EP1478604A1 - Ceramic compounds having a high proportion of solids for producing ceramic materials and products having a low level of shrinkage - Google Patents

Ceramic compounds having a high proportion of solids for producing ceramic materials and products having a low level of shrinkage

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Publication number
EP1478604A1
EP1478604A1 EP03714683A EP03714683A EP1478604A1 EP 1478604 A1 EP1478604 A1 EP 1478604A1 EP 03714683 A EP03714683 A EP 03714683A EP 03714683 A EP03714683 A EP 03714683A EP 1478604 A1 EP1478604 A1 EP 1478604A1
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EP
European Patent Office
Prior art keywords
ceramic
solids content
fraction
fractions
vol
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Application number
EP03714683A
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German (de)
French (fr)
Inventor
Wolfgang Von Gentzkow
Jünger HUBER
Gerhard Piecha
Lothar SCHÖN
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Siemens AG
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Siemens AG
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Publication of EP1478604A1 publication Critical patent/EP1478604A1/en
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    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
    • C04B35/622—Forming processes; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
    • C04B35/626—Preparing or treating the powders individually or as batches ; preparing or treating macroscopic reinforcing agents for ceramic products, e.g. fibres; mechanical aspects section B
    • C04B35/62605—Treating the starting powders individually or as mixtures
    • C04B35/62625—Wet mixtures
    • C04B35/6263—Wet mixtures characterised by their solids loadings, i.e. the percentage of solids
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
    • C04B35/622—Forming processes; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
    • C04B35/626—Preparing or treating the powders individually or as batches ; preparing or treating macroscopic reinforcing agents for ceramic products, e.g. fibres; mechanical aspects section B
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B2235/00—Aspects relating to ceramic starting mixtures or sintered ceramic products
    • C04B2235/02—Composition of constituents of the starting material or of secondary phases of the final product
    • C04B2235/50—Constituents or additives of the starting mixture chosen for their shape or used because of their shape or their physical appearance
    • C04B2235/54—Particle size related information
    • C04B2235/5418—Particle size related information expressed by the size of the particles or aggregates thereof
    • C04B2235/5436—Particle size related information expressed by the size of the particles or aggregates thereof micrometer sized, i.e. from 1 to 100 micron
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B2235/00—Aspects relating to ceramic starting mixtures or sintered ceramic products
    • C04B2235/02—Composition of constituents of the starting material or of secondary phases of the final product
    • C04B2235/50—Constituents or additives of the starting mixture chosen for their shape or used because of their shape or their physical appearance
    • C04B2235/54—Particle size related information
    • C04B2235/5418—Particle size related information expressed by the size of the particles or aggregates thereof
    • C04B2235/5445—Particle size related information expressed by the size of the particles or aggregates thereof submicron sized, i.e. from 0,1 to 1 micron
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B2235/00—Aspects relating to ceramic starting mixtures or sintered ceramic products
    • C04B2235/02—Composition of constituents of the starting material or of secondary phases of the final product
    • C04B2235/50—Constituents or additives of the starting mixture chosen for their shape or used because of their shape or their physical appearance
    • C04B2235/54—Particle size related information
    • C04B2235/5463—Particle size distributions
    • C04B2235/5472—Bimodal, multi-modal or multi-fraction
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B2235/00—Aspects relating to ceramic starting mixtures or sintered ceramic products
    • C04B2235/60—Aspects relating to the preparation, properties or mechanical treatment of green bodies or pre-forms
    • C04B2235/602—Making the green bodies or pre-forms by moulding
    • C04B2235/6021—Extrusion moulding
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B2235/00—Aspects relating to ceramic starting mixtures or sintered ceramic products
    • C04B2235/60—Aspects relating to the preparation, properties or mechanical treatment of green bodies or pre-forms
    • C04B2235/602—Making the green bodies or pre-forms by moulding
    • C04B2235/6022—Injection moulding
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B2235/00—Aspects relating to ceramic starting mixtures or sintered ceramic products
    • C04B2235/60—Aspects relating to the preparation, properties or mechanical treatment of green bodies or pre-forms
    • C04B2235/602—Making the green bodies or pre-forms by moulding
    • C04B2235/6027—Slip casting

Definitions

  • the invention relates to ceramic compositions for molding ceramic materials and / or products by plastic shaping (extrusion, injection molding) or casting (film casting, slip casting).
  • Ceramic masses consist of ceramic powders, an aqueous dispersion medium and one or more binders, the so-called binder.
  • This binder contains water-soluble or water-swellable polymer materials.
  • mineral raw materials are ground into powder, granulated and prepared into ceramic masses by adding water, plasticizers, solidifying agents and / or sintering aids.
  • the shaping takes place with these materials. This can be done by pressing, plastic forming (extrusion, injection molding) or casting (film casting, slip casting). After shaping, it is dried. The material shrinks due to the volatile constituents escaping during drying, essentially water. After shaping by casting or injection molding, the shrinkage is up to 70% by volume, since the masses contain up to 70% water to ensure the required flowability.
  • the green bodies obtained after drying are optionally processed mechanically. After this processing, sintering (firing) takes place. This is done by pyrolysis of the polymer components. In the event of fire, the material shrinks by a further 20 to 30%.
  • the volume shrinkage of the ceramic during drying and sintering depends on the proportion of the aqueous and polymeric dispersion medium that is required for the processability of the ceramic masses. Here it applies that this proportion is all the greater is, the more complex shapes are to be realized and the better the masses have to flow during molding by injection molding or extrusion. While a moisture content of 5 - 10% is sufficient for pressing, approx. 25 to 30% water content is required for extrusion and approx. 60 - 70% for casting. Due to the volume shrinkage occurring during drying and sintering, it is hardly possible to realize the specifications of the three-dimensional dimensions of the ceramic products without post-processing. Therefore, mechanical reworking is required in most cases. In view of the hardness of ceramic materials, however, post-processing involves considerable effort and cost.
  • the object of the present invention is to increase the solids content in ceramic compositions while maintaining good processability in order to minimize the shrinkage during drying, debinding and / or sintering of the ceramic.
  • the invention relates to ceramic compositions which can be processed by extrusion, casting and / or injection molding and which have a solids content of at least 60% by volume, the solids content being a combination of at least two fractions, so-called powder fractions, with different particle size distributions.
  • the invention also relates to the use of these ceramic materials for producing high-quality ceramic materials with little shrinkage.
  • the ceramic compositions according to the invention advantageously comprise a combination of at least two solid fractions which differ in their average particle size by a factor of 4-5.
  • D is preferably 5 o- particle size of the smaller (finer or more finely divided) particle fraction of ⁇ 1 micron and the larger (coarser, coarser) particle fraction 1 - lO ⁇ m.
  • the ceramic compositions according to the invention comprise a combination of three solid fractions which differ in terms of their particle size.
  • the D 50 particle size of the smallest particle fraction is preferably ⁇ 1 ⁇ m, that of the middle particle fraction 1-10 ⁇ m and that of the largest particle fraction> 10 ⁇ m.
  • the solids fractions can have any distribution of the Dao / Dio ratio. However, they preferably have a narrow distribution, particularly preferably they have a narrow distribution with a Dgo / Dio ratio of 2 to 50, preferably 3 to 30.
  • the ceramic compositions comprise a bimodal solid mixture in which the volume fraction of the more finely divided particle fraction is between 5 and 50% by volume, preferably between 10 and 25% by volume, based on the total solid.
  • the ceramic compositions comprise a trimodal solid mixture in which, for example, the volume fraction of the coarse particle fraction is between 40 to 60% by volume, that of the average particle fraction between 20 to 30 and that of the fine particle fraction. Fraction is also between 20 to 30 vol .-%, based on the total solid.
  • the liquid portion of the ceramic compositions according to the invention comprises commercial plasticizers, plasticizers, solidifiers and sintering aids.
  • the proportion of ceramic solid is increased compared to conventional compositions by means of tailored particle size distribution without an increase in viscosity restricting the processability of the compositions.
  • the increased solids content in these masses results in a higher quality of the resulting ceramic products as well as a reduced expenditure of time and energy for the production of these products.
  • the invention relates to ceramic compositions for producing ceramic materials and products with low shrinkage.
  • the masses can be processed by extrusion, injection molding or casting and contain, compared to conventional ceramic masses, a powder fraction of at least 60% by volume, without an increase in viscosity limiting the processability of the masses.
  • the solids content can be increased by bimodal or multimodal distribution of the ceramic powders.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Ceramic Engineering (AREA)
  • Inorganic Chemistry (AREA)
  • Materials Engineering (AREA)
  • Structural Engineering (AREA)
  • Organic Chemistry (AREA)
  • Compositions Of Oxide Ceramics (AREA)
  • Press-Shaping Or Shaping Using Conveyers (AREA)

Abstract

The invention relates to ceramic compounds for producing ceramic materials and products having a low level of shrinkage. The compounds can be processed by extrusion, injection molding or casting and contain, in comparison with conventional ceramic compounds, a powder proportion of at least 60 vol. % without an increase in viscosity causing the processability of the compounds to be limited. A bi-modal or multi-modal distribution of the ceramic powders increases the proportion of solids.

Description

Beschreibungdescription
Keramische Massen mit hohem Feststoffanteil zur Herstellung keramischer Werkstoffe und Produkte mit geringem SchwundCeramic masses with a high solids content for the production of ceramic materials and products with low shrinkage
Die Erfindung betrifft keramische Massen zur Abformung keramischer Werkstoffe und/oder Produkte durch plastisches Ver- formen (Extrudieren, Spritzgießen) oder Gießen (Foliengießen, Schlickergießön) .The invention relates to ceramic compositions for molding ceramic materials and / or products by plastic shaping (extrusion, injection molding) or casting (film casting, slip casting).
Keramische Massen bestehen aus keramischen Pulvern, einem wässrigen Dispersionsmedium und einem oder mehreren Bindemittel, dem sog. Binder. Dieser Binder enthält wasserlösliche oder mit Wasser quellbare Polymermaterialien.Ceramic masses consist of ceramic powders, an aqueous dispersion medium and one or more binders, the so-called binder. This binder contains water-soluble or water-swellable polymer materials.
Zur Herstellung keramischer Massen werden mineralische Rohstoffe zu Pulver vermählen, granuliert und durch Zugabe von Wasser, Plastifizierungsmittel, Verfestigungsmittel und/oder Sinterhilfsmittel zu keramischen Massen aufbereitet. Mit die- sen Massen erfolgt die Formgebung. Dies kann durch Pressen, plastisches Verformen (Extrudieren, Spritzgießen) oder Gießen (Foliengießen, Schlickergießen) erfolgen. Nach der Formgebung wird getrocknet. Durch die bei der Trocknung entweichenden flüchtigen Bestandteile, im wesentlichen Wasser, schrumpft das Material. Nach Formgebung durch Gießen oder Spritzgießen, beträgt der Schwund bis zu 70 Vol.-%, da die Massen zur Sicherstellung der benötigten Fließfähigkeit bis zu 70 % Wasser enthalten. Die nach Trocknung erhaltenen Grünkörper werden ggf. mechanisch bearbeitet. Nach dieser Bearbeitung wird ge- sintert (gebrannt) . Dies geschieht durch Pyrolyse der Polymer- anteile. Beim Brand schrumpft der Werkstoff um weitere 20 bis 30 %.For the production of ceramic masses, mineral raw materials are ground into powder, granulated and prepared into ceramic masses by adding water, plasticizers, solidifying agents and / or sintering aids. The shaping takes place with these materials. This can be done by pressing, plastic forming (extrusion, injection molding) or casting (film casting, slip casting). After shaping, it is dried. The material shrinks due to the volatile constituents escaping during drying, essentially water. After shaping by casting or injection molding, the shrinkage is up to 70% by volume, since the masses contain up to 70% water to ensure the required flowability. The green bodies obtained after drying are optionally processed mechanically. After this processing, sintering (firing) takes place. This is done by pyrolysis of the polymer components. In the event of fire, the material shrinks by a further 20 to 30%.
Der Volumenschwund der Keramik beim Trocknen und Sintern ist abhängig vom Anteil des wässrigen und polymeren Dispersionsmediums, das für die Verarbeitbarkeit der keramischen Massen benötigt wird. Hierbei gilt, dass dieser Anteil umso größer ist, je komplexere Formen realisiert werden sollen und je besser die Massen deshalb bei der Formgebung durch Spritzguss oder Extrusion fließen müssen. Während für das Pressen ein Feuchtegehalt von 5 - 10% ausreicht, werden für die Extrusion ca. 25 bis 30 % Wasseranteil und für das Gießen ein Anteil von ca. 60 - 70 % benötigt. Durch den beim Trocknen und Sintern auftretenden Volumenschwund ist es kaum möglich, die Vorgaben der dreidimensionalen Abmessungen der Keramikprodukte ohne Nachbearbeitung zu realisieren. Deshalb ist in den meisten Fällen eine mechanische Nachbearbeitung erforderlich. Die Nachbearbeitung ist allerdings in Anbetracht der Härte keramischer Werkstoffe mit erheblichem Aufwand und Kosten verbunden.The volume shrinkage of the ceramic during drying and sintering depends on the proportion of the aqueous and polymeric dispersion medium that is required for the processability of the ceramic masses. Here it applies that this proportion is all the greater is, the more complex shapes are to be realized and the better the masses have to flow during molding by injection molding or extrusion. While a moisture content of 5 - 10% is sufficient for pressing, approx. 25 to 30% water content is required for extrusion and approx. 60 - 70% for casting. Due to the volume shrinkage occurring during drying and sintering, it is hardly possible to realize the specifications of the three-dimensional dimensions of the ceramic products without post-processing. Therefore, mechanical reworking is required in most cases. In view of the hardness of ceramic materials, however, post-processing involves considerable effort and cost.
Versucht man den Volumenschwund durch Erhöhung des Feststoffanteils der keramischen Massen aus herkömmlich hergestellten Mahlgütern zu reduzieren, so wird die Viskosität der Mischung erhöht. Das heißt, die Massen sind durch Extrusion und Spritzguss nicht mehr verarbeitbar.If one tries to reduce the volume loss by increasing the solids content of the ceramic masses from conventionally produced regrinds, the viscosity of the mixture is increased. This means that the masses can no longer be processed by extrusion and injection molding.
Aufgabe der vorliegenden Erfindung ist es, den Feststoffanteil in keramischen Massen unter Beibehaltung der guten Ver- arbeitbarkeit zu erhöhen, um den Schwund beim Trocknen, Entbindern und/oder Sintern der Keramik zu minimieren.The object of the present invention is to increase the solids content in ceramic compositions while maintaining good processability in order to minimize the shrinkage during drying, debinding and / or sintering of the ceramic.
Gegenstand der Erfindung sind keramische Massen, die durch Extrusion, Gießen und/oder Spritzguss verarbeitbar sind und die einen Feststoffanteil von mindestens 60 Vol.-% haben, wobei der Feststoffanteil als Kombination zumindest zweier Fraktionen, sogenannter Pulverfraktionen, mit unterschiedlicher Partikelgrößenverteilung vorliegt. Zudem ist Gegenstand der Erfindung die Verwendung dieser keramischen Massen zur Herstellung hochwertiger Keramikwerkstoffe mit geringem Schwund.The invention relates to ceramic compositions which can be processed by extrusion, casting and / or injection molding and which have a solids content of at least 60% by volume, the solids content being a combination of at least two fractions, so-called powder fractions, with different particle size distributions. The invention also relates to the use of these ceramic materials for producing high-quality ceramic materials with little shrinkage.
Vorteilhafte Ausgestaltungen der Erfindung ergeben sich aus den Unteransprüchen und der Beschreibung. Durch die Kombination von Feststofffraktionen unterschiedlicher Partikelgrößenverteilung wird die Schaffung dieser keramischen Massen möglich. Diese unterschiedlichen Feststoff- fraktionen werden aus unterschiedlichen Mahlprozessen erhalten, bei denen auf unterschiedliche Partikelgrößen (herunter) gemahlen wird. Die Kombination von Feststofffraktionen unterschiedlicher Partikelgrößenverteilung bewirkt eine höhere Packungsdichte des Feststoffanteils der keramischen Massen. Da- mit ist eine Erhöhung des Feststoffanteils machbar, die einen erheblich reduzierten Schwund des Werkstoffes zur Folge hat, sowohl bei der Trocknung zum Grünkörper als auch beim nachfolgenden Brand zur Keramik. Der reduzierte Schwund äußert sich in verbesserten Endeigenschaften der keramischen Produk- te, wie höhere Maßhaltigkeit, reduzierte Spannung im Material und verminderter Ausschuss. Durch die Tatsache, dass weniger Dispersionsmedium entfernt und/oder Binder pyrolysiert werden uss, ergeben sich als weitere Vorteile eine deutliche Reduzierung der benötigten Trocknungs- und Temperzeiten sowie ein deutlich reduzierter Energieaufwand.Advantageous embodiments of the invention result from the subclaims and the description. The combination of solid fractions with different particle size distributions makes it possible to create these ceramic materials. These different solid fractions are obtained from different grinding processes in which grinding is carried out to different particle sizes. The combination of solid fractions with different particle size distributions results in a higher packing density of the solid portion of the ceramic masses. This makes it possible to increase the solids content, which results in a considerably reduced shrinkage of the material, both during drying to form the green body and in the subsequent firing to the ceramic. The reduced shrinkage manifests itself in improved final properties of the ceramic products, such as higher dimensional accuracy, reduced tension in the material and reduced scrap. The fact that less dispersion medium has to be removed and / or binders need to be pyrolyzed has the further advantages of a significant reduction in the drying and annealing times required and a significantly reduced energy expenditure.
Die erfindungsgemäßen keramischen Massen umfassen vorteilhafterweise eine Kombination zumindest zweier Feststofffraktionen, die sich hinsichtlich ihrer mittleren Partikelgröße um den Faktor 4 - 5 unterscheiden. Bevorzugt beträgt die D5o- Partikelgröße der kleineren (feinkörnigeren oder feinteiligeren) Partikelfraktion <1 μm und die der größeren (gröberen, grobteiligeren) Partikelfraktion 1 - lOμm.The ceramic compositions according to the invention advantageously comprise a combination of at least two solid fractions which differ in their average particle size by a factor of 4-5. D is preferably 5 o- particle size of the smaller (finer or more finely divided) particle fraction of <1 micron and the larger (coarser, coarser) particle fraction 1 - lOμm.
Nach einer vorteilhaften Ausführungsform umfassen die erfindungsgemäßen keramischen Massen eine Kombination dreier Feststofffraktionen, die sich hinsichtlich ihrer Partikelgröße unterscheiden. Bevorzugt beträgt die D50-Partikelgröße der kleinsten Partikelfraktion <1 μm, die der mittleren Partikel- fraktion 1 - 10 μm und die der größten Partikelfraktion > 10 μm. Die Feststofffraktionen können eine beliebige Verteilung des Däo/Dio-Verhältnisses haben. Bevorzugt haben sie jedoch eine enge Verteilung, insbesondere bevorzugt haben sie eine enge Verteilung mit einem Dgo/Dio-Verhältnis von 2 bis 50, bevor- zugt von 3 bis 30.According to an advantageous embodiment, the ceramic compositions according to the invention comprise a combination of three solid fractions which differ in terms of their particle size. The D 50 particle size of the smallest particle fraction is preferably <1 μm, that of the middle particle fraction 1-10 μm and that of the largest particle fraction> 10 μm. The solids fractions can have any distribution of the Dao / Dio ratio. However, they preferably have a narrow distribution, particularly preferably they have a narrow distribution with a Dgo / Dio ratio of 2 to 50, preferably 3 to 30.
Nach einer vorteilhaften Ausführungsform umfassen die keramischen Massen ein bimodales Feststoffgemisch, bei dem der Volumenanteil der feinteiligeren Partikelfraktion zwischen 5 und 50 Vol.-%, bevorzugt zwischen 10 und 25 Vol.-%, bezogen auf den gesamten Feststoff, beträgt.According to an advantageous embodiment, the ceramic compositions comprise a bimodal solid mixture in which the volume fraction of the more finely divided particle fraction is between 5 and 50% by volume, preferably between 10 and 25% by volume, based on the total solid.
Nach einer besonders vorteilhaften Ausführungsform umfassen die keramischen Massen ein trimodales Feststoffgemisch, bei dem beispielsweise der Volumenanteil der grobteiligen Partikelfraktion zwischen 40 bis 60 Vol.-%, der der mittleren Partikelfraktion zwischen 20 bis 30 und der der feinteiligen. Fraktion ebenfalls zwischen 20 bis 30 Vol.-%, bezogen auf den gesamten Feststoff, beträgt.According to a particularly advantageous embodiment, the ceramic compositions comprise a trimodal solid mixture in which, for example, the volume fraction of the coarse particle fraction is between 40 to 60% by volume, that of the average particle fraction between 20 to 30 and that of the fine particle fraction. Fraction is also between 20 to 30 vol .-%, based on the total solid.
Der Flüssiganteil der erfindungsgemäßen keramischen Massen umfasst handelsübliche Verflüssigungsmittel, Plastifizie- rungsmittel, Verfestigungsmittel und Sinterhilfsmittel.The liquid portion of the ceramic compositions according to the invention comprises commercial plasticizers, plasticizers, solidifiers and sintering aids.
Die Vorteile der erfindungsgemäßen Massen gegenüber den bekannten keramischen Massen sind durch Beispiele belegt.The advantages of the compositions according to the invention over the known ceramic compositions are demonstrated by examples.
Bei den Massen gemäß der Erfindung ist gegenüber herkömmlichen Massen der Anteil des keramischen Feststoffs durch maß- geschneiderte Partikelgrößenverteilung erhöht, ohne dass eine Viskositätssteigerung die Verarbeitbarkeit der Massen einschränkt. Der erhöhte Feststoffanteil in diesen Massen bewirkt eine höhere Qualität der resultierenden keramischen Produkte so wie einen reduzierten Zeit- und Energieaufwand zur Herstellung dieser Produkte. Die Erfindung betrifft keramische Massen zur Herstellung keramischer Werkstoffe und Produkte mit geringem Schwund. Die Massen sind durch Extrusion, Spritzguss oder Gießen verarbeitbar und enthalten gegenüber herkömmlichen keramischen Massen einen Pulveranteil von zumindest 60 Vol.-%, ohne dass eine Viskositätssteigerung die Verarbeitbarkeit der Massen einschränken würde. Die Erhöhung des Feststoffanteils gelingt durch eine bi- oder multimodale Verteilung der keramischen Pulver. In the compositions according to the invention, the proportion of ceramic solid is increased compared to conventional compositions by means of tailored particle size distribution without an increase in viscosity restricting the processability of the compositions. The increased solids content in these masses results in a higher quality of the resulting ceramic products as well as a reduced expenditure of time and energy for the production of these products. The invention relates to ceramic compositions for producing ceramic materials and products with low shrinkage. The masses can be processed by extrusion, injection molding or casting and contain, compared to conventional ceramic masses, a powder fraction of at least 60% by volume, without an increase in viscosity limiting the processability of the masses. The solids content can be increased by bimodal or multimodal distribution of the ceramic powders.

Claims

Patentansprüche claims
1. Keramische Masse, die durch Extrusion, Gießen und/oder Spritzguss verarbeitbar ist und die einen Feststoffanteil von mindestens 60 Vol.-% hat, wobei der Feststoffanteil als Kombination zumindest zweier Fraktionen mit unterschiedlicher Partikelgrößenverteilung vorliegt .1. Ceramic mass which can be processed by extrusion, casting and / or injection molding and which has a solids content of at least 60% by volume, the solids content being a combination of at least two fractions with a different particle size distribution.
2. Keramische Masse nach Anspruch 1, bei der der Feststoffanteil im Bereich von 60 bis 80 Vol.-% liegt.2. Ceramic mass according to claim 1, wherein the solids content is in the range of 60 to 80 vol .-%.
3. Keramische Masse nach einem der Ansprüche 1 oder 2, wobei zwei Fraktionen des Feststoffanteils sich hinsichtlich ihrer mittleren Partikelgröße um den Faktor 4 - 5 unterscheiden.3. Ceramic mass according to one of claims 1 or 2, wherein two fractions of the solid fraction differ in their average particle size by a factor of 4-5.
4. Keramische Masse nach einem der vorstehenden Ansprüche, wobei der Feststoffanteil als eine Kombination zumindest dreier Fraktionen, die sich hinsichtlich ihrer Partikelgröße unterscheiden, vorliegt.4. Ceramic mass according to one of the preceding claims, wherein the solids content is present as a combination of at least three fractions which differ in terms of their particle size.
5. Keramische Masse nach einem der vorstehenden Ansprüche, wobei der Feststoffanteil zumindest eine Kombination zweier Fraktionen umfasst, bei der der Volumenanteil der feinteili- geren Partikelfraktion zwischen 5 und 50 Vol.-%, bezogen auf den gesamten Feststoffanteil, ausmacht.5. Ceramic mass according to one of the preceding claims, wherein the solids content comprises at least a combination of two fractions in which the volume fraction of the finely divided particle fraction is between 5 and 50 vol.%, Based on the total solids content.
6. Keramische Masse nach Anspruch 5, wobei der Feststoffanteil zumindest eine Kombination zweier Fraktionen umfasst, bei der der Volumenanteil der feinteiligeren Partikelfraktion zwischen 10 und 30 Vol.-%, bezogen auf den gesamten Feststoff, beträgt.6. Ceramic mass according to claim 5, wherein the solids content comprises at least a combination of two fractions, in which the volume fraction of the more finely divided particle fraction is between 10 and 30 vol .-%, based on the total solids.
7. Keramische Masse nach einem der vorstehenden Ansprüche, wobei der Feststoffanteil zumindest eine Kombination dreier7. Ceramic mass according to one of the preceding claims, wherein the solids content at least a combination of three
Fraktionen umfasst, bei der der Volumenanteil der grobteiligen Partikelfraktion zwischen 40 und 60 Vol.-%, der der itt- leren Partikelfraktion zwischen 20 und 30 Vol.-% und der der feinteiligen Fraktion zwischen 10 und 30 Vol.-%, bezogen auf den gesamten Feststoffanteil, beträgt.Fractions in which the volume fraction of the coarse particle fraction between 40 and 60 vol .-%, that of the itt- ler particle fraction between 20 and 30 vol .-% and that of the fine fraction between 10 and 30 vol .-%, based on the total solids content.
8. Verwendung von durch Extrusion, Gießen und Spritzguss verarbeitbaren keramischen Massen nach einem der Ansprüche 1 bis 1 , zur Herstellung hochwertiger Keramikwerkstoffe mit geringem Schwund. 8. Use of ceramic materials which can be processed by extrusion, casting and injection molding according to one of claims 1 to 1, for producing high-quality ceramic materials with low shrinkage.
EP03714683A 2002-02-28 2003-02-28 Ceramic compounds having a high proportion of solids for producing ceramic materials and products having a low level of shrinkage Withdrawn EP1478604A1 (en)

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