Polycrystalline mounting mat

Abstract

The present disclosure relates to innovative fiber mats for use in pollution control devices. These fiber mats incorporate a nonwoven layer of polycrystalline fibers having fibers of a given length. The fiber mat is cost-effective, exhibits favorable erosion resistance, and shows surprisingly good holding force performance in multi-cycle compression tests, offering economic benefits alongside technical advantages.

Description

[0001] PA103066W002

[0002] POLYCRYSTALLINE MOUNTING MAT

[0003] The present disclosure relates to an innovative fiber mat for use in pollution control devices. This fiber mat incorporates a nonwoven layer of polycrystalline fibers having fibers of a given length. The fiber mat is both cost-effective and provides desirable technical advantages.

[0004] BACKGROUND

[0005] Pollution control devices are employed to control atmospheric pollution of combustion engines. Such devices typically include a pollution control element, which typically contains catalytic converters or particle filters.

[0006] Pollution control elements using ceramic catalytic converters are known for removing carbon monoxide (CO), hydrocarbons (HC), and nitrogen oxides (NOx) from automobile engine exhaust gases. These systems typically include a ceramic catalyst carrier with a honeycomb shape stored in a metal casing. Other systems use ceramic particulate filters to remove particulates from diesel or gasoline engine exhaust gases.

[0007] Mounting mats are placed between the pollution control element and the housing to avoid damage to the pollution control element, compensate for thermal expansion differences, reduce mechanical shock to the pollution control element due to impact and vibration, and prevent exhaust gases from bypassing the pollution control element. These fiber mats are exposed to a wide range of temperatures, from -30°C to 1050°C, and must be resilient over prolonged periods of use. The mats are inserted into the pollution control device in a process known as “canning,” where the mat is wrapped around the pollution control element and then pushed into the housing. The force required for this insertion is referred to as “canning force.”

[0008] There is a continuous need for improved materials that can withstand the harsh conditions within pollution control devices. Traditional mounting mats often face challenges related to durability and cost. The present disclosure offers a solution by providing fiber mats made from polycrystalline fibers of a given length, which exhibit desirable erosion resistance and demonstrate surprisingly good results in multi-cycle compression tests.

[0009] SUMMARY

[0010] The present disclosure pertains to fiber mats designed for use in pollution control devices. These fiber mats incorporate a nonwoven layer of polycrystalline fibers, which extend in multiple planes normal to the z-direction without the need of mechanical binding processes. This unique fiber arrangement enhances the structural integrity and performance of the mat. For instance, the fiber mat exhibits desirable erosion resistance and shows surprisingly good holding force performance in multi -cycle compression tests.

[0011] The terms “fiber mat,” “fibrous mat,” and “mounting mat” are used interchangeably throughout the disclosure, with the understanding that, in the appropriate context, these mats can also be an insulation mat.All scientific and technical terms used herein have meanings commonly used in the art unless otherwise specified. The definitions provided herein are to facilitate understanding of certain terms used frequently in this application and are not meant to exclude a reasonable interpretation of those terms in the context of the present disclosure.

[0012] Unless otherwise indicated, all numbers in the description and the claims expressing feature sizes, amounts, and physical properties used in the specification and claims are to be understood as being modified in all instances by the term “about.” Accordingly, unless indicated to the contrary, the numerical parameters set forth in the foregoing specification and attached claims are approximations that can vary depending upon the desired properties sought to be obtained by those skilled in the art utilizing the teachings disclosed herein. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques.

[0013] Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the invention are approximations, the numerical values set forth in the specific examples are reported as precisely as possible. Any numerical value, however, inherently contains certain errors necessarily resulting from the standard deviations found in their respective testing measurements.

[0014] The recitation of numerical ranges by endpoints includes all numbers subsumed within that range (e.g. a range from 1 to 5 includes, for instance, 1, 1.5, 2, 2.75, 3, 3.80, 4, and 5) and any range within that range.

[0015] As used in this specification and the appended claims, the singular forms “a”, “an”, and “the” encompass embodiments having plural referents, unless the content clearly dictates otherwise. As used in this specification and the appended claims, the term “or” is generally employed in its sense including “and / or” unless the content clearly dictates otherwise.

[0016] Amounts of ingredients of a composition are indicated by % by weight (or “% wt”. or “wt.-%”) unless specified otherwise. The amounts of all ingredients add to a total of 100 % wt, unless specified otherwise.

[0017] Unless explicitly stated otherwise, all embodiments and optional features of the present disclosure can be combined freely.

[0018] In the context of the present disclosure, the terms “room temperature” and “ambient temperature” are used interchangeably and refer to a temperature of 23 °C at ambient pressure condition of about 101 kPa.

[0019] The term “polymer” will be understood to include polymers, copolymers (e.g., polymers formed using two or more different monomers), oligomers and combinations thereof, as well as polymers, oligomers, or copolymers that can be formed in a miscible blend. Polymers referred to in this disclosure include those polymerized in-situ from monomers as well as those materials that exist in a polymeric form independent of the processes used to create them herein.

[0020] The term “adjacent” refers to the relative position of two elements, such as, for example, two layers, that are close to each other and may or may not be necessarily in contact with each other or thatmay have one or more layers separating the two elements as understood by the context in which “adjacent” appears.

[0021] The term “immediately adjacent” refers to the relative position of two elements, such as, for example, two layers, that are next to each other and in contact with each other and have no intermediate layers separating the two elements. The term “immediately adjacent,” however, encompasses situations where one or both elements (e.g., layers) have been treated with a primer, or whose surface has been modified to affect the properties thereof, such as etching, embossing, etc., or has been modified by surface treatments, such as corona or plasma treatment, etc. that may improve adhesion.

[0022] The term “polycrystalline fibers” refers to fibers predominantly composed of crystalline structures, where the crystalline content is at least 1% by weight based on the total weight of the fibers. In general, the crystalline content is typically from 1% to 100%. Poly crystalline fibers typically contain a significant proportion of aluminum oxide AI2O3, with a content of at least 50 % by weight based on the weight of the fibers, and preferably at least 70 % by weight, and in some embodiments as high as 95%. Certain preferred embodiments of the present disclosure use mullite polycrystalline fibers with a composition of approximately 72% AI2O3 and 28% SiC>2. Mullite polycrystalline fibers have a crystallinity of less than 10%.

[0023] In the context of the present disclosure, the phrase “extending in more than one plane normal to the z-direction” refers to the orientation and arrangement of fibers within a fiber mat, where the fibers are not confined to a single flat plane but instead traverse multiple planes that are perpendicular to the z-direction. The z-direction is defined as the axis extending from the first major surface towards the second major surface of the mat (e.g., from the bottom to the top of the mat across the thickness of the mat.) In this configuration, it is assumed that the first major surface of the mat is aligned coinciding with a horizontal plane. In this context, a fiber that extends in more than one plane normal to the z-direction will have segments or portions that lie in different horizontal planes, creating a three-dimensional network of fibers.

[0024] This arrangement can be visualized when considering multiple planes normal to the z-direction (several horizontal slices of the mat, each at different heights along the z-direction.) When fibers extend in more than one plane normal to the z-direction, they cross through these multiple horizontal slices, creating an interwoven 3 -dimensional structure.

[0025] The term “mechanical binding processes” refers to techniques used to enhance the structural integrity of nonwoven mats. These processes involve physically moving or entangling fibers without the use of chemical binders. Examples of mechanical binding processes include needle punching, hydroentangling or spunlacing, stitching, carding and cross-lapping.

[0026] The term “uncompressed” refers to the state where the mat is not being subjected to compression forces, such as when the mat has not been installed around a pollution control element inside a casing. Conversely, the term “compressed” refers to the condition in which the mat's fibers are subjected to an external force or pressure, with the fibers being packed closer together, resulting in a reduction of the mat's thickness and volume, and increasing its density.The term “average length” of fibers refers to the arithmetic average of the fiber length of 20 separate measurements as described in the Example section.

[0027] BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1A is a micro CT photograph of a fiber mat according to the present disclosure, showing a 3 -dimensional structure of the fibers.

[0028] FIG. IB is a close-up micro CT photograph of a fiber mat according to the present disclosure, showing a 3 -dimensional structure of the fibers.

[0029] FIG. 2A is a micro CT photograph of a fiber mat made using a wet-laid process, lacking a 3-dimensional structure of the fibers.

[0030] FIG. 2B is a close-up micro CT photograph of a fiber mat made using a wet-laid process, lacking a 3 -dimensional structure of the fibers.

[0031] FIG. 3 shows an example of the calculation of fiber length.

[0032] DETAILED DESCRIPTION

[0033] The present disclosure is directed to fiber mats comprising a nonwoven layer of polycrystalline fibers. In some embodiments, these fibers have an average length ranging from 3 mm to 10 mm. The mat features a first major surface and a second major surface that opposes the first, with the z-direction extending from the first major surface towards the second major surface. At least a portion of the polycrystalline fibers extend in more than one plane normal to the z-direction without the use of mechanical binding processes. The fiber mat, when having an open gap density of 0.24 g / cm3, exhibits an erosion resistance of at most 1.3 wt % according to the Erosion Resistance Test. Additionally, when the fiber mat has an open gap density of 0.3636 g / cm3, it shows a holding force of at least 50 KPa after 1000 cycles according to the Multi-Cycle Compression Test.

[0034] Fiber Mats

[0035] An inorganic fibrous mat suitable for use in the present disclosure preferably contains one or more nonwoven layers made exclusively or predominantly from polycrystalline fibers. “Predominantly” as used herein means the content of polycrystalline fibers is at least 75 % by weight based on the total weight of the mat, preferably at least 85 % by weight, more preferably at least 90 % by weight and most preferably at least 95 % by weight (based on the total weight of the mat). The use of poly crystalline fibers, particularly in nonwoven mats, has the advantage that the mat exhibits very good temperature resistance and is also we 11 -adaptable to various shapes. In particular, poly crystalline fibrous mats are easily wrapped around porous pollution control elements commonly used in the art.

[0036] Poly crystalline fibers are fibers that contain at least 50 % by weight based on the weight of the fibers of AI2O3, preferably at least 70 % by weight and may or may not contain other oxides.

[0037] Polycrystalline fibers of the present disclosure with mullite composition contains 72% AI2O3 and 28%In some embodiments, the fiber mat may include other fibers in amounts of less than 25 % by weight based on the weight of the mat, preferably less than 15 % by weight, more preferably less than 10 % by weight or less than 5 % even 0 % by weight based on the weight of the mat. Preferably, the mat according to the present disclosure contains at least 95 % by weight, preferably at least 97 % by weight of fibers (weight percentages are based on the weight of the mat).

[0038] The mounting mat according to the present invention may or may not include Si O2. If SiO2is present, it is typically a component of fibers, its content may be from about 0.5 to 35 % by weight, for example from about 6 % to about 25 % by weight of SiO2(based on the weight of the mat). Mullite composition 72% AI2O3 and 28% SiO2

[0039] If the fiber mat comprises other fibers different from polycrystalline fibers, those fibers may be selected from the group of alumina fibers, alumina-silica fibers, glass fibers, ceramic fibers, carbon fibers, silicon carbide fibers, or boron silicate fibers or a combination thereof. In some specific embodiments, the fibrous material may include annealed melt-formed ceramic fibers, sol-gel formed ceramic fibers, polycrystalline ceramic fibers, alumina-silica fibers, glass fibers, including annealed glass fibers or nonbio-persistent fibers. Other fibers are possible as well, if they withstand the high temperatures and the temperature changes occurring in a pollution control device and the required holding forces during use of the pollution control device.

[0040] Surprisingly, the inventors have found that a fiber mat that was produced through a dry-laid process and that comprises the features mentioned in the independent claim shows improved performance in a multi -cycle compression test (MCC) and cold Erosion Resistance test without the need for adding any other performance ingredients, such as like inorganic binder or other additives.

[0041] In all known fiber mat making processes, organic binders may be added and they are a typical component of fiber mats. The organic binder holds the fibers together and helps produce a mat that is easily manageable during the assembly / installation process.

[0042] Organic binders, in general, do not influence the holding performance of the mat since they bum out once the mounting mat achieves operational temperatures. In some embodiments, the organic binder may be added in an amount between 1 and 15 wt.%, preferably between 1 and 10 wt.%. Typically, the organic binder may be an acrylic latex binder, a silicone binder in a wet laid process, or it may be mono-or bi-component fibers based on PE, PP, PET, etc. in a dry laid process. However, other binders may be used depending on the type of mat fibers used and the final application of the mat.

[0043] Fiber mats according to this disclosure may be used as mounting and / or as insulation mats. More specifically, fiber mats may be used as a mounting mat for exhaust gas treatment devices, as an insulation mat for example for components of an exhaust gas treatment device such as for example a catalytic converter or a filter.

[0044] According to one embodiment, the compression step of the processed fibrous material includes thermal bonding, chemical bonding (e.g., vinyl polymers and copolymers, acrylic ester polymers and copolymers, rubber and synthetic rubber, and natural binders, principally starch) or a combination thereof.Any other known compression methods in the field of inorganic fiber mats / members or mounting mats / members may be used as well.

[0045] In some embodiments, the fiber mat according to this disclosure may comprise an inorganic binder in an amount of 0.1 to 10 wt.% based on the total weight of the mounting mat, for example in an amount of 0.5 to 5 wt.%.

[0046] The fiber mat may comprise further additives for improved handling, improved performance, and / or improved protection properties.

[0047] Inorganic fillers

[0048] The inorganic fibrous mat for use in the present disclosure may or may not contain inorganic materials other than fibers. Typical inorganic materials used in mounting mats for pollution control devices include alumina particles, silica particles, and intumescent materials. As used herein, "intumescent material" means an inorganic material that expands, foams, or swells when exposed to a sufficient amount of thermal energy. Intumescent materials include vermiculites and graphites.

[0049] However, preferably, the mat according to this disclosure does not contain any intumescent material, or contains only low amounts of intumescent materials, for example in amounts of from 0 to less than 5 % by weight (based on the weight of the mat). The mat may or may not contain inorganic fillers, for example clays or metal oxides. Typical amounts include amounts from 0 to 5 % by weight (based on the weight of the mat).

[0050] Surface Additives

[0051] The fiber mats of the present disclosure may comprise certain surface additives to aid in controlling friction between each surface of the mat and the surface usually in contact with those surfaces on the mat. There are two different types of surface additives that may be applied to the major surfaces of the mats of this disclosure: first organic surface additives and second organic surface additives.

[0052] First organic surface additives are applied to the first major surface of an inorganic fibrous mat to reduce the friction coefficient, facilitating the insertion of the pollution control element into the housing. Suitable first organic surface additives include organic compounds with a melting point above 25 °C and less than 70°C, or oils with a kinematic viscosity at 40°C between 4 and 145 mm2 / s (measured in accordance with ASTM D445.) Preferred additives are hydrocarbons and functional hydrocarbons, such as aliphatic hydrocarbons and fatty acid esters, including diester or polyester oils.

[0053] These additives are typically applied in amounts less than 0.5% by weight, ensuring they do not significantly reduce the mat's compression resistance. The application method involves spraying the additives onto the surface of the finished mat, ensuring they are predominantly present on the surface facing the housing. This targeted application enhances the mat's performance during the canning process without the need for traditional binders, making the mats easier to handle and more effective in their application.

[0054] It may be desirable to increase the difference between the coefficients of friction of the first and second major surfaces of the mounting mats as described herein even further and / or adjust to desired values. In some embodiments, second organic surface additives are applied to the second major surfaceof the inorganic fibrous mat, which faces the pollution control element. The primary function of these additives is to increase the friction coefficient of this surface, thereby ensuring a secure fit between the mat and the pollution control element.

[0055] Examples of second organic surface additives are selected from hydrocarbon compounds, particularly solid hydrocarbons such as carbohydrates. Suitable carbohydrates include monosaccharides, disaccharides, oligosaccharides, and polysaccharides, with specific examples being glucose, sucrose, lactose, maltose, and their equivalents containing amino or sulfone moieties.

[0056] In preferred embodiments, a second organic surface additives include vinyl polymers and copolymers, acrylic ester polymers and copolymers, rubber and synthetic rubber, and natural binders, principally starch. The application of these additives is typically in the range of 0.005 to 0.4 wt.-%, based on the total weight of the mounting mat. These levels of additive ensure that the desired increase in friction is achieved without significantly altering the mat's overall properties. The method of application may involve spraying, dipping, or powder dry coating, followed by a heating step, if necessary, to fix the additives to the mat surface. This strategic use of second organic surface additives allows for a tailored friction profile, enhancing the mat's ability to securely hold the pollution control element in place during the canning process and throughout its operational life.

[0057] In other preferred embodiments the second organic surface additives include latex compositions comprising polymers or copolymers of acrylates, methacrylates, styrenes, butadienes, vinyl pyridines, acrylonitriles, vinyl chlorides, vinyl acetates, vinyl alcohols, ethylenes, polyurethanes, polyamides, silicones, polyesters, epoxy resins and combinations thereof.

[0058] Methods of Making Fiber Mats

[0059] This disclosure also relates to a method of making a fiber mat for mounting and / or protecting a component that gets exposed to changing temperatures. In preferred embodiments, the method comprising the steps of:

[0060] • providing bulk fibers;

[0061] • converting the bulk fibers in a known fiber mat making process into a fiber mat for mounting, protecting a component that gets exposed to changing temperatures, and / or insulation purposes. The step of converting the processed fibrous material and optionally bulk fibers is most preferably a dry laid process. A dry laid process uses air to mix the ingredients of a fiber mat together. A forming chamber may be used for this mixing step. The mixing step may be followed by a laying, compressing, and / or a converting step.

[0062] The step of converting the bulk fiber according to the dry laid process may comprise the steps of:

[0063] • supplying bulk fiber through an inlet of a forming box having an open bottom positioned over a forming wire to form a mat of fibers on the forming wire, the forming box having a plurality of fiber separating rollers provided in at least one row in the housing between the inlet and housing bottom for breaking apart clumps of fibers and an endless belt screen;

[0064] • transporting the mat of fibers out of the forming box by the forming wire; and• compressing the mat of fibers and restraining the mat of fibers in its compressed state thereby obtaining a fiber mat having a desired thickness suitable for mounting a pollution control element in the housing of a catalytic converter, among other potential uses.

[0065] Pollution control devices

[0066] The present disclosure also provides a housing containing the fiber mat and a pollution control element. The housing may be part of a pollution control device or the combination and assembly of pollution control element, mounting mat and housing may form a pollution control device. The mounting mat as described herein can be placed between the pollution control element and the housing when mounting the pollution control element into the housing, for example during the assembly of the pollution control device.

[0067] A pollution control element according to the present disclosure may be any kind of device that is used to reduce the amount of unwanted ingredients in exhaust gases of, for example, vehicles or industrial machines. A pollution control element includes an exhaust-gas after-treatment element. Other typical examples of pollution control elements are catalytic converters or diesel particulate filters. Catalytic converters typically contain a ceramic monolithic structure having walls that support the catalyst or a plurality of monolithic structures. The catalyst typically oxidizes carbon monoxide and hydrocarbons or reduces the oxides of nitrogen in the engine exhaust gases to control atmospheric pollution. The monolithic structures may be made of metal or of a ceramic material and may be porous and / or honeycomb-structured. The devices typically have a housing (typically made of stainless steel). The fiber mat according to this disclosure is placed between the pollution control element and the housing and may hold the pollution control element in place or may help to hold the pollution control element in place.

[0068] The present disclosure further provides a use of a fiber mat for assembling a pollution control device as described herein. Preferably, the use comprises wrapping the mounting mat around a pollution control element such that the second major surface of the mounting mat is adjacent the major surface of the pollution control element. Similarly, it is preferred that the use further comprises inserting the pollution control element wrapped in the mounting mat into a housing such that the first major surface of the mounting mat faces the housing, wherein the housing is part of a pollution control device.

[0069] EXEMPLARY EMBODIMENTS

[0070] 1. A fiber mat, comprising a nonwoven layer comprising polycrystalline fibers,

[0071] wherein the poly crystalline fibers have an average length from 3 mm to 10 mm,

[0072] wherein the mat has a first major surface and a second major surface opposing the first major surface,

[0073] wherein the z-direction extends from the first major surface towards the second major surface, wherein at least a portion of the polycrystalline fibers extend in more than one plane normal to the z-direction without use of mechanical binding processes,

[0074] wherein the fiber mat having an open gap density of 0.24 g / cm3has an erosion resistance of at most 1.3 wt % according to the Erosion Resistance Test,wherein the fiber mat having an open gap density of 0.3636g / cm3has a holding force of at least 50 kPa after 1000 cycles according to the Multi-Cycle Compression Test.

[0075] . A fiber mat, comprising a nonwoven layer comprising polycrystalline fibers,

[0076] wherein the mat further comprises one or more binders,

[0077] wherein the poly crystalline fibers have an average length from 3 mm to 10 mm,

[0078] wherein the mat has a first major surface and a second major surface opposing the first major surface,

[0079] wherein the z-direction extends from the first major surface towards the second major surface, wherein at least a portion of the polycrystalline fibers extend in more than one plane normal to the z-direction without use of mechanical binding processes,

[0080] wherein the fiber mat having an open gap density of 0.24 g / cm3has an erosion resistance of at most 1.3 wt % according to the Erosion Resistance Test,

[0081] wherein the fiber mat having an open gap density of 0.3636g / cm3has a holding force of at least 50 KPa after 1000 cycles according to the Multi-Cycle Compression Test.

[0082] 3. A fiber mat, according to any of the preceding embodiments, further comprising one or more binders.

[0083] . A fiber mat, according to any of the preceding embodiments, wherein the one or more binders are chosen from polymers or copolymers of acrylates, methacrylates, styrenes, butadienes, vinyl pyridines, acrylonitriles, vinyl chlorides, vinyl acetates, vinyl alcohols, ethylenes, polyurethanes, polyamides, silicones, polyesters, epoxy resins and combinations thereof.

[0084] 5. A fiber mat, according to any of the preceding embodiments, wherein the fiber mat having an open gap density of 0.3636 g / cm3has a holding force of at least 80 KPa after 1000 cycles according to the Multi-Cycle Compression Test.

[0085] 6. A fiber mat, according to any of the preceding embodiments, wherein the fiber mat having an open gap density of 0.3636 g / cm3has a holding force of at least 90 KPa after 1000 cycles according to the Multi-Cycle Compression Test.

[0086] 7. A fiber mat, according to any of the preceding embodiments, wherein the fiber mat does not contain added fillers.

[0087] 8. A fiber mat, according to any of the preceding embodiments, wherein the fiber mat has a sodium content of less than 50 ppm, preferably less than 40 ppm, more preferably less than 30 ppm, even more preferably less than 20 ppm.

[0088] 9. A fiber mat, according to any of the preceding embodiments, wherein the fiber mat contains at least by 75 % by weight of polycrystalline fibers, preferably at least 85 % by weight based on the total weight of the inorganic fibrous mat.

[0089] 10. A fiber mat, according to any of the preceding embodiments, wherein the fiber mat exhibits a total organic content of less than 10 % (measured per LOI), preferably from 3 % to 5 %.11. A fiber mat, according to any of the preceding claims, wherein the fiber mat has not been subjected to any mechanical binding process, such as needle punching, hydroentangling or spunlacing, stitching, carding and cross-lapping.

[0090] 12. A fiber mat, according to any of the preceding claims, wherein the poly crystalline fibers have a crystalline content of 1% to 20%.

[0091] 13. A fiber mat, according to any of the preceding embodiments, wherein the polycrystalline fibers have a crystalline content of 1% to 10%.

[0092] 14. A fiber mat, according to any of the preceding embodiments, wherein the fiber mat has an uncompressed thickness of 3-50 mm.

[0093] 15. A fiber mat, according to any of the preceding embodiments, wherein the fiber mat has an uncompressed thickness of 5-30 mm.

[0094] 16. A fiber mat, according to any of the preceding embodiments, wherein the fiber mat has a compressed thickness of 3-20 mm.

[0095] 17. A fiber mat, according to any of the preceding embodiments, wherein the fiber mat has a compressed thickness of 2-15 mm.

[0096] 18. A fiber mat, according to any of the preceding embodiments, wherein the fiber mat has a basis weight from 700 g / m2to 5000 g / m2.

[0097] 19. A fiber mat, according to any of the preceding embodiments, wherein the fiber mat has a basis weight from 900 g / m2to 3150 g / m2.

[0098] 20. A fiber mat, according to any of the preceding embodiments, wherein the fiber mat comprises a surface additive.

[0099] 21. A fiber mat, according to any of the preceding embodiments, wherein the fiber mat comprises a surface additive in the fiber mat as measured per LOI from 0.005 to 0.4 wt.-%, based on the weight of the fiber mat.

[0100] 22. A fiber mat, according to any of the preceding embodiments, wherein the fiber mat comprises a first surface additive chosen from aliphatic hydrocarbons having from 10 to 40 carbon atoms, aliphatic functionalized hydrocarbons having from 10 to 40 carbon atoms, and optionally a second surface additive chosen from carbohydrates and latex compositions.

[0101] 23. A fiber mat, according to any of the preceding embodiments, wherein the fiber mat comprises one or more first surface additives chosen from aliphatic hydrocarbons having from 10 to 40 carbon atoms, aliphatic functionalized hydrocarbons having from 10 to 40 carbon atoms, and carbohydrates; wherein the functionalized hydrocarbon has one or more functional groups chosen from hydroxy groups, carboxylic acid ester groups, ketone groups, oxygen-ether groups, and combinations thereof; and

[0102] wherein the fiber mat comprises one or more second surface additives chosen from carbohydrates and latex compositions,

[0103] wherein carbohydrates are chosen from monosaccharides such as glucose, fructose, and galactose; disaccharides such as sucrose, lactose, maltose, trehalose, cellobiose, and chitobiose;oligosaccharides such as raffinose, maltodextrins, cellodextrins, fructo-oligosaccharides, and galactooligosaccharides; and polysaccharides, and equivalents to the above-mentioned carbohydrates containing amino moieties and / or sulfone moieties and

[0104] wherein the latex compositions comprise polymers or copolymers of acrylates, methacrylates, styrenes, butadienes, vinyl pyridines, acrylonitriles, vinyl chlorides, vinyl acetates, vinyl alcohols, ethylenes, polyurethanes, polyamides, silicones, polyesters, epoxy resins and combinations thereof.

[0105] 24. A pollution control device comprising a housing, a pollution control element, and a fiber mat according to any of the preceding embodiments.

[0106] EXAMPLES

[0107] Certain embodiments of the present disclosure are illustrated in greater detail in the following examples. These examples are merely for illustrative purposes. It is not intended to limit the invention to the specific embodiments illustrated in these examples.

[0108] The following examples have been prepared:

[0109] • fiber mat made from bulk fiber with organic binder

[0110] • fiber mat made from cut bulk fiber with organic binder

[0111] Equipment Used:

[0112] • Sieve Vibratory Sieve Shaker AS 200 basic from Retsch

[0113] • Plastic Container 1000ml

[0114] • Scissors

[0115] • Compressed Air compressor.

[0116] • Aluminum Metal plates 13mm thick, approximately 150mm x 150 mm.

[0117] • Convection oven for drying

[0118] Materials Used:

[0119] • Trevira, bico-fiber product with Polyethylene terephthalate (PET) and Copolyolefin commercially available from Trevira GmbH, Germany

[0120] • Polycrystalline bulk fiber: as for example MAFTEC™ Bulk, commercially available from Maftec Group Co., Japan

[0121] • Interam™ 1101HT, polycry stalline wet-laid mounting mat from 3M US

[0122] • Interam™ 1600HTE, polycrystalline needled mounting mat from 3M US

[0123] • Interam™ 1600ANB, polycrystalline needled mounting mat from 3M US

[0124] • Interam™ 1650HTG, polycrystalline needled mounting mat from 3M US

[0125] Hand-sheet (mat) Making Process: The bulk fibers were cut with scissors and separated into different fiber lengths with the Vibratory Sieve Shaker AS 200 basic from Retsch in the following fiber lengths: < 0.425mm, 0.425mm <x<0.6mm, and > 0.85mm. The cut bulk fibers were opened with pressed air 4bar in a 1000 ml plastic container for 5min. The opened bulk fibers were mixed with the bicomponent binder fiber with air pressure of 4bar for 3min. Afterwards, the mixture was laid on a metal plate and coveredwith a second metal plate. The construction was screwed together to a gap of 7mm to provide a compressed thickness for the mats of 7mm. Then, the pre-compressed samples were heated up to 180°C for 30min to activate the binder fiber and connect to the polyX bulk fiber. The samples were cooled down to room temperature.

[0126] The average fiber diameter was in the range of 4-7pm

[0127] Example 1: For example 1, the cut bulk fiber <0.425mm was used with 3% of the bico-fiber for making a hand-sheet according to the above-described process.

[0128] Example 2: For example 2, the cut bulk fiber with fiber length 0.425mm<X<0.6mm was used with 3% of the bico-fiber for making a hand-sheet according to the above-described process.

[0129] Example 3: For example 3, the cut bulk fiber with fiber length >0.85mm was used with 3% of the bico-fiber for making a hand-sheet according to the above-described process.

[0130] Example 4: For example 4, the bulk fiber was processed in the production dry laid process with 4% bico-fiber.

[0131] Comparative Example 1: As a comparative example, the product Interam™ 1101HT from the wet laid production process has been used.

[0132] Table 1: test matrix

[0133]

[0134] Thickness

[0135] The thickness of the mats was determined according to ISO 10635: 1999(E), (dial gauge comparator method).

[0136] Density

[0137] Density is calculated by dividing the sample weight by the volume of the sample. The volume is calculated by multiplying the area of the sample (length multiplied by width) times the thickness of the sample.

[0138] Crystallinity

[0139] The crystallinity is measured with X-ray diffraction spectroscopy, for example D8 Discover from Bruker, with a tube voltage of 40kV and current 30mA within the angle 20-30°. Crystallinity iscalculated with the peak intensity (A) at a diffraction angle 20 of 26.3° with peak intensity (Ao) as reference and defining the intensity ratio as percent crystallinity (%)."

[0140] Crystallinity (%) = Peak intensity (A) / Peak intensity (Ao) x 100

[0141] Total organic content (Loss on Ignition; LOI)

[0142] The total content of organic material of a mat is determined by the loss on ignition method. A sample of a fiber mat having a dimension of 50 mm x 50 mm (length x width) was dried at 110 °C for 2 hours using a hot air oven ULP 500 from Memmert GmbH & Co. KG. The sample was then allowed to cool to room temperature (23±2 °C.) in a desiccator under dry conditions (e. g. using silica gel or a molecular sieve). After weighing the sample, the sample was heated (“fired”) to 600 °C for 2 hours using e. g. a muffle furnace LH 120 / 14 from Nabertherm, then allowed to cool to room temperature in a desiccator under dry conditions and weighed again.

[0143] The weight loss, i. e., the difference in weight before and after heating to 600 °C is generally considered as LOI of a fiber mat, presuming that under these conditions essentially the whole content of organic material decomposes and dissipates.

[0144] Fiber length measurement:

[0145] All samples were heated for 2 hours at 550°C to eliminate the organic binder. Afterwards, 0.001g of fibers from each sample were dissolved in 1.4g of pure water in a closed glass jar. Each sample was shaken 20 times by turning the jar 180 degrees and then placed in an ultrasonic bath Brandelin Sonorex RK 52H for 5 minutes. Two drops of each sample were placed on a glass object slide. The slides were heated for 20 minutes at 100°C. Fibers were then prepared on a carbon foil substrate for measurement using the REM Hitachi TM3000. The image resolution varied based on fiber length, with 20x to 3 Ox magnification used for longer fibers. Bent fibers were measured in smaller straight lines, particularly for longer fibers. In total, 20 measurements of each sample were taken, and the average, minimum, and maximum fiber lengths were recorded.

[0146] The fiber lengths were measured manually and the length was calculated manually. Figure 3 shows an example where the fiber length divided into several straight portions. The total fiber length was obtained as the sum of the lengths of the various straight segments.

[0147] Table 4: Fiber length measurement the examples and reference material

[0148]

[0149] As can be seen from the Examples, the fiber length used was different for each sample. The fibers from Example 4, produced using the dry laid production process, are approximately 9 times longer compared to the fibers from Comparative Example 1, produced using the wet laid production process.

[0150] Multi-cycle Compression Test MCC:

[0151] A common parameter to characterize the performance of a mounting mat is the so-called multicycle compression test. The Examples were tested at a temperature of 650 °C, the gap was cycled 1000 times between a closed gap and an open gap density. The open gap pressure after cycling was recorded.

[0152] For the tests in these examples a material test machine from Zwick / Roell Model Z010 from Zwick GmbH & Co KG, Ulm, Germany was utilized. The test machine was equipped with a lower fixed heatable stainless steel block and a load cell capable of measuring forces up to 10 kN and an upper heatable stainless steel block mounted to the movable crosshead of the test machine. For the tests a sample of each example and comparative example with 50.8 mm diameter was cut out of the mounting member and placed on the lower heatable stainless steel block. The crosshead was moved downwards to compress the mounting member to a defined closed gap, which corresponds to a density of the mounting member of 0.40 g / cm3. The maximum pressure at closed and before heating is called peak pressure P0. The relaxed pressure “P relaxed” is taken after lOmin dwell time after the closed gap is reached. The temperature of the heatable stainless steel blocks was raised to 650 °C while keeping the gap constant. After reaching the temperature of 650 °C, the gap was cycled between the closed gap position corresponding to a density of the mounting member of 0.40 g / cm3and an open gap position corresponding to a density of the mounting member of 0.3636 g / cm3. After 1000 cycles the test was stopped and the open gap pressure after 1000 cycles P1000 was recorded.

[0153] All samples and the comparative example were tested at isothermal temperatures at 650°C, 10% gap opening.

[0154] Gap Bulk Density GBD (closed gap): 0.40 g / cm3

[0155] • at 650°C test GBD (open gap): 0.3636 g / cm3(10% gap opening)

[0156] Table 2: MCC of examples and reference material, test temperature 650°C:

[0157]

[0158] As can be seen from the Examples, using the bulk fiber for making a fiber mounting mat with the dry laid process, the fiber length influences the results in the multi-cycle compression test in all three values: P0, Prelaxed, and P1000. The values are improved by using an average fiber length of 6mm, as demonstrated in Example 4.Erosion Resistance Test (EC)

[0159] A mat was cut in a sample 50 mm x 40 mm and mounted between 2 Inconel™ steel plates to a mount density of 0. 24 g / cm3. Based on the mat weight the gap was adjusted with spacers between the plates. The assembly was heated to 500°C for 2 hours to remove any organic material, including the binder and then cooled down to room temperature (23°C). An apparatus having five air nozzles distributed evenly in a circular fashion was used to provide pressurized air for the erosion test. Five samples could be tested simultaneously, each in front of each nozzle. Once the assembly was placed in front of an air nozzle, the mat edge was exposed to pulsating air jet (brand: Viehoever Sondermaschinen Gmbh) at a pressure of 4 bar for 4 hours. The pulsation frequency was 200 Hz with a nozzle diameter of 2mm. The pulsation frequency was achieved by a rotating perforated disc placed between the nozzle and the sample. The rotating disc had a diameter of 260 mm and 18 holes having a diameter of 25 mm each, evenly spaced around the circumference of the rotating disc, with a distance of 40mm between the centers of adjacent holes. After this process, the mat sample was removed and the weight loss due to erosion was determined.

[0160] Table 3: Erosion test results of examples and reference material:

[0161]

[0162] As can be seen from the Examples, the fiber length influences the erosion resistance. The best erosion resistance was achieved with the longer fibers from the dry laid production process in Example 4, with approximately 1.3% erosion.

[0163] X-Ray Imaging (micro-CT)

[0164] Samples were examined at a resolution of 5 pm using a X-ray microtomography scanner Bruker Skyscan 1272 x-ray microtomography scanner at X-ray source settings of 60 kV and 166 pA. Projected 2D images were collected using a step size of 0.1 degrees as the sample was rotated through 180 degrees. The resulting projected images were taken through the process of reconstruction to produce a stack of 2D slice images along the axis of sample rotation Bruker Nrecon.

[0165] The dry laid and wet laid production process examples showed different results regarding the mat structure. Example 4 from the dry laid production process, with an average fiber length of 6 mm, exhibited a 3D connection structure. In contrast, Comparative Example 1 from the wet laid production process showed only a 2D structure.Sodium extract content measurements:

[0166] 4 g of each mat material was diluted in 35 ml deionized water and were heated in an oven for 3 h at 60 °C. Afterwards the solution was filtered and filled in glass flakes and the sodium content was determined with ICP AES described in DIN EN ISO 11885:2009.

[0167] Three different commercially available mats from the Interam line were tested against a polycrystalline dry laid mat according to the present disclosure.

[0168] The results are summarized in table 2.

[0169] <

[0170]

Claims

We claim:

1. A fiber mat, comprising a nonwoven layer comprising polycrystalline fibers,wherein the poly crystalline fibers have an average length from 3 mm to 10 mm,wherein the mat has a first major surface and a second major surface opposing the first major surface,wherein the z-direction extends from the first major surface towards the second major surface, wherein at least a portion of the polycrystalline fibers extend in more than one plane normal to the z-direction without use of mechanical binding processes,wherein the fiber mat having an open gap density of 0.24 g / cm3has an erosion resistance of at most 1.3 wt % according to the Erosion Resistance Test,wherein the fiber mat having an open gap density of 0.3636g / cm3has a holding force of at least 50 kPa after 1000 cycles according to the Multi-Cycle Compression Test.

2. A fiber mat, according to any of the preceding claims, further comprising one or more binders.

3. A fiber mat, according to any of the preceding claims, wherein the one or more binders are chosen from polymers or copolymers of acrylates, methacrylates, styrenes, butadienes, vinyl pyridines, acrylonitriles, vinyl chlorides, vinyl acetates, vinyl alcohols, ethylenes, polyurethanes, polyamides, silicones, polyesters, epoxy resins and combinations thereof.

4. A fiber mat, according to any of the preceding claims, wherein the fiber mat does not contain added fillers.

5. A fiber mat, according to any of the preceding claims, wherein the fiber mat has a sodium content of less than 50 ppm, preferably less than 40 ppm, more preferably less than 30 ppm, even more preferably less than 20 ppm.

6. A fiber mat, according to any of the preceding claims, wherein the fiber mat contains at least by 75 % by weight of polycrystalline fibers, preferably at least 85 % by weight based on the total weight of the inorganic fibrous mat.

7. A fiber mat, according to any of the preceding claims, wherein the fiber mat has not been subjected to any mechanical binding process, such as needle punching, hydroentangling or spunlacing, stitching, carding and cross-lapping.

8. A fiber mat, according to any of the preceding claims, wherein the poly crystalline fibers have a crystalline content of 1% to 20%.

9. A fiber mat, according to any of the preceding claims, wherein the fiber mat has an uncompressed thickness of 3-50 mm.

10. A fiber mat, according to any of the preceding claims, wherein the fiber mat has a compressed thickness of 2- 15 mm.

11. A fiber mat, according to any of the preceding claims, wherein the fiber mat has a basis weight from 700 g / m2to 5000 g / m2.

12. A fiber mat, according to any of the preceding claims, wherein the fiber mat has a basis weight from 900 g / m2to 3150 g / m2.

13. A fiber mat, according to any of the preceding claims, wherein the fiber mat comprises a surface additive.

14. A fiber mat, according to any of the preceding claims, wherein the fiber mat comprises a first surface additive chosen from aliphatic hydrocarbons having from 10 to 40 carbon atoms, aliphatic functionalized hydrocarbons having from 10 to 40 carbon atoms, and optionally a second surface additive chosen from carbohydrates and latex compositions.

15. A pollution control device comprising a housing, a pollution control element, and a fiber mat according to any of the preceding claims.

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