pressure loss and improve the PM collection rate based on the number of particles at the start of use, and further, PM is collected and accumulated.
  • a ceramic honeycomb filter having improved pressure loss characteristics can be obtained.
  • the sealing formed on the flow path may be formed on the end face portion of the exhaust gas inflow side or the exhaust gas outflow side of the flow path, and enters the inside of the flow path from the inflow side end face or the outflow side end face. It may be formed at a position.
  • a clay containing a pore-forming material composed of ceramic raw material powder and hollow resin particles is extruded into a predetermined molded body, and described above. It has a step of drying and firing the molded body, and the ratio of the pore-forming material contained in the clay is 1 to 8 parts by mass with respect to 100 parts by mass of the ceramic raw material powder, and the ceramic raw material powder is: It contains 15 to 22% by mass of silica, 40 to 43% by mass of talc, 15 to 30% by mass of alumina, and 1 to 13% by mass of kaolin.
  • the silica has a median diameter D50 of 13 to 25 ⁇ m and D10.
  • D90 is 30 to 40 ⁇ m
  • the proportion of particles with a particle size of 10 ⁇ m or less is 20 to 35% by mass
  • the proportion of particles with a particle size of 100 ⁇ m or more is 2% by mass or less
  • D20 is the particle size in the cumulative volume corresponding to 20% of the total volume
  • D80 is the particle size in the cumulative volume corresponding to 80% of the total volume.
  • the talc has a median diameter D50 of 5 to 15 ⁇ m
  • the alumina has a median diameter D50 of 3 to 6 ⁇ m
  • the pore-forming material has a median diameter D50 of 20 to 55 ⁇ m.
  • the particle size D10 at the cumulative volume corresponding to 10% of the total volume is 15 to 30 ⁇ m
  • the particle size D90 at the cumulative volume corresponding to 90% is 60 to 80 ⁇ m.
  • Grain size distribution deviation SD1 log (D80) -log (D20), D20 is the particle size in the cumulative volume corresponding to 20% of the total volume, and D80 is the cumulative volume corresponding to 80% of the total volume. The particle size is D20 ⁇ D80. ] Is 0.20 to 0.35.
  • the porosity is 52 to 63%
  • the pore volume having a pore diameter of 100 ⁇ m or more is the total pore volume. 2.2-3.0%, pore volume of pore diameter 40 ⁇ m or more is 4.2-5.0% of total pore volume, pore volume of pore diameter 30 ⁇ m or more is 5.8-6.5% of total pore volume, pore diameter 5 ⁇ m or more and less than 8 ⁇ m
  • the pore volume is 8 to 12% of the total pore volume, the pore volume of 1 ⁇ m or more and less than 4 ⁇ m is more than 9.6% of the total pore volume and 13% or less, and the pore volume of less than 3 ⁇ m is total fine.
  • the pore diameter d10 which is 10% of the total pore volume, is 18 to 22 ⁇ m
  • the pore diameter d25 which is 25%
  • the pore diameter (median pore diameter) d50 which is 50%, is 10 to 13 ⁇ m.
  • 75% pore diameter d75 is 6-9 ⁇ m
  • (iii) difference between the log of pore diameter d20 where the cumulative pore volume is 20% of the total pore volume and the log of pore diameter d80 which is 80% ⁇ A ceramic honeycomb structure having a log (d20) -log (d80) of 0.45 or less can be obtained.
  • the pores formed in the ceramics consist of pores formed by melting the ceramic raw material powder in the firing process and pores formed by burning the pore-forming material. Therefore, by setting the median diameter and particle size distribution of the ceramic raw material powder and the pore-forming material within the above-mentioned ranges, it is possible to control the pores generated when the ceramic is fired.
  • the resin particles are burned to form voids and ceramic.
  • the raw material powder is fired to form pores.
  • hollow resin particles which generate less heat due to combustion than solid resin particles, firing cracks are less likely to occur in the process of firing the molded product.
  • the pore diameter of the formed partition wall can be within the above range.
  • the nano-sized PM collection rate and PM It is possible to obtain the ceramic honeycomb structure of the present invention having improved strength while maintaining good pressure loss characteristics when the powder is collected.
  • Ceramic raw material powder contains 15 to 22% by mass of silica, 40 to 43% by mass of talc, 15 to 30% by mass of alumina, and 1 to 13% by mass of kaolin.
  • the ceramic raw material powder is preferably a cordierite raw material.
  • the main crystal of the raw material for making cordierite is cordierite (SiO 2 having a chemical composition of 42 to 56% by mass, Al 2 O 3 having a chemical composition of 30 to 45% by mass, and MgO having 12 to 16% by mass).
  • each raw material powder having a silica source component, an alumina source component and a magnesia source component is blended, and is composed of, for example, silica, talc, alumina, kaolin, aluminum hydroxide and the like.
  • the pores formed in the ceramics having the cordierite as the main crystal are due to the pores formed by firing silica and talc as the ceramic raw materials and the pores formed by burning the pore-forming material. Therefore, by adjusting the particle size and particle size distribution of the ceramic raw material powder such as silica and talc together with the above-mentioned pore-forming material, it is possible to control the pores generated when the cordierite ceramics are fired.
  • silica and the pore-forming material occupy most of the formed pores, and therefore contribute greatly to the pore structure.
  • Silica Silica is known to exist stably up to high temperatures, and at 1300 ° C or higher, its melting point drops due to reaction with other raw materials and diffuses into a liquid phase to form pores. Therefore, when 15 to 22% by mass of silica is contained, a desired amount of pores can be obtained. Including silica in excess of 22% by weight must reduce other silica source components, kaolin and / or talc, in order to maintain the main crystal in the cordierite, resulting in the gain by kaolin. The effect of low thermal expansion (effect obtained by orienting kaolin during extrusion molding) is reduced, and thermal impact resistance is reduced. On the other hand, if it is less than 15% by mass, the number of pores formed in the partition wall is reduced, so that a low pressure loss when PM is collected and accumulated may not be obtained.
  • the silica content is preferably 17-21% by mass.
  • Silica has a median diameter D50 of 13 to 25 ⁇ m, and in the curve showing the relationship between the particle size and the cumulative volume, the particle size D10 at the cumulative volume corresponding to 10% of the total volume is 1 to 5 ⁇ m, and 90% of the total volume.
  • the particle size D90 in the cumulative volume corresponding to is 30 to 40 ⁇ m, the proportion of particles having a particle size of 10 ⁇ m or less is 20 to 35% by mass, the proportion of particles having a particle size of 100 ⁇ m or more is 2% by mass or less, and the particle size distribution.
  • Deviation SD2 log (D80) -log (D20), D20 is the particle size in the cumulative volume corresponding to 20% of the total volume, and D80 is the cumulative volume corresponding to 80% of the total volume.
  • the particle size is D20 ⁇ D80.
  • the median diameter D50 of silica When the median diameter D50 of silica is less than 13 ⁇ m, the proportion of micropores in the pores formed in the partition wall increases, which causes an increase in pressure loss when PM is collected and accumulated. On the other hand, when it exceeds 25 ⁇ m, the number of coarse pores increases and the nano-sized PM collection rate decreases.
  • the median diameter D50 of silica has an upper limit of preferably 24 ⁇ m, more preferably 23 ⁇ m, and a lower limit of preferably 14 ⁇ m, even more preferably 15 ⁇ m.
  • the D10 of silica is less than 1 ⁇ m, the proportion of micropores formed in the partition wall that deteriorates the pressure loss characteristics increases, which is not preferable.
  • the pore volume of the partition wall having a pore diameter of 1 ⁇ m or more and less than 4 ⁇ m becomes relatively small, and it becomes impossible to satisfy the range of more than 9.6% and 13% or less of the total pore volume, which is coarse.
  • the proportion of the fine pores increases, and it may not be possible to expect improvement in the strength of the ceramic honeycomb structure. Furthermore, it is not preferable because the proportion of coarse pores that reduce the nano-sized PM collection rate increases.
  • the upper limit of D10 of silica is preferably 4.5 ⁇ m, more preferably 4 ⁇ m, and the lower limit is preferably 1.5 ⁇ m, further preferably 2.0 ⁇ m.
  • the D90 of silica is less than 30 ⁇ m, the proportion of micropores formed in the partition wall that deteriorates the pressure loss characteristics increases, which is not preferable. On the other hand, if it exceeds 40 ⁇ m, the proportion of coarse pores that lowers the nano-sized PM collection rate and the strength of the ceramic honeycomb structure increases, which is not preferable.
  • the upper limit of D90 of silica is preferably 39.5 ⁇ m, and the lower limit is preferably 21 ⁇ m, more preferably 22 ⁇ m.
  • the proportion of silica having a particle size of 10 ⁇ m or less is less than 20% by mass, the pore volume of the partition wall having a pore diameter of 1 ⁇ m or more and less than 4 ⁇ m becomes relatively small, exceeding 9.6% of the total pore volume and 13% or less. In some cases, it becomes impossible to satisfy the above range, the proportion of coarse pores increases, and improvement in the strength of the ceramic honeycomb structure cannot be expected. Furthermore, it is not preferable because the proportion of coarse pores that reduce the nano-sized PM collection rate increases. On the other hand, if it exceeds 35% by mass, the proportion of micropores in the pores formed in the partition wall increases, which causes an increase in pressure loss when PM is collected and accumulated.
  • the upper limit of the proportion of silica particles having a particle size of 10 ⁇ m or less is preferably 34 ⁇ m, more preferably 33 ⁇ m, and the lower limit is preferably 21 ⁇ m, further preferably 22 ⁇ m.
  • the proportion of silica having a particle size of 100 ⁇ m or more exceeds 2% by mass, the number of coarse pores increases and the nano-sized PM collection rate decreases.
  • the proportion of silica having a particle size of 100 ⁇ m or more is preferably 1.8% by mass or less, more preferably 1.5% by mass or less.
  • the particle size distribution deviation SD2 exceeds 0.65, the proportion of coarse pores that reduce the nano-sized PM collection rate increases, which is not preferable. On the other hand, if it is less than 0.40, the proportion of micropores in the pores formed in the partition wall increases, which causes an increase in pressure loss when PM is collected and accumulated.
  • the upper limit is preferably 0.64, more preferably 0.63, and the lower limit is preferably 0.42, even more preferably 0.44.
  • the sphericity of the silica is preferably 0.5 or more. When the sphericity of silica is less than 0.5, the number of pores having acute-angled portions, which are likely to be the starting points of fracture, may increase and the strength of the honeycomb structure may decrease, which is not preferable.
  • the sphericity of silica is preferably 0.6 or more, and more preferably 0.7 or more.
  • the sphericity of a silica particle is a value obtained by dividing the projected area of the silica particle by the area of a circle whose diameter is the maximum value of a straight line connecting two points on the outer circumference of the particle through the center of gravity of the silica particle. It can be obtained with an image analyzer.
  • silica a crystalline one or an amorphous one can be used, but an amorphous one is preferable from the viewpoint of adjusting the particle size distribution.
  • Amorphous silica can be obtained by pulverizing an ingot produced by melting high-purity natural silica stone at a high temperature.
  • Silica may contain Na 2 O, K 2 O, and Ca O as impurities, but the total content of the impurities is preferably 0.1% or less in order to prevent the coefficient of thermal expansion from becoming large.
  • Silica with high sphericity is obtained by finely pulverizing high-purity natural silica stone and spraying it into a high-temperature flame.
  • Amorphous silica with high sphericity can be obtained by simultaneously melting and spheroidizing silica particles by spraying into a high-temperature flame. Further, it is preferable to adjust the particle size of the spherical silica by a method such as classification.
  • Kaolin Kaolin contains 1 to 13% by mass. If kaolin is contained in an amount of more than 13% by mass, it may be difficult to adjust the pore volume of less than 1 ⁇ m to 1.7 to 4.0% of the total pore volume in the pore distribution of the ceramic honeycomb structure. If it is less than% by mass, the coefficient of thermal expansion of the ceramic honeycomb structure becomes large.
  • the kaolin content is preferably 4-8% by mass.
  • the plate-like crystal of kaolin undergoes a rectifying action when passing through a mold during extrusion molding, and the c-axis of the crystal is oriented perpendicularly to the partition surface of the honeycomb structure.
  • the c-axis which has a negative thermal expansion in the direction perpendicular to the c-axis of the kaolin crystal, grows in the cordierite crystal, and the coefficient of thermal expansion of the honeycomb structure can be reduced. Therefore, the shape of kaolin has a great influence on the orientation of kaolin.
  • the cleavage index of kaolin which is an index that quantitatively indicates the shape of kaolin, is preferably 0.80 or more, and more preferably 0.85 or more.
  • Talc Talc contains 40-43% by mass.
  • the talc one having a median diameter D50 of 5 to 15 ⁇ m is used.
  • the particle size D10 at the cumulative volume corresponding to 10% of the total volume is 10 ⁇ m or less, and similarly. It is preferable to use a talc having a particle size D90 of 25 ⁇ m or more in a cumulative volume corresponding to 90% of the total volume.
  • Talc is a compound containing MgO and SiO 2 as main components, and is known to react with the surrounding Al 2 O 3 components and melt to form pores during the firing process.
  • talc having a small particle size together with the Al 2 O 3 source raw material, a large number of small diameter pores can be dispersed in the partition wall, and the communication of the pores in the partition wall can be improved.
  • the median diameter D50 of talc is less than 5 ⁇ m, the communication of pores is low, and the pressure drop characteristic when PM is collected and accumulated is lowered.
  • the median diameter D50 of talc exceeds 15 ⁇ m, the number of coarse pores increases and the nano-sized PM collection rate decreases.
  • the median diameter D50 of talc is preferably 6 to 14 ⁇ m, more preferably 8 to 13 ⁇ m.
  • the D10 of talc is more preferably 8 ⁇ m or less, still more preferably 7 ⁇ m or less.
  • the D90 of talc is more preferably 25 to 45 ⁇ m, still more preferably 25 to 40 ⁇ m or less.
  • Talc is preferably plate-like particles from the viewpoint of reducing the coefficient of thermal expansion of the ceramic honeycomb structure in which the main component of the crystal phase is cordierite.
  • the view factor indicating the flatness of talc is preferably 0.5 or more, more preferably 0.6 or more, and most preferably 0.7 or more.
  • Talc may contain Fe 2 O 3 , Ca O, Na 2 O, K 2 O and the like as impurities.
  • the content of Fe 2 O 3 is preferably 0.5 to 2.5% by mass in the raw material of the magnesia source in order to obtain a desired particle size distribution, and the content of Na 2 O, K 2 O and Ca O is thermally expanded. From the viewpoint of lowering the coefficient, the total amount is preferably 0.5% by mass or less.
  • Alumina contains 15 to 30% by mass.
  • As the alumina one having a median diameter D50 of 3 to 6 ⁇ m is used.
  • the particle size D90 in the cumulative volume corresponding to 90% of the total volume is 20 ⁇ m or less, and the proportion of particles having a particle size of 25 ⁇ m or more is 0.4% by mass or less. It is preferable to use alumina.
  • alumina By blending alumina having such a median diameter and particle size distribution, a large number of small-diameter pores can be dispersed in the partition wall, so that the communication of the pores in the partition wall can be improved. It contributes to the formation of the pore distribution of the ceramic honeycomb structure of the present invention.
  • the upper limit of the median diameter D50 of alumina is more preferably 5.5 ⁇ m, and the lower limit is even more preferably 3.5 ⁇ m.
  • the upper limit of D90 is preferably 19 ⁇ m, more preferably 18 ⁇ m, and the lower limit is preferably 1 ⁇ m, further preferably 3 ⁇ m.
  • the proportion of particles having a particle size of 25 ⁇ m or more is preferably 0.3% by mass or less.
  • As a raw material having an alumina source component it is preferable to use aluminum hydroxide in addition to alumina.
  • the total content of the impurities Na 2 O, K 2 O and Ca O in alumina and aluminum hydroxide is preferably 0.5% by mass or less, more preferably 0.3% by mass or less, and most preferably 0.1% by mass or less. ..
  • Pore-forming material used in the present invention is composed of hollow resin particles, and the amount added thereof is 1 to 8 parts by mass with respect to 100 parts by mass of the ceramic raw material powder. If the amount of the pore-forming material added is out of this range, it becomes difficult to obtain a partition wall having the pore structure. When the amount of the pore-forming material added is less than 1% by mass, it becomes difficult to obtain a partition wall having a porosity of 52% or more, so that the pressure loss characteristic when PM is collected and accumulated deteriorates. If the amount of the pore-forming material added exceeds 8% by mass, the porosity of the partition wall may exceed 63%, and the nano-sized PM collection rate decreases.
  • the upper limit of the amount of the pore-forming material added is preferably 7 parts by mass, more preferably 6 parts by mass, even more preferably 5.4 parts by mass, most preferably 5 parts by mass, and the lower limit is preferably 1.5 parts by mass. More preferably, it is 2 parts by mass.
  • the median diameter D50 of the pore-forming material is 20 to 55 ⁇ m. If the median diameter D50 is less than 20 ⁇ m, the low pressure loss when PM is collected and accumulated cannot be maintained. When the median diameter D50 exceeds 55 ⁇ m, the pores formed become coarse, so that the nano-sized PM collection rate decreases.
  • the upper limit of the median diameter D50 of the pore-forming material is preferably 53 ⁇ m, more preferably 50 ⁇ m, and the lower limit is preferably 25 ⁇ m, further preferably 30 ⁇ m.
  • the upper limit of the particle size D10 in the cumulative volume corresponding to 10% of the total volume is preferably 28 ⁇ m, more preferably 26 ⁇ m, and the lower limit is 17 ⁇ m, further preferably 19 ⁇ m.
  • the upper limit of the particle size D90 in the cumulative volume corresponding to 90% of the total volume is preferably 77 ⁇ m, more preferably 75 ⁇ m, and the lower limit is preferably 63 ⁇ m, further preferably 65 ⁇ m.
  • the upper limit of the particle size distribution deviation SD1 is preferably 0.33, more preferably 0.32, and the lower limit is preferably 0.22, further preferably 0.23. Further, it is preferable that the particle size D5 in the cumulative volume corresponding to 5% of the total volume is 10 to 25 ⁇ m, and the particle size D95 in the cumulative volume corresponding to 95% of the total volume is 70 to 95 ⁇ m. In addition, D5 ⁇ D10 ⁇ D20 ⁇ D50 ⁇ D80 ⁇ D90 ⁇ D95.
  • the particle size of the pore-forming material can be measured using a Microtrack particle size distribution measuring device (MT3000) manufactured by Nikkiso Co., Ltd.
  • the sphericity of the pore-forming material is preferably 0.5 or more. When the sphericity of the pore-forming material is less than 0.5, the number of pores having acute-angled portions, which are likely to be the starting points of fracture, may increase and the strength of the honeycomb structure may decrease, which is not preferable.
  • the sphericity of the pore-forming material is preferably 0.7 or more, and more preferably 0.8 or more.
  • the sphericity of the pore-forming material is the value obtained by dividing the projected area of the pore-forming material by the area of a circle whose diameter is the maximum value of a straight line that passes through the center of gravity of the pore-forming material and connects two points on the outer circumference of the particle. , Can be obtained from an electron micrograph with an image analyzer.
  • Foamed resin particles are preferable as the hollow resin particles.
  • the resin used as the pore-forming material (poly) methyl methacrylate, polybutyl methacrylate, polyacrylic acid ester, polystyrene, polyacrylic ester, polyethylene, polyethylene terephthalate, methyl methacrylate / acrylonitrile copolymer and the like are suitable.
  • Hollow resin particles have an outer shell thickness of 0.1 to 3 ⁇ m, contain a gas such as a hydrocarbon, contain 70 to 95% of water on the surface of the resin particles, and have a true specific gravity of 0.01 to 0.05. It is preferable to use one.
  • a binder is added to the ceramic raw material powder and the pore-forming material and mixed in a dry manner, and then water and, if necessary, additives such as a dispersant and a surfactant are added.
  • the plastic clay obtained by kneading is extruded from a mold for forming a honeycomb structure by a known extrusion molding method, for example, an extrusion molding method such as a plunger type or a screw type. Is formed, and after the molded body is dried, the end face and the outer periphery are processed as necessary, and the molded body is fired.
  • a known extrusion molding die is used as the honeycomb structure molding die, but the following is used for molding a ceramic honeycomb structure having a fan-shaped convex portion at a partition wall intersection of the ceramic honeycomb structure.
  • the mold 20 is formed at the corners of the four mold members 26a, 26b, 26c, and 26d at the slit intersection 23 where the grid-like slits 21 intersect in the extruded direction. It has arcuate recesses 24a, 24b, 24c and 24d.
  • the radius of the inscribed circle 24 inscribed in these arcuate recesses 24a, 24b, 24c, 24d is the intersection of all the slits of the mold 20. It is configured to be constant in the part.
  • FIG. 8 (c) the mold 20 is manufactured by separating the center point Ca of the inscribed circle 24 and the center point Cs of the slit intersection 23 by a distance Sd.
  • the sizes of the arcuate recesses 24b and 24c can be increased, and in the example of FIG. 8C, the sizes of the arcuate recesses 24c and 24d can be increased.
  • Such a honeycomb forming die 20 is manufactured by first forming a supply hole 22, then forming a hole 240 on the opposite surface of the hole forming surface on which the supply hole 22 is formed, and then forming a slit 21. it can.
  • the center position of the hole 240 is the position of the center point Ca of the inscribed circle 24, and the four corners of the mold member at the slit intersection 23 of the honeycomb molding mold 20 are viewed in the extrusion direction.
  • a chamfered portion is formed in a concave shape.
  • the hole 240 and the slit 21 are provided so that the center position of the hole 240 (the position of the center point Ca of the inscribed circle 24) is separated from the position of the center point Cs of the slit intersection 23 by the distance Sd between the center points.
  • the hole 240 can be formed by drilling a hole while controlling the position of the hole, for example, using a drilling machine having a precise XY stage.
  • the image data of the optical microscope taken by observing with the optical microscope can be measured with an image measuring machine (Quick Vision manufactured by Mitutoyo Co., Ltd.).
  • Baking is performed using a continuous furnace or a batch furnace while adjusting the rate of temperature rise and cooling.
  • the ceramic raw material is a cordierite-forming raw material, it is kept at 1350 to 1450 ° C. for 1 to 50 hours, and after sufficient cordierite main crystals are formed, it is cooled to room temperature.
  • the temperature rise rate is a temperature range in which the binder decomposes (for example, when a large ceramic honeycomb structure having an outer diameter of 150 mm or more and a total length of 150 mm or more is manufactured, so that the molded body does not crack during the firing process).
  • Cooling is preferably performed at a rate of 20 to 40 ° C./h, especially in the range of 1400 to 1300 ° C.
  • the obtained honeycomb structure can be made into a ceramic honeycomb filter by sealing the end of a desired flow path by a known method.
  • this mesh sealing portion may be formed before firing.
  • Examples 1 to 5 and Comparative Examples 1 to 3 Silica, talc and alumina, aluminum hydroxide and kaolin having the particle shapes (particle size, particle size distribution, etc.) shown in Tables 1 to 5 are shown in Table 7 so that the total amount of the ceramic raw material powder is 100% by mass. The mixture was blended in an added amount to obtain a cordierite-forming raw material powder having a chemical composition of cordierite after firing.
  • the pore-forming material having the particle size distribution and the true specific gravity shown in Table 6 was added in the amount shown in Table 7, methyl cellulose was added and mixed, and then water was added and kneaded to achieve plasticity. Ceramic clay was prepared.
  • the sphericity of the pore-forming material particles is a circle whose diameter is the maximum value of the projected area A1 obtained from the image of the particles taken by an electron microscope and the straight line connecting the two points on the outer circumference of the particles through the center of gravity. It is a value calculated by the formula: A1 / A2 from the area A2 of, and is shown as an average value for 20 particles.
  • the particle size and particle size distribution of silica, talc, alumina, aluminum hydroxide, kaolin and pore-forming material were measured using a Microtrack particle size distribution measuring device (MT3000) manufactured by Nikkiso Co., Ltd.
  • the ratio of diameter 10 ⁇ m or less, the ratio of 25 ⁇ m or more, the ratio of 100 ⁇ m or more, D90, D80, D20, D10, etc. were determined.
  • Example 1 and Comparative Examples 1 and 2 R is formed at the slit intersection of the mold so that the shape of the partition wall intersection of the ceramic honeycomb structure is 100 ⁇ m at the corner R portion shown in FIG. 5 (a).
  • the mold was used.
  • the molds are formed so that the shape of the partition wall intersection has a protrusion height X of the fan-shaped convex portion shown in FIG. 5 (b) of 60 ⁇ m (0.2 times the wall thickness).
  • a mold manufactured by forming a slit so that the slit intersection coincides with the hole 240 was used.
  • the peripheral part is removed and processed, and the schedule is 210 hours in a firing furnace (10 ° C / h for room temperature to 150 ° C, 2 ° C / hr for 150 to 350 ° C, 20 ° C / h and 1150 for 350 to 1150 ° C).
  • a firing furnace (10 ° C / h for room temperature to 150 ° C, 2 ° C / hr for 150 to 350 ° C, 20 ° C / h and 1150 for 350 to 1150 ° C).
  • the outer circumference of the fired ceramic honeycomb is coated with an outer skin material composed of amorphous silica and colloidal silica and dried.
  • the outer diameter is 266.7 mm
  • the total length is 304.8 mm
  • the partition wall thickness is 12 mil (0.30 mm)
  • the cell density is 260.
  • Ceramic honeycomb structures of Examples 1 to 5 and Comparative Examples 1 to 3 having cpsi (40.3 cells / cm 2) were obtained.
  • the flow path ends of these ceramic honeycomb structures are filled with a sealant slurry made of a cordierite-forming raw material so as to be alternately sealed, and then the sealant slurry is dried and at 1400 ° C.
  • a sealant slurry made of a cordierite-forming raw material so as to be alternately sealed, and then the sealant slurry is dried and at 1400 ° C.
  • Each of the Codylite ceramic honeycomb filters of Examples and Comparative Examples was produced.
  • the length of the sealant after firing was in the range of 7 to 10 mm. Two identical ceramic honeycomb filters were made.
  • the pore distribution was measured by the mercury intrusion method, the coefficient of thermal expansion, and the A-axis compression fracture strength were measured by the following methods. Measurements were made.
  • a graph showing the relationship between the pore size and the cumulative pore volume was obtained.
  • the cumulative pore volume at a mercury pressure of 1800 psi (1.26 kg / mm 2 , equivalent to a pore diameter of about 0.1 ⁇ m) was defined as the total pore volume.
  • the total pore volume, porosity, and cumulative pore volume are 10% of the total pore volume, the pore diameter d10, 20%, and the fine pore diameter d20, 25%.
  • Porosity d25, 50% pore diameter (median pore diameter) d50, 75% pore diameter d75, 80% pore diameter d80, 85% pore diameter d85, 100 ⁇ m or more pore volume, 40 ⁇ m or more Porosity volume, pore volume of 30 ⁇ m or more, pore volume of 5 ⁇ m or more and less than 8 ⁇ m, pore volume of 1 ⁇ m or more and less than 4 ⁇ m, pore volume of less than 3 ⁇ m, pore volume of less than 2 ⁇ m, and pore volume of less than 1 ⁇ m ⁇ 1 log (d20) -log (d80), the difference between the log of the pore diameter d20 where the cumulative pore volume is 20% of the total pore volume and the log of
  • the difference ⁇ 2 log (d75) -log (d85) between the log of the pore diameter d75 where the pore volume is 75% of the total pore volume and the log of the pore diameter d85 where the pore volume is 85% was calculated.
  • the values of the pore diameters d10, d20, d25, d50, d75, d80 and d85 are interpolated with the two measurement points before and after the closest to each pore diameter among the measurement points obtained by the measurement of the mercury intrusion method. I asked for it. For example, in the case of d20, as shown in FIG.
  • A-axis compression fracture strength is 24.5 mm in diameter from the ceramic honeycomb structure in accordance with the standard M505-87 "Test method for ceramic monolith carrier for automobile exhaust gas purification catalyst" established by the Society of Automotive Engineers of Japan. And a sample piece with a length of 24.5 mm was collected. The A-axis compressive fracture strength was measured using 18 sample pieces taken from each ceramic honeycomb structure, the average value of them was calculated, and the value of Comparative Example 1 was set to 1.0 and shown as a relative value. The results are shown in Table 10.
  • PM collection rate based on the number of particles at the initial stage of collection is a ceramic honeycomb filter fixed to the pressure loss test stand, and the air flow rate is 10 Nm 3 At / min, while adding combustion soot with an average particle size of 0.11 ⁇ m at a rate of 1.3 g / h, the number of combustion soot particles flowing into the honeycomb filter and the number of combustion soot particles flowing out of the honeycomb filter every minute. Is measured using SMPS (Scanning Mobility Particle Sizer) (TIS model 3936), and the number of particles of combustion soot flowing into the honeycomb filter in 1 minute from 40 minutes to 41 minutes after the start of injection, and the honeycomb filter.
  • SMPS Sccanning Mobility Particle Sizer
  • the ceramic honeycomb filters of the present invention of Examples 1 to 5 have a PM collection rate that effectively collects nano-sized PM, which greatly affects the number of particles in the exhaust gas, as compared with Comparative Examples 1 to 3. It can be seen that the strength is improved while maintaining good pressure loss characteristics when PM is collected and accumulated.
  • the ratio of the pore volume having a pore diameter of 5 ⁇ m or more and less than 8 ⁇ m was 12.5%.
  • the strength of the ceramic honeycomb structure is low because it exceeds the specified range (8 to 12%).
  • the ratio of the pore volume of 40 ⁇ m or more and the ratio of the pore volume of 30 ⁇ m or more are 5.1 and 6.6, respectively, which exceed the specified range of the present invention (4.2 to 5.0% and 5.8 to 6.5%, respectively).
  • the ratio of the pore volume of 1 ⁇ m or more and less than 4 ⁇ m is 8.5%, which is below the specified range of the present invention (more than 9.6% and less than 13%), so that the strength of the ceramic honeycomb structure is low and the PM collection rate is low. Low.
  • the ceramic honeycomb structure of Comparative Example 2 has a pore volume of 100 ⁇ m or more, a pore volume of 40 ⁇ m or more, and a fineness of 30 ⁇ m or more, although the pressure loss when PM is collected is well maintained.
  • the pore volume (3.4%, 6.3% and 8.4%, respectively) exceeds the specified range of the present invention (2.2 to 3.0%, 4.2 to 5.0% and 5.8 to 6.5%, respectively), and the fineness of 5 ⁇ m or more and less than 8 ⁇ m.
  • the pore volume, the pore volume of 1 ⁇ m or more and less than 4 ⁇ m, the pore volume of less than 3 ⁇ m, and the pore volume of less than 2 ⁇ m (7.8%, 6.3%, 6.0%, and 3.7%, respectively) are within the specified range of the present invention (respectively, respectively. Since it is 8 to 12%, more than 9.6% and 13% or less, 8 to 12% and 4.5 to 7.0%), the strength of the ceramic honeycomb structure is not improved and the PM collection rate is low.
  • the ceramic honeycomb structure of Comparative Example 3 has a pore volume of 100 ⁇ m or more, a pore volume of 40 ⁇ m or more, and a pore volume of 30 ⁇ m or more (2.1%, 4.1%, and 5.7%, respectively). Is below the specified range of the present invention (2.2 to 3.0%, 4.2 to 5.0% and 5.8 to 6.5%, respectively), so that the pressure loss when PM is collected is not well maintained.
  • the ratio of the pore volume having a pore diameter of 5 ⁇ m or more and less than 8 ⁇ m is 7.6%, which is lower than the specified range (8 to 12%) of the present invention, an improvement effect can be seen in terms of strength, but the fineness of 5 ⁇ m or more and less than 8 ⁇ m is observed.
  • the proportion of the pore volume is too low, and the pore volume of 1 ⁇ m or more and less than 4 ⁇ m, the pore volume of less than 3 ⁇ m, and the pore volume of less than 2 ⁇ m (8.8%, 7.6%, and 4.4%, respectively) are defined in the present invention.
  • the PM collection rate is low because it is below the range (more than 9.6% and less than 13%, 8-12% and 4.5-7.0%, respectively).

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Ceramic Engineering (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Organic Chemistry (AREA)
  • Materials Engineering (AREA)
  • Structural Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Combustion & Propulsion (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Geology (AREA)
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Abstract

Cette structure en nid d'abeilles en céramique a un grand nombre de chemins d'écoulement qui sont séparés par des parois de séparation poreuses et sont formés dans une direction axiale : les parois de séparation ayant (a) une porosité de 52 à 63 % et (b) dans une distribution de pores fins mesurée par un procédé de pénétration de mercure et par rapport à l'ensemble du volume de pores fins, le volume de pores fins ayant un diamètre de pores fins supérieur ou égal à 100 µm représente de 2,2 à 3,0 % ; le volume de pores fins ayant un diamètre de pores fins supérieur ou égal à 40 µm représente de 4,2 à 5,0 % ; le volume de pores fins ayant un diamètre de pores fins supérieur ou égal à 30 µm représente de 5,8 à 6,5 % ; le volume de pores fins ayant un diamètre de pores fins supérieur ou égal à 5 µm mais inférieur à 8 µm représente de 8 à 12 % ; le volume de pores fins ayant un diamètre de pores fins supérieur ou égal à 1 µm mais inférieur à 4 µm représente plus de 9,6 % mais pas plus de 13 % ; le volume de pores fins ayant un diamètre de pore fin inférieur à 3 µm représente de 8 à 12 % ; le volume des volumes de pores fins ayant un diamètre de pores fins inférieur à 2 µm représente de 4,5 à 7,0 % ; le volume de pores fins ayant un diamètre de pores fins inférieur à 1 µm représente 1,7 à 4,0 % ; le diamètre de pore fin d10 auquel le volume de pores fins cumulatif devient 10 % est de 18 à 22 µm ; le diamètre de pore fin d25 auquel le volume de pores fins cumulatif devient de 25 % est de 13,0 à 15,5 µm ; le diamètre de pore fin (diamètre moyen de pore fin) d50 à laquelle le volume de pores fins cumulé devient de 50 % est de 10-13 µm ; le diamètre de pore fin d75 auquel le volume de pores fins cumulatif devient 75 % est de 6 à 9 µm ; et σ1=log(d20)-log(d80), qui est la différence entre le logarithme du diamètre de pore fin d20 à laquelle 20 % est obtenu et le logarithme du diamètre de pore fin d80 à laquelle 80 % est obtenu, n'est pas supérieur à 0,45.
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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2010013509A1 (fr) * 2008-07-28 2010-02-04 日立金属株式会社 Structure en nid d'abeilles en céramique et son procédé de fabrication
WO2015046012A1 (fr) * 2013-09-24 2015-04-02 日立金属株式会社 Structure céramique en nid d'abeilles et son procédé de production
JP2015071165A (ja) * 2010-04-01 2015-04-16 日立金属株式会社 セラミックハニカムフィルタの製造方法
JP2019171318A (ja) * 2018-03-29 2019-10-10 日本碍子株式会社 ハニカムフィルタ

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2010013509A1 (fr) * 2008-07-28 2010-02-04 日立金属株式会社 Structure en nid d'abeilles en céramique et son procédé de fabrication
JP2015071165A (ja) * 2010-04-01 2015-04-16 日立金属株式会社 セラミックハニカムフィルタの製造方法
WO2015046012A1 (fr) * 2013-09-24 2015-04-02 日立金属株式会社 Structure céramique en nid d'abeilles et son procédé de production
JP2019171318A (ja) * 2018-03-29 2019-10-10 日本碍子株式会社 ハニカムフィルタ

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