• 专利附录
  • 专利说明
  • 权利要求
  • 类似技术
  • 同族专利
  • 引用文献
  • 法律状态
  • 优先权
    • 专利摘要:
    It is proposed a porous honeycomb structural body capable of satisfying a loss of pressure and isostatic resistance which are mutually contradictory properties simultaneously and a method for making it. In a porous honeycomb structural body having partition walls which contain cordierite as the main crystalline phase and have a porosity of 40 to 75% and an average pore diameter of 10 to 50 μm, the porosity and the Average pore diameter in a central portion of the honeycomb structural body is made larger than the porosity and the average pore diameter in a peripheral portion of the honeycomb structural body.
    公开号:BE1018254A3
    申请号:E2003/0039
    申请日:2003-01-17
    公开日:2010-08-03
    发明作者:Yasushi Noguchi；Yukihisa Wada；Yumi Muroi
    申请人:Ngk Insulators Ltd；
    IPC主号:
    专利说明:

    DESCRIPTION
    POROUS POROUS STRUCTURE BODY, USE THEREOF, AND PROCESS FOR PRODUCING THE SAME
    The present invention relates to a porous honeycomb structural body for use and method of manufacture, and more specifically to a porous / honeycomb structural body having a loss. reduced pressure, while maintaining isostatic resistance by controlling the dissolution of the porosity and a pore diameter of the structural body, its use is a method for manufacturing the structural body. bee of the present invention may be preferably used especially as a particulate filter for purifying the exhaust gas, and a carrier for a catalyst.
    Description of the Related Art (0002) Recently, the influence of particulate matter and NOx discharged from an automotive engine, especially a diesel engine or the like on the environment has gained increasing attention. As a result, much research and development has been done on the use of a porous honeycomb structural body as an important means for collecting and removing such deleterious substances.
    (0003) For example, a honeycomb structure body is being developed to collect and remove particulate matter in the exhaust gas by establishing exhaust gas flow in individual passage holes having openings at one of the end faces of the honeycomb structural body including a plurality of through holes which are separated by porous partition walls and whose openings on an end face where the exhaust gas flow and an end face where the exhaust gas out are closed alternately and forcing it through these partition walls. Development work is also underway, as a new approach, to improve the purity of such substances, to provide a catalyst consisting of a honeycomb structural body being composed of a porous structure, all of which have high porosity partition walls on which catalysts for HC and NOx compounds are charged in a relatively larger amount.
    (0004) On the use of such a porous honeycomb structure body, it is received in a metal cabinet or the like by means of a support with a fixed pressure force so that the nest structure body bee should not be moved into the metal case during continuous vibration of an engine or the like. As a result, the structural body must have isostatic resistance that allows the structural body to withstand the pressure force. Specifically, an attempt has been made to make the porosity of the honeycomb structural body higher, meeting the demands in reducing pressure loss for lower fuel consumption and high output torque, or requests for increasing the amount of catalyst charged for improving the purification ability. Accordingly, it is strongly desired to have a honeycomb structural body provided with sufficient isostatic resistance, while satisfying the demands for rendering the porosity in the honeycomb structure body higher. In this case, in the case of a honeycomb structural body installed in the exhaust path, the exhaust flow volume in the central part of the honeycomb structural body bee is associated with the perpendicular direction of the path for the exhaust gases. Thus, the flowability of the exhaust gases and the amount of HC, NOx compounds or the like in the central portion of the honeycomb structural body have a complete influence on the overall pressure loss and the purification ability. As a result, the development of honeycomb structural bodies and catalyst bodies having a structure capable of taking into account distribution differences in the flowing gases has long been desired.
    (0005) It has been proposed as porous honeycomb structural body of the prior art to achieve the above mentioned objectives a porous honeycomb structural body having a prolonged durability time for collecting particulate matter with a reduced frequency of regeneration treatment by constituting the honeycomb structural body to have "a porosity of 45 to 60%, pores with a block pore diameter of 100 μm or more in a volume which corresponds to 10 % or less of a total volume of all pores, and a relationship between a total of specific surfaces (Mm2 / g) of all pores opening on the surface of the honeycomb structure body and penetrating the body honeycomb structure inward, and a surface roughness (Npm) on the surface of the honeycomb structural body of Ι, ΟΟΟΜ + 85N> 530 "(see Japanese Patent No. 2,726 616).
    (0006) In addition, there is disclosed a porous ceramic honeycomb structural body having a significantly extended collection time with the same collection efficiency and the same pressure loss, having a "porosity of 40 to 55 and a total pore volume having a diameter of 2 μm or less being 0.015 cc / g or less (see Japanese Patent No. 2,578,176).
    (0007) In addition, a cordierite honeycomb structure having a high collection rate, low pressure loss and low coefficient of thermal expansion simultaneously having a thermal expansion coefficient of between 25 ° C and 800 ° C. ° C of 0.3x10'6 / ° C or lower, 55-80% porosity, 25-40μm average pore diameter, and small pores each 5-40μm in diameter and pores of large size each having a diameter of 40 to 100 μm as pores on the surfaces of the partition walls, the number of small pores being 5 to 40 times larger than the number of large pores "is also described (JP document -A-9-77573).
    (0008) However, with regard to any of these honeycomb structural bodies, no consideration has ever been given to the simultaneous satisfaction of such a feature such as the reduction of pressure loss. and obtaining increased isostatic resistance, which are mutually contradictory by controlling the pore distribution.
    SUMMARY OF THE INVENTION
    (0009) The present invention has been considered in view of the problems mentioned above. An object of the present invention is to provide a porous honeycomb structural body capable of simultaneously satisfying the characteristics of loss of pressure and isostatic resistance, which are mutually contradictory properties, suitable for use particularly in an apparatus for exhaust gas treatment installed in combustion equipment and which is usable, for example, for a structural body for collecting and removing particulates contained in the exhaust, or a catalyst body for decomposing HC, NOx and the like to remove them, and likewise for a process for making the porous honeycomb structural body.
    (0010) Intensive studies have been carried out to solve the problems mentioned above. As a result, first, it has been found that firing shrinkage of a honeycomb molded article containing a raw material forming cordierite as the main component and carbon as a pore forming agent becomes extremely obvious when the production temperature of the molded article within a temperature of 1000 to 1200 ° C, but the baking removal of the molded article hardly occurs when the temperature of the molded article is at outside the temperature range of 1000 to 1200 ° C previously mentioned.
    (0011) Next, further studies were made and found that a honeycomb structural body having a large pore diameter and porosity in a central portion which greatly influences a reduction in pressure loss can obtained by using carbon as a pore-forming agent and controlling a rate of temperature increase of the cooking environment so as to prevent the carbon existing in the central portion of the molded article from baking until the central portion of the molded article exceeds the previously mentioned temperature range. The present invention was completed on the basis of what has been found previously.
    (0012) That is, in accordance with the present invention, there is provided a porous honeycomb structural body having partition walls which contain cordierite as the main crystalline phase, a porosity of 40 at 75% and an average pore diameter of 10 to 50 μπι, in which the porosity and the pore diameter in the central part of the honeycomb structure body are larger than those in a peripheral part of the structural body honeycomb. In this specification, the phrase "core" refers to a midpoint of a central axis of a honeycomb structural body or molded article or partition wall portion which is closest to the midpoint, while the phrase "peripheral part" refers to the outermost part of the partition wall from a central midpoint of the nest structure body bee or article molded in a direction perpendicular to the central axis. In the honeycomb structural body of the present invention, the porosity and pore diameter are defined with respect to the "central portion". However, an area having a larger porosity and a larger diameter than the peripheral portion may have a certain diffusion area from the central portion. In addition, in this specification, the terms "porosity" and "pore diameter" mean mean porosity and average pore diameter, unless otherwise specified.
    (0013) In the present invention, the porosity in the central portion of the honeycomb structural body is preferably greater than the porosity in the peripheral portion of the honeycomb structure body of 2% or higher, more preferably 3% higher, and the pore diameter in the central portion of the honeycomb structural body is preferably larger than the pore diameter in the peripheral portion of the structural body honeycomb of 2 μm or more, more preferably 3 μm or more.
    (0014) In addition, in accordance with the present invention, there is also provided a method for making a porous honeycomb structural body which comprises the steps of preparing a molded article having a honeycomb structure by using a rootstock containing a raw cordierite forming material as a primary raw material and carbon in an amount of at least 5 parts by mass based on 100 parts by weight of the cordierite formation raw material and by drying and baking of the obtained molded article, wherein, on baking of the molded article, the temperature of the baking environment is increased at a rate at which the carbon existing in the central portion of the molded article is removed by cooking within a temperature range of 1200 ° C to below 1430 ° C in terms of temperature of the central portion of the molded article.
    (0015) In the present invention, it is preferable to increase the temperature of the cooking environment, depending on the type of carbon to be used, usually at a rate of 20 to 60 ° C / hr indoors a temperature range of 400 to 1150 ° C.
    (0016) Furthermore, the temperature of the cooking environment is preferably maintained within a temperature range of 1150 to 1200 ° C for at least 5 hours after the temperature reaches 1 150 ° C. ° C.
    (0017) Moreover, in the process for the manufacture of the present invention, the molded article having a honeycomb structure is preferably manufactured by use of a root ball containing at least carbon in one amount of 25 parts or less by weight based on 100 parts by weight of the raw cordierite formation material. In addition, the molded article having a honeycomb structure is more preferably manufactured by use of a lumen containing a malleable resin in an amount of 5 parts or less by mass based on 100 parts by mass of the raw material. of cordierite formation. Further, the atmosphere in the baking oven in which the molded article is baked is preferably set to an oxygen concentration of 7 to 17% by volume at least when the temperature of the baking environment is from 400 to 1150 ° C.
    (0018) Now, with reference to FIG. 1, a relationship between the rate of temperature increase and pore formation in a baking step in the process for the manufacture of the present invention will be described. Fig. 1 is a graph illustratively showing the state of the temperature of a cooking environment and the temperature of a central portion of the honeycomb structural body in a cooking step in an embodiment of the present invention. invention. In FIG. 1, a solid line represents the temperature of the central portion of the molded article and dashed lines represent the temperature of the cooking environment. In addition, the temperatures of the central portion of the molded article were measured by inserting an R-thermocouple into a through hole and attaching the R-thermocouple in the central portion of the molded article.
    (0019) As shown in FIG. 1 showing an example in which graphite is used as a carbon source, in the process for the manufacture of the present invention, when the temperature of the cooking environment * reaches a temperature at which the carbon contained as a pore forming agent can cook, ie about 600 ° C in FIG. 1, the temperature of a central portion of the molded article becomes higher than the surrounding temperature. This indicates that the carbon contained as a pore forming agent has begun to cook and that the temperature inside the molded article has accordingly been increased by it. When the temperature of the molded article reaches from 1000 to 1200 ° C by further increasing the surrounding temperature, the baking removal of the molded article comprising the raw cordierite forming material becomes the most troublesome, although such a phenomenon should not be apparent in the graph.
    (0020) At this point, if the carbon has already been removed by firing and the pores are already formed in the honeycomb structure, the pore diameter formed in the honeycomb structure is shrunk due to baking removal. However, if the carbon remains as in the example shown in FIG. 1, the cooking advances while maintaining the pore diameters at the diameter of the carbon. In addition, when the temperature of the molded article exceeds 1,200 ° C with an increase in the cooking environment temperature, the baking shrinkage of the molded article becomes low. In addition, if the carbon is completely removed by cooking at this time, edges substantially equal to the diameter originally possessed by the carbon are formed. The pores thus formed may have larger diameters compared with the pore diameter that has been formed as shrinkage due to the carbon bake emission below 1000 ° C.
    (0021) When the carbon in the molded article is removed by molding in a certain portion, the temperature of that portion of the molded article decreases rapidly to or below the environment temperature. That is, if this portion is the central portion of the molded article, the occurrence of a peak at a temperature ranging from 1200 to 1300 ° C can be observed, as shown in FIG. Fig. 1. That is, if an internal temperature of the molded article, to which such a sudden temperature change as mentioned above occurs, overlaps by 1000 to 1200 ° C of the temperature of the molded article. the environment in which the baking removal of the molded article is most troublesomely observed, the baking removal is accentuated. As a result, tears in the structure are observed due to cooking shrinkage.
    (0022) Therefore, in the present invention, since the above-mentioned peak temperature, i.e., the internal temperature of the molded article at the time the carbon was present in the central portion of the molded article is eliminated by cooking, is controlled to exceed 1200 ° C by controlling the rate of increase of the temperature of the cooking environment, the pores of the honeycomb structure being present in its central portion may have a diameter equal to that of the carbon having been present in the central part without causing tearing due to the withdrawal of cooking.
    (0023) In addition, the carbon is present in a peripheral portion of the molded article; said portion being in a more aerobic environment is removed by cooking more easily than the carbon present in a central portion including the central portion and is often removed by cooking at a relatively low temperature and forms pores. Thus, the diameters of these are often retracted due to subsequent cooking shrinkage. As a result, the pore diameter porosity difference between the central portion and the peripheral portion has often been observed.
    BRIEF DESCRIPTION OF THE DRAWINGS
    Fig. 1 is a graph illustrating how much the temperature of a central portion of a molded article and the temperature of a cooking environment has increased in a firing step in an embodiment of the present invention.
    Fig. 2 is a simplified explanatory view to show the sites at which the porosity and pore diameter of a porous honeycomb structural body were measured in the Examples and Comparative Examples.
    Fig. 3 is a graph illustrating how much the temperature of the central portions of the molded articles and the temperature of a cooking environment increased in baking steps in the Examples and Comparative Examples.
    Fig. 4 is a graph illustrating how much the temperature of the central portions of the molded articles and the temperature of a cooking environment increased in baking steps in the examples and in the comparative examples.
    Fig. 5 is a simplified explanatory view to show the sites at which the porosity and pore diameter of a porous honeycomb structural body in Example 1 were measured.
    Fig. 6 is a graph showing the results of measuring the porosity of the porous honeycomb structural body in Example 1 at various sites between the central portion and the peripheral portion.
    Fig. 7 is a graph showing the results of measuring the pore diameter of the porous honeycomb structural body in Example 1 at various sites between the central portion and the peripheral portion.
    DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
    (0024) An embodiment of the present invention will now be described in detail.
    1. Porous honeycomb structural body (0025) The present porous honeycomb structural body is directed to a porous honeycomb structural body having partition walls containing cordierite as a crystalline phase main and having a porosity of 40 to 75% and an average pore diameter of 10 to 50 μm, and a characteristic such that the porosity and mean pore diameter of the partition walls in the central portion of the nest structure body bees are larger than the porosity and pore diameter of the partition walls in the peripheral portion of the honeycomb structural body.
    (0026) Reduction of pressure loss and improvement of purity can be effectively achieved while maintaining the required isostatic strength when holding the honeycomb structural body in a cabinet. That is, a honeycomb structural body having greater isostatic strength and higher strength can be produced not only against rupture in the peripheral walls due to physical shock which may be applied to them by risk until the honeycomb structure body is received in a box, but also the shock due to the vibrations after reception in the box, compared with the one having the same pore diameter, but no practical difference in the pore diameter between the peripheral part and the central part, since the pore diameter and the porosity in the peripheral part are smaller than those in the central part.
    (0027) In the present invention, the porosity of the partition wall is adjusted within a range of 40 to 75%, since an increase in pressure loss is considerable when it is below 40%. % and, on the other hand, a reduction of the isostatic resistance is considerable when it exceeds 75%.
    For this reason, in the present invention, the porosities of all partition walls are preferably from 50 to 75%, more preferably from 57 to 70%, and still more preferably from 65 to 70%.
    (0028) In addition, in the present invention, the porosity of the partition walls in the central portion of the honeycomb structural body should be greater than the porosity of the partition walls in the peripheral portion of the body. with a honeycomb structure, preferably at least 2%, more preferably at least 3%, still more preferably at least 5% in terms of absolute value, with the effect that the reduction in the pressure loss becomes remarkable. That is, the porosity in the central portion is 52 to 72%, preferably 55 to 73%, more preferably 68 to 75%. As long as the porosity of the honeycomb structural body as a whole is within the aforementioned range, however, a small deviation from the previously mentioned figures due to the manufacturing conditions should always be found at within the allowable level in the present invention.
    (0029) Furthermore, in the present invention, how much the porosity changes from the peripheral portion to the central portion is not particularly limited. However, it is preferred that the porosity preferably changes continuously from the peripheral portion to the central portion. This is because a honeycomb structural body having a high thermal resistance and high impact resistance can be produced by continuously changing the porosity. Moreover, in this case, it is preferred that the amount of change of the porosity in the portion to the partition walls forming a series of cells placed at a position 1/3 of the distance from the outermost periphery to the outside to the central axis of the honeycomb structural body is preferably 30% or higher, particularly preferably 50% or more of the total amount of change in porosity between the outermost periphery and the center of the honeycomb structural body, from the point of view of the effective reduction of pressure loss.
    (0030) Furthermore, in the present invention, the average pore diameter of the partition walls is controlled within a range of 10 to 50 μm. This is because an increase in pressure loss is likely to occur previously due to pore clogging when the average pore diameter is below 10 μm, but a reduction in the efficiency of the collection of pore. particles becomes considerable when it exceeds 50 pm. For this reason, in the present invention, the average pore diameter of the partition walls is preferably 15 to 40 μm, more preferably 20 to 35 μm, and still more preferably 25 to 30 μm.
    (0031) In addition, in the present invention, the pore diameter of the partition walls in the central portion of the honeycomb structural body is greater than the pore diameter of the partition walls in the most peripheral portion. outside the honeycomb structural body, preferably at least 2 μm, more preferably at least 3 μm, still more preferably at least 5 μm. This is because the reduction effect becomes remarkable by constituting the pore diameter as mentioned above. That is, the pore diameter in the central portion is 12 to 52 μm, preferably 17 to 42 μm, more preferably 25 to 37 μm. As long as the average pore diameter of the honeycomb structural body as a whole is within the aforementioned range, however, a small deviation from the previously mentioned figures due to the manufacturing conditions should always occur. find within a level allowable in the present invention.
    (0032) Furthermore, in the present invention, there is no particular limitation on how the pore diameter changes from the peripheral portion to the central portion. However, it is preferred that the pore diameter continuously change from the peripheral portion to the central portion, since high heat resistance and high impact resistance can be achieved by doing this. In addition, in this case, it is preferable to change the average pore diameter in the portion between the partition walls of the outermost peripheral portion and the partition walls forming a series of placed cells. at a position 1/3 of the distance from the outermost periphery to the central axis of the honeycomb structural body 30% or greater than the change as a whole; more preferably make the change in this larger than preferable portion, still more preferably 50% or greater than the change as a whole, from the standpoint of the effective reduction of the pressure loss.
    (0033) In addition, in the present invention, the components of the partition wall are not particularly limited except that its essential component is cordierite. The cordierite may be oriented cordierite, unoriented cordierite, α-crystalline cordierite, β-crystalline cordierite, or the like.
    (0034) In addition, the partition walls may also contain other crystalline phases such as mullite, zirconia, aluminum titanate, clay-bonded silicon carbide, zirconia, spinel, indialite, sapphire, corundum and titanium. These crystalline phases can be contained alone or in combination of two or more simultaneously.
    (0035) However, in the present invention, a coefficient of thermal expansion of the raw materials constituting the partition walls is preferably 1.0 x 10 -6 / ° C or less at a temperature between 40 ° C and 40 ° C. 800 ° C, from the point of view of improving the impact resistance under high temperature during use at a higher temperature.
    (0036) Moreover, in the present invention, the shape of the honeycomb structural body is also not particularly limited, and may be, for example a cylinder having circular or oval end surfaces, a prism having end surfaces in the form of a polygon such as a triangle or a square, or the cylinder or prism whose sides are curved in the form of a dog's paw. In addition, the shape of the through hole is also not particularly limited and its cross section may have a polygonal shape such as a square or an octagon, a circular shape or an oval shape.
    (0037) In addition, a honeycomb filter can be produced from the honeycomb structure body of the present invention by plugging at the different end faces alternately a plurality of through holes in the openings. In this case, there is no particular limitation on the capping agent to plug the openings and this can be any capping agent usable in a conventional manner.
    (0037) A monolithic catalytic body can be produced from the honeycomb structural body of the present invention by charging the partition walls of the body with a catalyst. In the case where the honeycomb structural body is used as a support for a catalyst body, it is preferable to have a honeycomb structural body having a cell density of 0.9 to 233 cells. / cm 2 (6 to 1500 cells / in 2), and a separation wall thickness of 50 to 300 μπι. In addition, the length of the honeycomb support in its axial direction, i.e. in the direction of the flow of the exhaust gas, is usually 60 to 300 mm, preferably 100 to 250 mm. mm.
    (0037) An absorption layer can be formed on the honeycomb support. An adsorbent such as alumina having a high surface area or an adsorbent containing zeolite as the main component is usually preferably used. There is no special limitation on the zeolite and thus naturally occurring zeolite or synthetic zeolite can be used. However, it is preferable to use that having an Si / Al ratio of 40 or more, from the point of view of thermal stability, durability, and hydrophobicity. It is possible to use, for example, ZSM-5, USY, β-zeolite, silicalite, metarosilicate, or the like.
    The catalyst component (s) may be loaded directly onto the honeycomb structural body, or via the adsorption layer.
    (0038) The porous honeycomb structural body described above of the present invention may be produced by a process to be described later or by other methods.
    2. A method of manufacturing a porous honeycomb structural body (0039) In a method for making the porous honeycomb structural body of the present invention, firstly, a molded article having a Honeycomb structure is made by the use of a root ball containing a raw cordierite forming material as the main raw material and at least carbon as a pore forming agent.
    As the crude cordierite formation material used in the present invention, those obtained by mixing a silica (SiO 2) source component such as kaolin, talc, quartz, fused silica or mullite, a source component of magnesium oxygen (MgO) such as talc or magnesite, and a source component of alumina (Al2O3) such as kaolin, aluminum oxide or aluminum hydroxide so as to obtain the theoretical composition of a crystal of cordierite are generally used. However, in certain applications, those whose compositions are deliberately changed with respect to the theoretical composition, or those which contain mica, quartz, Fe 2 O 3, CaO, Na 2 O or K 2 0 as impurities may also be used. Alternatively, those having types, proportions and particle diameters of the controlled components while maintaining the theoretical composition so as to control porosity and average pore diameter of a honeycomb structural body which must be obtained can also be used.
    Illustrative examples of the carbon contained as a pore forming agent in the present invention include graphite and activated carbon. Graphite can be used as a pore forming agent which is fired at a temperature of 600 to 1200 ° C, and activated char may be used as a pore forming agent which is fired at temperatures of 400 to 1. 200 ° C. In addition, in the present invention, the carbon is incorporated in the lump in an amount of 5% or more by weight, preferably 7% or more by weight, more preferably 10% or more by weight. When the amount of carbon incorporated as a pore forming agent is below 5% by weight, it is difficult to cause the carbon to be contained in the central portion of the molded article which is to be removed by cooking at a temperature. of 1200 ° C or higher, even though a rate of increase in temperature at the time of cooking is controlled, thereby causing problems such as porosity and average pore diameter in the central part of the body of the body. Honeycomb structure can not be made wider, compared to those in the peripheral part of the honeycomb structure body. Thus, tearing due to firing shrinkage often occurs in the honeycomb structural body.
    (0042) However, when a dielectric drying is carried out in a drying step, the carbon is preferably incorporated in an amount of 25% or less by mass, more preferably 23% or less by weight, still more preferably 21% or less by mass, to prevent excessive conductivity.
    (0043) In the present invention, other materials may also be incorporated as a pore forming agent. Illustrative examples of such materials include a malleable resin, frothy resin, wheat flour, starch, phenolic resin, polymethyl methacrylate, polyethylene, and polyethylene terephthalate.
    (0044) By these, since the foamed resin such as an acrylic microcapsule is initially hollow, it is preferable in that a honeycomb structure body with high porosity can be obtained with the use a small amount of it.
    (0045) However, when a malleable resin that is removed by cooking at a lower temperature than carbon is added in a large amount, the pores are formed at a relatively low temperature as the temperature increases, and an environment in which which the easily cooked carbon is formed, so that it becomes difficult to control the rate of increase in temperature. As a result, the malleable resin is preferably incorporated in a clump in an amount of less than 5% by weight, more preferably 3% or less by weight.
    (0046) In the present invention, as necessary, other additives such as a binder and a dispersant can be incorporated into a clump.
    (0047) Illustrative examples of the binder include methyl hydroxypropyl cellulose, methyl cellulose, hydroxyethyl cellulose, methyl carboxylic cellulose, and polyvinyl alcohol. Illustrative examples of the dispersant include ethylene glycol, dextrin, fatty acid soap, and a polyhydric alcohol. These additives can be used alone or in combination of two or more in accordance with the goals.
    (0048) In the present invention, a method for preparing a clump is not particularly limited. For example, a root ball can be made by adding 5 to 40 parts by weight of the carbon-inclusive complete pore forming agent, 10 to 40 parts by weight of water and optionally 3 to 5 parts by weight of carbon. a binder and 0.5 to 2 parts by weight of a dispersant to 100 parts by weight of the raw cordierite formation material and kneading these materials together.
    (0049) In addition, as a method of manufacturing a molded article having a honeycomb structure with the use of a clod thus obtained, extrusion molding, injection molding, or plastic molding can be used. press, for example. Of these, extrusion molding is preferred because it facilitates continuous molding and can cause the cordierite crystals to orient themselves to impart low thermal expansion to the molded article.
    As a method of drying the molded article, hot air drying, microwave drying, dielectric drying, drying under reduced pressure, vacuum drying or freezing can be used, for example. Particularly, it is preferable to dry the molded article in a drying step comprising a combination of hot air drying and microwave drying or dielectric drying, since the complete molded article can be quickly and uniformly dried. .
    (0051) Next, in the present invention, the dried molded article is cooked by raising a cooking environment temperature to a rate at which the carbon in the central portion of the molded article is removed by cooking at a temperature of within a temperature ranging from 1,200 ° C (inclusive) to 1,430 ° C (not included) as the temperature of the central portion of the molded article.
    (0052) As described above, with a rate of increase in temperature at which the carbon in the central portion of the molded article is removed by cooking at a temperature below 1200 ° C, the pores of the partition walls in the central and peripheral parts in a honeycomb structural body to be obtained have the same pore diameter or the bake removal tears occur in the structural body in honeycomb, so that the honeycomb structural body that is to be obtained can not be used as a honeycomb structural body. On the other hand, with a rate of increase in temperature at which the carbon in the central portion of the molded article is not completely removed by cooking even at a temperature exceeding 1430 ° C, the cordierite constituting the partition walls are melted, thereby causing clogging or obstruction of pores or tears due to cooking shrinkage of the partition walls in the honeycomb structural body to be obtained.
    (0053) For determining the rate of temperature increase of the environment so as to bake the carbon in the central portion of the molded article at a temperature of 1,200 ° C to below 1,400 ° C as temperature of the central part of the molded article, this shall be determined by considering all factors such as carbon content, oxygen content in the cooking environment, types and contents of other training agents of pore and dimension of the molded article in an understandable manner.
    (0054) For example, when the carbon content is low, a rate of increase of the environmental temperature until the temperature of the central portion of the molded article reaches at least 1200 ° C must be fast since all the carbon is likely to be removed by cooking before the temperature of the central portion of the molded article reaches 1,200 ° C. Similarly, when the oxygen content in the cooking environment is rich, the temperature increase rate of the environment until the temperature of the central portion of the molded article reaches at least 1200 ° C must also be fast as carbon removal is accelerated.
    (0055) On the other hand, when the molded article to be fired is of a large size, the rate of increase of the temperature of the environment until the temperature of the central portion of the molded article reaches at least 1,200 ° C must be slow since a quantity of oxygen that must be delivered in the central part is low.
    (0056) On the other hand, when another pore forming agent such as a malleable resin is contained, a temperature at which the malleable resin is removed by baking is 300 to 400 ° C, which is less than the temperature at which carbon is removed by cooking. As a result, at a temperature at which the carbon starts to cook, the pores are already formed due to the firing removal of the malleable resin, and an environment in which carbon removal can be accelerated is already formed. Accordingly, when the other pore forming agent such as malleable resin or the like is contained, the higher the pore forming agent content, the faster the rate of increase of the environmental temperature will be. . Of course, a molded article can be baked by selecting an increase rate at the correct temperature within a range of 20 to 60 ° C / hr, taking into account the size of the molded article the type, quantity, or the like, of the pore forming agent.
    (0057) More specifically, for example, when a honeycomb structural body having a porosity of 57 to 61% and a dimension of φ190.5 mm x L203.2 mm at φ26β, 7 mm x L305.0 mm is manufactured by using a raw material containing 10 parts by mass of activated carbon and 2 parts by mass of malleable resin based on 100 parts by weight of the raw cordierite formation material, a molded article is preferably, baked at an environmental temperature rise rate of between 400 ° C and 1150 ° C at 30 to 35 ° C / hr (when the molded article is baked at the same rate of temperature increase ). In addition, when a honeycomb structural body having a larger dimension of φ305.0 mm × L356.0 mm is manufactured, a molded article is preferably baked at a rate of temperature rise. environment between 400 ° C and 1150 ° C from 20 to 30 ° C / hr.
    (0058) Moreover, for example, when a honeycomb structural body having a porosity of 65 to 70% and a dimension of φ144.0 mm x L152.0 mm is manufactured by the use of a raw material containing 10 parts by weight of activated charcoal and 2.2 to 2.6 parts by weight of malleable resin based on 100 parts by weight of the raw cordierite forming material, a molded article is preferably baked at a rate increasing the temperature of the environment between 400 ° C and 1150 ° C from 50 to 90 ° C / hr (when the molded article is baked at the same rate of increase in temperature). In addition, when graphite is used as a pore forming agent in place of activated carbon, the above rate of temperature increase can be applied at environmental temperatures ranging from 400 ° C to 1150 ° C. C or from 600 ° C to 1150 ° C.
    (0059) In addition, changes in porosity and average pore diameter from the outermost periphery to the central axis can be made significant near the outermost periphery by making the velocity of increase of the high environment temperature and can be made gradual from the peripheral part to the central part by making the rate of increase of temperature low.
    Examples (0060) The present invention will be further described with reference to examples. However, the present invention should not be limited by these examples in any way.
    1. Evaluation Method (0061) Honeycomb structural bodies obtained in the following Examples and Comparative Examples were evaluated in accordance with the following methods: (1) Pore Diameter (0062) As is shown in FIG. 2, a pore diameter of a partition wall portion (hereinafter referred to as a "central part") placed at a midpoint A of the central axis X or a body with a nest structure bees or at a position closest to the mid-point and a pore diameter of a partition wall (hereinafter referred to as the "peripheral portion") placed at a position B which is the outermost at From the midpoint in a direction perpendicular to the central axis were measured using a mercury injection porosimeter manufactured by Micromeritics Corporation.
    (2) Porosity (0063) A total pore volume in the central and peripheral portions of the honeycomb structural body was measured using a mercury injection porosimeter manufactured by Micromeritics Corporation, and the porosity was calculated from the total pore volume, with an absolute density of cordierite of 2.52 g / cc.
    (3) Soot Collection Pressure Loss (0064) First, against the two end surfaces of each of the honeycomb structural bodies obtained in the Examples and Comparative Examples, a ring having a diameter internal diameter of <j) 215.0 mm was pressed and, through the rings, soot generated by a soot generator was allowed to flow within a range of φ215.0 mm from the nest structure body. bee to collect 33 g of soot. Then air at 6.2 Nm3 / min was allowed to flow with the soot collected on the honeycomb structure body and a pressure difference between the two sides of the nest structure body. bee was measured to evaluate a loss of pressure of the honeycomb structural body having the soot collected thereon.
    (4) Isostatic Resistance (0065) Firstly, both sides of the honeycomb structural body were covered with a metal plate having the same diameter as that of the honeycomb structural body, the metal plates were attached with a rubber hose having the same diameter as that of the honeycomb structural body, and a rubber bollard was applied to and around the rubber hoses to seal the structural body honeycomb against the entrance of the water. Then, the sealed honeycomb structural body was immersed in water, a water pressure was raised until the honeycomb structural body was broken and a resistance Isostatic (MPa) was evaluated on the basis of the water pressure at which the honeycomb structural body was broken.
    (5) Determination method for the pressure loss rise ratio (0065) Each of the catalyst bodies prepared by charging the respective honeycomb structural bodies obtained in Example 9 and in the Comparative Example 11 with a catalyst was placed in a metal cabinet, respectively. Then, hot air having a temperature of 400 ° C was allowed to flow into each of the boxed catalyst bodies at a flow rate of 13 m 3 / min. The pressure difference between the inlet port portion and the outlet port portion was measured to obtain the pressure loss A1. The same procedure was repeated using respective honeycomb structural bodies. in a case in which no catalyst has been charged to obtain the pressure loss A2. The ratio of elevation of the pressure loss is obtained from the following equation:
    Ratio of elevation of pressure loss = (A1-A2) / A2 x100.
    (6) Exhaust gas cleaning efficiency test (0065) Each of the catalyst bodies prepared as a sample for the determination of the pressure loss was also used for the determination of the purification efficiency. . The efficiency of the exhaust gas purification was evaluated using a 5 liter diesel engine. The exhaust gases from the engine were conducted into each of the catalyst bodies. The HC concentration in the exhaust gas at the inlet of the catalyst body, B1 and the HC concentration in the exhaust gas at its outlet port, B2 were determined. The efficiency of the treatment was calculated from the following equation:
    Effectiveness of purification = (B1-B2) / B1x100.
    2. Examples, comparative examples, and their evaluations.
    (0066) As shown in line 1 of the
    Table 1, 39.8% by weight of talc (average particle diameter: 21 μm), 18.5% by weight of kaolin (average particle diameter: 11 μm), 14.0% by weight of alumina (diameter of average particle size: 7 gm), 15.2% by weight of aluminum hydroxide (average particle diameter: 2 gm) and 12.5% by weight of silica (average particle diameter: 25 gm), were mixed together to make a raw cordierite formation material.
    (0067) Then, based on 100 parts by weight of the cordierite-forming raw material, 10.0 parts by weight of carbon (graphite) (average particle diameter: 53 gm), 2.0 parts by weight of a malleable resin (average particle diameter: 50 gm), 4 parts by weight of a binder, 0.5 parts by weight of a surfactant and 31 parts by weight of water were loaded into a kneader and then kneaded for 60 minutes to obtain a corroi.
    (0068) Next, the resulting clod was loaded into a vacuum mill and kneaded to make a cylindrical clump, and the clod was then loaded into an extruder to be molded into a honeycomb shape. Then, after being subjected to dielectric drying, the molded article was completely dried by hot air drying and its two end faces were cut to a given size.
    (0069) Then, the openings of the passage holes of the dried honeycomb article were plugged at an alternately different position at the two end faces for the use of a suspension made of a raw material of cordierite formation of the same composition.
    (0070) Finally, the article was fired at a temperature of 600 to 1150 ° C within an oxygen concentration of 10 to 15% by volume in accordance with a temperature program shown in line 1 in of Table 2 to obtain a honeycomb structure body (honeycomb filter) having a dimension of φ229.0 mm × L305.0 mm, a separation wall thickness of 300 μm and 46, 5 x 10 -2 / mm 2 (300 cells / in 2).
    (Example 2) (0071) A honeycomb structural body (honeycomb filter) was obtained in the same manner as in Example 1 except that a molded article was baked in accordance with a temperature program shown in row 2 of Table 2.
    (Example 3) (0072) A honeycomb structural body (honeycomb filter) was obtained in the same manner as in Example 1 except that a molded article was baked in accordance with a temperature program shown in row 3 of Table 2.
    (Comparative Example 2) (0073) A honeycomb structural body (honeycomb filter) was obtained in the same manner as in Example 1 except that, as shown in line 2 of the Table 1, silica with an average particle diameter of 35 μm was used and based on 100 parts by weight of the raw cordierite formation material, 20.0 parts by weight of carbon (graphite), 1.5 parts of malleable resin mass, 4 parts by weight of binder, 0.5 part by weight of surfactant and 34 parts by weight of water were loaded into a kneader and then kneaded for 60 minutes to obtain a clump.
    (Example 3) (0074) A honeycomb structural body (honeycomb filter) was obtained in the same manner as in Example 1 except as shown in line 2 of Table 1, silica with an average particle diameter of 35 μm was used and based on 100 parts by weight of the cordierite formation raw material, 20.0 parts by weight of carbon (graphite), 1.5 parts by mass of malleable resin 4 parts by weight of binder, 0.5 parts by weight of surfactant and 34 parts by weight of water were loaded into a kneader and kneaded for 60 minutes to obtain a clump and a molded article was cooked in accordance with a temperature program shown in row 2 of Table 2.
    (Comparative Example 3) (0075) A honeycomb structural body (honeycomb filter) was obtained in the same manner as in Example 1 except that, as shown in line 2 of Table 1 silica having an average particle diameter of 35 μm was used and based on 100 parts by weight of the cordierite formation raw material, 20.0 parts by weight of carbon (graphite), 1.5 parts by weight of malleable resin, 4 parts by weight of binder, 0.5 parts by weight of surfactant and 34 parts by weight of water were loaded into a kneader and kneaded for 60 minutes to obtain a root ball, and the article molded was cooked in accordance with a temperature schedule shown in line 3 of Table 2.
    (Example 4) (0076) A honeycomb structural body (honeycomb filter) was obtained in the same manner as in Example 1 except that, as shown in line 3 of Table 1, silica with an average particle diameter of 35 μm was used and based on 100 parts by weight of the cordierite formation raw material, 5.0 parts by weight of carbon (graphite), 3.0 parts by weight of malleable resin, 4 parts by weight of binder, 0.5 parts by weight of surfactant and 30 parts by weight of water were loaded into a kneader and kneaded for 60 minutes to obtain a corroi, and a molded article was baked in accordance with a temperature schedule shown at line 4 of Table 2.
    (Comparative Example 4) (0077) A honeycomb structural body (honeycomb filter) was obtained in the same manner as in Example 1 except that, as shown in line 3 of Table 1 silica having a mean particle diameter of 35 μm was used and based on 100 parts by weight of the cordierite formation raw material, 5.0 parts by weight of carbon (graphite), 3.0 parts by weight of malleable resin, 4 parts by weight of binder, 0.5 parts by weight of surfactant and 30 parts by weight of water were loaded into a kneader and kneaded for 60 minutes to obtain a clod and a molded article. was cooked in accordance with a temperature schedule shown in row 3 of Table 2.
    (Comparative Example 5) (0078) A honeycomb structural body (honeycomb filter) was obtained in the same manner as in Example 1 except as shown in line 3 of Table 1, silica with an average particle diameter of 35 μm was used and based on 100 parts by weight of the cordierite formation raw material, 5.0 parts by weight of carbon (graphite), 3.0 parts by weight of resin malleable, 4 parts by weight of binder, 0.5 parts by weight of surfactant and 30 parts by weight of water were loaded into a kneader and kneaded for 60 minutes to obtain a clod and a molded article was baked in accordance with a temperature schedule shown in line 1 of Table 2.
    37
    Table 1
    Preparation Composition
    Note: Numbers in parentheses mean average particle diameters (pm) 38 Table 2 Cooking Conditions
    (Evaluation Results) (0079) As for the efficiency of soot collection, although not specifically represented in Table 3, a 95-98% soot collector yield that was satisfactory from the point of view practice has been achieved in the examples and in the comparative examples.
    (1) Examples 1 and 2 and Comparative Example 1 (0080) These examples and the comparative example are the same in that the honeycomb molded article was manufactured by the use of a root ball containing 10, 0 parts by weight of carbon (graphite) and 2.0 parts by weight of malleable resin based on 100 parts by weight of the cordierite raw material and different in that the molded articles were baked in accordance with the programs temperature values shown in rows 1 to 3 of Table 2, respectively.
    (0081) As shown in Table 3, in Example 1 wherein the molded article was fired at an environmental temperature increase rate of 35 ° C / hr between 600 ° C and 1150 ° C C and Example 2 in which the molded article was fired at an environmental temperature increase rate of 20 ° C / hr between 600 ° C and 1150 ° C, the carbon (graphite) was completely removed by firing at temperatures ranging from 1,200 ° C to a temperature below 1,430 ° C, i.e. at 1,290 ° C (temperature of a central portion of the molded article) in Example 1 and at 1220 ° C (temperature of a central portion of the molded article) in Example 2, and the honeycomb structural bodies can be obtained without baking crack. In addition, in all of the obtained honeycomb structural bodies, a pore diameter and a porosity of a central portion were greater than those of a peripheral portion of at least 2 μm and at least 2%, respectively. Therefore, despite significant isostatic resistances of not less than 2.9 MPa, the soot collection pressure losses were as low as 5.9 kpa or lower. More particularly, in Example 1 in which the rate of increase of the environmental temperature between 600 ° C and 1150 ° C was rapid, a pore diameter and the porosity of a central portion were greater than those of a peripheral portion of 5 pm and 5%, respectively, and a loss of soot collection pressure was particularly low of a value of 5.2 kpa.
    (0082) Moreover, in Comparative Example 1 in which the molded article was cooked under commonly used cooking conditions, namely that the article was cooked at a rate of temperature increase of the environment of 20 ° C / hr between 600 ° C and 900 ° C and 10 ° C / hr between 900 ° C and 1000 ° C and then maintained at 1200 ° C for 10 hours, the carbon in the central part of the The molded article was removed by firing at 1160 ° C (temperature of the central portion of the molded article), and baking cracks were observed in the resultant honeycomb structural body. Thus, the obtained honeycomb structural body is not practical for use as a honeycomb filter.
    (0083) In addition, with regard to the honeycomb structural body obtained in Example 1, a pore diameter and a porosity of the partition wall placed at each 28.6 mm from the midpoint A (center) ) of the central axis in a direction perpendicular to the central axis were measured as shown in FIG. 5. It follows that porosity and pore diameter have been found to change continuously from the peripheral portion to the central portion and that pore diameter porosity change values between the peripheral portion and the separation which form a cell placed 1/3 from the outermost periphery, the length between the outermost periphery and the central axis corresponded to 71% and 69% of the total values of the changes, respectively, as shown in Figs. 6 and 7.
    (2) Example 3 and Comparative Examples 2 and 3 (0084) This example and the comparative examples are the same in that the honeycomb structural body (honeycomb filter) was manufactured by use of a clump containing 20.0 parts by mass of carbon and 1.5 parts by mass of malleable resin based on 100 parts by weight of cordierite raw material (in which the carbon is not easily removed by cooking until the temperature of the root ball reaches a higher temperature than the temperature range of the above Example 1) and different in that the molded articles have been cooked in accordance with the temperature programs shown in lines 1 to 3 in Table 2, respectively.
    (0085) As shown in Table 3, in Example 3 wherein the molded article was fired at an environmental temperature increase rate of 20 ° C / hr between 600 ° C and 1150 ° C, the carbon in the central portion of the molded article was removed by firing at temperatures ranging from 1,200 ° C to a lower value of 1,430 ° C, i.e. at 1350 ° C ( temperature of the central portion of the molded article), and the honeycomb structural body can be obtained without baking crack. In addition, the differences in diameter and porosity between the central portion and the peripheral portion of the obtained honeycomb structure body were very large, such as 7 μm and 6%, respectively. As a result, despite a significant isostatic resistance of 2.9 MPa, a soot collection pressure loss was very low at a value of 5.0 kPa.
    (0086) Furthermore, in Comparative Example 2 in which the molded article was fired at an environmental temperature increase rate of 35 ° C / hr between 600 ° C and 1150 ° C, the carbon in a central portion of the molded article was removed by firing at a temperature of not less than 1430 ° C, namely 1445 ° C (temperature of the central portion of the molded article) which was the melting point of the cordierite and the honeycomb structural body obtained with cooking crack portions due to the melting of a partition wall were not practically usable as a structural body. Honeycomb. In addition, in Comparative Example 3 wherein the molded article was baked under generally conventionally used baking conditions, ie, the article was baked at a rate of temperature rise of the environment at 20 ° C / hr between 600 ° C and 900 ° C and 10 ° C / hr between 900 ° C and 1000 ° C and then held at 1000 ° C for 10 hours, the carbon in a central portion of the The molded article was removed by baking at 1135 ° C (temperature of the central portion of the molded article), and a baking crack was observed in the obtained honeycomb structural body.
    (3) Example 4 and Comparative Examples 4 and 5 (0087) This example and the comparative examples are the same in that the honeycomb structural body (honeycomb filter) was manufactured by the use of a clump containing 5.0 parts by mass of carbon and 3.0 parts by weight of malleable resin based on 100 parts by weight of raw cordierite formation material (wherein the carbon is easily removed by cooking at a temperature less than the temperature range of Example 1 above) and different in that the molded articles were fired in accordance with temperature programs shown in lines 1, 3 and 4 of Table 2, respectively.
    (0088) As shown in Table 3, in Example 4 wherein the molded article was fired at an environmental temperature increase rate of 60 ° C / hr between 600 ° C and 1150 ° C. ° C, the carbon in the central portion of the molded article was removed by firing at temperatures ranging from 1,200 ° C to a lower temperature of 1,430 ° C, ie, at 1,285 ° C (temperature of the central part of the molded article), and the honeycomb structural body can be obtained without a baking crack. In addition, the differences in pore diameter and porosity between the central portion and the peripheral portion of the resulting honeycomb structure body were very large, such as 3 μιη and 3%, respectively. Consequently, although a substantial isostatic resistance of 2.8 MPa, which is practically satisfactory from the point of view of practice, has been obtained, a soot collection pressure loss has been very low by a value of 5, 2 kpa.
    (0089) Furthermore, in Comparative Example 4 in which the molded article was baked under generally conventionally used baking conditions, ie, the article was baked at a rate of temperature increase of the environment of 20 ° C / hr between 600 ° C and 900 ° C, and 10 ° C / hr between 900 ° C and 1000 ° C and then maintained at 1000 ° C for 10 hours, carbon in part of the molded article was removed by firing before the temperature of the molded article reached a temperature range in which the firing shrinkage was significant, namely, at 950 ° C (temperature of the central portion of the molded article). In addition, although no cooking cracks were observed in the obtained honeycomb structural body, there was no difference in pore diameter and porosity between the peripheral portion and the central portion. honeycomb structural body. Thus, although an isostatic resistance of 2.8 MPa which was similar to that of Example 3 was obtained, a soot collection pressure loss was 5.9 kPa, which was greater than in the Example 3. In addition, in Comparative Example 5 wherein the molded article was fired at an environmental increase rate of 35 ° C / hr between 600 ° C and 1150 ° C, the carbon in a central portion of the molded article was removed by baking at 1150 ° C (temperature of the central portion of the molded article), and baking cracks were observed in the honeycomb structural body got.
    (Examples 5 to 7 and Comparative Examples 6 and 7) (0090) Honeycomb structural bodies (honeycomb filter) were produced in the same manner as in Example 1, except that the articles molded honeycomb moldings having dimensions of φ143.8 mm x L152.4 mm (φ5.66 inches x L6.0 inches), φ190.5 mm x L203.2 mm (φ7.5 inches x L8.0 inch), φ228, β mm x L203.2 mm (φ9.0 inches x L8.0 inches), φ266.7 mm x L304.8 mm (φ10.5 inches x L12.0 inches) and φ304, 8 mm x L355, 6 mm (φ12.0 inches x L14.0 inches) were manufactured and that these items were fired in accordance with a temperature schedule shown in line 5 of Table 4.
    (Evaluation Results) (0091) As shown in FIG. 3, in Comparative Example 6 wherein the molded article having a dimension of φ143.8 mm x L152.4 mm (φ5.66 inches x L6.0 inches) was baked, a peak indicating that the carbon in the The central portion of the molded article was removed by firing at 1080 ° C (temperature of the central portion of the molded article) at which the firing shrinkage temperature was significant. Furthermore, in Comparative Example 7 in which the molded article having a dimension of φ304.8 mm x L355.6 mm (φ12.0 inches x L14.0 inches) was baked, a peak indicating that the carbon in a central portion of the molded article was removed by firing at about 1310 ° C (temperature of the central portion of the molded article) was recognized.
    (0092) In contrast, in Examples 5 to 7 in which the molded articles having dimensions of φ190.5mm x L203.2mm (φ7.5 inches x L8.0 inches), φ228.6mm x L203 , 2mm (φ9.0 inches x L8.0 inches) and φ2ββ, 7mm x L304.8mm (φΐ0.5 inches x L12.0 inches), were fired, with peaks indicating that carbon in the central parts of molded articles were removed by firing at temperatures ranging from 1,200 ° C to a temperature below 1,430 ° C, ie at 1,220 ° C, 1,250 ° C and 1,290 ° C (temperatures of the parts molded articles) respectively, have been recognized.
    (Example 8 and Comparative Examples 8 to 10) (0093) Honeycomb structural bodies (honeycomb filter) were produced in the same manner as in Example 1 except that molded articles honeycomb which have been fired having dimensions of φ143.8 mm x L152.4 mm (φ5.66 inches x L6.0 inches), φ190.5 mm x L203.2 mm (φ7.5 inches x L8, 0 inches), φ228.6 mm x L203.2 mm (φ9.0 inches x L8.0 inches) and φ266, 7 mm x L304.8 mm (φ10.5 inches x L12.0 inches) were manufactured and in that these molded articles have been fired in accordance with a temperature schedule shown in line 6 of Table 4.
    (Evaluation Results) (0094) As shown in FIG. 4, in Comparative Examples 9 and 10 in which the molded articles having dimensions of φ190.5 mm × L203.2 mm (φ7.5 inches x L8.0 inches) and 228.6 mm × L203.2 mm (( φ9.0 inches x L8.0 inches) were cooked, respectively, peaks indicating that the carbon in the central parts of the molded articles were removed by firing at 1 130 ° C and 1 190 ° C (temperature of the central parts of molded articles) to which a significant shrinkage was found, and in Comparative Example 8 in which the molded article having a dimension of φ143.8 mm x L152.4 mm (φ5.66 inches x L6 0 inches) was cooked, a peak indicating that the carbon in a central portion of the molded article was removed by firing at 990 ° C (temperature of the central portion of the molded article) was recognized.
    (0095) Δ the opposite, in Example 8 in which the molded article having a dimension of φ266.7 mm × L304.8 mm (φΐ0.5 inches x L12.0 inches) was baked, a peak indicating that the carbon in a central portion of the molded article was removed by firing at temperatures ranging from 1200 ° C to a temperature below 1430 ° C, i.e. the central part of the molded article), has been recognized.
    (Example 9) (0093) Honeycomb structure bodies (catalyst support) having the dimension of φ229.0 mm × L152.0 mm, the thickness of the partition walls of 300 μm and the cell density 300 cells / in 2 were manufactured in the same manner as in Example 1 except that no plugging of the end-face openings was made. Each of these honeycomb structural bodies thus prepared was charged to 500 g of a high surface area alumina mixture and Pt containing an oxidation catalyst to obtain a catalyst body, respectively. The pore diameter in the peripheral portion and the diameter in the central portion of the resulting catalyst body were 14 μm and 19 μm, respectively. The porosity in the peripheral portion and that in the central portion of the catalyst body obtained were 54% and 59%, respectively.
    (Comparative Example 11) (0093) Honeycomb structure bodies (catalyst support) having the dimension of φ229.0 mm × L152.0 mm, the thickness of the partition walls of 300 μm and the density of 300 cell / inch2 cell were manufactured in the same manner as in Comparative Example 4 except that no plugging of the end face openings was made. Each of the honeycomb structural bodies thus prepared was charged to 500 g of a mixture of alumina having a high specific surface area and Pt containing an oxidation catalyst to obtain a catalyst body, respectively. The pore diameter in the peripheral portion and the diameter in the central portion of the resulting catalyst body were 15 μm and 15 μm, respectively. The porosity in the peripheral portion and in the central portion of the catalyst body obtained were 55% and 55%, respectively.
    Note: * 1 represents data after catalyst loading.
    (Evaluation Results) (0081) As shown in Table 5, in the case where the body of the catalyst prepared by charging a honeycomb structural body in accordance with Example 9 with a catalyst, the isostatic resistance of the catalyst body was as large as 5.8 MPa due to obtaining a higher porosity and increasing the amount of charged catalyst obtained since obtaining a larger body diameter since the Honeycomb structural body had a pore diameter and a porosity of a central portion larger than those of a peripheral portion of 4 μm and 4%, respectively, compared to those in the peripheral portion. As a result, despite significant soot collection pressure losses, these were as low as 5.9 kpa or smaller. In addition, the rate of increase in pressure loss was as low as 5% and the exhaust purification efficiency was as high as 70%. On the other hand, in the case of the preferred catalyst body by charging a honeycomb structural body having a pore diameter and a porosity in the central portion equal to those in the peripheral portion in accordance with Comparative Example 11 with a catalyst, the isostatic resistance of the catalyst body was 5.5 MPa, which was much lower than that of the honeycomb structural body in accordance with Example 9. In addition, the rate of increase of the pressure loss was 11%, and the exhaust purification efficiency was 58%, both being lower than in Example 9.
    (0096) As described above, in accordance with the present invention, a porous honeycomb structural body capable of satisfying pressure loss and isostatic resistance which are mutually contradictory properties simultaneously and suitable for particular use. in a filter for collecting and removing particulates in the exhaust gas, or a support for the scrubbing catalysts for decomposing and suppressing NOx and HC in the exhaust gases as well as processes for making the porous structure body Honeycomb can be offered.
    权利要求:
    Claims (11)
    [1]
    A porous honeycomb structural body having separating walls which contain cordierite as the main crystalline phase and have a porosity of 40 to 75% and an average pore diameter of 10 to 50 μιη, wherein the porosity and the average pore diameter in a central portion of the honeycomb structural body is larger than that in a peripheral portion of the honeycomb structural body.
    [2]
    The honeycomb structural body according to claim 1, wherein the porosity in the central portion of the honeycomb structural body is greater than that in the peripheral portion of the honeycomb structural body. by at least 2%, and the average pore diameter in the central part of the honeycomb structural body is larger than that in the peripheral part of the honeycomb structural body by at least 2 μm .
    [3]
    The honeycomb structural body according to claim 1 or 2, wherein the porosity in the central portion of the honeycomb structural body is greater than that in the peripheral portion of the honeycomb structural body. bee of at least 3%.
    [4]
    A honeycomb structural body according to any one of claims 1 to 3, wherein the average pore diameter in the central portion of the honeycomb structural body is larger than that in the peripheral portion. honeycomb structural body of at least 3 μm.
    [5]
    A method for using the honeycomb structural body according to any one of claims 1 to 4 as a filter for filtering deleterious materials or as a support for charging an exhaust gas cleaning catalyst.
    [6]
    A process for producing a porous honeycomb structural body which comprises the steps of: preparing a molded article having a honeycomb structure by using a root containing a raw material forming cordierite as the main raw material and carbon in an amount of at least 5 parts by mass based on 100 parts by weight of the raw cordierite forming material, drying and then baking the molded article in which, on during baking of the molded article, a temperature of the environment is increased at a rate at which carbon in a central portion of the molded article is removed by baking at temperatures of the central portion of the molded article which range from 1,200 ° C to below 1,430 ° C.
    [7]
    The method of claim 6, wherein the temperature of the environment is increased at a rate of 20 to 60 ° C / hr within a temperature range of 400 to 1150 ° C.
    [8]
    The process of claim 6 or 7, wherein the temperature of the environment is maintained within a temperature range of 1150 to 1200 ° C for at least 5 hours.
    [9]
    The method of any one of claims 6 to 8, wherein a carbon-containing clump in an amount of 25 parts or less by weight based on 100 parts by weight of the raw cordierite formation material is used.
    [10]
    The process according to any of claims 6 to 9, wherein an environment in which the molded article is fired comprises an environmental temperature of 400 to 1150 ° C and an oxygen concentration of 7 to 17%. in volume.
    [11]
    The method of any one of claims 6 to 10, wherein a lumen containing a malleable resin in an amount of less than 5 parts by weight based on 100 parts by weight of raw cordierite formation material is used.
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    同族专利:
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    US20030143370A1|2003-07-31|
    CN1434001A|2003-08-06|
    DE10301959A1|2003-08-07|
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    法律状态:
    2010-07-31| RE| Patent lapsed|Effective date: 20100131 |
    优先权:
    申请号 | 申请日 | 专利标题
    JP2002012113|2002-01-21|
    JP2002012113|2002-01-21|
    JP2002352600A|JP2003277162A|2002-01-21|2002-12-04|Porous honeycomb structural body, application thereof and manufacturing method therefor|
    JP2002352600|2002-12-04|
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