slip

Abstract

Slip comprising a powder of an inorganic material or an inorganic material mixture, a binder, a polymerization initiator, and a co-initiator. The objective is to propose a slip with the highest possible filler content and, at the same time, sufficiently low viscosity and good curing behavior. This objective is achieved by providing a photoinitiator as the polymerization initiator and a slip with a powder filler content of between 45 and 75 vol.%, with a particle size distribution based on the respective percentile value d50 between 0.05 and 20 µm.

Description

[0001] The invention relates to a slip containing a ceramic or metal powder and to a method for producing such a slip according to claims 1 and 16, respectively.

[0002] A slip, as mentioned above, is a suspension; it consists of a powder made of an inorganic material or an inorganic material mixture (filler), a binder, a polymerization initiator, a co-initiator, and a solvent to adjust viscosity. Slips are an established intermediate product in powder metallurgy for the production of unsintered metallic or ceramic molded bodies (green bodies) using a casting process with subsequent removal, solidification, or conversion of the solvent, known as slip casting. These semi-finished products are then used for further processing into a finished powder metallurgical component using a debinding and sintering process.

[0003] For example, EP 0 413 456 B1 discloses a process in which ceramic powder containing silicon carbide (SiC) is suspended in ethanol, optionally finely ground, and sieved. The ethanol is then removed, and the resulting powder is pressed into a green body and subsequently sintered in an oxygen atmosphere.

[0004] From DE 10 335 224 A1, a method for producing a shaped body made of ceramic material is also known, in which a metal oxide powder and a metal powder are mixed in a colloidal sol to form a slip, and this slip is then consolidated in a mold to form a green body, in particular by freeze-gelling, and finally the green body is sintered to form the shaped body in an active atmosphere which enables oxidation of the metal powder.

[0005] Likewise, DE 10 2017 203 885 A1 discloses a ceramic suspension comprising a solvent or solvent mixture, a dispersant, a non-functionalized ceramic powder, a monofunctional binder, a multifunctional binder as a crosslinker, and a polymerization initiator. Here, too, the solvent, preferably a branched or linear, monohydric or polyhydric aliphatic alcohol, is proposed.

[0006] An increasingly important field of application for the proposed slip is additive manufacturing (AM) of components and structures made of inorganic materials such as ceramics, but also metals, where the slip is printed layer by layer onto a substrate (3D printing process).

[0007] One of these additive manufacturing processes is bath-based photopolymerization (VPP), in which a slurry, a suspension of ceramic or metal particles and a binder system, is cured in a location-selective manner using light of a defined wavelength, thereby building the component. The invention specifically encompasses a new formulation for a VPP slurry with improved properties and a related process for producing such a slurry.

[0008] Such an application is characterized by a multi-stage additive manufacturing process in which the material from which the future component is to be made is first shaped as a slurry in an AM system, for example through a printing process. Liquid slurry components such as the solvent are removed and / or the binder is solidified through a chemical reaction or other transformation. This creates a green body which, due to the binder content, must have the dimensional stability required for further processing or even for machining. In a subsequent debinding step, the binder and / or the solvent are chemically or thermally removed from the green body; this creates a debindered brown body. This is then sintered, resulting in diffusion-driven rearrangements in the brown body.The brown body is thus further compacted, shrinks and takes on its final shape, density and characteristic properties as a finished component or structure.

[0009] To ensure that as few defects as possible, ideally none at all, occur during debinding and sintering, the highest possible filler content in the slurry is desirable. Furthermore, the achievable component thickness is limited by the necessary debinding step, as the binder and its decomposition products must escape from the component during debinding. A higher filler content is intended to improve debinding behavior and thus enable the realization of thicker-walled components. At the same time, sufficiently good curing and a low viscosity of the slurry for processing in the VPP process must be ensured. These are inherently contradictory goals.

[0010] Slips are suspensions that contain ceramic or metallic fillers on the order of 50% by volume. The remaining 50% consists of a mostly organic binder system and the solvent to adjust the viscosity. Slips as such are therefore not dimensionally stable; they must be solidified. The comparatively high proportion of the binder system is due to two facts or requirements: Firstly, a higher solids content, i.e. metal or ceramic particles, leads to a higher viscosity of the suspension; secondly, a higher solids content impairs the curing behavior of the suspension. In order to accelerate the debinding and sintering following the printing process and to increase process reliability (avoidance of defects, etc.), the highest possible filler content is aimed for.

[0011] When producing a slip, good homogeneity must be ensured. In addition, mixing must be carried out as efficiently as possible, while preventing thermal damage to the slip caused by excessive mixing intensities and excessively long mixing times.

[0012] Due to the composition of a conventional slip, the filler content is limited; in conventional systems, for example, with Al2O3 as a filler, the maximum filler content is approximately 50 vol.%. The solvent, which is one or more polar or non-polar substances with a low boiling point or high volatility and low viscosity, preferably a branched or linear, monohydric or polyhydric aliphatic alcohol, serves only to adjust the slip viscosity and significantly improves miscibility, but is otherwise not involved in the curing reaction.

[0013] However, the requirements for a slip that is suitable for an additive manufacturing process such as the aforementioned VPP process do not only relate to good miscibility, but also to other properties such as good curability and the highest possible dimensional stability even with larger volumes.

[0014] Based on this, one object of the invention is to propose a slip with the highest possible filler content and at the same time sufficiently low viscosity and good and homogeneous curing behavior, which does not have the aforementioned disadvantages and limitations or only has a reduced one.

[0015] A further task is to propose a method for producing such a slip.

[0016] The problem is solved with a slurry having features of the first claim and a method having features of claim 16. Subclaims referring back to these claim describe advantageous embodiments of the slurry and the method.

[0017] To solve this problem, a slip is proposed that essentially requires no solvent admixture and yet is suitable for use in an additive manufacturing process, in particular the VPP process mentioned above, by exhibiting the required low viscosity. A slip is proposed, comprising a powder of an inorganic material or an inorganic material mixture, a binder, a polymerization initiator, and a co-initiator. Preferably, the slip consists only of the aforementioned powder, the binder, the polymerization initiator, and the co-initiator.

[0018] It is essential that the polymerization initiator is a photoinitiator and that the powder has a filler content between 45 vol.%, preferably 50 vol.% or more preferably 55 vol.% and 75 vol.%, preferably 70 vol.% or more preferably 65 vol.% with a particle size distribution based on the respective percentile value d50 between 0.05 and 20 µm. In particular, a particle size distribution is proposed whose ratio of largest to smallest value spans a range of up to a factor of 400 and thus makes a high filler content possible, in particular up to 75%, but preferably the aforementioned range between 45 and 75%, but more preferably a filler content greater than or equal to 50% up to 65 or 75%, and this as a bed, without the need for compression of the filler. Therefore, the fundamentally missing proportion of solvent benefits a higher proportion of solids.Furthermore, the slip must exhibit the low viscosity required for processing even without a solvent. Conversely, this means that the removal or conversion of solvent components known from conventional technologies is not available for solidifying the slip into the green body. This lack of a solidification mechanism is, in turn, compensated for by the fact that the polymerization initiator is a photoinitiator, which can utilize at least the light-accessible surfaces of the green body for its mechanical stabilization.

[0019] The stated problem is therefore solved by an optimized selection, composition, and coordination of the suspension components, whereby the omission of a solvent on the one hand and an increased filler content in the suspension (slip) are proposed on the other. The use of a co-initiator serves to improve curing. The optional, preferably proposed incorporation of mono-, di-, and higher-functional monomers of different functionality, i.e., different numbers of functional groups, in particular multiple or double bonds, preferably hydroxyethyl methacrylate (HEMA), isobornyl acrylate (IBOA), hexanediol diacrylate (HDDA), tetraethylene glycol diacrylate (TEGDA), tripopylene glycol diacrylate (TPGDA), trimethylolpropane triacrylate (TMPTA), ethoxylated trimethylolpropane triacrylate (ETMPTA), serves to further reduce viscosity and further improve curing.The effect of the combination of different functionalities is attributed to increased mobility of free radicals and double bonds combined with low volume shrinkage. In particular, the slip contains no acidic monomers, such as acrylic or methacrylic acid.

[0020] Using powder mixtures as fillers or filler components, especially when the particles have a particle size ratio based on the respective percentile value d50 between 1:1.5, preferably 1:3, and 1:150, preferably 1:50, the viscosity of the slurry can be influenced and a solvent substituted. By combining different monolithic material powders, the component properties can also be modified. The co-initiator serves to further improve the curing of the binder during the production of the green body and thus supports the polymerization initiator intended for this purpose.

[0021] A preferred embodiment of the slip provides a polymerization initiator that is or comprises a camphor derivative, preferably camphorquinone or at least one naphthalene derivative, or a mixture thereof. The selection depends on the wavelength of the light used for appropriate curing and the monomers of the binder.

[0022] A further preferred embodiment of the slip provides a co-initiator consisting of or comprising the group of amines, benzoates, nitriles, phenols, glycines, preferably an ethyl-4-dimethylamino benzoate, 4-dimethylamino-benzonitrile or N-phenylglycine, whereby the curing can be accelerated and intensified.

[0023] A further preferred embodiment of the slip comprises an additive for adjusting the properties of the slip, in particular with regard to its rheology and sedimentation. One embodiment provides for the additive to comprise modified urea and / or polyalkylamine and / or polycarboxylic acid polymer and / or alkylammonium salt of an acidic copolymer and / or salt of an unsaturated polyamine amide and / or phosphoric acid and / or styrene-maleic anhydride copolymer, preferably phosphoric acid ester and / or hydroxy-functional alkylammonium salt of an acidic copolymer. This allows the powder particles in the slip to be stabilized, in particular due to repulsion effects caused by charge differences, and sedimentation can be prevented or at least slowed down.

[0024] A further preferred embodiment of the slip provides a binder composed of a mixture of mono-, di- or multifunctional monomers, wherein more preferably the mass ratio of mono-, di- or multifunctional monomers is between 5:1:1, 1:5:1 to 1:1:5, preferably between 2:1:1, 1:2:1 to 1:1:2, more preferably 2:2:1. They serve in particular to reduce viscosity and improve curing. This improvement is expressed, for example, in a disproportionately strong increase in the storage modulus of the slip after curing compared to no or only a moderate increase in viscosity in the uncured state compared to slips known from the prior art. This effect is attributed to an increased mobility of the free radicals and double bonds with simultaneous low volume shrinkage due to the mixture of monomers of different functionality.It is furthermore proposed that. a) the monofunctional monomer is or comprises monofunctional (meth)acrylates, preferably hydroxyethyl methacrylate (HEMA) or isobornyl acrylate (IBOA), and / or b) the difunctional monomer is or comprises difunctional (meth-)acrylates, preferably hexanediol diacrylate (HDDA), tetraethylene glycol diacrylate (TEGDA) or tripopylene glycol diacrylate (TPGDA), and / or c) the multifunctional monomer is or comprises tri- or tetrafunctional (meth)acrylates, preferably trimethylolpropane triacrylate (TMPTA) or ethoxylated trimethylolpropane triacrylate (ETMPTA).

[0025] A further preferred embodiment of the slip provides that the powder consists as a filler or filler component of a non-functionalized oxide or non-oxide ceramic or of a mixture of these with or without sintering additives. This means that the powder surface has not been modified or altered in terms of its surface texture or chemical affinity by any treatment step, in particular thermal, chemical, mechanical or in any other way, before being incorporated into the slip. By choosing a suitable composition of the slip, complex pretreatment steps for the powder can be eliminated. The powder preferably consists predominantly of Al2O3, ZrO2, Y2O3, SiO2, TiO2, Si3N4, SiC, TiN, BC, AlN, Si3N4, BN, SiAlON or a mixture of these or mixed oxides, carbides or nitrides.

[0026] A further preferred embodiment of the slip provides that the powder comprises a powder mixture with two powder fractions (bimodal particle size distribution) which have a particle size ratio to each other based on the respective percentile value d50 between 1:1.5, preferably 1:3, and 1:150, preferably 1:50. A percentile value with a number between 0 and 100 indicates the value based on the amount of 100% of individual values, in which the ordered individual values are divided into two groups, so that a certain percentage corresponding to the stated number between 0 and 100 lies above and a percentage remaining to 100 lies below.

[0027] A further preferred embodiment of the slip provides that the powder comprises a powder mixture with three powder fractions (trimodal particle size distribution) which differ in a particle size ratio based on the respective percentile values d50 of the equivalent diameter of the particles from 1:5:25 to 1:20:400, preferably in a ratio of 1:7:21 to 1:15:225, particularly preferably in a ratio of 1:10:100, and a mass ratio of the particle fractions from small to medium to large particle size of 5:1:1, 1:5:1 to 1:1:5, preferably between 3:1:1 and 1:4:1 and 1:1:5, more preferably between 2:1:1 and 1:3:1 and 1:1:4.

[0028] A ratio of 1:2:3 has proven particularly advantageous in one exemplary embodiment, with a particularly preferred particle size ratio being proposed for powder mixtures with d50 values of 0.05 µm, 0.5 µm, and 3 µm. Mixing different particle sizes achieves a particularly high packing density of the powder in the slurry and optimized curing, taking light scattering and absorption into account.

[0029] The stated percentile values and mass ratios preferably refer to powder mixtures with the specified two or three powder fractions of the same material. Powder mixtures with powder fractions of different materials are optionally proposed with the same percentile values and mass ratios. The preferred ranges may vary slightly in the presence of physical or chemical interactions, such as repulsive and attractive forces or chemical reactions, taking into account the specific particle surface area and the surface charge or the electrical potential / zeta potential of the powder.

[0030] The aforementioned bimodal or trimodal particle size distribution alone enables, without further measures, compared to a monomodal particle size distribution with only one particle size range, e.g. around a value d50, not only a higher filler content of over 45%, preferably greater than 50% up to values between 70 and 80%, preferably 75%, but also advantageously a viscosity reduction and the setting of a predeterminable viscosity value.

[0031] A further preferred embodiment of the slip provides for an optional, although not necessary, solvent, in which the proportion of the solvent does not exceed 3.0 wt.%, more preferably 0.01 wt.%, based on the slip, in order to increase the filler content and to improve the viscosity and the curing properties.

[0032] The proposed mixture of mono-, di-, tri-, or multifunctional binder components also influences the curing behavior and that of the slurry. The particular advantage of the different functionalities lies in improved curing behavior combined with low slurry viscosity, which is attributed to increased mobility of free radicals and double bonds combined with low volume shrinkage.

[0033] Further advantageous embodiments provide for the use of further additives, for example - anti-skin formers, - Additives for specifying a sensitivity of the slurry at a predetermined wavelength, - Additives for shear-thinning behavior, - Additives for setting definable viscosity ranges depending on the shear rate, - Debinding accelerator

[0034] Further advantageous embodiments provide for the use of surface-modified or particle-formed ceramic or metallic fillers, whereby the dispersion and stabilization of the particles in the slip can be facilitated or improved.

[0035] To achieve the object, a method for producing the aforementioned slip is further proposed, comprising the following process steps: a) providing a powder of an inorganic material or a mixture of materials, a binder, a polymerisation initiator and a co-initiator, b) Weighing of the components of the powder and the binder, c) Mixing the weighed components and the binder to form a mixture, d) adding the polymerization initiator and the co-initiator to the mixture, e) Mixing the mixture of powder and binder with the polymerization initiator and co-initiator to form a slurry.

[0036] It is optionally proposed that the provision according to the aforementioned step a) also comprises an optional solvent and that the mixtures according to steps b) and e) also incorporate the solvent, wherein the proportion of the solvent does not exceed 3.0 wt.%, more preferably 0.01 wt.%, based on the slip.

[0037] Furthermore, as a preferred embodiment of the method, it is proposed that the mixing takes place in a planetary mixer and / or in a ball mill with or without grinding / mixing balls at time intervals, wherein the speed is increased and / or reduced and / or kept constant in and / or between the individual time intervals and / or the individual intervals are separated by pauses, and / or a three-roll mill is used for homogenization. In order to achieve a particularly good, i.e. homogeneous, mixing result, it is further preferably proposed that the said mixing comprise at least three time intervals in the speed sequence high - low - high and that these are separated by pauses, preferably by speeds greater than 1,200 rpm, particularly preferably greater than 1,500 rpm, in the high speed stage, and preferably between 500 and 1.200 rpm in the lower speed stage, preferably with mixing times between 30 and 120 s, particularly preferably between 45 and 90 s, in the individual stages and preferably separated by pause times between 60 and 300 s.

[0038] The proposed omission of a solvent is particularly advantageous, allowing the filler content in the slurry to be significantly increased. The proposed coordination of the remaining slurry components ensures sufficiently good processability in the VPP process, including the adjustment of viscosity, as well as sufficient mechanical stability of the green body.

[0039] The curing behavior of the slip into a green body is supported by the addition of a co-initiator. This co-initiator is matched to the actual photoinitiator and the other binder system in terms of their reaction / curing behavior and their properties, e.g., pH value, and, in a preferred embodiment, comprises a camphorquinone / amine mixture. Specifically, the results for camphorquinone as a photoinitiator have shown that the addition of the co-initiator 4-(dimethylamino)benzonitrile in a photoinitiator to co-initiator ratio of 3:2 leads to particularly good curing results in the green body. Examples of implementation:

[0040] The invention is explained in more detail using two exemplary embodiments (two solvent-free slip compositions according to Table 1). The features mentioned here and their combinations are not limited to these exemplary embodiments and their configurations. Rather, they should be considered representative of other possible configurations that are not explicitly presented as exemplary embodiments. Table 1: Slip compositions (two exemplary compositions) Material Example 1 Example 2 wt.% Vol.% wt.% Vol.% 1-octanol 0,00 0,00 0,00 0,00 BYK 111 / BYK W 969 1,40 3,01 1,13 2,62 Ceramic powder 79,25 50,14 83,23 56,66 of which d50 = 0.05µm 14,27 9,02 14,98 10,20 of which d50 = 0.5µm 27,74 17,55 29,13 19,83 of which d50 = 0.3µm 37,24 23,57 39,12 26,63 Isobornyl acrylate (IBOA) 6,52 16,47 5,26 14,32 Hexanediol diacrylate (HDDA) 6,60 16,30 5,34 14,17 (ethoxylated) trimethylolpropane triacrylate (TMPTA) 3,26 7,32 2,63 636 Camphorquinone 1,79 4,54 1,44 3,95 4-(Dimethylamino-)Benzonitrile 1,19 2,22 0,96 1,93 Sum: 100,00 100,00 100,00 100,00

[0041] In both embodiments, prior to the actual homogenization in a three-roll mill, the ceramic powder and all other binder components, with the exception of the photoinitiator camphorquinone and the co-initiator 4-(dimethylamino)benzonitrile, are first weighed. These components are mixed in several intervals ranging from 15 seconds to 2 minutes, each of which is interrupted by pauses (at least as long) to allow the mixture to cool. Mixing takes place in a planetary mixer at high speeds (in the range 500 to 2000 rpm, preferably in the range 1000 to 2000 rpm). A further improvement in slip homogeneity can be achieved by gradually increasing the speed of the individual stages up to the aforementioned high speeds, using a plastic mixing bowl.

[0042] Within the scope of a preferred embodiment of the exemplary embodiments, the incorporation of ceramic mixing balls (diameter in the range of 2 mm) into the mixture is proposed, whereby the achievable mixing result can be further improved and / or the required mixing time can be shortened.

[0043] In a final mixing step, the photoinitiator camphorquinone and the co-initiator 4-(dimethylamino)benzonitrile are added and mixed for a maximum of 60 seconds. This subsequent mixing prevents premature hardening or solidification of the slurry. Finally, the suspension is processed in a three-roll mill for further homogenization. During the processing time of several minutes, preferably between five and ten minutes, the roller gap is gradually reduced, thereby breaking up agglomerates and increasing the homogeneity of the slurry.

[0044] Compared to conventional slip systems, the invention exhibits improved properties in terms of the ceramic filler content and the processing properties in the VPP process (curing behavior and viscosity). The resulting lower proportion of binder and initiator positively influences the debinding behavior of the components, which also allows for an increase in the maximum possible component thickness. This is due to the optimized selection and coordination of the binder system. The coordination of the proportions of mono-, di-, and tri-functional binder as well as the initiator system with photo- and co-initiator has an advantageous effect and makes it possible to dispense with a solvent and increase the filler content. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] EP 0 413 456 B1

[0003] DE 10 335 224 A1

[0004] DE 10 2017 203 885 A1

[0005]

Claims

[1] Slip, comprising: a powder made of an inorganic material or an inorganic material mixture, b. a binder, c. a polymerization initiator and d. a co-initiator, characterized by , that e. the polymerization initiator is a photoinitiator and f. the slip has a powder filler content between 45 and 75 vol.% with a particle size distribution based on the respective percentile value d50 between 0.05 and 20 µm. [2] Slip according to claim 1, characterized by that the polymerization initiator is or comprises a camphor derivative, preferably camphorquinone or at least one naphthalene derivative or a mixture thereof. [3] Slip according to claim 1 or 2, characterized bythat the co-initiator comes from the group of amines, benzoates, nitriles, phenols, glycines, preferably is or comprises an ethyl 4-dimethylamino benzoate, 4-dimethylamino-benzonitrile or N-phenylglycine. [4] Slip according to one of the preceding claims, comprising an additive for adapting the properties of the slip, in particular with regard to its rheology and sedimentation. [5] Slip according to claim 4, characterized by that the additive comprises modified urea and / or polyalkylamine and / or polycarboxylic acid polymer and / or alkylammonium salt of an acidic copolymer and / or salt of an unsaturated polyamine amide and / or phosphoric acid and / or styrene-maleic anhydride copolymer, preferably phosphoric acid ester and / or hydroxy-functional alkylammonium salt of an acidic copolymer. [6] Slip according to one of the preceding claims, characterized bythat the binder consists of a mixture of mono-, di- or multifunctional monomers. [7] Slip according to claim 6, characterized by that the mass ratio of mono-, di- or multifunctional monomers is between 5:1:1, 1:5:1 and 1:1:5, preferably between 2:1:1, 1:2:1 and 1:1:2, more preferably 2:2:

1. [8] Slip according to claim 6 or 7, characterized by , that a. the monofunctional monomer is or comprises monofunctional (meth)acrylates, preferably hydroxyethyl methacrylate (HEMA) or isobornyl acrylate (IBOA), and / or b. the difunctional monomer is or comprises difunctional (meth)acrylates, preferably hexanediol diacrylate (HDDA), tetraethylene glycol diacrylate (TEGDA) or tripopylene glycol diacrylate (TPGDA), and / or c. the multifunctional monomer is or comprises tri- or tetrafunctional (meth)acrylates, preferably trimethylolpropane triacrylate (TMPTA) or ethoxylated trimethylolpropane triacrylate (ETMPTA). [9] Slip according to one of claims 6 to 8, characterized by that the monofunctional monomer consists of isobornyl acrylate (IBOA), the difunctional monomer consists of hexanediol diacrylate (HDDA) and / or the trifunctional monomer consists of trimethylolpropane triacrylate (TMPTA) [10] Slip according to one of the preceding claims, characterized by that the powder consists of a non-functionalized oxide or non-oxide ceramic or a mixture of these with or without sintering additives. [11] Slip according to claim 10, characterized by that the powder consists predominantly of Al2O3, ZrO2, Y2O3, SiO2, TiO2, Si3N4, SiC, TiN, BC, AlN, Si3N4, BN, SiAlON or a mixture of these or of mixed oxides, carbides or nitrides. [12] Slip according to one of the preceding claims, characterized by that the powder comprises a powder mixture with two powder fractions which have a particle size ratio to one another based on the respective percentile value d50 of between 1:1.5, preferably 1:3, and 1:150, preferably 1:

50. [13] Slip according to one of the preceding claims, characterized by that the powder comprises a powder mixture with three powder fractions which differ in a particle size ratio based on the respective percentile values d50 of the equivalent diameter of the particles of 1:5:25 to 1:20:400, preferably in a ratio of 1:7:21 to 1:15:225, particularly preferably in a ratio of 1:10:100, and have a mass ratio of the particle fractions from small to medium to large particle size of 5:1:1, 1:5:1 to 1:1:5, preferably between 2:1:1, 1:3:1 and 1:1:4, more preferably 1:2:

3. [14] Slip according to one of the preceding claims, comprising a solvent, wherein the proportion of the solvent does not exceed 3.0 wt.% based on the slip. [15] Slip according to claim 14, characterized by that the proportion of solvent does not exceed 0.001 wt.% based on the slip. [16] A process for producing a slip according to any one of the preceding claims, comprising the following process steps: a. Providing a powder of an inorganic material or a mixture of materials, a binder, a polymerization initiator and a co-initiator, b. Weighing of the powder and binder components, c. Mixing the weighed components and the binder to form a mixture, d. Adding the polymerization initiator and the co-initiator to the mixture, e. Mixing the mixture of powder and binder with the polymerization initiator and co-initiator to form a slurry. [17] Method according to claim 16, characterized by that the preparation according to step a) comprises a solvent and the mixtures according to steps b) and e) incorporate the solvent, wherein the proportion of the solvent does not exceed 0.05 wt.% based on the slip. [18] Method according to claim 16 or 17, characterized by that the mixing in steps c) and e) takes place in a planetary mixer and / or in a ball mill with or without grinding / mixing balls at time intervals, wherein the speed is increased and / or reduced and / or kept constant between the individual time intervals and / or the individual intervals are separated by pause times, and / or a three-roll mill is used for homogenization. [19] Method according to claim 18, characterized bythat mixing in steps c) and e) comprises at least three time intervals in the speed sequence high - low - high and these are separated by pause times.