EP4612113A1

EP4612113A1 - Higher temperature extrusion of ceramic precursor paste

Info

Publication number: EP4612113A1
Application number: EP23813115.5A
Authority: EP
Inventors: Keith Norman BUBB; Justin Bernard BULT; Aaron Gregory FOSTER; Rahul Suryakant KADAM; Michael James LEHMAN; Conor James Walsh
Original assignee: Corning Inc
Current assignee: Corning Inc
Priority date: 2022-10-31
Filing date: 2023-10-24
Publication date: 2025-09-10
Also published as: WO2024097046A1; CN120077021A

Abstract

Extrusion of a ceramic precursor paste at higher temperatures using polyethylene glycol in the paste.

Description

HIGHER TEMPERATURE EXTRUSION OF CERAMIC PRECURSOR PASTE

Cross-reference to Related Applications

[0001] This application claims the benefit of priority under 35 U.S.C. §119 of U.S. Provisional Application Serial No. 63/420919 filed on October 31, 2022 the content of which is relied upon and incorporated herein by reference in its entirety.

BACKGROUND

Field

[0002] The present specification relates to ceramic pastes (ceramic and/or ceramicforming pastes), methods of making such pastes, and methods of making self-standing extruded articles by extruding such pastes.

Technical Background

[0003] Ceramic products in a wide range of fields from refractory tubing to automotive and diesel exhaust filters and catalytic converter substrates can be manufactured by extrusion of pastes. The cost of such products can be driven by the rate of production of quality products.

Summary

[0004] Aspects of the disclosure pertain to porous filter bodies and methods for their manufacture and use.

[0005] In one aspect, ceramic precursor batch mixtures, or ceramic-forming pastes or ceramic pastes, are disclosed herein, comprising an inorganic component comprised of inorganic particles, a cellulosic binder component, a lubricant component comprised of fatty acid and/or synthetic oil, a liquid vehicle component comprised of water, and polyethylene oxide. In embodiments, a ratio of the amounts (in wt% with respect to the inorganic component) of the cellulosic binder component to the polyethylene oxide is between 0.5: 1 and 1.5: 1. In embodiments, the cellulosic binder component comprises a methylcellulose constituent comprised of one or more of methylcellulose, hydroxypropyl methylcellulose, hydroxyethyl cellulose, carboxylmethyl cellulose, and related cellulosic compounds. [0006] In another aspect, a method of manufacturing a ceramic article, the method comprising: extruding a ceramic batch mixture, the ceramic batch mixture comprising: an inorganic component in an inorganic amount; a binder component in a binder amount measured as a super addition by weight to the inorganic amount, the binder component comprising a cellulose-based polymer component in a cellulosic amount measured as a super addition by weight to the inorganic amount; and a polyethylene oxide component in a polyethylene oxide amount measured as a super addition by weight to the inorganic amount, wherein a ratio of the amounts (in wt%) of the methylcellulose to the polyethylene oxide is between 0.5: 1 and 1.5: 1; wherein the ceramic batch mixture is at a temperature of greater than or equal to 50 C during the extruding.

[0007] In embodiments, the ceramic batch mixture is at a temperature of greater than or equal to 55 C during the extruding.

[0008] In embodiments, the ceramic batch mixture is at a temperature of greater than or equal to 60 C during the extruding.

[0009] In embodiments, the ceramic batch mixture further comprises a pore former component in a pore former amount measured as a super addition by weight to the inorganic amount.

[0010] In embodiments, the ceramic batch mixture further comprises a liquid component in a liquid amount measured as a super addition by weight to the inorganic amount, the liquid component comprising water.

[0011] In embodiments, the ceramic batch mixture further comprises one or more lubricants.

[0012] In embodiments, the ceramic batch mixture further comprises one or more surfactants.

[0013] In embodiments, the ratio of the amounts (in wt%) of the methylcellulose to the polyethylene oxide is between 0.75: 1 and 1.25: 1.

[0014] In embodiments, the ratio of the amounts (in wt%) of the methylcellulose to the polyethylene oxide is between 0.80: 1 and 1.20: 1.

[0015] In embodiments, the ratio of the amounts (in wt%) of the methylcellulose to the polyethylene oxide is between 0.90: 1 and 1.10: 1. [0016] In embodiments, the ratio of the amounts (in wt%) of the methylcellulose to the polyethylene oxide is between 0.95: 1 and 1.05: 1.

[0017] In embodiments, the ratio of the amounts (in wt%) of the methylcellulose to the polyethylene oxide is about 1 : 1.

[0018] In embodiments, the ceramic batch mixture exhibits a wall drag greater than 5 and less than 16 psi at velocities between 0.5 and 2.5 inch/second as measured by capillary rheometer test.

[0019] In embodiments, the ceramic batch mixture exhibits a wall drag greater than 7 and less than 16 psi at velocities between 0.5 and 2.5 inch/second as measured by capillary rheometer test.

[0020] In embodiments, the ceramic batch mixture exhibits a wall drag greater than 10 and less than 25 psi at velocities between 1.0 and 2.5 inch/second as measured by capillary rheometer test.

[0021] In embodiments, a sample comprised of the ceramic batch mixture exhibits a strain at break of greater than 13 %.

[0022] In embodiments, a sample comprised of the ceramic batch mixture exhibits a strain at break of greater than 15 %.

[0023] In embodiments, a sample comprised of the ceramic batch mixture exhibits a strain at break of 13 to 20%.

[0024] In embodiments, the ceramic batch mixture exhibits wall drag which differs by less than 15% between temperatures of 20 to 40 C, inclusive, at extrusion velocities between 0.5 and 2.5 inch/second, inclusive.

[0025] In embodiments, the cellulose-based polymer comprises a cellulose ether. In embodiments, the cellulose ether comprises one or more of methylcellulose (MC), hydroxypropylcellulose or hydroxypropylmethylcellulose (HPMC) and hydroxyethylmethylcellulose (HEMC). In embodiments, the cellulose-based polymer comprises methylcellulose.

[0026] In embodiments, the ceramic batch mixture further comprises a lubricant component in a lubricant amount less than 1% by weight superaddition to the inorganic amount. In embodiments, the lubricant component comprises a synthetic lubricant in an amount less than 1% by weight superaddition to the inorganic amount. In embodiments, the lubricant component is free of synthetic lubricant. In embodiments, the lubricant component comprise an oil lubricant. In embodiments, the oil lubricant comprises one or more of light mineral oil, com oil, high molecular weight polybutenes, polyol esters, a blend of light mineral oil and wax emulsion, a blend of paraffin wax in com oil, and combinations of these.

[0027] In embodiments, the amount of oil lubricants is from about 1% by weight to about 10% by weight. In an exemplary embodiment, the oil lubricants are present from about 3% by weight to about 6% by weight. In embodiments, the pore former component comprises one or more of a starch, graphite, polymer resin, or combinations thereof.

[0028] In embodiments, the ceramic batch mixture further comprises a surfactant component in a surfactant amount less than 1% by weight superaddition to the inorganic amount. In embodiments, the surfactant component comprises one or more of C8 to C22 fatty acids, and/or their derivatives, C8 to C22 fatty esters, C8 to C22 fatty alcohols, and combinations of these.

[0029] In embodiments, the surfactant component comprises stearic, lauric, myristic, oleic, linoleic, palmitic acids, and/or their derivatives, tall oil, stearic acid in combination with ammonium lauryl sulfate, and combinations of all of these.

[0030] In embodiments, the surfactant component comprises lauric acid, stearic acid, oleic acid, tall oil, and combinations of these.

[0031] In embodiments, the amount of surfactants is from about 0.25% by weight to about 2% by weight as a super addition to the inorganic component.

[0032] In embodiments, the starting mixture comprises: an inorganic component comprised of cordierite precursor inorganic particles; a cellulosic binder component comprised of a methylcellulose constituent; a lubricant component comprised of fatty acid and/or synthetic oil; and a liquid vehicle component comprised of water.

[0033] In embodiments, the cellulosic binder component comprises methylcellulose. In embodiments, the cellulosic binder component consists of methylcellulose.

[0034] In embodiments, the PEO has a molecular weight of 1 million or more. In embodiments, the PEO has a molecular weight of 1-2 million. In embodiments, the PEO has a molecular weight of 2 million or more. In embodiments, the PEO has a molecular weight of 5 million or more. In embodiments, the PEO has a molecular weight of 7 million or more. [0035] In embodiments, the PEO has a molecular weight of 5 million or less. In embodiments, the PEO has a molecular weight of 2 million or less. In embodiments, the PEO has a molecular weight of 1 million or less.

[0036] In embodiments, the synthetic oil comprises a polyalphaolefin.

Brief Description of the Drawings

[0037] FIG.l graphically illustrates the entry pressure (Pentry, in psi) to a capillary rheometer die measured at various temperatures (°C) for a cordierite precursor batch with no PEO (Batch A) and for a cordierite precursor batch with 5 wt% PEO (as super addition to the cordierite-forming inorganic component) (Batch B).

[0038] FIG. 2 graphically illustrates capillary pressure vs rate (extrusion velocity through capillary rheometer die) for Batch A at 35 °C and Batch B at 55 °C which is representative of the stiffness as seen in FIG. 1.

[0039] FIG. 3 graphically illustrates calculated wall shear stress or wall drag Ty (in psi) for Batch A at 30 °C and Batch B (with PEO) at 55 °C. Thus, even with high stiffness from methylcellulose gelation, the PEO provides low wall drag at 55 °C.

[0040] FIG. 4 illustrates die pressure measurements taken from a 40 mm twin screw extruder die for Batch B (with PEO) at 55 °C and Batch A (without PEO) at 35 °C.

[0041] FIG. 5 graphically illustrates measured tensile stress (in MPa) vs. tensile strain (%) for Batch A (without PEO) at 35 °C, Batch A (without PEO) at 60 °C, and Batch B (with 5% PEO) at 60 °C.

Detailed Description

[0042] Reference will now be made in detail to embodiments of articles for emissions treatment, for example, filtration articles, comprising a plugged honeycomb filter body comprising inorganic deposits disposed on walls defining inlet channels of the plugged honeycomb filter body, the inorganic deposits comprising fumed silica particles, embodiments of which are illustrated in the accompanying drawings. Whenever possible, the same reference numerals will be used throughout the drawings to refer to the same or like parts. [0043] Specific and preferred values disclosed for components, ingredients, additives, reactants, constants, scaling factors, and like aspects, and ranges thereof, are for illustration only. They do not exclude other defined values or other values within defined ranges. The compositions, apparatus, and methods of the disclosure include those having any value or combination of the values, specific values, or ranges thereof described herein.

[0044] As used herein, “ceramic batch mixture” comprises a mixture which comprises, among other constituents, an inorganic component comprised of either ceramic constituents (e.g. cordierite or silicon carbide) or ceramic-forming precursor constituents (e.g. oxide constituents capable of being transformed into a ceramic material such as cordierite upon firing), or both. The inorganic particles can comprise single-constituent particulates such as cordierite or silicon carbide, or mixtures of oxides or other compounds that are convertible to crystalline ceramic materials upon firing, such as cordierite. Ceramic products may be manufactured by employing such batch mixtures. For example, a method of manufacturing a ceramic body comprises mixing an inorganic (ceramic and/or ceramic-forming) powder component such as a cordierite and/or cordierite forming component, water as the liquid vehicle, a cellulose ether binder, and a lubricant component comprised of a fatty acid constituent and an oil constituent such as a synthetic oil constituent; the method can further comprise extruding the paste through an extrusion die, such as a honeycomb extrusion die, to produce a self-standing, or self-supporting, extrudate body. The extrudate body, or a portion thereof, can be fired to sinter and/or reactively sinter the extruded composition into a ceramic composition. In embodiments, the mixture can be thoroughly blended to form a plasticized ceramic paste, and the method can further comprise pressing or extruding the ceramic paste through an extrusion die to form a self-standing body. In embodiments, the extrusion die is a honeycomb die and the extruded self-standing body is an unfired honeycomb body that retains its extruded shape despite the presence of retained water.

[0045] As used herein, “ceramic paste” comprises a paste which comprises, among other constituents, a liquid vehicle component such as water, and an inorganic component comprised of either ceramic constituents (e.g. cordierite or silicon carbide) or ceramic-forming precursor constituents (e.g. oxide constituents capable of being transformed into a ceramic material such as cordierite upon firing), or both. [0046] As used herein, the terms “unfired extruded body,” “green body,” “green ceramic body,” or “ceramic green body” refer to an non-fired body, part, or ware before firing, unless otherwise specified. The terms “batch mixture,” “ceramic precursor batch,” “green composition,” and “green batch material” refer to the mixture of materials that are used to form the green body by extrusion, unless otherwise specified. The non-fired extruded body and batch mixture contain a vehicle, such as water, and typically include inorganic components, and can include other materials such as binders, pore formers, lubricants, surfactants, stabilizers, plasticizers, and the like. As used herein, “firing” refers to thermal processing (heating) of the green body at an elevated temperature to form a ceramic material or a ceramic body, and comprises reaction sintering in which one or more batch materials physically react with each other to form one or more ceramic compounds, such as with cordierite-forming and aluminumtitanate forming batches, as well as sintering ceramic ingredients, such as with silicon carbide batches.

[0047] As used herein, a “wt %,” “weight percent,” or “percent by weight” of an inorganic or organic component, unless specifically stated to the contrary, is based on the total weight of the total inorganics in which the component is included. Organic components are specified herein as super additions based upon 100% of the inorganic components used.

[0048] The batch mixture from which the unfired extruded body is formed includes at least one inorganic component. The inorganic component may be one or more ceramic ingredient, one or more inorganic ceramic-forming ingredient, and/or combinations thereof. The ceramic ingredient may be, for example, cordierite, aluminum titanate, silicon carbide, mullite, alumina, and the like. The inorganic ceramic-forming ingredient may be cordieriteforming raw materials, aluminum titanate-forming raw materials, silicon carbide-forming raw materials, aluminum oxide-forming raw materials, alumina, silica, magnesia, titania, aluminum-containing ingredients, silicon-containing ingredients, titanium-containing ingredients, and the like.

[0049] Cordierite has the formula 2MgO.2A12O3.5SiO2. The cordierite-forming raw materials may include at least one magnesium source, at least one alumina source, at least one silica source, and at least one hydrated clay. In the embodiments described herein, sources of magnesium include, but are not limited to, magnesium oxide or other materials having low water solubility that, when fired, convert to MgO, such as Mg(0H)2, MgC03, and combinations thereof. For example, the source of magnesium may be talc (Mg3Si4O10(OH)2), including calcined and/or uncalcined talc, and coarse and/or fine talc. In various embodiments, the at least one magnesium source may be present in an amount from about 5 wt % to about 25 wt % of the overall cordierite-forming raw materials on an oxide basis. In other embodiments, the at least one magnesium source may be present in an amount from about 10 wt % to about 20 wt % of the cordierite-forming raw materials on an oxide basis. In further embodiments, the at least one magnesium source may be present in an amount from about 11 wt % to about 17 wt %.

[0050] Sources of alumina include, but are not limited to, powders that, when heated to a sufficiently high temperature in the absence of other raw materials, will yield substantially pure aluminum oxide. Examples of suitable alumina sources may include alpha-alumina, a transition alumina such as gamma-alumina or rho-alumina, hydrated alumina or aluminum trihydrate, gibbsite, corundum (A12O3), boehmite (A10(0H)), pseudoboehmite, aluminum hydroxide (Al(0H)3), aluminum oxyhydroxide, and mixtures thereof. In one embodiment, the at least one alumina source is a kaolin clay, and in another embodiment, the at least one alumina source is not a kaolin clay. The at least one alumina source may be present in an amount from about 25 wt % to about 45 wt % of the overall cordierite-forming raw materials on an oxide basis, for example. In another embodiment, the at least one alumina source may be present in an amount from about 30 wt % to about 40 wt % of the cordierite-forming raw materials on an oxide basis. In a further embodiment, the at least one alumina source may be present in an amount from about 32 wt % to about 38 wt % of the cordierite-forming raw materials on an oxide basis.

[0051] Silica may be present in its pure chemical state, such as a-quartz or fused silica. Sources of silica may include, but are not limited to, non-crystalline silica, such as fused silica or sol-gel silica, silicone resin, low-alumina substantially alkali-free zeolite, diatomaceous silica, kaolin, and crystalline silica, such as quartz or cristobalite. Additionally, the sources of silica may further include, but are not limited to, silica-forming sources that comprise a compound that forms free silica when heated. For example, silicic acid or a silicon organometallic compound may form free silica when heated. The at least one silica source may be present in an amount from about 40 wt % to about 60 wt % of the overall cordierite-forming raw materials on an oxide basis. In some embodiments, the at least one silica source may be present in an amount from about 45 wt % to about 55 wt % of the cordierite-forming raw materials on an oxide basis. In a further embodiment, the at least one silica source may be present in an amount from about 48 wt % to about 54 wt %.

[0052] Hydrated clays used in cordierite-forming raw materials can include, by way of example and not limitation, kaolinite (A12(Si2O5)(OH)4), halloysite (A12(Si2O5)(OH)4.H2O), pyrophylilite (A12(Si2O5)(OH)2), combinations or mixtures thereof, and the like. In some embodiments, the at least one alumina source and at least one silica source are not kaolin clays. In other embodiments, kaolin clays, raw and calcined, may comprise less than 30 wt % or less than 20 wt %, of the cordierite-forming raw materials. The green body may also include impurities, such as, for example, CaO, K2O, Na2O, and Fe2O3.

[0053] In some embodiments, the cordierite-forming raw materials have an overall composition comprising, in weight percent on an oxide basis, 5-25 wt % MgO, 40-60 wt % SiO2, and 25-45 wt % A12O3. In other embodiments, the cordierite-forming raw materials have an overall composition comprising, in weight percent on an oxide basis, 11-17 wt % MgO, 48- 54 wt % SiO2, and 32-38 wt % A12O3.

[0054] In embodiments in which the inorganic ceramic-forming ingredients form an aluminum titanate ceramic, the inorganic ceramic-forming ingredients can include an alumina source, a silica source, and a titania source. The titania source can in one aspect be a titanium dioxide composition, such as rutile titania, anatase titania, or a combination thereof. The alumina source and silica source may be selected from the sources of alumina and silica described hereinabove. The amounts of the inorganic ceramic-forming ingredients are suitable to provide a sintered phase aluminum titanate ceramic composition comprising, as characterized in an oxide weight percent basis, from about 8 to about 15 wt % SiO2, from about 45 to about 53 wt % A12O3, and from about 27 to about 33 wt % TiO2. For example, an exemplary inorganic aluminum titanate precursor powder batch composition can include approximately 10% quartz; approximately 47% alumina; approximately 30% titania; and approximately 13% additional inorganic additives. Additional exemplary non-limiting inorganic batch component mixtures suitable for forming aluminum titanate include those disclosed in U.S. Pat. Nos. 4,483,944; 4,855,265; 5,290,739; 6,620,751; 6,942,713; 6,849,181; 7,001,861; and 7,294,164, each of which is hereby incorporated by reference.

[0055] In embodiments in which the inorganic components form a silicon carbide ceramic, the inorganic ceramic-forming ingredients can include about 10-40%, by weight of the final batch, finely powdered silicon metal, preferably about 15-30%. The silicon powder should exhibit a small mean particle size, e.g., from about 0.2 micron to 50 microns, preferably 1-30 microns. The surface area of the silicon powder may, in some instances, be more descriptive than particle size, and should range between about 0.5 to 10 mSup2/Sup/g, preferably between about 1.0-5.0 mSup2/Sup/g. In various embodiments, the silicon powder is a crystalline silicon powder.

[0056] The silicon carbide ceramic-forming batch mixture also contains about 10-40%, by weight, of a carbon precursor, for example, a water soluble crosslinking thermoset resin having a viscosity of less than about 1000 centipoise (cp). The thermoset resin utilized may be a high carbon yield resin in an amount such that the resultant carbon to silicon ratio in the batch mixture is about 12:28 by weight, the stoichiometric ratio of Si — C needed for formation of silicon carbide.

[0057] Powdered silicon-containing fillers, in an amount up to 60%, by weight, may also be included in the silicon carbide ceramic-forming batch mixture. The main function of these fillers is to prevent excessive shrinkage of the green body during the carbonization and reactive consolidation/sintering steps. Suitable silicon-containing fillers include silicon carbide, silicon nitride, mullite or other refractory materials. Additional exemplary nonlimiting inorganic batch component mixtures suitable for forming silicon carbide include those disclosed in U.S. Pat. Nos. 6,555,031 and 6,699,429, each of which is hereby incorporated by reference.

[0058] In embodiments in which the inorganic components form an aluminum oxide ceramic, the inorganic components can include A12O3 and/or aluminum oxide-forming ingredients.

[0059] In addition to the inorganic components, each of the batch compositions includes an organics package that may include at least a non-polar carbon chain lubricant and an organic surfactant having a polar head. In various embodiments, the organics package may also include one or more binders. In embodiments, the organics package may also include one or more pore-forming materials. The term “organics package,” as used herein, excludes the amount of liquid vehicle and/or liquid solvents, such as water, included in various batch compositions. The organics package is used to form a flowable dispersion that has a relatively high loading of the ceramic material. The non-polar carbon chain lubricant and the organic surfactant are chemically compatible with the inorganic components, and can provide sufficient strength and stiffness to allow handling of the unfired extruded body. Additionally, the organics package is removable from the unfired extruded body during firing. In embodiments, the batch mixtures may have an organics package in percent by weight of the inorganic components, by super addition, from about 1% to about 25% or from about 2% to about 20%. In some embodiments, the batch mixture may have an organics package in percent by weight of the inorganic components, by super addition, from about 5% to about 15%, from about 7% to about 12%, or even from about 9% to about 10%. In some embodiments, the batch mixture may have an organics package in percent by weight of the inorganic components, by super addition, from about 5% to about 11%, or about 7%.

[0060] Binders may include, but are not limited to, cellulose-containing components such as methylcellulose, ethylhydroxy ethylcellulose, hydroxybutyl methylcellulose, hydroxymethylcellulose, hydroxypropyl methylcellulose, hydroxyethyl methylcellulose, hydroxybutylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, sodium carboxy methylcellulose, and mixtures thereof. Methylcellulose and/or methylcellulose derivatives, such as hydroxypropyl methylcellulose, are especially suited as organic binders.

[0061] Pore-forming materials can include, for example, a starch (e.g., com, barley, bean, potato, rice, tapioca, pea, sago palm, wheat, canna, and walnut shell flour), polymers (e.g., polybutylene, polymethylpentene, polyethylene (preferably beads), polypropylene (preferably beads), polystyrene, polyamides (nylons), epoxies, ABS, acrylics, and polyesters (PET)), hydrogen peroxides, and/or resins, such as phenol resin. In some embodiments, the organic material may comprise at least one pore-forming material. In other embodiments, the organic material may comprise at least two pore-forming materials. In further embodiments, the organic material may comprise at least three pore-forming materials. For example, in embodiments, a combination of a polymer and a starch may be used as the pore former. [0062] The non-polar carbon chain lubricant may provide fluidity to the ceramic precursor batch and may aid in the shaping of the ceramic precursor batch while also allowing the batch to remain sufficiently stiff during the forming (i.e., the extruding) process. The nonpolar carbon chain lubricant can include, for example, mineral oils distilled from petroleum, synthetic and semi-synthetic base oils, including Group II and Group III paraffinic base oils, polyalphaolefins, alphaolefins, and the like. In various embodiments, the non-polar carbon chain lubricant is a polyalphaolefin. Exemplary polyalphaolefins suitable for use include those sold under the trade name DURASYN®, including but not limited to DURASYN® 162 and DURASYN® 164, and SILKFLO®, including but not limited to SILKFLO® 362, available from INEOS Group AG (Switzerland), or under the trade names NEXBASE®, including but not limited to NEXBASE® 3020 (Neste Oil, Finland), and/or PARAFLEX™, including but not limited to PARAFLEX™ HT5 (Petro-Canada, Canada). In various embodiments, the nonpolar carbon chain lubricant is present in an amount of at least 3 wt % of the inorganic components, by super addition.

[0063] Organic surfactants having a polar head adsorb to the inorganic particles, keeping the inorganic particles in suspension, preventing clumping, and possibly generating migration pathways. The organic surfactant can include, for example, C8-C22 fatty acids and/or their ester or alcohol derivatives, such as stearic, lauric, linoleic, oleic, myristic, palmitic, and palmitoleic acids, soy lecithin, and mixtures thereof. In various embodiments, the organic surfactant is present in an amount of at least 0.3 wt % of the inorganic components, by super addition.

[0064] In various embodiments, liquid vehicles such as solvents may be added to the batch mixture to create a ceramic paste (precursor or otherwise) from which the unfired extruded body is formed. In embodiments, the solvents may include aqueous-based solvents, such as water or water-miscible solvents. In some embodiments, the liquid vehicle, or solvent, is water. The amount of aqueous solvent present in the ceramic precursor batch may range from about 20 wt % to about 50 wt %.

[0065] According to various embodiments, a method of making a ceramic body includes adding the organics package (including at least a non-polar carbon chain lubricant and an organic surfactant) to at least one inorganic component. The inorganic components and organic materials may be mixed to form a batch mixture. The inorganic components may be combined as powdered materials and intimately mixed to form a substantially homogeneous powder batch. The organic materials and/or solvent may be mixed with inorganic components individually, in any order, or together to form a substantially homogeneous batch. Other suitable steps and conditions for combining and/or mixing inorganic components and organic materials together to produce a substantially homogeneous batch may be used. For example, the inorganic components and organic materials may be mixed by a kneading process to form a substantially homogeneous batch.

[0066] In various embodiments, the batch mixture is shaped or formed into a structure using forming means, such as molding, pressing, casting, extrusion, and the like. According to various embodiments, the batch mixture is extruded to form a green body. Extrusion can be achieved using, for example, a hydraulic ram extrusion press, a two stage de-airing single auger extruder, or a twin screw mixer with a die assembly attached to the discharge end of the extruder. The batch mixture may be extruded at a predetermined temperature and velocity.

[0067] In various embodiments, the batch mixture is formed into a honeycomb structure. The honeycomb structure may include a web structure having a plurality of cells separated by cell walls. In some embodiments, each of the cell walls has a thickness of less than about 0.008 inch. The reduced wall drag batch mixtures disclosed herein can be used to produce thin-walled honeycomb structures which otherwise could be susceptible to distortion resulting from, among other things, differential shear or flow of the batch mixture through the extrusion die and/or interactions between the extrusion die and the batch materials.

[0068] After formation, the unfired extruded body is then fired at a selected temperature under suitable atmosphere and for a time dependent upon the composition, size, and geometry of the green body to result in a fired, porous ceramic body. Firing times and temperatures depend on factors such as the composition and amount of material in the green body and the type of equipment used to fire the green body. Firing temperatures for forming cordierite may range from about 1300° C. up to about 1450° C., with holding times at the peak temperatures ranging from about 1 hour to about 8 hours and total firing times that may range from about 20 hours up to about 85 hours. Suitable firing processes may include those described in U.S. Pat. Nos. 8,187,525, 6,287,509, 6,099,793, or U.S. Pat. No. 6,537,481, each of which is incorporated by reference in its entirety.

[0069] Batch flow characteristics may be determined, at least in part, by the stiffness and wall drag characteristics of the ceramic paste formed from the batch. The wall drag of the ceramic paste should be low enough that the ceramic paste moves through the manufacturing equipment and the extrusion dies at a reasonable pressure and with an even flow through the die. However, fluids used to lower wall drag should not be added in quantities such that the resultant extrudate loses stiffness (e.g., slumps) or has a decrease in tensile strength. In the embodiments described herein, the organics package of the batch mixture may be controlled to minimize wall drag while preventing slumping and retaining tensile strength, and in some embodiments even reducing the pressure used for extrusion. The decreased wall drag can provide product and quality benefits, process benefits, and reductions in manufacturing costs. For example, the ability to alter the wall drag for a batch mixture may minimize bow and reduce slump, while increasing die life and reducing energy costs. Accordingly, the batch mixtures of the various embodiments include concentrations of the non-polar carbon chain lubricant and the organic surfactant sufficient to reduce wall drag while maintaining good tensile strength and maintaining good firing characteristics.

[0070] The composition and/or wall drag state of the batch mixture can also affect the flow of the batch through the extruder. For example, the flow of the composition of the batch mixture may be influenced by the type of binder, the particle sizes and orientation or particles contained in the batch, and the like. In addition, it has been found that the flow of the batch is affected by the amount of non-polar carbon chain lubricant and the amount of organic surfactant having a polar head contained within the batch.

[0071] In addition to production rate of extruded ceramic products, the “die life” or footage of batch through an extrusion die before recoating is needed can be a significant cost factor. The rate at which products can be extruded is dependent on die pressure which includes contributions of the “wall drag” induced by the batch being forced through an extrusion die. Reduction of wall drag helps to achieve both higher rates of extrusion and longer die life.

[0072] Wall drag may be reduced using lubricants, and stiffness may be increased with the pressure relief from the wall drag reduction. Higher stiffness benefits product quality and may allow for thinner webs and larger diameters to be extruded. Large diameter thin wall honeycomb bodies require a significant stiffness increase compared to smaller ware, while maintaining die pressures and rheological properties could push the limits of known capabilities.

[0073] We have found a way to obtain high stiffness low wall drag ceramic precursor batch mixtures with increased tensile properties without the need for lubricant additions by adding PEO and running above the gelation temperature of the cellulosic binder like methylcellulose, a combination which allows for high stiffness, high tensile properties, and low die pressures. Another benefit may include reduced inline screen pressures within the extrusion line: with previous low wall drag compositions, the batch mixture needs to be screened at full stiffness in the mixing stream of an extruder such as a tandem twin screw extruder; the batch mixture can then be warmed, such as through a takeoff machine, and extruded at stiffness through the extrusion die.

[0074] Surprisingly we have found that the addition of PEO enables a cordierite precursor batch mixture to be extruded at higher temperatures , such as at greater than or equal to 50 C, greater than or equal to 60 C, greater than or equal to 70 C, 50 C to 80 C, 50 C to 70 C, 60 C to 80C, 70 C to 80 C. Moreover, the associated extrudate is imbued with a higher stiffness, advantageously providing enhanced strength to the extruded ware in the form of self- supporting or self-standing honeycomb body. Such green extruded honeycomb bodies can then be transported or conveyed into dryers, firing kilns, and the like for further processing and/or storage.

[0075] We have found that introducing PEO in addition to cellulosic binder like methylcellulose in a cordierite precursor batch mixture can provide such benefits. In embodiment, the batch mixture contains a 1 : 1 ratio of methylcellulose and PEO; the ratio around that level has been found to double the stiffness of the extrusion paste above the gelation temperature of the batch mixture (driven by the gelation temperature of the methylcellulose) while inducing a low wall drag state.

[0076] We have found that such substitution is particularly effective when the cellulosic binder comprises a methylcellulose constituent. In embodiments, the ratio of the amounts (in wt% with respect to the inorganic component) of the methylcellulose constituent to the polyethylene oxide is between 0.75: 1 and 1.25: 1. In embodiments, the ratio of the amounts (in wt%) of the methylcellulose constituent to the polyethylene oxide is between 0.80: 1 and 1.20: 1. In embodiments, the ratio of the amounts (in wt%) of the methylcellulose constituent to the polyethylene oxide is between 0.90: 1 and 1.10: 1. In embodiments, the ratio of the amounts (in wt%) of the methylcellulose constituent to the polyethylene oxide is between 0.95: 1 and 1.05: 1. In embodiments, the ratio of the amounts (in wt%) of the methylcellulose constituent to the polyethylene oxide is about 1 : 1. In embodiments, the batch mixture comprises methylcellulose in an amount greater than 3.0 wt% and less than 5.40 wt% with respect to the inorganic particles. In embodiments, the cellulosic binder component is methylcellulose in an amount greater than 3.0 wt% and less than 5.40 wt% with respect to the inorganic particles.

[0077] A measure of tensile strength is strain at break (“SAB” or “SAB%) as measured by capillary rheometer tensile test.

[0078] In one aspect, ceramic precursor batch mixtures, or ceramic-forming pastes or ceramic pastes, are disclosed herein, comprising an inorganic component comprised of inorganic particles, a cellulosic binder component, a lubricant component comprised of fatty acid and/or synthetic oil, a liquid vehicle component comprised of water, and polyethylene oxide. In embodiments, a ratio of the amounts (in wt% with respect to the inorganic component) of the cellulosic binder component to the polyethylene oxide is between 0.5: 1 and 1.5: 1. In embodiments, the cellulosic binder component comprises a methylcellulose constituent comprised of one or more of methylcellulose, hydroxypropyl methylcellulose, hydroxyethyl cellulose, carboxylmethyl cellulose, and related cellulosic compounds.

[0079] In embodiments, the cellulosic binder component consists of a methylcellulose constituent. In embodiments, the ratio of the amounts (in wt%) of the methylcellulose constituent to the polyethylene oxide is between 0.75: 1 and 1.25: 1. In embodiments, the ratio of the amounts (in wt%) of the methylcellulose constituent to the polyethylene oxide is between 0.80: 1 and 1.20: 1. In embodiments, the ratio of the amounts (in wt%) of the methylcellulose constituent to the polyethylene oxide is between 0.90: 1 and 1.10: 1. In embodiments, the ratio of the amounts (in wt%) of the methylcellulose constituent to the polyethylene oxide is between 0.95: 1 and 1.05: 1. In embodiments, the ratio of the amounts (in wt%) of the methylcellulose constituent to the polyethylene oxide is about 1 : 1. In embodiments, the batch mixture comprises methylcellulose in an amount greater than 3.0 wt% and less than 5.40 wt% with respect to the inorganic component. In embodiments, the cellulosic binder component is methylcellulose in an amount greater than 3.0 wt% and less than 5.40 wt% with respect to the inorganic component.

[0080] In embodiments, the cellulosic binder component consists of methylcellulose. In embodiments, the ratio of the amounts (in wt%) of the methylcellulose to the polyethylene oxide is between 0.75: 1 and 1.25: 1. In embodiments, the ratio of the amounts (in wt%) of the methylcellulose to the polyethylene oxide is between 0.80: 1 and 1.20: 1. In embodiments, the ratio of the amounts (in wt%) of the methylcellulose to the polyethylene oxide is between 0.90: 1 and 1.10: 1. In embodiments, the ratio of the amounts (in wt%) of the methylcellulose to the polyethylene oxide is between 0.95: 1 and 1.05: 1. In embodiments, the ratio of the amounts (in wt%) of the methylcellulose to the polyethylene oxide is about 1 : 1. In embodiments, the resulting batch mixture is in a lower wall drag state than the starting low wall drag batch mixture.

[0081] In embodiments, the PEO constituent has a molecular weight of 1 million or more. In embodiments, the PEO constituent has a molecular weight of 1-2 million. In embodiments, the PEO constituent has a molecular weight of 2 million or more. In embodiments, the PEO constituent has a molecular weight of 5 million or more. In embodiments, the PEO constituent has a molecular weight of 7 million or more.

[0082] In embodiments, the PEO constituent has a molecular weight of 5 million or less. In embodiments, the PEO constituent has a molecular weight of 4 million or less. In embodiments, the PEO constituent has a molecular weight of 3 million or less. In embodiments, the PEO constituent has a molecular weight of 2 million or less. In embodiments, the PEO constituent has a molecular weight of 1-2 million. In embodiments, the PEO constituent has a molecular weight of 1-3 million. In embodiments, the PEO constituent has a molecular weight of 1-4 million.

[0083] In embodiments, the oil constituent comprises a synthetic oil. In embodiments, the synthetic oil comprises a polyalphaolefin.

[0084] In embodiments, the inorganic particles are comprised of cordierite precursors. [0085] In embodiments, the batch mixture comprises methylcellulose in an amount greater than 3.0 wt% and less than 5.40 wt% with respect to the inorganic particles.

[0086] Examples

[0087] Embodiments will be further understood by the following non-limiting examples.

[0088] FIG.l graphically illustrates the entry pressure (Pentry, in psi) to a capillary rheometer die measured at various temperatures (°C) for a cordierite precursor batch with no PEO (Batch A) and for a cordierite precursor batch with 5 wt% PEO (as super addition to the cordierite-forming inorganic component) (Batch B), wherein both Batch A and Batch B contained 5.4 wt% methylcellulose. As seen in FIG. 1, gelation of Batch A begins around 40 °C and increases at a very rapid rate with increasing temperatures thereafter, thereby stiffening the batch mixture; at the higher temperatures, gelation is so pronounced, and stiffness increased to such high levels, that extrusion of the batch mixture no longer becomes possible. On the other hand, gelation of Batch B begins at a lower temperature (around 37 °C) than Batch A, however, significantly, gelation (as reflected in the pressure needed to pass through the capillary rheometer die) increases relatively slowly with increasing temperature, and the entry pressure levels off (relatively constant) at higher temperatures (around 60 to 80 °C). Thus, as seen in Batch B of FIG. l, the addition of 5% PEO, with no water or other changes to the composition of the batch mixture, provides similar entry pressure at low temperature, but once the gelation point is reached (lower than without PEO, because PEO takes water and results in higher methylcellulose concentration with respect to the liquid vehicle, which results in lower gel point), the pressure goes up and then levels out once again and runs stable to high temperature. With Batch B, we have found that extruding in the 60 degree C range gives double the stiffness compared to operating at room temperature. Notably, extrusion of Batch A at 60 °C would not have been feasible or even possible with commercially sized extrusion dies and extrusion equipment.

[0089] FIG. 2 graphically illustrates capillary pressure vs rate (extrusion velocity through capillary rheometer die) which reflects the stiffness as seen in FIG. 1.

[0090] As graphically illustrated in FIG. 3, the calculated wall shear stress or wall drag Ty (in psi) showed that Batch A at 30 °C exhibited double the stiffness of Batch B (with PEO) to 55 °C. Thus, even with high stiffness from methylcellulose gelation, the PEO provides low wall drag at 55 °C.

[0091] FIG. 4 illustrates die pressure measurements taken from a 40 mm twin screw extruder die which shows the gelled low wall drag Batch B (with PEO) at 55 °C has lower total die pressure (1500 psi) at double the stiffness compared to Batch A (without PEO) having higher total die pressure (2400 psi) at 35 °C.

[0092] FIG. 5 graphically illustrates measured tensile stress (in MPa) vs. tensile strain (%) for Batch A (without PEO) at 35 °C, Batch A (without PEO) at 60 °C, and Batch B (with 5% PEO) at 60 °C. The tensile properties shown for Batch B at 60 °C with PEO had higher peak load due to stiffness, but same Strain at Break compared to Batch A at 30 °C. For reference the Batch A at 60 °C Standard RRG is provided in FIG. 5 and shows almost no Strain at Break. [0093] It will be apparent to those skilled in the art that various modifications and variations can be made to the embodiments described herein without departing from the spirit and scope of the claimed subject matter. Thus, it is intended that the specification cover the modifications and variations of the various embodiments described herein provided such modification and variations come within the scope of the appended claims and their equivalents.

Claims

What is claimed is:

1. A method of manufacturing a ceramic article, the method comprising: extruding a ceramic batch mixture, the ceramic batch mixture comprising: an inorganic component in an inorganic amount; a binder component in a binder amount measured as a super addition by weight to the inorganic amount, the binder component comprising a cellulose-based polymer component in a cellulosic amount measured as a super addition by weight to the inorganic amount; and a polyethylene oxide component in a polyethylene oxide amount measured as a super addition by weight to the inorganic amount, wherein a ratio of the amounts (in wt%) of the methylcellulose to the polyethylene oxide is between 0.5: 1 and 1.5: 1; wherein the ceramic batch mixture is at a temperature of greater than or equal to 50 C during the extruding.

2. The method claim 1 wherein the ceramic batch mixture is at a temperature of greater than or equal to 55 C during the extruding.

3. The method claim 1 wherein the ceramic batch mixture further comprises a pore former component in a pore former amount measured as a super addition by weight to the inorganic amount.

4. The method claim 1 wherein the ceramic batch mixture further comprises a liquid component in a liquid amount measured as a super addition by weight to the inorganic amount, the liquid component comprising water.

5. The method claim 1 wherein the ceramic batch mixture further comprises one or more lubricants.

6. The method claim 1 wherein the ceramic batch mixture further comprises one or more surfactants.

7. The method claim 1 wherein the ratio of the amounts (in wt%) of the methylcellulose to the polyethylene oxide is between 0.75: 1 and 1.25: 1.

8. The method claim 1 wherein the ratio of the amounts (in wt%) of the methylcellulose to the polyethylene oxide is between 0.80: 1 and 1.20: 1.

9. The method claim 1 wherein the ratio of the amounts (in wt%) of the methylcellulose to the polyethylene oxide is between 0.90: 1 and 1.10: 1.

10. The method claim 1 wherein the ratio of the amounts (in wt%) of the methylcellulose to the polyethylene oxide is between 0.95: 1 and 1.05: 1.

11. The method claim 1 wherein the ratio of the amounts (in wt%) of the methylcellulose to the polyethylene oxide is about 1 : 1.

12. The method claim 1 wherein the ceramic batch mixture exhibits a wall drag greater than 5 and less than 16 psi at velocities between 0.5 and 2.5 inch/second as measured by capillary rheometer test.

13. The method claim 1 wherein the ceramic batch mixture exhibits a wall drag greater than 7 and less than 16 psi at velocities between 0.5 and 2.5 inch/second as measured by capillary rheometer test.

14. The method claim 1 wherein the ceramic batch mixture exhibits a wall drag greater than 10 and less than 25 psi at velocities between 1.0 and 2.5 inch/second as measured by capillary rheometer test.

15. The method claim 1 wherein a sample comprised of the ceramic batch mixture exhibits a strain at break of greater than 13 %.

16. The method claim 1 wherein a sample comprised of the ceramic batch mixture exhibits a strain at break of greater than 15 %.

17. The method claim 1 wherein a sample comprised of the ceramic batch mixture exhibits a strain at break of 13 to 20%.

18. The method claim 1 wherein the ceramic batch mixture exhibits wall drag which differs by less than 15% between temperatures of 20 to 40 C, inclusive, at extrusion velocities between 0.5 and 2.5 inch/second, inclusive.

19. The method claim 1 wherein the cellulose-based polymer comprises a cellulose ether.

20. The method claim 19 wherein the cellulose ether comprises one or more of methylcellulose (MC), hydroxypropylcellulose or hydroxypropylmethylcellulose (HPMC) and hydroxyethylmethylcellulose (HEMC).

21. The method claim 1 wherein the cellulose-based polymer comprises methylcellulose.

22. The method claim 1 wherein the ceramic batch mixture further comprises a lubricant component in a lubricant amount less than 1% by weight superaddition to the inorganic amount.

23. The method claim 22 wherein the lubricant component comprises a synthetic lubricant in an amount less than 1% by weight superaddition to the inorganic amount.

24. The method claim 22 wherein the lubricant component is free of synthetic lubricant.

25. The method claim 22 wherein the lubricant component comprise an oil lubricant.

26. The method claim 25 wherein the oil lubricant comprises one or more of light mineral oil, com oil, high molecular weight polybutenes, polyol esters, a blend of light mineral oil and wax emulsion, a blend of paraffin wax in com oil, and combinations of these.

27. The method claim 1 wherein the amount of oil lubricants is from about 1% by weight to about 10% by weight. In an exemplary embodiment, the oil lubricants are present from about 3% by weight to about 6% by weight.

28. The method claim 1 wherein the pore former component comprises one or more of a starch, graphite, polymer resin, or combinations thereof.

29. The method claim 1 wherein the ceramic batch mixture further comprises a surfactant component in a surfactant amount less than 1% by weight superaddition to the inorganic amount.

30. The method claim 29 wherein the surfactant component comprises one or more of C8 to C22 fatty acids, and/or their derivatives, C8 to C22 fatty esters, C8 to C22 fatty alcohols, and combinations of these.

31. The method claim 29 wherein the surfactant component comprises stearic, lauric, myristic, oleic, linoleic, palmitic acids, and/or their derivatives, tall oil, stearic acid in combination with ammonium lauryl sulfate, and combinations of all of these.

32. The method claim 29 wherein the surfactant component comprises lauric acid, stearic acid, oleic acid, tall oil, and combinations of these.

33. The method claim 29 wherein the amount of surfactants is from about 0.25% by weight to about 2% by weight as a super addition to the inorganic component.

34. The method of claim 1 wherein the mixture comprises: an inorganic component comprised of cordierite precursor inorganic particles; a cellulosic binder component comprised of a methylcellulose constituent; a lubricant component comprised of fatty acid and/or synthetic oil; and a liquid vehicle component comprised of water.

35. The method of claim 1 wherein the cellulosic binder component comprises methylcellulose.

36. The method of claim 1 wherein the cellulosic binder component consists of methylcellulose.

37. The batch mixture of claim 1 wherein the PEO has a molecular weight of 1 million or more.

38. The batch mixture of claim 1 wherein the PEO has a molecular weight of 1-2 million.

39. The batch mixture of claim 1 wherein the PEO has a molecular weight of 2 million or more.

40. The batch mixture of claim 1 wherein the PEO has a molecular weight of 5 million or more.

41. The batch mixture of claim 1 wherein the PEO has a molecular weight of 7 million or more.

42. The batch mixture of claim 5 wherein the synthetic oil comprises a polyalphaolefin.

43. The batch mixture of claim 1 wherein the PEO has a molecular weight of 5 million or less.

44. The batch mixture of claim 1 wherein the PEO has a molecular weight of 2 million or less.

45. The batch mixture of claim 1 wherein the PEO has a molecular weight of 1 million or less.