Set of chemicals for producing a ceramic dispersion or a ceramic gel

Abstract

Provide a set of chemicals for the production of ceramic dispersions or ceramic gels. The present invention relates to a set of chemicals for the production of ceramic dispersions or ceramic gels, a manufacturing process for ceramic molded parts, and ceramic molded parts manufactured by this process.

Description

Technical Field

[0001] The present invention relates to a set of chemical substances for producing a ceramic dispersion or a ceramic gel, which is preferably suitable for the production of ceramic shaped parts such as ceramic veneers, or shaped bodies such as ceramic partial crowns, veneers, ceramic inlays, and onlays by a layer build-up process such as stereolithography. The present invention also relates to a method for producing a ceramic shaped part and a ceramic shaped part produced by this method.

Background Art

[0002] In a layer build-up process for producing a ceramic veneer or a shaped body, a ceramic gel or a ceramic dispersion containing a (curable) polymer material is applied to a substrate in layers and continuously dried, for example, by exposure to radiation or heat, either simultaneously or downstream. Thereby, a so-called ceramic "green body" is produced. Next, a debinding treatment is performed, that is, a polymeric binder is usually discharged at a high temperature, and a so-called "white body" is produced. During the debinding treatment, the binder is converted by heat and / or a thermochemical process, the repeating units of the polymer are at least partially changed, and at least partially decomposed into volatile components.

[0003] The white body is sintered in a sintering furnace during high-temperature firing. The finely dispersed ceramic powder is compressed and solidified under the influence of temperature, and the porous component shrinks and the strength increases.

[0004] However, the layer build-up process always has the drawback that defects such as cracks and bubbles occur during heating, especially in the debinding treatment step, rendering the member unusable. This effect can usually only be addressed by slowing down the heating process, that is, increasing the heat treatment time, but then the corresponding manufacturing process becomes uneconomical.

[0005] For example, Patent Document 1 discloses a curable composition for producing a three-dimensional body by stereolithography, which composition contains 40 to 70% by volume of ceramic or metal particles, 10 to 35% by weight of a monomer, 1 to 10% by weight of a photoinitiator, 1 to 10% by weight of a dispersant, and preferably a solvent, a plasticizer, and a coupling agent.

[0006] From Patent Document 2, a slurry for producing a ceramic molded part by a hot melt inkjet printing process is known, which contains ceramic particles and one or more waxes that are polymerizable by free radicals and can produce a green body that can be substantially debound without cracking. However, in a stereolithography process, the slurry needs to be stable in a liquid state for a long period of time, that is, in particular, it is necessary to prevent the particles dispersed in the slurry from precipitating prematurely, which particularly causes problems in terms of achieving the desired maximum volume fraction of ceramic particles in the slurry.

[0007] Patent Document 3 discloses a stereolithography-based process that at least partially overcomes the above-mentioned drawbacks. However, here too, a radical polymer precursor is used to generate a binder.

[0008] However, in such radical reactions, especially in the case of silicate-based ceramic gels, there is a drawback that free radicals may damage other components of the composition and may lead to discoloration. Furthermore, in radical reactions at high conversion rates, it has been observed that the reaction rate increases exponentially (Trommsdorff-Norrish effect). This effect is due to a decrease in the probability of chain termination by recombination of highly reactive chain ends, which is caused by an increase in the immobility of growing polymer chains. As a result, the rate of the exothermic reaction increases, the temperature rises, the decomposition of the radical initiator is accelerated, and the concentration of reactive molecules increases. At the same time, due to the increase in viscosity, it becomes more difficult to dissipate the heat of reaction (heat of polymerization). As a result, local overheating occurs, and when applied in multiple layers, cracks, explosions, and decomposition may occur in other components of the ceramic composition. Also, the mechanical properties and durability of ceramic molded parts obtained from known compositions are limited, and there is a particular problem that cracking and decomposition are likely to occur. Furthermore, the stability / storage properties of the ceramic composition are also limited.

Prior Art Documents

Patent Documents

[0009]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0010] Therefore, against this background, the object of the present invention is to provide a set of chemical substances that can overcome the above-mentioned drawbacks. The set of chemical substances according to the present invention is intended to enable a straightforward build-up process of silicate mineral-based ceramic gels or ceramic dispersions, from which high-quality ceramic shaped parts with little discoloration can be obtained.

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

[0012] This problem is solved, according to this invention, by a set of chemical substances for manufacturing ceramic gels. This set comprises the following components, namely A) preferably a powdery ceramic material, and B) a binder, the ceramic material comprises or consists of a silicate ceramic material, and the binder comprises or consists of a gelling agent. Preferably, it is a polymer, and the polymer has one or more repeating units, and one or more of the one or more repeating units have one or more chelating functional groups.

[0013] This set of chemical substances is suitable for the preparation of ceramic dispersions, in particular ceramic dispersions and / or ceramic gels. For this purpose, it is preferred to add a solvent such as water or alcohol and / or a dispersant to the set of chemical substances, or the set of chemical substances has a corresponding solvent and / or dispersant. Preferably, this ceramic dispersion is suitable for use in the processes of stereolithography, binder jetting or material jetting.

[0014] In colloid chemistry and process engineering, a dispersion is a heterogeneous mixture of two or more substances that hardly or do not dissolve in each other at all and do not chemically bond. One or more substances are finely dispersed as a so-called dispersed phase in another continuous substance called the so-called dispersion medium.

[0015] A "gel" is an example of a dispersion system consisting of two or more components. The gelling agent, which is a solid component, forms a sponge-like three-dimensional network with long molecules and / or highly branched molecules, and the holes are filled with a liquid (lyogel) or a gas (xerogel). The liquid component is thus fixed to the solid component. When the network is highly porous and filled with air as the gas, the gel is also called an aerogel.

[0016] As a matrix former, the gelling agent thickens the liquid phase and / or forms a rubbery gel. Therefore, it can also be used to thicken and / or stably support emulsions. It is classified into natural (e.g., agar), inorganic (e.g., bentonite), semi-synthetic (e.g., carboxymethyl cellulose), and synthetic gelling agents (e.g., polyvinyl alcohol). Semi-synthetic and synthetic gelling agents are particularly preferred in this invention due to their high performance.

[0017] According to this invention, "solvent and / or dispersant" means a substance that is liquid under standard conditions (temperature: 298.15 K = 25 °C, pressure: 1013.25 mbar = 1013.25 hPa) and in which at least some of the components of a set of chemical substances can be dissolved and / or dispersed.

[0018] According to the present invention, a "binder" is a substance or combination of substances that, particularly by retaining and stabilizing ceramic particles during heat treatment, produces a stable dispersion or gel and enables a uniform distribution. As an essential component, the binder according to the present invention includes or consists of a gelling agent such as a polymer containing a chelating functional group. The binder according to the invention also contributes to stabilizing the ceramic material in a finely dispersed state in a solvent and / or a dispersant, that is, when a solvent and / or a dispersant is used, it suppresses the sedimentation of the ceramic material and also makes it possible to completely prevent it.

[0019] In the context of the present invention, "polymer" shall mean a chemical substance composed of macromolecules. A "macromolecule" is a molecule composed of one or more identical or similar structural units, which is a constitutional repeating unit (IUPAC. Compendium of Chemical Terminology, 2nd ed. (the “Gold Book”), A.D. McNaught, A. Wilkinson, Blackwell Scientific Publications, Oxford (1997), S.J. Chalk. ISBN0-9678550-9-8). Such a macromolecule has 10 or more repeating units, preferably 15 or more repeating units. The molar mass is preferably 3,000 g / mol or more, more preferably 5,000 g / mol or more, still more preferably 7,000 g / mol or more, and most preferably 10,000 g / mol or more.

[0020] Polymers are usually produced by reacting monomers or oligomers having one or more constitutional repeating units through a polymerization reaction. An oligomer is a molecule formed from a plurality of monomers and thus structurally consists of a number of identical or similar structural units. When a molecule is produced from the reaction of 2 to 10 monomers, preferably 2 to 8 monomers, preferably 3 to 7 monomers, in the context of the invention, this is referred to as an oligomer.

[0021] The binder preferably contains 50% by weight or more, more preferably 70% by weight or more, still more preferably 80% by weight or more, yet more preferably 90% by weight or more, most preferably 95% by weight or more, or 100% by weight of a gelling agent, and the gelling agent is preferably in the form of a polymer having a chelating functional group.

[0022] Preferably, the ceramic material contains 50% by weight or more, more preferably 70% by weight or more, still more preferably 80% by weight or more, yet more preferably 90% by weight or more, most preferably 95% by weight or more of a silicate ceramic material.

[0023] The silicate ceramic material is an inorganic non-metallic material obtained from a silicate raw material, i.e., a compound having [SiO 4 4 -tetrahedra in its crystal structure. The SiO 2 content of the silicate ceramic material is preferably 20% by weight or more, more preferably 30% by weight or more. The term silicate ceramic material may include glass ceramics, but preferably does not include them. Preferably, the proportion of glass ceramics in the silicate ceramic material is less than 5% by weight, more preferably less than 2% by weight, still more preferably less than 1% by weight, yet more preferably less than 0.5% by weight, most preferably less than 0.1% by weight.

[0024] According to the present invention, the term "set of chemical substances" means a predetermined composition in which the individual chemical substances are in separate containers or are present as a composition in which some or all are mixed. Particularly preferably, the set of chemical substances is present as a composition, particularly a liquid, paste-like or solid composition.

[0025] ​The term "chelating functional group" refers to a functional group capable of forming a chelate. A chelate is a cyclic coordination compound having one or more central metal atoms or ions and a polydentate ligand, a so-called chelating ligand. A ligand is an ion or molecule that can bind, i.e., coordinate, to a central metal atom or ion via a coordination bond. The difference between a coordination bond and a classical covalent bond is that in a coordination bond, the ligand provides both of the bonding electrons, and thus the ligand becomes a "Lewis base". Polydentate in this context means that the ligand has two or more coordination sites for coordinating to a metal atom or ion. In other words, a chelating ligand must have two or more atomic groups that can act as electron donors.

[0026] In a preferred embodiment of the present invention, the chelating ligand has three or more, more preferably four or more, particularly preferably five or more, and most preferably six or more coordination sites.

[0027] The present inventors have confirmed that by using a gelling agent according to the present invention, such as a polymer having a chelating group, a silicate ceramic dispersion, or a silicate ceramic gel, it is possible to produce ceramic particles having a high stability of the ceramic particles, i.e., the ceramic particles having little or only very little tendency to separate. Further, this composition has a structure that is easy to process while at the same time having sufficient stability. This was previously impossible or only possible to a limited extent.

[0028] In particular, when using a polymer having a chelating group, although not bound by this theory, the inventors believe that the chelating group forms a polar interaction with the partially positively charged silicon atoms of the silicate ceramic, and as a result, stabilization can be achieved especially in the dispersion. A polymer material having one or more chelating functional groups thus acts as a binder. The corresponding polymer material also increases the viscosity of the gel or dispersion, resulting in a fluid and easily processable material, especially a sprayable material. This eliminates the need to use a radically polymerizable polymer precursor compound during production to ensure the processability of the corresponding ceramic gel.

[0029] Using the set of chemicals according to this invention, it is possible to produce ceramic gels or ceramic dispersions that are extremely delicate and can also build a fine particle structure. Furthermore, the peripheral shrinkage observed during the debinding process and the sintering process is small, that is, the volume change is not significant. The inventors believe that this is because the ceramic particles in the gel are uniformly dispersed. Furthermore, the debinding process is particularly efficient and rapid.

[0030] To achieve particularly good processability of the gel or dispersion, it is preferable to increase the viscosity. To achieve this, in a preferred embodiment of the present invention, when the gelling agent is a crosslinked polymer, more precisely, it may be advantageous when the polymer macromolecules of the set of chemicals are crosslinked.

[0031] Preferred gelling agents are selected from the group consisting of chitosan or chitosan derivatives, polysaccharides such as alginic acid, xanthan or alginates, polyuronic acids, gelatin, hyaluronic acid, polyvinyl alcohol, polyethylene glycol, acryloyldimethyltaurate ammonium, hydroxypropyl starch (HPS), hydroxypropyl distarch phosphate (HDP), polyquaternium, especially 3-methyl-1-vinylimidazolium methyl sulfate-N-vinylpyrrolidone copolymer or poly(2-methacryloxyethyltrimethylammonium chloride), bentonite, sorbitan monooleate, polyethylene glycol triether or polypropylene glycol triether, propylene glycol dicaprylate / dicaprate, silicate clay and / or layered silicate, such as sodium-magnesium silicate or aluminum-magnesium silicate, montmorillonite-type sodium-magnesium, or sodium-magnesium-fluorine-lithium layered silicate, polyacrylamide, silica (such as aerosil), sorbitan oleate decyl glucoside crosslinked polymer, styrene-maleic anhydride or ethylene-maleic anhydride copolymer and its derivatives, hydrophobized ethoxylate urethane, polyvinylpyrrolidone, amylopectin, cellulose or cellulose derivatives (such as cellulose acetobutyrate), polyacrylate or polymethacrylate and its esters, copolymers and / or salts, or mixtures and copolymers thereof. The gelling agent is preferably crosslinked, especially crosslinked by covalent bonds.

[0032] It is particularly preferred that the gelling agent is a hydrogel-forming polymer. A hydrogel is a gel composed of an insoluble polymer capable of binding water. The molecules forming the gel are bonded by chemical bonds such as covalent bonds, supramolecular bonds, ionic bonds, or physical bonds such as entanglement of polymer chains to form a network capable of binding a solvent such as water. Examples of polymers crosslinked by covalent bonds include thiolated polymers (thiomers) that crosslink polymer chains by forming disulfide bonds.

[0033] Superabsorbent polymers are a particularly preferred special form among gelling agents. A superabsorbent polymer (a "superabsorber") is preferably a crosslinked polymer that can absorb several times its own weight of polar solvents such as water. When a liquid is absorbed, the superabsorbent polymer swells and forms a hydrogel. The functions of superabsorbent polymers are described, for example, in Koltzenburg, S., Nuyken, O., Maskos, M. (2013). Polymers: Synthesis, properties and applications. Germany: Springer Berlin Heidelberg.

[0034] According to the present invention, the superabsorbent polymer is preferably a crosslinked copolymer having repeating units consisting of acrylic acid and / or sodium acrylate and / or acrylic acid esters.

[0035] According to the present invention, the superabsorbent polymer is preferably a crosslinked copolymer having repeating units consisting of methacrylic acid and / or sodium methacrylate and / or methacrylic acid esters.

[0036] Particularly preferred are crosslinked copolymers of acrylic acid and sodium acrylate, or crosslinked copolymers of acrylic acid and / or sodium acrylate and / or acrylamide, especially crosslinked copolymers of acrylic acid, sodium acrylate and acrylamide.

[0037] Particularly preferred are crosslinked copolymers of methacrylic acid and sodium methacrylate, or crosslinked copolymers of methacrylic acid and / or sodium methacrylate and / or methacrylamide, especially crosslinked copolymers of methacrylic acid, sodium methacrylate and methacrylamide. The corresponding copolymers are particularly preferably crosslinked with allyl ether of sucrose or allyl ether of pentaerythritol.

[0038] Carbomers, especially those crosslinked with polyalcohols, polyalkene ethers (e.g., polyalcohol allyl ethers and polyalkene ethers of saccharides), allyl ether sucrose, or allyl ether pentaerythritol are particularly preferred, as they have a wide range of applications and are easily available.

[0039] Polymers in which the chelating group contains one or more oxygen atoms have also been proven to be particularly preferred in use. The inventors believe that the stabilizing effect is particularly high, especially due to the remarkable Si - O interaction. The chelating group may be, for example, an acid group, a base, or an ester group contained in polyacrylic acid or polyacrylate. Polyvinylpyrrolidone or polyvinylphosphonate has also been proven to be particularly preferred. The macromolecules of the aforementioned polymers are particularly preferably crosslinked, and crosslinking by covalent bonds is preferred. In this case, the terms "bond" and "crosslink" are used synonymously and refer to the formation of a three - dimensional network by the bonding of a large number of macromolecules constituting the polymer. Crosslinking can be achieved directly during the formation of the macromolecule or by reaction with an existing polymer. As a result, swelling is observed in the polymer, which has a positive effect on the dispersion medium.

[0040] The set of chemical substances preferably contains less than 5% by weight, more preferably less than 2% by weight, even more preferably less than 1% by weight, even quite preferably less than 0.5% by weight, and most preferably less than 0.1% by weight of polymerizable polymer precursor compounds such as monomers or oligomers.

[0041] Particularly preferably, the weight ratio of the polymerizable polymer precursor compound to the polymer in the set of chemical substances is 1:10 or more, preferably 1:50 or more, and particularly preferably 1:100 or more.

[0042] By appropriately reducing the proportion of polymerizable compounds, side reactions and decomposition reactions can be avoided during gel production.

[0043] Preferably, the binder and / or gelling agent has a low ash residue, preferably 10 wt% or less, more preferably 5 wt% or less, still more preferably 1 wt% or less, quite preferably 0.5 wt% or less, and most preferably 0.2 wt% or less.

[0044] The ash residue, i.e., the residue remaining after the heat treatment of ashing, can be determined in particular by thermogravimetric analysis as described in DIN EN ISO 3451-1. The less the ash residue, the more the discoloration of the ceramic molded part is suppressed.

[0045] The set of chemicals according to the invention preferably further comprises a solvent and / or a dispersant. In this context, polar and / or protic solvents such as water and / or alcohols, in particular polyhydric alcohols such as ethylene glycol and monopropylene glycol, are particularly preferred. These are particularly suitable for keeping the components of the gel or dispersion obtained from the set of chemicals in a dispersed or dissolved state, thereby enabling the processing of the gel or dispersion.

[0046] In a preferred embodiment of the invention, the weight ratio of the solvent and / or dispersant in the weight of the set of chemicals not including the weight of the ceramic material is 5 wt% or more, preferably 10 wt% or more, more preferably 15 wt% or more, still more preferably 20 wt% or more, still quite preferably 30 wt% or more, and most preferably 40 wt% or more, but generally 70 wt% or less.

[0047] Preferably, the weight ratio of the solvent and / or dispersant in the weight of the set of chemicals not including the weight of the ceramic material is from 50 wt% to 99.9 wt%, more preferably from 70 wt% to 99 wt%, and most preferably from 90 wt% to 99 wt%.

[0048] In a preferred embodiment of the present invention, the weight ratio of the ceramic material in the weight of the chemical set is 70% by weight or less, preferably 50% by weight or less, more preferably 40% by weight or less, even more preferably 35% by weight or less, and most preferably 30% by weight or less, but preferably 20% by weight or more.

[0049] In a preferred embodiment of the present invention, the weight ratio of the ceramic material in the weight of the chemical set is in the range of 5-70% by weight, preferably 10-50% by weight, more preferably 15-40% by weight, and most preferably 20-35% by weight.

[0050] A correspondingly low percentage of ceramic material generally allows for the production of a gel that is more flowable and easier to handle.

[0051] Particularly preferably, the composition further comprises one or more bases, in particular Brönsted bases, i.e. compounds whose monomolar aqueous solution has a pH>7, preferably>8. The base ensures that the interaction between the ceramic particles and the polymeric material is improved. In particular in the case of chelating groups with acid functions, the base serves to capture protons, which further increases the complexation strength of the chelating groups. This effect can be particularly observed in polyacrylic acids or polyacrylates and polyvinylphosphonic acids or polyvinylphosphonates. The base is particularly preferably selected from the group consisting of alkali metal and alkaline earth metal hydroxides and alkali metal and alkaline earth metal carbonates. Particularly preferably, the base is selected from the group consisting of NaOH, KOH, Na 2 CO 3 , K 2 CO 3 , CaCO 3 , CaO and Ca(OH) 2 , NaHCO 3 or mixtures thereof.

[0052] The set of chemical substances preferably contains a base in an amount of 15% by weight or less, more preferably 10% by weight or less, still more preferably 5% by weight or less, even more preferably 1% by weight or less, and most preferably 0.5% by weight or less. The minimum content of the base is preferably 0.05% by weight or more, more preferably 0.1% by weight or more.

[0053] Preferably, the weight ratio of the base(s) in the weight of the set of chemical substances, excluding the weight of the ceramic material, is from 0.10% by weight to 0.99% by weight, more preferably from 0.20% by weight to 0.8% by weight, and most preferably from 0.3% by weight to 0.7% by weight.

[0054] In a preferred embodiment of the present invention, the set of chemical substances preferably contains a preservative, which is preferably biocidal, as an additional component. The preservative serves to extend the shelf life of the ceramic gel or ceramic dispersion, particularly by preventing the decomposition process. In particular, sulfur-containing preservatives such as isothiazolinones are preferably used as preservatives. Their bactericidal and fungicidal effects prevent the microbial decomposition of the components of the set of chemical substances. Particularly preferred are 5-chloro-2-methyl-4-isothiazolin-3-one, 2-methyl-4-isothiazolin-3-one, isothiazolin-3-one, methylisothiazolinone, benzisothiazolinone, octylisothiazolinone, dichlorooctylisothiazolinone, or mixtures thereof. Alternatively, formaldehyde releasers such as O-formaldehyde or N-formaldehyde are also suitable as preservatives. Particularly preferred are benzyl hemiformaldehyde, 1,6-dihydroxy-2,5-dioxanehexane, methylolurea, 7-ethylbicyclooxazolidine, methenamine, paraformaldehyde, tris(hydroxymethyl)nitromethane, or mixtures thereof.

[0055] The set of chemical substances preferably contains a preservative in an amount of 5% by weight or less, more preferably 2% by weight or less, still more preferably 1% by weight or less, even quite preferably 0.5% by weight or less, and most preferably 0.25% by weight or less. The minimum content of the preservative is preferably 0.05% by weight or more, more preferably 0.1% by weight or more.

[0056] To suppress the coloring of the ceramic gel or ceramic dispersion, the set of chemical substances preferably contains a transition metal compound, especially Er 2 O 3 、Fe 2 O 3 、Co 3 O 4 、MnO 2 、NiO 2 、Cr 2 O 3 、Pr 2 O 3 、Tb 2 O 3 、Bi 2 O 3 and may further contain a coloring component selected from oxides of these mixtures. However, alternatively or additionally, acetylacetonates or carboxylates of iron, cerium, praseodymium, nickel, terbium, lanthanum, tungsten, osmium, terbium and manganese can also be used.

[0057] The coloring component is preferably selected such that a tooth-colored ceramic molded part can be obtained after debinding treatment and sintering.

[0058] The coloring component can preferably also be incorporated into the ceramic material. The ceramic material can also contain other additives such as a fluidizing agent or a release agent.

[0059] The set of chemical substances preferably contains the above coloring component in an amount of less than 5% by weight, more preferably 2% by weight or less, still more preferably 1% by weight or less, even quite preferably 0.5% by weight or less, and most preferably 0.25% by weight or less. The minimum content of the above coloring component is preferably 0.05% by weight or more, more preferably 0.1% by weight or more.

[0060] In a preferred embodiment of the present invention, the weight ratio of the ceramic material in the weight of the set of chemical substances is 40% by weight or more, preferably 50% by weight or more, more preferably 55% by weight or more, still more preferably 60% by weight or more, and most preferably 65% by weight or more.

[0061] In a preferred embodiment of the present invention, the weight ratio of the ceramic material in the weight of the set of chemical substances is 95% by weight or less, preferably 90% by weight or less, more preferably 85% by weight or less, still more preferably 80% by weight or less, and most preferably 75% by weight or less.

[0062] In a preferred embodiment of the present invention, the weight ratio of the ceramic material in the weight of the set of chemical substances is in the range of 50 to 90% by weight, preferably 55 to 85% by weight, more preferably 60 to 80% by weight, and most preferably 65 to 75% by weight.

[0063] Generally, by appropriately increasing the proportion of the ceramic material, a very compact gel with less residual ash can be obtained.

[0064] Also, when the proportion of the ceramic material is relatively high, the possibility of mechanical damage occurring during the heat treatment of the ceramic gel or dispersion is significantly reduced, and a more homogeneous ceramic molded part can be obtained.

[0065] In a preferred embodiment of the present invention, the weight ratio of the gelling agent in the weight of the set of chemical substances is, for example, in the form of a polymer, 0.1% by weight or more, more preferably 0.2% by weight or more, still more preferably 0.5% by weight or more, still more preferably 1% by weight or more, still more preferably 1.5% by weight or more, still more preferably 1.5% by weight or more, still more preferably 2% by weight or more, and most preferably 2.5% by weight or more. Thereby, the ceramic material in the ceramic gel or ceramic dispersion is particularly significantly stabilized. However, the weight ratio of the polymer is preferably 3.5% by weight or 4% by weight or less, whereby the residual ash generated by the heat treatment of the set of chemical substances is minimized.

[0066] The weight ratio of the gelling agent in the weight of the set of chemical substances excluding the weight of the ceramic material is preferably from 0.10% by weight to 0.99% by weight, more preferably from 0.20% by weight to 0.8% by weight, and most preferably from 0.3% by weight to 0.7% by weight.

[0067] The weight ratio of the ceramic material to the weight of the other components of the set of chemical substances is preferably in the range of 1:1 to 5:1, more preferably 2:1 to 4:1, and most preferably 3:1 to 4:1. Also, the ratio of the ceramic powder to the binder is very preferably from 60:40 to 70:30.

[0068] The silicate ceramic is preferably selected from the group consisting of feldspar, leucite, lithium silicate, lithium disilicate, and lithium aluminosilicate ceramic. Feldspar ceramic is particularly preferred, especially in combination with polyacrylic acid and / or polyacrylate as a polymer. In this combination, a particularly remarkable stabilizing effect was observed.

[0069] Furthermore, the present invention also relates to a composition composed of a set of chemical substances or containing a set of chemical substances, particularly a gel or a dispersion. Preferably, the weight ratio of the set of chemical substances to the total weight of the composition is 10 to 70% by weight, preferably 15 to 70% by weight, more preferably 20 to 60% by weight, still more preferably 25 to 60% by weight, and most preferably 30 to 60% by weight.

[0070] The gel or dispersion is preferably prepared by mechanically mixing component B) (i.e., the binder) and any optionally included components (such as component C or component E) etc.) with a ceramic material (preferably in the form of a ceramic powder).

[0071] The present invention also relates to a method for manufacturing a ceramic molded part, which includes or consists of the following steps. That is a 1 ) mixing the components of the set of chemical substances defined above to obtain a gel or a dispersion; b) irradiating or heat-treating the gel or dispersion in a temperature range of 50°C to 150°C to obtain a green body; c) at least partially, preferably by heat-treating or irradiating the green body in a temperature range of 150°C to 350°C, preferably completely removing the binder to obtain a white body; d) sintering the white body to obtain a ceramic molded part, or, when steps b) and / or c) are optional, heat-treating the green body or the gel or the dispersion in a temperature range of 700°C to 1000°C. The process steps are preferably carried out at different times in the order from a 1 ) to d).

[0072] The above steps b) and c) are optional and can also be carried out without a time interval, that is, combined as one step. The ceramic molded part can also be manufactured by omitting the intermediate steps of manufacturing the green body or the white body. The binder is removed in step d). However, when these steps are carried out, particularly high product quality can be obtained.

[0073] The method for manufacturing a ceramic molded part according to the present invention preferably includes the following additional steps.

[0074] a 2 ) A step of applying a gel or dispersion in layers to the surface, preferably to a cop or mounting die made of metal or zirconium, preferably by spraying and / or a 3D printing process, particularly preferably by multi-jet modeling.

[0075] This step is preferably carried out between steps a 1 ) and b), particularly preferably carried out separately in time from these steps.

[0076] Preferably, steps a 2 ) and / or b) and / or c) and / or d) of the method according to the present invention are carried out by a rapid prototyping process, particularly a stereolithography process.

[0077] Furthermore, the present invention also relates to ceramic molded parts produced by the method according to the present invention, such as crowns, crown parts, veneers, ceramic inlays or onlays, bridge anchor crowns, bridge pontics, and their parts. In the above process, by using the set of chemicals according to the present invention, ceramic molded parts with particularly high homogeneity and a natural appearance can be obtained. Therefore, these exhibit favorable properties compared to known ceramic molded parts of the prior art. Preferably, in order to obtain a white body, the binder is removed by heat treatment of the green body in the temperature range of 150°C to 350°C, particularly by irradiation with infrared light. However, this removal is particularly rapid and homogeneous when using the gel or dispersion according to the present invention. In the above temperature range, the debinding treatment time can be 20 minutes or less, 15 minutes or less, and even 10 minutes or less.

[0078] In addition, the ceramic molded parts produced by the method according to the present invention are also characterized by high strength and attention to details. The flexural strength based on ISO6872 is preferably more than 50 MPa and particularly in the range of 100 - 500 MPa for molded bodies made of feldspar or glass-ceramics.

[0079] The present invention also relates to the use of a combination of a silicate ceramic and a gelling agent, particularly a polymer having one or more repeating units, wherein one or more of the repeating units preferably have at least chelating functional groups in a gel for producing ceramic molded parts for manufacturing ceramic molded parts for dental restorations such as inlays, onlays, veneers, crowns, bridges.

[0080] The present invention also relates to the use of a gelling agent as a binder in a gel or dispersion for producing a ceramic molded body, and the gel preferably contains or consists of a silicate ceramic.

[0081] Furthermore, the present invention also relates to the use of a polymer having one or more repeating units, one or more of which repeating units contains one or more chelating functional groups as a binder in a gel or dispersion for the production of ceramic shaped parts, and the gel preferably contains or consists of a silicate ceramic.

[0082] Examples Hereinafter, the present invention will be described with specific examples together with the corresponding photographs.

[0083] Example 1 of production Prepare a mixture of the following components in a Petri dish. 1) Deionized water (~70 wt%) 2) Carbomer (~17 wt%) 3) Sodium hydroxide (~3 wt%) 4) Monopropylene glycol (~7 wt%) 5) A mixture of 5-chloro-2-methyl-4-isothiazolin-3-one, 2-methyl-4-isothiazolin-3-one, and isothiazolin-3-one (remaining amount)

[0084] After obtaining a uniform paste, add feldspar or glass ceramic powder to this mixture. Add the ceramic powder in an amount 3 to 4 times the total mass of the mixture of components 1) to 5) so that a sprayable ceramic dispersion can be obtained after mechanical mixing. Transfer the mixture to a 10 ml Coltene syringe and apply it to the framework body in layers. Then, perform heat treatment at 150 °C to obtain a green body. Further perform heat treatment at 300 °C to obtain a white body, and then sinter at 950 °C.

[0085] Example 2 of production Prepare a mixture of the following components in a Petri dish. 1) Deionized water (~98.5 wt%) 2) Carbomer (~1.0 wt%) 3) Potassium hydroxide (~0.5 wt%)

[0086] After a uniform paste is obtained, feldspar or glass ceramic powder is added to this mixture. The ceramic powder is added in an amount 3 to 4 times the total mass of the mixture of components 1) to 3) so that a sprayable ceramic dispersion is obtained after mechanical mixing. The mixture is transferred to a 10 ml Coltene syringe and applied to the framework body in layers. Then, heat treatment is performed at 150 °C to obtain a green body. Further heat treatment at 300 °C gives a white body, which is then fired at 950 °C.

[0087] Figure 1 is a photograph of the white body before firing obtained in the above process "Example of Manufacture 1". Figure 2 is a photograph of the same white body after firing at 950 °C for 60 minutes, and as can be seen from Figure 2, a ceramic component with a uniform closed structure is obtained.

Claims

1. A set of chemicals comprising the following components, namely: A) A ceramic material comprising or consisting of a silicate ceramic material, and B) A binder, characterized in that the binder comprises or consists of a gelling agent.

2. The set of chemicals according to claim 1, wherein the gelling agent comprises or consists of a polymer having one or more repeating units, and the one or more repeating units preferably have a chelating functional group.

3. The set of chemicals according to claim 2, wherein the polymer is cross-linked.

4. The set of chemicals according to claim 2 or 3, wherein the polymer is a superabsorbent polymer, preferably a copolymer having repeating units of (meth)acrylic acid and / or sodium (meth)acrylate.

5. The set further comprises the following additional component, namely C) A solvent and / or dispersant preferably selected from the group consisting of water and alcohols, according to any one of claims 1 to 4.

6. The set further comprises the following additional component, namely, D) A base preferably selected from the group consisting of hydroxides of alkali metals and alkaline earth metals and carbonates of alkali metals and alkaline earth metals, according to any one of claims 1 to 5.

7. The set further comprises the following additional component, namely, E) A preferably biocidal preservative, according to any one of claims 1 to 6.

8. The set further comprises the following additional component, namely, F) Preferably, Er 2 O 3 , Fe 2 O 3 , Co 3 O 4 , MnO 2 , NiO 2 , Cr 2 O 3 , Pr 2 O 3 , Tb 2 O 3 , Bi 2 O 3 A set of chemical substances according to any one of claims 1 to 7, comprising a coloring component selected from these and mixtures thereof.

9. The set of chemicals according to any one of claims 1 to 8, wherein the weight ratio of the ceramic material to the weight of the set of chemicals is in the range of 50 to 90% by weight, preferably in the range of 60 to 80% by weight.

10. The set of chemicals according to any one of claims 1 to 9, wherein the silicate ceramic material is selected from the group consisting of feldspar, leucite, lithium silicate, lithium disilicate, and lithium aluminosilicate ceramic.

11. A gel or dispersion comprising the set of chemicals defined in any one of claims 1 to 10.

12. a １ (ii) mixing the components of the set of chemical substances as defined in any one of claims 1 to 11 to obtain a gel or a dispersion; b) Optionally, heat-treating the gel or dispersion in a temperature range of 50°C to 200°C to obtain a green body; c) Optionally, heat-treating the green body in a temperature range of 250°C to 350°C to remove the binder and obtain a white body; d) Sintering by heat treatment in a temperature range of 700°C to 1000°C to obtain a ceramic molded part, a process for the preparation of a ceramic molded part.

13. The following additional steps, namely a ２ ) Preferably, a step of applying a gel or a dispersion in layers on a surface by a spray and / or 3D printing process, particularly preferably by binder jetting, material jetting, polyjet or multijet modeling, the manufacturing process of the ceramic molded part according to claim 10.

14. A ceramic molded part obtainable by the process defined in claim 12 or 13.

15. Use of a combination of a silicate ceramic material selected from the group consisting of feldspar ceramics and leucite ceramics and a crosslinked polymer in a gel or dispersion for the production of ceramic molded parts, in particular for the production of ceramic molded parts for dental restorations such as inlays, onlays, veneers, crowns or bridges.

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