Classifications

• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
  • C03C11/00—Multi-cellular glass ; Porous or hollow glass or glass particles
  • C03C11/005—Multi-cellular glass ; Porous or hollow glass or glass particles obtained by leaching after a phase separation step
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
  • B22F3/10—Sintering only
  • B22F3/11—Making porous workpieces or articles
• • 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
  • C04B35/01—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics
• • 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
  • C04B35/01—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics
  • C04B35/10—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on aluminium oxide
  • C04B35/101—Refractories from grain sized mixtures
• • 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
  • C04B35/01—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics
  • C04B35/46—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on titanium oxides or titanates
• • 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
  • C04B35/6269—Curing of mixtures
• • 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
  • C04B38/00—Porous mortars, concrete, artificial stone or ceramic ware; Preparation thereof
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F2998/00—Supplementary information concerning processes or compositions relating to powder metallurgy
  • B22F2998/10—Processes characterised by the sequence of their steps
• • 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
  • C04B2235/30—Constituents and secondary phases not being of a fibrous nature
  • C04B2235/32—Metal oxides, mixed metal oxides, or oxide-forming salts thereof, e.g. carbonates, nitrates, (oxy)hydroxides, chlorides
  • C04B2235/3217—Aluminum oxide or oxide forming salts thereof, e.g. bauxite, alpha-alumina
• • C—CHEMISTRY; METALLURGY
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  • 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
  • C04B2235/30—Constituents and secondary phases not being of a fibrous nature
  • C04B2235/32—Metal oxides, mixed metal oxides, or oxide-forming salts thereof, e.g. carbonates, nitrates, (oxy)hydroxides, chlorides
  • C04B2235/3231—Refractory metal oxides, their mixed metal oxides, or oxide-forming salts thereof
  • C04B2235/3232—Titanium oxides or titanates, e.g. rutile or anatase
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
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  • 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
  • C04B2235/30—Constituents and secondary phases not being of a fibrous nature
  • C04B2235/32—Metal oxides, mixed metal oxides, or oxide-forming salts thereof, e.g. carbonates, nitrates, (oxy)hydroxides, chlorides
  • C04B2235/327—Iron group oxides, their mixed metal oxides, or oxide-forming salts thereof
• • C—CHEMISTRY; METALLURGY
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  • C04B2235/00—Aspects relating to ceramic starting mixtures or sintered ceramic products
  • C04B2235/65—Aspects relating to heat treatments of ceramic bodies such as green ceramics or pre-sintered ceramics, e.g. burning, sintering or melting processes
  • C04B2235/656—Aspects relating to heat treatments of ceramic bodies such as green ceramics or pre-sintered ceramics, e.g. burning, sintering or melting processes characterised by specific heating conditions during heat treatment
  • C04B2235/6562—Heating rate
• • 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
  • C04B2235/65—Aspects relating to heat treatments of ceramic bodies such as green ceramics or pre-sintered ceramics, e.g. burning, sintering or melting processes
  • C04B2235/656—Aspects relating to heat treatments of ceramic bodies such as green ceramics or pre-sintered ceramics, e.g. burning, sintering or melting processes characterised by specific heating conditions during heat treatment
  • C04B2235/6565—Cooling rate
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
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  • C04B2235/00—Aspects relating to ceramic starting mixtures or sintered ceramic products
  • C04B2235/65—Aspects relating to heat treatments of ceramic bodies such as green ceramics or pre-sintered ceramics, e.g. burning, sintering or melting processes
  • C04B2235/656—Aspects relating to heat treatments of ceramic bodies such as green ceramics or pre-sintered ceramics, e.g. burning, sintering or melting processes characterised by specific heating conditions during heat treatment
  • C04B2235/6567—Treatment time

Definitions

• the present invention relates to specific curable compositions; its uses; processes for manufacturing shaped cellular articles, cellular (micro) spheres and non-cellular (micro) spheres; to specific novel shaped cellular articles.
• EP0251634 discloses a moulding process for manufac- turing shaped inorganic articles using a thermosetting resin, a sinterable ceramic powder and pore formers. The process is complemented by thermosetting of the used polymer followed by a sintering.
• the process disclosed in this document is considered disadvantageous as polymeri- zation may take place prior to the shaping step, thus requiring additional precautions when processing the starting materials. Compositions using thermal curing processes are not preferred when fast and controllable shaping is required. Further, shaping steps suitable and articles obtainable according to this document are limited.
• US2002/0022672 discloses inter alia a process for manufacturing crosslinked polymeric foams using nanopar- ticles capable for polymerization and polymerizable material; it further discloses cross-linked foams com- prising such nanoparticles and polymerizable material.
• the document does not disclose inorganic porous material.
• the use of diluents and liquid pore formers in this process is disadvantageous for multilayer processing since these may compromise the quality of interface between such layers.
• WO03/015963 discloses a process for manufacturing a porous material, corresponding starting materials and products obtainable.
• the starting material according to this document is a dry flowable powder mixture. It is apparent that a solid starting material is disadvantageous for a number of manufacturing processes such as extrusion processes. Further, the heat and pressure needed to shape the composition disclosed therein make its use disadvantageous for multilayer processing.
• WO02/08321 discloses a process for manufacturing foams containing functionalized metal oxides, corresponding starting materials and products obtainable.
• the starting material according to this document is a discontinuous or co-continuous phase comprising water as a pore former. It is apparent that the use of solvents and liquid pore formers is disadvantageous for multilayer processing as liquid phase compromises the interface between layers and liquid removal is difficult or time consuming. Further, the size of the liquid pore former is difficult to control and its shape may be deformed during extrusion processes. Finally, the starting materials disclosed require low concentration of particles, which requires large production equipment.
• Andersson et al J. of the European Ceramic Society 2008, 2815-2821 disclose a process for manufacturing macroporous ceramics using specific expandable solid pore formers in combination with thermic initiators and diluents. It is apparent that the use of diluents, such as water, are disadvantageous as its removal is difficult and time consuming. Such compositions are disadvantageous for multilayer processes. Further, the pore former size is highly dependent on the temperature used during the curing step.
• the invention relates ⁇ in a first aspect to a curable composition, suitable for the manufacture of shaped cellular articles, and its use;
• the articles obtainable according to the processes described herein may contain a structured surface and/or cross section, i.e. they are either structured or non-structured. Further, the articles obtainable according to the processes described herein may consist of one material (i.e. homogeneous through a cross - sectional profile) or more than one material (i.e. non-homogeneous through a cross - sectional profile) .
• the inventive processes as described herein thus produce
• Fig. 1 shows a general and schematic process scheme according to the invention to obtain shaped cellular articles .
• Fig. 2 schematically shows various approaches for shaping the inventive composition to obtain composites and cellular shaped articles.
• Fig. 3 shows in a general and schematic process scheme according to the invention to obtain shaped cellular coatings material, wherein (1) shows a substrate, (2) shows cured layers and (3) shows a cast uncured layer.
• Fig. 4 schematically shows a set up of a manufacturing device according to one embodiment of the invention, suitable for manufacturing articles in the form of cellular and non cellular microspheres.
• Fig. 5 shows a general and schematic process scheme according to a preferred embodiment of the invention to obtain shaped cellular articles.
• shaped cellular inorganic or carbonaceous article defines an article containing (i.e. comprising or consisting of) sintered, partially sintered or non- sintered particles selected from the group of inorganic particles and carbonaceous particles, and which is essentially free of a cured polymer (as defined below) .
• cellular refers to a foam-like structure of the article where the material is built out of either discrete (fully closed cell structure), interconnected open cell network (fully open cell structure) or intermediate cell structures. The cells are filled with ambient gas, air or gas left after heating steps.
• This porous cell (or pore) structure which in the present invention has cell (or pore) sizes typically in the 1-1000 micrometers range is distinguished from the porous network of the particles comprising the cell wall before sintering, which are typically 10-1000 nanometer.
• a preferred ratio of cell size to particle size is >5:1 but can be as large as 10000:1.
• the term "inorganic” is understood in its broadest sense. Thus, any material free of organic compounds, which is material containing C-C single or multiple bonds or C-H bonds, is considered “inorganic".
• inorganic refers to ceramics (including oxides, carbides, nitrides, borides, silicates, hydrides, hydroxides), glasses (including oxides, fluorides, calcogenides) metals and alloys, inorganic salts and minerals (including nitrates, carbonates, sulphates, phosphates) .
• ceramic, glass and metal particles are particularly preferred.
• Particularly preferred inorganic articles are ceramic articles. Said article may contain one single type of particles (i.e. one oxide, one salt, one metal, one alloy) or combinations of one or more of such parti- cles .
• carbonaceous refers to material essentially consisting of or consisting of Carbon, such as graphite, carbon nanotubes, nanorods and the like.
• shaped cellular composite defines a material obtainable or obtained by a process as disclosed herein, said material contains a cured polymer (as defined herein) and inorganic/carbonaceous particles (as defined herein) and exhibits a cellular structure (as defined herein) .
• shaped non-cellular article defines a material obtainable or obtained by a process as disclosed herein, said material does not contain polymer material (as defined herein) but inorganic/carbonaceous particles (as defined herein) and pore formers (particularly solid pore formers), which are stable or metastable during the heating (debinding) step and therefore does not exhibit a cellular structure (as defined herein) .
• shaped non-cellular composite defines a material obtainable or obtained by a process as disclosed herein, said material contains a cured polymer, inorganic/carbonaceous particles and pore formers (as defined herein) and does not exhibit a cellular structure (as defined herein) .
• Pore formers or alternatively “cell formers” defines any material capable of forming pores (or cells) in an article by a process as described herein.
• Pore formers may be liquid or solid.
• Liquid pore formers may be aqueous or non-aqueous, preferably non-aqueous.
• Solid pore formers may be of inorganic material or organic material including particles of the core-shell type, preferably of organic material. The shape and crystalline phase of the particle is not limiting. Particles can be fibrous, sheet like, irregular, spherical.
• the shape and volume (or phase) of the pore formers as defined herein is unchanged or substantially unchanged during the shaping step b) and curing step c) .
• a continuous liquid pore former phase is regarded as an emulsification medium.
• emulsification media are suitable for manufacturing shaped cellular articles (particularly cellular microspheres) as defined herein.
• shape step is used in its broadest sense and includes all steps providing a shape to a composition as disclosed herein, including extrusion, moulding, deposition, printing, coating, casting and the like.
• extrusion process is known in the field; it defines a process to create composites of a fixed cross-sectional profile. This process is conventionally performed by pushing or drawing an appropriate material through a die of the desired cross section, optionally followed by one or more finishing steps.
• co- extrusion is known in the field; it refers to the process of simultaneously combining a, first fluid and one or more additional fluids in one extrusion unit.
• the cross section of the stream may vary depending of appli- cation.
• the additional fluid may be any suitable fluid and may comprise curable monomers, oligomers and/or polymers, dispersions of inorganic particles in these mixtures or inert fluids.
• a sheathing fluid in the context of this invention, is not considered an "additional fluid", thus the mere use of a sheathing fluid in a process according to this invention is not considered a "co-extrusion".
• coating process is known in the field; it defines a process to provide a coating on a substrate. Such coating may consist of one or more layers of the same or different material (coating / multilayer process) . Typical examples include spin-coating, knife- or blade- coating, spread coating and the like.
• emulsifi- cation is known in the field (e.g. oil in water emul- sion) ; it defines a process to produce (micro-) spherical droplets ( (micro-) "spheres”) by applying energy to a mixture containing non-miscible liquids; the dispersion and pore-former in the present invention. At relatively high ratio of pore former phase to dispersion phase, a discrete phase of (micro) spheres may form.
• heterogeneous / homogeneous define the compositions of the composite / article produced along a cross-section of the material. If only one type of material is present, such composite / article is termed homogeneous, otherwise heterogeneous.
• Heterogeneous composites / articles may be "core/shell” type or “lay- ered” and are preferably obtainable by co-extrusion or mulit-layerd coating.
• unstructured refers to either homogeneous or heterogeneous composite / article produced in a process without structuring dies/fluids or lithographic structuring where the whole of the composite (both cross section and length) is cured during the curing step.
• structured defines the modified cross sectional shape of the composite / article produced relative to an unstructured composite / article.
• a modification of the cross section using structuring fluids is considered (hydrodynamic) structuring while a modification of the cross section using a complex die is considered (mechanical) structuring.
• a modification of the cross section using a complex die which is aided with structuring fluids is considered a combined mechanic - hydrodynamic structuring.
• the non-curable structuring fluids are fugitive after curing whereas the curable fluids are fugitive during de-binding.
• (lithographic) struc- turing can also be done using a focused (laser) beam or alternatively with a flood exposure radiation source eguipped with a mask and a shutter.
• Sections of the curable extruded streams can be therefore selectively cured, producing modified cross sections.
• Structured articles are preferably above 10 micrometers in their larger dimension, particularly above 100 micrometers.
• the sectioning can be done along the direction of flow, producing thin cured sections (e.g. as a result of a shutter opening and closing or a beam with periodic motion) .
• an unstructured / structured article / composite may still be “cellular” as defined herein.
• the terra “dispersion” is known in the field; it particularly refers to i) a system in which finely divided particles, which are approximately 1 nanometer to 0.1 micrometer in size, are dispersed within a continuous medium in a manner that prevents them from being filtered easily or settled rapidly ("nanoparticulate dispersion”); ii) a system in which finely divided particles, which are approximately 1 nanometer to 1 micrometer in size, are dispersed within a continuous medium (“colloidal disper- sion”) ; to a system in which particles, which are larger than about 1 micrometer in size, are distributed in a continuous medium which filtered easily but settle slowly (“suspension”).
• dispersions are suitable for the present invention
• the term "dispersion” is used to cover all types. Preferred are, however, dispersions of particles in the size range 1 nanometer - 10 micrometers; more preferably 10 nanometers - 1 micrometer.
• sheath defines a stream of non curable fluid encompassing the extruded stream during the radiation curing step.
• the sheathing fluid has limited miscibility with the dispersion.
• the primary intent of the sheath is prevention of the sticking of the cured composite to the wall of the curing vessel and sustaining of a continuous flow.
• the sheaths flow and viscosity provide also hydrodynamic means to modify the size of dispersion cross section but not intentionally the shape of the cross section before curing. If the sheath is present in the exit die of the dispersion, the sheath moves relative to the die and is referred to as "dynamic sheath". Given a radiation transparent die material, the dynamic sheath enables the curing step to be performed in the die.
• the sheath In the case where the uncured extrudate is injected through the exit die into a large reservoir of liquid the sheath is referred to as "pseu- dostatic sheath". This process generally avoids the use of dynamic sheathing fluid and can be adapted for mass production purposes.
• the curing step is done within the pseudostatic sheath reservoir. This requires radiation lamps providing flood exposure situated around the reservoir as well as UV transparent reservoir materials and sheathing fluid. Further, the sheathing fluid may also be selected from the groups of wetting and non- wetting fluids with respect to the composition.
• extrusion die used in co-extrusion processes is known in the field. It normally consists of a manifold combining different streams into one composite stream.
• extrusion or when using relatively high viscosity dispersions
• holes in the extruded material are produced by extrusion around mechanical elements (mandrels) present in the die and arranged parallel to the flow direction. The structure of the elements is then inversely replicated in the extrudate.
• the mechanical elements described above consist of tubes delivering (hydrodynamic) structuring fluids.
• the location where the mechanical elements end in an extrusion die, or where the last dispersion or additional fluids (such as structuring fluid (s)) exit the mechanical element in co-extrusion dies, is defined as the location where structuring is complete ("end of exit die"); although the size of the outer conduit may not change. Beyond this point the additional fluids and the dispersion maintain the shape of the cross section of the composite stream defined by the mechanical elements (i.e., exit die) and enable thereafter curing in either dynamic or pseudo-static sheathing fluids.
• room temperature denotes a temperature range between 10-70 0 C, preferably between 15- 40 0 C; room temperature is 25°C +/-5°C.
• the invention in more general terms, in a first aspect, relates to a composition
• a composition comprising (i) one or more inorganic or carbonaceous particles, (ii) one or more monomers, oligomers and/or polymers curable by electromagnetic radiation or electron beams, (iii) one or more pore formers, (iv) optionally one or more initiators, (v) optionally one or more surfactants, (vi) optionally one or more diluents.
• the average size of component (iii) : size of component (i) is at least 3 : 1, preferably 5 : 1.
• the content of component (i) is 20 - 70 vol-%, preferably >40 vol-%, based on the total amount excluding pore former, i.e. (i)/((i) + (ii) + (iv) + (v) + (vi)) is 20 - 70 vol-%, preferably >40 vol-%.
• the content of component (ii) is at least 30 - 80 vol-% preferably ⁇ 60 vol-% based on the total amount excluding pore former, i.e. (ii)/((i) + (ii) + (iv) + (v) + (vi)) is at least 30 - 80 vol-% preferably ⁇ 60 vol-%.
• compositions consist of a continuous or non-continuous "dispersion phase” and a "distinct phase” containing the pore former.
• the term ,,dispersion phase denotes a composition as described herein without pore formers; the ,,distinct phase", consisting of the pore former, does not include diluents.
• compositions are suitable for conventional shaping and heating steps and thus for the manufacture of cellular shaped articles.
• size ratio of particles pore formers; amount of particles; amount of monomers
• the compositions provided are suitable for a wide range of shaping steps, without the limitations of the prior art. It is believed that this is particularly due to low viscosity and controlled hardening properties of the present composition.
• the present invention also relates to the use of a composition as defined herein for manufacturing a shaped cellular article.
• the manufacture of the inventive compositions may take place according to known procedures; generally speaking by combining the components as defined herein, which are commercially available or obtainable according to known processes.
• the present invention also relates to a process for manufacturing a composition as described herein comprising the steps of combining components (i) to (vi) as defined herein; preferably by combining components (i) , (ii), (iv) - (vi) (if present) first to obtain a dispersion and than adding component (iii) to obtain the inventive composition.
• the obtained composition may have an appearance of a dispersion / suspension, a foam-type structure, an emulsion.
• Component (i) In general, it is believed that the critical parameters of the process described herein are primarily related to dispersion properties, rather than properties of the particle material.
• the choice of inorganic particles and/or carbonaceous particles depends on specific application. In one embodiment, the particles do not, or essentially do not, take place in the curing step c) ("non-polymerisable") . In the context of the present invention, preceramic polymers are not considered a member of the group of component i) .
• inert, functional (e.g., optical, magnetic, electric, ferroelectric, catalytic) particles can be used.
• the particle material to be used as the inorganic constituent may be selected from a wide range of materials.
• any inorganic particle may be used.
• the term metal is used in its broadest sense, including main group metals, transition metals, rare earth metals and metalloids.
• aluminium, stainless steel, Al 2 O 3 , SiO 2 , Si 3 N 4 , SiC, hydroxyapa- thite, zirconia, PZT, ZnO, CeO 2 , TiO 2 are identified as materials for inorganic particles.
• Carbonaceous parti- cles include carbon particles and carbon nanotube materials. Mixtures of particles may also be used.
• Suitable particles may have a round, irregular, nanofiber / nanorod / nanobelt / nanotube type, core / shell type or an aggregated shape.
• the particle may consist of one or more materials.
• the amount of compound (i) in the curable dispersion may be between 20 - 70 vol-% of the curable composition without pore formers.
• the inorganic content refers to inorganic particles and inorganic radiation curable monomers/oligomers or polymers but not to inorganic pore formers .
• the size of compound (i) may vary in a broad range, and may be adapted according to the needs of the final article to be produced. Suitable are particles having an average particle diameter in the range of 1 nm - 10 micrometers, preferably 10 - 1000 nm, particularly preferably 20 - 500 nm. Colloidal particles are preferred for the current application where wall thickness of the cells approaches 1 micrometer.
• Component (ii) The type of compound selected from the group consisting of curable monomer, oligomer and/or polymer to be used is less critical. Basically, any curable material may be used, including mono- and higher functional monomers and oligomers. Commercially available
• stereolitography resins are suitable.
• said monomers, oligomers and / or polymers may be selected from the group consisting of acrylates and derivatives thereof, (such as methaycrylates and acrylic esters) and co-polymers containing such acrylates.
• Epoxies, vinyl ethers, vinyl monomers are also suitable.
• Such curable monomers / polymers may be used pure, diluted in organic solvents or as water based systems. By way of example, mixtures of uv-vis curable mono and multifunctional acrylates may be used.
• the resulting thermoset / thermoplast character is dependent on the choice of oligomers (e.g. urethane acrylates, epoxy acrylates) .
• Monomers / oligomers / polymers having large content of oxygen are preferred for cases where the de- binding step (described later) is done without oxygen. It is believed that this measure prevents excessive carbonization during this step.
• monomers / oligomers / polymers having advantageous magnetic, electric, ferro- magnetic, optical properties may be used.
• component (ii) is selected from the group consisting of one or more monomers, curable by electromagnetic radiation or electron beams,
• component (ii) is se- lected from the group consisting of acrylates and (meth) acrylates.
• the pore former i.e. (ii)/((i) + (ii) + (iv) + (v) + (vi)
• Component (iii) In principle, any known material functioning as a pore former during the manufacturing process may be used. Such pore forming materials are known to the skilled person. Thus, pore formers may be organic, inorganic or composite solid particles of varying shapes and aspect ratios. Fluids such as liquids and/or gases can also be used as pore formers. The pore formers form a distinct discrete or continuous phase in the composition defined herein.
• Pore former require mechanical energy to be supplied to produce a compositions in the form of a mixed disper- sion (solid pore former) ; in the form of an emulsion/dispersion (liquid pore former) ; or in the form of a wet foam/dispersion (gas pore former) .
• the fluids should not mix or modify the properties of the original dispersion substantially.
• the size of the pore formers may vary in a broad range and depend on the size of component (i) and the aimed porosity of the final article. As defined above, the average size of component (iii) : size of component (i) is at least 3 : 1, preferably 5 : 1. The size is defined on a volume basis. As a maximum size of the pore formers, 1000 micrometers was found advantageous, preferably 1-500 micrometers. These values particularly apply for discrete or co-continuous pore former phase.
• the shape and volume (or phase) of the pore formers is unchanged, or essentially unchanged during the shaping and curing steps as defined herein.
• the present invention relates to a composition, wherein a high amount of liquid pore formers is used, preferably 50-95 vol% of the total composition.
• the liquid pore former is equivalent to the emulsification medium where the composition (dispersion with or without pore formers) forms discrete (micro) spheres upon emulsification.
• the (micro) sphere themselves may contain another pore former. These provide intermedi- ate precursors for cellular or non-cellular inorganic (micro) spheres .
• Pore formers (iii) may be selected from the group consisting of solid pore formers, liquid pore formers and gaseous pore formers; particularly solid pore formers and liquid, non-aqueous pore formers.
• component (iii) consists of solid organic or inorganic, preferably organic, particles.
• the invention relates to a composition, wherein the concentration of component (iii) is at least 5 vol%.
• solid pore formers result in article dimensions close to net shape and relatively good control over size and volume of cells in the cellular inorganic article. It was further found that fluid pore formers (liquid or gaseous) may advantageously be deformed during axial processing (e.g. extrusion) . The use of solid pore formers in a composition without diluents is found to be advantageous for multilayer articles and processing.
• the pore former determines the cell wall and porosity of the inorganic cellular article produced.
• initiator The type of initiator to be used is less critical. In the scope of the present invention only initiators responsive to electromagnetic radiation are considered; although thermally responsive initiators are also suitable. Suitable initiators are compatible to component (ii) and are responsive to electromagnetic radiation or electron beams used in the curing step; preferred are initiators responsive to UV radiation ( "UV initiators") and/or initiators responsive to VIS radia- tion (“VIS initiators”) and/or initiators responsive to X-Ray radiation (“X-Ray initiators”) and/or initiators responsive to electron beam radiation (“electron beam initiators”) . By way of example, LTM, TPO, organic sulphur, or totally organic photoinitiator may be used, either as single initiator or as a mixture thereof. Preferably, an effective amount of initiator is present in the inventive composition or added prior to the shaping step.
• electron beam radiation is also considered electromagnetic radiation. Such radiation is also suitable and is hereafter grouped under same radiation category.
• Component (v) The type of surfactant to be used (if any) is less critical. Basically, any surfactant compatible with the other components which provides adequate dispersion is suitable. Preferred are surfactants that provide high coverage of the particle.
• anionic, cationic, nonionic, polyeletrolyte surfactants may be used.
• anionic or cationic comb-polyelectrolytes are used.
• Reactive surfactants i.e. those that can participate in the cross linking reactions during curing
• Emulsifica- tion as defined herein, may use similar or different types of surfactants. Block hydrophilic/hydrophobic copolymers are preferred for emulsification.
• Component (vi) The type of diluent to be used (if any) is less critical. Basically, any diluent compatible with the other components may be used. Diluents may be used to adjust viscosity and / or reactivty. It was also found that water-free diluents are often advantageous; in a further embodiment, the invention thus relates to a composition as described herein comprising a water-free diluent as component (vi) .
• the invention also relates to a composition as described herein, wherein component (vi) is not present (which is a "composition where no diluent is present") .
• component (vi) is not present
• component (component vi) which use solid pore formers only (component iii)
• component iiii are solidi ⁇ fied during curing, as no liquid or gas phases exist in the sample after curing.
• Such compositions are found particularly suitable for the manufacture of multilayer articles.
• Additional components e.g. an- tifoamers
• Such components may be beneficial, e.g. to facilitate manufacturing or may be required as part of the cellular article to be made.
• Kit of parts The invention relates to a composition as described herein as well as to kits suitable for manufacturing such composition. Particularly the invention relates to a kit, wherein one composition contains components i), ii), optionally iv) and optionally v) and vi) and the second composition contains component iii) and optionally iv) , v) and vi) .
• Kit parts containing the photoinitiator, component iv) are stored in a manner such that they are shielded from relevant electromagnetic radiation.
• component iv) may be stored separately and added to the kit or one of its parts just before use to avoid premature curing.
• the inventive composition is a liquid composition free of diluent (i.e. a suspension) .
• Said suspension consisting of particles (i), solid pore formers (iii) and initiators (iv) which are suspended in liquid curable monomer, oligomer and/or polymer (ii) .
• Preferable are acrylates and/or methacry- lates as component (ii) .
• said suspensions suitably have a viscosity below 100 Pas , typically in the range of 0.05 to 10 Pas.
• the invention in a second aspect, relates to a process for manufacturing shaped cellular articles.
• Such process comprises the steps of a) providing a composition as defined herein, then b) subjecting said composition to a shaping step; then c) subjecting the obtained material to a curing step which uses electromagnetic radiation; then d) optionally subjecting the obtained material to a purification step, then e) optionally subjecting the obtained material to an assembly step; then f) subjecting the obtained material to a heating step ("de-binding") wherein the polymer and pore formers are removed; then g) optionally subjecting the obtained material to a leaching step wherein inorganic pore formers are removed; then h) optionally subjecting the obtained material to a heating step wherein the particles are partially or fully sin- tered (“sintering”), then i) optionally subjecting the obtained material to a finishing step.
• This process provides a shaped cellular article containing inorganic or carbonaceous particles without (or essentially without) polymeric material and is also illustrated in Fig. 1. It is important to note that in the heating step (h) , the particles may be fully sintered but the cells are not.
• the process according to the second aspect of the invention benefits from the relatively low viscosity of the starting material, its stability during hardening (curing) and good interface quality for new layers; it provides a very versatile process for manufacturing a wide variety of cellular articles, including articles which may have complex structures / microstructures and / or may be of large or small dimensions.
• the composition is sufficient fluid such that known ceramic or rapid-prototyping/ rapid- manufacturing shaping techniques can be employed. These include, but are not limited to, coating, casting, moulding, extrusion, mixing / emulsification, printing / deposition.
• the solidification of the composition described above takes place shortly after shaping upon exposure of the above composition to radiation.
• the radiation preferably in the form of UV-vis radiation causes a rapid increase in viscosity due to initiation of polymerization and/or cross-linking reactions in the above composition. Portions of the shaped object can be shielded from the radiation so that selective curing of selected parts of the shaped object occurs.
• Products after this step may be in the form of fibers, tapes, tubes, single and multilayered coatings and monoliths, films, (micro) spheres etc.
• the inventive process provides a shaped cellular article of inorganic and / or carbonaceous material.
• the produced article is of inorganic material if component (iii) consists of inorganic particles; is of carbo- naceous material if component (iii) is carbonaceous particles and is of a mixed composition, if component (iii) consists of a mixture of inorganic and carbonaceous particles .
• Step a) Compositions, suitable for the inventive process are described herein. Suitable compositions may be stored in a reservoir (tank) and fed to the shaping unit by use of conventional means, e.g. extrusion feeding devices, pumps or by means of gravity. Standard de- airing, filtering and mixing procedures can be employed to ensure the quality.
• Viscosites for suitable compositions may vary in a broad range.
• compositions show a viscosity below 100 Pa*s, particular preferably below 10 Pa*s at shear rates and temperatures used for shaping. Temperature and shear rate can be used as variables for viscosity modification.
• compositions described herein are homogeneous and essentially stable (i.e. particles do not sediment) over time or can be easily homogenized by low energy mixing.
• the compositions are advantageously stored and use at or around room temperature. Short homogenizing step may be employed before use, especially when large pore formers are used (>200 micrometers) .
• Step b) (Shaping) :
• the invention is not limited to a specific shaping step. Basically any shaping step which is applicable to the inventive composition and which allows curing afterwards is applicable. This step is believed to be predominantly determined by the viscosity of the composition and not the particle material.
• step b) may be selected from the group consisting of extrusion processes, coating processes, printing processes, deposition processes, casting processes, moulding processes, mixing processes and emulsifi- cation processes.
• Extrusion processes include conventional extrusion and co-extrusion
• coating processes include conventional coating and multilayer coating. This is further illustrated in Fig. 2.
• compositions including pore form- ers
• the viscosity of compositions (including pore form- ers) during the shaping step may vary in a broad range.
• compositions show viscosities below 100 Pa*s, particular preferably below 10 Pa*s (at shear rates >100 s "1 and 25°C) .
• the shaping step is done by extrusion.
• Conventional extrusion / co- extrusion utilizes the dependence of viscosity on temperature and/or shear rate (e.g., dispersions in polymer melts) to obtain a sufficiently low viscosity for shaping and suffciently high viscosity for the extruded body to prevent unwanted deformation.
• the range for a specific starting material depends on the temperatures and pressures used, but cannot be set independently.
• One of the advantages of the present invention lies in the efficient decoupling of (micro-) forming and setting viscosities.
• the composites are microstructured at relatively low viscosities but can be cured in several seconds to rigid bodies.
• step b) referred to above is advantageously an extrusion or co-extrusion step .
• inventive extrusion processes are considered particular useful for manufacturing small diameter fibres (unstructured or microstructured) having also large open cross sectional area and/or thin wall (e.g., thin wall tubes) . These are easier to produce by the inventive process compared to known extrusion, due to use of starting material of lower viscosity. Further, the quality of heterogeneous composites benefit from improved quality of interface between layers resulting from the use of lower viscosity dispersions. The relatively low viscosity enables also combining of the co-extruded streams at dimensions similar to or close to the final cured dimensions. In known extrusion processes, the die is constructed to yield desired cross section of the article to be produced.
• shaped articles e.g. tubes
• structuring fluids in addition to structured die
• litho- graphical possibilities such as with focused beam (e.g. a laser beam) or a mask/shutter, selective time varying and/or curing of selected areas of the cross section of the extruded stream are possible.
• This enables for example a) partial curing of composite cross section close to the surface, b) forming thin sections in the flow direction having full or partial cured cross section, c) forming a continuous homogeneous/heterogeneous fibre or tape by only lithographical means.
• Extrusion processes according to this invention may be performed with or without sheathing fluids (as defined below) and / or as extrusion/co-extrusion processes (as defined below)
• a sheathing fluid optionally aids the inventive process.
• the invention relates thus in one embodiment to such extrusion processes, wherein step b) is aided by a sheathing fluid ("dynamic sheathing"), or wherein step c) is aided by a sheathing fluid (“pseudostatic sheathing"), or wherein steps b) and c) are aided by sheathing fluid(s), or wherein neither step b) nor step c) are aided by a sheathing fluid.
• Suitable sheathing fluids are transparent or essentially transparent with regards to the radiation used during curing; particularly, such fluids are UV transparent.
• Sheathing fluids may also contain additives such as salts and surfactants.
• the present invention relates in one embodiment to a process as described herein, wherein step b) is aided by a dynamic sheathing fluid passing the die along with said dispersion.
• the sheathing fluid passes the die along with said composition.
• a dynamic sheathing fluid having a viscosity in the range of 1/100 to 10 fold the viscosi ' ty of said dispersion was found to be suitable. The viscosities are defined at the particular conditions of shear rate and temperature during extrusion.
• the present invention relates in a further embodiment to a process as described herein, wherein step c) is aided by a pseudo-static sheathing fluid.
• the die may be arranged before or within a reser- voir of such sheathing fluid.
• a pseudo-static sheathing fluid having a viscosity above 0.3 mPas was found to be suitable, however the viscosity may not be limiting.
• step b) is aided by a dynamic sheathing as described herein and step c) is aided by a pseudo-static sheathing fluid as described herein.
• the present invention relates in a further embodiment to a process as described herein, wherein no sheath- ing fluid is used to aid the process.
• This process is advantageous for starting materials that have rheological properties between those used for conventional extrusion and those of the present invention that are advantageously produced using sheaths.
• the extruded material (with or without a dynamic sheath) may be extruded using known extrusion processes (e.g. directly to air) .
• the invention relates to a manufacturing process as described herein wherein said composition is complemented by one or more addi- tional fluids, such process is referred to as "co- extrusion process".
• Said additional fluid (s) may be independently selected from the following groups: a) one or more second composition (s) ; b) one or more curable structuring fluid(s); c) one or more non curable structuring fluid(s) .
• the concept of co-extrusion shall be explained in further detail below, whereby any extrusion process as described herein consisting of additional fluid (s) (besides "composition” and "sheathing fluid”) is considered a co-extrusion.
• the first compositions as defined herein may be complemented by one or more second composition (s) ("group a") .
• Such second composition will pass the die along with said first composition.
• two or more composition having different properties are fed to the die.
• This offers a method for manufacturing heterogeneous (e.g. "multilayered") shaped cellular articles.
• the particles of said first and said second composition differ from each other in at least one parameter.
• said second composition may contain particles of different material and / or different particle size.
• the components i) to v) may be selected according to the definitions given herein.
• such second composition comprises i) one or more organic and/or inorganic particles, preferably inorganic particles; ii) one or more curable monomers, oligomers and/or polymers, iii) optionally one or more pore formers, iv) optionally one or more initiators, v) optionally one or more surfactants, vi) optionally one or more diluents.
• said second composition (s) are selected from the same group of inert or functional particles of component i) .
• said first composition may be complemented by one or more curable structuring fluids ("group b") .
• curable structuring fluids will pass the die along with said first dispersion. Materials suitable for such curable fluids basically correspond with those of said first composition, with the exception that particles are absent.
• suitable curable struc ⁇ turing fluids comprise i) one or more curable monomers, oligomers and/or polymers; ii) optionally one or more initiators; iii) optionally one or more pore formers, iv) optionally one or more surfactants; v) optionally one or more diluents.
• the cured structuring fluid is part of the structure of a shaped composite but is replicated in the inorganic article as holes after the de-binding step. By this embodiment, it is possible to obtain heterogeneous and homogeneous shaped cellular articles.
• the invention relates to a process as described herein, wherein the fluid of group b) contains or essentially consists of monomers, oligomers and/or polymers of acrylates or meth-acrylates .
• said first composition may be complemented by one or more non-curable structur- ing fluids ("group c") .
• group c non-curable structur- ing fluids
• Such non-curable structuring fluids will pass the die along with said first dispersion.
• Materials suitable for such curable fluids basically correspond with those of said sheathing fluid.
• suitable non-curable structuring fluids comprise i) one or more diluents and ii) optionally one or more non- curable oligomers and/or polymers.
• the invention relates to a process as described herein, wherein the fluid of group c) has a viscosity in the range of 1/500 to 10 fold the viscosity of said first dispersion.
• all fluids passing the die are adjusted to a laminar flow regime. This measure avoids flow instabilities and excessive mixing.
• extrusion step bl is advantageously done at or around room temperature.
• Step b2) (Coating / Mulitlayer processes) :
• the shaping step is accomplished by a coating process.
• the composite body is made out of one or more layers of similar or different curable compositions. Rapid prototyping or rapid manufacturing techniques are considered suitable. This is especially advantageous for UV-vis curable compositions.
• the method is demonstrated in Fig. 3. Many different bodies can be prepared when several different composi- tions are used. Those compositions belong to the additional fluids groups a) and b) described in step bl) above. These fluids are treated in b2 ) as compositions only (without structuring functions) . For example, gradient materials when concentration, size, type, shape of pore formers is changed gradually for each subsequent layer.
• the inorganic material can also be changed in different manners for each layer. Further, standard coating and casting methods of a substrate, such as spin coating, knife or blade-coating, spread coating, screen printing and the like are applicable. It is also understood that the substrate may be removed after the curing step or at the end of the manufacturing process; such removal would be considered as a "finishing step”. Further, such removal may be accomplished mechanically, thermally and/or chemically. In this case the term "mould" is used to distinguish from a permanent / functional substrate.
• the invention relates to a proc- ess for manufacturing shaped cellular articles (c.f. Fig. 3) comprising the steps of a) providing a substrate and a composition as described herein; then b) coating said substrate with a first layer thereof; c) then subjecting at least a portion of the layer to a radiation initiated polymerization step (curing) ; d) then optionally removing non-reacted composition; then b) coating said cured layer with a further layer of similar or different composition; then c) subjecting at least a portion of said further layer to a radiation initiated polymerization step; then d) optionally, removing non-reacted composition; then optionally repeating steps b) to d) until the desired article is obtained; then optionally subjecting the obtained material to further finishing steps.
• coating and curing steps of each layer is done at or around room tempera ⁇ ture. It was found that the inventive compositions are stable at room temperature. Further, the inventive compositions are low-viscous and homogeneous and may therefore rapidly spread to thin layers and immediately after rapidly cured (e.g. by UV radiation) . In conclusion, the advantageous properties of the inventive compositions result in an improved and rapid multilayer process .
• coating and curing steps are advantageously carried out at room temperature and at ambient pressure.
• the need for cycling temperatures or pressures between steps i.e. heat/cool or pressurize/depressurize the samples between process steps.
• the advantageous properties of the inventive compositions result in a further improved and rapid multilayer process.
• compositions according to this invention which have only solid pore formers and no diluents, are cured to 100% solids.
• the drying steps for each layer eliminated and in addition thereto - an ideal interface for the next layer is provided.
• the advanta- geous properties of the inventive compositions result in a further improved and rapid multilayer process.
• Step b3) (Emulsification process) :
• the shaping step is done by an emulsification process.
• Known emulsification processes such as high- shear mixing or ultrasonication, may be employed.
• An emulsification step is used in all processes involving liquid pore formers, in order to reach a stable or metastable emulsion, often with an addition of special surfactants.
• the size of the pore former is defined with sufficient stability for the subsequent shaping/curing processes.
• emulsification is not considered a "shaping" process for discret or co-continous liquid pore former phases. This can be regarded as merely mixing the composition defined herein and defining the pore former size; similar to mixing and homogenization procedures done with solid pore formers .
• the liquid pore former phase is continuous and the dispersion phase forms discrete droplets.
• the liquid pore former is equivalent to the emulsification medium.
• Such emulsification medium is also suitable for manufacturing of (micro) sphere .
• Emulsification is therefore considered a shaping process for (micro) sphere production.
• the thus obtained (micro) sphere emulsion can be cured in a batch process (e.g. in the mixer/emulsifier) or advantagesly the curing (step (c) ) is aided by an extrusion process.
• FIG. 4 A preferred manufacturing device for the production of (micro) spheres is shown in Fig. 4.
• the (micro) sphere emulsion shaped in the emulsifier is fed by an extrusion unit to a curing unit wherein the (micro) spheres are cured.
• the emulsion, now containing solid (micro) spheres is fed to a purification unit wherein the spheres are separated from the pore formers and optionaly washed and dried before further processing.
• the (micro) spheres themselves can contain another type of pore former, for example, solid pore formers, rendering them cellular microspheres after heating steps (f, optionaly h) and if solid pore formers are used a leaching step (g) .
• step b3) is done at or around room temperature.
• Step c) (Curing) :
• the curing of the initially formed composite may be performed according to standard processes, e.g. known from “rapid prototyping processes". This step is predominantly dependent on the materials refractive indices, radiation (e.g., UV) absorption and on particle size. This only limits the thickness of a shaped composite available according to the inventive process, but the process is expected to work for all materials below such thickness. Appropriate curing conditions depend on the monomers, oligomers / polymers and initiators used in the preceding step as well as particle size, concentration and material used.
• the curing step is performed by a focused (laser) beam; or by a flood exposure unit equipped with a mask and optionally a shutter.
• This equipment enables to selectively cure sections of the composite and offers an additional method for manufacturing structured shaped composites / articles.
• the selective curing can be applied to sections of the cross section and/or sectioning in the direction of flow. The later produces discrete elements rather than fibres or tapes.
• Using a beam or a radiation source/mask to selectively pattern radiation curable materials is a well established technology used for structuring / etching surfaces of articles; suitable processes and equipment are known from stereolithography or micro- stereolithography .
• This embodiment is particularly suitable in combination with the dynamic sheathing fluid as described herein or in combination with the coating as described herein.
• the curing step consists of a radiation step using radiation in the UV and / or VIS spectrum, particularly in the UV spectrum.
• the curing time is in the order of 1 - 20 seconds for extrusion processes and 1-300 seconds for casting/coating processes.
• the curing step is carried out at or around room temperature. In an advantageous embodiment, the curing step is done below 2 bar, preferably at or around atmospheric pressure .
• Step d) (Purification) : Depending on the intended use of the shaped composite initially obtained and of the starting materials used, one or more further purification steps may follow the curing step. Such steps may be employed to remove unwanted starting materials, sheath fluids, diluents or other reaction aids, or to further modify the surface of the shaped composite. For coating/casting processes, unreacted material after litho- graphical structuring can advantageously be removed by suction (Vacuum) with or without the use of solvents.
• the purification comprises one or more washing steps using a solvent, a mixture of solvents or solvents with surfactants and/or one or more drying steps.
• acetone For example acetone, alcohols, hydrocarbons or water for organic pore formers or (meth) acrylate based systems; water or alcohol for an aqueous system.
• Systems containing diluents may require drying steps even if washing is not required.
• Step e) (Assembly) : Depending on the intended use of the shaped composite obtained and of the starting materials used, one or more further assembly (finishing) steps may follow the previously described steps. These steps include but not limited to coating, cutting, weaving, assembling into other devices, pressing or shaping, all of which are known per se .
• Step f and h) (Heating) :
• the heating step according to this invention is designed to remove all (or essentially all) organic material from the shaped composite obtained in the previous step; to effect pore forming and to effect a sintering of component i) .
• the product of this step is a shaped cellular article, unless heat stable pore formers are used.
• Such heating steps are known per se and may be performed in a one - step or multi step process.
• the invention relates to a process as described herein, wherein said step f) com- prises a first heating step wherein organic pore formers (iii) and polymer material (ii) are removed (“de- binding") along with unstable inorganic pore formers, and a second heating step wherein the particles (i) are partly of fully sintered (“sintering”) .
• a leaching step to remove inorganic pore formers stable or meta-stable during de-binding can advantageously be used after the first heating step.
• This step is designated (g) and is used only when stable inorganic pore formers are used.
• the sintering step is optional step (h) .
• Step f) (De-binding) : To obtain shaped cellular articles, the polymer/inorganic composites are de-binded. Organic pore formers are removed in the process along with the radiation generated organic polymer. Removal of organic pore formers (and gas pore formers) results in a reticulated or cellular inorganic materials.
• the de-binding comprises heating the composite material. Temperatures, heating times and atmospheres required depend on the structure of the shaped composite, the type and amount of organic material present in said composite.
• heating rate and temperatures are preferably adjusted to avoid undesired sintering and/or destruction of the shape and/or undesirable reaction of the parti- cles. Suitable parameters may be identified by routine experiments. Typically, heating temperatures are in the range of 200-800 0 C, preferred in the range of 400 - 700 0 C.
• An oxygen containing atmosphere is preferred for ma- terials where oxidation is not critical or for products of the de-binding step which belong to the group of metal (or mixed metal) oxides or hydroxides. Generally, air is the preferred atmosphere.
• An inert or reducing atmosphere is preferred, if products may oxidize during the de- binding treatment, such as metals, carbides, nitrides. It is also possible to change atmospheres during de-binding.
• Step g) (leaching) Inorganic pore formers which are not removed during the heating (de-binding) step can be removed by leaching with reactive gases or liquids which remove the pore former selectively, without significantly removing the inorganic/carbonaceous particles making up the cell walls.
• reactive gases or liquids which remove the pore former selectively, without significantly removing the inorganic/carbonaceous particles making up the cell walls.
• calcium oxide pore former can be removed with nitric acid solution at room tempera- ture. This treatment does not attack aluminum oxide.
• This step may optionally include washing procedures and drying before sintering.
• Step h) (Sintering) Sintering refers in the context of this invention to partial or full closure of pores between the inorganic/carbonaceous particles making up the walls of the cellular material.
• the sintering conditions are selected such that the cells are left in the sintered material while the cell walls partially or fully densify. This is due to the fact that the cell dimension is larger (preferably >5x) than the average distance between the inorganic particles (or average pore diameter) .
• Partial sintering is designed to strengthen the cellular material while retaining significant specific surface area. Full sintering reflects the attainment of a cell wall with density near or at the maximum theoretical density for the particular material. Such sintering steps are known per se. Temperatures and heating times required depend, inter alia, on the structure of the shaped composite, the particle material and porosity. Temperatures should be selected to achieve sintering and to avoid / reduce destruction of the shape. Sintering routines (temperature, time, atmospheres) are highly material dependent but are known to the person skilled in the art.
• Step i) (Finishing): Any finishing step known in the field may be applied to the shaped cellular article obtained by the inventive process. This includes, by way of example, cutting, coating, assembling into other devices, pressing or shaping.
• the invention in a third aspect, relates to shaped cellular articles.
• the compositions as described herein may be used to produce shaped cellular articles; such articles are either known (i.e. available by different processes using different starting materials) or novel, where they form part of the present invention.
• the invention relates to a shaped cellular article obtainable by or obtained by a process for manufacturing as described herein.
• the invention relates to a shaped inorganic cellular article essentially consisting of carbon.
• shaped cel- lular articles with porosity >30% are preferred. This may be advantageously achieved by adjusting the amount of pore former in the composition.
• the present invention re- lates to new shaped cellular articles as described herein in the form of a fibre, tube, tape or section thereof; in the form of a coating or multilayerd article or in the form of spheres / microspheres.
• These articles may be, depending on its manufacturing, be homogeneous or hetero- geneous and (micro-) structured or unstructured.
• the present invention relates to new shaped cellular articles as described herein fulfilling one or more, preferably all, of the following characteristics: a) porosity between 10-95%, preferably between 30-90%; b) cell size between 0.5-1000 micrometers, preferably between 1-500 micrometers; c) ratio of cell size to size of passage between cells larger than 3, preferably larger than 5.
• the invention relates to the use of the shaped composites / articles obtained or obtainable by a process as described herein.
• the uses are those that benefit from the special and potential advantages of the present invention such as flexibility in multilayer fabrication, structuring and sectioning, mass production of relatively small diameter fibres and thin wall objects, mass production of (micro) spheres, flexibility in material combinations, small particle size of feedstock .
• a manufacturing device comprising a emulsification unit followed by a extrusion unit, followed by a curing unit, followed by a purification unit.
• the (micro) sphere emulsion shaped in the emulsifier is fed by an extrusion unit to a curing unit wherein the (micro) spheres are cured.
• the emulsion, now containing solid (micro) spheres is fed to a purification unit wherein the spheres are separated from the emulsification medium and optionaly washed and dried before further processing.
• the (micro) spheres themselves can contain another type of pore former, for example, solid pore formers, rendering them cellular microspheres after heating steps (f, optionaly h) and if solid pore formers are used a leaching step (g) .
• the units may be run in parallel, e.g. two extrusion units followed by one or more curing unit. Further, certain elements of a unit may be present as either a single element or in manifold
• the units of the device are followed by each other as defined below. This means that the material prepared in one unit is transported to the next unit as defined herein. In one embodiment, the units are in fluid communication, meaning that manufactured material is directly transported to the following unit.
• the manufacturing device may be adapted to continu- ous or batch wise production; as known to persons in the field.
• extrusion and curing unit are adapted to a continuous process.
• This embodiment provides low investment costs and high flexibility of the process.
• all units are adapted to a continuous process.
• This embodiment provides low manufacturing costs in large scale production.
• ancillary units e.g. for de-airing, mixing, filtering, pumping / transporting, collection, storage, measuring, controlling are not explicitly shown. Such units are known to the person skilled in the art.
• Emulsification unit This unit provides an emulsion of a composition as described herein. Such units are known in the field. In this unit the composition and the amount and type of applied energy determines the size distribution of the (micro) sphere emulsion obtained.
• Extrusion unit Extruders are known in the field.
• the extrusion unit for (micro) sphere production uses compositions where the dispersion phase in non-continuous and therefore differs from the extrusion employed to make fibres, tubes or tapes which uses compositions having continuous disper ⁇ sion phases. Sheaths and/or structuring fluids are therefore inapplicable for the sphere extrusion process .
• the sphere emulsion is extruded through a die essen ⁇ tially transparent to electromagnetic radiation wherein the (micro) spheres are cured by exposure to radiation.
• the extruder is designed to allow homoge- neous emulsion flow and the die is narrow and long enough to allow sufficient curing depth and curing time, respec ⁇ tively.
• Curing unit According to the present invention, curing is initiated by electromagnetic radiation.
• at least one source of radiation such as a lamp emitting UV and/or visible light, is present in this unit.
• the unit is adapted to ensure the extrudate (which is pro ⁇ vided within the exit die) is exposed to the radiation, to ensure full curing.
• the curing unit consists of UV lamps providing flood exposure. These are conveniently positioned around the exit die of the extruder. The exit die material and the pore former fluid are substantially transparent to the radiation.
• Purification units are known in the field and may be selected according to the requirements of the process and/or article obtained.
• a preferred purification step is a sieving step followed by a washing or rinsing step; suitable units are thus equipped with a stagnant or vibrating sieve, washing bath and/or a sprayer and/or dryer. This unit removes the pore formers, washes and dries the spheres before further processing.
• separation by centrifugation or other means known to the person skilled in the art can be employed.
• Example 1 monolithic alumina cellular articles , 70-80% A UV curable dispersion consisting of 27 vol% alumina powder (Taimicron TM-DAR, Taimei chemicals co., Ltd, Japan) and 73 vol% monomer mixture was provided.
• the alumina powder had an average particle size of 150 nanometers and density of 3.96 g/cm 3 .
• the alumina powder was pre-stabilized with 4.5% (particle basis) of comb- polyelectrolyte MelPers4343 surfactants (BASF, Germany) .
• the resin composition was 93.3% 2-HEA (2-Hydroxyethyl Acrylate, BASF, Germany) and 6.7% PEG200DA (Polyethylene- glycol 200 diacrylate, Rahn, Switzerland) .
• the viscosity of the dispersion was 0.034 Pa • s (23°C, 100 1/s) .
• the pore formers were spherical PE particles (Flow beads, CL- 2080; Sumitomo seika, Japan) with size range of 6-25 micrometers and average size of 12 micrometers and density of 0.918 g/cm 3 , according to the manufacturer.
• the pore former in an amount equivalent to 83% porosity of the finished inorganic cellular material (based on alumina particles only) was added to the dispersion to form a composition suitable for shaping of cellular alumina.
• the calculation of equivalent porosity assumes the volume of the PE pore former particles is replaced by air after the polymer phase is removed by de-binding and full sintering.
• the equivalent amount in this case is 7 g PE pore formers per 6.4 g alumina particles.
• a pourable paste was obtained.
• 3% (monomer basis) of the liquid photoinitiator Genocure LTM (containing ⁇ 25% 2, 4, 6-Trimethylbenzoylphenyl-phosphineoxide, Rahn, Switzerland) was added homogeneously to the paste.
• the paste was cast in several 1.7 cm ID plastic moulds transparent to UV radiation from all sides, to a level of 2-3 mm.
• the moulds were inserted into a UV chamber (UV cube 100, Dr. Honle AG, Germany, Fe bulb, 100W) and cured for 2-3 minutes from top and bottom.
• the cured disks were demoulded and heated from room temperature to 650 0 C in 1Oh and debinded at 650 0 C in air for 2h. This was followed by heating from 650 0 C to 1500 0 C in 6h and sintering at 1500 0 C for 2h. Cooling to room temperature was done over 15h.
• the disks remained integral and strong. SEM of broken surface showed well distributed cells with sizes of 3-30 micrometers (most with diameter of -10 micrometer) , corresponding closely to the pore former size and shape. The thickness of the cell wall was 0.2-1 micrometers.
• Hg- porosimetry measurements showed an average pore size of 2 micrometers (corresponding approximately to the passage between pores seen in SEM) .
• the density of the cellular article was 0.833 g/cm 3 ; corresponding to a porosity of 79%. 13.5% of the porosity was inaccessible to Hg, assuming the cell wall had a theoretical density of 4 g/cm 3 .
• the maximal temperature in the UV cube measured after prolonged operation was 70 0 C (close to the UV bulb) .
• the sample temperature during the curing step may have therefore risen to about 35-40 0 C.
• this temperature increase is by no means essential for the curing of the sample. In the absence of thermal initiator no curing takes place even at much higher temperatures, in the vicinity of the evaporation temperature of the monomers.
• TM-DAR pre-stabilized alumina particles consisting of 40 vol% alumina powder and 60 vol% monomer mixture
• the resin composition was 93.3% 4-HBA (2- Hydroxybutyl Acrylate, BASF, Germany) and 6.7% PEG200DA (Polyethyleneglycol 200 diacrylate, Rahn, Switzerland) .
• a paste with 70% equivalent porosity was made using monosized 40 micrometer PMMA pore former with a density of 1.2 g/cm 3 (Spheromeres, Microbeads, Norway) .
• Example 2 monolithic alumina cellular article, layer by layer, 80%
• the paste with composition of example 1 was used (83% equivalent porosity) .
• the paste was cast to 1 layer of ⁇ 1 mm thickness in two square 2x2 cm 2 UV transparent plastic moulds having a depth of -0.9 cm and cured in the UV setup of example 1 for 2-3 min.
• a second layer of ⁇ 1 mm was cast on top of the first, planarized and then cured in a similar fashion. Additional layers were processed similarly until a thickness of -0.9 cm was obtained.
• the de-binding and sintering steps were similar to those described in Example 1.
• the cubes remained integral and strong and had sintered dimensions of 1.54x1.54 cm 2 and thickness of 0.7 cm. Preliminary crash tests showed the strength of the material was comparable with literature values for 75-80% porous materials.
• Example 3 Thin layer of cellular alumina, 70% porosity
• An UV curable dispersion consisting of 40 vol% alumina powder (Taimicron TM-DAR, Taimei chemicals co., Ltd, Japan) and 60 vol% monomer mixture was provided.
• the alumina powder has an average particle size of 150 nm and a density of 3.96 g/cm3. This powder was pre-stabilized with 4.5% (particle basis) of MelPers4343 surfactants (BASF, Germany) .
• the resin composition was 93.3% 4-HBA (4-Hydroxybutyl acrylate, BASF, Germany) and 6.7%
• PEG200DA Polyethyleneglycol 200 diacrylate, Rahn,
• the viscosity of the dispersion was 0.3 Pas
• the pore formers used were spherical monosized 10 micrometers PMMA microbeads (Spheromeres, Microbeads, Norway) with a density of 1.2 g/cm 3 .
• An amount of pore formers equivalent to 70% porosity of the finished cellular sample was added to the dispersion to get a composition suitable for shaping of cellular materials.
• the equivalent amount in this case is 5 g PMMA pore formers per 7.1 g alumina particles.
• a pourable paste, with a viscosity of 5 Pas (at 23°C, 100 s "1 ) was obtained.
• 5% (monomer basis) of the photoinitiator Genocure LTM was added homogenously to the paste.
• the paste was cast to a thin film between two Polypropylene (PP) foils. 200 micrometer spacers in ⁇ serted between the two foils determined the thickness of the film.
• the cast film was inserted into a UV chamber (described in example 1) and cured for 1 minute.
• the PP foil provides a good casting substrate since it is substantially transparent to UV radiation and the cured films can easily be separated from/de-moulded from it.
• the cured thin layer having a thickness of 200 micrometers and an area of -40 cm 2 was placed between 2 alumina plates with a distance of 400 micrometers created by spacers, and heated from room temperature to 65O 0 C at 0.9 °C/min and debinded at 650 0 C for 2 h. This was followed by heating from 650°C up to 1500 0 C at 1.4 °C/min and sintering at 1500 0 C for 2 h. Cooling to room temperature was done with a rate of 1.5°C/min. After sintering the film retained integrity and had a thickness of 160-170 micrometers .
• the paste composition used in this example is fully solidified during curing since it contains only solid pore formers (which do not change phase during shaping and/or curing) and no diluents.
• the cured sample is composed of 100% solids.
• Example 4 Gradient porosity structure, layer by layer, 0-70% porosity
• alumina and pore former content varied as follows: 49 vol% alumina dispersion without pore formers (monosized 10 micrometers PMMA microbeads) , 46 vol% alumina dispersion with 30% equiva- lent porosity, 43 vol% alumina dispersion with 52% equivalent porosity and 40 vol% alumina dispersion with 70% equivalent porosity.
• the alumina solid content was chosen to provide compositions with identical, or almost identical, total shrinkage of the green layers during debinding and sintering. 5% (monomer basis) LTM was added to each paste and mixed thoroughly.
• the paste without pore former was cast on a Teflon plate, covered with a PP-foil and planarized (by lightly pressing on the foil) to create a planar layer of about 400 micrometer thick- ness (similar casting procedure described in example 3) .
• This layer was cured for 2 - 3 minutes in the UV chamber of example 1.
• On this cured layer the next layer of paste with the next higher porosity was cast and cured in a similar fashion. This process was repeated for the other two pastes to create a multilayer sample having 4 layers with increasing pore former content and overall thickness of 2 nun and an area of -13 cm 2 . Debinding and sintering steps were similar to those explained in example 3. However no spacers or loads were used.
• sample sintering After sintering the sample remained integral and strong but was slightly bent. It had a thickness of 1.6 mm. Such bending and minor imperfections can be eliminated by further adjust ⁇ ment of layer composition and smaller porosity increments between layers.
• the spacers (example 3) or load used may also be employed during debinding and sintering to obtain unbent samples.
• SEM of the sample cross section shows four -400 micrometer layers with gradually (but stepwise) varying porosity from 0-70%. An average cell size of 7 - 9 micrometers is obtained in all cellular layers. Except minor imperfections, the interface between the layers appears intact.
• Example 5 Gradient cell size structure, layer by layer, 70% porosity, cell size 6-40 micrometers
• the dispersion of example 3 was used as basis for four paste compositions suitable for the shaping of cellular materials with gradient structures.
• the paste compositions had similar equivalent porosity but distinctly different pore former size.
• the four pore formers used were spherical monosized PMMA microbeads (Sphero- meres, Microbeads, Norway) with a size of either 6, 10, 20 or 40 micrometers and a density of 1.2 g/cm 3 .
• Four pastes with an amount of pore formers equivalent to 70% porosity of the finished cellular sample were produced and 5% (monomer basis) LTM was added and mixed thoroughly.
• the paste with 40 micrometer pore former was cast on a Teflon plate and covered with a PP-foil and pla- narized to create a planar layer of -400 micrometer thickness. This layer was cured for 2 - 3 minutes in the UV chamber. On this cured layer the next layer of paste with the next smaller pore formers was cast and cured in a similar fashion. This process was repeated for the other two pastes to create a multilayer sample with 4 layers having decreasing pore former size and overall thickness of 1.9 mm and an area of -12 cm 2 . Debinding and sintering steps were similar to those explained in example 3. However no spacers or loads were used. The sample remained integral and strong and had a thickness of about 1.5 mm. SEM of broken sample shows four layers with gradually (but stepwise) increase in cell size. Each layer has well distributed cells with size corresponding closely to the initial pore former size. Except minor imperfections the interface between the layers appears intact.
• Example 6 alumina cellular fibre 70% with pseu- dostatic sheath process or without sheath
• a UV curable dispersion of 43 vol% alumina (Taim- icron TM-DAR, Taimei chemicals co., Ltd, Japan) and 57 vol% resin was provided.
• the alumina powder has an average particle size of 150 nanometers and density of 3.96 g/cm 3 .
• the powder was pre-stabilized with 7 wt% comb-polyelectrolyte surfactant (particle basis) obtained from BASF, Germany.
• the polyelectrolyte has a polyme- thacrylate backbone with 1 PEO side chain for every 6 methacrylate groups.
• the PEO side-chain length is 1100 g/mol.
• the resin composition was 93.3% HEA (2-Hydroxyethyl Acrylate, BASF, Germany) and 6.7% Miram- mer 282 (Polyethyleneglycol 200 diacrylate, Rahn, Switzerland) .
• the viscosity of the dispersion was 0.21 Pa • s ' (23 0 C, 100 1/s) .
• the pore formers were spherical PE particles (Flow beads, CL-2080; Sumitomo seika, Japan) with size range of 6-25 micrometers, an average size of 12 micrometers and density of 0.918 g/cm 3 , according to the manufacturer.
• the pore former in an amount equivalent to 73% porosity (based on alumina particles only) were added to the dispersion.
• a 1 ml glass syringe containing the paste was equipped with a stainless steel tip having an ID of 500 micrometer. All UV transparent surfaces of the flow system which contained the dispersion were coated with aluminium foil to shield the dispersion from UV radiation and prevent curing of the dispersion before exiting the die.
• the dispersion was injected manually (i.e., under low pressure) in a continuous fashion into a glass beaker with a diameter of 10 cm filled with DI water to a level of -15 cm. The linear speed of the stream leaving the syringe tip was approximately 2 cm/s.
• a UV lamp (Fe bulb, 10OW, Dr.
• Example 7 - alumina cellular (micro) spheres , 0-80% porosity
• a UV curable dispersion of 31 vol% alumina and 69 vol% resin was provided.
• the alumina powder was pre- stabilized with 4.5% of MelPers4343 surfactants (BASF, Germany) .
• the resin composition was similar to that of example 1.
• the viscosity of the dispersion was 0.058 Pa • s (23°C, 100 1/s) .
• 3% LTM photoinitiator (resin basis) was added homogeneously to the dispersion.
• the dispersion was mixed vigorously with an equal volume of Oil(Mazzola) to form a composition capable of producing (micro) spheres consisting of a suspension of dispersion droplets.
• the suspension is cast in 17 mm diameter plastic moulds to a height of 1-2 mm and cured for 1-2 minutes in the UV curing setup of example 1.
• the sphere cake produced was de-binded and sintered as described in example 1.
• An integral and strong disk consisting of spheres was obtained.
• the individual sintered spheres show sizes between 50-400 micrometers, most spheres around 150 micrometers. Hg-porosimetry indicates the spheres are fully dense.
• the second approach is ideal to obtain individual spheres. After curing, the spheres were sieved and washed with IPA and water to remove the oil. Spheres containing an equivalent of 41% porosity pore former in the size range 50-1000 micrometers (most spheres around 500 micrometers) and 83% pore former in the size range 100-500 micrometers (most around 300 micrometers) were obtained.
• Example 8 monolithic alumina cellular article, oil pore former
• the dispersion of example 5 (a) was used (31 vol% alumina and 69 vol% resin) .
• the alumina powder was pre- stabilized with 4.5% of MelPers4343 surfactants (BASF, Germany) .
• the viscosity of the dispersion was 0.058 Pa-s (23°C, 100 1/s) .
• Oil(Mazzola) was added to the dispersion (39 wt% emulsion basis) to produce a composition with continuous dispersion phase, capable of producing cellular alumina. This is equivalent to 75% porosity (based on alumina particles only) .
• the oil contained 7% PEG-block- PE copolymer (Sigma Aldrich, Switzerland) as emulsion surfactant. 3% (monomer basis) of the photoinitiator Genocure LTM (containing ⁇ 25% 2, 4 , 6-Trimethylbenzoyl- phenyl-phosphineoxide, Rahn, Switzerland) was added homogeneously to the mixture. A relatively stable and pourable composition was obtained after vigorous mixing. The casting, curing, de- binding and sintering are similar to those described in Example 1. The piece remained integral and strong. SEM of broken surface showed well distributed spherical cells with size of 10-60 micrometers, dense wall with size of several micrometers.
• Example 9 monolithic silica cellular article, 40% porosity
• a UV curable dispersion containing 40 vol% silica powder (Aerosil ox50, Evonic Degussa, Germany) and 60 vol% resin was provided.
• the silica had an average particle size of 40 nanometers and density of 2.2 g/cm 3 .
• the resin composition was similar to that of example 1.
• the dispersion had a viscosity of 0.5 Pa • s (25°C, 100s "1 ) .
• 3% photoinitiator Genocure LTM (Rahn, Switzerland) was added homogeneously (monomer basis) .
• the pore formers were spherical PE particles (Flow beads, CL-2080; Sumi ⁇ tomo seika, Japan) with size range of 6-25 micrometers and average size of 12 micrometers and density of 0.918 g/cm 3 , according to the manufacturer.
• the pore formers in an amount equivalent to 40% porosity (based on silica particles only) were added to the dispersion to form a composition capable of producing cellular silica.
• the equivalent amount in this case is 1.7 g PE pore formers per 3 g silica particles.
• the samples were cast and cured as described in example 1. The samples were heated from room temperature to 500 0 C in 8.5 h de-binded at 500 0 C for 2 h.
• the sample was heated in 4 h and sintered at 1250 0 C for 2 h.
• the disk remained strong and integral.
• SEM of broken surface showed well distributed spherical cells with size of 3-20 micrometers (most with diameter about 10 micrometers) , corresponding closely to the pore former size and shape.
• the thickness of the cell wall is mostly between 1-5 micrometers, but distances between cells can be as large as 10 micrometers. Most cell walls appear intact.
• Hg-porosimetry indicates 35 % and average pore size (corresponding to passage between cells) of 0.4 micrometers.
• Example 10 monolithic hydroxyapatite cellular article, 60% porosity
• a UV curable dispersion containing 27 vol% hydroxya- patite powder (Sigma Aldrich, Switzerland) and 73 vol% resin was provided.
• the hydroxyapatite had an average particle size ⁇ 200 nanometer.
• the density of the powder is taken as 3.156 g/cm 3 .
• the resin composition was 93.3% 4-HBA (Hydroxybutyl acrylate, BASF, Germany), 6.7% Miramer 282 (Polyethyleneglycol 200 diacrylate, Rahn, Switzerland) .
• 3% photoinitiator Genocure LTM was added homogeneously (monomer basis) .
• the pore formers were spherical PE particles (Flow beads, CL- 2080; Sumitomo seika, Japan) with size range of 6-25 micrometers an average size of 12 micrometers and density of 0.918 g/cm 3 , according to the manufacturer.
• the pore formers in an amount equivalent to 63% porosity (based on hydroxyapatite particles only) were added to the dispersion to form a composition capable of producing cellular hydroxyapatite.
• the calculation of equivalent porosity assumes the volume of the PE pore former particles is replaced by air in the cellular material after the polymer phase is removed by de-binding and full sintering.
• the equivalent amount in this case is 3 g PE pore formers per 5.3 g hydroxyapatite particles.
• the samples were cast into 17 mm round plastic moulds and cured with the UV curing setup of example 1 for 2-3 minutes. The de- binding and sintering steps of example 7 were used. SEM of broken surface showed well distributed spherical cells with size of 3-20 micrometers (most with diameter about 8-10 micrometers), corresponding closely to the pore former size and shape. The thickness of the cell wall is around 1-3 micrometers. Most cell walls appear intact.
• the density of the cellular material is found by Hg porosimetry to be 1.24 g/cm 3 corresponding to a porosity of 61 % (of which 11.5% is closed) and an average pore diameter (corresponding to the passage between the cells) of 2.4 micrometers.
• Example 11 Monolithic La 0 . 6 Sr 0 ⁇ CoO 3 (LSC) , TiO 2 and Fe 2 O 3 cellular articles
• a UV curable dispersion consisting of 33 vol% LSC and 67 vol% monomer mixture was provided.
• the LSC powder had a density of 5.9 g/cm3.
• the aqueous dispersion was acidified to a pH of 4.8 with HCl and pre-stabilized with 10% (particle basis) of MelPers4343 surfactants (BASF, Germany) . After this procedure the particle size distribution trimodal with two main peaks of 67 nm and 1.6 micrometers.
• the resin of example 3 was used.
• the viscosity of the dispersion was 0.45 Pas (at 23°C, 100 s "1 ) .
• the pore formers of example 3 with an amount equivalent to 69-74% porosity of the finished cellular sample (based on LSC particles only) was added to the dispersion. 5-10% LTM (monomer basis) was added homogenously to the dispersion. The dispersion was cast between two PP-foils with a distance of 200 micrometer and inserted to the UV chamber and cured for 3 minutes. UV curing was possible but resulted in small curing depth (80-120 micrometer). It is apparent that these results can be significantly improved an appropriate selection of a UV-vis curing system.
• Examples 1-8 and 11 demonstrate that alumina and LSC nano and submicrometer powders stabilized with comb- polyelectrolyte surfactants are compatible with the monomer mixture and pore formers used.
• Cellular materials have been similarly prepared from compositions containing dispersions of 25 nm TiO 2 nanoparticles (Aeroxide, P25, Evonic Degussa, Germany) and 25 nm Fe 2 O 3 (Hematite) nanoparticles (NanoAmor, USA) stabilized with 10% and 15% Melpers4343, respectively.
• the monomer mixture and pore formers of example 3 were used.
• the solid loading of the TiO 2 and Fe 2 O 3 dispersions was 17 and 19 vol%, respectively.
• the equivalent porosity was 50 or 86% for TiO 2 and 50% for Fe 2 O 3 .
• TiO 2 pastes were cured by UV radiation (5% LTM per monomer mixture) and Fe 2 O 3 pastes thermally (1% AIBN, at 85°C for 30 minutes) . Both materials were debinded at 550 0 C for 2h. Fe 2 O 3 was partially sintered at 850 0 C for Ih. SEM of broken surface shows that also in these cases the cellular materials thus obtained exhibit good replication of the pore former shape and size.

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