MXPA00012059A - Binder system for honeycomb ceramic bodies and a method for producing honeycomb bodies - Google Patents

Abstract

A binder system for use in the formation of ceramic or other powder-formed greenware comprising a binder, a solvent for the binder, a surfactant, and a component that is non-solvent with respect to the binder and solvent. The non-solvent component exhibits a lower viscosity than the solvent when containing the binder and comprises a low molecular weight oil having a 90%recovered distillation temperature range of between about 220 to 400°C. Also disclosed is a process of forming and shaping plasticized powder mixtures and a process for forming ceramic articles utilizing the binder system.

Description

AGLUTINANT SYSTEM FOR CERAMIC BODIES IN HONEYCOMB, AND METHOD TO PRODUCE BODIES IN PANAL BACKGROUND OF THE INVENTION FIELD OF THE INVENTION The present invention relates generally to a binder system for use in the field of forming ceramic or ceramic bodies, and to a method for producing ceramic bodies or honeycomb ceramic bodies using said binder system. More particularly, the invention relates to a binder system containing a non-solvent based on low molecular weight oil, and to the use of a binder system in a method for producing honeycomb ceramic bodies.

DESCRIPTION OF THE RELATED TECHNIQUE Binders and binder systems useful for the manufacture of products from pulverized materials, for example, from particulate ceramic materials, must satisfy a number of requirements. For example, the binder and the binder systems must be compatible with the ceramic material, so that a flowing dispersion comprising a relatively high load of the ceramic material in the binder can be provided. In addition, the "raw" preform produced by shaping the dispersion of the ceramic powder in the binder must have reasonable strength so that it can be handled. For a "combustion" or desirable removal of the binder, the binder must be removable from the configured ceramic part without incurring any deformation or breakage of the part. In addition, the binder-free preform must have at least a minimum level of strength, and yet be sufficiently free of binder residues so that defect-free consolidation can be easily achieved. The formulation of binders that meet these requirements is complex, which is why a large number of different binder formulations have been described in the prior art. Recently, cellulose ether binders have been favored for use in the formation of articles of various forms, i.e., honeycomb substrates. The mixtures are intimately mixed and homogeneous, and result in the crude body having good integrity in size and shape, as well as uniform physical properties. In addition to the binders, these powder mixtures typically include certain org additives, including, for example, surfactants, lubricants and dispersants, and function as processing aids to increase wetting, thereby producing a uniform batch.

Recently, there has been an increase in the demand for thinner wall structures and higher cell density, complex configured products, and products that have a large frontal area. The complex and thin-wall configured products that are produced using the current binder technology, ie, cellulose ether binders, are extremely difficult to handle without causing shape deformation, due to the low strength of the "raw" preform. . A recent solution / trend in extrusion technology, especially for multicellular honeycomb bodies, formed of highly saturated ceramic powder mixtures, is to extrude a more rigid body without causing proportional increase in pressures. However, attempts to extrude more rigid batches of ceramic with the current batch components, i.e. the use of the aforementioned cellulose ether binder coupled to the decrease in the amount of water and / or including additives such as seboato sodium or sodium stearate, have been largely unfortunate due to the higher extrusion pressures resulting from the collision of the finer particles and the abrasiveness of the materials involved. Another solution tried is to use fast-setting techniques, that is, solidifying the walls of honeycomb cells quickly after forming, thus ensuring that the dimension of the raw item will not be altered in subsequent cutting and handling steps. Prior methods of rapid hardening involve delayed hardening using fast setting waxes as described, for example, in the U.S. patent. 5,568,652, and / or by applying an external field such as an RF field at the die output. Although these rapid hardening methods involve the extrusion of soft batches, which historically for highly saturated ceramic mixtures has led to better extrusion quality, these methods have not been very successful for thin-walled cell structures. A recent solution described in the patent application of E.U.A. coassigned series No. 60 / 069,637 (Chalasani et al.), involves a powder mixture to form honeycomb structures, which includes inorganic powder, binder, binder solvent, surfactant and a component which is non-solvent with respect to the binder, solvent and powder materials. This powder mix is blended, plasticized and shaped to form a crude ceramic preform body having improved wet and wet strength, and is thus especially suitable for use in the processing of thin-walled honeycomb structures. In addition, Chalasani discloses a preferred mixture of aqueous binder system including water, cellulose ether and a hydrophobic non-solvent. While the Chalasani reference provides significant advances in the ability of the technique to form thin-walled and complex honeycomb ceramic bodies by extrusion, the inclusion of this non-solvent in the powder, for example, light mineral oil, gives as result in additional complications in the "combustion" or removal of the binder. Specifically, it is difficult to remove the binder components from the shaped ceramic part without incurring deformation or breakage of the part. Due to the reduced strength of thin walled honeycomb bodies and the corresponding increase in dimension changes during binder removal due to the exothermic nature of the oil removal, special considerations must be taken into account when baking of the ceramic honeycomb to prevent cracking of the ceramic body. Especially designed powders, apparatus for the removal of volatile compounds, atmospheres containing reduced oxygen and complicated and increased baking cycles, are among the numerous means that have been used to reduce the differential shrinkage and the high frequency of cracking experienced during baking. thin-walled honeycomb ceramic bodies incorporating the aforementioned binder. In light of the above shortcomings experienced in the art, there is a need to develop a binder system which allows a thin-walled ceramic body to be formed and baked into a desired ceramic article without high differential shrinkage and cracking incidences or defects, and which can be quickly and easily removed from the ceramic body.BRIEF DESCRIPTION OF THE INVENTION Therefore, an object of the present invention is to provide a binder system capable of being used in the formation of ceramic bodies or other inorganic honeycomb bodies which results in a sufficiently high wet strength of the crude body formed with at least a portion of the binder system capable of being removed without generating a significant exothermic reaction as a result of said removal during the baking process, thereby reducing the incidences of cracking and the level of differential shrinkage during baking. The above objective of the invention can be achieved in accordance with the invention, which provides a binder system for use in the formation of crude articles of ceramic or other crude article formed of powder, which comprises the essential components of a component of binder, a solvent for the binder component, a surfactant component, and a component that is non-solvent with respect to the binder and solvent components. The non-solvent component exhibits a lower viscosity than the solvent when it contains the binder, and comprises a low molecular weight oil having a distillation temperature scale recovered at 90% between about 220 to 400 ° C, i.e. an oil of low molecular weight.

In accordance with another embodiment of this invention, a batch of moldable powder formed of an inorganic powder component, consisting of a concretable inorganic particulate material, and the aforementioned binder system is provided. According to another embodiment of the invention, there is provided a method for forming and configuring plasticized powder mixtures, comprising mixing an inorganic powder component consisting of a mixture of concretable inorganic particulate material and the binder system of the invention, and then plasticizing the components to form a plasticized mixture, and then configuring the plasticized mixture to form a crude body. According to a final embodiment of the invention, a method for manufacturing ceramic articles is provided, which comprises the aforementioned steps of forming and configuring the binder system and inorganic powder composition, and then including the further step of heating this ceramic raw body, which has the desired shape, to remove the binder system and bake the formed ceramic body, thus resulting in a baked ceramic body. An advantageous feature of the binder system is that it is useful for producing cordierite honeycomb structures having thin walls and a large number of cells. Specifically, the resultant wet raw body formed in this manner exhibits a high degree of stiffness necessary to prevent collapse in honeycomb ceramic structures with very thin walls, i.e. those having a thickness of less than 150 μm. An additional benefit of this invention is that the bake cracks associated with the above binder systems are reduced, while still maintaining the extrusion benefits of the above binder systems. Specifically, the low molecular weight oils used in the present invention exhibit a lower exothermic intensity associated with their removal when compared to the oil-based non-solvent components used above.

BRIEF DESCRIPTION OF THE FIGURES For a better understanding of the invention, reference is made to the accompanying drawings, in which: Figure 1 is a graphic illustration showing the reduced percentage of lateral and frontal cracks for ceramic bodies incorporating the binder system of the invention incorporates a low molecular weight oil, comparatively with ceramic bodies containing binder systems that incorporate a non-solvent based on oil; Figure 2 is a graphical illustration comparing the exothermic intensity of the removal of the binder system of the invention with the exothermic intensity associated with the removal of a binder system containing an oil-based standard non-solvent component.

DETAILED DESCRIPTION OF THE INVENTION According to the invention, a binder system for use in the raw material processing steps of a ceramic body or other subsequently baked inorganic body includes the following components: a binder, a solvent for the binder, a surfactant, and a component which is non-solvent with respect to at least the binder and solvent components. The non-solvent is a low molecular weight oil, which exhibits a lower viscosity than the binder when it contains the solvent and a distillation temperature scale recovered at 90% between about 220 to 400 ° C, preferably about 220 to 320 ° C. ° C, and more preferably from about 220 to 280 ° C, referred to herein as low molecular weight oil. The low molecular weight oil still functions like the one described in the Chalasani application mentioned above. In summary, the low molecular weight oil replaces a portion of the solvent, and does not contribute to plasticity, but provides the necessary fluidity to perform the configuration, while still allowing the batch to remain firm. As such, the present binder system achieves the same desired increase in the raw and wet strength over that achieved with conventional binders, without proportional increases in the processing difficulty. In other words, the binder system of the present invention allows the extrusion of a firm batch without adversely affecting the processing performance such as extrusion pressure, torque and flow characteristics. Typical oil-based non-solvents, as described above in the Chalasani application mentioned above, provide an important benefit of shape retention for thin-walled ceramic bodies in the raw and wet state. However, these highly saturated ceramic systems based on immiscible liquids / aqueous liquids are relatively difficult to bake without resulting cracking. The cracking of the parts is due, in part, to the difficulty of removing large quantities of the standard oil-based fluids typically used as the non-solvent, along with other organic additives present in the system, at relatively high temperatures (150- 500 ° C). The removal of these organic additives comprises a sequence of simultaneous reactions that are mainly complex and include, for example, oxidation, volatilization and thermal degradation of the organic additives. Due to the binder combustion phenomena associated with the use of these standard oil-based non-solvent components containing binder systems, the honeycomb parts exhibit large thermal gradients and drastic dimensional changes. The use of a binder system incorporating a low molecular weight oil as the non-solvent component is superior to any of the standard binder systems containing non-solvent described above, including those described in the reference mentioned above. This binder system of the invention provides the benefit that the low molecular weight oil in the binder system is removed by means of volatilization, a baking reaction much less exothermic than that required to remove the standard binder systems. containing a non-solvent component based on oil. As a result of the removal means required for this binder system of the invention, the raw bodies incorporating the binder system of the invention will exhibit a reduced exotherm during baking, which will likely lead to reduced cracking of the bodies of the binder. honeycomb ceramic subsequently formed. The requirement that the low molecular weight oil exhibit a distillation temperature scale recovered to 90% between approximately 220-400 ° C as measured by and as defined in ASTM D86, ensures that the oil exhibits an exothermic combustion associated with its removal that is much less intense than for standard oil-based fluids that are typically used as the non-solvent, for example, light mineral oil. Generally, low molecular weight oils are oils that consist predominantly of straight or branched chain saturated or unsaturated hydrocarbons that exhibit carbon chain lengths that have distributions on the scale of 14 to 24; preferably, at least 70% of the carbon chain length distributions, and more preferably 90% of the carbon chain length distributions are within the range between 14 to 24. A desirable feature than low weight oil Molecular should exhibit is the ability to maintain its liquid nature during the forming / extrusion process. In addition, the low molecular weight oil must exhibit a solubility parameter in accordance with the following Hansen parameters, as defined by Alian FM Burton in the "Handbook of Solubility Parameters and Other Cohesion Parameters", CRC Press, pp. 95-111 , 2a. ed., 1991: (1) a dispersion parameter, dD, ranging from about 12 to 20, preferably between about 14 to 19; (2) a polarity parameter, dP, less than equal to or equal to 2, preferably less than or equal to 1; (3) a hydrogen bridge formation parameter, 5H, less than or equal to 4, preferably less than or equal to 2; and (4) a total parameter, dr, ranging from about 12 to 20, preferably from about 14 to 19. Acceptable non-solvent low molecular weight oils include polyalpha olefins, light mineral oils that exhibit the recovered distillation temperature at 90 % needed, and linear alpha olefins. The preferred binders used in this invention are aqueous based, that is, they are capable of forming hydrogen bonds with polar solvents. Acceptable binders for use in the present invention are methylcellulose, ethylhydroxyethylcellulose, hydroxybutylmethylcellulose, hydroxymethylcellulose, hydroxypropylmethylcellulose, hydroxyethylmethylcellulose, hydroxybutylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, sodium carboxymethylcellulose, and mixtures thereof. Methylcellulose and / or methylcellulose derivatives are especially suitable as organic binders in the practice of the present invention, with methylcellulose, hydroxypropylmethylcellulose, or combinations thereof being preferred. Preferred sources of cellulose ethers are Methocel A4M, F4M, F240 and K75M cellulose products from Dow Chemical Co. Methocel A4M cellulose is a methyl cellulose. The cellulose products Methocel F4M, F240 and K75M are hydroxypropylmethylcellulose. The properties of the preferred cellulose ether binders such as methylcellulose, are water retention, water solubility, surfactant character and wetting capacity, thickening of the mixture, providing wet and dry raw strength to the raw bodies, gelation thermal and hydrophobic association in an aqueous environment. Cellulose ether binders that promote the hydrophobic association with the non-solvent and the interaction of hydrogen bonding with the solvent are desirable. Examples of substituent groups that provide hydrophobic association with the non-solvent are methoxy, propoxy and butoxy groups. These substituents that provide the hydrophobic association also contribute to the strength of the gel binder. Substituent groups that maximize the interaction of hydrogen bonding with polar solvents, for example, water, are hydroxypropyl and hydroxyethyl groups, and to a lesser extent hydroxybutyl groups. This combination of properties allows the binders to be at the interface between the solvent and the non-solvent. Acceptable solvents for use in the binder system of the invention should be water based, and provide hydration of the binder component and the particulate inorganic component. Particularly preferred as the solvent are water or water miscible solvents. Acceptable surfactants for use in the binder system of the invention include, for example, Cs-C22 fatty acids and / or their derivatives, C-C22 fatty esters, C8-C22 fatty alcohols, stearic, lauric, linoleic and palmitoleic, stearic acid in combination with ammonium lauryl sulfate, with lauric, stearic and oleic acids being particularly preferred. One particularly preferred embodiment of the binder system comprises a binder component comprising a cellulose ether selected from the group consisting of methyl cellulose, methyl cellulose derivatives, and combinations thereof, a non-solvent comprising polyalpha olefin, a surfactant selected from the group consisting of group consisting of stearic acid, ammonium lauryl sulfate, lauric acid, oleic acid, palmitic acid, and combinations thereof, and water as a solvent.

The present invention is not restricted to ceramic batch formulations, but has general application in powder forming processes, that is, in the formation of products or preforms for products from essentially any inorganic material concretable into particles, which is available in, or can be converted to, a finely divided form. The powder formed materials from which this invention is suitable include particulate ceramics, including crystalline ceramic materials, particulate glasses and crystallizable glasses (vitreous ceramics). For ceramics, vitreous ceramics and vitreous ceramic powders, those materials are understood as well as their pre-baked precursors. Combinations are physical or chemical combinations, for example mixtures or mixed materials. Examples of powdered materials are cordierite, mulita, clay, talc, zircon, zirconia, spinel, aluminas and their precursors, silicas and their precursors, silicates, aluminates, lithium aluminosilicates, aluminum silica, feldspar, titania, fused silica, nitrides , carbides, borides, for example, silicon carbide, silicon nitride, sodium lime, aluminosilicate, borosilicate, barium sodium borosilicate, or mixtures thereof, as well as several others. Although the binder system offers substantial advantages in conventional inorganic forming processes, it provides unique processing advantages for ceramic materials, especially those producing cordierite, mulita, or mixtures thereof during baking, some examples of such mixtures being approximately 2% to about 60% of mulite, and about 30% to about 97% of cordierite, including other phases, typically up to about 10% by weight. Some compositions of the ceramic batch material for the formation of cordierite that are especially suitable for the practice of the present invention are those described in the U.S.A. 3,885,977, which is incorporated herein by reference. A particularly preferred ceramic material and one which ultimately forms cordierite after baking is the following in parts by weight, assuming 100 parts by weight: approximately 33 to approximately 41, and more preferably approximately 34 to approximately 40 parts of aluminum oxide, approximately 46 to about 53, and more preferably about 48 to about 52 parts of silica, and about 11 to about 17, and more preferably about 12 to about 16 parts of magnesium oxide. In the practice of the present invention, a mouldable powder batch composition comprising the binder system and an inorganic powder component consisting of a concretable inorganic particulate material, for example, a ceramic powder material, can be prepared, using the components in any desired and selected quantity.

In a preferred embodiment, the composition comprises 100 parts by weight of the inorganic powder, about 2 to 50 parts by weight of the low molecular weight oil component, about 0.2 to 10 parts by weight of the surfactant, about 2 to 10 parts by weight. of the binder, and about 6 to 50 parts by weight of the solvent component. In a particularly preferred embodiment, the composition comprises 100 parts by weight of the inorganic powder, about 5 to 10 parts by weight of the low molecular weight oil, about 0.2 to 2 parts by weight of the surfactant, about 2.5 to 5 parts by weight of the binder, and about 8 to 25 parts by weight of the solvent component. The individual components of the binder system are mixed with a mass of the inorganic powder material, for example, the ceramic powder material, in a known manner suitable for preparing an intimate mixture of the ceramic material and the binder system. For example, all the components of the binder system can be pre-mixed with each other, and the mixture is added to the ceramic powder material. In this case, the entire portion of the binder system can be added at a time, or divided portions of the binder system can be added one after the other at suitable intervals. Alternatively, the components of the binder system may be added to the ceramic material one after the other, or each previously prepared mixture of two or more components of the binder system may be added to the ceramic powder material. In addition, the binder system can be mixed first with a portion of the ceramic powder material. In this case, the remaining portion of the ceramic powder is subsequently added to the prepared mixture. In any case, the binder system must be mixed uniformly with the ceramic powder material in a predetermined portion. Uniform mixing of the binder system and the ceramic powder material can be achieved in a known kneading process at an elevated temperature. In particular, in the case of batches for ceramic products, batch formation occurs in two stages before the configuration step. In the first stage or wetting step of the batch formation, the inorganic powder particles, the surfactant and the binder component are mixed dry, followed by the addition of the solvent such as in a Littleford mixer. The solvent is added in an amount that is less than what is needed to plasticize the batch. With water as the solvent, water hydrates the binder and dust particles. The low molecular weight oil is then added to the mixture to soak the binder and the powder particles. Low molecular weight oil has lower surface tension than water. As a result, it soaks the particles much more quickly than the solvent. In this step, the powder particles are coated and dispersed by the surfactant, the solvent and the low molecular weight oil.

In a preferred embodiment, the plasticization is carried out in a second stage. In this step, the wet mix of the first stage is separated by shear in any suitable mixer in which the batch will be plasticized such as, for example, in a twinworm mixer / extruder, auger mixer, mullet mixer , or double arm, etc. The resulting firm batch is then formed into a green body by any known method for forming plasticized mixtures such as, for example, extrusion, injection molding, sliding molding, centrifugal molding, pressure molding, dry pressing, etc. The invention is better adapted for extrusion through a die. The vertical or horizontal extrusion operation can be carried out using a hydraulic ram extrusion press, or a two-stage single auger extruder with deaeration, or a twinworm mixer with a die assembly fixed to the discharge end. In the latter, the appropriate worms are selected in accordance with the material and other process conditions to intensify the pressure sufficient to force the batch material through the die. The prepared ceramic raw body is then baked at a selected temperature under a suitable atmosphere, and for a time which depends on the composition, size and geometry, to result in a baked body of the desired ceramic. For example, for a composition that is primarily for cordierite formation, temperatures typically range from about 1300 to about 1450 ° C, where retention times at these temperatures vary from about 1 hour to 8 hours. Baking temperatures and times depend on factors such as the types and amounts of materials and the type of equipment used, but typical total baking times vary between approximately 20 to 80 hours. The benefits resulting from the use of the binder system of the invention are similar to those described in the co-assigned co-assigned application mentioned above, which details the use of a non-solvent in the formation and configuration of crude ceramic bodies. Specifically, said advantages include: (1) configuration, for example, the extrusion can be carried out at significantly lower temperatures, almost at least about 25% lower, than that achieved by conventional binder systems; (2) processing at lower temperatures, and thus less mixing torques, which in turn allows extrusion at higher feed rates (at least 2 times, and generally about 2-2.5 times higher) than that allow conventional binder systems, while still maintaining the quality of the product; (3) processing involving cellulose ether binders that use water as a solvent, which produces higher gel strengths at higher yields and reduced heating rates of the batch of the ceramic batch compared to conventional batches, where the capacity of Higher performance was achieved by the use of cellulose ethers with low gel strength, and drying blisters resulting during dielectric drying; (4) benefits of the method of extruding the orthogonality of the cells in the perimeter of the configured body, as well as a uniform outer layer; and (5) a good retention of the shape after leaving the die and, specifically, in the case of multicellular structures, an improvement of the orthogonality of the cells in the perimeter of the part closest to the outer layer. As described above, this method exhibits many of the same advantages, for example, increased wet strength and increased extrusion rates, of the non-solvent binder system mentioned above and described in the co-pending application.; however, as described above, inherent in the use of these standard oil-based non-solvents and other conventional binder systems, is that during baking, the large exotherms associated with the combustion of the non-solvent have resulted in shrinkage and Differential cracking. The present binder system overcomes this deficiency of the above binders, incorporating a low molecular weight oil which exhibits a distillation temperature recovered at 90% between about 220 to 320 ° C, as the non-solvent component. The main benefits of the present binder system shown on the above binder systems, including the prior systems containing non-solvent, include the following: (1) removal of the binder system is effected by a reaction exhibiting a reduced exotherm, which reduces the occurrence of cracking or defects during baking, and thus allows the easy formation of baked bodies; (2) the use of low molecular weight oil decreases the amount of fluid / binder that needs to be removed during baking; (3) the low viscosity of the low molecular weight oil, slightly higher than that of water, and the reduced surface tension in certain compositions, i.e. the use of appropriate surfactants, decreases the mixing torques during extrusion, and exhibits minimum deformation increase / maximum stiffness; (4) the dimensional changes exhibited during baking bodies incorporating the binder system of the invention, resemble those of a crude body without oil-based fluid; (5) The present binder system can be easily removed at a comparatively higher speed and, consequently, allows increased productivity of baked bodies. The present invention thus suitably applies to the manufacture of complicated shaped bodies, especially ceramic, which are usually formed by extrusion, and to the manufacture of the corresponding baked bodies, such as honeycomb ceramic multicell structures having a high density of cells and exhibit thin wall dimensions therein.

EXAMPLES In order to better illustrate the principles of the present invention, several examples of the binder system according to the same will be described. However, it will be understood that the examples are given for illustrative purposes only, and that the invention is not limited to mimes, but various changes and modifications can be made without departing from the spirit thereof.

EXAMPLES 1 TO 11 Various mixtures of the suitable inorganic powder batch in the formation of a cordierite ceramic body are given in Table I in parts by weight. Each of the compositions 1 to 11 were prepared by combining and dry blending the components of the designated inorganic mixture indicated in Table I; Y and Z differ in the ratio of the coarse and fine alumina used in the alumina component. An amount of the binder system included in Table II is then added to each of the inorganic dry mixtures, and then mixed to form a mixture of the plasticized ceramic batch. Two of the eleven compositions have been included for comparative purposes. Each of these eleven different plasticized batch mixtures comprised 100 parts by weight of the batch of inorganic powder batch and different amounts, up to 35.9 parts by weight, of the binder system components as described in Table II. Table III includes the different non-solvent components (ie, various types of oil) used in the examples and represented by the designations A-F. The distribution of the carbon chain and the recovered distillation temperature at 90%, 95% recovered for Durasyn 162, of these non-solvents, are given in Table III. Note that non-solvents A, C and D each comprise a low molecular weight oil that exhibits predominantly carbon chain lengths on a scale between 14 and 24, and a distillation temperature at 90% at least greater than 220 ° C; the distillation temperature recovered at 95% of 230 ° C of the Durasyn 162 corresponds to a distillation temperature recovered to 90% higher than 220 ° C. Each of the different plasticized mixtures was extruded through a twinworm extruder to form honeycomb ceramic substrates exhibiting a diameter of 14.37 cm, a cell wall size of 139.7 μ and a length of 10.16 cm; composition 10 is the exception, since it exhibited a diameter of 10.57 cm, a cell wall size of 101.6 μ and a length of 11.43 cm. The conditions maintained during the extrusion included an extrusion pressure scale of 150-170 kg and an extrusion temperature scale of 23-25 ° C. Approximately 90 honeycomb ceramic raw bodies were formed from each of the 11 compositions of the batch, and each of the 90 ceramic honeycombs for each of the 11 compositions were subjected to a sufficient heating and baking cycle for each of the 11 compositions. remove the organic binder system from, and to concretize, the honeycomb substrates. The total number of frontal and lateral cracks was counted for each of the 11 baked (a total for each of the compositions). The total number of lateral and frontal cracks for each composition was then divided between the total number of substrates baked for that composition to arrive at a percentage value of lateral and frontal cracks for the composition, and this figure is recorded in Table II as %.

TABLE I TABLE II Composition 1 used an Industrene 9018 stearic acid, while the stearic acid of compositions 2 to 13 comprised Emorsol E-120, both straight-chain stearic acid. 2 See table III.

TABLE III Distillation temperature recovered from 1 to 95% An examination of the cracking values reported in Table II reveals that the use of low molecular weight oil, Durasyn 162 or Penreco 2260/6970, as a component of the binder system, produces substrates in baked honeycomb which exhibit a percentage of frontal and lateral cracking of almost zero, even in compositions containing up to 9.2 parts by weight of oil. By comparing the composition 4 of the invention with the comparative compositions 5 and 6, all containing 8 parts of oil in the binder system, it can be seen that the percentage of frontal and lateral cracking of 0% for the composition 4, is compares favorably with the cracking percentages for compositions 5 and 7, which are 93 and 2.0%, respectively. The effect of reducing frontal and lateral cracking is even more substantial in those compositions that use 9.2 parts of oil in the binder system; Composition 2 exhibits a percentage of frontal cracking of 2%, while Composition 1 exhibits a value of 119%. This reduction in the effect of the percentage of cracking exhibited by the compositions of the binder system of the invention containing low molecular weight oil, is illustrated more clearly in Figure 1; the designations of the composition correspond to the designations in Table I. The reduced cracking during the baking of the honeycomb ceramic substrate bodies incorporating the batch system of the invention, when compared to those incorporating conventional binder systems that contain oil is due to the fact, as described above, that the organic additives in the binder system, the low molecular weight oil, exhibits a much less intense exothermic reaction after the removal of the raw body during baking. This evaporation and the reduced exothermic condition are supported by the data shown in Figure 2, where the DTA results of three of the previous compositions are plotted. The data plotted in Figure 2 reveal that the composition incorporating standard oil-containing binder systems, ie, light mineral oil binder systems, composition 1, exhibits a substantial exotherm on the temperature scale of 100-500 °. C. This should be compared with the graphs of compositions 3 and 4, which reveal that the binder system, after the removal, exhibits an endothermic reaction between 100-200 ° C, followed by a slightly exothermic reaction on the temperature scale of 200-300. This figure suggests that the binder system of compositions 3 and 4 is removed by evaporation, followed by a period of volatilization, as opposed to the pyrolysis that appears to be the removal mechanism for composition 1. It should be noted that the graphs of the compositions 3 and 4 resemble those expected for standard raw bodies incorporating standard binder systems that simply contain a binder component, solvent for the binder component and a surfactant, for example, methylcellulose, water and stearic acid.

Claims (28)

NOVELTY OF THE INVENTION CLAIMS

1. - A binder system for use with a ceramic body, characterized in that it comprises: a binder component, a solvent for the binder component, a surfactant component, and a component which is non-solvent with respect to at least the binder and solvent components, and which exhibits lower viscosity than the solvent when containing the binder, the non-solvent component comprising a low molecular weight oil having a distillation temperature recovered at 90% between about 220 to 400 ° C .

2. The binder system according to claim 1, further characterized in that the low molecular weight oil exhibits a distillation temperature recovered at 90% between about 220 to 320 ° C.

3. The binder system according to claim 1, further characterized in that the low molecular weight oil exhibits a distillation temperature recovered at 90% between about 220 to 280 ° C.

4. The binder system according to claim 1, further characterized in that it comprises in parts by weight, assuming 100 parts of inorganic components, approximately 15 to 30 parts of low molecular weight oil, approximately 0.5 to 10 parts of surfactant. , about 2 to 20 parts of binder, and about 50 to 75 parts of solvent.

5. The binder system according to claim 1, further characterized in that it comprises, in parts by weight, about 5 to 10 parts of low molecular weight oil, about 1 to 5 parts of surfactant, about 5 to 15 parts. of binder, and approximately 60 to 70 parts of solvent.

6. The binder system according to claim 1, further characterized in that the low molecular weight oil is selected from the group consisting of polyalpha olefins, light mineral oils that they exhibit the necessary distillation temperature recovered at 90%, and linear alpha olefins.

7. The binder system according to claim 6, further characterized in that the binder comprises a cellulose ether selected from the group consisting of methylcellulose, methylcellulose derivatives, and combinations thereof, the non-solvent component is polyalphaolefin, the surfactant is selected from the group consisting of stearic acid, ammonium lauryl sulfate, lauric acid, oleic acid, palmitic acid, and combinations thereof, and the solvent is water.

8. A batch of moldable powder comprising an inorganic powder component and a binder system, the inorganic powder component consisting of a concretable inorganic particulate material, characterized in that: the binder system comprises a binder component, a solvent for the binder component, a surfactant component, and a component which is non-solvent with respect to at least the binder and solvent components, and which exhibits lower viscosity than the solvent when it contains the binder, the component non-solvent comprising a low molecular weight oil having a distillation temperature recovered at 90% between about 220 to 400 ° C.

9. The binder system according to claim 8, further characterized in that the low molecular weight oil exhibits a distillation temperature recovered at 90% between about 220 to 320 ° C.

10. The binder system according to claim 8, further characterized in that the low molecular weight oil exhibits a distillation temperature recovered at 90% between about 220 to 280 ° C.

11. The batch of moldable powder according to claim 8, further characterized in that it comprises 100 parts by weight of the inorganic powder, about 2 to 50 parts by weight of the non-solvent, about 0.2 to 10 parts by weight of the surfactant, approximately 2 to 10 parts by weight of the binder, and about 6 to 50 parts by weight of the solvent.

12. - The batch of moldable powder according to claim 8, further characterized in that it comprises 100 parts by weight of the inorganic powder, about 5 to 10 parts by weight of the non-solvent, about 0.2 to 2 parts by weight of the surfactant component, approximately 2.5 to 5 parts by weight of the binder component, and approximately 8 to 25 parts by weight of the solvent component.

13. The binder system according to claim 8, further characterized in that the low molecular weight oil is selected from the group consisting of polyalpha olefins, light mineral oils that exhibit the necessary distillation temperature recovered at 90%, and alpha linear olefins.

14. The mouldable powder according to claim 13, further characterized in that the binder comprises a cellulose ether selected from the group consisting of methylcellulose, methylcellulose derivatives, and combinations thereof, the non-solvent component is polyalphaolefin, The surfactant is selected from the group consisting of stearic acid, ammonium lauryl sulfate, lauric acid, oleic acid, palmitic acid, and combinations thereof, and the solvent is water.

15. A method for forming and configuring plasticized powder mixtures, characterized in that it comprises: combining components comprising an inorganic powder component consisting of a mixture of concretable particulate inorganic material, and a binder system comprising a binder component , a solvent for the binder component, a surfactant component, and a component which is non-solvent with respect to at least the binder and solvent components, and which exhibits lower viscosity than the solvent when it contains the binder , the non-solvent component comprising low molecular weight oil having a distillation temperature recovered at 90% between 220 to 400 ° C; mix and plasticize the components to form a plasticized mixture; and configure the plasticized mixture to form a crude body.

16. The binder system according to claim 15, further characterized in that the low molecular weight oil exhibits a distillation temperature recovered at 90% between about 220 to 320 ° C.

17. The binder system according to claim 15, further characterized in that the low molecular weight oil exhibits a distillation temperature recovered at 90% between about 220 to 280 ° C.

18. The method according to claim 15, further characterized in that mixing and plasticizing involve dry mixing the inorganic powder mixture, the surfactant and the binder to form a uniform dry mixture, adding the solvent to the dry mixture. resulting to form an intermediate plasticized mixture, and then add the non-solvent to the intermediate plasticized mixture to form the plasticized mixture.

19. The method according to claim 15, further characterized in that the plasticized mixture comprises 100 parts by weight of the inorganic powder, approximately 2 to 50 parts by weight of the non-solvent, approximately 0.2 to 10 parts by weight of the surfactant, approximately 2 to 10 parts by weight of the binder, and about 6 to 50 parts by weight of the solvent.

20. The method according to claim 15, further characterized in that the plasticized mixture comprises 100 parts by weight of the inorganic powder, about 5 to 10 parts by weight of the non-solvent, about 0.2 to 2 parts by weight of the surfactant component. , about 2.5 to 5 parts by weight of the binder component, and about 8 to 25 parts by weight of the solvent component.

21. The method according to claim 15, further characterized in that the configuration is carried out by passing the mixture through a twinworm extruder., and then through a die to form a raw honeycomb structure.

22. A method for manufacturing ceramic articles, characterized in that it comprises the steps of forming and configuring a composition for the manufacture of ceramics, and baking the resulting shaped and formed raw body, wherein the composition for the manufacture of the ceramic comprises a inorganic powder component consisting of a concretable inorganic particulate material, and a binder system comprising a binder, a solvent for the binder, a surfactant, and a component which is non-solvent with respect to at least the components of binder and solvent, and which exhibits a lower viscosity than the solvent when containing the binder, the non-solvent component comprising a low molecular weight oil having a distillation temperature recovered at 90% between about 220 to 400 ° C.

23. The binder system according to claim 22, further characterized in that the low molecular weight oil exhibits a distillation temperature recovered at 90% between about 220 to 320 ° C.

24. The binder system according to claim 22, further characterized in that the low molecular weight oil exhibits a distillation temperature recovered at 90% between about 220 to 280 ° C.

25. The method according to claim 22, further characterized in that the formation involves mixing and the plasticization involves dry mixing the inorganic powder mixture, the surfactant and the binder to form a uniform dry mixture, adding the solvent to the The resulting dry mixture to form an intermediate plasticized mixture, and then add the non-solvent to the intermediate plasticized mixture to form the plasticized mixture.

26. The method according to claim 22, • 3 further characterized in that the plasticized mixture comprises 100 parts by weight of the inorganic powder, approximately 2 to 50 parts by weight of the non-solvent, approximately 0.2 to 10 parts by weight of the surfactant, approximately 2 to 10 parts by weight of the binder. , and about 6 to 50 parts by weight of the solvent.

27. The method according to claim 22, further characterized in that the plasticized mixture comprises 100 parts by weight of the inorganic powder, about 5 to 10 parts by weight of the non-solvent, about 0.2 to 2 parts by weight of the surfactant, about 2.5 to 5 parts by weight of the binder, and about 8 to 25 parts by weight of the solvent. The method according to claim 22, further characterized in that the configuration is carried out by passing the mixture through a twinworm extruder, and then through a die to form a raw honeycomb structure.