WO2023096777A1

WO2023096777A1 - Water miscible batch components for ceramic extrudates

Info

Publication number: WO2023096777A1
Application number: PCT/US2022/049918
Authority: WO
Inventors: Gregg William Crume; James Robert Matthews; Jimmie Lewis Williams
Original assignee: Corning Inc
Current assignee: Corning Inc
Priority date: 2021-11-29
Filing date: 2022-11-15
Publication date: 2023-06-01
Anticipated expiration: 2024-05-29

Abstract

A binder system for use in producing ceramic extrudates includes a binder, a liquid vehicle, and a lubricant material that is partially miscible in the liquid vehicle at a temperature within an operating temperature range of extrusion equipment for producing the ceramic extrudates. The binder system is incorporated into batch mixtures for producing the ceramic extrudates. The batch mixtures include inorganic ceramic precursors and the binder system. The lubricant material that is partially miscible in the liquid vehicle reduces wall drag in the extrusion equipment and reduces oil fissures and other defects resulting from accumulation of non-miscible constituents, such as non-miscible organic oils, in the extrusion equipment.

Description

WATER MISCIBLE BATCH COMPONENTS FOR CERAMIC EXTRUDATES

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims the benefit of priority under 35 U.S.C. §119 of U.S. Provisional Application Serial No. 63/283585 filed on November 29, 2021, the content of which is relied upon and incorporated herein by reference in its entirety.

BACKGROUND

Field

[0002] The present specification generally relates to ceramic articles and, more specifically, to water miscible batch components for ceramic extrudates.

Technical Background

[0003] Ceramic honeycomb articles are widely used as anti -pollution devices in the exhaust systems of automotive vehicles, both as catalytic converter substrates and as particulate filters. Ceramic honeycomb articles for use in such applications are formed from a matrix of thin, porous ceramic walls that define a plurality of parallel, gas conducting channels. In ceramic honeycomb articles used as catalytic substrates, a catalytic coating is applied to the honeycomb articles to deposit catalyst material in or on the walls. The ceramic honeycomb articles may additionally or alternatively have end-plugs, e.g., in alternate gas conducting channels, to force exhaust gases to pass through the porous channel walls in order to capture and filter out soot and ash particulates prior to exhaust discharge. The ceramic honeycomb bodies can be manufactured by shaping a ceramic-forming batch mixture into green bodies and firing the green bodies. Batch mixtures for forming these ceramic honeycomb articles are desired.

SUMMARY

[0004] The present disclosure is directed to batch mixtures containing ceramic precursors for forming ceramic articles, such as porous ceramic honeycomb articles. In the formation of ceramic articles, mixtures of various inorganic powder constituents are prepared which are then formed into various shapes. The batch mixtures include the inorganic ceramic precursors and a binder system comprising at least a liquid vehicle (e.g., water or other solvent) and a binder. The binder system can include non-solvent organic compounds that are added to the batch to stiffen the batch while allowing extrusion at reduced pressure and reduced work imparted to the batch (e.g., torque in the case of a single screw or twin screw extruders). The non-solvent organic compounds are typically non-miscible organic oils, such as mixtures of polyalphaolefins and fatty acids, which can increase stiffness and lubricity of the batch mixture. However, these non-miscible organic oils have to be removed from the batch during firing, which can lengthen the firing cycle. In addition, the non-miscible organic oils can bum out through charring, which can cause defects in the finished ceramic articles after firing. Further, non-miscible organic oils separate from the batch and can accumulate in the extrusion hardware. Sufficient build-up over time can lead to streaks of these non-miscible organic oils on the surface of the parts, leading to unwanted surface defects, such as oil fissures. Being mobile species, these non-miscible organic oils may also evaporate in the drying process, potentially causing pollution issues, increasing the risk of fire hazards, or both.

[0005] Accordingly, a need exists for alternative binder systems and batch mixtures for producing porous ceramic honeycomb structures with improved lubricity and decreased defects caused by oil separation and accumulation.

[0006] According to embodiment first aspect of the present disclosure, a binder system for use in producing ceramic extrudates comprises a binder comprising methylcellulose, methylcellulose derivatives, or combinations of these; a liquid vehicle; and a lubricant material that is partially miscible in the liquid vehicle at a temperature that is within an operating temperature range of extrusion equipment for producing the ceramic extrudates. Partially miscible in the liquid vehicle means that a first portion of the lubricant material is soluble in the liquid vehicle and a second portion of the lubricant material is insoluble in the liquid vehicle and forms a second phase separate from a first phase comprising the liquid vehicle.

[0007] A second aspect of the present disclosure can comprise the first aspect, wherein the lubricant material has a solubility in the liquid vehicle that is inversely proportional to temperature, such that when the temperature increases, the solubility of the lubricant material in the liquid vehicle decreases.

[0008] A third aspect of the present disclosure can comprise either one of the first or second aspects, wherein the lubricant material is non-reactive with the liquid vehicle and the binder. [0009] A fourth aspect of the present disclosure can comprise any one of the first through third aspects, wherein the lubricant material is partially miscible in the liquid vehicle at a solubility temperature that is in a range of from 5 °C to 60 °C.

[0010] A fifth aspect of the present disclosure can comprise any one of the first through fourth aspects, wherein the lubricant material comprises poly(propylene) glycol (PPG).

[0011] A sixth aspect of the present disclosure can comprise the fifth aspect, wherein the PPG has a number average molecular weight (Mn) of less than or equal to 2000 Daltons.

[0012] A seventh aspect of the present disclosure can comprise either one of the fifth or sixth aspects, wherein the PPG has a number average molecular weight of from 400 Daltons to 2000 Daltons.

[0013] An eighth aspect of the present disclosure can comprise any one of the fifth through seventh aspects, wherein the PPG has a multi-modal molecular weight distribution.

[0014] A ninth aspect of the present disclosure can comprise any one of the fifth through eighth aspects, wherein the lubricant material comprises a mixture of at least two different PPGs, where each PPG has a different number average molecular weight.

[0015] A tenth aspect of the present disclosure can comprise any one of the first through ninth aspects, wherein the liquid vehicle is water.

[0016] An eleventh aspect of the present disclosure can comprise any one of the first through tenth aspects, wherein the composition does not include fatty acids or polyalphaolefin oils.

[0017] A twelfth aspect of the present disclosure can comprise any one of the first through eleventh aspects and can be directed to a composition for producing ceramic honeycomb structures. The composition comprising at least one inorganic ceramic precursor and the binder system of any one of the first through eleventh aspects.

[0018] A thirteenth aspect of the present disclosure can comprise the twelfth aspect, wherein the composition comprises greater than or equal to 1 wt.%, or from 1 wt.% to 15 wt.% of the lubricant material based on the total weight of the at least one inorganic ceramic precursor.

[0019] A fourteenth aspect of the present disclosure can comprise either one of the twelfth or thirteenth aspects, wherein the composition comprises greater than or equal to 2 percent by volume of the lubricant material, where the percent by volume is equal to the true volume of the lubricant material divided by the total true volume of the inorganic ceramic precursors times 100.

[0020] A fifteenth aspect of the present disclosure can comprise any one of the twelfth through fourteenth aspects, wherein the lubricant material comprises poly(propylene) glycol (PPG) and the composition comprises from 1 wt.% to 15 wt.% PPG based on the total weight of the at least one inorganic ceramic precursor.

[0021] A sixteenth aspect of the present disclosure can comprise the fifteenth aspect, wherein the composition comprises from 2% to 42% by volume of the PPG, where the percent by volume is equal to the true volume of the PPG divided by the total true volume of the inorganic ceramic precursors times 100.

[0022] A seventeenth aspect of the present disclosure can comprise any one of the twelfth through sixteenth aspects, wherein the one or more ceramic precursors comprises at least one cordierite forming raw material.

[0023] An eighteenth aspect of the present disclosure can comprise any one of the twelfth through seventeenth aspects, further comprising one or more processing additives selected from plasticizers, surfactants, dispersants, or combinations of these.

[0024] A nineteenth aspect of the present disclosure can comprise any one of the twelfth through eighteenth aspects, comprising from 20 wt.% to 50 wt.% water, based on the total weight of the ceramic precursors, from 1 wt.% to 15 wt.% binder, based on the total weight of the ceramic precursors, and from 1 wt.% to 15 wt.% PPG, based on the total weight of the ceramic precursors.

[0025] A twentieth aspect of the present disclosure is directed to method for forming a ceramic article, the method comprising forming a batch mixture comprising at least one ceramic precursor and a binder system. The binder system can comprise any of the binder systems of the first through eleventh aspects. In embodiments, the binder system can comprise a binder comprising methylcellulose, methylcellulose derivative, or combinations of these; a liquid vehicle; and a lubricant material that is partially miscible in the liquid vehicle at a temperature that is within an operating temperature range of extrusion equipment for producing a ceramic extrudate. Partially miscible in the liquid vehicle means that a first portion of the lubricant material is soluble in the liquid vehicle and a second portion of the lubricant material is insoluble in the liquid vehicle and forms a second phase separate from a first phase comprising the liquid vehicle. The method further includes extruding the batch mixture to produce the ceramic extrudate, wherein the lubricant material in the batch mixture reduces extrusion pressure and torque in the extrusion equipment during extrusion. The method can further comprise firing the ceramic extrudate under conditions sufficient to produce the ceramic article.

[0026] A twenty-first aspect of the present disclosure can comprise the twentieth aspect, wherein the partial miscibility of the lubricant material in the liquid vehicle may reduce accumulation of the second phase in the extrusion equipment.

[0027] A twenty-second aspect of the present disclosure can comprise either one of the twentieth or twenty first aspects, further comprising washcoating and calcining the ceramic article.

[0028] A twenty-third aspect of the present disclosure can comprise any one of the twentieth through twenty-second aspects, further comprising thermally treating the ceramic article.

[0029] A twenty-fourth aspect of the present disclosure can comprise any one of the twentieth through twenty-third aspects, wherein the lubricant material has a solubility in the liquid vehicle that is inversely proportional to the temperature.

[0030] A twenty-fifth aspect of the present disclosure can comprise any one of the twentieth through twenty-fourth aspects, wherein the lubricant material is self-regulating, meaning that as drag in the extrusion equipment increases, temperature increases, which decreases the solubility of the lubricant material in the liquid vehicle, which increases the amount of lubricant material at the wall of the extrusion device, which then reduces the drag on the wall, reducing the temperature that further increases the solubility of the lubricant material in the liquid vehicle.

[0031] A twenty-sixth aspect of the present disclosure can comprise any one of the twentieth through twenty-fifth aspects, wherein the lubricant material comprises poly(propylene) glycol (PPG) having a number average molecular weight of from 400 Daltons to 2000 Daltons.

[0032] A twenty-seventh aspect of the present disclosure can comprise any one of the twentieth through twenty-sixth aspects, further comprising extruding the batch mixture with the extrusion equipment to produce the ceramic extrudate, measuring one or more operating conditions of the extruding equipment, and adjusting an amount, a number average molecular weight, a molecular weight distribution, or combinations thereof of the lubricant material, such as but not limited to PPG, based on the measured values of the one or more operating conditions.

[0033] A twenty-eighth aspect of the present disclosure can comprise the twenty-seventh aspect, wherein the operating conditions comprises one or more of an extrusion rate, an extrusion pressure, an extrusion temperature, back-up length, work imparted to the batch, or combinations of these.

[0034] Additional features and advantages will be set forth in the detailed description which follows, and in part will be readily apparent to those skilled in the art from that description or recognized by practicing the embodiments described herein, including the detailed description which follows, the claims, as well as the appended drawings.

[0035] It is to be understood that both the foregoing general description and the following detailed description describe various embodiments and are intended to provide an overview or framework for understanding the nature and character of the claimed subject matter. The accompanying drawings are included to provide a further understanding of the various embodiments, and are incorporated into and constitute a part of this specification. The drawings illustrate the various embodiments described herein, and together with the description serve to explain the principles and operations of the claimed subject matter.

BRIEF DESCRIPTION OF THE DRAWINGS

[0036] FIG. 1 schematically depicts a porous ceramic honeycomb article, according to one or more embodiments shown and described herein;

[0037] FIG. 2 graphically depicts rate sweep testing data comprising pressure and wall drag (y-axis) as a function of extrusion velocity (y-axis) for extrusion of the batch mixtures of Examples 2 and 3 compared to the control batch of Comparative Example 1, according to one or more embodiments shown and described herein;

[0038] FIG. 3 graphically depicts rate sweep testing data comprising pressure and wall drag (y-axis) as a function of extrusion velocity (y-axis) for extrusion of the batch mixtures of Examples 4 and 5 compared to the control batch of Comparative Example 1, according to one or more embodiments shown and described herein; [0039] FIG. 4 graphically depicts rate sweep testing data comprising pressure and wall drag (y-axis) as a function of extrusion velocity (y-axis) for extrusion of the batch mixtures of Examples 6-8 compared to the control batch of Comparative Example 1, according to one or more embodiments shown and described herein;

[0040] FIG. 5 graphically depicts rate sweep testing data comprising pressure and wall drag (y-axis) as a function of extrusion velocity (y-axis) for extrusion of the batch mixture of Example 9 comprising a mixture of polyethylene glycols) (PPGs) of different molecular weights compared to the control batch of Comparative Example 1 and the batch mixtures of Examples 4 and 5, each of which having a single PPG, according to one or more embodiments shown and described herein;

[0041] FIG. 6 graphically depicts the toughness of various batch mixtures compared to the toughness of the control batch of Comparative Example 1, according to one or more embodiments shown and described herein;

[0042] FIG. 7 graphically depicts rate sweep testing data comprising pressure and wall drag (y-axis) as a function of extrusion velocity (y-axis) for extrusion of the batch mixture of Example 4 compared to the control batch of Comparative Example 1 and the comparative batch mixture of Comparative Example 11, which comprised polyethylene glycol as the lubricant material, according to one or more embodiments shown and described herein;

[0043] FIG. 8 graphically depicts relative die pressure (y-axis) as a function of run time (x- axis) for extrusion of a batch mixture of Example 12 comprising PPG compared to extrusion of the control batch of Comparative Example 1, according to one or more embodiments shown and described herein;

[0044] FIG. 9 graphically depicts torque (y-axis) as a function of run time (x-axis) for extrusion of a batch mixture of Example 12 comprising PPG compared to extrusion of the control batch of Comparative Example 1, according to one or more embodiments shown and described herein; and

[0045] FIG. 10 graphically depicts temperature (y-axis) vs. concentration (x-axis) phase diagrams for PPG having a molecular weight of 1000 Daltons and polypropylene glycol having a molecular weight of 2000 Daltons, according to one or more embodiments shown and described herein. DETAILED DESCRIPTION

[0046] Reference will now be made in detail to embodiments of porous ceramic honeycomb articles, examples 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.

[0047] The present disclosure is directed to batch mixtures for producing extrudates, which are then fired to produce ceramic articles, such as but not limited to porous ceramic honeycomb articles. The batch mixtures of the present disclosure comprise one or a plurality of inorganic ceramic precursors and a binder system. The binder system comprises a binder, a liquid vehicle, and a lubricant material. The binder comprises methylcellulose, methylcellulose derivatives, or combinations of these. The lubricant material is a material that is partially miscible in the liquid vehicle at a temperature that is within an operating temperature range (e.g., from 5 °C to 60 °C) of the extrusion equipment for producing the ceramic extrudates. Partially miscible in the liquid vehicle means that a first portion of the lubricant material is soluble in the liquid vehicle and a second portion of the lubricant material is insoluble in the liquid vehicle and forms a second phase separate from a first phase comprising the liquid vehicle. In embodiments, the liquid vehicle is water and the lubricant material is polypropylene glycol) (PPG) or a mixture of PPGs. Ceramic articles prepared from the batch mixtures comprising the lubricant material are also disclosed.

[0048] The lubricant material that is partially miscible in the liquid vehicle at a temperature within an operating temperature range of the extrusion equipment reduces wall drag compared to comparative batch mixtures comprising fatty acids and polyalphaolefin oils as processing aids, while also producing extrudates having tensile properties comparable to the batch mixtures comprising fatty acids and polyalphaolefin oils. The batch mixtures comprising the lubricant materials partially miscible in the liquid vehicle may further reduce oil fissures and other defects in ceramic articles produced from the batch mixtures.

[0049] As used herein, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to a "silica source" or an "alumina source" can comprise aspects of having two or more such silica sources or alumina sources, respectively, unless the context clearly indicates otherwise. [0050] As used herein, a "wt. %" or "weight percent" or "percent by weight" of an organic component, unless specifically stated to the contrary, is based on the total weight of the total inorganics in which the component is included. All organic additions, such as, for example, pore formers and binders, are specified herein as superadditions based upon 100% of the inorganic ceramic precursors in the batch mixture. As used herein, a “percent by volume” or “volume percent” or “vol.%” of an organic component, unless specifically stated to the contrary, refers to the true volume of the organic component divided by the total true volume of the inorganic ceramic precursors in the batch mixture times 100.

[0051] Referring now to FIG. 1, one embodiment of a ceramic article comprising a porous ceramic honeycomb article 100 is schematically depicted. The porous ceramic honeycomb article 100 can be used as a wall-flow filter for particulate matter filtration. For example, the porous ceramic honeycomb article 100 can be used in filtering particulate matter from a vehicle exhaust. The porous ceramic honeycomb article 100 generally comprises a porous cordierite ceramic honeycomb body having a plurality of cell channels 101 extending between a first end 102 and a second end 104. The plurality of generally parallel cell channels 101 formed by, and at least partially defined by, intersecting porous channel walls 106 that extend from the first end 102 to the second end 104. The porous ceramic honeycomb article 100 can also comprise a skin formed about and surrounding the plurality of cell channels. This skin can be extruded during the formation of the channel walls 106 or formed in later processing as an after-applied skin, by applying a skinning cement to the outer peripheral portion of the cells.

[0052] In embodiments, the plurality of parallel cell channels 101 are generally square in cross section and are formed into a honeycomb structure. However, in alternative embodiments, the plurality of parallel cell channels in the honeycomb structure can have other cross-sectional configurations, including rectangular, round, oblong, triangular, octagonal, hexagonal, or combinations thereof.

[0053] The term "honeycomb" as used herein is defined as a structure of longitudinally- extending cells formed from the channel walls 106 and preferably having a generally repeating grid pattern therein. For honeycombs utilized in filter applications, certain cells are designated as inlet cells 108 and certain other cells are designated as outlet cells 110. Moreover, in a porous ceramic honeycomb article 100, at least some of the cells can be plugged with plugs 112. Generally, the plugs 112 are arranged at or near the ends of the cell channels and are arranged in some defined pattern, such as in the checkerboard pattern shown in FIG. 1, with every other cell being plugged at an end. The inlet channels 108 can be plugged at or near the second end 104, and the outlet channels 110 can be plugged at or near the first end 102 on channels not corresponding to the inlet channels. Accordingly, each cell can be plugged at or near one end of the porous ceramic honeycomb article only.

[0054] While FIG. 1 depicts one embodiment of porous ceramic honeycomb articles 100, in which some or all of the channels are plugged, is should be understood that, in alternative embodiments, all the channels of the porous ceramic honeycomb articles can be unplugged, such as when the porous ceramic honeycomb article 100 is used as catalytic through-flow substrates for use with gasoline engines. Additionally, the batch mixtures and binder systems of the present disclosure can be suitable for producing a broader range of ceramic articles, in particular, those ceramic articles formed through extrusion of the batch mixture to produce an extrudate, which then is fired to produce the ceramic article.

[0055] The ceramic articles described herein, such as the porous ceramic honeycomb articles 100, are formed by first mixing a batch mixture comprising one or a plurality of ceramic precursors, forming the batch mixture into a green article such as an extrudate, drying the green article and firing the green article under conditions suitable to initially produce the ceramic article. Other post-processing steps can be undertaken after firing.

[0056] The batch mixtures comprise a combination of constituent materials suitable for producing a ceramic article. In general, the batch mixture comprises a combination of inorganic ceramic precursors including but not limited to a relatively fine talc, a relatively fine silica source, and an alumina source. In embodiments, the inorganic ceramic precursors further comprise clay, such as, for example, kaolin clay. In embodiments, the batch mixture also comprises one or more organic pore formers. For example, the batch mixture can comprise a starch or graphite as pore formers. The batch mixture further comprises a binder system comprising a binder material, a liquid vehicle, and a processing aid, such as a lubricant material. The batch mixtures can also comprise one or more other additives, such as but not limited to plasticizers, surfactants, dispersants, or other types of organic additives.

[0057] In embodiments, the batch mixture comprises ceramic precursors that are cordierite precursors suitable for forming ceramic articles that predominately comprise a cordierite crystalline phase. Although described herein in the context of cordierite-based ceramic articles, it is understood that the binder system of the present disclosure can be suitable for use with other ceramic precursors to produce other types of ceramic articles, such as but not limited to alumina articles, silicon carbide articles, and the like without limitation. The binder system can further be suitable for non-cordierite based ceramic honeycomb body production.

[0058] In embodiments, the inorganic batch components and the organic batch components are selected in conjunction with a specific firing cycle so as to yield a ceramic article comprising a predominant cordierite crystalline phase with a specific microstructure. However, it should be understood that, after firing, the ceramic article can also comprise small amounts of mullite, spinel, and/or mixtures thereof. For example, and without limitation, in some embodiments, the ceramic article comprises at least 90% by weight, or even at least 95% by weight, or even at least 98% - 99% by weight of a cordierite crystalline phase, as measured by x-ray diffraction. The cordierite crystalline phase produced consists essentially of, as characterized in an oxide weight percent basis, from about 49% to about 53% by weight SiCh, from about 33% to about 38% by weight AI2O3, and from about 12% to about 16% by weight MgO. Moreover, the cordierite crystalline phase stoichiometry approximates Mg2A14Si50is. The inorganic ceramic precursors of the batch mixture can be appropriately adjusted to achieve the aforementioned oxide weights within the cordierite crystalline phase of the ceramic article. [0059] In embodiments, the batch mixtures comprise from about 35% to about 45% by weight of talc based on the total weight of the inorganic ceramic precursors. In embodiments, the batch mixtures comprises from about 38% to about 43% by weight of talc, which is based on the total weight of inorganic ceramic precursors in the batch mixture. The talc can have a relatively fine particle size. For example, in embodiments, the talc has a mean particle diameter dptso of less than or equal to about 10 microns, less than or equal to about 9 microns, less than or equal to about 8 microns, less than or equal to about 6 microns, or even less than or equal to about 5 microns. In embodiments, the talc has a mean particle size dptso in the range from about 3 microns to about 10 microns, such as from about 8 microns to about 10 microns. All particle sizes described herein are measured by a particle size distribution (PSD) technique, such as by a SEDIGRAPH™ particle size analyzer by Micrometrics..

[0060] In embodiments, the amount of the silica source in the batch mixture is from about 13% to about 24% by weight based on the total weight of inorganic ceramic precursors in the batch mixture. In embodiments, the amount of the silica source in the batch mixture can be from about 15% to about 18% by weight based on the total weight of inorganic ceramic precursors in the batch mixture. The silica source generally has a fine particle size. For example, in some embodiments, the silica source has a mean particle diameter d_pS5o of less than or equal to 20 microns, less than or equal to 15 microns, or even less than or equal to 10 microns. In one embodiment, the silica source is a microcrystalline silica, such as but not limited to Imsil® A-25 microcrystalline silica. However, it should be understood that other silica sources can be used. For example, other suitable silica sources include fused silica; colloidal silica; or crystalline silica such as quartz or crystobalite.

[0061] In embodiments, the batch mixtures can comprise from about from about 20% to about 35% by weight alumina source based on the total weight of inorganic ceramic precursors in the batch mixture. In embodiments, the batch mixture comprises from about 22% to about 33% by weight alumina source, or from about 26% to about 29% by weight alumina source, based on the total weight of inorganic ceramic precursors in the batch mixture. The alumina source generally has a fine particle size. For example, in some embodiments, the alumina source has a mean particle diameter d_pa5o of less than or equal to 10 microns, less than or equal to 8 microns, or even less than or equal to 6 microns. Exemplary alumina sources can comprise any aluminum oxide or a compound containing aluminum which, when heated to a sufficiently high temperature, yields essentially 100% aluminum oxide, such as alpha-alumina and/or hydrated alumina. Non-limiting examples of alumina sources include corundum, gammaalumina, transitional aluminas, or combinations of these. In embodiments, the alumina source can comprise an aluminum hydroxide, examples of which can comprise but are not limited to gibbsite and bayerite, boehmite, diaspore, aluminum isopropoxide, and the like. If desired, the alumina source can also comprise a dispersible alumina source. As used herein, a dispersible alumina source is one that is at least substantially dispersible in a solvent or liquid medium and that can be used to provide a colloidal suspension in a solvent or liquid medium. In embodiments, a dispersible alumina source can be a relatively high surface area alumina source having a specific surface area of at least 20 m²/g, at least 50 m²/g, or even at least 100 m²/g. A suitable dispersible alumina source comprises alpha aluminum oxide hydroxide (AIOOH.X.H2O) commonly referred to as boehmite, pseudoboehmite, and as aluminum monohydrate. In alternative embodiments, the dispersible alumina source can comprise the so- called transition alumina or activated alumina (i.e., aluminum oxyhydroxide and chi, eta, rho, iota, kappa, gamma, delta, and theta alumina) which can contain various amounts of chemically bound water or hydroxyl functionalities.

[0062] In embodiments, the batch mixtures further comprises clay. The amount of clay in the batch mixtures can be from about 0% (zero %) to about 20% by weight, from greater than 0% (zero %) to about 20% by weight, from about 10% to about 18% by weight, or even from about 12% to about 16% by weight based on the total weight of the inorganic ceramic precursors in the batch mixture. When included in the batch mixture, the clay generally has a mean particle size d_pC5o of less than or equal to 10 microns, such as less than or equal to 5 microns, or even less than or equal to 3 microns. Suitable clays that can be included in the batch mixtures include, without limitation, raw kaolin clay, calcined kaolin clay, and/or mixtures thereof. Exemplary and non-limiting clays include non-delaminated kaolinite raw clay and delaminated kaolinite.

[0063] In embodiments, the inorganic ceramic precursors can comprise any other ceramic precursors suitable for making ceramics. In the embodiments described herein, the inorganic ceramic precursors of the batch mixture (i.e., talc, silica, alumina, clay, etc.) have a mean inorganic particle size dsoip less than or equal to 15 microns.

[0064] As described hereinabove, in embodiments, the batch mixtures can comprise organic pore former constituents such as relatively fine pore formers. In embodiments, an organic pore former can be added to the batch mixture in an amount sufficient to create a relatively high pore number density with a relatively small mean pore size and a relatively narrow pore size distribution. In embodiments, the batch mixture can comprise greater than or equal to about 30% by weight of an organic pore former based on the total weight of the inorganic ceramic precursors in the batch mixture. In embodiments, the amount of pore former added to the batch mixture is greater than about 35% by weight, greater than or equal to about 40% by weight, greater than or equal to about 50% by weight, greater than or equal to about 55% by weight, or even greater than or equal to about 60% by weight based on the total weight of the inorganic ceramic precursors in the batch mixture. It should be understood that, increasing the amount of pore formers in the batch mixture increases the pore number density of the porous ceramic honeycomb article after firing. In embodiments, the organic pore formers generally have a mean particle size d_PP5o less than or equal to 25 microns, less than or equal to 20 microns, less than or equal to 15 microns, or even less than or equal to 10 microns. The organic pore former can be a cross-linked pore former (i.e., cross-linked starches and the like) or un-cross-linked pore former. Examples of suitable pore forming materials include, without limitation, cross-linked corn starch, cross-linked wheat starch, cross-linked potato starch, uncross-linked potato starch, un-cross-linked corn starch, green bean starch, and pea starch. Organic pore formers can further include graphite.

[0065] The inorganic ceramic precursors are combined with the binder system and mixed together to produce the batch mixture. In embodiments, the batch mixture also comprises one or more of the pore formers previously discussed herein. The binder system comprises the binder, the liquid vehicle, and one or more processing aids, such as but not limited to a lubricant material.

[0066] The binder can comprise an organic binder. Suitable organic binders include water- soluble cellulose ether binders such as methylcellulose, hydroxypropyl methylcellulose, methylcellulose derivatives, hydroxy ethyl acrylate, polyvinylalcohol, and/or any combinations thereof. In embodiments, the binder is methylcellulose, methylcellulose derivatives, or a combinations of both. The binder is present in the batch mixture as a super addition in an amount in the range of from about 0.1% to about 15% by weight based on the total weight of the inorganic ceramic precursors in the batch mixture. In embodiments, the organic binder can be present in the batch mixture as a super addition in an amount in the range of from about 0.1% to about 10%, from about 0.1% to about 8%, from about 0.1% to about 6%, from about 2% to about 15%, from about 2% to about 10%, from about 2% to about 8%, from about 2% to about 6%, from about 4% to about 15%, from about 4% to about 10%, from about 4% to about 8%, or even from about 4% to about 6% by weight based on the total weight of the inorganic ceramic precursors. The amount of the binder in the batch mixture can be expressed in percent by volume, which is the true volume of the binder divided by the total true volume of the inorganic ceramic precursors in the batch mixture times 100. In embodiments, the batch mixture can comprise from about 0.3% to about 45%, from about 0.3% to about 30%, from about 0.3% to about 25%, from about 0.3% to about 20%, from about 5% to about 45%, from about 5% to about 30%, from about 5% to about 25%, from about 5% to about 20%, from about 11% to about 45%, from about 11% to about 30%, from about 11% to about 25%, or even from about 11% to about 20% binder by volume. Incorporation of the organic binder into the batch mixture allows the batch mixture to be readily extruded. [0067] As previously discussed, the binder system can comprise at least one liquid vehicle, which is included to provide a flowable or shapable consistency to the batch mixture. The liquid vehicle can comprise a solvent, such as but not limited to water. Although the batch mixtures discussed herein comprise water as the liquid vehicle, it should be understood that other liquid vehicles exhibiting solvent action with respect to suitable organic binders can be used alone or in combinations with water. The amount of the liquid vehicle in the batch mixture can be adjusted to modify handling properties of the batch mixture or to improve compatibility with other components of the batch mixture. The liquid vehicle is included in the batch mixture as a super addition to the batch mixture in an amount in the range from about 20% to about 50% by weight based on the total weight of the inorganic ceramic precursors in the batch mixture, such as from about 20% to about 35% by weight or from about 25% to about 35% by weight based on the total weight of the inorganic ceramic precursors in the batch mixtures. In embodiments, the liquid vehicle comprises water. The batch mixtures can include from about 20% to about 50% water, based on the total weight of the ceramic precursors in the batch mixture. In embodiments, the batch mixture includes from about 20% to about 36%, from about 20% to about 34%, from about 29% to about 50%, from about 29% to about 36%, from about 29% to about 34%, from about 30% to about 50%, or even from about 30% to about 36% water by weight based on the total weight of the ceramic precursors in the batch mixture.

[0068] The amount of the liquid vehicle in the batch mixture may be expressed in percent by volume, which is the true volume of the liquid vehicle divided by the total true volume of the inorganic ceramic precursors in the batch mixture times 100. In embodiments, the batch mixture can comprise from about 55% to about 140%, from about 55% to about 105%, from about 55% to about 97%, from about 80% to about 140%, from about 80% to about 105%, from about 80% to about 97%, from about 85% to about 140%, or even from about 85% to about 105% by volume water.

[0069] In addition to the liquid vehicle and binder, the binder system can comprise one or more processing aids, which are added to the batch mixture to stiffen the batch while allowing extrusion at lower pressures and torques. In conventional batch mixtures, the non-solvent processing aids are typically non-miscible organic oils, such as mixtures of polyalphaolefin oils (PAO oils) and fatty acids. As used in the present disclosure, the term “non-miscible organic oils” refers to organic compounds that are insoluble in water over the operating temperatures of the extrusion process, such as having a solubility in water of less than 0.1 wt.% over a temperature range of from 5 °C to 60 °C.

[0070] As used herein, the term “PAO oils” refers to oils that are produced through synthesizing oligomers from alpha olefin monomers and consist of low molecular weight polymers comprising a small number of repeat units derived from the alpha olefin monomers. The polyalphaolefin oils provide increased stiffness to the batch by occupying space in the batch without interacting significantly with the binder (e.g., methylcellulose, methylcellulose derivatives, or other binders). The fatty acids are included to provide lubricity, as the fatty acids are surface active and can reduce friction and increase slip at the wall surfaces. These nonsolvent processing aids have to be removed from the batch mixture during firing of the extrudates, and this can lengthen the firing cycle. In addition, non-miscible organic oils, such as the PAO oils and fatty acids, can bum out of the batch mixture during firing through charring, if not removed properly during the appropriate stage of firing. Charring can cause defects in the finished ceramic articles if they are not completely removed in the correct portion of the firing schedule.

[0071] These non-miscible organic oils can also cause a variety of other unwanted problems, both in forming and in the dryers, prior to firing. Non-miscible organic oils can separate from the batch mixture and accumulate in the extrusion equipment. Sufficient buildup of accumulated non-miscible organic oils overtime can lead to streaks of these non-miscible organic oils on the surfaces of the extrudates and the ceramic articles produced therefrom. These oil streaks can further lead to the formation of unwanted surface defects, namely oil fissures, as the surface oil leads to differential drying of one region of the extrudate over another. Being mobile species, these non-miscible organic oils may evaporate in the drying, potentially causing pollution issues and/or increasing the risk of fire hazards.

[0072] The batch mixtures of the present disclosure solve these problems by replacing the non-miscible organic oils, such as the PAO oils and fatty acids, with a lubricant material that is partially miscible in the liquid vehicle at a temperature or temperature range that is within an operating temperature range of the extrusion equipment used for extruding the batch mixture to form the ceramic extrudates. As used herein, the term “partially miscible” in water means that a first portion of the lubricant material that is less than the total amount of the lubricant material is soluble in the liquid vehicle (e.g., water) and a second portion of the lubricant material is insoluble in the liquid vehicle and forms a second phase separate from the first phase comprising the liquid vehicle.

[0073] Partial miscibility of the lubricant material in the liquid vehicle may cause at least a portion of the lubricant material to form the second phase at the boundary of the batch mixture and the inner surfaces of the extrusion equipment, the die, or both. Batch mixtures comprising the lubricant materials disclosed herein achieve equivalent or better performance compared to batch mixtures comprising fatty acids and PAO oils with respect to wall drag and tensile properties of the extrudates. However, the partial miscibility of the lubricant materials disclosed herein reduces the amount of the second phase, which reduces or prevents the accumulation of the second phase within the extrusion equipment and reduces the probability of uneven distribution of the second phase throughout the batch mixture. With no accumulation of a second oil phase within the extrusion equipment and subsequent surface streaking, the formation of oil fissures in the finished ceramic articles is reduced or prevented. Thus, the lubricant materials that are partially miscible in the liquid vehicle can achieve similar or improved batch performance compared to fatty acids and PAO oil without the adverse properties caused by the uneven distribution and/or segregation of the oil phase throughout the batch mixture.

[0074] In the batch mixtures disclosed herein, the liquid vehicle can be water. The lubricant material is present within the aqueous phase and serves to occupy space while not significantly altering the hydration rate of the methylcellulose-based binder in an adverse way. However, just enough of the lubricant material occupies the second phase, separate from the aqueous phase and, therefore, is able to act as a boundary lubricant between the batch mixture and the inner surfaces of the extrusion equipment and dies. Because the lubricant material is mostly miscible with the aqueous phase, any lubricant material that comes out into the second phase may return to the aqueous phase later.

[0075] The lubricant materials that are partially miscible in the aqueous phase can reduce wall drag during extrusion, which can reduce extrusion pressure and torque during extrusion, as compared to conventional batch mixtures comprising fatty acids and PAO oils as processing aids. This can lead to increased extrusion rates and cost savings through increased throughput rates. The lubricant materials disclosed herein can also enable deliberate tuning of wall drag to be compatible with process equipment capabilities and equipment aging, while maintaining other attributes of the extrudates, such as tensile strength. The lubricant materials disclosed herein can increase batch stiffness, which increases shape retention of the extrudates and reduces collapse. The lubricant materials disclosed herein may also enable increasing the solids content and decreasing organics content of the batch mixtures. The lubricant materials disclosed herein can reduce or prevent oil fissures and other surface defects and can reduce the firing cycle, which can reduce cost and waste. The lubricant materials that are partially miscible in an aqueous phase are often oxidized to a greater degree compared to the fatty acids and PAO oils. This greater degree of oxidation of the lubricant materials disclosed herein can reduce the firing time or temperature required to burn-out the lubricant materials, among other features.

[0076] The lubricant materials are non-reactive with the water and non-reactive with the binder. In embodiments, the liquid vehicle is water and the lubricant material is a water miscible material that is partially miscible in water at a temperature or temperature range that is within the operating temperature range of the extrusion equipment used to extrude the batch mixture to produce the ceramic extrudates. In particular, in embodiments, the lubricant material is partially miscible in water at a temperature or temperature range that is within the operating temperature range of from 5 °C to 60 °C for the extrusion equipment. In embodiments, the lubricant material is partially miscible in water over the temperature range of from 5 °C to 60 °C.

[0077] In embodiments, the lubricant material is partially miscible over a range of temperatures that is narrower than the operating temperature range of from 5 °C to 60 °C for the extrusion equipment. If the temperature limit of partial solubility at which the lubricant material becomes entirely immiscible in water is within the operating temperature range of from 5 °C to 60 °C, the lubricant material may still be effective in producing sufficient lubrication to prevent extrusion parameters, such as extrusion temperature, extrusion pressure, back-up length, and torque from exceeding operational limits.

[0078] Similarly, if the temperature limit of partial solubility at which the lubricant material becomes entirely miscible in water is within the operating temperature range of from 5 °C to 60 °C, the lubricant material may not form the lubricating second phase at lower temperature. However, at these lower temperatures, lubrication may not be needed in certain parts of the extrusion system (e.g., parts of the extrusion system experiencing those lower temperatures) as long as the lack of lubrication does not cause the operating parameters of the extrusion process, such as pressure, back-up length, and torque, to exceed operational limits. It is only in certain parts of the extrusion equipment (e.g., parts experiencing the greatest amount of friction with the batch mixture) where the degree of lubrication effects the ability to maintain the system within operational limits. At these points, it is important to have a partially miscible system, even if at other locations in the system there is simultaneously a fully miscible or fully immiscible local condition. In embodiments, the lubricant material is partially miscible over a narrow temperature range. In these embodiments, the extrusion equipment can comprise additional temperature control systems to maintain the temperature of the batch mixture within the partial solubility range of the lubricant material in the high-friction regions of the extrusion equipment.

[0079] The batch mixtures herein can comprise an amount of the lubricant material partially miscible in the liquid vehicle (e.g., water) that is sufficient to provide lubrication between the batch material and the extrusion equipment. The batch mixtures herein can comprise greater than or equal to about 1%, greater than or equal to about 2%, or even greater than or equal to about 3% lubricant material by weight based on the total weight of inorganic ceramic precursors in the batch mixture. The batch mixtures herein can comprise less than or equal to about 15%, less than or equal to about 10%, or even less than or equal to about 8% lubricant material by weight based on the total weight of inorganic ceramic precursors in the batch mixture. In embodiments, the batch mixtures herein can comprise from about 1% to about 15% or from about 3% to about 8% lubricant material by weight based on the total weight of inorganic ceramic constituents in the batch mixture. In embodiments, the batch mixture can comprise an amount of the partially miscible lubricant material that is less than or equal to 100%, less than or equal to 90%, or even less than or equal to 80% of the total amount of PAO oil and fatty acids in a comparative batch mixture comprising PAO oil and fatty acid as processing aids, while providing the same or reduced wall drag and comparable tensile properties of the extrudates.

[0080] The amount of the lubricant material in the batch mixture may be expressed in percent by volume, which is the true volume of the lubricant material divided by the total true volume of the inorganic ceramic precursors in the batch mixture times 100. The batch mixtures can comprise greater than or equal to about 2%, greater than or equal to about 5%, or even greater than or equal to about 8% by volume lubricant material. The batch mixtures can comprise less than or equal to about 42%, less than or equal to about 28%, or even less than or equal to about 22% by volume lubricant material. In embodiments, the batch mixtures can comprise from about 2% to about 42% or from about 5% to about 22% by volume lubricant material.

[0081] In embodiments, the lubricant material has a solubility in water that is inversely proportional to temperature, such that when the temperature increases, the solubility of the lubricant material in water decreases. In embodiments, the lubricant material is poly(propylene) glycol (PPG). PPG has a solubility in water that is inversely proportional to temperature. When the batch mixture comprises PPG as the lubricant material, the majority of the PPG (e.g., >50%) can be present within the aqueous phase and serves to occupy space while not significantly and adversely altering the hydration rate of the methylcellulose-based binder. Due to the partial solubility of the PPG in water, just enough of the PPG occupies a second phase and, therefore, is able to act as a boundary lubricant. Because the PPG is mostly miscible with the aqueous phase, any of the PPG that comes out of the aqueous phase to form the second phase may return to the water phase later, when the temperature decreases.

[0082] Without wishing to be bound by theory, the mechanism of action is believed to be the variable solubility of the PPG in the aqueous phase. The PPG is not 100% miscible with the aqueous phase at all concentrations and temperatures. One of the properties that makes PPG suitable for the lubricant material of the present disclosure is that the solubility of PPG in water decreases with increasing temperature. Referring now to FIG. 10, the temperatureconcentration phase diagrams for PPG having molecular weight of 1000 Daltons (Ref. No. 1002) and PPG having molecular weight of 2000 Daltons (Ref. No. 1004) in water are graphically depicted. As shown in FIG. 10, the concentration of PPG in the aqueous phase increases with decreasing temperature for both grades of PPG.

[0083] As a result of the solubility of the PPG being inversely proportional to temperature, at locations within the extruding equipment where the operating temperatures are greater, the PPG becomes less soluble, and the second phase, which is the lubricating phase, increases in proportion. The increased second phase reduces friction, which reduces the amount of heating due to friction of the batch materials within the extrusion equipment. The reduced heating reduces the temperature, which in turn increases the solubility of the PPG in the aqueous phase. This reduces the amount of the second phase. Thus, the amount of the second phase is self- regulating as lower heating gives lower temperatures and more of the PPG dissolves into the aqueous phase, so reducing the proportion available to the second phase. Furthermore, when the extrudate exits the extruder and cools, essentially 100% of the PPG may become completely miscible with the aqueous phase and no second phase will exist to cause potential problems, such as development of oil fissures or other surface defects.

[0084] As discussed further herein, the addition of PPG to the batch mixture has been found to reduce wall drag, reduce overall extrusion pressure, and reduce torque in the extrusion equipment without adversely affecting the tensile properties of the extrudate compared to batch mixtures that comprise fatty acids and PAO oils as processing aids. For 1 : 1 replacement of the PAO oils and fatty acids in the batch mixture with PPG, batch mixtures comprising PPG produce a wall drag that is less than the wall drag of a batch mixture comprising the fatty acids and PAO oil by at least 10%, at least 20%, at least 25%, or even at least 30% at an extrusion velocity of greater than or equal to 0.1 inches per second when determined according to the wall drag rate sweep testing procedure described herein. Batch mixtures comprising PPG have also been found to produce extrudates having tensile properties comparable to extrudates prepared from batch mixtures comprising PAO oils and fatty acids.

[0085] The reduction in wall drag achieved with batch mixtures comprising the PPG results in reduced extrusion pressure and torque in the extrusion equipment compared to batch mixtures comprising PAO and fatty acids. This reduction in extrusion pressure and torque can enable greater throughput from the extrusion process. Also, the reduction in wall drag with the use of PPG was found to be significant enough to enable a lesser amount of lubricant material to be included in the batch mixtures compared to batch mixtures comprising fatty acid and PAO oils as processing aids. In particular, the batch mixtures of the present disclosure can comprise an amount of PPG that is less than 100%, less than or equal to about 90%, or even less than or equal to about 80% of the total amount of fatty acid and PAO oil needed to produces the same wall drag and comparable batch stiffness.

[0086] The molecular weight of the PPG depends on the number of repeating propylene glycol units in the PPG, and the intermolecular interactions of PPG with other constituents of the batch material are highly dependent on the molecular weight. PPGs with different molecular weights will interact with the water and the other batch constituents to different extents, due in part to the differences in hydrophilicity of the PPG. At molecular weights greater than about 2000 Daltons, PPG is not miscible in water. PPG with molecular weights of less than or equal to about 1000 Daltons are partially or fully miscibility with water and have different degrees of hydrophilicity and interaction with the other constituents of the batch mixture. For the batch mixtures herein, the PPG can have a number average molecular weight of less than or equal to 2000 Daltons, such as less than or equal to 1000 Daltons. In embodiments, the PPG has a number average molecular weight of from 400 Daltons to 2000 Daltons, such as from 400 Daltons to 1000 Daltons.

[0087] In embodiments, the batch mixture can comprise a single PPG having a number average molecular weight that provides the desired wall drag and tensile properties of the extrudate. The different molecular weights of PPG having different solubility in water and interacting differently with the other batch constituents may allow the specific properties of the batch mixture to be tuned by use of mixtures of PPGs having different molecular weights. In embodiments, the batch mixture comprise a plurality of PPGs, wherein each of the plurality of PPGs has a different number average molecular weight. In embodiments, the batch mixture can comprise PPG having a multi-modal molecular weight distribution, where the term “multimodal” refers to a molecular weight distribution having two or more peaks.

[0088] In embodiments, the lubricant material can comprise a mixture of two or more than two different PPGs, where each PPG has a different number average molecular weight. For instance, the lubricant material can comprise a mixture of PPGs having molecular weights of 425 Daltons, 725 Daltons, 1000 Daltons and combinations of these. In embodiments, the lubricant material can be a mixture of PPGs having a molecular weight of 425 Daltons and a PPG having a molecular weight of 1000 Daltons. In other embodiments, the lubricant material can be a mixture of PPGs having a molecular weight of 425 Daltons and a PPG having a molecular weight of 725 Daltons. In still other embodiments, the lubricant material can be a mixture of a PPG having a molecular weight of 425 Daltons, a PPG having molecular weight of 725 Daltons, and a PPG having a molecular weight of 1000 Daltons. Although described in terms of PPGs having molecular weights of 425 Daltons, 725 Daltons, and 1000 Daltons, it is understood that any grade of PPG having molecular weight from 400 Daltons to 2000 Daltons can be incorporated into a mixture of PPGs to fine-tune the properties of the batch mixture.

[0089] The wall drag, extrusion pressure, torque, back-up length, and combinations of these can be modified by changing the molecular weights of the different PPGs in the mixture of PPGs comprising the lubricant material while maintaining the same batch volume. The wall drag, extrusion pressure, torque, back-up length, and combinations of these can also be modified by changing the ratios of the different PPGs in the mixture of PPGs comprising the lubricant composition while maintaining the same batch volume. Because the PPGs having different molecular weights can be mixed in any combination and ratio, this allows the wall drag to be tuned to match system requirements. The ability to fine-tune the wall drag can enable the batch mixture to be modified to account for changing geometry of the die and extrusion equipment due to wear and aging of the extrusion equipment. The changing surface characteristics of the extrusion equipment can potentially be compensated for by small adjustments to the molecular weights or ratios of the different PPGs in the lubricant material to maintain constant extrusion performance through the lifetime of the die and extrusion equipment.

[0090] Again, without wishing to be bound by theory, it is believed that the means by which the different molecular weights of PPG are able to produce different levels of wall drag in the extrusion of the batch mixtures is two-fold. Primarily, it is believed that the means by which the different molecular weights of PPG are able to produce different levels of wall drag is associated with the different miscibilities of the various PPGs with water. The shorter (lower molecular weight) PPGs have a higher miscibility with water and therefore exhibit a smaller second phase, which results in less material to lubricate the movement of particles past each other and the surfaces of the extrusion equipment. Secondarily, the shorter (lower molecular weight) PPGs will have a slightly lower intrinsic lubricating capacity.

[0091] The batch mixtures herein can comprise an amount of PPG sufficient to provide lubrication between the batch material and the extrusion equipment. The batch mixtures can comprise greater than or equal to about 1%, greater than or equal to about 2%, or even greater than or equal to about 3% PPG by weight based on the total weight of inorganic ceramic precursors in the batch mixture. The batch mixtures can comprise less than or equal to about 15%, less than or equal to about 10%, or even less than or equal to about 8% PPG by weight based on the total weight of inorganic ceramic precursors in the batch mixture. In embodiments, the batch mixtures can comprise from about 1% to about 15% or from about 3% to about 8% PPG by weight based on the total weight of inorganic ceramic precursors in the batch mixture. In embodiments, the batch mixture can comprise an amount of PPG that is less than 100%, less than about 90%, or even less than or equal to about 80% of the total amount of PAO oil and fatty acids in a comparative batch mixture comprising PAO oil and fatty acid as processing aids.

[0092] The amount of the PPG in the batch mixture can be expressed in percentage by volume, which is the true volume of the PPG divided by the total true volume of the inorganic ceramic precursors in the batch mixture times 100. The batch mixtures can comprise greater than or equal to about 2%, greater than or equal to about 5%, or even greater than or equal to about 8% by volume PPG. The batch mixtures can comprise less than or equal to about 42%, less than or equal to about 28%, or even less than or equal to about 22% by volume PPG. In embodiments, the batch mixtures can comprise from about 2% to about 42% or from about 5% to about 22% by volume PPG.

[0093] In embodiments, the binder system, the batch mixture, or both do not include a non- miscible organic oil that is immiscible with the liquid vehicle, such as water, over the entire temperature range of 5 °C to 60 °C. In embodiments, the binder system, batch mixture, or both does not include a fatty acid or a PAO oil. As previously discussed, the PAO oil, fatty acid, or both form a second phase that can accumulate in the extrusion equipment to cause streaking and oil fissures in the ceramic articles produced.

[0094] In embodiments, the batch mixtures can comprise one or more other additives, such as but not limited to one or more plasticizers, surfactants, dispersants, or combinations thereof. In embodiments, the batch mixture can comprise one or more additives selected from the group consisting of plasticizers, surfactants, dispersants, and combinations thereof.

[0095] The lubricant materials disclosed herein are incorporated into a method for producing a ceramic article. The methods for forming ceramic articles herein comprise forming the batch mixture comprising at least one inorganic ceramic precursor and the binder system. The inorganic ceramic precursor can comprise any of the ceramic precursors previous discussed herein. The binder system comprises the binder comprising methylcellulose, methylcellulose derivative, or combinations of these; the liquid vehicle (e.g., water or other solvent); and the lubricant material that is partially miscible in the liquid vehicle at a temperature that is within an operating temperature range of the extrusion equipment for producing a ceramic extrudate. In embodiments, the batch mixture further comprises pore formers or other additives, as previous described herein. [0096] The methods can further comprise extruding the batch mixture to produce the ceramic extrudate. The lubricant material in the batch mixture reduces extrusion pressure and torque in the extrusion equipment during extrusion. The methods further comprise firing the ceramic extrudate under conditions sufficient to produce the ceramic article. The partial miscibility of the lubricant material in the liquid vehicle reduces accumulation of the second phase in the extrusion equipment, thereby reducing oil fissures and other defects in the ceramic article typically resulting from the use of non-miscible organic oils, such as fatty acids and PAO oils. The methods disclosed herein can further comprise washcoating and calcining the ceramic article. The methods disclosed herein can further comprise thermally treating the ceramic article.

[0097] In embodiments of the methods, the lubricant material has a solubility in the liquid vehicle that is inversely proportional to the temperature. In embodiments, the lubricant material is self-regulating, meaning that as the drag in the extrusion equipment increases, the temperature increases, which decreases the solubility of the lubricant material in the liquid vehicle, which increases the amount of lubricant material at the wall of the extrusion device, which then reduces the drag on the wall, reducing the temperature that further increases the solubility of the lubricant material in the liquid vehicle. In embodiments, the lubricant material is PPG having a number average molecular weight of from 400 Daltons to 2000 Daltons. In embodiments, the lubricant material comprises a mixture of PPG having different molecular weights. In embodiments, the method can comprise adjusting an average molecular weight, the molecular weight distribution, or both of the PPG to adjust the wall drag, tensile properties, or both of the ceramic extrudate.

[0098] The batch mixtures of the present disclosure can be prepared by combining the inorganic ceramic precursors, binders, the liquid vehicle, lubricant materials, pore formers, and other additives. The constituents of the batch mixture are mixed together in a mixer, such as but not limited to a Littleford mixer, and kneaded for approximately 5-20 minutes to produce a batch mixture having the desired formability and green strength to permit the batch mixture to be shaped into an extrudate.

[0099] The resulting batch mixture can then shaped into a green body (e.g., a green honeycomb article) by conventional ceramic forming processes, such as, for example, extrusion. When the green body is formed by extrusion, the extrusion can be performed using a hydraulic ram extrusion press, or alternatively, a two stage de-airing single auger extruder, or a twin screw mixer with a die assembly attached to the discharge end. When formed by an extrusion process, the green body is referred to herein as an extrudate. The methods disclosed herein can comprise extruding the batch mixture with the extrusion equipment to produce the extrudates, and measuring one or more operating conditions of the extruding equipment. In embodiments, the lubricant material is PPG or a mixture of PPGs of different molecular weights, and the methods further comprise adjusting an amount, a number average molecular weight, a molecular weight distribution, or combinations thereof of the PPG(s) based on the measured values of the one or more operating conditions. The operating conditions can comprise one or more of an extrusion rate, an extrusion pressure, an extrusion temperature, a back-up length , work imparted to the batch (e.g., torque for single or dual screw extruders), or combinations of these. The back-up length refers to the length of the zone in an extruder where the batch mixture exhibits a 100% degree of fill.

[00100] After the batch mixture has been formed into the ceramic extrudate, the extrudate is then dried to remove excess liquid from the extrudate. Suitable drying techniques include microwave drying, hot air drying, RF drying, or various combinations thereof. After drying, the extrudate is placed in a kiln or furnace and fired under conditions effective to convert the extrudate into the ceramic article comprising a primary cordierite crystalline phase, as described herein. In embodiments, the ceramic article is the porous ceramic honeycomb article 100.

[00101] It should be understood that the firing conditions utilized to convert the extrudates into the ceramic articles can vary depending on the process conditions such as, for example, the specific composition, size of the extrudate, and nature of the equipment used. To that end, in one aspect, the firing conditions specified herein may need to be adapted (i.e., slowed down) for very large cordierite structures, for example.

[00102] The firing schedules utilized to produce the ceramic articles, such as the porous ceramic honeycomb articles 100, having the properties described herein can ramp the temperature of the extrudates quickly from about 1200 °C to a maximum hold temperature greater than or equal to about 1420 °C, or even greater than or equal to about 1425 °C. The quick ramp rate can be greater than or equal to about 50 °C/hr or even greater than or equal to about 75 °C/hr. In embodiments, the green bodies can be held at the maximum hold temperature for from about 5 to about 20 hours, such as from about 10 hours to about 15 hours. In embodiments, the green bodies can be fired at a maximum hold temperature in the range of from about 1420 °C to about 1435 °C, or even from about 1425 °C to about 1435 °C. In embodiments, the firing cycle comprises a quick ramp rate of 50 °C/hr or higher from about 1200 °C and the maximum hold temperature in the range from about 1420 °C to about 1435 °C for a sufficient time to form the cordierite crystalline phase in the ceramic article. The total firing time can range from approximately 40 to 250 hours, depending on the size of the extrudate fired. During the total firing time, the temperature of the extrudate is ramped up to the maximum hold temperature and held for a period of time sufficient to form the cordierite crystalline phase. In embodiments, the firing schedule can comprise ramping from 1200 °C at a rate above 50 °C/hour and firing at a soak temperature of between about 1425 °C and 1435 °C for between about 10 hours to about 15 hours.

[00103] In embodiments, the firing schedule can comprise a first firing period, during which the extrudate is fired from about room temperature to a pore former burnout temperature at an average firing rate of from about 20 °C/hour and about 70 °C/hour. The first firing period of the firing schedule can comprise a pore former burnout stage, which can be a hold or slight ramp within the range of pore former burnout temperatures to minimize cracking and temperature differentials between the skin and the core of the honeycomb. In embodiments of the firing schedule, the burnout stage can be followed by an intermediate ramp, during which the extrudate is ramped from the pore former burnout temperature to a temperature of about 1200 °C. An upper portion of the firing schedule comprises a relatively faster ramp rate at temperatures above 1200 °C. This fast ramp in the upper portion of the firing schedule can be coupled with a hold portion at a temperature above about 1420 °C, or even at or above about 1425 °C, such as a temperature of from 1420 °C to 1435 °C. The cordierite crystalline phase of the ceramic articles is formed during this hold portion. The ramp rate in the upper portion 0 of the firing schedule can be greater than or equal to about 50 °C/hour, greater than or equal to about 75 °C/hour, greater than or equal to about 100 °C/hour, or even greater than or equal to about 120 °C/hour. By utilizing the faster ramp rate in the upper portion of the firing schedule (e.g., above about 1200 °C) and the relatively high hold temperature (e.g., above 1420 °C), unique microstructure characteristics of the fired ceramic body may be achieved, as will be described in more detail herein. [00104] In particular, the firing cycle described herein can aid in reducing the relative amount of fine porosity present in the fired ceramic honeycomb article to below about 4.0 microns. Without being bound by any particular theory, it is believed that the reduction mechanism is thought to be from the promotion of viscous flow of the cordierite forming components such that fine pores are filled by the viscous flow of the components during the initial formation of the cordierite phase. Following the fast ramp, the honeycomb is held at the hold temperature for a suitable time, such as from 5 hours to 20 hours, to form the cordierite phase. After this, the honeycomb article is cooled to room temperature in a cooling portion of the firing schedule. The cooling rate is slow enough to prevent cracking and is dependent on the size of the ceramic article being fired. The firing schedule can be modified depending on the particular inorganic ceramic precursors used and the type of ceramic article being produced. [00105] In some embodiments described herein, the ceramic articles, such as the porous ceramic honeycomb article 100, can be washcoated with a catalyst washcoat after firing. For example, a slurry of a particulate catalyst washcoating composition can be applied to the surfaces (both internal and external) of the porous ceramic honeycomb article 100. For example, in embodiments, the catalyst washcoat can have a catalytic function that promotes catalytic reactions involving the reduction of NO_X and/or the oxidation of CO, hydrocarbons, and NO in an exhaust gas stream which is directed through the porous ceramic honeycomb article 100. Thus, it should be understood that, in addition to acting as a particulate filter, the porous ceramic honeycomb articles 100 described herein can also exhibit catalyst functionalities and, as such, may be utilized as a 4-way filter de-NO_x integrated filter (NIF).

[00106] In embodiments, the primary particulate component of the washcoating slurry is alumina. In other embodiments, the primary particulate component of the washcoating slurry is a zeolite, such as Fe-ZSM-5 which can be incorporated in water in an amount from about 7 wt. % to about 12 wt. % to form a catalyst washcoat slurry. However, it should be understood that, in other embodiments, the catalyst washcoat can comprise a different primary particulate component. In embodiments, the catalyst washcoat additionally comprises a particulate catalyst such as, by way of example and not limitation, platinum, palladium, rhodium, or any other catalytic material and/or various alloys thereof. In embodiments, the porous ceramic honeycomb article 100 can optionally comprise a preliminary passivation coating applied to the porous ceramic honeycomb article 100 before the washcoating process. The preliminary passivation coating may prevent the washcoating material from becoming lodged in the microcracks, as is the case for more highly microcracked articles. In embodiments, the porous ceramic honeycomb article does not include a preliminary passivation coating.

[00107] Following application of the washcoat to the porous ceramic honeycomb article 100, the porous ceramic honeycomb article 100 can be exposed to a microcracking condition, which increases the number of microcracks per unit volume in the porous ceramic honeycomb article. In one embodiment, the microcracking condition is a thermal cycle. In this embodiment, the porous ceramic honeycomb article is heated to a peak temperature and then rapidly cooled. The heating and rapid cooling causes the porous ceramic honeycomb article to expand and contract thereby causing microcracks to nucleate and grow in the porous ceramic honeycomb article. In embodiments, the peak temperature of the thermal cycle is greater than or equal to about 400 °C, or even greater than or equal to about 600 °C. In embodiments, the peak temperature of the thermal cycle is in the range from about 400 °C to about 800 °C. After heating to the peak temperature, the porous ceramic honeycomb article is rapidly cooled at a rate of at least about 200 °C/hr, during which time microcracks are formed throughout the volume of the porous ceramic honeycomb article. By exposing the porous ceramic honeycomb article to the thermal cycle, the porous ceramic honeycomb article becomes a microcracked porous ceramic honeycomb article.

[00108] In other embodiments, the microcracking condition can be an acid wash. In these embodiments, the porous ceramic honeycomb article is immersed in an acid solution which precipitates the nucleation and growth of microcracks throughout the porous ceramic honeycomb article. In embodiments, the porous ceramic honeycomb article can be immersed in a solution having a pH of less than about 6, or even less than about 5, to cause further microcracking in the porous ceramic honeycomb article. By exposing the porous ceramic honeycomb article to the acidic solution, the porous ceramic honeycomb article becomes a microcracked porous ceramic honeycomb article.

[00109] As previously discussed, the ceramic articles can be the porous ceramic honeycomb articles 100. The porous ceramic honeycomb articles 100 have a thickness T of the porous channel walls 106 in units of mils (1/1000 inch or 25.4 microns) that is a function of the cell density of the porous ceramic honeycomb article 100 in cells per square inch (cpsi). In embodiments, the porous ceramic honeycomb article has a thickness T of the porous channel walls in a range from about (l l+(300-CD)*0.03) to about (8+(300-CD)*0.02), where CD is the density of the cells in cells per square inch (cpsi). In other embodiments, the thickness of the channel walls is in a range from about (10+(300-CD)*0.03) to about (6+(300-CD)*0.02), or in a range from about (12+(300-CD)*0.03) to about (8+(300-CD)*0.02). The porous ceramic honeycomb articles 100 has a cell density CD of less than or equal to about 400 cpsi, less than or equal to about 300 cpsi. The porous ceramic honeycomb articles 100 has cell density CD of greater than or equal to about 150 cpsi. In embodiments, the porous ceramic honeycomb articles 100 has a cell density CD of from about 150 cpsi to about 400 cpsi.

[00110] Reference may be made herein to the porous ceramic honeycomb article 100 having a "geometry" of A/B where A is the cell density CD of the porous ceramic honeycomb article 100 and B is the thickness T of the channel walls. By way of example and not limitation, a porous ceramic honeycomb article 100 having a 200/10 geometry has a cellular density of 200 cpsi and a cell wall thickness of 10 mils. In some embodiments, the porous ceramic honeycomb articles 100 have a geometry of 300/8, 300/10, or even 200/12. However, it should be understood that other geometries are possible.

[00111] The porous ceramic honeycomb articles 100 described herein generally have a relatively high total porosity (% P). In embodiments, the porous ceramic honeycomb articles 100 have a total porosity of from about 50% P to about 70% P, such as from about 55% P to about 65% P, from about 58% P to about 62% P, or even from about 62% P to about 65% P, as measured with mercury porosimetry.

[00112] The pores of the porous ceramic honeycomb article are highly connected within the channel-like domains of cordierite ceramic indicating an interpenetrated network structure. Accordingly, the morphology of the surface porosity taken in conjunction with the morphology of the total body porosity of the ceramic article is generally a bi-continuous morphology. In the embodiments, the cordierite domain size is generally greater than or equal to about 20 microns, greater than or equal to about 40 microns, or even greater than or equal to 60 microns. In embodiments, the cordierite domain size within the porous ceramic honeycomb article 100 is in the range from about 20 microns to about 80 microns.

[00113] The specific pore volume of the honeycomb article characterizes the total volume available inside the porous structure of the channels walls as a function of the porosity %P of the of the porous ceramic honeycomb article and the total volume of the channel walls present in the porous ceramic article, referred to herein as the open frontal area (OF A) of the porous honeycomb article. More specifically, the specific pore volume VP is related to the OFA and the porosity %P according to the relation in Equation 1 (EQU 1).

VP = (1 - OF A) X (%P) EQU. 1

[00114] The porous ceramic honeycomb articles 100 can have a relatively low specific pore volume VP. In embodiments, the porous ceramic honeycomb articles 100 have a specific pore volume less than or equal to 0.22, less than or equal to 0.20, less than or equal to 0.185, or even less than or equal to 0.18. In embodiments, the porous ceramic honeycomb articles 100 have a specific pore volume of from 0.14 to 0.22.

[00115] The bare surface porosity of the porous ceramic honeycomb articles 100, as measured by image analysis of SEM micrographs of the porous ceramic honeycomb articles 100 prior to washcoating, can be greater than or equal to 30%, greater than or equal to 35%, greater than or equal to 38%, greater than or equal to 40%, or even greater than or equal to 42%. The greater surface porosity yields a porous ceramic honeycomb article 100 with a greater permeability and a corresponding lower backpressure drop when used as a particulate filter in automotive and/or diesel applications. In embodiments, the porous ceramic honeycomb articles 100 have a surface porosity to total porosity ratio of greater than or equal to 0.5, greater than equal to 0.6, or even greater than or equal to 0.7.

[00116] The porous ceramic honeycomb articles 100 can have a mean pore diameter dso of less than or equal to 20 microns, less than or equal to 16 microns, or even less than or equal to 14 microns. In embodiments, the mean pore diameter dso of the porous ceramic honeycomb article are from about 12 microns to about 20 microns, from about 12 microns to about 16 microns, from about 12 microns to about 14 microns, from about 14 microns to about 20 microns, or even from about 14 microns to about 16 microns. Controlling the porosity such that the mean pore diameter dso is within these ranges limits the amount of very small pores and thereby minimizes the washcoated backpressure of the fired porous ceramic article.

[00117] In embodiments, the pore size distribution of the porous ceramic honeycomb article 100 comprises a dio value of greater than or equal to 5 microns or even greater than or equal to 8 microns. The quantity dio, as used herein, is the pore diameter at which 10% of the pore volume is comprised of pores with diameters smaller than the value of dio; thus, using mercury porosimetry techniques to measure porosity, dio is equal to the pore diameter at which 90% by volume of the open porosity of the ceramic has been intruded by mercury during the porosimetry measurement.

[00118] As used herein, the d-factor df of the porous ceramic honeycomb article 100 is a characterization of the relative width of the distribution of pore sizes that are finer than the mean pore size dso. The d-factor df is defined by the following Equation 2 (EQU. 2).

In EQU 2, dso and dio are as defined hereinabove. In the embodiments described herein, the pore size distribution of the open interconnected porosity of the porous walls of the porous ceramic honeycomb article 100 is relatively narrow such that df is less than or equal to 0.35, less than or equal to 0.3, less than or equal to 0.25, less than or equal to 0.22, or even less than or equal to 0.2. In some embodiments, the d-factor of the porous ceramic honeycomb articles is in a range from about 0.15 to about 0.35.

[00119] In embodiments, the porous ceramic honeycomb article 100 have a pore size distribution with a dw value of less than or equal to 45 microns, less than or equal to 35 microns, or even less than or equal to 30 microns. The quantity dw, as used herein, is the pore diameter at which 90% of the pore volume is comprised of pores with diameters smaller than the value of dgo; thus, using mercury porosimetry techniques to measure porosity, dgo is equal to the pore diameter at which 10% by volume of the open porosity of the ceramic has been intruded by mercury during the porosimetry measurement.

[00120] The ultra narrow pore size distribution of the porous ceramic honeycomb articles can also be characterized by the breadth dAbsb of the distribution of pore sizes that are both finer and coarser than the mean pore size dso. As used herein, dAbsb is defined by the following Equation 3 (EQU. 3). d-Absb ⁼ (^75 ^— ^25) EQU. 1

In EQU. 3, the quantity d25, as used herein, is the pore diameter at which 25% of the pore volume is comprised of pores with diameters smaller than the value of d25, and the quantity d?5, as used herein, is the pore diameter at which 75% of the pore volume is comprised of pores with diameters smaller than the value of d?5. The porous ceramic honeycomb articles described herein can have a pore size distribution exhibiting a dAbsb of less than or equal to 10 microns, less than or equal to 8 microns, or even less than or equal to 6 microns. Having a narrow breadth around the mean pore size value ensures that the majority of the pores and pore volume are within a desired range and that little volume of the porous ceramic honeycomb article 100 is lost to pores that are either too small or too large. It is believed that this narrow absolute breadth is expected to provide improved catalyst washcoat coatability as well as high permeability following coating with a catalyst washcoat (i.e., high efficiency in pore utilization for flow). [00121] In the embodiments described herein, the combined properties of the total porosity, the surface porosity, the mean pore diameter dso, the d-factor df, and the specific pore volume provide a porous ceramic honeycomb article 100 with a relatively high initial filtration efficiency in both the bare and coated conditions. In embodiments, the bare initial filtration efficiency can be greater than or equal to 50%, such as greater than or equal to 55%, greater than or equal to 60%, greater than or equal to 70%, or even greater than or equal to 90%. Similarly, in embodiments, the porous ceramic honeycomb article 100 can have a coated initial filtration efficiency greater than or equal to 50% after coating with a catalyst washcoat, such as greater than or equal to 55%, greater than or equal to 60%, greater than or equal to 70%, or even greater than or equal to 90% after coating with a catalyst washcoat.

TEST METHODS

[00122] Tensile Strength

[00123] Tensile tests for green extrudates are conducted using a 5969 strength tester available from INSTRON®. The tensile strength tests are conducted with a 50 lb load cell. The green extrudates are formed into dogbone- shaped test samples, each sample having a width of 5.8 mm, a gauge length of 35 mm, and the thickness of 3.5 mm.

[00124] Wall Drag

[00125] In the embodiments described herein, wall drag may be measured using a “rate sweep test” in which a batch mixture is simultaneously extruded through two dies in a capillary rheometer. An RH7 capillary rheometer available from Malvern Instruments Limited of England can be used for the rate sweep test. According to various embodiments, both dies have a 1 mm diameter circular opening. The first die on the right hand side can have a 0.25 mm length and the second die on the left hand side can have a 16 mm length such that the difference in pressure between the two dies can be attributed to wall drag. The pressure through the first die is referred to herein as Plight and the pressure through the second die is referred to herein as PLeft.

[00126] In various embodiments of the rate sweep test, wall drag or pressure is measured at a plurality of batch velocities and temperatures, and the PLeft (16 mm), Plight (0.25 mm), and the difference between the pressures (PLeft-PRight), which is indicative of wall drag, are plotted as a function of batch velocity, as shown in FIGS. 2-4 for example. In various embodiments, the capillary rheometer is set to a desired temperature, and the batch is extruded at a series of velocities from 0.01 in/s to 4 in/s, corresponding to batch velocities that occur during the extrusion process. The batch velocities are changed after a time period of about 3 minutes to enable the batch to reach a steady state at each velocity. Batch velocities can be changed, for example, using a programming unit that controls the speed with which the piston is pushed. The time between velocity changes can vary depending on the particular embodiment, but should be long enough to allow the pressure to stabilize following the change in velocity. After the pressure is measured at each of the desired batch velocities, the temperature is changed and the test is run again to determine the wall drag response to temperature for the batch.

EXAMPLES

[00127] The following examples are offered to illustrate specific embodiments of the porous ceramic honeycomb articles described above. It should be understood that the following examples are for purposes of description only and are not intended to limit the scope of the claimed subject matter.

[00128] For the purposes of evaluating the subject matter of the present disclosure, batch mixtures based on the composition used to make ultra-thin wall (2 mil web) cordierite substrates were prepared. Lab scale tests were conducted on batches of approximately 350 grams of inorganics content, which included the ceramic precursors. The inorganics and the binder were premixed by AMPL in 40 lb batches, to provide consistency across testing. The other liquid components comprising water and lubricating additives were added to 375 grams of premixed “masterbatch” and blended in a mixer. The resulting batch mixtures were then added to an INTELLI-TORQUE™ PLASTI-CORDER™ torque rheometer produced and marketed by BRAB ENDER® and mixed for 8 minutes. Each batch was then deaired for 10 minutes and extruded into either rods for rheometric analysis or ribbons for dogbone cutting and tensile testing. Table 1 provides the batch mixture of the control batch. [00129] All batches of the following Examples and Comparative Examples were evaluated for wall drag using an RH7 capillary rheometer available from Malvern Instruments Limited to conduct rate sweep tests, according to the test methods discussed herein. Some batches of the Examples and Comparative Examples were evaluated for tensile strength according to the test method previously discussed herein.

[00130] Comparative Example 1: Standard Control Batch

[00131] For Comparative Example 1, the control batch mixture in Table 1 was prepared according to the methods disclosed herein. In particular, the inorganic ceramic precursors and methylcellulose binder were premixed in a 40 pound batch. The liquid additives (e.g., oleic acid, PAO oil, and water) were then added to 375 grams of the inorganics and binder mixture and the batch mixture was mixed in a torque rheometer for 8 minutes, as previously discussed. The batch mixture was then de-aired for 10 minutes and then subjected to testing for wall drag and tensile strength according to the methods discussed herein. The drag testing was conducted at a temperature of 30 °C. The drag testing results for the batch mixture of Comparative Example 1 are graphically depicted in FIGS. 2-5 and 7, and are identified with reference numbers 200 (Pteft), 202 (PRight), and 204 (wall drag). The tensile strength of the extrudate prepared from the batch material of Comparative Example 1 is shown in FIG. 6 and identified by reference number 622.

Table 1

[00132] Examples 2 and 3: Direct Replacement of Oleic Acid and PAO Oil with Polypropylene Glycol

[00133] In Examples 2 and 3, the control batch in Table 1 was modified to entirely replace the oleic acid and PAO oil with polypropylene glycol (PPG) on a 1 : 1 basis to evaluate the performance of the PPG as a property modifier for ceramic batch material. In particular, the 0.81 wt.% oleic acid and 6.49 wt.% PAO oil were replaced by 7.3 wt.% PPG, where the weight percent is based on the total weight of inorganic ceramic precursors. The PPG for Example 2 had a molecular weight of 425 Daltons (PPG 425), and the PPG for Example 3 had a molecular weight of 725 Daltons (PPG 725). The batches for Examples 2 and 3 each had 32 wt.% water based on the total weight of inorganic ceramic precursors. The batch mixtures were prepared according to the preparation method described in Comparative Example 1. The batch mixtures for Examples 2 and 3 were then subjected to wall drag and tensile strength testing according to the test methods discussed herein.

[00134] Referring now to FIG. 2, the rate sweep testing data for the batch mixtures of Examples 2 and 3 compared to the control batch of Comparative Example 1 are graphically depicted. The rate sweep testing was conducted at 30 °C over a range of velocities of from 0.0 to 4 inches per second. The rate sweep testing data for Example 2 are indicated in FIG. 2 by reference numbers 210 (PLeft), 212 (Plight), and 214 (wall drag), and the rate sweep testing data for Example 3 are indicated in FIG. 2 by reference numbers 220 (PLeft), 222 (Plight), and 224 (wall drag). The pressure velocity curves from the rate sweep testing data in FIG. 2 shows that the PPG-based batch mixtures of Examples 2 and 3 have flatter pressure and wall drag profiles compared to the control batch of Comparative Example 1. This is indicative of greater shear thinning behavior of the PPG in Examples 2 and 3 compared to the oils in the control batch of Comparative Example 1. The greater molecular weight of the PPG 725 in Example 3 resulted in less pressure and less wall drag compared to the PPG 425 in Example 2. Thus, increasing the molecular weight of the PPG can further reduce pressure and wall drag.

[00135] Referring now to FIG. 6, the tensile strength of extrudates prepared from the batch mixture of Example 2 (ref. no. 602) and Example 3 (ref. no. 608) are graphically depicted. In FIG. 6, the tensile strength of the control batch of Comparative Example 1 is identified by reference number 622. As shown by FIG. 6, the batch mixtures of Examples 2 and 3 both exhibited greater tensile strength compared to the control batch of Comparative Example 1. Even though the PPG-containing batch mixture of Examples 2 and 3 have less wall drag than the oil -containing control batch of Comparative Example 1, the PPG batch mixtures of Examples 2 and 3 also have greater stiffness than their oil -containing counterparts. Although this might be expected for compositions containing lower liquid volumes (e.g., Examples 4 and 5 below), this is true even with 1 : 1 replacements, such as in Example 2 and 3, where the volumes of liquids are the same as the control batch of Comparative Example 1. [00136] Thus, both of the batch mixtures of Examples 2 and 3 were found to be adequate to provide a significant drop in wall drag and overall pressure, without adversely impacting tensile properties.

[00137] Examples 4 and 5: Reduced Concentration of Polypropylene Glycol

[00138] Because the reductions in wall drag for Examples 2 and 3 were so significant, especially for PPG 725 of Example 3, the effects of reducing the amount of the PPG was investigated. In Examples 4 and 5, the total amount of the PPG was reduced to 80% of the amount of the oleic acid and PAO oil in the control batch of Comparative Example 1. In particular, the 0.81 wt.% oleic acid and 6.49 wt.% PAO oil of the control batch of Comparative Example 1 were replaced by 5.84 wt.% PPG (80% of the 7.3 wt.% combined of the oleic acid and PAO oil), where the weight percent is based on the total weight of inorganic ceramic precursors. The effects of further increasing molecular weight of the PPG on the pressures and wall drag were also investigated by preparing a batch mixture with PPG having a molecular weight of 1000 Daltons (PPG 1000). Example 4 included PPG 1000, and Example 5 included PPG 725. The batches for Examples 4 and 5 each had 32 wt.% water based on the total weight of inorganic ceramic precursors. The batch mixtures were prepared according to the preparation method described in Comparative Example 1. The batch mixtures for Examples 4 and 5 were then subjected to wall drag testing according to the test methods discussed herein.

[00139] Referring now to FIG. 3, the rate sweep testing data for the batch mixtures of Examples 4 and 5 compared to the control batch of Comparative Example 1 are graphically depicted. The rate sweep testing was conducted at 30 °C over a range of extrusion velocities of from 0.0 to 4 inches per second. The rate sweep testing data for Example 4 are indicated in FIG. 3 by reference numbers 310 PLeft), 312 (Plight). and 314 (wall drag), and the rate sweep testing data for Example 5 are indicated in FIG. 3 by reference numbers 320 (PLeft), 322 (Plight), and 324 (wall drag). The pressure velocity curves from the rate sweep testing data in FIG. 3 show that the PPG-based batch mixtures of Examples 4 and 5 have flatter pressure and wall drag profiles compared to the control batch of Comparative Example 1 (ref. nos. 202, 204, 206). This is indicative of greater shear thinning behavior of the PPG in Examples 4 and 5 compared to the oils in the control batch of Comparative Example 1. Further, the data in FIG. 3 shows that even a reduced amount of the PPG produces reduced wall drag compared to the oleic acid and PAO oil in the control batch of Comparative Example 1. Thus, the amount of extrusion additives can be reduced when PPG is used compared to using a fatty acid and PAO oils, as in Comparative Example 1. The greater molecular weight of the PPG 1000 in Example 4 resulted in even less pressure and wall drag compared to the PPG 725 in Example 5.

[00140] Examples 6-8: Effects o f Changing Water Content

[00141] In Examples 6-8, the effects of changing the water lever in the batch mixture comprising the PPG is investigated. Generally, changing the water level in the batch mixture alters the wall drag during extrusion and batch stiffness of the extruded green structures. In particular, increasing the water content to a particular batch mixture is expected to give lower wall drag and lower batch stiffness. For all of Examples 6-8, PPG 1000 was used to replace the oleic acid and PAO oil in the control batch. For each of Examples 6-8, the batch mixtures included 5.84 wt.% PPG 1000 based on the total weight of the inorganic ceramic precursors, which is a replacement ratio of 0.8: 1 of the oleic acid and PAO oil in the control batch. The batch mixture of Example 6 had 30 wt.% water based on the total weight of the inorganic ceramic precursors. The batch mixture of Example 7 had 32 wt.% water based on the total weight of the inorganic ceramic precursors. The batch mixture of Example 8 had 34 wt.% water based on the total weight of the inorganic ceramic precursors. The batch mixtures of Examples 6-8 were prepared according to the preparation method described in Comparative Example 1. The batch mixtures for Examples 6-8 were then subjected to wall drag and tensile strength testing according to the test methods discussed herein.

[00142] Referring now to FIG. 4, the rate sweep testing data for the batch mixtures of Examples 6-8 compared to the control batch of Comparative Example 1 are graphically depicted. The rate sweep testing was conducted at 30 °C over a range of extrusion velocities of from 0.0 to 4 inches per second. In FIG. 4, the rate sweep testing data for Example 6 are indicated by reference numbers 410 (PLeft), 412 (Plight). and 414 (wall drag), the rate sweep testing data for Example 7 are indicated by reference numbers 420 (PLeft), 422 (Plight). and 424 (wall drag), and the rate sweep testing data for Example 8 are indicated by reference numbers 430 (PLeft), 432 (Plight), and 434 (wall drag). The control batch of Comparative Example 1 is represented by reference numbers 202, 204, and 206.

[00143] FIG. 4 shows the effect varying the water content in the batch mixture from 30 wt.% to 34 wt. % based on the total weight of inorganic ceramic precursors. It is noted that the standard control batch of Comparative Example 1 has 32 wt.% water. As shown by Example 6, using PPG 1000 and reducing the water content to 30 wt.% still produces reduced wall drag compared to the standard control batch of Comparative Example 1, which has 32 wt.% water. Thus, FIG. 4 shows that the use of PPG can enable the amount of water to be reduced while still reducing the wall drag of the batch mixture during extrusion. As the amount of water is increased from 30 wt.% in Example 6 to 32 wt.% in Example 7, the wall drag further decreases. However, further adding water to increase the water content to 34 wt.%, as in Example 8, does not result in a further reduction in wall drag.

[00144] Referring now to FIG. 6, the tensile strength of extrudates prepared from the batch mixture of Example 6 (ref. no. 616), Example 7 (ref. no. 614), and Example 8 (ref. no. 618) are graphically depicted. In FIG. 6, the tensile strength of the control batch of Comparative Example 1 is identified by reference number 622. As shown by FIG. 6, the batch mixtures of Examples 6-8 exhibited tensile strength at least comparable to the tensile strength of the control batch of Comparative Example 1. Example 7 having 32 wt.% water showed greater stiffness compared to the batch mixtures of Examples 6 and 8.

[00145] Example 9: Blends of Polypropylene Glycols with Different Molecular Weights [00146] In Example 9, a batch mixture comprising a mixture of PPG compounds of different molecular weights was prepared and evaluated. The batch mixture of Example 9 included equal amounts of PPG having molecular weights of 425 Daltons, 725 Daltons, and 1000 Daltons. In particular, the batch mixture of Example 9 include 32 wt.% water, 1.94 wt.% PPG 425, 1.94 wt.% PPG 725, and 1.94 wt.% PPG 1000, where the weight percentages are based on the total weight of the inorganic ceramic precursors. The batch mixture of Example 9 was prepared according to the preparation method described in Comparative Example 1. The batch mixture of Example 9 was then subjected to wall drag and tensile strength testing according to the test methods discussed herein.

[00147] Referring to FIG. 5, the wall drag data for Example 9 is shown in comparison to the wall drag for Examples 4 (PPG 1000), Example 5 (PPG 725), and Comparative Example 1 (oleic acid and PAO oil). FIG. 5 shows the wall drag for several different compositions composed of different ratios of various PPGs, exhibiting a wide range of wall drag values from very low for Example 4 (PPG 1000) up to greater values of Example 9 (mixture), which is similar in wall drag to that of the control batch of Comparative Example 1 (oleic acid and PAO oil). By using different ratios of the different PPG molecular weights, different wall drag values can be obtained for the same batch volume.

[00148] Because the different molecular weights can be mixed in any combination and ratio, this allows the wall drag to be tuned to match system requirements. This has potential benefit as die hardware ages. The changing surface characteristics can potentially be compensated for by small adjustments in the batch mixture to maintain constant extrusion performance through the lifetime of the die.

[00149] Example 10: Tensile Strength

[00150] In Example 10, the tensile strength of batch mixtures comprising different PPG molecular weights, different PPG contents, and different water contents are evaluated. The following Table 2 provides the batch mixtures tested and the reference numbers for FIG. 6. The batch mixtures of Example 10 were prepared according to the preparation method described in Comparative Example 1. The batch mixtures of Example 10 were then subjected to tensile strength testing according to the test methods discussed herein.

Table 2

[00151] Excellent wall drag and pressure performance is not in itself adequate. The batch must also maintain adequate tensile properties, in order to minimize forming and drying defects. FIG. 6 shows that the tensile strength values for the batch mixtures comprising PPG are comparable to the control batch of Comparative Example 1 (ref. no. 622), which includes oleic acid and PAO oils. FIG. 6 shows that replacement of oleic acid and PAO oils with PPGs in the batch mixtures does not cause a significant reduction in the tensile strength of the batch mixtures. In fact, FIG. 6 shows that replacement of oleic acid and PAO oil with PPG, in some cases, can increase the stiffness of the batch mixture.

[00152] Comparative Example 11: Polyethylene Glycol

[00153] In Comparative Example 11, polyethylene glycol (PEG) was tested in place of PPG. In particular, a batch mixture comprising PEG in place of the oleic acid and PAO oil in Table 1 was prepared and evaluated. The batch mixture for Example 11 was prepared with 5.8 wt.% PEG and 32 wt.% water. The PEG had a molecular weight of 1000 Daltons. The batch mixture of Example 11 was prepared according to the preparation method described in Comparative Example 1. The batch mixture of Example 11 was then tested for wall drag and tensile strength according to the test methods previously disclosed herein.

[00154] Referring now to FIG. 7, the rate sweep testing data for the batch mixture of Example 11 compared to the control batch of Comparative Example 1 and to the batch mixture of Example 4 (5.8 wt.% PPG 1000) are graphically depicted. The rate sweep testing was conducted at 30 °C over a range of extrusion velocities of from 0.0 to 4 inches per second. The rate sweep testing data for Example 11 are indicated in FIG. 7 by reference numbers 702 (Pteft), 704 (PRight), and 706 (wall drag), and the rate sweep testing data for Example 4 are indicated in FIG. 7 by reference numbers 310 (Pteft), 312 (PRight). and 314 (wall drag). The control batch of Comparative Example 1 is indicated by reference numbers 200 (Pteft), 202 (P ight). and 204 (wall drag). The batch mixture of Example 11 with the PEG 1000 exhibited greater tensile strength compared to the batch mixture of Example 4 (PPG 1000) and the control batch of Comparative Example 1. However, as shown in FIG. 7, the batch mixture of Example 11 comprising the PEG 1000 produced remarkablly higher wall drag, rather than the low wall drag of PPG-based compositions. In contrast to the excellent performance of PPG, the high wall drag imparted by the use of PEG makes PEG unsuitable as an oil replacement in these extrusion compositions.

[00155] Example 12: Scale Up to Twin-Screw Extruder

[00156] In Example 12, a batch mixture comprising PPG was scaled up to operation on a twin-screw extruder. The batch mixtures were further tested by scaling up to 40 lb (inorganics basis) batch size. The batch mixture for Example 12 included PPG1000 (molecular weight of 1000 Daltons) as the lubricant material. The formulation of the batch mixture for Example 12 is provided below in Table 3. Table 3

[00157] The batch mixture of Example 12 having a batch size based on 40 pounds of inorganic ceramic precursors was prepared according to the preparation method described in Comparative Example 1. The batch mixture was then added to an AMPL 32 mm twin screw extruder. The batch mixture was extruded to produce green bodies having a diameter of 4 inches, a cell density of 600 cpsi, and a web thickness of 2 mil, and the system parameters of the twin screw extruder were monitored. For comparison, the control batch of Comparative Example 1 was also prepared in a 40 pound batch and extruded to produce the same 4 inch diameter green bodies having cell density of 600 cpsi and web thickness of 2 mil. [00158] Referring to FIG. 8, the relative die pressure (y-axis) as a function of run time (x- asix) for the batch mixture of Example 12 (ref. no. 802) and the control batch of Comparative Example 1 (ref. no. 800) is graphically depicted. As shown in FIG. 8, extrusion of the batch mixture of Example 12 required less die pressure compared to the control batch of Comparative Example 1. Referring to FIG. 9, the relative torque (y-axis) as a function of run time (x-axis) for the batch mixture of Example 12 (ref. no. 902) and the control batch of Comparative Example 1 (ref. no. 900) is graphically depicted. As shown in FIG. 9, the torque is also reduced for the batch mixture of Example 12 having the PPG compared to the control batch of Comparative Example 1, which included the oleic acid and PAO oil.

[00159] Good temperature control of the extrusion hardware may be beneficial in embodiments, particularly right before the die, because of the influence of temperature on the solubility of PPG into water. Achieving the right degree of control of the solubility of the PPG in the aqueous phase may allow for minimization of adhesion to the extruder hardware and allow for good extrusion performance regulation.

[00160] 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 binder system for use in producing ceramic extrudates, the binder system comprising: a binder comprising methylcellulose, methylcellulose derivatives, or combinations of these; a liquid vehicle; and a lubricant material that is partially miscible in the liquid vehicle at a temperature that is within an operating temperature range of extrusion equipment for producing the ceramic extrudates, where partially miscible in the liquid vehicle means that a first portion of the lubricant material is soluble in the liquid vehicle and a second portion of the lubricant material is insoluble in the liquid vehicle and forms a second phase separate from a first phase comprising the liquid vehicle.

2. The binder system of claim 1, wherein the lubricant material has a solubility in the liquid vehicle that is inversely proportional to temperature, such that when the temperature increases, the solubility of the lubricant material in the liquid vehicle decreases.

3. The binder system of claim 1, wherein the lubricant material is non-reactive with the liquid vehicle and the binder.

4. The binder system of claim 1, wherein the lubricant material is partially miscible in the liquid vehicle at a solubility temperature that is in a range of from 5 °C to 60 °C.

5. The binder system of claim 1, wherein the lubricant material is poly(propylene) glycol (PPG).

6. The binder system of claim 5, wherein the PPG has a number average molecular weight (Mn) of less than or equal to 2000 Daltons.

7. The binder system of claim 5, wherein the PPG has a number average molecular weight of from 400 Daltons to 2000 Daltons.

8. The binder system of claim 5, wherein the PPG has a multi-modal molecular weight distribution.

46

9. The binder system of claim 5, wherein the lubricant material comprises a mixture of at least two different PPGs, where each PPG has a different number average molecular weight.

10. The binder system of claim 1, wherein the liquid vehicle is water.

11. A composition for producing ceramic articles, the composition comprising: at least one inorganic ceramic precursor; and the binder system of claim 1.

12. The composition of claim 11, wherein the composition comprises greater than or equal to 1 wt.% of the lubricant material based on the total weight of the at least one inorganic ceramic precursor.

13. The composition of claim 11, wherein the lubricant material comprises PPG and the composition comprises from 1 wt.% to 15 wt.% PPG based on the total weight of the at least one inorganic ceramic precursor.

14. The composition of claim 11, wherein the at least one inorganic ceramic precursor comprises at least one cordierite forming raw material.

15. The composition of claim 11, further comprising one or more processing additives selected from plasticizers, surfactants, dispersants, or combinations of these.

16. The composition of claim 11, comprising: from 20 wt.% to 50 wt.% water, based on the total weight of the at least one inorganic ceramic precursor; from 1 wt.% to 15 wt.% binder, based on the total weight of the at least one inorganic ceramic precursor; and from 1 wt.% to 15 wt.% PPG, based on the total weight of the at least one inorganic ceramic precursor.

17. A method for forming a ceramic article, the method comprising:

47 forming a batch mixture comprising at least one inorganic ceramic precursor and a binder system, wherein the binder system comprises: a binder comprising methylcellulose, methylcellulose derivative, or combinations of these; a liquid vehicle; and a lubricant material that is partially miscible in the liquid vehicle at a temperature that is within an operating temperature range of extrusion equipment for producing a ceramic extrudate, where partially miscible in the liquid vehicle means that a first portion of the lubricant material is soluble in the liquid vehicle and a second portion of the lubricant material is insoluble in the liquid vehicle and forms a second phase separate from a first phase comprising the liquid vehicle; extruding the batch mixture to produce the ceramic extrudate, wherein the lubricant material in the batch mixture reduces extrusion pressure and torque in the extrusion equipment during extrusion; and firing the ceramic extrudate under conditions sufficient to produce the ceramic article.

18. The method of claim 17, wherein the partial miscibility of the lubricant material in the liquid vehicle reduces accumulation of the second phase in the extrusion equipment.

19. The method of claim 17, wherein the lubricant material has a solubility in the liquid vehicle that is inversely proportional to the temperature.

20. The method of claim 17, wherein the lubricant material is poly(propylene) glycol (PPG) having a number average molecular weight of from 400 Daltons to 2000 Daltons.

21. The method of claim 17, further comprising: extruding the batch mixture with the extrusion equipment to produce the ceramic extrudate; measuring one or more operating conditions of the extruding equipment; and

48 adjusting an amount, a number average molecular weight, a molecular weight distribution, or combinations thereof of the lubricant material based on the measured values of the one or more operating conditions.

22. The method of claim 21, wherein the operating conditions comprises one or more of an extrusion rate, an extrusion pressure, an extrusion temperature, back-up length, work imparted to the batch, or combinations of these.