DE202006017355U1 - Porous substrate having high porosity useful for e.g. filter comprises structure formed of bonded ceramic fibers produced by mixing ceramic fiber with additives and fluid; extruding the mixture into green substrate followed by curing - Google Patents

Abstract

A porous ceramic substrate having porosity of 60 - 85% comprises structure formed of bonded ceramic fibers and is produced by an extrusion process involving mixing ceramic fibers with additives and a fluid to form an extrudable mixture; extruding the mixture into a green substrate; and curing the green substrate into the porous substrate. Independent claims are included for the following: (1) an extruded porous honeycomb substrate; (2) a filter product; and (3) a catalytic converter product.

Description

BACKGROUND

1. RELATED APPLICATIONS

These Application claims the benefit of US Provisional Patent Application Number 60 / 737,237, filed on 16 November 2005, entitled "Extrusion System porous Substrate "; U.S. Patent Application Number 11 / 323,430, filed December 30 2005, entitled "Extrudable Mixture to form a porous Blocks "of the US patent application Number 11 / 322,777, filed December 30, 2005, entitled "Method for extruding a porous one Substrate "; and United States Patent Application Number 11 / 323,429 filed December 30 2005, entitled "Extruded porous Substrate and articles using the same ", of which all are included herein in their entirety.

2nd AREA

The The present invention relates to a porous ceramic honeycomb substrate.

3. DESCRIPTION OF THE STAND OF THE TECHNIQUE

Lots Processes require solid substrates to facilitate and support different ones Operations. To the For example, substrates used in filtering applications are suspended solids to filter, separate different substances or bacteria or remove germs from the air. These substrates can be so Be constructed in air, exhaust gases or liquids act, and can be prepared so that they have significant environmental or chemical Withstand loads. In another example, to the relief chemical reactions catalytic materials on the substrates applied. For example, a precious metal may be applied to a suitable one Substrate are applied, and the substrate can then act, that it is harmful Exhaust gases in less harmful Catalytically converts gases. Typically, these fixed Substrates more effective with a higher Porosity.

The porosity is generally defined as the property of a solid material, the percentage of the total volume of this material determines which of an open space is occupied. For example has a substrate with 50% porosity half the volume of the substrate occupied by open spaces becomes. In this way, a substrate with a higher porosity has less Mass per volume as a substrate with a lower porosity. Some Applications benefit from a lower mass substrate. For example, when a substrate is used to produce a catalytic Support process and the catalytic process operates at an elevated temperature, heats up a substrate with a lower thermal mass faster to its operating temperature. This way, the time is up for to warm its operating temperature Catalyst, i. the kicking time, using a more porous and less thermally massive substrate reduced.

Permeability is also an important property for substrates, especially filter and catalytic substrates. The permeability is related to porosity in that the permeability is a measure of how easily a fluid, such as a liquid or gas, can flow through the substrate. Most applications take advantage of a high permeability substrate. For example, an internal combustion engine works more efficiently when the aftertreatment filter provides a lower back pressure for the engine. Low back pressure is created by using a higher permeability substrate. Since permeability is more difficult to measure than porosity, porosity is often used as a substitute guide to the permeability of a substrate. However, this is not a particularly accurate characterization because a substrate may be quite porous but may still have limited permeability if the pores are not generally open and interconnected. For example, a Styrofoam cup is formed from a highly porous foam material, but is not permeable to the liquid flow. Therefore, considering the importance of porosity and permeability, the pore structure of the substrate must also be tested. In the example of styrofoam cup, the polystyrene material has a closed pore network. That is, the foam contains many unbonded and / or closed pores. In this way, there are many gaps and open spaces in the foam, but since the pores are not connected, no fluid or gas can flow from one side of the foam to the other. As more of the channels begin to connect, the fluid paths begin to form from one side to the other. In such a case, it is said that the material has several open pore networks. The more connected Channels are formed through the material, the higher the permeability for the substance. In the case where each pore is connected to at least one other channel and all pores allow fluid flow through the entire thickness of the wall formed from the material, the substrate would be defined as a completely open pore network. It is important to keep in mind the difference between cells and pores. Cells are the channels that pass (generally but not necessarily parallel to one another) through the honeycomb substrate. Often honeycomb substrates are mentioned in connection with how many cells per square inch they have. For example, a substrate has 200 cells per square inch 200 Channels along the major axis of the substrate. On the other hand, as pores, the gaps are referred to in the material itself, as in the material forming the wall separating two parallel channels or cells. Fully or mostly open pore network substrates are not known in the filter or catalyst industries. Instead, even most porous extruded substrates available are a mixed form of open and closed pore porosity.

Accordingly is it for many applications very desirable, that substrates with high porosity and be formed with an inner pore structure that is equally high permeability allows. As well have to the substrates are formed with a sufficiently strong structure, to meet the structural and environmental needs of particular Applications. For example, a filter or Catalyst to be attached to an internal combustion engine to be able of possible environmental Vibration, the thermal requirements and the manufacturing and use stresses withstand. After all the substrate must be able to be manufactured at a cost, the low enough to allow full use. For example, to get to the level of global pollutant emissions of motor vehicles, a filter substrate both in developed as also developing countries affordable and usable. Accordingly, the entire Cost structure for Filter and catalyst substrates an essential consideration in the substrate design and the selected method.

The Extrusion has proven to be an efficient and cost effective Process for the preparation of solid substrates with constant cross-section proved. In particular, the extrusion of ceramic powder material the most widely used method for the production of filter and catalytic substrates for Internal combustion engines. Over time, the process is to extrude of ceramic powder advanced so that now substrates with porosities from approximate 60% can be extruded. These extruded porous Substrates have good strength properties, can be flexible can be made be mass produced, maintain high quality levels, and are very inexpensive. However, the extrusion of ceramic powder material has a practical one Upper limit of porosity achieved, and further increases the porosity seem to lead to unacceptably low strength. To the For example, when the porosity is increased above 60%, the extruded ceramic powder substrate has become as not strong enough to work in the harsh environment of a diesel particulate filter to work. In another limitation of the known extrusion methods was it desirable the surface area in a substrate to enlarge to enable a more efficient catalytic conversion. To the surface area to enlarge attempts the cell density of the extruded ceramic powder substrates to increase, however, led the increase the cell density to an unacceptable back pressure for the engine. Therefore, the extruded ceramic powder substrates have very high porosities insufficient strength and also produce an unacceptable Back pressure, if an increased surface area needed becomes. Accordingly, the extrusion of ceramic powder seems their to have reached practical limits of use.

In the desire to be higher porosities To achieve, filter suppliers have tried on folded ceramic papers convert. Using such folded ceramic papers are porosities of about 80% possible with very low dynamic pressure. With such a small one Back pressure these filters were used in applications such as mining, where a very small Back pressure is a necessity. However, the use of the Folded ceramic paper filter sporadically and did not get very strong accepted. For example, folded ceramic papers became rough Environments are not used effectively. The production of the folded Ceramic papers requires the use of a papermaking process, which produces ceramic paper structures that are relatively weak and not cost-effective compared to extruded filters seem to be. Furthermore allows the formation of folded ceramic papers has very little flexibility in the Cell shape and cell density. For example, it is difficult to do a folded one Paper filter with big inlet channels and smaller outlet channels which are desirable in some filter applications can. Accordingly, the use of folded ceramic papers the requirements for Filter and catalytic substrates with higher porosity not Fulfills.

In another example of the endeavor to increase the porosity and the disadvantages of folded To avoid paper, substrates have been formed by forming a mass with ceramic precursors and thoroughly processing the mass into growing monocrystalline whiskers in a porous pattern. However, growing these crystals in place requires careful and accurate control of the curing process, making the process for mass production difficult, relatively expensive and prone to failure. Furthermore, this difficult process only provides a little more percentage points in porosity. Finally, the process develops only a mullite-like crystalline whisker which limits the applicability of the substrate. For example, a mullite is known to have a large coefficient of thermal expansion, making crystalline mullite whiskers undesirable in many applications requiring a wide temperature range and accurate temperature transitions.

Accordingly The industry has a need for a solid substrate that has a high porosity and has a correspondingly high permeability. This would be preferred Substrate as a very desirable open cell network would be shaped economical be in the making and could with flexible physical, chemical and reaction properties getting produced.

SUMMARY

Short summarized, the present invention provides an extrudable Mixture for producing a highly porous substrate using an extrusion process. In particular, the present invention enables Fibers, such as organic, inorganic, glass, ceramic or metal fibers, into a mass that, when extruded and cured, a highly porous Substrate forms. In dependence of allows the special mixture the present invention substrate porosities from about 60% to about 90% and allows also process advantages with other porosities. The extrudable mixture can use a wide variety of fibers and additives and is connected to a wide variety of operating environments and applications customizable. Fibers having a shape factor greater than 1 are selected according to the substrate requirements and be with binders, pore formers, extrusion aids and Fluid mixed to form a homogeneous extrudable mass. The homogeneous mass is extruded to a greenbody substrate. The more volatile Material is preferably removed from the green body substrate, which allows that the fibers connect and contact each other. During the Curing process continues, Fiber-to-fiber bonds are formed to form a structure with one to create a substantially open pore network. The resulting porous Substrate is useful in many applications, for example as a Substrate for a filter or catalyst housing or a catalyst.

In A more specific example is ceramic fibers with a shape factor between about 3 and about 1000, although more typically in the range of about 3 to about 500 selected. The form factor is the ratio of Length of Fiber divided by the diameter of the fiber. The ceramic fibers become homogeneous with binder, pore former and a fluid Mass mixed. A shear mixing process is applied to the fiber evenly in the Mass more complete to distribute. The ceramic material may be about 8 to about 40 volume percent be the mass, resulting in a substrate that is between about 92% and about 60% porosity Has. The homogeneous mass is extruded to a greenbody substrate. The Binder material is removed from the green body substrate, which allows the fibers to overlap or to contact. While the curing process continues, fiber-to-fiber bonds are formed to form a solid to create an open cell network. As used in this description, is "curing" defined in such a way that it comprises two main process steps: 1) Binder removal and 2) bond formation. The binder removal process is removed free water, removes most of it the additive and allows the fiber-to-fiber contact. The resulting porous substrate is useful in many applications for example as a substrate for a filter or catalyst.

In Another specific example may be a porous substrate without use be generated by pore formers. In this case, the ceramic material from about 40 to about 60 or more percent by volume of the mass, from which resulting in a substrate having between about 60% and about 40% porosity. There no pore former is used, the extrusion process is simplified and cheaper. Likewise, the resulting structure is a very desirable, essentially open pore network.

Advantageously, the disclosed fiber extrusion system produces a substrate which has a high porosity and has both an open pore network which allows a correspondingly high permeability and a sufficient strength according to the application requirements. The fiber extrusion system also produces a substrate with sufficient cost efficiency to allow full utilization of the resulting filters and catalysts. The extrusion system is readily applicable for mass production and allows flexible chemical compositions and constructions to handle a variety of applications support applications. The present invention represents a pioneering use of fibrous material in an extrudable blend. This fibrous extrudable blend enables the extrusion of very high porosity substrates in a mass production and cost effective manner. By enabling the use of fibers in the reproducible and robust extrusion process, the present invention enables the mass production of filter and catalytic substrates for wide use throughout the world.

These and other features of the present invention are from a reading The following description can be seen and understood by the means and combinations be realized, which are particularly indicated in the appended claims.

SHORT DESCRIPTION THE DRAWINGS

The Drawings form part of this description and are included exemplary embodiments of the invention, which are carried out in various forms can. It is understood that in some cases different aspects of Invention exaggerated or shown enlarged could be, for an understanding to facilitate the invention.

1 Fig. 10 is a block diagram of a system for extruding a porous substrate according to the present invention.

2 Figure 11 is an illustration of a fibrous extrudable blend according to the present invention.

3A and 3B FIG. 10 is an illustration of an open pore network according to the present invention. FIG.

4 FIG. 4 is an electron micrograph of an open pore network according to the present invention and a closed pore network of the prior art. FIG.

5 Fig. 10 is an illustration of a filter block using a porous substrate according to the present invention.

6 are tables of fibers, binders, pore formers, fluids and rheologies useful in the present invention.

7 Fig. 10 is a block diagram of a system for extruding a porous substrate according to the present invention.

8th Fig. 10 is a block diagram of a system for curing a porous substrate according to the present invention.

9 Figure 10 is a block diagram of a system for processing fibers for a porous substrate according to the present invention.

10 Figure 4 is a schematic for extruding a porous gradient substrate according to the present invention.

11 Figure 4 is a schematic for extruding a porous gradient substrate according to the present invention.

12 Figure 4 is a schematic for extruding a porous gradient substrate according to the present invention.

DETAILED DESCRIPTION

Detailed descriptions of examples of the invention are provided herein. It is understood, however, that the present invention can be illustrated in various forms. Therefore, the specific details disclosed herein are not to be interpreted as limiting, but rather as a representative basis for teaching a person skilled in the art, such as the present invention in almost any incoming system, structure or method.

Regarding 1 Now, a system for extruding a porous substrate will be explained. In general, a system uses 10 an extrusion process to extrude a greenbody substrate that can be cured to the highly porous final substrate product. The system 10 advantageously produces a substrate with high porosity, which has both a substantially open pore network, which allows a correspondingly high permeability, as well as a sufficient strength according to the application requirements. The system 10 also produces a substrate with sufficient cost efficiency to allow full utilization of the resulting filters and catalysts. The system 10 is readily applicable to mass production and allows flexible chemical compositions and designs to support a variety of applications.

The system 10 enables a highly flexible extrusion process, so that it is able to cover a wide range of specific applications. When using the system 10 First, the substrate designer determines the requirements for the substrate. These requirements may include, for example, size limitations, fluid permeability, desired porosity, pore size, mechanical strength and impact properties, heat resistance, and chemical reactivity. According to these and other requirements, the designer selects materials for use in forming an extrudable blend. Significantly, the system allows 10 the use of fibers 12 in the formation of an extruded substrate. These fibers may be, for example, ceramic fibers, organic fibers, inorganic fibers, polymer fibers, oxide fibers, glassy fibers, glass fibers, amorphous fibers, crystalline fibers, non-oxide fibers, carbide fibers, metal fibers, other inorganic fiber structures, or a combination thereof. However, for ease of explanation, the use of ceramic fibers will be described, although it will be understood that other fibers may be used. Also, the substrate is often described as a filter substrate or a catalytic substrate, although other uses are considered and within the scope of this teaching. The designer selects the particular type of fiber based on the application-specific requirements. For example, the ceramic fiber may be selected as a mullite fiber, an aluminum silicate fiber, or other generally available ceramic fiber material. The fibers must be added 14 usually machined by cutting the fibers to a useful length, which may include a cutting operation prior to blending the fibers with additives. Likewise, the various mixing and shaping steps in the extrusion process further cut the fibers.

According to the special requirements are additives 16 added. These additives 16 may include binders, dispersants, pore formers, plasticizers, processing aids, and reinforcing materials. Likewise, a fluid 18 , which is usually water, with the additives 16 and the fibers 12 combined. The fibers, the additives and the fluid become an extrudable rheology 21 mixed. This mixing may include dry mixing, wet mixing and shear mixing. The fibers, additives and fluid are mixed until a homogeneous mass is produced, which evenly distributes and arranges the fibers throughout the mass. The fibrous and homogeneous mass is then extruded to form a greenbody substrate 23 to build. The green body substrate has sufficient strength to hold together up to the remaining processes.

The greenbody substrate is then added 25 hardened. As used in this specification, "cure" is defined to include two major process steps: 1) binder removal and 2) bond formation The binder removal process removes free water, removes most of the additives, and allows fiber-to-fiber contact Frequently, the binder is removed using a heating process that burns off the binder, however, it will be understood that other removal operations may be used depending on the particular binder used. For example, some binders may be removed using an evaporative or sublimation process. Some binders and / or other organic components may be melted prior to degradation into a vapor phase As the curing process continues, fiber-to-fiber bonds are formed These bonds promote overall structural strength and also produce the desired porosity and the like nd permeability to the substrate. Accordingly, the cured substrate 30 a highly porous substrate made up mostly of fibers that form an open pore network 30 are bound. The substrate can then be used as a substrate for many applications, including as a substrate for filter applications and catalyst applications. Advantageously, the system has 10 allows a desirable extrusion process to produce substrates with porosities of up to about 90%.

Regarding 2 now becomes an extrudable material 50 explained. The extrudable material 50 is ready for extrusion from an extruder such as a piston or screw extruder. The extrudable mixture 52 is a homogeneous mass containing fibers, plasticizers and other additives as required by the specific application. 2 represents an enlarged section 54 It is understood that the enlarged section 54 can not be drawn to scale, but is provided as an aid to this description. The extrudable mixture 52 contains fibers, such as fibers 56 . 57 and 58 , These fibers were selected to produce a highly porous and solid final substrate with desired thermal, chemical, mechanical and filtration properties. As will be understood, essentially fibrous bodies have not been considered extrudable because they have no inherent plasticity. However, it has been found that by accurate selection of plasticizers and by process control, an extrudable mixture 52 can be extruded from fibers. In this way, the cost, mass production and flexibility benefits of extrusion can be extended by including the benefits that are available from the use of fibrous material.

In general, a fiber is considered to be a material having a relatively small diameter and a shape factor greater than one. The form factor is the ratio of the length of the fiber divided by the diameter of the fiber. For simplicity, as used herein, the "diameter" of the fiber is assumed to be a circular cross-sectional shape of the fiber, and this simplified assumption is applied to fibers regardless of their actual cross-sectional shape, for example, a fiber having a shape factor of 10 The diameter of the fiber may be 6 microns, although the diameters are readily available in the range of about 1 micron to about 25 microns, it being understood that fibers of many other diameters and form factors in the system 10 can be successfully used. As described in more detail with respect to later figures, there are several alternatives for selecting form factors for the fibers. It should also be understood that the shape of the fibers is in sharp contrast to the conventional ceramic powder where the shape factor of each ceramic particle is approximately one.

The fibers for the extrudable mixture 52 may be metallic (sometimes referred to as thin-diameter metallic wires), though 2 in relation to ceramic fibers. The ceramic fibers may be in an amorphous state, a glassy state, a crystalline state, a polycrystalline state, a monocrystalline state, or a glass-ceramic state. When forming the extrudable mixture 52 For example, a relatively small volume of ceramic fiber is used to create the porous substrate. For example, the extrudable mixture 52 have only about 10 to 40 volume percent ceramic fiber material. In this way, after curing, the resulting porous substrate has a porosity of about 90% to about 60%. It is understood that other amounts of ceramic fiber material can be selected to produce other porosity values.

To produce an extrudable mixture, the fibers are usually combined with a plasticizer. In this way, the fibers are combined with other selected organic or inorganic additives. These additives constitute three major characteristics for the extrudate. First, the additives allow the extrudable mixture to have a rheology suitable for extrusion. Second, the additives impart sufficient strength to the extruded substrate, commonly referred to as a green body substrate, to hold its shape and position the fibers until these additives are removed during the curing process. Third, finally, the additives are selected to burn in the curing process in a manner that facilitates the placement of the fibers in an overlapping construction and does not weaken the formation of a solid structure. Usually, the additives contain a binder, such as the binder 61 , The binder 61 acts as an aid to hold the fibers in place and provide strength to the green body substrate. The fibers and binders can be used to produce a porous substrate having a relatively high porosity. However, in order to further increase the porosity evenly, additional pore formers, such as the pore former, may be used 63 , to be added. The pore formers are added to increase the open space in the cured final substrate. The pore formers may be spherical, oblong, fibrous or irregular in shape. The pore formers are selected not only for their ability to create an open space and based on their thermal degradation behavior, but also for assisting in aligning the fibers. In this way, the pore formers assist in arranging the fibers into an overlapping pattern to facilitate proper bonding between the fibers during a later stage of curing. In addition, pore formers also play a role in aligning the fibers in preferred directions, which affects the thermal expansion of the extruded material and the strength along various axes.

As briefly described above, the extrudable mixture 52 use one or more fibers those selected from many types of available fibers. Further, the selected fiber may be combined with one or more binders selected from a wide variety of binders. Also, one or more pore formers selected from a variety of pore formers may be added. The extrudable mixture may use water or other fluid as its softening agent and may have added other additives. This flexibility in the formation of the chemical composition allows the extrudable mixture 52 advantageously can be used in many different types of applications. For example, mixture combinations may be selected according to the required environmental, temperature, chemical, physical and other requirements. Furthermore, since the extrudable mixture 52 is prepared for extrusion, the extruded end product is formed flexibly and economically. Although in 2 not shown, the extrudable mixture 52 extruded by means of a screw or piston extruder to form a greenbody substrate, which is then cured to the final porous substrate product.

The The present invention represents a pioneering use of fibrous material in a plastic block or mixture for extrusion. This fibrous extrudable mixture allows the extrusion of substrates with very high porosities in a mass production and in a cost effective manner. By enabling the use of the fibers in the reproducible and robust Extrusion process allows the present invention mass production of filter and catalytic Substrates for wide use throughout the world.

Regarding 3A an enlarged hardened area of a porous substrate is shown. The substrate section 100 is after binder removal 102 and after the curing process 110 shown. After binder removal 102 become the fibers, like the fiber 103 and 104 , initially held in position with binder material, and as the binder material burns, the fibers are exposed to be in an overlapping but loose structure. Likewise, a pore builder 105 be positioned to both create an open space and to align or arrange the fibers. Since the fibers have only a relatively small volume of the extrudable mixture, many open spaces exist 107 between the fibers. When the binder and pore former are burned off, the fibers can easily shift to further contact each other. The binder and pore formers are selected to burn off in a controlled manner such that they do not disrupt the placement of the fibers or cause the substrate to collapse upon burning. Usually, the binder and pore formers are selected such that they degrade or burn off prior to forming bonds between the fibers. As the curing process continues, the overlapping and contacting fibers begin to form bonds. It is understood that the bonds can be formed in a variety of ways. For example, the fibers may be heated to allow the formation of a liquid assisted sintered bond at the intersection or node of the fibers. This liquid state sintering may result from the particular fibers selected or from additional additives added to the mixture or coated on the fibers. In other cases, it may be desirable to form a sintered bond in the solid state. In this case, the intersecting bonds form a grain structure connecting the overlapping fibers. In the raw state, the fibers have not yet formed physical bonds with each other, but may still have some degree of green body strength due to the entanglement of the fibers together. The particular type of bond selected depends on the choice of starting materials, the desired strength, and the chemical compositions and environments that are effective. In some cases, the bonds are caused by the presence of inorganic binders, which are the mixture that holds the fibers together in a composite net, and which do not burn off during the curing process.

Advantageously, it facilitates the formation of bonds, such as the bonds 112 , forming a substantially solid structure with the fibers. The bonds also allow the formation of an open pore network with very high porosity. For example, it becomes an open space 116 naturally generated by the space between the fibers. An open space 114 is generated when the pore builder 105 falls down or burns down. In this way, the process of forming the fiber bond creates an open pore network with no or nearly no limited channels. This open pore network produces high permeability and high filtration efficiency and allows a large surface area, for example, to add a catalyst. It will be understood that the formation of bonds may depend on the type of bonding desired, such as solid state sintering or liquid supported / liquid state, and additives that are present during the curing process. For example, the additives, the particular fiber selection, the time of heating, the level of heat, and the reaction environment may all be adjusted to produce a particular type of bonding.

Regarding 3B Now, an enlarged cured portion of a porous substrate will be explained. The substrate section 120 is after binder removal 122 and after the curing process 124 shown. The substrate section 120 is similar to the substrate section 100 who's referring to 3A is described so that is not described in detail. The substrate 120 was formed without the use of special pore formers, so that the entire open pore network 124 resulting from the positioning of the fibers with a binder material. In this way, substrates of reasonably high porosity can be formed without the use of any particular pore-forming agents, thereby reducing the cost and complexity of producing such substrates with adequate porosity. It has been found that substrates having a porosity ranging from about 40% to about 60% can be produced in this manner.

Regarding 4 now becomes an electron microscope picture set 150 explained. The image set 150 first make an open pore network 152 which is produced as desired using a fibrous extrudable mixture. As can be seen, the fibers formed bonds with intersecting fiber nodes and pore formers and binders were burned leaving a porous open pore network. In stark contrast, the picture represents 154 a typical closed cell network made using known methods. The partially closed pore network has a relatively high porosity, but at least part of the porosity is from closed channels. These closed channels do not contribute to permeability. In this way, from an open pore network and a closed pore network with the same porosity, the open pore network has a more desirable permeability characteristic.

The extrudable mixture and process, which are generally so described, are used to produce a very beneficial and porous substrate. In one example, the porous substrate may become a filter block substrate 175 be extruded, as in 5 is shown. The substrate block 175 was extruded using a piston or screw extruder. The extruder could be conditioned to operate at room temperature, a little elevated temperature or in a controlled temperature window. In addition, various parts of the extruder could be heated to different temperatures to affect the deceleration properties, shear history, and gelation properties. In addition, the size of the extrusion dies may also be sized to control the expected shrinkage in the substrate during the heating and sintering process. Advantageously, the extrudable mixture was a fibrous extrudable mixture with sufficient plasticizer and other additives to allow the extrusion of fibrous material. The extruded ingot in the raw state was cured to remove the free water, burn off additives and form structural bonds between the fibers. The resulting block 175 has both very desirable porosity properties as well as excellent permeability and a very useful surface area. Likewise, the block 175 depending on the particular fibers and additives selected for advantageous depth filtering. The block 176 has channels 179 which extend longitudinally through the block. The inlets to the block 178 may be left open for a flow-through operation, or any other opening may become clogged to create a wall-flow effect. Although the block 175 With hexagonal channels shown, it should be understood that other patterns and sizes can be used. For example, the channels may have a uniformly sized square, rectangular or triangular channel pattern; a square / rectangular or octagonal / square channel pattern with larger inlet channels; or be provided with a different symmetrical or asymmetrical channel pattern. The exact shapes and sizes of the channels or cells can be tuned by adjusting the design of the mold. For example, a square channel may be configured to have curved corners using EDM (spark erosion) to form the posts in the die. Such rounded corners are expected to increase the strength of the final product despite a somewhat higher back pressure. In addition, the die design can be modified to extrude honeycomb substrates where the walls have different thicknesses and the outer skin has a different thickness than the rest of the walls. Similarly, in some applications, an outer skin may be applied to the extruded substrate for final determination of size, shape, contour, and strength.

When used as a flow-through device allows the high porosity of the block 176 a large surface area for the application of the catalytic material. In this way, a very effective and efficient catalyst with a low thermal mass can be produced. With such a low thermal mass, the resulting catalyst has good light-off properties and efficiently utilizes the catalytic material. When used in an example of wall flow or wall filtration, the high permeability of the substrate walls allows relatively low back pressures where in the depth filtering is facilitated. This depth filtering allows for efficient partial removal and more effectively facilitates regeneration. In shaping the wall flow, the fluid flowing through the substrate is forced to move through the walls of the substrate, allowing more direct contact with the fibers forming the wall. These fibers provide a large surface area for any reactions that take place as if a catalyst were present. Because the extrudable mixture can be formed from a wide variety of fibers, additives and fluids, the chemical composition of the extrudable mixture can be adjusted to produce a block having specific properties. For example, if the final block is desired as a diesel particulate filter, the fibers are selected to contribute to safe operation even at the extreme temperature of uncontrolled regeneration. In another example, if the block is to be used to filter a particular type of exhaust, the fiber and bonds are selected such that they do not react with the exhaust in the expected operating temperature range. Although the advantages of the high porosity substrate with respect to filters and catalysts have been described, it should be understood that there are many other applications for the highly porous substrate.

The fibrous extrudable mixture as described with reference to 2 can be formed from a wide variety of starting materials. The selection of suitable materials is generally based on the chemical, mechanical and environmental conditions under which the final substrate must operate. Accordingly, a first step in designing a porous substrate is to understand the ultimate application for the substrate. Based on these requirements, special fibers, binders, pore formers, fluids and other materials can be selected. It will be appreciated that the method used with the selected materials may affect the final substrate product. Since the fiber is the major structural material in the final substrate product, the choice of fiber material is critical to the final substrate being able to operate in its intended application. Accordingly, the fibers are selected according to the required bonding requirements, and a particular type of bonding process is selected. The bonding process may be liquid state sintering, solid state sintering or a compound which requires a binder such as a glass former, glass, layer silicates, ceramics, ceramic precursors or colloidal solutions. The binder may be part of one of the fiber constructions, a coating on the fiber, or a component in one of the additives. It is also understood that more than one type of fiber can be selected. It is also understood that some fibers may be consumed during the curing and bonding process. When selecting the fiber composition, the final operating temperature is an important consideration, so that the heat resistance of the fiber can be maintained. In another example, the fiber is selected such that it remains chemically inactive and unreactive in the presence of expected gases, liquids or solid suspended matter. The fiber may also be selected at its expense, and some fibers may pose health concerns due to their small dimensions, so their use can be avoided. Depending on the mechanical environment, the fibers are selected for their ability to both form a strong solid structure and to maintain the required mechanical integrity. It will be understood that the selection of a suitable fiber or set of fibers can compromise design and application. 6 Table 1 shows various types of fibers that can be used to form a fibrous extrudable mixture. In general, the fibers may be oxide or non-oxide ceramic, glass, organic, inorganic, or metallic. For ceramic materials, the fibers may be in various states, such as amorphous, glassy, polycrystalline or monocrystalline. Although Table 1 lists many available fibers, it will be understood that other types of fibers can be used.

The binders and pore formers can then be selected according to the type of fibers selected as well as other desired properties. In one example, the binder is selected to facilitate a particular type of bonding in the liquid state between the selected fibers. In particular, the binder has a component which reacts at a bonding temperature such that it facilitates the flow of a liquid compound to the junctions of the intersecting fibers. Also, the binder is selected for its ability to both soften the selected fiber and maintain its strength in the raw state. In one example, the binder is also selected for the type of extrusion used and the temperature required for extrusion. For example, some binders form a gelatinous mass when heated too much and therefore can only be used in low temperature extrusion processes. In another example, the binder may be selected for its impact or shear mixing properties. In this way, the binder can facilitate cutting the fibers of the desired shape factor during the blending operation. The binder can also be selected according to its degradation or burning properties. The binder must be able to hold the fibers generally in place and the forming fiber structure during burning not to interrupt. For example, if the binder burns off too quickly or violently, the exiting gases may disrupt the forming structure. Likewise, the binder can be selected according to the amount of the remainder of the binder left after burning. Some applications may be highly sensitive to such residues.

pore formers can for the Formation of relatively adequate porosities are not needed. To the Example can The natural Arrangement and densification of the fibers within the binder interact to create a porosity from about 40% to about 60%. In this way, a substrate with adequate porosity under Use of an extrusion process without the use of pore formers be generated. In some cases allows the removal of pore forming a porous substrate, in comparison to produce known processes more economical. however can, if a porosity required by more than about 60%, pore formers are used for an additional To cause air space within the substrate after curing. The pore formers can also be selected according to their degradation or burning properties, and can also according to their size and shape selected become. The pore size can For example, for separating special types of suspended matter or Enable important for a particularly high permeability. The shape of the Pores can also be adjusted, for example, the exact alignment to support the fibers. For example, a relatively elongated Pore form the fibers to a more aligned pattern, while a more irregular or spherical Shape the fibers can arrange to a more arbitrary pattern.

The Fiber may be provided by a manufacturer as a tailored fiber and can be used directly in the process, or a fiber can be provided in a mass format, which is usually is processed before use. In one way or another should consider procedural issues, such as the fiber to their final desired Form factor distribution is to be processed. In general, the Fiber first sliced before mixing with other additives, and will then while the mixing, shearing and extrusion steps further cut. however the extrusion can also be carried out with uncut fibers, by setting the rheology to be the extrusion mixture with reasonable extrusion pressures makes extrudable, and without dilatant flows in the extrusion mixture caused when it attaches to the extrusion press molding surface Pressure is placed. It goes without saying that the cutting of Fibers to an appropriate form factor distribution at different Jobs in the entire process can be performed: as soon as the Fiber selected and to a usable length it is cut with the binder and the pore former mixed. This mixing may initially be in a dry form carried out to initiate the mixing process, or may be used as a wet mixing operation carried out become. The fluid, which is usually Water is added to the mixture. To the required level to achieve the homogeneous distribution, the mixture is over or several stages sheared. The shear mixing or dispersion mixing creates both a very desirable homogeneous mixing process for a uniform distribution of Fibers in the mixture as well as a further cutting of fibers to the desired Form factor.

6 Table 2 shows various binders available for selection. It is understood that a single binder may be used, or multiple binders may be used. The binders are generally classified into organic and inorganic classifications. The organic binders generally burn off at a low temperature during curing, while the inorganic binders usually form part of the final structure at a higher temperature. Although various binder choices are listed in Table 2, it should be understood that various other binders can be used. 6 Table 3 shows a list of available pore formers. Pore formers can generally be defined as organic or inorganic, with the organic usually burning at a lower temperature than the inorganic ones. Although various pore formers are listed in Table 3, it will be understood that other pore formers can be used. 6 Table 4 shows various fluids that can be used. Although it is understood that water may be the most economical and most commonly used fluid, some applications may require different fluids. Although Table 4 shows various fluids that may be used, it will be understood that other fluids may be selected according to specific application and process requirements.

In general, the mixture can be adjusted to have a rheology suitable for advantageous extrusion. Usually, proper rheology results from the proper selection and mixing of fibers, binders, dispersants, plasticizers, pore formers, and fluids. A high level of mixing is needed to give the fibers adequate plasticity. Once the right fiber, the right binder and the right pore former have been selected, the amount of fluid will become usually finalized to achieve the right rheology. Proper rheology can be indicated, such as by one of two trials. The first attempt is a subjective, informal attempt where a drop of the mixture is removed and molded between the fingers of an experienced extrusion operator. The operator is able to detect when the mixture is properly sliding between the fingers, indicating that the mixture is in a proper state for extrusion. A second more objective approach is based on the measurement of physical properties of the mixture. In general, shear strength can be measured versus compaction pressure using a limited (ie high pressure) annular rheometer. The measurements are taken and recorded according to a comparison of the cohesive strength with the pressure dependence. By measuring the mixture at various mixtures and fluid levels, a rheology diagram indicating the rheology points can be formed. For example, Table 5 presents 6 a rheology diagram for a fibrous ceramic mixture. The axis 232 represents the cohesive strength, and the axis 234 represents the pressure dependence. The extrudable area 236 represents an area where fibrous extrusion is most likely to occur. Therefore, a mixture that is characterized by any measurement that falls within the range 236 falls, probably successfully extruded. Of course, it is understood that the rheology diagram is subject to many variations, and so there is some variation in the positioning of the region 236 expected. In addition, there are several other direct and indirect attempts to measure rheology and plasticity, and it will be understood that any number of these can be used to test whether the mixture has the right rheology to match the final shape of the desired one Product can be extruded.

As soon as the correct rheology has been achieved, the mixture is an extruder extruded. 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 be a require human intervention. The mixture is determined by means of a Extruded die having the desired cross-sectional shape for the substrate block Has. The die was selected to be the greenbody substrate sufficiently formed. In this way, a stable green body substrate generated by the curing process is being treated while his Shape and fiber orientation is maintained.

The Green substrate is then dried and cured. Drying may take place under ambient conditions, at controlled temperature and humidity conditions (as in controlled ovens), in microwave ovens, in HF ovens and convection ovens occur. The curing generally requires the removal of free water to the Green substrate to dry. It is important to control the green body substrate in a controlled manner Way too dry, that no cracks or other structural Errors are introduced. The temperature can then be increased to burn off additives, such as binders and pore formers. The Temperature is controlled to ensure that the additives be burned in a controlled manner. It goes without saying that the burning off of the additives is a passage of temperatures over different Time cycles and different heat levels may require. Once the additives have burned off, the substrate becomes heated to the required temperature to structural bonds at the fiber crossing points or nodes. The required Temperature is determined by the type of bond required and the chemical composition of the fibers selected. For example, liquid-backed sintered Bindings usually formed at a temperature lower than bonds in the solid State is. It is understood that the size of the time at the bonding temperature regulated according to the specific nature of the bond to be generated can be. The entire heat cycle can in the same oven, in different ovens, in discontinuous or continuous processes and under conditions of air or controlled atmosphere carried out become. After the fiber bonds have been formed, the substrate becomes slowly cooled to room temperature. It is understood that the curing process in one oven or several ovens / cookers carried out can be and in production ovens / herds, like tunnel ovens, can be automated.

Regarding 7 Now, a system for extruding a porous substrate will be explained. The system 250 is a highly flexible process for producing a porous substrate. To shape the substrate, the substrate requirements are defined as in block 252 is shown. For example, the ultimate use of the substrate generally defines the substrate requirements, which may include size limitations, temperature limitations, strength limitations, and chemical reaction limitations. Furthermore, the cost and manufacturability of the substrate in bulk may dictate and drive certain selections. For example, a high production rate may result in the production of relatively high temperatures in the extrusion die, and therefore, binders that operate at an elevated temperature without curing or gelling are selected. For extrusions using high temperature binders, the dies and cylinder must be maintained at a relatively high temperature, such as 60 to 180 ° C, can be maintained. In such a case, the binder may melt, which reduces or eliminates the need for additional fluid. In another example, a filter may be configured to deposit suspended matter so that the fiber is selected such that it does not react with the suspended matter even at elevated temperatures. It is understood that a wide range of applications can be reconciled with a wide range of possible mixtures and processes. One skilled in the art understands the trade-offs associated with the selection of fibers, binders, pore formers, fluids, and process steps. However, one of the significant advantages of the system 250 its flexibility in the choice of mixture composition and process adaptations.

Once the substrate requirements have been defined, a fiber is taken from Table 1 of 6 selected as in block 253 is shown. The fiber may be of a single type or may be a combination of two or more types. It is also understood that some fibers can be selected to be consumed during the curing process. Also, additives may be added to the fibers, such as coatings on the fibers to introduce other materials into the mixture. For example, dispersants can be applied to fibers to facilitate separation and placement of fibers, or binders can be applied to the fibers. In the case of binders, as the fibers reach the curing temperatures, the binders aid in the formation and flow of bonds in the liquid state.

A typical composition to achieve a porosity> 80%

A binder is then removed from Table 2 of 6 selected as in block 255 is shown. The binder is selected to promote both the green strength and to control burn-off. Likewise, the binder is selected such that it produces sufficient plasticity in the mixture. If necessary, a pore former from Table 3 of 6 selected as in block 256 is shown. In some cases, sufficient porosity can be achieved by using only fibers and binders. The porosity is achieved not only by the natural densification properties of the fibers, but also by the space occupied by the binders, solvents, and other volatile components released during the debonding and curing stages. To achieve higher porosities, additional pore formers can be added.

Pore formers are also selected for their controlled burn-off capabilities and can also aid in the plasticization of the mixture. A fluid, which is usually water, is shown in Table 4, 6 selected as in block 257 is shown. Other liquid materials, such as a dispersant, to aid in the separation and placement of the fibers and plasticizers and extrusion aids to improve the flow behavior of the mixture can be added. This dispersant can be used to control the surface electronic charge on the fibers. In this way, fibers can have a controlled charge to cause individual fibers to repel each other. This facilitates a more homogeneous and arbitrary distribution of the fibers. A typical composition for a mixture that intends to produce a substrate with a porosity> 80% is shown below. It is understood that the mixture can be tuned according to the target porosity, the particular application and the process aspects.

As in block 254 Shown in the block 252 selected fibers are processed so that they have an appropriate form factor distribution. This form factor should preferably be in the range of about 3 are up to about 500 and may have one or more distribution modes. It is understood that other ranges may be selected, for example, around a 1000 form factor. In one example, the distribution of form factors may be arbitrarily distributed over the desired range, and in other examples, the form factors may be selected with more discrete mode values. Form factor has been found to be an important factor in defining compaction properties for the fibers. Accordingly, the shape factor and the distribution of the shape factors are selected such that a particular strength and porosity requirement is realized. It will also be understood that the processing of the fibers into their preferred form factor distribution may be performed at various locations in the process. For example, the fibers may be trimmed by a contractor and provided with a predetermined form factor distribution. In another example, the fibers may be provided in a bulk form and processed into a suitable form factor as a preparatory step in the extrusion process. It is understood that mixing, shear mixing or dispersion mixing and extrusion aspects of the process 250 also contribute to cutting and shredding the fibers. Accordingly, the form factor of the fibers originally introduced into the mixture is different than the shape factor in the cured final substrate. Accordingly, the crushing and cutting action of mixing, shear mixing and extrusion should be used in selecting the correct form factor distribution 254 be included in the process.

With the fibers machined to the proper form factor distribution, the fibers, binders, pore formers and fluids are mixed to a homogeneous mass, as in block 262 is shown. This mixing process may include a dry mixing aspect, a wet mixing aspect and a shear mixing aspect. It has been found that shear or dispersion mixing is desirable to produce a highly homogeneous distribution of fibers within the mass. This distribution is particularly important because of the relatively low concentration of ceramic material in the mixture. When the homogeneous mixture is mixed, the rheology of the mixture can be controlled, as in block 264 is shown. When the mixture is mixed, its rheology is further changed. The rheology can be subjectively tested or measured to match the desired range as shown in Table 5 of FIG 6 is shown. The mixture falling within this desired range has a high probability of extruding properly. The mixture is then extruded to a greenbody substrate as in block 268 is shown.

In the case of screw extruders, mixing can also occur in the extruder itself, not in a separate mixer. In such cases, the history of shearing the mixture must be carefully handled and controlled. The green body substrate has sufficient green body strength to hold its shape and fiber arrangement during the curing process. The greenbody substrate is then cured, as in block 270 is shown. The curing process involves the removal of any residual water, the controlled burning off of most additives, and the formation of the fiber-to-fiber bonds. During the firing process, the fibers maintain their entangled and crossing relationship, and as the curing process continues, bonds are formed at the crossing points or junctions. It is understood that the bonds may result from a bonding process in the liquid state or in the solid state. It is also understood that some of the bonds may be the result of reactions with additives provided in the binder, pore formers, as coatings on the fibers, or in the fibers themselves. After the bonds have been formed, the substrate is slowly cooled to room temperature.

Regarding 8th Now, a method of curing a porous fibrous substrate will be explained. The procedure 275 has a green body substrate with a fibrous ceramic content. The curing process first slowly removes the remaining water from the substrate as in block 277 is shown. Usually, the removal of water can be carried out at a relatively low temperature in an oven. After the residual water has been removed, the organic additives can be burned off, as in block 279 is shown. These additives are burned in a controlled manner to facilitate the proper placement of the fibers and to ensure that leaking gases and residues do not interfere with the fibrous structure. As the additives burn, the fibers maintain their overlapping arrangement and can continue to contact at the crossings or junctions, as in block 281 is shown. The fibers were positioned in these overlapping arrangements using the binder and may have particular patterns formed by the use of pore formers. In some cases, inorganic additives may be used which will bond to the fibers, be consumed during the bond formation process, or remain as part of the final substrate structure. The curing process proceeds to form fiber-to-fiber bonds, as in block 285 is shown. The specific timing and temperature required to create the bonds depends on the type of fibers used, the type of binder used, or Aids and the type of binding desired. In one example, the bond may be a liquid-state sintered bond created between the fibers, as in block 286 is shown. Such bonds are supported by glass formers, glass, ceramic precursors or inorganic fluxes present in the system. In another example, a sintered bond in the liquid state can be produced using sintering aids or agents, as in block 288 is shown. The sintering aids may be provided as a coating on the fibers, as additives, as binders, as pore formers or as the chemical composition of the fibers themselves. Likewise, the fiber-to-fiber bond can be formed by sintering in the solid state between the fibers, as in block 291 is shown. In this case, the intersecting fibers have grain size growth and mass transfer, leading to the formation of chemical bonds at the nodes and to an overall solid structure. In the case of sintering in the liquid state, a mass of bonding material accumulates at the crossing nodes of the fibers and forms the solid structure. It is understood that the curing process can be performed in one or more ovens and can be automated in an industrial tunnel or kiln.

Regarding 9 Now, a method for preparing the fibers will be explained. The procedure 300 shows that bulk fibers are taken up as in block 305 is shown. The bulk fibers usually have very long fibers in a grouped and interlaced arrangement. Such bulk fibers must be processed to sufficiently separate and cut the fibers for use in the blending operation. Accordingly, the bulk fibers become water 307 and possibly a dispersant 309 mixed to a pulp 311 to build. The dispersant 309 For example, it may be a pH regulator or a charge regulator to help the fibers repel each other. It is understood that various other types of dispersants can be used. In one example, the bulk fibers are coated with a dispersant prior to introduction into the slurry. In another example, the dispersant simply becomes the pudding mix 311 added. The porridge is mixed vigorously, as in block 314 is shown. This vigorous mixing serves to cut and separate the bulk fibers into a usable form factor distribution. As previously described, the form factor for the initial use of the fibers is different than the distribution in the final substrate as the mixing and extrusion process further shreds the fibers.

After the fibers have been cut to a suitable shape factor distribution, the water is filtered using a filter press 316 or by pressing against a filter in other equipment for the most part. It is understood that other methods of water removal, such as freeze-drying, may be used. The filter press can use pressure, vacuum or other means to remove the water. In one example, the cut fibers are further dried to a completely dry state, as in block 318 is shown. These dried fibers can then be dry blended 323 where they are mixed with other binders and dry pore formers, as in block 327 is shown. This initial dry mixing helps to create a homogeneous mass. In another example, the water content of the filtered fibers is controlled for the correct moisture content, as in block 321 is shown. In particular, enough water is left in the shredded pulp to facilitate wet mixing, as in block 325 is shown. It has been found that by exiting slightly pulpy water with the fibers, additional separation and distribution of the fibers can be achieved. At the wet mixing stage, binders and pore formers may also be added, and water 329 can be added to achieve the right reology. The mass is also shear mixed, as in block 332 is shown. The shear mixing may also be carried out by passing the mixture through tubular dies using a screw extruder, a twin screw extruder or a shear mixer (such as a sigma blade type mixer). Shear mixing can also take place in a sigma mixer, a high shear mixer and inside the screw extruder. The shear mixing process is to produce a more homogeneous mass 335 desirable having a desired plasticity and extrudable rheology for the extrusion to be effective. The homogeneous mass 335 has a uniform distribution of fibers, with the fibers positioned in an overlapping matrix. In this way, when the homogeneous mass is extruded and cured into a block of substrate, bonding of the fibers to a solid structure is made possible. Further, this solid structure forms an open pore network with high porosity, high permeability and high surface area.

Regarding 10 Now, a method for generating a gradient substrate block will be explained. The procedure 350 is designed to allow the production and extrusion of a substrate block having a gradient characteristic. For example, a substrate may be formed having a first material toward the center of the block and another material toward the outside of the block has. In a more specific example, a material having a lower coefficient of thermal expansion towards the center of the block is used, where particularly high heat is to be expected, while a material having a relatively high coefficient of thermal expansion is used on the outer surfaces where low heat is expected. In this way, a more uniform expansibility for the entire block can be obtained. In another example, selected areas of a block may include higher density ceramic material to provide increased structural support. These structural support members may be concentric or axially disposed in the block. Accordingly, the particular materials may be selected according to desired gradients in porosity, pore size or chemical composition according to the application requirements. Further, the gradient may require the use of more than two materials.

In an example, the gradient structure may be provided by providing a cylinder of a first material 351 be generated. A sheet of a second material 353 gets around the cylinder 351 wrapped around, as by the presentation 355 is shown. In this way, the layer B 353 a concentric tube around the inner cylinder 351 around. The layered cylinder 355 is then placed in a piston extruder where air is evacuated and the mass is extruded through a die. During the extrusion process, material is mixed at the interface between the material A and the material B, facilitating a seamless transition. Such an interface allows for the overlap and bonding of fibers between two different types of materials, thereby promoting a stronger overall structure. Once the material has been extruded, cured and compacted, it creates a filter or catalyst housing 357 with a gradient substrate. In particular, the material A forms in the middle of the substrate while the material B 361 forms at the outer sections. It is understood that more than two materials can be used and that the pore size, porosity and chemical properties can be controlled gradient.

Regarding 11 now becomes another procedure 375 for generating a gradient substrate. In the process 375 is a first cylinder 379 provided in approximately the size of the piston extrusion cylinder. In one example, the outer cylinder 379 the actual cylinder used in the piston extruder. An inner tube 377 is provided, which has a smaller diameter than the outer tube 379 Has. The tubes are concentrically arranged such that the inner tube 377 concentric inside the tube 379 is positioned. Pellets of a first extrudable mixture material 383 are in the pipe 377 while pellets of a second extrudable mixture material 381 in the ring between the pipe 377 and the tube 379 are stored. The inner tube is carefully removed, leaving the material A of the material 381 is surrounded concentrically. The assembly of the material is then placed in the extrusion flask where air is removed from the vacuum and extruded through a die. Once extruded, cured and compacted, a gradient substrate is produced as described with reference to FIG 10 is described. It is understood that more than two concentric rings can be formed, and that different types of gradients can be generated.

Regarding 12 Another method for producing a gradient substrate will be explained. The procedure 400 has a column of an extrudable mixture 402 with alternating discs of two extrudable materials. The extrudable mixture 402 has a first material 403 adjacent to a second material 404 on. In one example, material A is relatively porous while material B is less porous. During extrusion, the material flows through the extrusion die causing the fibers from section A and section B to intermix in an overlapping arrangement. In this way, the respective sections A and B are bonded together to form a fibrous substrate block. After curing and compacting becomes a filter 406 generated. The filter 406 has a first section 407 with relatively high porosity and a second section 408 with less porosity. That way, gas will pass through the filter 406 first filtered through a high porosity region of large pore size and then filtered through a less porous, small pore size region. In this way, large particles in the area 407 deposited while smaller particles in the area 408 be deposited. It is understood that the size and number of the material discs can be controlled according to the application requirements.

The fiber extrusion system offers great flexibility in the application. For example, a wide range of fibers and additives can be selected to form the blend. There are various mixing and extrusion options as well as options for curing, time and temperature. With the teachings disclosed, one skilled in the art of extrusion understands that many variations can be used. The honeycomb substrate is a general design that can be produced using the technique described in the present invention, however For example, other shapes, sizes, contours and shapes can be extruded for different applications.

For certain Applications, such as use with filter devices (DPF, oil / air filter, Hot gas filter, Air filters, water filters, etc.) or catalytic devices (such as 3-way catalysts, SCR catalysts, deodorants, deodorants, biological reactors, chemical reactors, oxidation catalysts, etc.), the channels can be plugged in an extruded substrate. The Clogging may occur in the raw state or on a sintered substrate carried out become. Most constipation compositions require one heat treatment for the curing and bonding with the extruded substrate.

Even though particular preferred and alternative embodiments of the present invention For one of ordinary skill in the art, it will be apparent to one of ordinary skill in the art you can see that many different modifications and extensions the technology described above using the teaching of this can be realized in the invention described herein. All Such modifications and extensions are intended in the real world Sense and scope of the invention as discussed in the appended claims.

Claims (6)

Porous ceramic honeycomb substrate ( 175 ): having a porosity in the range of about 60% to about 85%; having a structure consisting essentially of bonded ceramic fibers ( 30 ), and has a field of honeycomb channels, and wherein the honeycomb substrate ( 175 ) by an extrusion process ( 10 ), comprising the steps of: mixing the ceramic material fiber ( 12 ) with additives ( 16 ) and a fluid ( 18 ) to form an extrudable mixture ( 21 . 52 ) to build; Extruding the extrudable mixture into a honeycomb green body substrate ( 23 ); and curing the green body substrate to the porous honeycomb substrate. porous Ceramic honeycomb substrate according to claim 1, characterized by Sintered, crystal or glass bonds between the fibers. Porous ceramic honeycomb substrate according to claim 1, wherein the cured porous ceramic substrate consists essentially of an open pore network ( 152 ) of ceramic fibers ( 12 ) consists. porous The ceramic honeycomb substrate of claim 1, wherein the bonds are through Sintering or by formation of glass, glass ceramic or ceramic bonds have arisen. Porous ceramic honeycomb substrate ( 175 ) according to claim 1, wherein the ceramic fibers ( 12 ) have a distributed form factor with a mode in the range of 3 to 1000. Porous ceramic honeycomb substrate ( 175 ) according to claim 1, wherein the ceramic fibers ( 12 ) are selected from the following group: Fiber FP, manufacturer DuPont, composition in wt.%> 99% a-Al ₂ O ₃ ; PRD-166, manufacturer Du Pont, composition in wt.% ~ 80% a-Al ₂ O ₃ ~ 20% ZrO ₂ ; Nextel 312, manufacturer 3M, composition in wt.% 62% Al ₂ O ₃ 24% SiO ₂ 14% B ₂ O ₃ ; Nextel 720, manufacturer 3M, composition in wt.% 85% Al ₂ O ₃ 15% SiO ₂ ; Nextel 550, manufacturer 3M, composition in wt.% 73% Al ₂ O ₃ 27% SiO ₂ ; Nextel 610, manufacturer 3M, composition in wt.% 0.2-0.3% SiO ₂ 0.4-0.7% Fe ₂ O ₃ > 99% a-Al ₂ O ₃ ; Almax, manufacturer Mitsu Mining, composition in wt.%> 99% a-Al ₂ O ₃ ; Altex, manufacturer Sumitomo, 85%? -Al ₂ O ₃ 15% SiO ₂ ; Saphikon, manufacturer Saphikon, composition in wt.% 100% Al ₂ O ₃ ; Nicalon NL200, composition Si-CO; Hi-Nicalon, composition Si-C; Tyranno Lox M, composition in Si-CO-Ti; Sylramic, composition SiC, TiB ₂ ; Cloning, composition Si-NC; SCS-6, composition SiC; Nextel 610, composition Al ₂ O ₃ ; Nextel 720, composition Al ₂ O ₃ -SiO ₂ ; Almax, composition Al ₂ O ₃ ; Sapphire, composition Al ₂ O ₃ (single crystal)