JP2009515808A - System for extruding porous carriers - Google Patents

Abstract

An extrudable mixture is provided for producing a highly porous support using an extrusion process. More particularly, the present invention can be mixed with masses that form highly porous carriers when extruded and cured, such as organic, inorganic, glass, ceramic or metal fibers. Depending on the particular mixture, the present invention allows carrier porosity from about 60% to about 90%, and also allows processing advantages at other porosity. The extrudable mixture can use a wide variety of fibers and additives and can be adapted to a wide variety of operating environments and applications. Depending on the support requirements, fibers exhibiting an aspect ratio greater than 1 are selected and mixed with a binder, pore-forming component, extrusion aid, and fluid to form a homogeneous, extrudable mass. The homogeneous mass is extruded onto a green carrier. Many volatile materials are preferentially removed from the green carrier, which causes the fibers to interconnect and contact. As the curing process continues, a fiber-to-fiber bond is formed, resulting in a structure having a substantially open pore network. The resulting porous support is useful in many applications, for example as a support for filter media or catalyst hosts, or as a catalytic converter.

Description

  This application was filed on Nov. 16, 2005, and in US Provisional Application No. 60 / 737,237 entitled “System for Extruding Porous Carriers”; Dec. 30, 2005 And filed on Dec. 30, 2005, in US patent application Ser. No. 11 / 323,430 entitled “Extrudable Mixtures to Form Porous Blocks” Filed in US patent application Ser. No. 11 / 322,777 entitled “Extruding the Carrier”; and filed Dec. 30, 2005 and entitled “Extruded Porous Carrier and Product Using It”. US patent application Ser. No. 11 / 323,429, which is hereby incorporated by reference in its entirety.

  The present invention generally relates to an extrusion process for extruding a porous support, and in one particular means, an extrusion process for extruding a porous ceramic support. Many processes require a rigid carrier to facilitate and support various processes. For example, carriers are used in filtration applications to filter particulates, separate various substances, or remove bacteria or pathogens from the air.

  These carriers can be constructed to operate in the air, vent gases or liquids, and can be manufactured to withstand substantial environmental or chemical stresses. In another example, catalyst material is deposited on a support to promote chemical reactions. For example, the noble metal can be deposited on a suitable support, which can then serve to catalyze the conversion of hazardous exhaust gases to less harmful gases. In particular, these rigid carriers exhibiting high porosity work more effectively.

  Porosity is generally defined as the property of a solid material that defines the percentage of the total volume of that material that is occupied in an open space. For example, a carrier exhibiting 50% porosity exhibits half the volume of the carrier occupied by the open space. In this respect, a carrier exhibiting a high porosity has a lower mass per volume than a carrier exhibiting a low porosity. Certain applications benefit from low mass carriers. For example, the support is used to support the catalytic process, and when the catalytic process operates at an elevated temperature, the support that exhibits a low calorie heats more quickly to its operating temperature. In this respect, the time during which the catalyst is heated to the operating temperature, ie the turn-off time, is reduced by using a larger support that is more porous and thermally lower.

  Permeability is also an important feature for supports, particularly filtration and catalyst supports. Permeability is related to porosity in that permeability is a measure of how easily a fluid such as a liquid or gas can flow through a carrier. Most applications benefit from a highly permeable carrier. For example, an internal combustion engine works more effectively when an aftertreatment filter provides a low back pressure to the engine. Low back pressure is created by using a higher permeable carrier. Since permeability is more difficult to measure than porosity, porosity is often used as an alternative guide to carrier permeability. However, if the pores are generally empty and not interconnected, the support can be very porous, but this is not a particularly rigorous feature since it is still limited in permeability. . For example, styrofoam beverage cups are formed from a very porous foam material, but are not permeable to liquid flow. Therefore, the pore structure of the carrier should also be examined when considering the importance of porosity and permeability. In the example of a styrofoam cup, the styrofoam material has a closed pore network. This means that the foam contains many unconnected and / or closed end pores.

  In this regard, there are many voids and open spaces in the foam, but the pores are not connected, so no fluid or gas can flow from one side of the foam to the other. As many channels (channels) begin to connect with each other, the fluid path then begins to form from one to the other. In such a case, the material appears to have more open pore networks. The more connecting channels formed in the material, the higher the permeability for the material. If each pore is connected to at least one other path and the total pores allow the flow of fluid to pass through the full thickness of the wall formed from the material, the carrier is completely open pores Defined as having a network. It is important to note the difference between cells and pores. The cells are referred to as paths that penetrate the honeycomb carrier (generally parallel to each other, but not necessarily). Often, a honeycomb carrier is true under the circumstances of how many cells per square inch the carrier has. For example, a carrier having 200 cells per square inch has 200 paths along the major axis of the carrier. On the other hand, the pores correspond to gaps inside the material itself, such as in the material that builds the walls separating two parallel paths or cells. Completely or almost open pore network carriers are not known in the filtration or catalyst industry. Instead, even the most porous available extrusion supports are a hybrid of open and closed porosity.

  Therefore, it is highly desirable for many applications that the support be formed with an internal porosity structure that allows for high porosity and also high permeability. In addition, the carrier should have a structure that is sufficiently rigid to support the structural and environmental requirements for a particular application. For example, a filter media or catalytic converter that is intended to be in intimate contact with an internal combustion engine must be able to withstand possible environmental shocks, thermal requirements and manufacturing and service stresses. Ultimately, the carrier needs to be produced at a sufficiently low cost to accommodate a wide range of applications. For example, filter carriers must be affordable and available in developed as well as developing countries to affect the level of pollution worldwide from automobiles. Thus, the overall cost structure for the filter media and catalytic converter carrier is a substantial consideration in the carrier design and selection process.

  Extrusion has proven to be an effective and cost effective method for producing rigid carriers of constant cross section. More specifically, the extrusion of ceramic powder material is the most widely used method for producing filter media and catalyst supports for internal combustion engines. Over the years, the method of extruding powdered ceramics has evolved to be able to extrude carriers that exhibit a porosity approaching 60%. These extruded porous carriers exhibit excellent strength characteristics, can be manufactured flexibly, can be expanded, maintain high quality standards, and are very cost effective. However, extrusion of powder ceramic material achieves a certain upper limit porosity, and further increases in porosity are likely to produce unacceptably low strength. For example, if the porosity is increased beyond 60%, the extruded ceramic powder support has not proven to be strong enough to operate in the harsh environment of diesel particulate filters. In another limitation of the known extrusion process, it has been desired to increase the surface area in the support that addresses more thorough catalytic conversion. In order to increase the surface area, the extruded ceramic powder support attempted to increase the cell density, but the increase in cell density resulted in unacceptable back pressure to the engine. Thus, the extruded ceramic powder support does not exhibit sufficient strength at very high porosity, and further creates an unacceptable back pressure when the surface area needs to be increased. Thus, the extrusion of ceramic powder appears to have reached its specific availability limit.

  In an effort to obtain a high porosity, filter media suppliers have attempted to move to pleated ceramic paper. Using such pleated ceramic paper, a porosity of about 80% is possible which exhibits a very low back pressure. With such low back pressure, these filter media have been used in applications such as excavation where extremely low back pressure is required.

  However, the use of pleated ceramic paper filter media has been sporadic and has not been widely adopted. For example, pleated ceramic paper has not been used effectively in harsh environments. Producing pleated ceramic paper requires the use of a papermaking process that creates a relatively weak ceramic paper structure and does not appear to be cost effective compared to extruded filter media. Furthermore, the formation of pleated ceramic paper allows little flexibility in cell shape and density. For example, it is difficult to create a paper fluted filter medium with a large inlet path and a small outlet path, which may be desirable in certain filtration applications. Therefore, the use of pleated ceramic paper did not satisfy the requirements for high porosity filter media and catalyst supports.

  Another example of an effort to increase porosity and avoid the disadvantages of pleated paper is to carefully process the mass to form a mass with a ceramic precursor and grow single crystal whiskers in a porous pattern Some have built a carrier by doing so. However, growing these crystals in situ requires careful and precise control of the curing process, making the process difficult to measure, relatively expensive, and prone to defects. Furthermore, this difficult method only gives an additional percentage to the porosity. Ultimately, the process only grows mullite-type crystal whiskers, which limits the availability of the support. For example, mullite is known to exhibit a large coefficient of thermal expansion, which makes crystalline mullite whiskers undesirable in many applications that require a wide operating temperature range and a sensitive temperature transition.

  Thus, the industry requires a rigid carrier that exhibits high porosity and associated high permeability. Preferably, the support is formed as a highly desirable open cell network, is cost effective to manufacture, and can be manufactured with flexible physical, chemical, and reactive properties.

  Briefly, the present invention provides an extrudable mixture for producing a highly porous support using an extrusion process. More particularly, the present invention can be mixed with masses that form highly porous carriers when extruded and cured, such as organic, inorganic, glass, ceramic or metal fibers. Depending on the particular mixture, the present invention allows carrier porosity from about 60% to about 90%, and also allows processing advantages at other porosity. The extrudable mixture can use a wide variety of fibers and additives and can be adapted to a wide variety of operating environments and applications. Depending on the support requirements, fibers exhibiting an aspect ratio greater than 1 are selected and mixed with a binder, pore-forming component, extrusion aid, and fluid to form a homogeneous, extrudable mass. The homogeneous mass is extruded into a green carrier to preferentially remove many volatile materials from the green carrier, which interconnects and contacts the fibers. As the curing process continues, a fiber-to-fiber bond is formed, resulting in a structure having a substantially open pore network. The resulting porous support is useful in many applications, for example as a support for filter media or catalyst hosts, or as a catalytic converter.

  In a more specific example, more typically, ceramic fibers that are in the range of about 3 to about 500 but exhibit an aspect ratio distribution between about 3 and about 1000 are selected. Aspect ratio is the ratio of fiber length divided by fiber diameter. The ceramic fibers are mixed in a homogeneous mass with binder, pore forming component, and fluid. A shear mixing process is used to distribute the fibers evenly and evenly throughout the mass. The ceramic material can be from about 8% to about 40% by weight of the mass and it yields a support that exhibits a porosity between about 92% and about 60%. A homogeneous mass is extruded into a green carrier. The binder material is removed from the green carrier, which can overlap and contact the fibers. Continuing the curing process forms a fiber-to-fiber bond, resulting in a rigid open cell network. As used in this description, “curing” is defined as including two important process steps. 1) binder removal, and 2) bond formation. The binder removal process removes water, removes most additives, and allows fiber-to-fiber contact. The resulting porous support is useful in many applications, for example as a support for filter media or catalytic converters.

  In another specific example, a porous support can be produced without the use of pore-forming components. In this case, the ceramic material can be from about 40% to about 60% or more by mass of the mass and it yields a support that exhibits a porosity between about 60% and about 40%. Since no pore forming component is used, the extrusion process is simplified and more cost effective. Furthermore, the resulting structure is a highly desirable and substantially open pore network.

  Advantageously, the disclosed fiber extrusion system produces a carrier that exhibits high porosity and has an open pore network that allows the associated high permeability, as well as sufficient strength depending on the needs of the application. . The fiber extrusion system also produces a carrier that is sufficiently cost effective to allow widespread use of the resulting filter media and catalytic converter. Extrusion systems can be easily extended to mass production and address flexible chemistry and structure to support multiple applications. The present invention makes pioneering use of fiber materials in extrudable mixtures. This fibrous extrudable mixture allows for the extrusion of supports exhibiting very high porosity in an expandable production and in a cost-effective manner. By allowing the fibers to be used in repeatable and robust extrusion processes, the present invention enables mass production of versatile filter media and catalyst supports throughout the world.

  These and other features of the present invention will become apparent from an interpretation of the following description and may be appreciated by means of its combination and combinations particularly pointed out in the appended claims.

  A detailed description of embodiments of the present invention is provided herein. However, it should be construed that the present invention can be exemplified in various forms. Accordingly, the specific details disclosed herein are not to be construed as limitations, but rather teach one of ordinary skill in the art how to use the invention in any detailed system, structure, or means. It should be interpreted as a representative basis.

  With reference now to FIG. 1, a system for extruding a porous support is illustrated. In general, the system 10 uses an extrusion process that extrudes a green carrier that can eventually be cured into a highly porous carrier product. The system 10 advantageously produces a carrier that exhibits a high porosity, has a network of substantially open pores that allows the associated high permeability, and has sufficient strength depending on the application needs. The system 10 also produces a carrier that is sufficiently cost effective to allow widespread use of the resulting filter media and catalytic converter. System 10 is easily scalable to mass production and addresses flexible chemistry and construction that supports numerous applications.

  System 10 allows for a very flexible extrusion process and is therefore adaptable to a wide range of specific applications. When using the system 10, the carrier designer first establishes requirements for the carrier. These requirements can include, for example, size, fluid permeability, desired porosity, pore size, mechanical strength and impact properties, thermal stability, and chemical reaction limits. With these and other requirements, the designer selects the material to use in forming the extrudable mixture. Importantly, the system 10 allows the use of fibers 12 in forming the extruded carrier. These fibers include, for example, ceramic fibers, organic fibers, inorganic fibers, polymer fibers, oxide fibers, glassy fibers, glass fibers, amorphous fibers, crystalline fibers, non-oxidized fibers, carbide fibers, metal fibers, etc. Inorganic fiber structures, or combinations thereof. However, for the sake of clarity, it is expected that other fibers could be used, but the use of ceramic fibers has been described. In addition, although other uses are contemplated and are within the scope of the present teachings, the support is often considered a filter media support or a catalyst support. The designer selects a specific type of fiber based on the specific needs of the application. For example, ceramic fibers may be selected as mullite fibers, aluminum silicate fibers, or other commonly available ceramic fiber materials. The fiber specifically needs to be processed 14 to cut the fiber to an available length, and it may include shredding before mixing the fiber with the additive. Furthermore, various mixing and shaping steps in the extrusion process further cut the fibers.

  Additive 16 is added according to specific requirements. These additives 16 can include binders, dispersants, pore forming components, plasticizers, processing aids, and reinforcing materials. In addition, fluid 18, typically water, is combined with additive 16 and fiber 12. The fibers, additives and fluid are mixed 21 until extrudable rheology. This mixing can include dry mixing, wet mixing, and shear mixing. The fibers, additives, and fluid are mixed until a homogeneous mass is produced, which distributes and arranges the fibers evenly within the mass. The fibrous and homogeneous mass is then extruded to form a green substrate 23. The green body carriers are strong enough to hold each other throughout the rest of the processing.

  Thereafter, the green substrate carrier is cured 25. As used in this description, “curing” is defined to include two important processing steps. 1) binder removal, and 2) bond formation. The binder removal process removes water, removes most additives, and allows fiber-to-fiber contact. Often, a heating step that burns off the binder is used to remove the binder, but it will be appreciated that other removal processes may be used, depending on the particular binder used. For example, transpiration or sublimation processes can be used to remove certain binders. Certain binders and / or other organic components may melt prior to decomposition into the gas phase. As the curing process continues, a fiber-to-fiber bond is formed. These bonds promote overall structural rigidity as well as create the desired porosity and permeability of the carrier. Accordingly, the cured carrier 30 is a very porous carrier of generally fibers that are bonded to the open pore network 30. The support can then be used as a support for many applications, including as a support for filter media applications and catalytic converter applications. Advantageously, the system 10 has allowed a desirable extrusion process to produce a carrier having a porosity of up to about 90%.

  With reference now to FIG. 2, an extrudable material 50 is illustrated. The extrudable material 50 can be immediately extruded from an extruder such as a piston or shaft extruder. The extrudable mixture 52 is a homogeneous mass containing fibers, plasticizers, and other additives as required by the particular application. FIG. 2 shows an enlarged portion 54 of a homogeneous mass. It will be appreciated that the enlarged portion 54 may not be drawn to expand, but is provided as an aid to the present description. The extrudable mixture 52 contains fibers such as fibers 56, 57 and 58. These fibers were selected to produce a very porous and rigid final support that exhibited the desired thermal, chemical, mechanical, and filtration characteristics. As will be appreciated, the substantially fibrous bodies were not considered extrudable because they did not exhibit their own plasticity. However, it has been found that the extrudable mixture 52 containing fibers can be extruded through appropriate selection of plasticizers and process control. In this regard, the cost, scale, and flexibility benefits of extrusion can range from using a fibrous material to including available benefits.

  In general, fibers are considered a material having a relatively small diameter that exhibits an aspect ratio greater than one. Aspect ratio is the ratio of fiber length divided by fiber diameter. As used herein, the “diameter” of a fiber is simply considered to be a circular cross-sectional shape of the fiber. This concise assumption applies to the fibers regardless of their true cross-sectional shape. For example, a fiber exhibiting an aspect ratio of 10 has a length that is 10 times the diameter of the fiber. Diameters ranging from about 1 micron to about 25 microns are fully available, but the fiber diameter can be 6 microns. It can be seen that many different diameter and aspect ratio fibers can be successfully used in the system 10. As will be shown in more detail with respect to the subsequent figures, there are several alternatives for selecting the aspect ratio for the fibers. It can also be seen that the fiber shape is in contrast to a typical ceramic powder in which the aspect ratio of each ceramic particle is approximately 1.

  Although FIG. 2 is discussed with respect to ceramic fibers, the fibers of the extrudable mixture 52 can be metallic (often referred to as thin diameter metallic wires). The ceramic fibers can be in an amorphous state, a glassy state, a crystalline state, a polycrystalline state, a single crystalline state, or a glass-ceramic state. In making the extrudable mixture 52, a relatively low volume of ceramic fibers is used to make the porous support. For example, the extrudable mixture 52 may have a ceramic fiber material limited to about 10% to 40% by volume. In this regard, after curing, the resulting porous carrier exhibits a porosity of about 90% to about 60%. It will be appreciated that other amounts of ceramic fiber material may be selected to produce other porosity values.

  In order to produce an extrudable mixture, the fibers are combined in particular with a plasticizer. In this way, the fiber is combined with other selected organic or inorganic additives. These additives provide three important properties for the extrudate. First, the additive causes the extrudable mixture to exhibit an appropriate rheology for extrusion. Secondly, until these additives are removed during the curing process, they are generally referred to as green substrates that retain their form and are strong enough to position the fibers. An extruded carrier is provided. And third, the additive is selected to burn off in the curing process in a way that promotes the alignment of the fibers into an overlapping structure and in a way that does not weaken the rigid structure being formed. In general, the additive includes a binder, such as binder 61. The binder 61 acts as a medium that holds the fibers in position and provides strength to the green carrier. Fiber and binder (s) can be used to produce a porous carrier that exhibits a relatively high porosity. However, in order to further increase the porosity, other pore-forming components such as the pore-forming component 63 can be added. In order to increase the open space in the final cured carrier, a pore-forming component is added. The pore-forming component can be in shape, spherical, oval, fibrous or irregular. Not only their ability to create open spaces, their ability to be based on their pyrolytic action, but also the pore-forming components that help in orienting the fibers. In this regard, the pore-forming component helps in aligning the fibers in an overlapping pattern that promotes proper bonding between the fibers during the later stages of curing. In addition, the pore-forming component also plays a role in the fiber orientation in the preferred direction, which affects the thermal expansion and strength of the extruded material along various axes.

  As briefly indicated above, the extrudable mixture 52 may use one or more fibers selected from many types of available fibers. Further, the selected fibers can be combined with one or more binders selected from a wide variety of binders. In addition, one or more pore-forming components selected from a wide variety of pore-forming components can be added. The extrudable mixture can use water or other fluid as its plasticizer and can have other additives added. This flexibility in product chemistry allows the extrudable mixture 52 to be used advantageously in many different types of applications. For example, the mixture combination may be selected according to the required environmental, temperature, chemical, physical, or other requirement needs. Further, since the extrudable mixture 52 can be extruded immediately, the final extruded product can be formed flexibly and economically. Although not shown in FIG. 2, the extrudable mixture 52 is extruded through a shaft or piston extruder to form a green carrier, which is then cured into a final porous carrier product.

  The present invention represents the pioneering use of fiber materials in plastic batches or mixtures for extrusion. This fibrous extrudable mixture allows for the extrusion of supports exhibiting very high porosity in a scalable production and in a cost-effective manner. By allowing the fibers to be used in a repeatable and rigid extrusion process, the present invention allows mass production of filter media and catalyst supports for a wide range of applications around the world.

  With respect to FIG. 3A, an enlarged cured region of the porous support is shown. The carrier portion 100 is shown after the binder removal 102 and after the curing step 110. After binder removal 102, fibers such as fibers 103 and 104 are initially held in position with the binder material, and when the binder material burns off, the fibers are overlapping but unwound. Exposed as it is in the structure. In addition, the pore-forming component 105 can be positioned to create another open space and to align and align the fibers. Many open spaces 107 exist between the fibers because the fibers only contain a relatively small amount of the extrudable mixture. Once the binder and pore-forming components are burned off, the fibers can be slightly adjusted for further contact with each other. The binder and pore-forming component are selected to break off the fiber array or to burn off with control means so as not to collapse the support during burn-off. In particular, the binder and pore-forming components are selected to decompose or burn off before forming the bonds between the fibers. As the curing process continues, overlapping and contacting fibers begin to bond. It can be seen that the bond can be formed in several ways. For example, the fibers can be heated until they form a liquid-assisted sintered bond at the fiber intersection or node. This liquid phase sintering can occur from selected specific fibers, or can occur from another additive that is added to the mixture or coated onto the fibers. In other cases, it may be desirable to form a solid phase sintered bond. In this case, the intersection bond forms a particle structure that connects the overlapping fibers. In the green state, the fibers have not yet formed a physical bond with each other, but may still exhibit some raw material strength due to the entanglement of the fibers with each other. The particular type of bond chosen will depend on the choice of substrate material, desired strength, and operating chemistry or environment. In certain cases, bonding is caused by the presence of an inorganic binder and provides a mixture that holds the fibers together in a connected network and does not burn off during the curing process.

  Advantageously, the formation of a bond, such as bond 112, facilitates forming a substantially rigid structure with the fibers. Bonding also allows the formation of open pore networks that exhibit very high porosity. For example, the open space 116 is naturally created by the space between the fibers. The open space 114 is created when the pore-forming component 105 decomposes or burns off. In this regard, the fiber bond forming process creates an open pore network that is free or substantially free of termination paths (channels). This open pore network generates high permeability, high filtration efficiency and allows for a high surface area, for example for the addition of catalysts. It will be appreciated that bond formation depends on the type of bond desired, such as solid phase or liquid assisted / liquid phase sintering, and additives may be present during the curing process. For example, additives, specific fiber selection, heating time, degree of heating, and reaction environment can all be adjusted to create a specific type of bond.

  Referring now to FIG. 3B, another enlarged cured region of the porous carrier is shown. Carrier portion 120 is shown after binder removal 122 and after curing step 124. The carrier portion 120 is similar to the carrier portion 100 shown with respect to FIG. 3A and is therefore not shown in detail. The carrier 120 was formed without the use of specific pore-forming components, so that a fully open pore network 124 resulted from fiber positioning with the binder material. In this regard, moderately high porosity carriers are formed without the use of any specific porosity forming component, thereby reducing the cost and complexity of producing such medium porosity carriers. sell. It has been found that carriers exhibiting porosity ranging from about 40% to about 60% can be produced in this manner.

  Now referring to FIG. 4, a collection 150 of electron micrographs is shown. The photograph collection 150 first shows an open pore network 152 that is optionally created using a fibrous extrudable mixture. As can be seen, the fibers form bonds at the fiber nodes at the intersections and burn off the pore-forming components and binder and release the porous open pore network. In strong light and dark, photograph 154 shows a typical closed cell network made using known processes. A partially closed pore network exhibits a relatively high porosity, but at least some of the porosity is derived from the closed path. These closed paths do not contribute to permeability. In this regard, open pore networks, closed pore networks exhibiting the same porosity, and open pore networks exhibit more desirable permeability characteristics.

  The generally indicated extrudable mixtures and processes are very advantageous and are used to produce porous supports. In one example, the porous support can be extruded into the filter media block support 175 as shown in FIG. The carrier block 175 was extruded using a piston or shaft extruder. The extruder can be adjusted to operate at room temperature, slightly elevated temperature, or in a controlled temperature window. In addition, some portions of the extruder can be heated to various temperatures that affect the retarding characteristics, shear history, and gelling characteristics of the extrusion mixture. Furthermore, the size of the extrusion die can also be sized by adjusting the expected shrinkage in the support during the heating and sintering process. Conveniently, the extrudable mixture was a fibrous extrudable mixture with sufficient plasticizer and other additives to allow the fibrous material to be extruded. The extruded raw block was cured to remove free water, burn off the additives, and form structural bonds between the fibers. The resulting block 175 has highly desirable porosity characteristics, as well as excellent permeability and highly available surface area. Further, depending on the particular fibers and additives selected, a block 175 for advantageous depth filtration can be constructed. Block 176 has a path 179 extending longitudinally through the block. The inlet to block 178 may remain open for the flow-through process, or each other opening may be plugged to create a wall flow effect. Although a block 175 having a hexagonal path is shown, it will be appreciated that other patterns and sizes may be used. For example, a square, rectangular, or triangular path pattern made to an equal size; a square / rectangular or octagonal / quadrature path pattern with a large inlet path; or a path that exhibits another symmetric or asymmetric path pattern Can be formed. By adjusting the die design, the exact shape and size of the path or cell can be adjusted. For example, a square path can be bent at the corners by using EDM (Electro Electrical Discharge Machining) to form pins in the die. Such rounded corners are expected to increase the strength of the final product despite the slightly higher back pressure. Further, the die design can be modified so that the walls exhibit various thicknesses and the skin extrudes a honeycomb carrier having a different thickness than the remaining walls. Similarly, in some applications, the skin may be applied to an extruded carrier for the final definition of size, shape, profile and strength.

  When used as a flow-through device, the high porosity block 176 allows a large surface area for catalytic material applications. In this respect, a very effective and sufficient catalytic converter can be made and the converter has a low thermal mass. With such a low thermal mass, the resulting catalytic converter has excellent quenching characteristics and effectively uses catalytic materials. When used in the example of wall flow or wall filtration, the high permeability of the carrier wall allows for relatively low back pressure while facilitating depth filtration. This depth filtration allows for sufficient particle removal as well as promoting more effective regeneration. With the wall flow design, the fluid flowing through the carrier is moved through the wall of the carrier, thus allowing more direct contact with the fibers that make up the wall. These fibers exhibit a high surface area where a strong reaction occurs, such as when a catalyst is present. Since the extrudable mixture can be formed from a wide variety of fibers, additives, and fluids, the chemistry of the extrudable mixture can be adjusted to generate blocks that exhibit certain characteristics. For example, the final block, if desired as a diesel particulate filter medium, selects fibers that ensure safe operation even at uncontrolled regeneration extreme temperatures. In another example, if the block is to be used to filter a particular type of exhaust gas, the fibers and bonds are selected so that they do not react with the exhaust gas over the expected operating temperature range. The Although the advantages of high porosity supports have been described with respect to filter media and catalytic converters, it is recognized that there are many other applications for high porous supports.

  As described with respect to FIG. 2, the fibrous extrudable mixture can be formed from a wide variety of substrate materials. The selection of the appropriate material is generally based on the chemical, mechanical, and environmental conditions that the final support must operate on. Thus, the first step in designing a porous support is to understand the end use for the support. Based on these requirements, specific fibers, binders, pore forming components, fluids and other materials may be selected. It is also recognized that the process applied to the selected material can affect the final carrier product. Since fiber is the primary structural material in the final carrier product, the choice of fiber material is important because the final carrier can be run in its intended application. Thus, the fibers are selected according to the required bonding requirements and select a specific type of bonding process. The bonding process can be liquid phase sintering, solid phase sintering, or bonding that requires a binder such as a glass forming component, glass, clay, ceramic, ceramic precursor or colloidal sol. The binder can be part of a component in the fiber construction, one of the coatings on the fiber, or one of the additives. It will also be appreciated that more than one type of fiber may be selected. It is also recognized that some fiber can be consumed during the curing and bonding process. In selecting the fiber composition, the final operating temperature is an important concern because it can maintain the thermal stability of the fiber. In another example, the fibers are selected such that they remain chemically inert or non-reactive in the presence of the expected gas, liquid or solid particulate matter. Depending on its cost, fibers can be selected, and certain fibers may be health concerns due to their small size, and therefore may avoid their use. Depending on the mechanical environment, the fibers are selected for their ability to form a strong rigid structure as well as maintain the required mechanical integrity. It will be appreciated that the selection of an appropriate fiber or set of fibers may be involved in performance and application replacement conditions. FIG. 6, Table 1 shows several types of fibers used to form a fibrous extrudable mixture. In general, the fibers can be oxide or non-oxide ceramic, glass, organic, inorganic, or they can be metallic. For ceramic materials, the fibers can be in various states such as amorphous, glassy, polycrystalline or single crystalline. Table 1 shows a number of available fibers, but it will be appreciated that other types of fibers may be used.

  The binder and pore-forming component can then be selected depending on the type of fiber selected, as well as other desired characteristics. In one example, a binder is selected that promotes a particular type of liquid phase bonding between selected fibers. More specifically, the binder has components that react at the bonding temperature to promote the flow of liquid connected to the nodes of the intersection fiber. In addition, the binder is selected for its ability to plasticize the selected fiber and maintain its raw strength. In one example, the binder is also selected according to the type of extrusion to be used and the temperature required for the extrusion. For example, certain binders, when overheated, form a gel mass and can therefore only be used in the low temperature extrusion process. In another example, the binder may be selected by its impact on shear mixing characteristics. In this regard, the binder may facilitate chopping the fibers to the desired aspect ratio during the mixing process. The binder can also be selected by its decomposition or burn-off characteristics. Binders generally need to be able to hold the fibers in place and do not disrupt the fiber structure being formed during burn-off. For example, if the binder burns off too quickly or violently, the escape gas can disrupt the structure being formed. Furthermore, after burnout, the binder can be selected depending on the amount of residue left behind by the binder. Some applications can be very sensitive to such residues.

  A pore-forming component may not be required for the formation of a relatively moderate porosity. For example, the natural alignment and filling of the fibers in the binder can work together to allow a porosity of about 40% to about 60%. In this regard, a moderately porous support can be generated using an extrusion process without the use of pore-forming components. In some cases, removal of the pore-forming component makes it possible to produce a more economical porous support when compared to known processes. However, if a porosity greater than about 60% is required, a pore-forming component can be used to create another space in the carrier after curing. The pore-forming components can also be selected by their decomposition or burn-off characteristics, and can also be selected by their size and shape. The pore size can be important, for example, to capture specific types of particulate matter or to allow particularly high permeability. The shape of the pores can also be adjusted, for example, to assist with proper alignment of fibers. For example, a relatively elongated pore shape can align the fibers in a more ordered pattern, while a more irregular or spherical shape can cause the fibers to be arranged in a more arbitrary pattern.

  The fiber is supplied by the manufacturer as a chopped fiber and can be used directly in the process, or the fiber can be provided in a bulk format, which is generally processed prior to use. In either method, processing considerations should take into account how the fiber is processed into its final desired aspect ratio distribution. In general, the fibers are first chopped prior to mixing with other additives and then further chopped during the mixing, shearing, and extrusion steps. However, extrusion can be performed during extrusion mix using unchopped fibers and when placed under pressure on the extrusion die surface by setting the rheology to make an extrudable mix that can be extruded at a reasonable extrusion pressure. It can also be carried out without causing an expansion flow. It will be appreciated that chopping the fibers to an appropriate aspect ratio distribution can be performed at various times throughout the process. Once the fiber is selected and chopped to an available length, it is mixed with the binder and pore forming component. This mixing can be done initially in dry form to initiate the mixing process or as a wet mixing process. A fluid, typically water, is added to the mixture. To obtain the required level of uniform distribution, the mixture is shear mixed through one or more stages. Shear mixing or dispersive mixing provides a highly desirable homogeneous mixing process for evenly distributing the fibers in the mixture as well as cutting the fibers further to the desired aspect ratio.

  FIG. 6 Table 2 shows some binders available for selection. It will be appreciated that a single binder may be used, or multiple binders may be used. Binders are generally divided into organic and inorganic classifications. Organic binders are generally burned off at low temperatures during curing, while inorganic binders form part of the final structure, especially at high temperatures. Some binder choices are listed in Table 2, but it will be appreciated that several other binders may be used. FIG. 6 Table 3 shows a list of available pore-forming components. The pore-forming component is generally defined as organic or inorganic, and organics are burned off at a lower temperature than inorganic ones in particular. Some pore forming components are listed in Table 3, but it will be appreciated that other pore forming components may be used. FIG. 6 Table 4 shows various fluids that can be used. While it is recognized that water can be the most economical and frequently used fluid, certain applications may require other fluids. Table 4 shows some fluids that may be used, but it will be appreciated that other fluids may be selected depending on the particular application and process requirements.

  In general, the mixture can be adjusted to have the appropriate rheology for advantageous extrusion. In particular, suitable rheology results from the proper selection and mixing of fibers, binders, dispersants, plasticizers, pore-forming components and fluids. A high degree of mixing is required to moderately impart plasticity to the fibers. Once the appropriate fibers, binders and pore-forming components are selected, the amount of fluid is finally adjusted, especially to suit the appropriate rheology. Appropriate rheology may be demonstrated, such as by one of two tests. The first test is a subjective and informal test in which the beads of the mixture are removed and formed between the fingers of a skilled extrusion operator. The operator can identify when the mixture is properly displaced between the fingers and indicates that the mixture is under the proper conditions for extrusion. A second more objective test is by measuring the physical characteristics of the mixture. In general, a confined (ie, high pressure) tubular flow meter can be used to measure shear strength versus compression pressure. Measurements are made and filled in by comparing the adhesion strength vs. pressure dependence. By measuring the mixture at various mixtures and concentrations of the fluid, a rheological diagram can be created that identifies the rheological points. For example, FIG. 6 of Table 5 shows a rheological diagram for a fibrous ceramic mixture. Axis 232 shows the adhesive strength and axis 234 shows the pressure dependence. The extrudable area 236 represents an area where fibrous extrusion is very likely. Thus, the mixture characterized by any measurement that falls within region 236 is likely to be successfully extruded. Of course, it can be seen that the rheological diagram involves a number of variables, and thereby several variables should be expected in the positioning of region 236. In addition, there are several other direct and indirect tests to measure rheology and plasticity, and many of those tests are arranged to see if the mixture exhibits the correct rheology for it. Thus, it is recognized that it can be extruded into the final shape of the desired product.

  Once the proper rheology is reached, the mixture is extruded through an extruder. The extruder can be a piston extruder, a single screw extruder, or a twin screw extruder. The extrusion process can be highly automated or can require human intervention. The mixture is extruded through a die that exhibits the desired cross-sectional shape for the carrier block. A die was selected that satisfactorily formed a green body carrier. In this regard, a stable green body carrier is made that can be handled throughout the curing process while maintaining its shape and fiber alignment.

  Thereafter, the green carrier is dried and cured. Drying can be done in room conditions, at controlled temperature and humidity conditions (such as in a controlled oven), in a microwave oven, in an RF oven, and in a convection oven. Curing generally requires the removal of free water to dry the green carrier. It is important to dry the green support with control means so as not to introduce cracks or other structural defects. Thereafter, the temperature can be raised to burn off additives such as binders and pore-forming components. The temperature is controlled to ensure that the additive is burned off by the control means. It will be appreciated that additive burn-off may require a period of temperature through various timed cycles and levels of heat. Once the additive is burned off, the support is heated to the required temperature to form a structural bond at the fiber intersection or node. Select the required temperature according to the required bond type and fiber chemistry. For example, liquid assisted sintered bonds are formed at a lower temperature than solid phase bonds, among others. It will also be appreciated that the amount of time at the binding temperature can be adjusted depending on the particular type of bond to be produced. Full thermal cycles can be performed in the same furnace, in different furnaces, in batch or continuous processes, and under air or controlled atmosphere conditions. After forming the fiber bond, the support is slowly cooled to room temperature. It will be appreciated that the curing process can be accomplished in one oven or multiple ovens / furnace and can be automated in a production oven / furnace such as a tunnel kiln.

  Referring now to FIG. 7, a system for extruding a porous carrier is shown. System 250 is a very flexible process for producing porous carriers. In order to design the carrier, carrier requirements are defined as indicated by block 252. For example, the end use of the support generally defines the support requirements, which can include size constraints, temperature constraints, strength constraints, and chemical reaction constraints. Further, the cost and mass productivity of the carrier can determine and operate a given choice. For example, high production rates can cause relatively high temperatures in the extrusion die, and therefore select binders that operate at high temperatures without curing or gelling. For extrusion using a high temperature binder, the die and barrel may need to be maintained at a relatively high temperature, such as from 60 to 180 ° C. In such cases, the binder can melt to reduce or eliminate the need for another fluid. In another example, the filter media can be designed to trap particulate matter, where fibers are selected that remain unreactive with the particulate matter, even at high temperatures. It will be appreciated that a wide range of applications can be accommodated with a wide range of possible mixtures and processes. Those skilled in the art will recognize the exchange conditions involved in selecting the fiber, binder, pore forming component, fluid and processing stage. In fact, one of the obvious advantages of the system 250 is its flexibility with respect to the choice of the mixture composition and the adjustment of its process.

Once the carrier requirements are defined, the fibers are selected from Table 1 of FIG. 6 as indicated by block 253. The fibers can be of a single type or can be a combination of two or more types. It will also be appreciated that some fibers may be selected that are consumed during the curing process. In addition, additives can be added to the fiber to introduce other materials into the mixture, such as a coating on the fiber. For example, a dispersion agent can be applied to the fibers to facilitate fiber separation and alignment, or a binding aid can be coated on the fibers. In the case of a binding aid, when the fiber reaches the curing temperature, the binding aid assists in the formation and flow of liquid phase bonds.

  Thereafter, as indicated by block 255, a binder is selected from Table 2 of FIG. Select a binder that promotes the strength of the green state as well as controlled burn-off. In addition, a binder is selected that produces sufficient plasticity in the mixture. If required, the pore forming component is selected from Table 3 in FIG. 6 as indicated by block 256. In some cases, sufficient porosity can be obtained through the use of only fibers and binders. Porosity is achieved not only by the natural filling characteristics of the fibers, but also by the space occupied by binders, solvents and other volatile components released during the debinding and curing stages. In order to achieve a high porosity, another pore-forming component can be added. Their controlled burn-off capacity may also select the pore-forming components and assist in plasticizing the mixture. A fluid, typically water, is selected from Table 4 in FIG. Dispersants to assist in fiber separation and alignment, and other liquid materials such as plasticizers and extrusion aids to improve the flow behavior of the mixture may be added. This dispersant can be used to adjust the surface charge on the fiber. In this regard, the fibers can have their charge controlled to cause the individual fibers to repel each other. This promotes a more homogeneous and arbitrary distribution of fibers. A typical composition for a mixture intended to make a support exhibiting> 80% porosity is shown below. It will be appreciated that the mixture will be adjusted depending on the target porosity, specific application, and processing considerations.

  As indicated at block 254, the fibers selected at block 252 should be processed to exhibit an appropriate aspect ratio distribution. This aspect ratio is preferably in the range of about 3 to about 500 and may exhibit one or more embodiments of distribution. For example, it will be appreciated that other ranges can be selected around an aspect ratio of 1000. In one example, the aspect ratio distribution can be arbitrarily distributed throughout the desired range, and in another example, the aspect ratio can be selected with further distinct aspect values. Aspect ratio has been found to be an important factor in defining the filling characteristics of fibers. Thus, the aspect ratio and aspect ratio distribution are selected to implement specific strength and porosity requirements. Furthermore, it will be appreciated that processing the fibers to their preferred aspect ratio distribution can be done at various points in the processing. For example, the fibers can be cut by a third-party processing device and released with a predetermined aspect ratio distribution. In another example, the fibers can be supplied in a bulky form and processed to the appropriate aspect ratio as a primary step in the extrusion process. It will be appreciated that the mixing, shear mixing or dispersive mixing, and extrusion aspects of step 250 can also contribute to fiber cutting and chopping. Thus, the aspect ratio of the fibers initially introduced into the mixture is different from the aspect ratio in the final cured carrier. Accordingly, the shredding and cutting effects of mixing, shear mixing, and extrusion should be considered when selecting the appropriate aspect ratio distribution 254 to be introduced into the process.

  With fibers processed to an appropriate aspect ratio distribution, the fibers, binder, pore forming component and fluid are mixed into a homogeneous mass as indicated by block 262. This mixing step may include a dry mixing aspect, a wet mixing aspect, and a shear mixing aspect. It has been found that shearing or dispersive mixing is desirable to produce a very homogeneous distribution of fibers within the mass. This distribution is particularly important due to the relatively low concentration of ceramic material in the mixture. When the homogeneous mixture is to be mixed, the rheology of the mixture can be adjusted as indicated by block 264. As the mixture is mixed, its rheology continues to change. The rheology can be tested subjectively or can be measured depending on the desired area as shown in Table 5 of FIG. Mixtures that fall within this desired area are likely to be properly extruded. The mixture is then extruded into a green substrate carrier as indicated by block 268. In the case of a screw extruder, the mixing can take place inside the extruder itself rather than in a separate mixer. In such cases, the shear history of the mixture should be carefully managed and controlled. The green body carrier exhibits sufficient green strength to retain its shape and fiber alignment during the curing process. The green body carrier is then cured as indicated by block 270. The curing process includes removal of any residual water, controlled burn-off of most additives, and formation of fiber-to-fiber bonds. During the burn-off process, the fibers maintain their intertwined and intersecting relationship, and as the curing process proceeds, bonds are formed at the intersections or nodes. It will be appreciated that the binding can result from a liquid phase or solid phase binding process. Furthermore, it can be seen that some of the bonds may be due to reaction with the binder, the pore-forming component, as a coating on the fiber, or with additives that are themselves provided in the fiber. After the bond is formed, the support is slowly cooled to room temperature.

  Now referring to FIG. 8, a method of curing a porous fibrous carrier is shown. The method 275 has a green body carrier having a fibrous ceramic content. The curing process initially slowly removes residual water from the carrier as indicated at block 277. In particular, water removal can be performed in an oven at a relatively low temperature. After removing residual water, the organic additive may be burned off as indicated at block 279. These additives are burned off in a controlled manner that promotes proper alignment of the fibers and ensures that escaped gases and residues do not interfere with the fiber structure. When the additives are burned off, the fibers maintain their overlapping arrangement and may further contact at the intersection or node as indicated by block 281. The fibers can be positioned in these overlapping arrays using a binder and exhibit a specific pattern formed through the use of a pore-forming component. In some cases, inorganic additives that can be combined with the fibers could be used, consumed during the bond formation process, or remain part of the final support structure. The curing process proceeds as shown by block 285 to form a fiber-to-fiber bond. The specific timing and temperature will require a bond to be made depending on the type of fiber used, the type of binding aid or agent used, and the type of bond desired. In one example, the bond may be a liquid phase sintered bond that occurs between the fibers as indicated by block 286. Such bonding is supported by glass forming components, glasses, ceramic precursors or inorganic fluxing agents present in the system. In another example, as shown in block 288, a sintering aid or agent may be used to create a liquid phase sintered bond. Sintering aids can be provided as coatings on the fibers, as additives, from binders, from pore-forming components, or from the chemistry of the fibers themselves. Further, fiber-to-fiber bonds can be formed by solid phase sintering between the fibers as indicated by block 291. In this case, the intersecting fibers exhibit particle growth and mass transfer and lead to the formation of chemical bonds at the nodes and overall rigid structure. In the case of liquid phase sintering, the mass of the binding material accumulates at the fiber intersection and forms a rigid structure. It will be appreciated that the curing process can be performed in one or more ovens and can be automated in an industrial tunnel or kiln type furnace.

  Now referring to FIG. 9, the process of manufacturing the fiber is shown. Process 300 illustrates receiving bulk fibers as indicated by block 305. Bulk fibers typically have very long fibers in a bulk and interwoven arrangement. Such bulk fibers must be processed to sufficiently separate and cut the fibers for use in the mixing process. Accordingly, the bulk fibers are mixed with water 307 and possibly with dispersant 309 to form slurry 311. The dispersant 309 can be, for example, a pH or charge control agent that assists the fibers in repelling each other. It will be appreciated that several different types of dispersants can be used. In one example, the bulk fibers are coated with a dispersant before being introduced into the slurry. In another example, the dispersant is simply added to the slurry mixture 311. As shown in block 314, the slurry mixture is mixed vigorously. This vigorous mixing has the effect of shredding and separating the bulk fibers into an available aspect ratio distribution. As indicated above, since the mixing and extrusion process further shreds the fiber, the aspect ratio for the original use of the fiber differs from the distribution in the final carrier.

  After the fibers have been chopped to an appropriate aspect distribution, most of the water is removed using a filter media press 316 or in other devices by applying pressure to the filter media. It will also be appreciated that other water removal steps may be used, such as lyophilization. The filter media press may use pressure, vacuum or other means to remove water. In one example, as shown at block 318, the chopped fibers are further dried to complete dryness. These dry fibers can then be used in a dry mixing step 323 where they are mixed with other binders and dry pore forming components as indicated by block 327. This initial dry mixing helps to produce a homogeneous mass. In another example, the moisture content of the filtered fiber is adjusted for proper moisture content, as indicated by block 321. More particularly, as shown at block 325, sufficient water is left in the chopped fiber cake to facilitate wet mixing. It has been found that further separation and distribution of the fibers can be obtained by using the fibers to release some slurry water. Binders and pore-forming components can also be added during the wet mixing stage, and water 329 can be added to obtain the correct rheology. As indicated by block 332, the mass is also shear mixed. Shear mixing may be performed by passing the mixture through a spaghetti die using a screw extruder, twin screw extruder, or shear mixer (such as a Sigma blade type mixer). Shear mixing can occur in sigma mixers, high shear mixers, and even inside screw extruders. A shear mixing process is desirable to create a more homogeneous mass 335 that exhibits the desired plasticity and extrudable rheology for extrusion to work. Homogeneous mass 335 shows a uniform distribution of fibers and the fibers are positioned in the overlapping matrix. In this regard, the fibers are bonded to the rigid structure when the homogeneous mass is extruded into a carrier block and cured. In addition, this rigid structure forms an open pore network that exhibits high porosity, high permeability, and high surface area.

  Now referring to FIG. 10, a method of producing a tilted carrier block is shown. Step 350 is designed to allow the manufacture and extrusion of carrier blocks that exhibit tilt characteristics. For example, a carrier having a first material towards the center of the block and a different material towards the outside of the block can be produced. In a more specific example, a material that exhibits a low coefficient of thermal expansion is used, particularly toward the center of the block where a high heat is expected, while a material that exhibits a relatively high coefficient of thermal expansion may have a low heat. Use in the expected outer area. In this regard, a more homogenized expansion characteristic can be maintained for the overall block. In another example, selected areas of the block may have a high density ceramic material to provide increased structural support. These structural support members may be arranged concentrically on the block or arranged on an axis. Thus, a particular material may be selected depending on the porosity, pore size, or desired gradient in chemistry according to application requirements. In addition, tilting can cause the use of more than two materials.

  In one example, the ramp structure can be produced by providing a cylinder of the first material 351. As shown by the illustration 355, a sheet-like second material 353 wraps around the cylinder 351. At this point, layer B353 becomes a concentric tube around the inner cylinder 351. The layered cylinder 355 is then placed in a piston extruder, evacuating air and pushing the mass through a die. During the extrusion process, the material mixes at the interface between material A and material B and promotes a seamless interface. Such an interface allows fiber overlap and bonding between two different types of materials, thereby promoting a strong overall structure. Once the material is extruded, cured and filled, it produces a filter media or catalytic converter package 357 with a gradient carrier. More specifically, the A material is formed at the center of the carrier while the B material 361 is formed at the outer portion. It will be appreciated that more than two materials can be used and that pore size, porosity, and chemical characteristics can be gradually adjusted.

  Referring now to FIG. 11, another step 375 is shown for making a gradient carrier. In step 375, a first cylinder 379 is provided near the size of the piston extrusion barrel. In one example, outer cylinder 379 is the actual barrel used in a piston extruder. An inner tube 377 having a smaller diameter than the outer tube 379 is provided. The tubes are arranged concentrically to position the inner tube 377 concentrically inside the tube 379. The pellets of the first extrudable mixture material 383 are deposited inside the tube 377 while the pellets of the second extrudable mixture material 381 are deposited in the ring between the tube 377 and the tube 379. The inner tube is carefully removed so that material A is concentrically surrounded by material 381. The array of materials is then placed in an extrusion piston, the air is removed in vacuo and extruded through a die. Once extruded, cured and filled, it produces a graded carrier as shown with respect to FIG. It will be appreciated that more than two concentric rings can be made and that various types of tilt can be produced.

  Turning now to FIG. 12, another method of making a tilted carrier is shown. The method 400 has a column of extrudable mixture 402 having two extrudable material replacement discs. The extrudable mixture 402 has a first material 403 adjacent to a second material 404. In one example, material A is relatively porous while material B is less porous. During extrusion, the material flows through the extrusion die and mixes the fibers obtained from the A and B parts in an overlapping arrangement. At this point, each A and B portion is joined together to form a fibrous carrier block. The filter medium 406 is produced by curing and filling. The filter media 406 has a first portion 407 that exhibits a relatively high porosity and a second portion 408 that exhibits a low porosity. At this point, the gas flow through the filter media 406 is first filtered through a high porosity region that exhibits a large pore size and then through a low porous region that exhibits a small pore size. In this regard, large particles are captured in region 407 while small particles are captured in region 408. It will be appreciated that the size and number of material disks can be adjusted according to the application needs.

  The fiber extrusion system provides excellent flexibility in the tool. For example, a wide range of fibers and additives can be selected to form a mixture. There are several mixing and extrusion options, and the options are related to the curing method, timing and temperature. With the disclosed teachings, one of ordinary skill in the extrusion arts can appreciate that many variations can be used. Honeycomb carriers are a common design to be manufactured using the techniques described in the present invention, but other shapes, sizes, profiles, designs can be extruded for various applications.

  Filtration device (DPF, oil / air filter, hot gas filter, air filter, water filter, etc.) or catalytic device (3-way catalytic converter, SCR catalyst, deozonizer, deodorizer, biological reactor, chemical reactor, oxidation For certain applications, such as applications such as catalysts, it may be necessary to plug the path in the extruded carrier. A material similar in composition to the extruded carrier is used to plug the carrier. The plugging can be performed in the raw material state or on the sintered carrier. Most seal plug compositions require a heat treatment to cure and bond to the extruded carrier.

  When disclosing particularly preferred and alternative embodiments of the present invention, many different modifications and extensions of the techniques set forth above may be implemented using the teachings of the present invention set forth herein. Will be apparent to those skilled in the art. All such modifications and extensions are intended to be within the true concept and scope of the invention as discussed in the appended claims.

The drawings form part of the present specification and include exemplary embodiments of the present invention that may be embodied in various forms. It should be understood that in certain instances, various aspects of the invention may be exaggerated and enlarged to assist in understanding the invention.
1 is a block diagram of a system for extruding a porous carrier according to the present invention. 2 is an illustration of a fibrous extrudable mixture according to the present invention. 2 is an illustration of an open pore network according to the present invention. 2 is an illustration of an open pore network according to the present invention. 2 is an electron micrograph of an open pore network according to the present invention and a prior art closed pore network. It is an illustration of the filter media block using the porous support | carrier by this invention. 1 is a table of fibers, binders, pore forming components, fluids, and rheology useful in the present invention. 1 is a block diagram of a system for extruding a porous carrier according to the present invention. 1 is a block diagram of a system for curing a porous carrier according to the present invention. 1 is a block diagram of a system for processing fibers of a porous carrier according to the present invention. FIG. 3 is a diagram relating to extruding a tilted porous carrier according to the present invention. FIG. 3 is a diagram relating to extruding a tilted porous carrier according to the present invention. FIG. 3 is a diagram relating to extruding a tilted porous carrier according to the present invention.

Claims (108)

A ceramic material consisting essentially of elongated fibers,
Binder material,
An extrudable mixture that includes a fluid and wherein the elongated fibers, binder material and fluid are a homogeneous mass.   The extrudable mixture of claim 1 wherein the ceramic material is less than about 20% of the volume of the homogeneous mass.   The extrudable mixture of claim 1, wherein the extrudable mixture further comprises an inorganic clay, nanoclay, colloid, glass or non-fibrous ceramic precursor.   The extrudable mixture of claim 1 wherein the ceramic material is less than about 40% of the volume of the homogeneous mass.   The extrudable mixture of claim 1, wherein the ceramic material ranges from about 15% to about 30% by volume of the homogeneous mass.   The extrudable mixture of claim 1 wherein substantially all of the elongated fibers exhibit an aspect ratio greater than about 5 and less than about 200.   The extrudable mixture of claim 1, wherein substantially all of the elongated fibers exhibit an aspect ratio in the range of about 10 to about 1000.   The extrudable mixture of claim 1 wherein the ceramic material comprises a ceramic precursor. The extrudable mixture of claim 1, wherein the elongated fibers are ceramic fibers selected from the group identified in Table 1 of FIG. Fibers exhibiting an aspect ratio greater than 1,
Binder material,
An extrudable mixture that includes a fluid and the fibers, binder material and fluid are a homogeneous mass. 11. The extrudable mixture according to claim 10, wherein the fibers exhibit an aspect ratio distribution in a manner that is in the range of about 3 to about 1000. The extrudable mixture of claim 10 wherein the fibers exhibit a multi-modal distribution of aspect ratios in both embodiments in the range of from about 3 to about 1000. The extrudable mixture according to claim 10, wherein the fibers are ceramic fibers. The fiber is composed of organic fiber, polymer fiber, inorganic fiber, metal fiber, glass fiber, glass-ceramic fiber, oxide ceramic, non-oxide ceramic, amorphous, polycrystalline, metallic alloy 11. The extrudable mixture according to claim 10 which is substantially one selected fiber type. The fiber is composed of organic fiber, polymer fiber, inorganic fiber, metal fiber, glass fiber, glass-ceramic fiber, oxide ceramic, non-oxide ceramic, amorphous, polycrystalline, metallic alloy The extrudable mixture of claim 10 which is a mixture of selected fiber types. The extrudable mixture of claim 10 which coats the fibers. The extrudable mixture of claim 10 wherein the fibers are from about 15% to about 30% of the volume of the extrudable mixture. The extrudable mixture of claim 10 wherein the fibers are from about 8% to about 40% of the volume of the extrudable mixture. 11. An extrudable mixture according to claim 10 wherein the homogeneous mass exhibits a rheology set in the region bounded by points a, b, c and d in Table 5 of FIG. The extrudable mixture according to claim 10, wherein the fibers are metal fibers. 11. The extrudable mixture according to claim 10, wherein the fibers are ceramic fibers selected from the group identified in Table 1 of FIG. The extrudable mixture of claim 10 further comprising a pore-forming component and wherein the inorganic fibers, binder material, pore-forming component and fluid are in a homogeneous mass. 23. The extrudable mixture of claim 22 wherein the pore forming component is selected from the group identified in Table 3 of FIG. A homogeneous and extrudable mass comprising ceramic material, organic binder, and fluid;
An extrudable mixture wherein the ceramic material is less than about 40% of the mass volume. 25. The extrudable mixture of claim 24, wherein the ceramic material is less than about 20% of the mass volume. 25. The extrudable mixture according to claim 24, wherein the ceramic material is polycrystalline fibers, monocrystalline whiskers or amorphous fibers. Mixing elongated ceramic material fibers, binder material, and fluid into a homogeneous mass;
A method for producing a porous carrier, comprising extruding the homogeneous mass into a green carrier and curing the green carrier into a porous carrier. 28. The method of claim 27, wherein the mixing step comprises using less than about 40 volume percent ceramic-material fibers. 28. The method of claim 27, wherein the mixing step comprises using less than about 20% by volume ceramic-material fibers. 28. The method of claim 27, wherein the mixing step comprises using a shear mixer. 28. The method of claim 27, wherein the mixing step comprises mixing in the pore-forming component to form a homogeneous mass. 28. The method of claim 27, further comprising selecting a plurality of binders and selecting each binder exhibiting various temperatures that decompose thermally when compared to the other binder (s). 28. The method of claim 27, further comprising selecting a binder that provides sufficient raw material strength to prevent deformation of the green carrier prior to curing. 28. The method of claim 27, further comprising selecting the fibers such that substantially all of the fibers exhibit an aspect ratio greater than 5 by volume. 35. The method of claim 34, wherein the ceramic material comprises a fine or short material. 35. The method of claim 34, wherein the ceramic material is substantially free of fine or short materials. 28. The method of claim 27, wherein the curing step comprises forming bonds between intersecting fibers to form a porous support structure. 38. The method of claim 37, wherein substantially all intersecting fibers are bonded. 38. The method of claim 37, wherein some of the intersecting fibers are not bonded. Forming inorganic fibers, binder materials, and fluids into a homogeneous mass;
A method for producing a porous carrier comprising extruding a homogeneous mass into a green substrate carrier and curing the green substrate carrier into a porous carrier. 41. The method of claim 40, wherein the curing step comprises forming a bond between overlapping inorganic fibers to form a rigid structure of the porous support. 41. The method of claim 40, wherein the bond is a solid phase sinter bond, a liquid assisted sinter bond, or a glass, glass-ceramic or ceramic bond. 41. The method of claim 40, wherein the curing step comprises burning off substantially all of the fluid and organic material. 41. The method of claim 40, wherein the inorganic fibers formed bonds that create an open pore network. 41. The method of claim 40, wherein the extruding step further comprises extruding an extrudable mixture through the die. 41. The method of claim 40, wherein the extruding step further comprises extruding the extrudable mixture through a die using a piston or a screw extruder. 41. The method of claim 40, wherein the extrusion step is operated at room temperature or elevated temperature. Selecting a fiber material from Table 1 of FIG.
Selecting a binder from Table 2 of FIG.
Selecting a fluid from Table 4 in FIG.
Processing fiber materials,
Mixing the fiber material, binder, and fluid into a homogeneous mass;
Adjusting the rheology of the homogeneous mass to be extrudable,
A method for producing a porous carrier comprising extruding a homogeneous mass into a green substrate carrier and curing the green substrate carrier into a porous block. 49. The method of claim 48, wherein the processing stage is at least partially performed in the mixing stage, so that the mixing stage cuts long fibers into short fibers. 49. The method of claim 48, wherein the processing step further comprises coating the fiber with an organic material that assists in extrusion. 49. The method of claim 48, wherein the processing step comprises producing a slurry of the fiber material and fluid and vigorously aeration of the fiber material to cut long fibers into short fibers. 52. The method of claim 51, wherein the slurry further comprises a dispersion aid, an extrusion aid, or a strengthening aid. further,
Selecting an additive selected from the group consisting of pore-forming components, reinforcing agents, opacifiers, extrusion aids, dispersants, pH modifiers, inorganic binders, clays, erodible materials, and catalysts;
49. The method of claim 48, further comprising mixing the additive and the additive into a homogeneous mass. Removing the fluid from the green substrate,
Burning off organic materials,
Forming bonds between the fibers, and forming a fibrous open pore network in the carrier,
A step of curing the green substrate carrier into a porous block. 55. The curing process according to claim 54, wherein the bond is a solid phase sinter bond, a liquid assisted sinter bond, or a glass, glass-ceramic or ceramic bond. 55. A curing process according to claim 54, wherein the fibers rearrange into an intersecting network when the organic material is burned off. 55. The curing process of claim 54, further comprising using an inorganic additive material to form a portion of the fibrous open pore network. Forming a first extrudable mixture having a first mixture of fibers, additives, and fluids;
Forming a second extrudable mixture having a second mixture of fibers, additives, and fluid;
Arranging a first extrudable mixture adjacent to a second extrudable mixture in an extruder;
A method of producing a graded porous carrier comprising extruding a first and second extrudable mixture onto a green substrate carrier and curing the green substrate carrier. 59. The method of claim 58, wherein the curing step comprises forming bonds between intersecting fibers to form a porous support structure. At least some of the bonds are formed from one or more fibers obtained from one extrudable mixture that intersects one or more fibers in another extrudable mixture. 59. The method according to 59. 60. The method of claim 59, wherein the bond is a solid phase sinter bond, a liquid assisted sinter bond, or a glass, glass-ceramic or ceramic bond. The forming and arranging step further comprises forming the first extrudable mixture into a cylindrical shape and arranging the second extrudable mixture as a concentric layer around the cylinder. The method described. Forming and arranging steps further
Forming a first extrudable mixture into a first pellet;
Forming a second extrudable mixture into a second pellet;
Filling the tube with the first pellet;
59. The method of claim 58, comprising enclosing the tube with a second pellet and removing the tube. 64. The method of claim 63, further comprising excluding air from the pellets prior to extrusion. further,
Forming a first extrudate into a first set of discs;
59. The method of claim 58, comprising forming a second extrudate into a second set of disks and arranging the disks to form cylinders of alternative first and second disks. Putting bulk fiber into the liquid,
The process of producing fibers for use in an extruder comprising vigorously mixing fibers and liquid, chopping the fibers, and extracting most of the water from the mixture. 68. The process of claim 66, wherein the fiber is a ceramic fiber selected from the group listed in Table 1 of FIG. 68. The process of claim 66, further comprising adding a dispersant or binder to the liquid. 68. The process of claim 66, wherein the extracting step further comprises pressurizing the fibers and liquid against the filter media. 68. The process of claim 66, wherein the extracting step further comprises drying the fiber to remove most of the free liquid. Exhibit porosity in the range of about 60% to about 85%;
Having a structure formed from bonded ceramic fibers, and mixing the ceramic-material fibers with an additive and a fluid to form an extrudable mixture;
A porous ceramic support produced by an extrusion process comprising extruding an extrudable mixture into a green support and curing the green support into a porous support. 72. The porous ceramic carrier of claim 71, further comprising sintered, crystalline or glass bonds between the fibers. 72. A porous ceramic carrier according to claim 71, wherein the cured porous ceramic carrier consists essentially of ceramic fibers. 72. A porous ceramic carrier according to claim 71, wherein the cured porous ceramic carrier consists essentially of an open pore network of ceramic fibers. 72. The porous ceramic support of claim 71, wherein the cured porous ceramic support has a pore network such that substantially all of the pores are interconnected. A porosity that is in the range of about 60% to about 90% and having a structure formed from bound inorganic fibers,
Mixing inorganic fibers with additives and fluids to form an extrudable mixture;
A porous carrier that is produced by an extrusion process comprising extruding an extrudable mixture into a green substrate carrier and curing the green substrate carrier into a porous carrier. 77. The porous carrier of claim 76, wherein the curing step results in a fiber-to-fiber bond forming the structure. 77. The porous support of claim 76, wherein the bond is formed by sintering or by forming a glass, glass-ceramic or ceramic bond. The porous carrier of claim 6 wherein the curing step results in fiber-to-fiber bonds forming an open pore network. 77. The porous carrier of claim 76, wherein the inorganic fibers exhibit a distributed aspect ratio in a manner ranging from 3 to 1000. 77. The porous carrier according to claim 76, wherein the inorganic fibers are selected from Table 1 in FIG. 77. The porous carrier of claim 76, wherein the cured carrier has a detectable residue from burning off the additive. 77. The porous carrier of claim 76, wherein at least some of the fiber-to-fiber contact does not form a bond. 77. The porous carrier of claim 76, wherein substantially all fiber-to-fiber contact forms a bond. 77. The porous carrier of claim 76, further comprising a first carrier segment exhibiting a first porosity and a second carrier segment exhibiting a second porosity. 77. The porous carrier of claim 76, further comprising a first carrier segment exhibiting a first density and a second carrier segment exhibiting a second density. 77. The porosity of claim 76, further comprising a first carrier section that uses a first type of fiber-to-fiber bond and a second carrier section that uses a second type of fiber-to-fiber bond. Quality carrier. 77. A porous carrier according to claim 76, wherein the inorganic fibers comprise a crystalline, amorphous, glass or ceramic material. 77. The porous carrier according to claim 76, wherein the inorganic fiber is a metal fiber, a metal-alloy, or a ceramic fiber. 77. The porous carrier of claim 76, wherein the extrudable mixture further comprises organic fibers. A porous support exhibiting a porosity of about 40% to about 75% extruded from an extrudable mixture that does not contain any functionally effective pore-forming component. An extruded porous carrier basically composed of binding fibers. 94. A carrier according to claim 92, wherein the fibers consist essentially of ceramic fibers. 94. The support of claim 93, further comprising a solid phase, crystal, or glass bond between the ceramic fibers. 95. The support of claim 94, wherein the bonded ceramic fibers form an open pore network. 94. A porous support according to claim 93, wherein the ceramic fibers exhibit a distributed aspect ratio in a manner in the range of 3 to 1000. 94. The porous support of claim 93, wherein the ceramic fibers are selected from Table 1 of FIG. 94. The porous carrier of claim 92, further comprising parallel inlet and outlet paths in a honeycomb pattern. 94. The porous carrier of claim 92, further comprising parallel inlet and outlet paths, wherein the inlet path is larger than the outlet path. The porous carrier according to claim 92, wherein the porous carrier is a block having an arbitrary path. Extruded carrier having an open pore network formed by binding fibers;
A housing for holding the carrier,
A filter media product comprising an inlet for receiving a fluid and an outlet for supplying a filtered fluid. 102. The filter media product of claim 101, wherein the fluid is exhaust gas or liquid. 102. The filter media product according to claim 101, wherein the filter media product is an automobile air filter, an automobile exhaust filter, or an automobile cabin filter. 102. The filter media product of claim 101, further comprising a catalyst deposited on the extruded carrier. Extruded carrier having an open pore network formed by binding fibers;
Catalyst deposited on an extruded carrier,
A housing for holding the carrier,
A catalytic converter product comprising an inlet for receiving a fluid and an outlet for supplying a filtered fluid. 106. The catalytic converter product of claim 105, wherein the fluid is exhaust gas or liquid. 106. The catalytic converter product according to claim 105, wherein the filter medium product is an automobile air filter, an automobile exhaust filter, or an automobile cabin filter. 106. The catalytic converter product of claim 105 further comprising a catalyst deposited on the extruded carrier.

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