Ngk Insulators, Inc.

Wataru Kotani

Kazuhiko Kumazawa

Yoshiyuki Kasai

Kyoko Makino

Yoshiro Ono

Yasushi Noguchi

Toshiyuki Hamanaka

Takehiko Watanabe

Kunikazu Hamaguchi

Yasuhiro Ito

Masaomi Kamiya

Kazuhiko Umehara

There are newly provided an index which quantitatively indicates shapes of kaolin particles, and a method of measuring the index. There is also provided a method of manufacturing a low-thermal-expansion honeycomb structure suitable for an application such as a car exhaust gas purifying catalyst carrier by use of the kaolin particles whose index is not less than a predetermined value. A certain amount of kaolin particlesare pressed and filled into a container, peak intensities of the kaolin particlesin (200), (020), and (002) faces are measured by X-ray diffraction, respectively, and a cleavage index of the kaolin particlesis calculated from the resultant measured values by the following equation (1):Cleavage index=(002)/[(200)+(020)+(002)]&#x2003;&#x2003;(Equation 1),wherein (200), (020), and (002) denote values of the peak intensities of the kaolin particles measured in the (200), (020), and (002) faces by the X-ray diffraction, respectively.

Method of manufacturing cordierite honeycomb structure including measuring cleavage index of kaolin particles

A process for producing a cordierite-based ceramic honeycomb structure, includes kneading raw materials for cordierite with a forming aid to obtain a raw material batch, subjecting the raw material batch to obtain a honeycomb structure, and subjecting the honeycomb structure to drying and firing in this order to obtain a ceramic honeycomb structure whose crystal phase is composed mainly of cordierite. The raw material batch contains 65% by weight or more of raw materials for cordierite, comprising talc, kaolin and aluminum hydroxide and having crystal water. The kaolin has an average particle diameter of 5 &mgr;or more and a BET specific surface area of 10 m,/g or less and is contained in the raw material batch in an amount of 10% or more by weight. Formability during extruding, particularly lubricity and shape stability, are improved, for producing cordierite-based ceramic honeycomb structure having thin partition walls and high cell density, and improved mechanical strength (isostatic fracture strength) and improved catalyst coatability.

Process for production of cordierite-based ceramic honeycomb structure

A honeycomb regenerator is constructed by (a) honeycomb structural bodies arranged in a high temperature portion, in which a temperature is over 1250&deg; C. during a normal operation, made of aluminum-titanate or a combination of aluminum-titanate and mullite, and (b) honeycomb structural bodies arranged in a low temperature portion, made of cordierite and/or mullite, or by (a) honeycomb structural bodies arranged in a high temperature portion, to which an exhaust gas having a high temperature is contacted, made of aluminum-titanate or a combination of aluminum-titanate and mullite, (b) honeycomb structural bodies arranged in a middle temperature portion made of alumina and (c) honeycomb structural bodies arranged in a low temperature portion made of one material or a combination of materials selected from a group of cordierite, mullite and a porcelain. The honeycomb regenerator according to the invention can perform a heat exchanging operation effectively even in an exhaust gas having a high temperature and also in an exhaust gas having a high temperature and a corrosive property.

Honeycomb regenerator

A production method of a cordierite ceramic honeycomb structure is provided. 0.1 to 2% by weight of a nonionic polyether lubricant, obtained by adding ethylene oxide and propylene oxide to polyhydric alcohol with an ethylene oxide:propylene oxide ratio of 10:90 to 100:0 by weight, is added to the cordierite material batch for extruding. The honeycomb structure has a thin partition wall, and is suitable for the mass production by improving the formability (in particular, the lubricity and the shape stability) in extruding.

Production method of cordierite ceramic honeycomb structure

A honeycomb regenerator for receiving a waste heat in an exhaust gas by passing an exhaust gas and a gas to be heated alternately therethrough, which is constructed by stacking a plurality of honeycomb structural bodies, is disclosed. In the honeycomb regenerator according to the invention, cell open rates of the honeycomb structural bodies positioned at an inlet portion of the exhaust gas and at an inlet portion of the gas to be heated are larger than those of the honeycomb structural bodies positioned at a center portion.

A method of firing ceramic honeycomb structural bodies, in which cordierite raw materials including at least raw kaolin is extruded to obtain a honeycomb structural formed body and the thus obtained honeycomb structural formed body is fired. The method includes the step of firing a honeycomb structural body having a rib thickness of not more than 4.6 mil under such a condition that a temperature ascending rate during 400-600.degree. C. is maintained under 70.degree. C./hr. As a preferred embodiment, a temperature ascending rate during 400-600.degree. C. is defined as under 70.degree. C./hr in the case of manufacturing a honeycomb structural body having a rib thickness of 4.6-4.0 mil, or, a temperature ascending rate during 400-600.degree. C. is defined as under 40.degree. C./hr in the case of manufacturing a honeycomb structural body having a rib thickness of 3.9-2.0 mil.

Method of firing ceramic honeycomb structural bodies

A honeycomb regenerator for recovering waste heat from exhaust gas, comprises a stacked assembly including at least one first honeycomb body and at least one second honeycomb body stacked thereon, the first honeycomb body being formed of an anti-corrosive material, and the at least one second honeycomb body being formed of a material having a main phase of cordierite. The stacked assembly has an inlet for hot gas and an inlet for cold gas, such that the cold gas flows along a direction opposite the hot gas. Further, the at least one second honeycomb body is provided downstream of the at least one first honeycomb body along a gas flow direction of the hot gas. Accordingly, the at least one first honeycomb body receives the hot gas during flow thereof, while the at least one second honeycomb body receives the cold gas during flow thereof.

A production method of a honeycomb structure is provided. The production method of a thin wall cordierite honeycomb structure having cordierite as the main component of the crystalline phase includes: adding a forming auxiliary agent to a cordierite material to obtain a mixture, kneading the mixture to obtain a material batch, forming the material batch by extrusion to form a honycomb compact, drying the honeycomb compact to obtain a dried body, and firing the dried body. The cordierite material batch contains 65% by weight or more flat plate-like cordierite raw material including crystal water made from talc, kaolin and aluminum hydroxide with the BET specific surface areas for the cordierite raw materials being 7 to 18 m.sup.2 /g of talc, 14 to 22 m.sup.2 /g of kaolin and 6 to 18 m.sup.2 /g of aluminum hydroxide. The method can realize a thinner wall and a higher cell density and can improve the formability (in particular, the lubricity and the shape stability) at the time of extruding, the mechanical strength (hydrostatic pressure fracture strength), and the catalyst carrying characteristics.

Production method of thin wall cordierite honeycomb structure

A production method of a cordierite ceramic honeycomb structure is provided. Clay mineral, which is one component in the cordierite material batch for extruding, contains dickite and at least one selected from the group consisting of kaolinite and halloysite, with a 5 to 50% by weight dickite amount in the clay mineral. The honeycomb structure has a thin partition wall, and is suitable for the mass production by improving the formability (in particular, the lubricity and the shape stability) in extruding and by preventing crack generation in the firing process.

A ceramic honeycomb structure is disclosed which includes a ceramic honeycomb body having a matrix of partition walls forming a multiplicity of cells extending in an axial direction of the honeycomb body. The radially outermost array of the cells are open to an outside of the honeycomb body in radial directions thereof, to provide a plurality of grooves formed in an outer periphery of the honeycomb body to extend in the axial direction. The honeycomb structure further includes an outer coating which fills at least the grooves to cover the outer periphery of the ceramic honeycomb body, so as to provide an outer surface of the honeycomb structure. Also disclosed are a process of producing such a honeycomb structure, and a coating material used for forming the outer coating as described above.

Ceramic honeycomb structure with grooves and outer coating, process of

Cordierite honeycomb ceramics comprises a cordierite phase as a main ingredient. A value of [Fe.sub.2 O.sub.3 wt %/(MgO wt %+Fe.sub.2 O.sub.3 wt %)].times.100 is 2-10, where a ferric component is calculated as Fe.sub.2 O.sub.3. A thermal expansion coefficient of the cordierite honeycomb ceramics is less than 0.5.times.10.sup.-6 /.degree. C. within a temperature range of 40.degree.-800.degree. C. in a direction parallel to a flow passage of a honeycomb body. In the cordierite honeycomb ceramics including a ferric component, a ferric component is added from a talc as raw materials. The cordierite honeycomb ceramics having a low thermal expansion coefficient is obtained by mixing raw materials for cordierite generation to obtain a batch, extruding the batch into a honeycomb formed body, drying the honeycomb formed body, and firing the dried honeycomb formed body at a temperature range of 1350.degree.-1450.degree. C. After that, the sintered honeycomb body is immersed in an acid solution if necessary.

Cordierite honeycomb ceramics and method producing the same

A cordierite ceramic filter is formed by mixing cordierite powders having a porosity of more than 30% as aggregate with raw materials for cordierite generation, poring agents, forming agents and solvents to obtain a ceramic batch, extruding the ceramic batch into a honeycomb shape to obtain a formed body, and firing the formed body. The cordierite ceramic filter has a mean pore size in a range of aggregate mean size.times.0.15.+-.5 .mu.m, has a porosity of more than 30% and has a compressive strength more than 100 kgf/cm.sup.2 in a direction parallel to a flow passage. The cordierite ceramic filter has an excellent filter regeneration function, has a high mechanical strength and is light and compact.

Cordierite ceramic filter

A porous ceramic filter has properties such that a porosity of the filter is more than 45% and less than 60%, a volume of pores having a pore size of less than 40 .mu.m is more than 60% of total volume of pores of the ceramic filter and an inequality of 1000M+85N.gtoreq.530 is satisfied, wherein M (m.sup.2 /g) is a specific surface of total pores continued from a surface to an inner portion of the filter and N (.mu.m) is a surface roughness of a surface of the filter. Preferably, the porous ceramic filter has a thermal expansion coefficient of less than 0.5.times.10.sup.-6 /.degree.C. within a temperature range of 40.degree..about.800.degree. C. in a direction parallel to a flow passage of the filter. The porous ceramic filter according to the invention is preferably used for eliminating soots in an exhaust gas from a diesel engine, and has a long operating time and requires less frequent filter regenerations.

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Kasugai, Japan

Wataru Kotani