| Title of Invention | MULTILAYER MOUNTING MATS AND POLLUTION CONTROL DEVICES CONTAINING SAME |
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| Abstract | A mullilayer mat for mounting a pollution control element in a pollution control device. The mat comprises at least one non-intumescent layer comprising ceramic fibers and having a width defined by opposite lateral edges, and at least one intumescenl layer comprising an inlumescent material and having a width defined by opposite lateral edges. The width of the intumescent layer is less than the width oi the non-lnlumesccnt layer. The intumescent layer can have an exposed major surface. |
| Full Text | MULTILAYER MOUNTING MATS AND POLLUTION CONTROL DEVICES CONTAINING SAME Field of the Invention The present invention relates to systems for mounting a pollution control element in a pollution control device (e.g,, catalytic converters, engine exhaust filters, etc), in particular, to mats for mounting pollution control elements and, more particularly, such mounting mats having multiple layers. Ihe present invention also relates to pollution control devices using such mounting mats and exhaust systems that include such devices. Background Pollution control devices are used to reduce atmospheric pollution fron^ the exhaust systems of internal combustion engines such as, for example, those used in motor vehicles (e.g., automobiles, watercraft, aircraft, etc.), power generators and the like. Two typical types of such pollution control devices are catalytic converters and exhaust system fillers (e.g., diesel particulate filters) or traps. Catalytic converters contain one or more catalyst support elements, which are typically monolithic structures coated with desired catalyst material. The monolithic structure is typically made of ceramic, although metals have also been used. The catalyst(s) oxidize carbon monoxide and hydrocarbons or reduce the oxides of nitrogen in exhaust gases. Exhaust system filters typically include a filter element in the form of a honeycombed monolithic structure made from porous crystalline ceramic materials, hi the current state-of-the-art construction of these pollution control devices, their monolithic structure is mounted within a metal housing. Protective packing or mounting materials are typically positioned between the pollution control element (e.g., monolithic structure) and the metal housing to protect the pollution control element, for example, from road shock and vibration and to prevent exhaust gases from passing between the pollution control element and the metal housing. When a ceramic monolithic structure is used, such mounting materials typically need to compensate ibr the thermal expansion difference between the metal housing and the ceramic monolith. The process of mounting such a monolithic structure in a housing, with a mounting material, is referred to as 'canning". Such mounting processes have included inserting the monolith into the housing and injecting a paste into the gap between the monolith and the metal housing. Other mounting processes have also included wrapping a sheet material or mat around the monolith and inserting the wrapped monolith into the housing and welding the housing closed. The compositions used to form conventional mounting materials have included a variety ot non-intumescent materials and inlumescent materials. The present invention is an improvement over such prior pollution control element mounting systems. Summary ■ .1 ■ •\m PHI n ii ^1 ■ ti The present invention can provide one or more of multilayer mounting mats lor mounting a pollution control element in a pollution control device (e.g., catalytic converters, engine exhaust filters, etc.), pollution control devices including such multilayer mats, exhaust systems including such pollution control devices, and methods for making such mats, devices and exhaust systems. In one aspect, a multilayer mat is provided for mounting a pollution control element in a pollution control device. The mat may comprise at least one non-intumescent layer comprising ceramic fibers and having a width defined by opposite lateral edges, and at least one intumescent layer comprising an intumescent material and having a width defined by opposite lateral edges. The width of the intumescent layer is less than the width of the non-intumescent layer. It is desirable for the intumescent layer to have an exposed major surface. When the mat is used in a pollution control device operated at relatively high temperatures, the exposed major surface of the intumescent layer faces and may make direct contact with the housing of the pollution control device, such that the non-intumescent layer is disposed between the intumescent layer and the pollution control element. In this way, the non-intumescent layer insulates and protects the intumescent layer from the relatively high operating temperatures. In some applications, in contrast, where the operating temperatures of the pollution control device are relatively low, the intumescent layer faces and may make contact with the pollution control element and at least part of the non-intumescent layer is disposed between the housing and the intumescent layer. This latter embodiment can be useful when the heat generated by the pollution control element is not high enough to substantially harm the ability of the intumescent layer to expand intumescently, but the pollution control element does not get hot enough to cause such intumescent expansion, when the non-intumescent layer is disposed between the pollution control element and the intumescent layer. The at least one non-intumescent layer and the at least one intumescent layer may be joined together, 1 he at least one non-intumescent layer may comprise at least two non-intumescenl layers, the at least one intumescent layer may comprise at least two intumescent layers, or both the at least one non-intumescent layer may comprise at least two non-intumescent layers and the at least one intumescent layer may comprise at least two intumescent layers. i he composition of each of the at least two non-intumescent layers may be different. For example, one non-intumescent layer may be more resilient than another non-intumescent layer. The composition of each of the at least two intumescent layers may be different, such that the two layers have different expansion, compression and/or erosion properties. The width of each of the at least two non-intumescent layers may be different. It is also contemplated that the width of each of the at least two intumescent layers may different. However, it is preferred that the width of each intumescent layer be less than the width of each non-intumescent layer. In at least one embodiment, the at least one non-intumescent layer and the at least one intumescent layer are disposed relative to one another such that both lateral edges of the at least one intumescent layer are positioned within the lateral edges of the at least one non-intumescent layer. In at least one embodiment, the at least one non-intumescent layer and the at least one intumescent layer are disposed relative to one another such that one of the lateral edges of the at least one intumescent layer is substantially in-line with one of the lateral edges of the at least one non-intumescent layer, and only the other lateral edge of the at least one intumescent layer lies within the lateral edges of the at least one non-intumescent layer. The non-intumescent layer may have a thickness in the range of from about 0.5 mm to about 20 mm and a bulk density in the range of from about 0.05 g/cc to about 0.4 g/cc, and the intumescent layer may have a thickness in the range of irom about 0.5 mm to about 15 mm and a bulk density in the range of from about 0.4 g/cc to about 0.75 g/cc. hi at least one embodiment, the multilayer mat may further comprise a non-inlumescent strip of one or more layers comprising ceramic fibers. The strip may be positioned alongside one lateral edge of the at least one intumescent layer. Preferably, the width of the strip is narrower than the width of the at least one intumescent layer. It is als(v preferred that the combined widths of the non-inlumescent strip and the intumescent layer are together substantially equal to the width of the non-intumescent layer. It is also contemplated that another non-inlumescent strip of one or more layers comprising ceramic fibers may also be provided. One non-intumescent strip may be disposed alongside each lateral edge of the at least one intumescent layer, wherein the width of each strip is narrower than the width of the at least one intumescent layer. Preferably, the combined widths of both the non-inlumescenl strips and the intumescent layer are together substantially equal to the width of the non-intumescent layer. I he non-intumescent strip and the at least one intumescent layer may be substantially co-planar. Each non-intumescent strip may have a length that is substantially equal to the length of the at least one intumescent layer. Hach non-intumescent strip may be more resilient than the non-intumescen! layer. Alternatively, the non-intumescent layer may be more resilient than any non-inlumescenl strip. Hach non-intumescent strip may have a thickness in the range of from about 0.5 mm to about 20 mm and a bulk density in the range of from about 0.05 g/cc to aboul ,4 g/cc. fhe non-intumescent layer may have a thickness in the range of from about 0.5 mm to about 20 mm and a bulk density in the range of from about 0.05 g/cc to aboul 0.4 g/cc. The intumescent layer may have a thickness in the range of from aboul 0.5 mm to aboul 15 mm and a bulk density in the range of Irom about 0.4 g/cc to about 0.75 g/cc. In accordance with a second aspect, a pollution control device is provided comprising a housing having an inner wall, a pollution control element disposed in the housing so as to form a gap therebetween, and a muUilayer mat, sucli as one of Ihe mullilayer mats discussed above. The mullilayer mat is disposed in the gap so as to mount the pollution control element in the housing. In accordance with at least one embodiment, a portion of the inner wall of the housing may define a recess. The mat may be positioned in the housing so that at least a portion of only the intumescent layer is received within the recess. In accordance with at least one embodiment, a portion of the inner wall of the housing defines a recess. The mat may be positioned so that at least a portion of the intumescent layer is received within the recess, and neither lateral edge oi the intumescent layer is exi^osed to exhaust gases passing through the pollution control device. In accordance with at least one embodiment, a portion ofthe inner wall of the housing defines a recess. The mat may be positioned so that the intumescent layer is received within the recess, and one lateral edge ofthe intumescent layer is exposed to exhaust gases passing through the pollution control device. In accordance with at least one embodiment, a portion ofthe inner wall ofthe housing defines a recess. The mat may be positioned so that the intumescent layer is received within the recess and not exposed to exhaust gases passing through the pollution control device, and one intumescent strip is exposed to exhaust gases passing through the pollution control device. Preferably, the non-intumescent layer is positioned adjacent the pollution control element. The non-intumescent layer may be in contact with the pollution control element. The intumescent layer may be positioned adjacent the inner wall ofthe housing. In accordance with at least one embodiment, at least one ofthe lateral edges ofthe intumescent layer may be substantially sealed from exposure to exhaust gases passing lhr(High the pollution control device. The pollution control device may comprise a catalytic converter or an exhaust system filter. In accordance with a third aspect, an exhaust system for an internal combustion engine is provided and comprises a pollution control device constructed in accordance with any one ofthe embodiments discussed above. Brief Description of the Drawings Fig. 1 is a schematic cross sectional view of a mat constructed in accordance with a first embodiment; Fig. 2 is a schematic top view ofthe mat illustrated in Fig. 1; Fig. 3 is a perspective exploded view of a catalytic converter including the mat illustrated in Fig. 1; Fig. 4 is a schematic cross sectional view of a catalytic converter including the mal of Fig. 1; Fig. 4A is a schematic cross sectional view of a catalytic converter including a metal housing with a recess and multilayer mat formed in accordance with a Ihird embodiment; I'ig. 5 is a schematic cross sectional view of a catalytic converter including a multilayer mat formed in accordance with a fourth embodiment; Fig, 5 A is a schematic cross sectional view of a catalytic converter including a multilayer mat ibrmed in accordance with a Jifth embodiment; Fig. 6 is a schematic cross sectional view of a multilayer mat formed in accordance with a sixth embodiment; Fig. 7 is a schematic cross sectional view of a catalytic converter including the mat of Fig. 6; Fig, 8 is a schematic cross sectional view of a multilayer mat formed in accordance with a seventh embodiment; Fig, 9 is a schematic cross sectional view of a catalytic converter including ihe mat of Fig. 8; Fig. 10 is a schematic cross sectional view of a catalytic converter including a multilayer mat formed in accordance with an eighth embodiment; fig. 11 is a schematic cross sectional view of a multilayer mat formed in accordance with a ninth embodiment; Fig. 12 is a schematic cross sectional view of a catalytic converter including the mat of Fig. 11; and Fig. 13 is a schematic cross sectional view of a catalytic converter including a multilayer mat formed in accordance with a second embodiment. Detailed Dcscrintion A multilayer mat 10, constructed in accordance with a first embodiment, is illustrated in Figs. 1 and 2. As will be discussed below, the mal 10 may be used for mounting a pollution control element in a pollution control device. Ihe mat 10 comprises a non-intumescent layer 12 comprising suitable ceramic or other inorganic fibers and has a width W| defined by opposite lateral edges 14 and 16 and a length Li. fhe mat 10 further comprises an intumescent layer 20 comprising intumescent material and has a width W2 defined by opposite lateral edges 22 and 24 and a length L2. In the illustrated embodiment, the width W2 of the intumescent layer 20 is less than the width Wi olThe non-intumescent layer 12. Further, the intumescent layer 20 is positioned relative to the non-intumescent layer such that its two lateral edges 22 and 24 are positioned within the two lateral edges 14 and 16 of the non-intumescent layer 12. As illustrated in I'ig. 1, the intumescent layer 20 comprises an exposed major surface 20A having an area defined by its width W2 times its length L2. The major surface 20A also defines an outermost layer ol' the mat 10. As noted above, the mat 10 may be used to mount a pollution control element in a pollution control device. For example, the mat 10 may be used to mount a pollution control element comprising a catalyst support element 40, which, in the illustrated embodiment, comprises a monolithic structure coated with a catalyst material in a metal housing 50, see Figs. 3 and 4. The catalyst support element 40, mat 10 and metal housing 50 deiine a catalytic converter 60, see Fig. 3. The metal housing 50 has an inlet 52 and an outlet 54 through which exhaust gases flow into and out of the catalytic converter 60. The metal housing 50 can be formed from one or more metals, metal alloys, or intermediate compositions, such as stainless steel or austenitic steel. Preferably, a substantially resilient non-intumescent layer 12 is selected such that once the mat 10 and the catalyst support element 40 have been mounted within the metal housing 50, outer portions 18A and 18B of the non-intumescent layer 12 fill the gap Ci, in at least the seal areas As, between an inner wall of the housing 50 and the support element 40, see Fig. 4, so as to seal the gap G and protect the lateral edges 22 and 24 of the intumescent layer 20. The outer portions 18A and 18B resiliently fill the gap (), when at ambient temperature or a high operational temperature. In other words, at least the outer portions 18A and 18B of the non-intumescent layer 12 are resilient enough to exert a sufficient pressure to seal the gap G and protect the intumescent layer 20, whether the gap G is at ils smallest (i.e., at ambient temperature) or biggest (i.e., at the highest operating temperature). It is desirable for at least these outer portions 18A and 18B to also be durable enough to survive cycling of the gap G between its smallest and biggest over the desired life of the pollution control device. It can be preferable for the entire non-intumescent layer 12 to exhibit this degree of resilience and durability. Hence, the intumescent layer lateral edges 22 and 24 are substantially sealed from exposure to exhaust gases, especially high temperature exhaust gases, flowing through the catalytic converter 60. When the catalytic converter 60 experiences high operational temperatures, exposure of the intumescent layer 20 to high temperature exhaust gases can damage the intumescent material in (i.e., the intumescent characteristics ol) the layer 20, especially along exposed surfaces. Such damage can exacerbate the erosion of the layer 20 with increased exposure to the flowing exhaust gases. For example, vermiculite, which can be used to form part of some intumescent layers 20, can loose its intumescent characteristics when exposed to temperatures in excess of about 750 *'C. I lence, if the intumescent layer 20 is exposed to such damaging high temperatures, damaged portions of the layer 20 may be unable to sufficiently expand and fill the gap G wilh enough of a mounting force to prevent erosion of the layer 20. liven if exposed to exhaust gases at below such damaging high temperatures, the exhaust gases can still cause erosion of the layer 20. By insulating or shielding the intumescent layer 20 from exposure to exhaust gases via the outer portions 18A and 18B of the non-intumescent layer 12 and also insulating the layer 20 from high temperatures radiated by the element 40 via the non-intumescent layer 12, the intumescent layer 20 is, therefore, less likely to lose its intumescent capability to expand as the metal housing 50 expands due to increased temperatures during use of the catalytic converter 60. Because some intumescent materials are less expensive than some non-intumescent materials, this embodiment can provide a mat formed at a lower cost than mats formed primarily oi non-intumescent material(s) yet still function in an adequate manner to maintain a catalyst support element 40 tightly supported within a catalytic converter metal housing 50 during use of the catalytic converter 60. In addition to being left unsecured to each other, the intumescent layer 20 can be joined to the non-intumescent layer 12 such as, for example, by using adhesive, needle bonding, stitching, tape banding, tag attachment or co-forming, or adjacent portions of the material defining the layers 12 and 20 may be mechanically interconnected with one another. Although Figs. 1 and 2 illustrate a mat 10 comprising only two layers, one or more additional intumescent layers may be provided and/or one or more additional non-intumescent layers may be provided, the different intumescent layers may have different properties, such as different expansion, compression and/or erosion properties. Ihe different non-intumescent layers may also have different properties, such as different resiliency values and/or maximum temperature limitations. An additional example of a multilayer mat constructed in accordance with the first embodiment includes layers arranged in the following order: intumescent/non-intumescent/intumescent/non-intumescent. As used herein, the term "intumescent layer" refers to a layer that expands intumescently, other than only as a result of its coefficient of thermal expansion, for example by the inclusion of intumescent expanding materials such as vermiculite, expandable graphite, micas, and like materials. Typically, such layers need to be protected from erosion caused by exposure to hot exhaust gases. As used herein, the term 'non-intumescent layer" refers to a layer that exhibits very little or no intumescent expansion, that is, most or all of any expansion of the layer from heat exposure is the result of its coefficient of thermal expansion. Examples of non-intumescent materials include, without limitation, ceramic and other inorganic fibers. Specific examples of substantially resilient non-intumescenl materials from which the non-intumescent layer 12 may be formed include materials commercially available from 3M Company (St. Paul, MN) under the trade designation "INTERAM lOOOl 11," ^INfERAM 110()HT;'"INTERAM 1 IOIHT;'^MNTERAM 1200NC,"-MN'ri:RAM 15001 IT," '^INTERAM 1535H1," "IN TERAM 1550ilT," "IN fERAM 1600111,"and "IN1 ERAM 1600H fE." Specific example intumescent materials from which the intumescent layer 20 may be formed include materials commercially available from 3M Company (St. Paul, MN) under the trade designation "INTERAM 100," "IN 1 liRAM 200," "INI ERAM 550," "INTERAM 2000L1," "INTERAM X-D," ^iN lliRAM 1M," "IN IITIAM 1S," "INTERAM 570NC," and "IN 1 ERAM 600NC." l\)r a catalytic converter 60 having a mat 10 comprising a resilient non-intumescent layer 12 formed from "INTERAM 11OOH f" or "IN I ERAM 1535111" and an intumescent layer 20 formed from "INTERAM 550" or "INIERAM 1M," and a gap (i between an inner wall of the housing 50 and the support element 40, see fig. 4, equal to about 3 mm, it is believed that the resilient non-intumescent layer 12 can have a minimum basis weight of about 750 g/m , the intumescent layer 20 can have a minimum basis weight of about 675 g/m", and wherein the density of the combined non-intumescent layer 12 and intumescent layer 20 in a mount area AM of the gap G is equal to aboul 0.475 g/cc and the density of outer portions 18A, 18B of the non-intumescent layer 12 in the seal areas As of the gap G is equal to about 0.25 g/cc. I'or a gap equal to about 4 mm, it is believed that the resilient non-intumescent layer 12 can have a minimum basis weight of aboul 1000 g/m , the intumescent layer 20 can have a minimum basis weight of about 000 -f g/nr, and wherein the density of the combined non-intumescent layer 12 and intumescent layer 20 in the mount area AM of the gap G is equal to about 0.475 g/cc and the density of outer portions 18A, 18B of the non-intumescent layer 12 in the seal areas As of the gap (i is equal to about 0.25 g/cc. For a gap equal to about 6 mm, it is believed that the resilient non-intumescent layer 12 can have a minimum basis weight of aboul 1500 g/m~, the intumescent layer 20 can have a minimum basis weight of about 1350 g/nr, and wherein the density of the combined non-intumescent layer 12 and intumescent layer 20 in the mount area AM of the gap G is equal to about 0.475 g/cc and the density of outer portions 18A, 18B of the non-intumescent layer 12 in the seal areas As of the gap G is equal to about 0.25 g/cc. For a gap equal to about 8 mm, it is believed that the resilient non- intumescent layer 12 can have a minimum basis weight of aboul 2000 g/m^, the intumescent layer 20 can have a minimum basis weight of about 1800 g/m\ and wherein the density of the combined non-intumescent layer 12 and intumescent layer 20 in the mount area AM of the gap G is equal to about 0,475 g/cc and the density of outer portions 18 A, 18B of the non-intumescent layer 12 in the seal areas As of the gap G is equal to about 0,25 g/cc. In each of the prophetic examples set out above, in the mount area AM ol" the gap G where both the intumescent and non-intumescent layers 20 and 12 are positioned, it is believed that the intumescent layer 20 will fill approximately 25% of the gap, while the non-intumescent layer 12 will fill about 75% of the gap. It is believed that the outer portions 18A, I8B of the non-intumescent layer 12 in the seal areas As of the gap G, if provided at a minimum density of about 0.25 g/cc, will function in an acceptable manner to insulating the intumescent layer 20 from exposure to exhaust gases. It is contemplated that the mat 10 illustrated in Figs. 1-2 may also be used in low temperature applications. Such a multilayer mat 710, in accordance with a second embodiment, is illustrated in Fig. 13. Ihe mat 710 comprises a non-intumescent layer 712 comprising ceramic fibers and has a width Wi defined by opposite lateral edges 714 and 716 and a length L|. The mat 710 further comprises an intumescent layer 720 comprising intumescent material and has a width W2 defined by opposite lateral edges 722 and 724 and a length L2. In the illustrated embodiment, the width W2 of the intumescent layer 720 is less than the width W| of the non-intumescent layer 712. Further, the intumescenl layer 720 is positioned relative to the non-intumescent layer such that its two lateral edges 722 and 724 are positioned within the two lateral edges 714 and 716 of Ihe non-iniumescenl layer 712. As illustrated in Fig. 13, the inlumescent layer 720 comjirises an exposed major surface 720A having an area defined by its width W2 times its length I.2- I he major surlace 720A also defines an innermost layer of the mat 710. As illustrated in Fig, 13, the mat 710 is positioned so as to mount a pollution control element, such as a catalyst support element 40, in a metal housing 50. fhe calalysl support element 40, mat 710 and metal housing 50 define a catalytic converter 760, Preferably, a substantially resilient non-intumescent layer 712 is selected such that once the mat 710 and the catalyst support element 40 have been mounted within the melal housing 50, outer portions 718A and 718B of the non-intumescent layer 712 sufficiently expand in the seal areas As of a gap G, between an inner wall of the housing 50 and the support element 40, so as to seal the lateral edges 722 and 724 of the intumescent layer 720, as the gap G expands with increasing temperatures. Thus, the outer portions 718A and 7! 8B continue to fill the gap G when at ambient temperature or a high operational temperature. In other words, at least the outer portions 718A and 7181i of the non-intumescent layer 712 are resilient enough to exert a sufficient pressure to seal the gap (i and protect the intumescent layer 720, whether the gap G is at its smallest (i.e., at ambient temperature) or biggest (i.e., at the highest operating temperature). It is desirable for at least these outer porfions 718A and 718B to also be durable enough to survive cycling of the gap G between its smallest and biggest over the desired life of the pollution control device. It can be preferable for the entire non-intumescent layer 712 to exhibit this degree of resilience and durability. Hence, the intumescent layer lateral edges 722 and 724 are substantially sealed from exposure to high or low temperature exhaust gases fiowing through the catalytic converter 760. In the pollution control device 60 of Figs. 3-4, the intumescent layer 20 Jbrms an outermost layer of the mat 10. llencQ, the mat 10 is advantageous for use in mounting a pollution control element in a pollution control device that operates at high temperatures such that the intumescent layer 20 faces and makes contact with the pollution control device metal housing. As a result, energy in the form of heat is transferred efficiently from the intumescent layer 20 to the metal housing so as to help protect the intumescent layer 20 from overheating, when exposed to high temperatures. I he intumescent layer 20 is also protected from high temperatures radiated by the element 40 via the non-intumescent layer 12. In the pollution control device 760 of Fig. 13, the intumescent layer 720 forms an innermost layer of the mat 710. Hence, the mat 710 is advantageous for use in mounting a pollution control element, such as element 40, in a pollution control device that operates at relatively low temperatures such that the intumescent layer 720 laces and makes contact with the pollution control element so that the intumescent layer 720 receives sufllcient energy in the form of heat to cause the layer 720 to intumescently expand to the degree desired. In a third embodiment, where like reference numerals indicate like elements, a mat 1OA is used to support and mount a support element 40 in a metal housing 150 so as to defme a catalytic converter 180, see Fig. 4A. Ihe metal housing 150 is rolled or otherwise formed so as to include a recess 150A, which, in the illustrated embodiment, extends about the entirety of the housing 150. By forming the recess 150A within the housing 150, the stiffness of the housing is enhanced. I he housing recess 150A is shaped in X and Z directions so as to define a pocket sized to receive the intumescent layer 20 and shaped to substantially shield the intumescent layer lateral edges 22 and 24 from exhaust gases passing through the catalytic converter 180. Because the gap GA does not accommodate the thickness of both the intumescent layer 20 and the non-intumescent layer 13, the layer 13 does not need to expand as much to sufficiently fill the gap GA, as the gap increases with increasing temperature. As a result, the non-intumescent layer 13 in the lig. 4A embodiment may be formed from a material having less resiliency than the material used to ibrm the non-intumescent layer 12 in the Fig. 4 embodiment. For example, the non-intumescent layer 13 may be formed from a material commercially available from 3M Company (St. Paul, MN) under the trade designation "INTERAM 900111." A multilayer mat 70 constructed in accordance with a fourth embodiment is illustrated in Fig. 5, where like reference numerals indicate like elements. Ihe mat 70 comprises a non-intumescent layer 12 comprising ceramic fibers and has a width W| defmed by opposite lateral edges 14 and 16 and a length Li. The mat 10 further comprises an intumescent layer 72 comprising intumescent material and has a width W3 defined by opposite lateral edges 74 and 76 and a length substantially equal to length L| olthe non-intumescent layer 12. In the illustrated embodiment, the width W3 of the intumescent layer 72 is less than the width W| of the non-intumescenl layer 12. Further, the intumescent layer 72 is positioned relative to the non-intumescent layer 12 such that lateral edge 74 is positioned within the two lateral edges 14 and 16 of the non-intumcscent layer 12 and lateral edge 76 is substantially in-line with lateral edge 16. In Fig. 5, the mat 70 is shown provided within a metal housing 50 so as to support and maintain a catalyst support element 40 within the housing 50. The mat 70, housing 50 and support element 40 define a catalytic converter 80. Exhaust gases pass through the catalytic converter 80 from left to right as viewed in Fig. 5. Preferably, a substantially resilient non-inlumescent layer 12 is selected for use in the catalytic converter 80 such that once the mat 70 and the catalyst support element 40 are positioned within the metal housing 50, an outer or exposed portion 18A of the non-intumescent layer 12 fills the gap G so as to seal and protect the lateral edge 74 of the intumescent layer 72. Hence, the intumescent layer lateral edge 74 is sul")slantially sealed from direct exposure to high temperature exhaust gases tlowing through the catalytic converter 80. It is noted that in the Fig. 5 embodiment, the other lateral edge 76 olthe intumescent layer 72 is not sealed by the non-inlumescent layer 12. However, because the lateral edge 76 is not directly exposed to the incoming tlow of the exhaust gases, loss of intumescent material from lateral edge 76 may be minimal or insubstantial for some catalytic converter designs such as, for example, substantially round housing designs. rhe non-intumescent layer 12 may be formed from one of the same materials, set out above, from which the layer 12 in the Fig. 1 embodiment is formed, fhe intumescent layer 72 may be formed from one of the same inlumescent materials, set out above, from which the layer 20 in the Fig, 1 embodiment is formed. In the Fig. 5 embodiment, the intumescent layer 72 is shown positioned adjacent to the catalytic converter metal housing 50. However, for some applications, such as low temperature applications, the intumescent layer 72 may be positioned adjacent to the catalyst support element 40. In a tifth embodiment, where like reference numerals indicate like elements, a mat 170 is used to support and mount a support element 40 in a metal housing 250 so as to define a catalytic converter 280, see Fig. 5A. fhe melal housing 250 is Ibrmed so as to include a recess 250A, which, in the illustrated embodiment, extends about the entirety ol the housing 250. I he housing recess 250A is shaped in X and Z directions so as lo receive the intumescent layer 72 and substantially shield the intumeseeni layer lateral edge 74 from exhaust gases passing through the catalytic converter 280, Hence, the intumescent layer lateral edge 74 is substantially sealed (roni direct exposure to incoming high (emperalure exhaust gases flowing through the catalytic converter 280. It is noted that in the Fig. 5 A embodiment, the lateral edge 76 of the intumescent layer 72 is not sealed by the non-intumescent layer 13. However, because the lateral edge 76 is not positioned in the incoming path of the exhaust gases, loss oi intumescent material from lateral edge 76 may be minimal for some catalytic converter housing designs. It is also noted that because the non-intumescent layer 13 does not need to expand as substantially in the Z direction to shield tlie lateral edges 74 and 76 ol^the intumescent layer 72 from exhaust gases, the non-intumescent layer 13 in the Fig. 5A embodiment may be formed from a material having less resiliency than the material used to form the non-intumescent layer 12 in the I'ig. 5 embodiment. For example, the non-intumescent layer 13 may be Ibrmed from the same non-intumescent material, set out above, from which the non-intumescent layer 13 in the Fig. 4A embodiment is formed. A multilayer mat 90 constructed in accordance with a sixth embodiment is illustrated in Fig. 6, where like reference numerals indicate like elements. The mat 90 comprises an inner non-intumescent layer 13 comprising ceramic fibers and has a width Wi defined by opposite lateral edges 14 and 16 and a length L|. The mat 10 further comprises an intumescent layer 20 comprising intumescent material and has a width W2 defined by opposite lateral edges 22 and 24 and a length substantially equal to length F| of the non-intumescent layer 13. In the illustrated embodiment, the width W2 of the intumescent layer 20 is less than the width Wi of the non-intumescent layer 13, Further, the intumescent layer 20 is positioned relative to the non-intumescent layer 13 such that the lateral edges 22 and 24 are positioned within the two lateral edges 14 and 16 of the non-intumescent layer 13. 1 he multilayer mat 90 further comprises first and second strips 92 and 94, respectively, of non-intumescenl material, I he first non-intumescent strip 92 is positioned over a first outer portion 18A of the non-intumescent layer 13 and the second non-intumescent strip 94 is positioned over a second outer portion 18B of the non-intumescent layer 13. Ihe first non-intumescent strip 92 has a width W4 and a length substantially equal to the lengths of the inner non-intuniescen( layer 13 and the intumescent layer 20. fhe second non-intumescent strip 94 has a width W5 and a length substantially equal to the lengths of the inner non-intumescent layer 13 and the intumescent layer 20, In the illustrated embodiment, the summation of the width W2 of the intumescent layer 20, the width W4 of the first non-intumescent strip 92 and the width Ws of the second non-intumescenl strip 94 is substantially equal to the width W| of the inner non-intumescent layer 13. In Fig. 7, the mat 90 is shown provided within a metal housing 50 so as to support and maintain a catalyst support element 40 within the housing 50. fhe mal 90, housing 50 and support element 40 define a catalytic converter 380. Preferably, the non-intumescent strips 92 and 94 are formed from a substantially resilient non-intumescent material for use in the catalytic converter 380 such that once the mat 90 and the catalyst support element 40 are positioned within the metal housing 50, the strips 92 and 94 sufficiently expand in seal areas As of a gap G, between an inner wall of the housing 50 and the support element 40, see Fig. 1, so as to seal the lateral edges 22 and 24 of the intumescent layer 20, as the gap G expands with increasing temperatures. In other words, at least the strips 92 and 94 are resilient enough to exert a sufllcient pressure to seal the gap G and protect the lateral edges 22 and 24 of the intumescent layer, whether the gap G is at its smallest (i.e., at ambient temperature) or biggest (i.e., at the highest operating temperature). It is desirable for at least these strips 92 and 94 to also be durable enough to survive cycling of the gap G between its smallest and biggest over the desired life of the poUvUion control device. It can be preferable for the non-intumescent layer 13 to also exhibit this degree of resilience and durability. Hence, the intumescent layer laleral edges 22 and 24 are substantially sealed from exposure to high temperature exhaust gases flowing through the catalytic converter 380. It is noted that the inner non-intumescent layer 13 may be formed from a material which is less resilient than the non-intumescent strips 92 and 94. Typically, a less resilient non-intumescent material is less expensive than a more resilient non-intumescent material. For example, the non-inlumescent strips 92 and 94 may be formed from one of the same materials, set out above, IVom which the layer 12 in the Fig. 1 embodiment is formed. The intumescent layer 72 may be formed from one of the same intumescent materials, set out above, from which the intumescent layer 20 in the Fig. 1 embodiment is formed. The non-intumescenl layer 13 may be formed from the same non-intumescent material, set out above, from which the non-intumescent layer 13 in the Fig. 4A emliodimenl is formed. It is also contemplated that the non-intumescent strips 92 and 94 may be formed from a less resilient non-intumescent material while the non-intumescent layer 13 may be formed from a substantially resilient non-intumescent materiaL In this embodiment, once the mat and the catalyst support element 40 are positioned within the metal housing 50, the non-intumescent layer 13 provides the resiliency needed to seal areas As of the gap (i between the inner wall of the housing 50 and the support element 40 so as to protect the lateral edges 22 and 24 of the intumescent layer 20 during low and high operating temperatures of the pollution control device. For a catalytic converter 380 having a mat 90 comprising a non-intumescent layer 13 formed from "INTERAM 900HT," an intumescent layer 20 formed from "IN 11 ;KAM 100" or "INTERAM 550" and non-intumescent strips 92, 94 formed from "IN fERAM llOOiriV "INTERAM 11011 if," ^MNTERAM 1535HT," or "IN IliRAM l600!nT^" and having a gap G between an inner wall of the housing 50 and the support element 40, see Fig. 7, equal to about 3 mm, it is believed that the non-intumescent layer 1 3 may have a minimum basis weight of about 750 g/m~, the intumescent layer 20 may have a minimum basis weight of about 1550 g/m", and each non-intumescent strip 92 and 94 may have a minimum basis weight of about 450 g/m^ and wherein the compressed density of the combined non-intumescent layer 13 and intumescent layer 20 in a mount area AM of the gap G is about 0.77 g/cc and the compressed density of the combined non-intumescent layer 13 and a strip 92 or 94 in each seal area As of the gap G is equal to about 0.40 g/cc. For a gap equal to about 4 mm, it is believed that the non-intumescent layer 13 may have a minimum basis weight of about 1020 g/m^, the intumescent layer 20 may have a minimum basis weight of about 2100 g/m^, and each non-intumescent strip 92 and 94 may have a minimum basis weight ol" about 600 g/m" and wherein the compressed density of the combined non-intumescent layer 13 and intumescent layer 20 in the mount area AM of the gap G is about 0.77 g/cc and the compressed density ol the combined non-intumescent layer 13 and a strip 92 or 94 in each seal area As of the gap G is equal lo about 0,40 g/cc. For a gap equal to about 6 mm, it is believed that the non-intumescent layer 13 may have a minimum basis weight of about 1435 g/m", the intumescent layer 20 may have a minimum basis weight of about 3100 g/m", and each non-inlumescenl strip 92 and 94 may have a minimum basis weight of about 900 g/m^ and wherein the compressed density of the combined non-intumescent layer 13 and intumescent layer 20 in the mount area AM of the gap G is about 0.77 g/cc and the compressed density of the combined non-intumescent layer 13 and a strip 92 or 94 in each seal area As ot the gap G is equal lo about 0.40 g/cc. For a gap equal to about 8 mm, it is believed that the non-intumescenl layer 13 may have a minimum basis weight of about 2000 g/m^, the intumescenl layer 20 may have a minimum basis weight of about 4695 g/m~, and each non-intumescent strip 92 and 94 may have a minimum basis weight of about 1200 g/m" and wherein the compressed density of the combined non-intumescent layer 13 and Intumescent layer 20 in the mount area AM of the gap G is about 0.77 g/cc and the compressed density ot^ the combined non-intumescent layer 13 and a strip 92 or 94 in each seal area As of the gap G is equal to about 0,40 g/cc. In each of the prophetic examples set out above, in the mount area AM of the gap G where the intumescent and non-intumescent layers 20 and 13 are positioned, it is believed that the intumescent layer 20 will fill approximately 60% of the gap G, and the non-intumescent layer 13 will till about 40% of the gap Ci. In each of the prophetic examples set out above, in the seal areas As of the gap G where the non-intumescent layer 13 and a non-intumescent strip 92 or 94 are positioned, it is believed that the non-intumescent layer 13 will fill approximately 60% of the gap, and the non-intumescent strip 92 or 94 will fill approximately 40% of the gap G. In the Fig. 7 embodiment, the intumescent layer 20 is shown positioned adjacent lo the catalytic converter metal housing 50. However, for some applications, such as low temperature applications, the intumescent layer 20 may be positioned adjacent to the catalyst support element 40. In such an embodiment, the non-intumescent strips 92, 94 may also be positioned adjacent to the catalyst support element 40. A multilayer mat 100 constructed in accordance with a seventh embodiment is illustrated in Fig. 8, where like reference numerals indicate like elements. I he mat 100 comprises an inner non-intumescent layer 13 comprising ceramic fibers and has a width W| defined by opposite lateral edges 14 and 16 and a length L|. I he mat 100 liirlher comprises an intumescent layer 72 comprising intumescent material and has a width W^i defmed by opposite lateral edges 74 and 76 and a length substantially equal lo length F| of the non-intumescent layer 13. In the illustrated embodiment, the width W3 ol'lhe intumescent layer 72 is less than the width Wi of the non-intumescent layer 13. further, Ihe intumescent layer 72 is positioned relative to the non-intumescent layer 13 such that lateral edge 74 is positioned within the two lateral edges 14 and 16 of the non-inlumescenl layer 13 and lateral edge 76 is substantially in-line with lateral edge 16. the multilayer mat 100 further comprises a strip 102 of non-intumescent material. The non-intumescent strip 102 is positioned over a first outer portion 1 8A of ihe non-intumescent layer 13. The non-intumescent strip 102 has a width W4 and a length substantially equal to length Li of the inner non-intumescent layer 13. In tlie illustrated embodiment, the summation of the width W3 of the intumescent layer 72 and the width W.| of the non-intumescent strip 102 is substantially equal to the width Wi of the inner non-intumescent layer 13. In Fig. 9, the mat 100 is shown provided within a metal housing 50 so as lo support and maintain a catalyst support element 40 within the housing 50. Ihe mat 100, housing 50 and support element 40 define a catalytic converter 480. The non-intumescent strip 102 can be Ibrmed from a substantially resilient non-inlumescent material for use in the catalytic converter 480 such that once the mat 100 and the catalyst support element 40 are positioned within the metal housing 50, the strip 102 sufficiently expands in a seal area As of a gap G, between an inner wall of the housing 50 and the support element 40, see Fig. 9, so as to seal the lateral edge 74 of the intumescent layer 72, as the gap G expands with increasing temperatures. In other words, at least the strip 102 is resilient enough to exert a sultlcient pressure to seal the gap G and protect the lateral edge 74 of the intumescent layer 72, whether the gap G is at its smallest (i.e., at aml^ient temperature) or biggest (i.e., at the highest operating temperature). It is desirable for at least the strip 102 to also be durable enough to survive cycling of the gap G lietween its smallest and biggest over the desired life of the pollution control device. It can be preferable for the non-intumescent layer 13 to also exhibit this degree of resilience and durability. Hence, the intumescent layer lateral edge 74 is substantially sealed from direct exposure to high temperature exhaust gases flowing through the catalytic converter 480. It is noted that the inner non-intumescent layer 13 may be formed from a material which is less resilient than the non-intumescent strip 102. For example, the non-intumescent strip 102 may be Ibrmed from one of the same materials, set out above, from which the layer 12 in the Fig. 1 embodiment is formed, fhe intumescent layer 72 may be Ibrmed from one of the same intumescent materials, set out above, From which the intumescent layer 20 in the rig. I embodiment is formed. The non-intumescent layer 13 may be ibrmed from the same non-intumescent material, set out above, from which the non-intumescent layer 13 in the Fig. 4A embodiment is formed. It is noted that in the Fig. 9 embodiment, the lateral edge 76 of the intumescent layer 72 is not sealed by the non-intumescent layer 13. However, because the lateral edge 76 is not positioned in the incoming path of the exhaust gases, loss of intumescent material from lateral edge 76 may be minimal for some catalytic converter designs. In the Fig. 9 embodiment, the intumescent layer 72 is shown positioned adjacent to the catalytic converter metal housing 50. However, for some applications, such as low temperature applications, the intumescent layer 72 may be positioned adjacent to the catalyst support element 40. In such an embodiment, the non-intumescenl strip 102 may also be positioned adjacent to the catalyst support element 40. A multilayer mat 110 constructed in accordance with an eighth embodiment is illustrated in Fig. 10, where like reference numerals indicate like elements. Ihe mat 110 is similar to mat 100 illustrated in Figs. 8 and 9, except that the width W6 of an intumescent layer 112 is less than the width W3 of the intumescent layer 72 in the Fig. 8 embodiment. Ihe intumescent layer 112 has lateral edges 114 and 116, As illustrated in Fig. 10, the intumescent layer 112 defines an outermost layer and is positioned adjacent to the non-intumescent layer 13. The mat 110 is used to support and mount a support element 40 in a metal housing 550 so as to define a catalytic converter 580, see Fig. 10. The metal housing 550 is formed so as to include a recess 550A, which, in the illustrated embodiment, extends circumferentially about the entirety of the housing 550. The housing recess 550A is shaped in X and Z directions so as to receive the intumescent layer 112 and substantially shield the intumescent layer lateral edge 116 from exhaust gases passing through the catalytic converter 580 in a left to right direction as viewed in Fig. 10. 1 lence, the intumescent layer lateral edge 116 is substantially sealed from exposure to high temperature exhaust gases flowing through the catalytic converter 580. As in the Fig. 8 embodiment, the non-intumescent strip 102 is formed from a substantially resilient non-intumescent material for use in the catalytic converter 580 such that once the mat 110, and the catalyst support element 40 are positioned within the metal housing 550, the strip 102 sufficiently expands in a gap between the support element 40 and an inner wall of the housing 550 so as to seal the lateral edge 114 of the intumescent layer 112, as the gap expands with increasing temperatures. In other words, at least the strip 102 is resilient enough to exert a sufticienl pressure to seal the gap (i and protect (he lateral edge 114 of the intumescent layer 112, whether the gap G is at its smallest (i.e., al ambient temperature) or biggest (i.e., at the highest operating temperature). It is desirable for at least the strip 102 to also be durable enough to survive cycling of the gap G l^etween its smallest and biggest over the desired life of the pollution control device. It can be preferable for the non-intumescent layer 13 (o also exhibit this degree of resilience and durability. Hence, the intumescent layer lateral edge 114 is substantially sealed from direct exposure to incoming high temperature exhaust gases flowing through the catalytic converter 580. Ihe intumescent layer 112 may be formed from one of the same intumescent materials, set out above, from which the intumescent layer 20 in the fig. 1 embodiment is formed. The non-intumescent layer 13 may be formed from the same non-intumescent material, set out above, from which the non-intumescent layer 13 in the Fig. 4 A embodiment is formed. The non-intumescent strip 102 may be formed from one of (lie same materials, set out above, from which the layer 12 in the Fig. 1 embodimenl is formed. A multilayer mat 120 constructed in accordance with an ninth embodiment is illustrated in Fig. 11, where like reference numerals indicate like elements. 7 lie mat 120 comprises an inner non-intumescenl layer 13 comprising ceramic fibers and has a widlh Wi defined by opposite lateral edges 14 and 16 and a length Li. The mat 120 further comprises an intumescent layer 112 comprising intumescent material and having a width W6 defined by opposite lateral edges 114 and 116 and a length substantially equal to length L| of the non-intumescent layer 13. In the illustrated embodiment, the width W^ of the intumescent layer 112 is less than the width Wi of the non-intumescent layer 13. Further, the intumescent layer 112 is positioned relative to the non-intumescenl layer 13 such that the lateral edges 114 and 116 are positioned within the two lateral edges 14 and 16 of the non-intumescent layer 13. The multilayer mat 120 further comprises a strip 122 of non-intumescent material. The non-intumescent strip 122 is positioned over an outer portion 18B of the non-intumescent layer 13. The non-intumescent strip 122 has a width W5 and a length substantially equal to the lengths of the inner non-intumescent layer 13 and the intumescent layer 112, In Fig. 12, the mat 120 is shown provided within a metal housing 650 so as to support and maintain a catalyst support element 40 within the housing 650. the mat 120, housing 650 and support element 40 define a catalytic converter 680. Preferably, the non-intumescent strip 122 is formed from a substantially resilient non-intumescent material for use in the catalytic converter 680 such that once the mat 120 and the catalyst support element 40 are positioned within the metal housing 650, the strip 122 sufficiently expands in a gap between the support element 40 and an inner wall of the housing 650 so as to seal the lateral edge 116 of the intumescent layer 112, as the gap expands with increasing temperatures, hi other words, at least the strip 122 is resilient enough to exert a sufficient pressure to seal the gap G and protect the lateral edge 1 16 of the intumescent layer 112, whether the gap G is at its smallest (i.e., at ambient temperature) or biggest (i.e., at the highest operating temperature). It is desirable lor at least the strip 122 to also be durable enough to survive cycling of the gap G between its smallest and biggest over the desired life of the pollution control device. It can be preferable for the non-intumescent layer 13 to also exhibit this degree of resilience and durability. Hence, the intumescent layer lateral edge 116 is substantially sealed from exposure to high temperature exhaust gases flowing through the catalytic converter 680. The metal housing 650 is formed so as to include a recess 650A, which, in the illustrated embodiment, extends about the entirety of the housing 650, see I'ig. 12. Ihe housing recess 650A is shaped in X and Z directions so as to receive the intumescent layer 112 and substantially shield the intumescent layer lateral edge 114 from exhaust gases passing through the catalytic converter 680, Hence, the intumescent layer lateral edge 114 is substantially sealed from direct exposure to incoming high temperature exhaust gases Rowing through the catalytic converter 680. Ihe intumescent layer 112 may be formed from one of the same intumescent materials, set out above, from which the intumescent layer 20 in the Fig. 1 embodiment is formed. The non-intumescent layer 13 may be formed from the same non-intumescent material, set out above, from which the non-intumescent layer 13 in the Fig. 4A embodiment is Ibrmed. Ihe non-intumescent strip 122 may be formed from one of the same materials, set out above, from which the layer 12 in the Fig. 1 embodiment is formed. It is noted that the multilayer mats, set out above, may alternatively lie used to secure a pollution control element such as a filter element within a housing ol an exhaust filter or trap. It is further noted that such pollution control devices, according to the present invention, can be used in the exhaust system of an internal combustion engine (e.g., a vehicle exhaust system, a power generator exhaust system). 1 he multilayer mats are typically tlexible. The mats usually can be handled and wrapped around a pollution control element in a pollution control device without breaking or cracking. When wrapped around a pollution control element, the ends of the multilayer mat can meet in a variety of junctions as discussed in pending U.S. Patent Application Serial Number 10/824,029, entitled "SANDWICH HYBRID MOUNTINCi MAT," and tiled on April 14, 2004, the disclosure of which is incorporated herein by reference. As noted above, the non-intumescent layer 12 and non-intumescenl strips 102 and 122 may be more resilient than the non-intumescent layer 13, Further, the non-intumescent strips 92 and 94 may be more resilient than the non-intumescent layer 13 or vice versa. Hence, the non-intumescent layer 13 may be formed from a material having a different composition from a material used to form the non-intumescent layer 12 and non-intumescent strips 92, 94, 102, 122. Each non-intumescent layer or strip contains inorganic fibers. Any inorganic fiber that is known to be suitable for use in a mounting mat for a pollution control device can be selected. For example, the inorganic fibers can be alumina fibers, mullite fibers, quartz fibers, silicon carbide fibers, silicon nitride fibers, metal fibers, aluminosilicate fibers, magnesium aluminosilicate fibers, aluminoborosilicate tlbers, zirconia fibers, fitania fibers, and the like. The fibers can be amorphous, crystalline, or a combination thereof. Quartz fibers are commercially available under the trade designation "ASFROQUARTZ" from J.P. Stevens, Inc. (Slater, NC). Silicon carbide fibers are commercially available from Nippon Carbon (1 okyo, Japan) under the trade designation 'NICALON" or from Textron Specialty Materials (Lowell, MA) under the trade designation 'lYRANNO". Silicon nitride tlbers are commercially available from loren Hnergy International Corp. (New York, NY). Metal fibers are commercially available from Deckaert (Zweregan, Belgium) under the trade designation ^'BEKl-SIILFD CJI^ 90/C2/4" and from Ribbon Technology Corp. (Gahana, OH) under the trade designation "RIB'IHC". hi some embodiments of the non-intumescent layer(s) or strip(s), the inorganic libers are glass fibers. As used herein, the term '"glass fibers" refers to inorganic libers thai are prepared from an inorganic fusion material that has been cooled without substantial crystallization. The glass fibers are amorphous as determined using cither x-ray diffraction or transmission electron microscopic techniques. The glass fibers, at least in some applications, are shot free (i.e., the fibers contain no greater than 5 weight percent shot, no greater tlian 3 weight percent shot, no greater than 2 weight percent shot, no greater than 1 weight percent shot, or no greater than 0.5 weiglit percent sliot). As used herein, the term ^'shot" refers to non-fibrous particles that can be a by-producl of some inorganic fiber formation processes. Suitable glass fibers are often magnesium aluminosilicate fibers. Such glass fibers can contain at least 50 weight percent Si02, at least 8 weight percent AI^O^, and at least 1 weight percent magnesium oxide. For example, magnesium aluminosilicate fibers can contain 50 to 70 weight percent, 50 to 60 weight percent, 60 to 70 weight percent, or 55 to 65 weight percent Si02; 8 to 30 weight percent, 10 to 20 weight percent, or 20 to 30 weight percent AI2O3; and 1 to 15 weight percent, 1 to 12 weight percent, 1 to 10 weight percent, or 1 to 8 weight percent magnesium oxide. Additional oxides can be present sucl as sodium oxide, potassium oxide, boron oxide, calcium oxide, and the like. Specific examples of magnesium aluminosilicate glass fibers are li-glass fibers, S-glass fibers, S2-glass fibers, and R-glass fibers, li-glass fibers often contain about 55 weight percent Si02, about 11 weight percent AI2O3, about 6 weight percent B2O3, about 18 weight percent CaO, about 5 weight percent MgO, and about 5 weight percent other oxides. S-glass and S2-glass fibers typically contain about 65 weight percent SiOa, about 25 weight percent AI2O3, and about 10 weight t>ercent MgO. R-glass fibers usually contain about 60 weight percent Si02, about 25 weight percent AI2O3, about 9 weight percent CaO, and about 6 weight percent MgO. R-glass fibers, S-glass fibers, and S2-glass fibers are commercially available from Advanced Glassfiber Yarns, IJ.C (Aiken, SC) and Owens-Corning Fiberglass Corp. (Granville, OH), R-glass fibers are commercially available from Saint-Gobain Vetrotex (Herzogenrath, Cjermany). Various refractory ceramic fibers can be used in the non-intumescent layer(s) or strip(s). In some embodiments, the ceramic fibers are amorphous and contain mainly AI2O3 and Si02. Small amounts of other oxides can be present. The weight ratio of ANO to Si02 (AI2O3: Si02) is usually greater than or equal to 20:80, 30:70, 35:65, 40:60, 45:55, 50:50, 55:45, 60:40, or 70:30. The ceramic fibers typically include at least 30 weigiit percent SiOi and at least 20 weight percent AI2O3. For example, suitable ceramic fibers can contain Si02 in an amount of 30 to 80 weight percent and AhO^ in an amount of 20 to 70 weight percent weight percent based on the weight of the fibers. In some specific examples, the ceramic fibers can contain SiOa in an amount of 40 to 60 weight percenl and alumna in an amount of 40 to 60 weight percent based on the weight oflhe fibers. In other specific examples, the ceramic fibers can contain Si02 in an amount of 45 to 55 weight percent and A^O.^ in an amount of 45 to 55 weight percent based on the weight of (he libers. Hxemplary amorphous ceramic fibers that contain mainly Al2()3 and Si()2 include, but are not limited to, those commercially available from Thermal Ceramics (Augusta, GA) under the trade designation "KAOWOOf HA BULK" with 50 weight percent SiO. and 50 weight percent AI2O3 based on the weight of the fibers; from Thermal Ceramics under the trade designation 'CERAFIBHR" with 54 weight percent SiO^ and 46 weight percent Al2()3 based on the weight of the fiber; from Thermal Ceramics under the trade designation ^'KAOWOOL D73F" with 54 weight percent Si02 and 46 weight percent Al2()3 based on the weight of the fiber; from I^ath (Wilmington, DE) under the trade designation ^'RAfH 2300 IIT" with 52 weight percent SiOj, 47 weight percent AhO^, and no greater than 1 weight percent Fe203,1 i02, and other oxides based on the weight oflhe fibers; from Rath under the trade designation "^RATH ALUMINO-SllJCA ff: CII()PRi;i) I'IBHR" with 54 weight percent SiO?, 46 weight percent AI2O3, and no greater than 1 weight percent of other oxides based on the weight of the fiber; from Vesuvius (Buffalo, NY) under the trade designation "CHR-WOOf R1" with 49 to 53 weight percenl Si()2, 43 to 47 weight percent AI2O3, 0,7 to f 2 weight percent Fe203, f 5 to 1.9 weight percenl Ti()2, and no greater than 1 weight percent other oxides based on the weight of the fibers; from Vesuvius under the trade designation ^X^ER-WOOL LT" with 49 to 57 weight percent Si02, 38 to 47 weight percent AI2O3, 0.7 to 1.5 weight percent Fe203, 1.6 to 1.9 weight percent 1102, and 0 to 0.5 weight percent other oxides leased on the weight of the (ibers; and from Vesuvius under the trade designation 'CKR-WOOE I IP" with 50 to 54 weight percent Si02, 44 to 49 weight percent AI2O3, 0 to 0.2 weight percent 1 e203, 0 to 0.1 weight percent Ti02, and no greater than 0.5 weight percent other oxides based on the weiglit of the fibers. In other embodiments, the ceramic fibers are amorphous and contain mainly Si()2, AhOu and ZrOi- Small amounts of other oxides can be present, The weight ratio of AI2O3 to Si02 (AI2O3: Si02) is greater than or equal to 20:80, 30:70, 35:65, 40:60. 45:55, 50:50, 55:45, 60:40, or 70:30. The fibers contain at least 3 weight percent /r()2, at least 30 weight percent SiOa, and at least 20 weight percent AI2O3 based on the weight of the fiber. In some embodiments, the fibers contain Zr()2 in an amount up to 5 weight percent, up to 7 weight percent, up to 10 weight percent, up to 12 weight percent, up to 15 weight percent, up to 16 weight percent, up to 20, or up to 25 weight percent based on the weight of the libers. The ceramic fibers can contain Si02 in an amount of 30 to 70, 40 to 65, 45 to 60, 45 to 55, or 50 to 60 weight percent based on the weight of tlie libers. The ceramic libers can contain AI2O3 in an amount of 20 to 60, 25 to 50, 25 to 45, 25 to 40, 25 to 35, 30 to 50, or 30 to 40 weight percent based on the weight of the libers. In some specific examples, the ceramic fibers contain 25 to 50 weight percent AI2O3, 40 to 60 weight percent Si02, and 3 to 20 weight percent Zr02 based on the weight of tlie libers. In other specific examples, the ceramic fibers contain 30 to 40 weight percent AhOj, 45 to 60 weight percent Si02, and 5 to 20 weight percent Zr02 based on the weight of the fibers. Exemplary amorphous ceramic fibers that contain SiCh, AI2O3, and Zr()> are commercially available from Thermal Ceramics (Augusta, GA) under the trade designation '^KAOWOOL ZR" and ^^CHRACMKM" with 50 weight percent Si()2, 35 weight percent AI2O3, and 15 weight percent Zr()2 based on the weight of the liber; from Unifrax (Tonawonda, NY) under the trade designation "UNIFRAX FIBHRFRAX FltiFRMA I" with 52 to 57 weight percent Si02, 29 to 47 weight percent Al2()3, and no greater than 18 weight percent Zr02 based on the weight of the fibers; from Unifrax under the trade designation "UNIFRAX FIBERFRAX DURABACK" with 50 to 54 weight percent Si02, 31 to 35 weight percent AI2O3, 5 weight percent Zr02, 1 -3 weight percent Fe203, 1J weight percent ^f i02, 0.5 weight percent MgO, and no greater than 7 weight percent CaO based on the weight of the fibers; from Rath (Wilmington, DF) under the trade designation "RATH 2600 IITZ" with 48 weight percent Si02, 37 weight percent AI2O3, 15 weight percent Zr02, and no greater than 1 weight percent other oxides based on the weight of the libers; and from Vesuvius (Buffalo, NY) under the trade designation "CRIl-WOOL HTZ" with 44 to 51 weight percent SiOi, 33 to 37 weight percent AUOu 13 to 19 weight percent Zr02, 0.1 to 0,6 weight percent 1^6263, 0,1 to 0.6 weight percent riO>, and no greater than 1 weight percent other oxides based on the weight of the ilbers. ]n some embodiments of the non-intumescenl layer(s) or slrip(s), the ceramic fibers have a bulk shrinkage no greater than 10 percent, no greater than 8 percent, no greater than 6 percent, no greater than 4 percent, no greater than 3 percent, no greater than 2 percent, or no greater than 1 percent using the I hernial Mechanical Analyzer (T MA) test. The ceramic fibers typically shrink at least 0,5 percent. In some embodiments, (he ceramic fibers have a bulk shrinkage of 0.5 to 2 percent, 0.5 to 3 percent, 0.5 to 5 perceni, or 0.5 to 6 percent. In the rMA test, a sample under a load (e.g., 50 psi or 345 N/m~) is heated to 1000 '*C and then cooled. The caliper oi the sample can be measured during both the heating and cooling cycles at 750 **C to calculate percent shrinkage. 1 he percent shrinkage is equal to the difference in the caliper at 750 "C during the heating and cooling step multiplied by 100 and divided by the caliper at 750 "C during the heating step. The IMA test can be used to characterize the ceramic fibers or an non-intumescent layer prepared Irom ceramic fibers. Most or all of the organic materials that may be present in a non-intumescent layer are removed by time the temperature of the thermal Mechanical Analyzer reaches 750 **C, lixamples of ceramic fibers having a bulk shrinkage no greater than 10 percent as supplied (i.e., the fibers can be used as supplied without a heat-treatment) include, hut are not limited to, fibers that are crystalline and that contain both AI2O3 and Si02. The weight ratio of AI2O3 to Si02 (AI2O3: Si02) can be greater than or equal to 60:40, 65:35, 70:30, 72:28, 75:25, 80:20, 90:10, 95:5, 96:4, 97:3, or 98:2. In some specific examples, the ceramic fibers contain 60 to 98 weight percent AI2O3 and 2 to 40 weight percent Si02 based on the weight of the fibers, hi other specific examples, the ceramic fibers contain 70 to 98 weight percent AI2O3 and 2 to 30 weight percent Si02 based on the weight ol'the fibers. Traces of other oxides can be present. As used herein, the term 'trace" refers to an amount no greater than 2 weight percent, no greater than 1 weight percent, or no greater than 0.5 weight percent. Suitable ceramic fibers that are crystalline and have a bulk shrinkage no greater than 10 percent include, but are not limited, to those commercially available Irom Mitsubishi Chemical (1 okyo, Japan) under the trade designation 'MAM l^C" (e.g., MLSK M1.S2, and MLS3) with 28 weight percent Si02 and 72 weight percent AI2O3 based on the weight of the fibers; fiom Saffil Limited (Widness Cheshire, LJX.) under the trade designation "SAFFIL'^ (e.g., SF, LA Bulk, llA Bulk, HX Bulk) with 3 lo 5 weight perceni Si02 and 95 lo about 97 weight percent ANO^ based on the weight ol the libers; and from I Jnilrax (Tonawonda, NY) under the trade designation "UNIFRAX FIBHRFRAX FIBERMAX" with 27 weight percent Si02 and 72 weight percent ALO^ based on the weight of the fibers. Further examples of ceramic fibers that are crystalline and have a bulk shrinkage no greater than 10 percent as supplied are aluminoborosilicate fibers. These fibers typically contain AI2O3 in an amount of at least 50 weight percent, Si02 in an amount no greater than 50 weight percent, and B2O3 in an amount no greater than 25 weight percent based on the weight of the fibers. Some specitic aluminoborosilicate fibers contain 50 lo 75 weight percent AI2O3, 25 to 50 weight percent Si02, and 1 to 25 weight percent B2O3 based on the weight of the fibers. Such aluminoborosilicate fibers are commercially available under the trade designation ^^NHXTFiL 312" and "NEXTLL 440" from 3M Company (St, Paul, MN). At least some of these ceramic fibers that are crystalline and that have a bulk shrinkage no greater than 10 percent as supplied by the manufacturer are prepared using a sol-gel process. In a sol-gel process, the ceramic libers are formed by spinning or extruding a solution, dispersion, or viscous concentrate. The sol-gel process, which is further described in U.S. Patent No. 3,760,049 (Borer et al.), can include extrusion of the solution, dispersion, or concentrate through orifices to form green fibers that are then fired to form ceramic fibers. The solution, dispersion, or concentrate contains the t)xides or tlie precursors to the oxides that are in the fibers. In some embodiments, commercially available amorphous ceramic tlbers can be heat-treated to provide ceramic fibers that have a bulk shrinkage no greater than 10 percent. The ceramic fibers that can be heat-treated to provide fibers having a bulk shrinkage no greater than 10 percent typically are melt-blown or melt-spun from a mixture of AI2O3 and SiOi or a mixture of AI2O3 and Si02 with other oxides such as B2O3, P2O5, or Zr02. t^xemplary amorphous ceramic fibers that can be heat-treated include, but are not limited to, ceramic fibers commercially available from Thermal Ceramics (Augusta, (JA) under the trade designation 'KAOWOOL HA BULK", "CERA! IBER", ^^KAOWOOL D73F", "KAOWOOL ZR", or ^^CERACHEM"; from Rath (Wihnlnglon, DE) under the trade designation '"RATH 2300 RT", ^^RATH ALUMINO-SILICIAI li CHOPPED FIBER", or "RATH 2600 HTZ"; from Vesuvius (Bufl^lo, NY) under the trade designation ^^CER-WOOL RT", ^^CER-WOOL LT", or "CER-WOOL IITZ", or "CER-WOOL HP"; and from Unifrax (Tonawonda, NY) under the trade designation 'UNU RAX I'lBERl RAX FIBERMAT" or 'TJNIFRAX FIBERFRAX DURABACK". The ceramic fibers tend to devilrily (i.e., change, at least in part, from an amorphous state into a microcrystalline or crystalhne state) during the heat-treatment process. Usually, only a portion of the individual ceramic fiber undergoes devitrification. Ihat is, after heat-treatment, the individual ceramic fibers contain amorphous material as well as crystalline material, microcrystalline material, or a combination of crystalline and microcrystalline material. Techniques such as transmission electron microscopy and x-ray diffraction can be used to characterize the amorphous, crystalline, or microcrystalline nature of inorganic fibers. As used herein, the term '"amorphous" refers to inorganic Fibers that are Iree of crystalline or microcrystalline regions. If the inorganic tlbers are amorphous, no diffraction peaks (i.e., no diffraction pattern) can be detected using either transmission electron microscopy or x-ray diffraction. If the inorganic fiber contains regions having a small crystalline size (i.e., microcrystalline), diffraction peaks (i.e., a diffraction pattern) can be detected using transmission electron microscopy but not using x-ray diffraction. As used herein, the term "microcrystalline" refers to inorganic fibers that have at least some regions with a crystalline character and that have a crystal size detectable with transmission electron microscopy but not with x-ray diffraction. If the inorganic fibers contain regions having a larger crystalline size (i.e., crystalline), a diffraction pattern can be obtained using x-ray diffraction. As used herein, the term 'crystalline" refers to inorganic fibers that have at least some regions with a crystalline character and that have a crystal size detectable with x-ray diffraction. M he smallest crystal sizes detectable using x-ray diffraction typically results in a broad diffraction pattern without well-defined peaks. Narrower peaks indicate a larger crystalline size. The width of the diffraction peaks can be used to determine the crystalline size. The inorganic fibers that are crystalline are usually polycrystalline rather than being single crystals. In some applications, the ceramic fibers are heat-treated at a temperature of at least 700 'C. For example, the ceramic fibers can be heat-treated at a temperature of at least 800 X% at a temperature of at least 900 X\ at a temperature of at least 1000 "C, or at a temperature of at least 1100 "C, Suitable heat-treatment temperatures can vary depending on the composition of the ceramic fibers and the time the ceramic fibers are held at the heat-treatment temperature. Suitable heat-treatment methods and suitable heat-treated ceramic fibers are further described, for example, in hiternational Patent Application WO 99/46028 (Fernando et al.) and U.S. Patent No. 5,250,269 (Langer), the disclosure of which are incorporated herein by reference. There is a time-temperature relationship associated with the size of crystals or microcrystals that form during the heat-treatment process. For example, the ceramic fibers can be heat-treated at lower temperatures for longer periods of time or at higher temperatures for shorter periods of time to produce a comparable state of crystallinity or microcrystallinity. The time at the heat-treatment temperature can be up to 1 hour, up to 40 minutes, up to 30 minutes, up to 20 minutes, up to 10 minutes, up to 5 minule, up to 3 minutes, or up to 2 minutes. For example, the heat-treatment temperature can be chosen to use a relatively short heat-treatment time such as up to 10 minutes. Oi' 1 Ihe temperature of the heat-treatment can be chosen to be at least 20 'X\ at least 30 \.\ at least 40 T, at least 50 "C, at lest 60 T\ at least 70 "C, at least 80 "C, at least 90 X\ or at least 100 '*C above the devitrification temperature (i,e., the temperature at which the ceramic libers change from being an amorphous material to being a microcrystalline or crystalline material). Suitable heat-treatment times and temperatures lor the ceramic fibers can be determined using techniques such as, for example. Differential 1 hernial Analysis (DTA). The temperature for Al203-Si02 ilbers is typically in the range ol 700 *'( to 1200 ^*C, in the range of 800 'C to 1200 ^'C, in the range of 900 X: to 1200 X\ or in the range of 950 \: to 1200 T. A ceramic fiber that is completely amorphous usually shrinks more than ceramic liber that contain regions that are microcrystalline, crystalline, or a combination thereof. Ceramic libers that are at least partially crystalline or microcrystalline can be fabricated into mounting mats that can be repeatedly heated to a temperature suitable for use in a pollution control device and then cooled. Microcrystalline or crystalline ceramic libers tend to be resistant to further shrinkage that could negatively impact the performance of the non-intumescent layer. I'or ceramic fibers that are subjected lo heat-treatment, the brittleness ottlie (ibcrs can he balanced with the low bulk shrinkage characteristics. Crystalline or microcrystalline ceramic fibers tend to be more brittle than amorphous ceramic libers. Non-intumescent layers made from crystalline or microcrystalline ceramic fibers can break more easily than insulation prepared from amorphous fibers. On the other hand, crystalline or microcrystalline ceramic fibers tend to have a lower bulk shrinkage than amorphous ceramic fibers. rhe average diameter of the inorganic fibers is typically at least 3 micrometers, ai least 4 micrometers, at least 5 micrometers, at least 6 micrometers, or at least 7 micrometers, fhe inorganic fibers usually have an average diameter that is no greater than 20 micrometers, no greater than 18 micrometers, no greater than 16 micrometers, or no greater than 14 micrometers. In some embodiments, at least 60 weight percent of the inorganic fibers have an average diameter that is within 3 micrometers of the average diameter. Vox example, at least 70 weight percent, at least 80 weight percent, or at least 90 weight percent ol the inorganic fibers have an average diameter that is within 3 micrometers of the average diameter. The non-intumescent layer(s) or strip(s) can further contain an organic binder in amounts up to 20 weight percent based on the weight of the non-intumescent layer. In some embodiments, the organic binder is present in amounts up to 10 weight percent, up to 5 weight percent, or up to 3 weight percent based on the weight of the non-intumescent layer or strip, fhe organic binder is typically burned off when the multilayer mat containing the non-intumescent layer or strip is used at elevated temperatures such as those typically encountered in a pollution control device. Suitable organic binder materials can include aqueous polymer emulsions, solvent-based polymers, and solvent free polymers, [he aqueous polymer emulsions can include organic binder polymers and elastomers in the form of a latex (e.g., natural rubber lattices, styrene-butadiene lattices, butadiene-aciylonitrile lattices, and lattices of acrylate and melhacryiale polymers or copolymers). The solvent-based polymeric binder materials can include a polymer such as an aciylic, a polyurethane, a vinyl acetate, a cellulose, or a rubber based organic polymer. The solvent free polymers can include natural rubber, styrene-butadiene rubber, and other elastomers. In some embodiments, the organic binder material includes an aqueous acrylic emulsion. Acrylic emulsions advantageously tend to have good aging properties and non-corrosive combustion products. Suitable acrylic emulsions can include, but are not limited to, commercially available products such as those sold under the trade designation '^RI lOPLHX 1 R-934" (an aqueous acrylic emulsion having 44.5 weight percent solids) and "'RHOPLRX HA-8" (an aqueous emulsion of acrylic copolymers having 45.5 weight percent solids) from Rohm and Ilass (Philadelphia, PA); under the trade designation 'NliOCRYL XA-2022" (an aqueous dispersion of an acrylic resins having 60.5 percent solids) available from ICI Resins US (Wilmington, MA); and under the trade designation '^AlRfMlX 60()BP DEV" (an aqueous emulsion of ethylene vinyl acrylate terpolymer having 55 weight percent solids) from Air Products and Chemical, Inc. (Philadelphia, PA). Organic binders can also include a plasticizer, a tackifier, or a combination thereof. Plasticizers tend to soften a polymer matrix and can enhance the flexibility and moldability of the non-intumescent layer. For example, the organic binder can include a plasticizer such as isodecyl diphenyl diphosphate commercially available under the trade designation ^^SANTICIZER 148" from Monsanto (St. Louis, MO). lackifiers or tackiiying resins can aid in holding the insulation material together. An example of a suitable tackifier is commercially available from Bka Nobel, Inc. (loronto, Canada) under the trade designation "SNOW! ACK 810A". rhe non-intumescent layer(s) or strip(s) can also contain other materials such as, but not limited to, plasticizers, wetting agents, dispersants, defoaming agents, latex coagulants, and fungicides. Filler materials such as glass particles, calcium carbonate, expanded vermiculite, delaminated vermiculite, mica, perlite, aluminum trihydrate, magnesium phosphate hexahydrate, zinc borate, and magnesium hydroxide can be added. Additionally, inorganic binders such as clays, bentonite, and colloidal silica can be added. The non-intumescent layer(s) or strip(s) can also contain organic fibers such as, tor example, acrylics, cellulose, polyolefin, polyvinyl alcohol, polyester, or combinations thereof The fibers can be staple fibers or fibrillated fibers. Useful stable fibers typically have a size of about 0.5 to 5 denier. Suitable rayon fibers having a size of 1.5 denier per filament are commercially available from Minifiber, Inc. (Johnson City, TX). Suitable polyvinyl alcohol fibers are commercially available from Kuraray Americas, Inc. (New York, NY) under the trade designation 'KURALON". An acrylic tlber pulp is commercially available under the trade designation '"CFF" from Cytek Industries, inc. (West Paterson, NJ). A suitable non-intumescent layer or strip can include, at least in some embodiments, inorganic fibers in an amount of 10 to 99.5 weight percent and organic binders in an amount of 0.5 to 20 weight percent. For example, the non-intumescenl layer or strip can contain inorganic fibers in an amount of 20 to 99.5 weight percent, organic binder in an amount of 0.5 to 20 weight percent, and up to 60 weight percent inorganic binders or tillers. One non-intumescent layer thai can be used according to the present invention contains heat-treated aluminosilicate ceramic ilbers is commercially available iVom 3M Company (St. Paul, MN) under the trade designation ^MNTERAM 900111". This mat has a bulk density of about 0.25 g/cm^ and a weight per unit area of about 1020 to about 2455 g/m^. Other more resilient non-intumescent layer(s) or strip(s) include those commercially available from 3M Company under the trade designation "INTFRAM 11001 IT" and ^iN IHRAM 11 Oil \T\ These mats have a bulk density of about 0.15 g/cnr^ and a weight per unit area of about 440 to about 2100 g/m^. fhese mats contain crystalline alumina fibers (i.e., polycrystalline alumina fibers). Another suitable non-intumescent layer that includes magnesium aluminosilicate glass fibers is commercially available from 3M Company under the trade designation 'MNPF 571.02." This mat has a bulk density of 0.12 g/cm^ and a weight per unit area of about 600 to about 1400 g/m". A needle-bonded mat is commercially available from Mitsubishi Chemical Company, Tokyo, japan under the trade designation "MAFTEC MLS-3" with a bulk density of about 0.16 g/cnY\ This mat contains about 72 weight percent AI2O3 and about 28 weight percent Si02 based on the weight of the fibers. The intumescent layers contains at least one type of intumescent material, 'ilie intumescent layers can further include inorganic fibers, organic binders, plaslicizers, wetting agents, dispersants, defoaming agents, latex coagulants, fungicides, filler materials, inorganic binders, and organic fibers. These additional components are the same as those discussed above for the non-intumescent layer. Kxamples of suitable intumescent materials for the intumescent Uiyer include unexpanded vermiculite, hydrobiotite, water swellable synthetic tetrasilicic lluorine type mica as described in U.S. Pat. No. 3,001,571 (Match), alkali metal silicate granules as described in U.S. Pat. No. 4,521,333 (Graham et al.), expandable graphite, or combinations thereof. Alkaline metal silicate granules are commercially available from 3M Company (St. Paul, MN) under the trade designation "EXPAN I ROL 4BW". Hxpandable graphite is commercially available under the trade designation ^'GRAfOII. (jRADE 338-50" from UCAR Carbon Co., Inc. (Cleveland, OH). Unexpanded vermiculite is commercially available from Cometals Inc. (New York, NY). In some applications, the intumescent materials are selected from unexpanded vermiculite, expandable graphite, or a combination thereof. Ihe vermiculite can be treated, for example, with salts such as ammonium dihydrogen phosphate, ammonium nitrate, ammonium chloride, potassium chloride, or other soluble salts known in the art. The treatment is based on an ion exchange reaction. The intumescent layer often contain at least 5, at least 10, at least 20, at least 40, or at least 60 weight percent intumescent material based on the weight of the intumescent layer. In some intumescent layers, the layer can be free of inorganic fibers. In other intumescent layers, the layer can be free of inorganic fibers and organic binders. In still other intumescent layers, the layer contains 5 to about 85 weight percent intumescent material and less than 20 weight percent organic binder based on the weight oflhe intumescent layer. Inorganic fibers are included in some intumescent layers. In some more specific example, the intumescent layer includes intumescent materials in an amount of 5 to 85 weight percent, organic binder in an amount of 0.5 to 15 weight percent, and inorganic fibers in an amount of 10 to 60 weight percent based on the weight of the intumescent layer. In other examples, the intumescent layer includes intumescent materials in an amount of 5 to 70 weight percent, organic binder in an amount of 0,5 to 10 percent, and inorganic fibers in an amount of 30 to 45 weight percent based on the weight of the intumescent layer. In still other examples, the inlumescent layer includes intumescent materials in an amount of 20 to 65 weight percent, organic binders in an amount of 0.5 to 20 weight percent, inorganic fibers in an amount of 10 to 65 weight percent, and up to 40 weight percent inorganic fillers or inorganic binders. Suitable intumescent layers are commercially available (rom 3M (Si, Paul, MN) uiuler Ihe trade designations "INTERAM 100", 'iNTERAM 200", "IN TERAM 550", and "IN lERAM 2000 ET". These mats usually have a bulk density of about 0.4 to about 0.7 g/cm and a weight per unh area of about 1050 g/m' to about 8140 g/m~. Another suitable intumescent layer is commercially available from 3M under the trade designation ^iN fF-RAM 570NC". This layer usually has a weight per unit area of about 1050 g/nr to aboiit 4070 g/m^ and contains inorganic fibers that that meet European non-classified liber regulations. In some intumescent layers, biosoluble inorganic fibers are included. Intumescent layers containing biosoluble fibers are further described in International Patent Application Publication WO 03/031368 (lloworth), incorporated herein by relerence in its entirety. As used herein, 'biosoluble inorganic fibers" refer to inorganic fibers that are decomposable in a physiological medium or a simulated physiological medium. Physiological medium refers to, but is not limited to, those bodily fiuids typically found in the respiratory tract such as, for example, the lungs of animals or humans. The biosoluble inorganic fibers typically include inorganic oxides such as, for example, Na20, K2O, CaO, MgO, P2O5, Ei20, and BaO, or combinations thereof wilh silica. Other metal oxides or other ceramic constituents can be included in the biosoluble inorganic fibers even though these constituents, by themselves, lack the desired solubility but are present in low enough quantities such that the fibers, as a whole, are still decomposable in a physiological medium. Such metal oxides include, for example, AI2O3, TiOi, ZrOa, B2O3, and iron oxides. The biosoluble inorganic fibers can also include metallic components in amounts such that the fibers are decomposable in a physiological medium or simulated physiological medium. In one embodiment, the biosoluble inorganic fibers include silica, magnesium oxide, and calcium oxide. These types of fibers are typically referred to as calcium magnesium silicate fibers. The calcium magnesium silicate fibers usually contain less than about 10 weight percent aluminum oxide. Suitable biosoluble fibers can include 45 to 90 weight percent Si02, up to 45 weight percent CaO, up to 35 weight percent MgO, and less than 10 weight percent AI2O3. For example, the fibers can contain about 55 to about 75 weight percent Si02, about 25 to about 45 weight percent CaO, about 1 to about 10 weight percent MgO, and less than about 5 weight percent AI2O3. lixemplary biosoluble inorganic oxides fibers are described in U.S. Patent Nos. 5,332,699 (Olds et a!.); 5,585,312 (Tenl^yck et ah); 5,714,421 (Olds et al.); and 5,874,375 (Zoitas et al.). Various methods can be used to form biosoluble inorganic fibers including, but not limited to, sol gel formation, crystal growing processes, and melt forming techniques such as spinning or blowing. Biosoluble libers are commercially available from IJnifrax Corporation (Niagara Falls, NY) under the trade designation "INSLJLFRAX". Other biosoluble fibers are sold by Thermal Ceramics (located in Augusta, GA) under the trade designation ^^SUPERWOOL." For example, SUPERWOOL 607 contains 60 to 70 weight percent Si()2, 25 to 35 weight percent CaO, 4 to 7 weight percent MgO, and a trace amount of AhO^- SUPERWOOL 607 MAX can be used at a slightly higher temperalure and contains 60 to 70 weight percent SiOi, 16 to 22 weight percent CaO, 12 \o 19 weight percent MgO, and a trace amount of AI2O3. An exemplary intumescent layer can include intumescent material in an amount of 10 to HO weight percent, biosoluble inorganic fibers in an amount of 5 to 80 weight percent, micaceous binder in an amount o( 5 to 80 weight percent, and organic binder in an amount ol 0.5 to 20 weight percent. As used herein, "micaceous binder" refers to one or more micaceous minerals that can be wetted and then dried to form a cohesive body that is sell-supporting. As used herein, "self-supporting" refers to a micaceous binder that can be formed into a 5 cm x 5 cm X 3 mm sheet containing no other materials such that the dried sheet can be held horizontally at any edge for at least 5 minutes al 25 ^C and up to 50 percent relative humidity without crumbling or otherwise falling apart. As used herein, the phrase "micaceous mineral" refers to a family of minerals that can be split or otherwise separated into planar sheets or platelets. Micaceous minerals include, but are not limited to, expanded vermiculite, unexpanded vermiculite, and mica. Micaceous minerals typically have an average aspect ratio (i.e., the length of a particle divided by its thickness) that is greater than about 3. Micaceous minerals that typically have a particle size less than about 150 micrometers (e.g,, the micaceous binder contains micaceous minerals that can pass through a 100 mesh screen). In some embodiments, the micaceous binder contains micaceous minerals having a size less than about 150 micrometers and having an average aspect ratio of greater than about 8 or greater than about U). Suitable micaceous binders can include micaceous minerals that have been crushed. As used herein, 'crushed" refers to micaceous minerals that have been processed in any suitable manner that reduces the average particle size. Methods of crushing include, but are not limited to, mechanical shearing of a dilute or concentrated slurry, milling, air impact, and rolling. Other methods can be used alone or in combination wilh crushing to reduce the particle size. For example, thermal or chemical methods can be used to expand or expand plus exfoliate the micaceous minerals. Expanded vermiculite can be sheared or otherwise processed in water to produce an aqueous dispersion of delaminated vermiculite particles or platelets. Shearing can be adequately performed, for example, using a high shear mixer such as a blender. In some embodiments, the micaceous binder includes processed vermiculiles (i.e., vcrmiculate that has been expanded, delaminated, and crushed). Processed vermiculile is typically non-inlumescent. In other embodiments, the micaceous binder includes vermiculite that has not been expanded and delaminated or that has been only partially expanded and delaminated. Such materials tend to be intumescent. Suitable micaceous binders are commercially available irom W. R. Grace & Company, and include a delaminated vermiculite powder (under the trade designation 'VFPS") and an aqueous dispersion of chemically exfoliated vermiculite (under the trade designation 'MICROLITE). Also, expanded vermiculite flakes are available from W.R. Grace and Company (under the trade designation 'ZONELIIE #5") that can be reduced in particle size to form a micaceous binder. The micaceous binder can include vermiculite having a particle size less than about 150 micrometers and the intumescent material can include vermiculile having a particle size greater than about 150 micrometers (none passes through a 100 mesh screen). I he intumescent vermiculite can have an average particle size that is greater than about 300 micrometers. In one embodiment of a multilayer mat, the non-intumescent layer(s) or slrip(s) contains glass fibers and the intumescent layer(s) contain vermiculite. In another embodiment of the multilayer mat, the non-intumescent layer(s) or strip(s) contains reiVactory ceramic fibers having a shrinkage no greater than 10 percent based on the IMA test and the intumescent layer(s) contain vermiculite. Each non-intumescent layer or strip in the multilayer mat usually has a bulk density in the range of about 0.05 g/cnv^ to about 0.4 g/cm^ while the intumescent layer has a bulk density in the range of about 0.4 g/cm^ to about 0.75 g/cm\ As used herein, the term 'bulk density" refers to the density of a layer, strip or multilayer mat that is not under compression. The bulk density ol the multilayer mat depends on the thickness and composition of the various layers but is typically about 0.2 g/cm^ to about 0.5 g/cm*. In some applications, the multilayer mats have a compressed density of about 0.4 g/cnv^ to about 0.9 g/cm\ As used herein, the term '^compressed density" refers to the density of the multilayer mat after being assembled around a pollution control element in a pollution control device. A paper making process is used to form the non-intumescent layer(s), strip(s), the intumescent layer(s), or a combination thereof. For example, a non-intumescent layer(s) or strip(s) can be prepared by forming an aqueous slurry containing the inorganic libers. The aqueous slurry often contains up to 30 weight percent solids based on the weight of the slurry (e.g., the slurry can contain up to 20 weight percent or up to 10 weight percent solids based on the weight of the slurry). The slurry often contains at least 1 percent solids based on the weight of the slurry (e.g., slurry can contain at least 2 weight percent or at least 3 weight percent solids). In some embodiments, the slurry can contain 1 to 10, 2 to 8, or 3 to 6 weight percent solids. Higher solids can be advantageous because less water needs to be removed to prepare the preform. However, slurries with higher percent solids tend to be more difficult to mix. The intumescent layer can be prepared by forming an aqueous slurry containing the intumescent material. The percent solids can be comparable to those used to prepare the non-intumescent layer. The aqueous slurry for the intumescent layer often contains inorganic fibers however intumescent layers can be free of inorganic fibers. The water used in each aqueous slurry can be well water, surface water, or water that has been treated to remove impurities such as salts and organic compounds. When well or surface water is used in the aqueous slurry, salts (e.g., calcium and magnesium salts) present in the water can function as an inorganic binder. In some embodiments, the water is deionized water, distilled water, or a combination thereof. Other additives can also be included in each aqueous slurry composition. Such additives can include inorganic binders, inorganic fillers, defoamers, llocculants, surfactants, and the like. Strength enhancing agents can also be included such as, for example, organic fibers. Other methods can be used to prepare the non-intumescent layer(s) or sli ip(s). In some applications, the non-intumescent layer or strip can be prepared as a non-woven mat by chopping individual inorganic fibers to a desired length. Such a method is described in International Patent Application Publication WO 2004/011785 (Merry et ah), incorporated herein by reference. '1 he individualized fibers can be prepared by chopping a tow or yarn o( fiber using a glass roving cutter commercially available under the trade designation ^^MODEL 90 GLASS ROVING CUTTER" from Finn and Pram, Inc. (Pacoma, CA). Allernatively, the chopped individualized fibers can be formed using a hammer mill and then a blower. The fibers are usually chopped to a length ranging from about 0.5 to about 15 cm. A mat can be formed using a conventional web forming machine such as those commercially available from Rando Machine Corp. (Macedon, NY) under the trade designation "RANDO WEBBER" or from ScanWeb Co. (Denmark) under the trade designation 'DAN WEB". The chopped individualized fibers can be drawn onto a wire screen or mesh bell (e.g., a metal or nylon belt). Depending on the length of the fibers, the resulting mat can have sufficient handleability to be transferred to a needle punch or stitch bonding machine without a support such as a scrim. To facilitate ease of handing, some mats can be formed or placed on a scrim. A needle-punched nonwoven mat refers to a mat where there is physical entanglement of the inorganic fibers provided by multiple full or partial penetrations of the mat with barbed needles. Needle punching generally involves compressing a nonwoven mat and then punching and drawing barbed needles through the mat. Although the optimum number of needle punches per area of mat depends on the particular application, the nonwoven mat is often punched to provide about 5 to about 60 punches/cm". In some applications the mats have 10 to about 20 punches/cm . The nonwoven mat can be needle punched using a conventional needle punching machine such as those commercially available from Dilo (Germany) with barbed needles commercially available from Poster Needle Company (Manitowoc, WI). Alternatively, the nonwoven mat can be stitch bonded using techniques such as those disclosed in U.S. Patent No. 4,181,514 (Letkowitz et al.), the disclosure ofwhich is incorporated herein by reference. The mat can be stitch bonded using an organic thread or an inorganic thread (e.g., ceramic or stainless steel). A relatively thin layer of inorganic or organic sheet material can be placed on either or both sides of the mat during stitching to prevent or minimize the threads from cutting through the mat. Ihe spacing of the stitches can be varied but is usually about 3 to about 30 mm so thai the fibers are uniformly compressed throughout the entire area of the mat. A commercially available needle punched non-intumescent layer can be obtained from Mitsubishi Chemical (Tokyo, Japan) under the trade designation 'MAFTEC". I he intumescent layer can be in the form of a paste applied to a major surface ol a non-inlumescent layer. Suitable paste compositions for intumescent layers are further described, for example, in U.S. Patent Nos. 5,853,675 (Howorth) and 5,207,989 (MacNeil), incorporated herein by reference. Some of these compositions include inorganic fibers in addition to the intumescent material. The pastes can be applied initially, for example, to a substrate such as a release liner or paper, fhe subshate can be removed after contacting the paste with a major surface of a non-intumescenl layer. In other multilayer mats, the intumescent layer can be Ibrmed by spraying a suitable intumescent composition onto a major surface of a non-intumescent layer. I he compositions can include, for example, other materials such as inorganic fibers or organic binders. Alternatively, intumescent material free of a binder can be applied to a portion of a major surface of a non-intumescent layer. ihe various layers can be individually prepared and tlien bonded together, fhe various layers of the multilayer mat can be bonded to each other using needle punching or stitch bonding techniques. Some of the multilayer mats have an adhesive to adhere the non-intumescent and intumescent layers together. Each layer can be prepared separately and then bonded together. The adhesive can be a pressure sensitive adhesive or a hot melt adhesive. In some multilayer mats, the adhesive is a hot melt adhesive such as, for example, the adhesive commercially available from Bostik-Findley (Stafford, UK) under the trade designation 'TE 105-50" or ^TE 65-50". fhe multilayer mat can be prepared using a paper making process. One such process is described in U.S. Patent Publication 2001/0046456 (Eanger et al.), the lisclosure oi which is incorporated herein by reference. A first slurry containing inorganic fibers can be prepared and then deposited on a permeable substrate. The deposited first slurry can be partially dewatered to form a first layer. An inlumescent composition can be applied to a portion oi the first layer to form a second layer. The inlumescent composition can be applied, for example, by spraying if the composition includes a liquid or by sprinkling if the composition is free of a liquid. A second slurry containing inorganic fibers can be prepared and then deposited on over the second layer and any exposed first layer. The deposited third slurry can be at least partially dewatered to ibrm a third layer. After the final layer has been deposited, the mat can be dried to remove at least a portion of any remaining water. For example, the mat can be compressed and dried by passing the mat through heated rollers Such a process can result in some intermingling of the layers. Ihe intermingling o the layers can be practically invisible to the eye or can be to such an extent that a visible boundary or gradient layer forms between two adjacent layers. With such a process, the layers can be bonded together without the use of an adhesive, stitches, needles, or staples. The Ibregoing describes the invention in terms of embodiments jbreseen by the inventor for which an enabling description was available, notwithstanding that insubstantial modifications of the invention, not presently foreseen, may nonetheless represent equivalents thereto. What is claimed is: 1. A multilayer mat for mounting a pollution control element in a pollution ccM^lrol device, said mat comprising: at least one non-intumescent layer comprising ceramic fibers and having a width delined liy opposite lateral edges; and at least one intumescent layer comprising an intumescent material and having a width delined l:>y opposite lateral edges, wherein the width of said intumescent layer is less than the width of said non-intumescent layer and said intumescent layer has an exposed major surface. 2. The multilayer mat as in claim 1 , wherein said at least one non-intumescent layer and said at least one intumescent layer are disposed relative to one another such that lateral edges of said at least one intumescent layer are positioned within the lateral edges of said at least one non-intumescent layer, 3. Ihe multilayer mat as in claim 1, wherein said at least one non-intumescent layer and said at least one intumescent layer are disposed relative to one anotlier such that one of the lateral edges of said at least one intumescent layer is in-line with one of the lateral edges (^fsaid at least one non-intumescent layer, and only the other lateral edge of said at least one intumescent layer lies within the lateral edges of said at least one non-intumescent layer, 4. The multilayer mat as in any one of claims I to 3, wherein said non-intumescent layer has a thickness in the range of from about 0.5 mm to about 20 mm and a bulk density in the range of from about 0.05 g/cc to about 0,4 g/cc, and said intumescent layer has a thickness in the range of from about 0.5 mm to about 15 mm and a bulk density in the range of Irom about 0,4 g/cc to about 0.75 g/cc. 5. \\\t multilayer mat as in any one of claims 1 to 4, further comprising at least one non-intumescent strip of one or more layers comprising ceramic fibers, with one said non-intumescent strip being positioned alongside one lateral edge of said at least one intumescent layer, wherein the width of said strip is narrower than the width ol said at least one intumescent layer. 6. The multilayer mat as in claim 5, wherein said at least one non-intumescenl strip is two non-intumescent strips, with each non-intumescent strip being of one or more layers comprising ceramic fibers, and with one said non-intumescent strip being disposed alongside each lateral edge of said at least one intumescent layer, wherein the width of each said strip is narrower than the width of said at least one intumescent layer. 7. fhe multilayer mat as in claim 5 or 6, wherein the combined widths of said at least one non-intumescent strip and said intumescent layer are together substantially equal to the width of said non-intumescent layer. 8. fhe multilayer mat as in any one of claims 5 to 7, wherein said at least one non-intumescent strip and said at least one intumescent layer are substantially co-planar. 0. 1 he multilayer mat as in any one of claims 5 to 8, wherein said at least one non- intumescent strip has a length that is substantially equal to the length of said at least one intumescent layer. 10. J he multilayer mat as in any one of claims 5 to 9, wherein each said non- intumescent strip has a thickness in the range of from about 0.5 mm to about 20 mm and a bulk density in the range of from about 0.05 g/cc to about 0.4 g/cc, said non-intumescent layer has a thickness in the range of from about 0.5 mm to about 20 mm and a mount density bulk density in the range of from about 0.05 g/cc to about 0.4 g/cc, and said intumescent layer has a thickness in the range ol IVom about 0.5 mm to about 15 mm and a bulk density in the range of from about 0.4 g/cc to about 0.75 g/cc. 11. A pollution control device comprising: a housing having an inner wall; a pollution control element disposed in said housing so as to form a gap therebetween; and a multilayer mat as in any one of claims 1 to 4, wherein said mat is disposed in said gap so as to mount said pollution control element in said housing. 12. I he pollution control device as in claim 11, wherein a portion ot the inner wall of said housing dellnes a recess, said mat is positioned so that at least a portion of said intumescent layer is received within said recess, and neitlier later edge olsaid intumescent layer is exposed to exhaust gases passing through said pollution control device. 13. The pollution control device as in claim 11, wherein a portion ofthe inner wall of said housing defines a recess, said mat is positioned so that said intumescent layer is received within said recess, and one lateral edge of said intumescent layer is exposed lo exhaust gases passing through said pollution control device. 14. A pollution control device comprising: a housing having an inner wall; a pollution control element disposed in said housing so as to form a gap therebetween; and a multilayer mat as in any one ofclaims 5 to 10, wherein said mat is disposed in said gap so as to mount said pollution control element in said housing. 15. llie pollution control device as in claim 14, wherein a portion ot the inner wall of said housing defines a recess, said mat is positioned so that said intumescent layer is received within said recess and not exposed to exhaust gases passing through said pollution control device, and one said intumescent strip is exposed to exhaust gases passing through said pollution control device. 16. • The pollution control device as in any one ot claims 11 lo 15, wherein said non- intumescent layer is positioned adjacent said pollution control element. 17. The pollution control device as in claim 16, wherein said non-intumesccnt layer is in contact with said pollntion control element. 18. I he pollution control device as in any one ot claims II to 17, wherein at least one of the lateral edges of said intumescent layer is substantially sealed from exposure to exhaust gases passing through said pollution conUol device. 10. The pollution control device as in any one of claims 11 to 18, wherein said device is a catalytic converter or an exhaust system filter. 20. An exhaust system for an internal combustion engine, said exhaust system comprising a pollution control device as in any one of claims 11 to 19, |
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| Patent Number | 279928 | ||||||||
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| Indian Patent Application Number | 1864/CHENP/2008 | ||||||||
| PG Journal Number | 06/2017 | ||||||||
| Publication Date | 10-Feb-2017 | ||||||||
| Grant Date | 03-Feb-2017 | ||||||||
| Date of Filing | 15-Apr-2008 | ||||||||
| Name of Patentee | 3M INNOVATIVE PROPERTIES COMPANY | ||||||||
| Applicant Address | 3M CENTER, PO BOX 33427, SAINT PAUL, MN 55133-3427, USA. | ||||||||
Inventors:
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| PCT International Classification Number | B01D 53/94 | ||||||||
| PCT International Application Number | PCT/US2006/039033 | ||||||||
| PCT International Filing date | 2006-10-10 | ||||||||
PCT Conventions:
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