WO2017157747A1 - Ceramic suspension - Google Patents

Ceramic suspension Download PDF

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Publication number
WO2017157747A1
WO2017157747A1 PCT/EP2017/055505 EP2017055505W WO2017157747A1 WO 2017157747 A1 WO2017157747 A1 WO 2017157747A1 EP 2017055505 W EP2017055505 W EP 2017055505W WO 2017157747 A1 WO2017157747 A1 WO 2017157747A1
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WIPO (PCT)
Prior art keywords
ceramic
group
mixtures
suspension according
suspension
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PCT/EP2017/055505
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German (de)
French (fr)
Inventor
Dilyana Markova
Eric SCHWARZER
Mark Kelemen
Uwe Scheithauer
Tassilo Moritz
Original Assignee
Ceramtec Gmbh
Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V.
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Publication of WO2017157747A1 publication Critical patent/WO2017157747A1/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
    • C04B35/63—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 using additives specially adapted for forming the products, e.g.. binder binders
    • C04B35/632—Organic additives
    • 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
    • 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
    • C04B35/63—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 using additives specially adapted for forming the products, e.g.. binder binders
    • C04B35/632—Organic additives
    • C04B35/634—Polymers
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
    • G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
    • G03F7/0037—Production of three-dimensional images
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
    • G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
    • G03F7/004—Photosensitive materials
    • G03F7/0047—Photosensitive materials characterised by additives for obtaining a metallic or ceramic pattern, e.g. by firing
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
    • G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
    • G03F7/004—Photosensitive materials
    • G03F7/027—Non-macromolecular photopolymerisable compounds having carbon-to-carbon double bonds, e.g. ethylenic compounds
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
    • G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
    • G03F7/004—Photosensitive materials
    • G03F7/027—Non-macromolecular photopolymerisable compounds having carbon-to-carbon double bonds, e.g. ethylenic compounds
    • G03F7/028—Non-macromolecular photopolymerisable compounds having carbon-to-carbon double bonds, e.g. ethylenic compounds with photosensitivity-increasing substances, e.g. photoinitiators
    • G03F7/029—Inorganic compounds; Onium compounds; Organic compounds having hetero atoms other than oxygen, nitrogen or sulfur
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
    • G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
    • G03F7/004—Photosensitive materials
    • G03F7/027—Non-macromolecular photopolymerisable compounds having carbon-to-carbon double bonds, e.g. ethylenic compounds
    • G03F7/028—Non-macromolecular photopolymerisable compounds having carbon-to-carbon double bonds, e.g. ethylenic compounds with photosensitivity-increasing substances, e.g. photoinitiators
    • G03F7/031—Organic compounds not covered by group G03F7/029
    • 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
    • C04B2235/60—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
    • C04B2235/6026—Computer aided shaping, e.g. rapid prototyping

Definitions

  • the project that led to this patent application was funded by the European Union research and innovation program Horizon2020 under grant contract number 678503.
  • the present invention relates to suspensions containing ceramic particles (ceramic suspensions), a process for their preparation, and the use of the ceramic suspensions for additive (additive) manufacturing processes, in particular ceramic stereolithography-based additive manufacturing (ceramic SLA).
  • Ceramic SLA ceramic stereolithography-based additive manufacturing
  • a method that can be used for the additive production of ceramic materials is the laser-light or DLP-based stereolithography, wherein a ceramic powder is homogeneously dispersed in a photo-polymerizable organic binder system and can be prepared by selective exposure of the suspension, a ceramic green body, which can then be debinded into a finished product and, depending on the application, porous or dense sintered.
  • the individual components such as ceramic powder, solvents, binders and other components must be suitably coordinated so that both the processability of the suspension is given and after sintering densely sintered product is formed.
  • Known ceramic suspensions for the ceramic SLA process have the disadvantage that these compositions for some ceramic powders, in particular for non-surface modified alumina (Al 2 O 3 ), zirconia (ZrO 2 ) or silicon nitride (Si 3 N 4 ), unsuitable are.
  • suspensions are known which contain surface-modified ceramic or glass particles. The disadvantage of such particle surface modifications is that it means an additional overhead in the preparation of the ceramic powder to be used in the suspension.
  • known ceramic suspensions have the problem that they do not have a suitable viscosity at all shear rates.
  • the object of the present invention was therefore to develop suspensions with which unfunctionalized ceramic powder such.
  • unfunctionalized ceramic powder such as alumina (Al 2 O 3 ), zirconia (ZrO 2 ) and silicon nitride (Si 3 N 4 ), but also other ceramic materials can be processed by ceramic SLA method.
  • the object could be achieved by the ceramic suspension of claim 1 according to the invention. Preferred embodiments are specified in the subclaims.
  • the ceramic suspensions according to the invention comprise a) a solvent; b) a dispersant; c) an unfunctionalized ceramic powder; d) a monofunctional binder; e) a multifunctional binder (crosslinker); and f) a polymerization initiator.
  • the solvent (a) for the ceramic suspension according to the invention may be an organic solvent. Suitable organic solvents are organic Solvents which have a relatively high boiling point and a low vapor pressure and in which the binders used are soluble.
  • the solvent is preferably a branched or linear, monohydric or polyhydric, preferably mono- or dihydric, aliphatic alcohol having 2 to 10 carbon atoms, preferably 3 to 9 carbon atoms.
  • nonanol and 1, 2-propanediol are particularly preferred.
  • the solvent is contained in the suspension in an amount of 0.01 to 20 wt .-%, preferably 0.1 to 12 wt .-% based on the weight of the total suspension. It is also possible to use mixtures of two or more different solvents.
  • the dispersant (b) must be a dispersant which is capable of sufficiently dispersing the ceramic particles of the ceramic powder in the suspension. It is also possible to use mixtures of two or more dispersants.
  • the dispersant should be inert to free radicals that may occur in the polymerization, ie, for example, have no groups that are radically polymerizable.
  • Suitable dispersants are selected from the group consisting of organic compounds having a polar functional group, preferably amphiphilic homo- or copolymers having at least one polar functional group, more preferably an amphiphilic homopolymer having at least one polar functional group.
  • a suitable commercially available dispersant is, for example, BYK LPC 22124 (BYK) or Solsperse 3000.
  • the dispersant functions via a steric mechanism, ie a physical adsorption.
  • the amount of dispersant in the suspension is preferably less than 5% by weight, based on the weight of the ceramic powder, preferably between 0.5 and 3% by weight, based on the weight of the ceramic powder.
  • the non-functionalized ceramic powder (c) is selected from the group of oxide and non-oxide ceramics.
  • the unfunctionalized ceramic powder (c) is selected from the group consisting of powders of alumina (Al 2 O 3 ), zirconia (ZrO 2 ), silicon nitride (Si 3 N 4 ), silicon carbide (SIC), aluminum nitride (AIN ), Glass ceramic (SiO 2 ), titanium dioxide (TiO 2 ) and hydroxyapatite, and mixtures of aluminum oxide (Al 2 O 3 ) and zirconium oxide (ZrO 2 ) and mixtures of said ceramic powder or mixtures with other inorganic oxides, for example with the respective ceramic powder or mixtures of known sintering additives.
  • the unfunctionalized ceramic powder (c) is selected from the group consisting of powders of alumina (Al 2 O 3 ), zirconia (ZrO 2 ) and silicon nitride (Si 3 N 4 ), and mixtures of alumina (Al 2 O 3 ) and zirconium oxide (ZrO 2 ) and mixtures of said ceramic powders or mixtures with other inorganic oxides, for example with sintering additives known for the respective ceramic powders or mixtures.
  • non-functionalized in the sense of the present invention means that the ceramic powder is not surface-modified, in the sense that the ceramic powder, no organic substance is chemically applied to the surface or the surface of the ceramic particles is not chemically changed in the ceramic powder. Under the definition of the term fall both untreated, "bare" ceramic powder and the steric stabilization of the ceramic powder, for example by predispersing, because it does not cause a chemical change in the surface but the dispersant is at most physically adsorbed.
  • the particle size of the ceramic powder is in the range of 0.02 to 200 ⁇ (d50) (particle size measured by laser diffraction (eg Mastersizer 2000, Malvern, wet measurement)), preferably less than 10 ⁇ .
  • the ceramic powder is contained in the ceramic suspension in an amount of 30 to 90 wt .-% based on the weight of the total suspension, preferably in an amount of 50 to 90% by weight, based on the weight of the total suspension. With these amounts of ceramic powder, a suitable ratio to the organic components is given, so that a mechanically stable green body is formed.
  • the ceramic powder prior to preparation of the suspension, is ground in a mill together with dispersant and mixed (predispersed) to achieve the desired particle size and low viscosity of the ceramic suspension. Preferably, this also achieves a monomodal particle size distribution of the ceramic powder.
  • a preferred dispersant is BYK LPC 22124 (BYK).
  • the grinding of the ceramic powder is preferably carried out for 1 to 3 hours at a speed between 50 and 500 rpm, more preferably between 100 and 350 rpm.
  • the mill used may be, for example, a planetary ball mill.
  • the monofunctional binder (d) is one of the reactive compounds in the suspension through which an organic matrix is formed.
  • the binder is a monofunctional compound (has only one reactive group), which can be subjected to polymerization.
  • the binder is selected from the group consisting of (meth) acrylates and acrylamides, preferably acrylates.
  • the binder can also be a mixture of two or more binders. Suitable commercially available monofunctional binders are Laromer 8887 (BASF), SR217 (Arkema), A-SA NK ester (Kowa), HECLA (BASF), LA (lauryl acrylate) (BASF) and 4-HBA (4-hydroxybutyl acrylate). (BASF).
  • the binder is added to the suspension in an amount of from 1 to 50% by weight, based on the weight of the total suspension, preferably in an amount of from 1 to 10% by weight, based on the weight of the total suspension.
  • the crosslinker (e) is a multifunctional binder which has at least two reactive groups via which a polymerization is possible, or a mixture of two or more multifunctional binders.
  • the addition of a crosslinker results in the formation of a crosslinked polymer matrix.
  • the multifunctional binder (crosslinker) can be a di-, tri- or tetra-functional compound or a mixture of differently functional compounds.
  • the multifunctional binder (crosslinker) is preferably selected from the group consisting of functional (meth) acrylates.
  • the multifunctional binder (crosslinker) is added to the suspension in an amount of up to 40% by weight, based on the weight of the total suspension, preferably in an amount of from 1 to 20% by weight, based on the weight of the total suspension .
  • Suitable commercially available difunctional binders are Laromer TPGDA (BASF) and bisphenol A ethoxylate diacrylate (CAS: 64401 -02-1).
  • Suitable commercially available trifunctional binders are Ebecryl 83 (Allnex) and Ebecryl 160 (Allnex).
  • Suitable commercially available tetrafunctional binders are ATM 35E (Kowa), Ebecryl 40 (allnex) and di (trimethylolpropane) tetraacrylate (CAS: 94108-97-1).
  • the suspension according to the invention also comprises a polymerization initiator (f).
  • a photoinitiator is preferably used. Upon absorption of light, the photoinitiator decomposes, forms reactive species, and initiates polymerization.
  • the polymerization initiator is preferably selected from the group consisting of (bis) acylphosphine oxides and mixtures thereof, as well as camphor quinone / amine mixtures.
  • the amount of initiator contained in the ceramic suspension is in the range of 0.001 to 4 wt .-%, preferably 0.1 to 3 wt .-% based on the weight of entire suspension.
  • Suitable commercially available polymerization initiators are Irgacure 2022 (BASF), Genocure ITX (Rahn AG), Genocure CQ (Rahn AG), and Irgacure 819 (BASF).
  • the ceramic suspension has a shear-thinning or pseudoplastic behavior at a shear rate of between 0.1 and 100 l / s and preferably has a dynamic viscosity of 0.1 to 600 Pas.
  • the dynamic viscosity is preferably up to 300 Pas for a shear rate in the Range between 0.1 - 1 s "1 , more preferably the dynamic viscosity ⁇ 200 Pas in a shear rate range of 0.1 - 1 s " 1 and the dynamic viscosity is ⁇ 100 Pas in a shear rate range of 1 - 1000 s '
  • the dynamic viscosity can be measured with a commercially available rheometer, for example an Anton Paar MCR 302 (cone plate 25 mm, rotation mode). It is important that the ceramic suspension has a low viscosity in a wide range of different shear rates. Only then can complicated ceramic moldings with the ceramic SLA process can be produced.
  • the ceramic suspension thus prepared should be curable under blue or ultraviolet light.
  • the curing rate (curing rate) of the ceramic suspension according to the invention, within the process sequence of the respective ceramic stereolithography-based additive manufacturing process, should in particular be between 0.1 and 20 seconds.
  • the hardness rate depends on the layer thickness of the ceramic suspension produced in each case.
  • the conversion rate of the binders to the organic matrix (network) should be as high as possible.
  • the degree of crosslinking, together with the amount of ceramic powder, has an influence on the stability of the printed green body, which of course should be as high as possible.
  • the storage modulus G 'of the green body should be in the range of 10 5 to 10 8 Pa, preferably in the range of 10 6 to 10 7 Pa.
  • the memory module can be determined by means of known vibration rheometric measurements, for example an Anton Paar MCR 302 (oscillation mode).
  • the suspensions according to the invention can be prepared by successively adding the individual components (a) to (e) to a mixing container and mixing them.
  • the mixer is a high-speed planetary mixer (optionally in vacuum operation).
  • other mixing devices such as a drum mill can be used.
  • the duration of the mixing process should be comparatively short in order to save time as much as possible.
  • the finished suspension is to be prepared by a mixing time of less than 15 minutes, preferably less than 10 minutes, more preferably less than 3 minutes. It is important that a complete deagglomeration of the ceramic powder, as well as an effective dispersion can be achieved.
  • the ceramic suspensions of the invention may preferably be used for ceramic stereolithography-based additive manufacturing processes.
  • the ceramic green body is produced by means of ceramic stereolithography-based additive manufacturing processes.
  • individual points of the suspension by means of irradiation with light, preferably blue light, selectively cured and thus the green body formed successively.
  • the individual layers of ceramic suspension produced in the respective method have layer thicknesses ⁇ 100 ⁇ , preferably ⁇ 50 ⁇ , particularly preferably 5 to 25 ⁇ on.
  • the ceramic green body thus produced is first cleaned (cleaning with compressed air and subsequent cleaning with a solvent (eg an alcohol)) and then subjected to a heat treatment in a subsequent step.
  • the heat treatment includes curing the green body, debinding the green body to remove the binder or polymeric matrix, and sintering the green body.
  • the conditions in which the green body is debinded and sintered may vary depending on the composition of the organic matrix.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Ceramic Engineering (AREA)
  • Manufacturing & Machinery (AREA)
  • General Physics & Mathematics (AREA)
  • Inorganic Chemistry (AREA)
  • Spectroscopy & Molecular Physics (AREA)
  • Materials Engineering (AREA)
  • Structural Engineering (AREA)
  • Organic Chemistry (AREA)
  • Compositions Of Oxide Ceramics (AREA)

Abstract

The invention relate to suspensions which contain ceramic particles (ceramic suspensions), to a method for producing the suspensions and to the use of the ceramic suspensions for an additive (generative) production method, in particular the ceramic stereolithography-based additive method (ceramic-SLA).

Description

Keramische Suspension  Ceramic suspension
Das Projekt, das zu dieser Patentanmeldung geführt hat, wurde durch das Forschungs- und Innovationsprogramm Horizon2020 der Europäischen Union unter der Fördervertragsnummer 678503 gefördert. Gegenstand der vorliegenden Erfindung sind Suspensionen, die keramische Partikel enthalten (keramische Suspensionen), ein Verfahren zu deren Herstellung, sowie die Verwendung der keramischen Suspensionen für additive (generative) Fertigungsverfahren, insbesondere die keramische stereolithographiebasierte additive Fertigung (Keramik-SLA). Verfahren zur additiven Fertigung sind für verschiedenste Werkstoffe, insbesondere verschiedenste Arten von Kunststoffen aber auch für Metalle, hinlänglich bekannt. Ein Verfahren das für die additive Fertigung von keramischen Materialien genutzt werden kann ist die laserlicht- oder DLP-basierte Stereolithographie, wobei ein Keramikpulver in einem photo-polymerisierbaren organischen Bindersystem homogen dispergiert ist und durch selektive Belichtung der Suspension ein Keramik- Grünkörper hergestellt werden kann, der danach zum fertigen Produkt entbindert und je nach Anwendung porös oder dicht gesintert werden kann. The project that led to this patent application was funded by the European Union research and innovation program Horizon2020 under grant contract number 678503. The present invention relates to suspensions containing ceramic particles (ceramic suspensions), a process for their preparation, and the use of the ceramic suspensions for additive (additive) manufacturing processes, in particular ceramic stereolithography-based additive manufacturing (ceramic SLA). Processes for additive production are well known for a wide variety of materials, especially various types of plastics but also for metals. A method that can be used for the additive production of ceramic materials is the laser-light or DLP-based stereolithography, wherein a ceramic powder is homogeneously dispersed in a photo-polymerizable organic binder system and can be prepared by selective exposure of the suspension, a ceramic green body, which can then be debinded into a finished product and, depending on the application, porous or dense sintered.
Bei keramischen Suspensionen, die im Keramik-SLA-Verfahren verwendet werden können, müssen die einzelnen Komponenten, wie Keramikpulver, Lösemittel, Binder und andere Komponenten in geeigneter Weise aufeinander abgestimmt werden, damit sowohl die Prozessierbarkeit der Suspension gegeben ist als auch nach dem Sintern ein dicht-gesintertes Produkt entsteht. For ceramic suspensions that can be used in the ceramic SLA process, the individual components, such as ceramic powder, solvents, binders and other components must be suitably coordinated so that both the processability of the suspension is given and after sintering densely sintered product is formed.
Bekannte keramische Suspensionen für das Keramik-SLA-Verfahren weisen den Nachteil auf, dass diese Zusammensetzungen für manche Keramikpulver, insbesondere für nicht Oberflächen modifiziertes Aluminiumoxid (AI2O3), Zirkoniumoxid (ZrO2) oder Siliziumnitrid (Si3N4), ungeeignet sind. Im Stand der Technik, wie beispielsweise der EP 2 151 214 A1 , sind Suspensionen bekannt, die oberflächenmodifizierte Keramik- oder Glaspartikel enthalten. Der Nachteil solcher Partikel-Oberflächenmodifikationen ist, dass es einen zusätzlichen Mehraufwand bei der Herstellung des in der Suspension zu verwendenden Keramikpulvers bedeutet. Known ceramic suspensions for the ceramic SLA process have the disadvantage that these compositions for some ceramic powders, in particular for non-surface modified alumina (Al 2 O 3 ), zirconia (ZrO 2 ) or silicon nitride (Si 3 N 4 ), unsuitable are. In the prior art, such as EP 2 151 214 A1, suspensions are known which contain surface-modified ceramic or glass particles. The disadvantage of such particle surface modifications is that it means an additional overhead in the preparation of the ceramic powder to be used in the suspension.
Zudem weisen bekannte keramische Suspensionen das Problem auf, dass diese nicht bei allen Scherraten eine geeignete Viskosität aufweisen. In addition, known ceramic suspensions have the problem that they do not have a suitable viscosity at all shear rates.
Die Aufgabe der vorliegenden Erfindung bestand deshalb darin, Suspensionen zu entwickeln, mit denen sich nicht funktionalisierte Keramikpulver wie z. B. Aluminiumoxid (AI2O3), Zirkoniumoxid (ZrO2) und Siliziumnitrid (Si3N4), aber auch andere keramische Werkstoffe mittels Keramik-SLA-Verfahren bearbeiten lassen. Die Aufgabe konnte durch die erfindungsgemäßen keramischen Suspension nach Anspruch 1 gelöst werden. Bevorzugte Ausführungsformen sind in den Unteransprüchen angegeben. The object of the present invention was therefore to develop suspensions with which unfunctionalized ceramic powder such. As alumina (Al 2 O 3 ), zirconia (ZrO 2 ) and silicon nitride (Si 3 N 4 ), but also other ceramic materials can be processed by ceramic SLA method. The object could be achieved by the ceramic suspension of claim 1 according to the invention. Preferred embodiments are specified in the subclaims.
Die erfindungsgemäße keramische Suspensionen umfasst a) ein Lösemittel; b) ein Dispergiermittel; c) ein nicht funktionalisiertes Keramikpulver; d) einen monofunktionellen Binder; e) einen multifunktionellen Binder (Vernetzer); und f) einen Polymerisationsinitiator. Das Lösemittel (a) für die erfindungsgemäße keramische Suspension kann ein organisches Lösemittel sein. Geeignete organische Lösemittel sind organische Lösemittel, die einen relativ hohen Siedepunkt sowie einen geringen Dampfdruck aufweisen und in denen die verwendeten Binder löslich sind. Das Lösemittel ist bevorzugt ein verzweigter oder linearer, einwertiger oder mehrwertiger, vorzugsweise ein- oder zweiwertiger, aliphatischer Alkohol mit 2 bis 10 Kohlenstoffatomen, bevorzugt 3 bis 9 Kohlenstoffatomen. Besonders bevorzugt sind Nonanol und 1 ,2-Propandiol. Das Lösemittel ist in der Suspension in einer Menge von 0,01 bis 20 Gew.-%, bevorzugt 0,1 bis 12 Gew.-% bezogen auf das Gewicht der gesamten Suspension enthalten. Möglich ist auch der Einsatz von Mischungen aus zwei oder mehr verschiedenen Lösemitteln. Das Dispergiermittel (b) muss ein Dispergiermittel sein, welches geeignet ist die Keramikpartikel des Keramikpulvers in der Suspension in ausreichendem Maße zu dispergieren. Es können auch Mischungen von zwei oder mehr Dispergiermitteln eingesetzt werden. Das Dispergiermittel sollte inert gegenüber freien Radikalen sein, die bei der Polymerisation auftreten können, d.h. beispielsweise keine Gruppen aufweisen, die radikalisch polymerisierbar sind. Dafür eignen sich Dispergiermittel ausgewählt aus der Gruppe, bestehend aus organischen Verbindungen, die eine polare funktionelle Gruppe aufweisen, vorzugsweise amphiphile Homo- oder Copolymere, die mindestens eine polare funktionelle Gruppe aufweisen, besonders bevorzugt ein amphiphiles Homopolymer mit mindestens einer polaren funktionellen Gruppe. Ein geeignetes kommerziell erhältliches Dispergiermittel ist beispielsweise BYK LPC 22124 (BYK) oder Solsperse 3000. Das Dispergiermittel funktioniert über einen sterischen Mechanismus, also eine physikalische Adsorption. Die Menge an Dispergiermittel in der Suspension ist vorzugsweise weniger als 5 Gew.-% bezogen auf das Gewicht des keramischen Pulvers, vorzugsweise zwischen 0,5 und 3 Gew.-% bezogen auf das Gewicht des keramischen Pulvers. Die Auswahl des Dispergiermittels sorgt dafür, dass eine homogene stabile Suspension entsteht, wodurch eine gleichbleibende Materialverteilung während des Verfahrens erreicht wird. Das nicht funktionalisierte Keramikpulver (c) ist ausgewählt aus der Gruppe der Oxid- und Nichtoxidkeramiken. In einer bevorzugten Ausführungsform wird das nicht funktionalisierte Keramikpulver (c) aus der Gruppe, bestehend aus Pulvern von Aluminiumoxid (AI2O3), Zirkoniumoxid (ZrO2), Siliziumnitrid (Si3N4), Siliciumcarbid (SIC), Aluminiumnitrid (AIN), Glaskeramik (SiO2), Titandioxid (TiO2) und Hydroxylapatit, sowie Mischungen aus Aluminiumoxid (AI2O3) und Zirkoniumoxid (ZrO2) und Mischungen der genannten Keramikpulver oder Mischungen mit anderen anorganischen Oxiden, beispielsweise mit für die jeweiligen Keramikpulver oder Mischungen bekannten Sinteradditiven, ausgewählt. In einer besonders bevorzugten Ausführungsformwird das nicht funktionalisierte Keramikpulver (c) aus der Gruppe, bestehend aus Pulvern von Aluminiumoxid (AI2O3), Zirkoniumoxid (ZrO2) und Siliziumnitrid (Si3N4), sowie Mischungen aus Aluminiumoxid (AI2O3) und Zirkoniumoxid (ZrO2) und Mischungen der genannten Keramikpulver oder Mischungen mit anderen anorganischen Oxiden, beispielsweise mit für die jeweiligen Keramikpulver oder Mischungen bekannten Sinteradditiven, ausgewählt. The ceramic suspensions according to the invention comprise a) a solvent; b) a dispersant; c) an unfunctionalized ceramic powder; d) a monofunctional binder; e) a multifunctional binder (crosslinker); and f) a polymerization initiator. The solvent (a) for the ceramic suspension according to the invention may be an organic solvent. Suitable organic solvents are organic Solvents which have a relatively high boiling point and a low vapor pressure and in which the binders used are soluble. The solvent is preferably a branched or linear, monohydric or polyhydric, preferably mono- or dihydric, aliphatic alcohol having 2 to 10 carbon atoms, preferably 3 to 9 carbon atoms. Particularly preferred are nonanol and 1, 2-propanediol. The solvent is contained in the suspension in an amount of 0.01 to 20 wt .-%, preferably 0.1 to 12 wt .-% based on the weight of the total suspension. It is also possible to use mixtures of two or more different solvents. The dispersant (b) must be a dispersant which is capable of sufficiently dispersing the ceramic particles of the ceramic powder in the suspension. It is also possible to use mixtures of two or more dispersants. The dispersant should be inert to free radicals that may occur in the polymerization, ie, for example, have no groups that are radically polymerizable. Suitable dispersants are selected from the group consisting of organic compounds having a polar functional group, preferably amphiphilic homo- or copolymers having at least one polar functional group, more preferably an amphiphilic homopolymer having at least one polar functional group. A suitable commercially available dispersant is, for example, BYK LPC 22124 (BYK) or Solsperse 3000. The dispersant functions via a steric mechanism, ie a physical adsorption. The amount of dispersant in the suspension is preferably less than 5% by weight, based on the weight of the ceramic powder, preferably between 0.5 and 3% by weight, based on the weight of the ceramic powder. The selection of the dispersant ensures that a homogeneous stable suspension is formed, whereby a uniform material distribution is achieved during the process. The non-functionalized ceramic powder (c) is selected from the group of oxide and non-oxide ceramics. In a preferred embodiment, the unfunctionalized ceramic powder (c) is selected from the group consisting of powders of alumina (Al 2 O 3 ), zirconia (ZrO 2 ), silicon nitride (Si 3 N 4 ), silicon carbide (SIC), aluminum nitride (AIN ), Glass ceramic (SiO 2 ), titanium dioxide (TiO 2 ) and hydroxyapatite, and mixtures of aluminum oxide (Al 2 O 3 ) and zirconium oxide (ZrO 2 ) and mixtures of said ceramic powder or mixtures with other inorganic oxides, for example with the respective ceramic powder or mixtures of known sintering additives. In a particularly preferred embodiment, the unfunctionalized ceramic powder (c) is selected from the group consisting of powders of alumina (Al 2 O 3 ), zirconia (ZrO 2 ) and silicon nitride (Si 3 N 4 ), and mixtures of alumina (Al 2 O 3 ) and zirconium oxide (ZrO 2 ) and mixtures of said ceramic powders or mixtures with other inorganic oxides, for example with sintering additives known for the respective ceramic powders or mixtures.
Der Begriff „nicht funktionalisiert" im Sinne der vorliegenden Erfindung bedeutet, dass das Keramikpulver nicht oberflächenmodifiziert wird, in dem Sinne, dass das Keramikpulver keine organische Substanz chemisch auf die Oberfläche aufgebracht wird bzw. die Oberfläche der Keramikpartikel in dem Keramikpulver chemisch nicht verändert wird. Unter die Definition des Begriffes fallen sowohl unbehandelte, „nackte" Keramikpulver als auch die sterische Stabilisation des Keramikpulvers, beispielsweise durch ein Vordispergieren, weil dadurch keine chemische Veränderung der Oberfläche eintritt sondern das Dispergiermittel höchstens physikalische adsorbiert wird. Die Partikelgröße des Keramikpulvers liegt im Bereich von 0,02 - 200 μιτι (d50) (Partikelgröße gemessen mittels Laserbeugung (z.B. Mastersizer 2000, Malvern, Nassmessung)), vorzugsweise kleiner als 10 μιτι. Das Keramikpulver ist in der keramischen Suspension in einer Menge von 30 bis 90 Gew.-% bezogen auf das Gewicht der gesamten Suspension enthalten, bevorzugt in einer Menge von 50 bis 90 Gew.-% bezogen auf das Gewicht der gesamten Suspension. Bei diesen Mengen an Keramikpulver ist ein geeignetes Verhältnis zu den organischen Komponenten gegeben, sodass ein mechanisch stabiler Grünkörper entsteht. The term "non-functionalized" in the sense of the present invention means that the ceramic powder is not surface-modified, in the sense that the ceramic powder, no organic substance is chemically applied to the surface or the surface of the ceramic particles is not chemically changed in the ceramic powder. Under the definition of the term fall both untreated, "bare" ceramic powder and the steric stabilization of the ceramic powder, for example by predispersing, because it does not cause a chemical change in the surface but the dispersant is at most physically adsorbed. The particle size of the ceramic powder is in the range of 0.02 to 200 μιτι (d50) (particle size measured by laser diffraction (eg Mastersizer 2000, Malvern, wet measurement)), preferably less than 10 μιτι. The ceramic powder is contained in the ceramic suspension in an amount of 30 to 90 wt .-% based on the weight of the total suspension, preferably in an amount of 50 to 90% by weight, based on the weight of the total suspension. With these amounts of ceramic powder, a suitable ratio to the organic components is given, so that a mechanically stable green body is formed.
In einer bevorzugten Ausführungsform wird das Keramikpulver vor der Herstellung der Suspension zusammen mit Dispergiermittel in einer Mühle gemahlen und gemischt (Vordispergieren), um die gewünschte Partikelgröße und eine niedrige Viskosität der keramischen Suspension zu erreichen. Vorzugsweise wird dadurch auch eine monomodale Partikelgrößenverteilung des Keramikpulvers erreicht. Ein bevorzugtes Dispergiermittel ist BYK LPC 22124 (BYK). Das Mahlen des Keramikpulvers erfolgt vorzugsweise zwischen 1 und 3 Stunden bei einer Geschwindigkeit zwischen 50 und 500 rpm, besonders bevorzugt zwischen 100 und 350 rpm. Die verwendete Mühle kann beispielsweise eine Planetenkugelmühle sein. In a preferred embodiment, prior to preparation of the suspension, the ceramic powder is ground in a mill together with dispersant and mixed (predispersed) to achieve the desired particle size and low viscosity of the ceramic suspension. Preferably, this also achieves a monomodal particle size distribution of the ceramic powder. A preferred dispersant is BYK LPC 22124 (BYK). The grinding of the ceramic powder is preferably carried out for 1 to 3 hours at a speed between 50 and 500 rpm, more preferably between 100 and 350 rpm. The mill used may be, for example, a planetary ball mill.
Der monofunktionelle Binder (d) ist eine der reaktiven Verbindungen in der Suspension, durch den eine organische Matrix gebildet wird. Der Binder ist dabei eine monofunktionelle Verbindung (weist nur eine reaktive Gruppe auf), welche einer Polymerisation unterworfen werden kann. Der Binder ist dabei ausgewählt aus der Gruppe, bestehend aus (Meth)acrylaten und Acrylamiden, vorzugsweise Acrylate. Der Binder kann auch eine Mischung von zwei oder mehr Bindern sein. Geeignete kommerziell erhältliche monofunktionelle Binder sind Laromer 8887 (BASF), SR217 (Arkema), A-SA NK ester (Kowa), HECLA (BASF), LA (Lauryl Acrylate) (BASF) und 4-HBA (4-Hydroxy butyl acrylat) (BASF). Der Binder wird der Suspension in einer Menge von 1 bis 50 Gew.-% bezogen auf das Gewicht der gesamten Suspension zugegeben, bevorzugt in einer Menge von 1 bis 10 Gew.-% bezogen auf das Gewicht der gesamten Suspension. Der Vernetzer (e) ist ein multifunktioneller Binder, welcher mindestens zwei reaktive Gruppen aufweist über die eine Polymerisation möglich ist, oder eine Mischung aus zwei oder mehr multifunktionellen Bindern. Die Zugabe eines Vernetzers führt dazu, dass eine vernetzte Polymermatrix entsteht. Durch die Variation der Menge des Vernetzers oder die Anzahl der reaktiven Gruppen können die Eigenschaften des Grünkörpers beeinflusst werden. The monofunctional binder (d) is one of the reactive compounds in the suspension through which an organic matrix is formed. The binder is a monofunctional compound (has only one reactive group), which can be subjected to polymerization. The binder is selected from the group consisting of (meth) acrylates and acrylamides, preferably acrylates. The binder can also be a mixture of two or more binders. Suitable commercially available monofunctional binders are Laromer 8887 (BASF), SR217 (Arkema), A-SA NK ester (Kowa), HECLA (BASF), LA (lauryl acrylate) (BASF) and 4-HBA (4-hydroxybutyl acrylate). (BASF). The binder is added to the suspension in an amount of from 1 to 50% by weight, based on the weight of the total suspension, preferably in an amount of from 1 to 10% by weight, based on the weight of the total suspension. The crosslinker (e) is a multifunctional binder which has at least two reactive groups via which a polymerization is possible, or a mixture of two or more multifunctional binders. The addition of a crosslinker results in the formation of a crosslinked polymer matrix. By varying the amount of Crosslinking agent or the number of reactive groups, the properties of the green body can be influenced.
Der multifunktioneller Binder (Vernetzer) kann eine di-, tri- oder tetrafunktionelle Verbindung sein oder eine Mischung aus unterschiedlich funktioneller Verbindungen. Der multifunktioneller Binder (Vernetzer) ist bevorzugt ausgewählt aus der Gruppe, bestehend aus funktionellen (Meth)acrylaten. Der multifunktioneller Binder (Vernetzer) wird in einer Menge von bis zu 40 Gew.-%, bezogen auf das Gewicht der gesamten Suspension, zur Suspension gegeben, bevorzugt in einer Menge von 1 bis 20 Gew.-% bezogen auf das Gewicht der gesamten Suspension. Geeignete kommerziell erhältliche difunktionelle Binder sind Laromer TPGDA (BASF) und Bisphenol A ethoxylate diacrylate (CAS: 64401 -02-1 ). Geeignete kommerziell erhältliche trifunktionelle Binder sind Ebecryl 83 (Allnex) und Ebecryl 160 (Allnex). Geeignete kommerzielle erhältliche tetrafunktionelle Binder sind ATM- 35E (Kowa), Ebecryl 40 (Allnex) und Di(trimethylolpropane) tetraacrylate (CAS: 94108-97-1 ). The multifunctional binder (crosslinker) can be a di-, tri- or tetra-functional compound or a mixture of differently functional compounds. The multifunctional binder (crosslinker) is preferably selected from the group consisting of functional (meth) acrylates. The multifunctional binder (crosslinker) is added to the suspension in an amount of up to 40% by weight, based on the weight of the total suspension, preferably in an amount of from 1 to 20% by weight, based on the weight of the total suspension , Suitable commercially available difunctional binders are Laromer TPGDA (BASF) and bisphenol A ethoxylate diacrylate (CAS: 64401 -02-1). Suitable commercially available trifunctional binders are Ebecryl 83 (Allnex) and Ebecryl 160 (Allnex). Suitable commercially available tetrafunctional binders are ATM 35E (Kowa), Ebecryl 40 (allnex) and di (trimethylolpropane) tetraacrylate (CAS: 94108-97-1).
Erst durch die geeignete Kombination von multifunktionellem Binder (Vernetzer) und monofunktionellem Binder kann eine schnell härtende Suspension entstehen, wodurch die selektiv belichteten Stellen bei der keramischen stereolithographiebasierten additiven Fertigung schneller aushärten und die Prozess- bzw. Umwandlungsrate gesteigert werden kann. Only by the appropriate combination of multifunctional binder (crosslinker) and monofunctional binder can a fast-curing suspension arise, whereby the selectively exposed sites in the ceramic stereolithography-based additive manufacturing cure faster and the process or conversion rate can be increased.
Die erfindungsgemäße Suspension umfasst auch einen Polymerisationsinitiator (f). Für die keramische stereolithographiebasierte additive Fertigung wird vorzugsweise ein Photoinitiator eingesetzt. Durch Absorption von Licht zerfällt der Photoinitiator, bildet reaktive Spezies und startet die Polymerisation. Der Polymerisationsinitiator ist bevorzugt ausgewählt aus der Gruppe, bestehend aus (Bis)acylphosphinoxiden und Mischungen daraus, sowie Campherchinon/Amin-Mischungen. Die Menge an Initiator, die in der keramischen Suspension enthalten ist, liegt im Bereich zwischen 0,001 bis 4 Gew.-%, vorzugsweise 0,1 bis 3 Gew.-% bezogen auf das Gewicht der gesamten Suspension. Geeignete kommerzielle erhältliche Polymerisationsinititatoren sind Irgacure 2022 (BASF), Genocure ITX (Rahn AG), Genocure CQ (Rahn AG), und Irgacure 819 (BASF). The suspension according to the invention also comprises a polymerization initiator (f). For ceramic stereolithography-based additive manufacturing, a photoinitiator is preferably used. Upon absorption of light, the photoinitiator decomposes, forms reactive species, and initiates polymerization. The polymerization initiator is preferably selected from the group consisting of (bis) acylphosphine oxides and mixtures thereof, as well as camphor quinone / amine mixtures. The amount of initiator contained in the ceramic suspension is in the range of 0.001 to 4 wt .-%, preferably 0.1 to 3 wt .-% based on the weight of entire suspension. Suitable commercially available polymerization initiators are Irgacure 2022 (BASF), Genocure ITX (Rahn AG), Genocure CQ (Rahn AG), and Irgacure 819 (BASF).
Die keramische Suspension weist ein scherentzähendes bzw. strukturviskoses Verhalten bei einer Scherrate von zwischen 0,1 - 100 1/s auf und bevorzugt eine dynamische Viskosität von 0,1 bis 600 Pas, Bevorzugt beträgt die dynamische Viskosität bis zu 300 Pas für eine Scherrate im Bereich zwischen 0,1 - 1 s"1, besonders bevorzugt ist die dynamische Viskosität < 200 Pas in einem Scherratenbereich von 0,1 - 1 s"1 und die dynamische Viskosität ist < 100 Pas in einem Scherratenbereich von 1 - 1000 s' Die dynamische Viskosität kann mit einem handelsüblichen Rheometer, beispielsweise einem Anton Paar MCR 302 (Kegel-Platte 25 mm; Rotationsmodus) gemessen werden. Dabei ist es wichtig, dass die keramische Suspension eine geringe Viskosität in einem großen Bereich verschiedener Scherraten aufweist. Erst dadurch können komplizierte keramische Formkörper mit dem Keramik-SLA-Verfahren hergestellt werden. The ceramic suspension has a shear-thinning or pseudoplastic behavior at a shear rate of between 0.1 and 100 l / s and preferably has a dynamic viscosity of 0.1 to 600 Pas. The dynamic viscosity is preferably up to 300 Pas for a shear rate in the Range between 0.1 - 1 s "1 , more preferably the dynamic viscosity <200 Pas in a shear rate range of 0.1 - 1 s " 1 and the dynamic viscosity is <100 Pas in a shear rate range of 1 - 1000 s ' The dynamic viscosity can be measured with a commercially available rheometer, for example an Anton Paar MCR 302 (cone plate 25 mm, rotation mode). It is important that the ceramic suspension has a low viscosity in a wide range of different shear rates. Only then can complicated ceramic moldings with the ceramic SLA process can be produced.
Die so hergestellte keramische Suspension sollte unter blauem bzw. ultraviolettem Licht härtbar sein. Die Härtungsgeschwindigkeit (curing rate) der erfindungsgemäßen keramischen Suspension, innerhalb des Prozessablaufs des jeweiligen keramischen stereolithographiebasierten additiven Fertigungsverfahrens, sollte insbesondere zwischen 0,1 bis 20 Sekunden liegen. Die Härtegeschwindigkeit ist dabei abhängig von der beim jeweiligen Verfahren erzeugten Schichtstärke der keramischen Suspension. The ceramic suspension thus prepared should be curable under blue or ultraviolet light. The curing rate (curing rate) of the ceramic suspension according to the invention, within the process sequence of the respective ceramic stereolithography-based additive manufacturing process, should in particular be between 0.1 and 20 seconds. The hardness rate depends on the layer thickness of the ceramic suspension produced in each case.
Zudem sollte die Umwandlungsrate der Binder zur organischen Matrix (Netzwerk) so hoch wie möglich sein. Der Vernetzungsgrad hat zusammen mit der Menge an Keramikpulver einen Einfluss auf die Stabilität des gedruckten Grünkörpers, die natürlich möglichst hoch sein soll. Das Speichermodul G' des Grünkörpers sollte im Bereich von 105 bis 108 Pa liegen, bevorzugt im Bereich von 106 bis 107 Pa. Das Speichermodul kann mittels bekannten schwingungsrheometrischen Messungen ermittelt werden, beispielsweise einem Anton Paar MCR 302 (Oszillationsmodus). Die erfindungsgemäßen Suspensionen können hergestellt werden, indem die einzelnen Komponenten (a) bis (e) sukzessive in einen Mischungsbehälter gegeben und vermischt werden. Alternativ ist auch ein Verfahren denkbar bei dem erst die organischen Komponenten vermischt werden und danach erst das Keramikpulver zugegeben wird. Dadurch kann eine verbesserte Lösung des Initiators erreicht werden. Als Mischgerät eignet sich ein Hochgeschwindigkeits-Planetenmischer (optional im Vakuumbetrieb). Alternativ können auch andere Mischgeräte, wie z. B. eine Trommelmühle, verwendet werden. Die Dauer des Mischvorgangs sollte vergleichsweise kurz sein, um möglichst zeitsparend zu arbeiten. Erfindungsgemäß ist die fertige Suspension durch eine Mischdauer von weniger als 15 Minuten, vorzugsweise weniger als 10 Minuten, besonders bevorzugt weniger als 3 Minuten herzustellen. Dabei ist wichtig, dass eine vollständige Deagglomeration des Keramikpulvers, sowie ein effektives Dispergieren erreicht werden kann. In addition, the conversion rate of the binders to the organic matrix (network) should be as high as possible. The degree of crosslinking, together with the amount of ceramic powder, has an influence on the stability of the printed green body, which of course should be as high as possible. The storage modulus G 'of the green body should be in the range of 10 5 to 10 8 Pa, preferably in the range of 10 6 to 10 7 Pa. The memory module can be determined by means of known vibration rheometric measurements, for example an Anton Paar MCR 302 (oscillation mode). The suspensions according to the invention can be prepared by successively adding the individual components (a) to (e) to a mixing container and mixing them. Alternatively, a method is conceivable in which only the organic components are mixed and then only the ceramic powder is added. As a result, an improved solution of the initiator can be achieved. The mixer is a high-speed planetary mixer (optionally in vacuum operation). Alternatively, other mixing devices, such. As a drum mill can be used. The duration of the mixing process should be comparatively short in order to save time as much as possible. According to the invention, the finished suspension is to be prepared by a mixing time of less than 15 minutes, preferably less than 10 minutes, more preferably less than 3 minutes. It is important that a complete deagglomeration of the ceramic powder, as well as an effective dispersion can be achieved.
Die erfindungsgemäßen keramischen Suspensionen können vorzugsweise für keramische stereolithographiebasierte additive Fertigungsverfahren verwendet werden. The ceramic suspensions of the invention may preferably be used for ceramic stereolithography-based additive manufacturing processes.
Nach Herstellung der keramischen Suspension wird der keramische Grünkörper mittels keramischer stereolithographiebasierter additiver Fertigungsverfahren erzeugt. Dabei werden einzelne Stellen der Suspension mittels Bestrahlung mit Licht, vorzugsweise blauem Licht, selektiv ausgehärtet und so der Grünkörper sukzessive gebildet. Die einzelnen bei dem jeweiligen Verfahren erzeugten Schichten aus keramischer Suspension weisen dabei Schichtdicken < 100 μιτι, bevorzugt < 50 μιτι, besonders bevorzugt 5 bis 25 μιτι, auf. Der so hergestellte keramische Grünkörper wird zunächst gereinigt (Reinigung mit Pressluft und nachfolgender Reinigung mit einem Lösemittel (z. B. einem Alkohol)) und dann in einem nachfolgenden Schritt einer Wärmebehandlung unterzogen. Die Wärmebehandlung umfasst das Härten des Grünkörpers, das Entbindern des Grünkörpers, um den Binder bzw. die polymere Matrix zu entfernen, und das Sintern des Grünkörpers. After the ceramic suspension has been produced, the ceramic green body is produced by means of ceramic stereolithography-based additive manufacturing processes. In this case, individual points of the suspension by means of irradiation with light, preferably blue light, selectively cured and thus the green body formed successively. The individual layers of ceramic suspension produced in the respective method have layer thicknesses <100 μιτι, preferably <50 μιτι, particularly preferably 5 to 25 μιτι on. The ceramic green body thus produced is first cleaned (cleaning with compressed air and subsequent cleaning with a solvent (eg an alcohol)) and then subjected to a heat treatment in a subsequent step. The heat treatment includes curing the green body, debinding the green body to remove the binder or polymeric matrix, and sintering the green body.
Die Bedingungen untern denen der Grünkörper entbindert und gesintert wird können in Abhängigkeit von der Zusammensetzung der organischen Matrix variieren. The conditions in which the green body is debinded and sintered may vary depending on the composition of the organic matrix.

Claims

Ansprüche claims
1 . Keramische Suspension, umfassend: a) ein Lösemittel; b) ein Dispergiermittel; c) ein nicht funktionalisiertes Keramikpulver; d) einen monofunktionellen Binder; e) einen multifunktionellen Binder (Vernetzer); und f) einen Polymerisationsinitiator. 1 . A ceramic suspension comprising: a) a solvent; b) a dispersant; c) an unfunctionalized ceramic powder; d) a monofunctional binder; e) a multifunctional binder (crosslinker); and f) a polymerization initiator.
2. Keramische Suspension nach Anspruch 1 , dadurch gekennzeichnet, dass das Lösemittel (a) ein organisches Lösemittel, bevorzugt ein verzweigter oder linearer, einwertiger oder mehrwertiger, vorzugsweise ein- oder zweiwertiger, aliphatischer Alkohol mit 2 bis 10 Kohlenstoffatomen, bevorzugt 3 bis 9 Kohlenstoffatomen ist. 2. Ceramic suspension according to claim 1, characterized in that the solvent (a) is an organic solvent, preferably a branched or linear, monohydric or polyhydric, preferably mono- or dihydric, aliphatic alcohol having 2 to 10 carbon atoms, preferably 3 to 9 carbon atoms is.
3. Keramische Suspension nach Anspruch 1 oder 2, dadurch gekennzeichnet, dass das Dispergiermittel (b) ausgewählt ist aus der Gruppe, bestehend aus organischen Verbindungen die eine polare funktionelle Gruppe aufweisen, vorzugsweise amphiphilen Homo- oder Copolymeren, die mindestens eine polare funktionelle Gruppe aufweisen. 3. Ceramic suspension according to claim 1 or 2, characterized in that the dispersant (b) is selected from the group consisting of organic compounds which have a polar functional group, preferably amphiphilic homo- or copolymers which have at least one polar functional group ,
4. Keramische Suspension nach einem der vorstehenden Ansprüche, dadurch gekennzeichnet, dass das nicht funktionalisierte Keramikpulver (c) ausgewählt ist aus der Gruppe der Oxid- und Nichtoxidkeramiken, vorzugsweise aus der Gruppe, bestehend aus Pulvern von Aluminiumoxid (AI2O3), Zirkoniumoxid (ZrO2), Siliziumnitrid (Si3N4), Siliciumcarbid (SiC), Aluminiumnitrid (AIN), Glaskeramik (SiO2), Titandioxid (TiO2) und Hydroxylapatitsowie Mischungen aus Aluminiumoxid (AI2O3) und Zirkoniumoxid (ZrO2) und Mischungen der genannten Keramikpulver oder der genannten Mischungen mit anderen anorganischen Oxiden, beispielsweise mit für die jeweiligen Keramikpulver oder jeweiligen Mischungen bekannten Sinteradditiven. 4. Ceramic suspension according to one of the preceding claims, characterized in that the non-functionalized ceramic powder (c) is selected from the group of oxide and non-oxide ceramics, preferably from the group, consisting of powders of alumina (Al 2 O 3 ), zirconia (ZrO 2 ), silicon nitride (Si 3 N 4 ), silicon carbide (SiC), aluminum nitride (AIN), glass ceramic (SiO 2 ), titanium dioxide (TiO 2 ) and hydroxyapatite, and mixtures from aluminum oxide (Al 2 O 3 ) and zirconium oxide (ZrO 2 ) and mixtures of said ceramic powders or said mixtures with other inorganic oxides, for example with sintering additives known for the respective ceramic powders or respective mixtures.
5. Keramische Suspension nach einem der vorstehenden Ansprüche, dadurch gekennzeichnet, dass der monofunktionelle Binder (d) ausgewählt ist aus der Gruppe, bestehend aus (Meth)acrylaten und Acrylamiden. 5. Ceramic suspension according to one of the preceding claims, characterized in that the monofunctional binder (d) is selected from the group consisting of (meth) acrylates and acrylamides.
6. Keramische Suspension nach einem der vorstehenden Ansprüche, dadurch gekennzeichnet, dass der multifunktionelle Binder (Vernetzer) (e) ausgewählt ist aus der Gruppe, bestehend aus funktionellen (Meth)acrylaten. 6. Ceramic suspension according to one of the preceding claims, characterized in that the multifunctional binder (crosslinker) (e) is selected from the group consisting of functional (meth) acrylates.
7. Keramische Suspension nach einem der vorstehenden Ansprüche, dadurch gekennzeichnet, dass der Polymerisationsinitiator (f) ausgewählt ist aus der7. Ceramic suspension according to one of the preceding claims, characterized in that the polymerization initiator (f) is selected from the
Gruppe, bestehend aus (Bis)acylphosphinoxiden und Mischungen daraus, sowie Campherchinon/Amin-Mischungen. A group consisting of (bis) acylphosphine oxides and mixtures thereof, and camphorquinone / amine mixtures.
8. Verfahren zur Herstellung der keramischen Suspension nach Anspruch 1 , dadurch gekennzeichnet, dass die einzelnen Komponenten (a) bis (e) sukzessive in einen Mischungsbehälter gegeben und vermischt werden oder ein vorheriges Dispergieren des Keramikpulvers mit einem Dispergiermittel durchgeführt wird und das Keramikpulver nachfolgend mit den restlichen Komponenten in einem Mischungsbehälter vermischt wird. 8. A method for producing the ceramic suspension according to claim 1, characterized in that the individual components (a) to (e) are successively added to a mixing container and mixed or a previous dispersion of the ceramic powder is carried out with a dispersant and the ceramic powder below with the remaining components are mixed in a mixing tank.
9. Verwendung der keramischen Suspension nach Anspruch 1 für keramische stereolithographiebasierte additive Fertigungsverfahren (Keramik-SLA). 9. Use of the ceramic suspension according to claim 1 for ceramic stereolithography-based additive manufacturing processes (ceramic SLA).
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