Method for coloring a curable binder composition in an additive manufacturing process and colored suspension

Abstract

1. A method for producing a three-dimensional object by means of an additive manufacturing process from a curable binder composition, comprising adding at least one, such as at least two, in particular at least three, in particular at least four, coloring suspensions comprising color pigments and a solvent, in particular water, to the curable binder composition prior to application of the curable binder composition to color the curable binder composition.

Description

[Technical field]

[0001] The present invention relates to a method for producing a three-dimensional object from a curable binder composition by an additive manufacturing process, in which at least one color suspension is added to color the curable binder composition. Furthermore, the present invention relates to a liquid color suspension for coloring the curable binder composition, as well as to a kit comprising at least two color suspensions. [Background technology]

[0002] In the construction industry, hardenable binder compositions, such as mineral binder compositions, are widely used for a variety of applications, examples of such compositions include mortar, concrete, grout or screed compositions.

[0003] Building elements made from binder compositions that contain cement as binder typically have a grayish color, while gypsum-based compositions are usually white. However, from an architectural and aesthetic point of view, other colors are often desirable. In this regard, painting the surface of the building element is a well-known option. Another approach is to mix color pigments with the binder composition, which allows the building elements made from the hardening composition to be colored in deep colors.

[0004] In this regard, US 2016 / 0221874 A1 (Construction Research & Technology, GmbH) describes, for example, a colored cementitious composition composed of a hydraulic cement and a liquid color suspension. The liquid color suspension contains a polycarboxylate dispersant, a pigment, and a polysaccharide thixotropic additive. The pigment may be an inorganic or organic pigment.

[0005] In the construction sector, there have also been long attempts to use additive manufacturing processes to create geometrically demanding building elements. The term "additive manufacturing process" or "additive manufacturing" refers to a process in which a spatial object or body is created by depositing, applying, and / or solidifying a material into a target space.

[0006] The deposition, application and / or consolidation of materials, such as, for example, a curable binder composition, is performed, in particular, layer by layer, in particular based on a data model of the object to be produced. Each object is typically produced from one or more layers in an additive manufacturing process. Usually, shapeless materials (e.g., liquids, powders, granules, etc.) and / or shape-neutral materials (e.g., tapes, wires) are used to produce objects that undergo, in particular, chemical and / or physical processes (e.g., melting, polymerization, sintering, hardening). Additive manufacturing processes are also referred to, in particular, as "generative manufacturing processes" or "3D printing", etc.

[0007] Coloring in additive manufacturing with a hardenable binder composition can be achieved, for example, by adding color pigments to the dry powder mixture of the binder composition or by adding a coloring solution to the mixed binder composition. In this regard, WO 2019 / 048752 A1 (XTREEE) for example describes a method for coloring cementitious materials in additive manufacturing processes, whereby different colors can be added directly to the cementitious material in the extrusion head of the 3D printing device before extrusion of the material. Summary of the Invention [Problem to be solved by the invention]

[0008] However, uniformly dispersing color pigments in hardenable compositions, such as cementitious compositions, is a difficult task. This is especially true in additive manufacturing, where the pigments are usually pumped through a supply line and need to be mixed uniformly into the hardenable composition in a fairly short time interval, such as when the color pigments are added directly to the extrusion head of a 3D printing device. These difficulties are believed to be caused in part by the rheological properties of the color pigments or solutions containing the color pigments, which are not ideal for pumping and efficiently mixing them with the hardenable composition.

[0009] Furthermore, the addition of color pigments to the hardenable composition may affect the rheology and hardening behavior of the hardenable composition, especially when added in high concentrations, which is also crucial in additive manufacturing, since a defined hardening behavior of the mineral binder composition is crucial for the efficient and accurate construction of building elements or objects, respectively.

[0010] Therefore, there remains a need for new and improved solutions which overcome, to the greatest extent possible, the aforementioned shortcomings. [Means for solving the problem]

[0011] The object of the present invention is to provide an improved solution for the coloring of curable binder compositions in additive manufacturing processes. Thereby, preferably the solution should have as little influence as possible on the additive manufacturing process and on the rheology and / or curing behavior of the curable binder composition. Preferably, the solution should allow easy and reliable mixing of different shades.

[0012] Surprisingly, it has been found that this object can be achieved by means of the features of independent claims 1, 15, 16 and 17.

[0013] The invention therefore particularly relates to a method for producing three-dimensional objects from a curable binder composition by an additive manufacturing process, and to a liquid colouring suspension for colouring a curable binder composition for additive manufacturing.

[0014] The method of the present invention is based on the idea of ​​colouring the curable binder composition by adding at least one, for example at least two, in particular at least three, in particular at least four colour suspensions comprising colour pigments and water to the curable binder composition prior to application of the curable binder composition.

[0015] Solutions based on this method have been found to be very beneficial since the colored suspension can be added to the hardenable binder composition in the print head of the 3D printing device and / or in the supply lines upstream of the print head. This allows the color of the hardenable binder composition to be changed instantly in real time without the need to clean the supply lines when changing colors. Also, the hardenable mineral binder composition can be colored with different colors to create architectural elements with different colored sections within the same printing process.

[0016] Furthermore, the method of the present invention can be implemented in an automated method for coloring three-dimensional objects with different colors based on a data model of the three-dimensional object described in terms of its structure and color.

[0017] The color suspension according to the invention for coloring a curable binder composition for additive manufacturing comprises: a) 5 to 70% by weight, preferably 25 to 70% by weight, of a colour pigment, chosen in particular from organic pigments and carbon black; b) 25 to 70% by weight of a solvent, in particular water; and c) optionally, 0.001 to 30% by weight, preferably 0.001 to 5% by weight, of a defoaming agent; All percentages are given based on the total weight of the color suspension.

[0018] Surprisingly, it has been found that the liquid colour suspension of the present invention is highly beneficial for colouring curable binder compositions for additive manufacturing colouring.

[0019] In particular, the liquid pigment suspensions according to the invention can be pumped over fairly long distances through small pipes, even at fairly high pigment concentrations. In other words, the liquid pigment suspensions of the invention can be formulated to have unexpectedly advantageous rheological properties.

[0020] Also, the liquid colour suspensions according to the invention can be very accurately metered into the hardenable binder composition, even at low dosages in the range of 0.001 to 3% by weight.

[0021] Furthermore, the color suspensions of the present invention are fairly stable, in particular without the need for additional stabilizers.

[0022] Similar to paints, different inventive color suspensions can be premixed or mixed in the hardenable binder composition to create new colors of various intensities, whereby the color and concentration in the hardenable mineral binder composition can be easily controlled by the proportions of the individual color suspensions.

[0023] The coloured suspension of the present invention is therefore highly suitable for use in additive manufacturing processes.

[0024] Particularly preferred embodiments are outlined throughout the description and dependent claims. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0025] The first aspect of the present invention is a) 5 to 70% by weight, preferably 25 to 70% by weight, in particular 40 to 60% by weight, most preferably 45 to 55% by weight of a color pigment, in particular chosen from organic pigments and carbon black; b) 25 to 70% by weight, in particular 40 to 60% by weight, most preferably 45 to 55% by weight of a solvent, in particular water; and c) optionally, 0.001 to 30% by weight, preferably 0.001 to 5% by weight, of a defoaming agent; wherein all percentages are given relative to the total weight of the color suspension.

[0026] In particular such colour pigments are solid substances, in particular powder substances.

[0027] The color pigments can be inorganic and / or organic pigments. In particular, inorganic pigments refer to chemical compounds that do not have carbon-hydrogen bonds, such as metal oxides and carbon black. Thus, in particular, organic pigments refer to compounds that contain carbon-hydrogen bonds. Organic pigments include, for example, metal-organic pigments, such as phthalocyanine dyes.

[0028] The colored pigments can be, for example, organic dyes, metal organic dyes, metal oxides, silicates, metal phosphates, aluminates, carbonates, hydroxides, vanadates, nitrites, chromates, sulfides, selenides, sulfates, and / or carbon black.

[0029] Inorganic pigments include, for example, TiO2, BaSO4, Sb2O3, ZnO, magnetite, MnO2, Cd2SSe, FeO, Fe2O3, ZnCrO4, SnS2, CdS, BiVO4, Cr2O3, CoZnO2, Cu2CO3(OH)2, CaCuSi4O 10 , Co-aluminates, ultramarines and / or carbon black.

[0030] The carbon black may be selected, for example, from acetylene black, channel black, furnace black, lamp black, and / or thermal black.

[0031] In particular, the coloured pigments, in particular organic pigments, are chosen from red, blue, green, magenta and / or yellow pigments, which can be used as primary colours to be mixed in various amounts to create a colour gamut.

[0032] In particular, the color pigment comprises an organic pigment and an inorganic pigment, or the color pigment is a mixture of an organic pigment and an inorganic pigment.

[0033] In one particularly preferred embodiment, the color pigment is selected from organic pigments and carbon black.

[0034] In particular, in this case, the color pigment is essentially free of inorganic pigments other than carbon black. In particular, the color pigment comprises less than 1% by weight, in particular less than 0.1% by weight, preferably less than 0.01% by weight, of inorganic pigments other than carbon black, relative to the total amount of the color pigment.

[0035] Furthermore, the carbon black in this case is preferably selected from acetylene black, channel black, furnace black, lamp black and / or thermal black.

[0036] Surprisingly, it has been found that organic pigments can be used in significantly lower concentrations to obtain similar or even stronger shades, when compared to inorganic pigments, such as, for example, oxide-based pigments. Thus, less suspension dosage is required, and therefore less liquid is added to the binder composition during the additive manufacturing process. This further helps to keep the rheology and curing behavior of the curable binder composition at a constant level. Also, organic pigments can be more concentrated in the solvent, which further reduces the amount of liquid added in the process, and the shade obtained in the cured binder composition is typically much stronger.

[0037] Preferably, the organic pigment is a material selected from phthalocyanine dyes, quinophthalone dyes, naphthol dyes, diketopyrrolopyrrole dyes, quinacridone dyes, dioxazine dyes, arylide dyes, and / or pyrazoloquinazolone dyes, which have been found to be sufficiently stable in the hardenable binder composition, in particular in the mineral binder composition, and at the same time, they are able to color the hardenable binder composition at fairly low dosages.

[0038] However, other materials may also be suitable.

[0039] In particular in these special embodiments in which the colour pigments are selected from organic pigments and carbon black, the colour suspension comprises less than 1% by weight, in particular less than 0.1% by weight, preferably less than 0.01% by weight, of inorganic pigments other than carbon black, in particular oxidic pigments, relative to the total weight of the colour suspension. Nevertheless, in special applications, higher proportions of inorganic pigments can be added, if necessary.

[0040] The solvent is preferably selected so that the color pigment is suspended in the solvent, for example the solvent is a polar substance, most preferably water, this is especially true when the color suspension is used for coloring a mineral binder composition.

[0041] Optionally, the color suspension includes a defoamer, which helps to reduce foaming that occurs when mixing the color pigment, especially the organic pigment, with the solvent.

[0042] Preferably the defoaming agent is selected from water insoluble compounds.

[0043] In particular, the defoaming agent is selected from kerosene, liquid paraffin, animal oils, vegetable oils, sesame oil, castor oil, alkylene oxide adducts thereof, oleic acid, stearic acid and alkylene oxide adducts thereof, diethylene glycol laurate, glycerol monoricinoleate, alkenylsuccinic acid derivatives, sorbitol monolaurate, sorbitol trioleate, polyoxyethylene monolaurate, polyoxyethylene sorbitol monolaurate, natural waxes, linear or branched fatty alcohols and their alkoxylated derivatives, octyl alcohol, hexadecyl alcohol, acetylene alcohol, glycols, polyoxyalkylene glycols, polyoxyalkylene amides, polyamine acrylates, tributyl phosphate, sodium octyl phosphate; aluminum stearate, calcium oleate, silicone oils, silicone pastes, silicone emulsions, organically modified polysiloxanes, fluorosilicone oils; and / or polyoxyethylene polyoxypropylene adducts.

[0044] For example, a suitable antifoaming agent is Agitan® 218 available from Muenzing Chemie GmbH (Germany). Agitan® 218 is a blend of liquid hydrocarbons, modified fatty compounds, non-ionic emulsifiers and silicones.

[0045] The proportion of antifoaming agent may range from 0.001 to 30% by weight, preferably from 0.001 to 5% by weight, in particular from 0.01 to 2% by weight and especially from 0.1 to 1.6% by weight, relative to the total weight of the colour suspension.

[0046] Furthermore, the color suspension may further comprise additives for controlling the chemical and / or physical properties of the curable binder composition. Examples of such additives are explained below in connection with the method of the invention. For example, the proportion of the additives may be selected in the range of 0.001 to 30% by weight, preferably 0.001 to 10% by weight, in particular 0.01 to 5% by weight, relative to the total weight of the color suspension.

[0047] A further aspect of the present invention relates to a method for producing a color suspension as described above, whereby a color pigment, in particular selected from organic pigments and carbon black, is mixed with a solvent and optionally a defoamer. Most preferably, the mixture thus obtained is subjected to a high speed mixing process. This allows a very homogeneous and stable color suspension to be obtained.

[0048] Another aspect of the invention is directed to a kit comprising at least two, in particular at least three, in particular at least four, colour suspensions as described above, each of the at least two colour suspensions comprising a different colour pigment. In particular, the colour pigment contained in each of the at least two colour suspensions comprises an organic pigment, an inorganic pigment or a mixture of organic and inorganic pigments. In particular, the colour pigment contained in each of the at least two colour suspensions is selected from organic pigments and carbon black.

[0049] Using such a kit, different colours from at least two colour suspensions can be mixed in a simple and reproducible manner.

[0050] Most preferably, the kit comprises at least one color suspension with a color pigment having a color different from black, in particular chosen from organic pigments, and a color suspension with a color pigment chosen from carbon black. In particular, the color pigment having a color different from black is chosen from red, blue, green, magenta and / or yellow pigments.

[0051] Even more preferably, the kit comprises at least three color suspensions comprising a color pigment having a color different from black, in particular selected from organic pigments, and a further color suspension comprising a color pigment selected from carbon black, each of the color pigments having a different color. In particular, the color pigment having a color different from black is selected from red, blue, green, magenta and / or yellow pigments. This allows mixing any kind of color with a wide range of intensities.

[0052] Furthermore, the kit may comprise at least one, two, three or four colour suspensions comprising additives for controlling the chemical and / or physical properties of the curable binder composition. Examples of such additives are described below in connection with the method of the invention. For example, the proportion of additives may be selected in the range of 0.001 to 30% by weight, preferably 0.001 to 10% by weight, in particular 0.01 to 5% by weight, relative to the total weight of the colour suspension.

[0053] The kit may also further comprise additives as separate components for controlling the chemical and / or physical properties of the curable binder composition, examples of such additives being described below in relation to the method of the invention.

[0054] Another aspect of the invention is directed to a method for producing a three-dimensional object by an additive manufacturing process, in particular a generating free space process, from a hardenable binder composition, in particular a mineral binder composition, wherein prior to applying the hardenable binder composition at least one, such as at least two, in particular at least three, in particular at least four color suspensions comprising color pigments and a solvent, in particular water, are added to the hardenable binder composition to color the hardenable binder composition.

[0055] The at least one colour suspension used in the method of the invention is a colour suspension comprising a colour pigment and a solvent, in particular water, whereby the suspension comprises for example 1 to 99% by weight, in particular 5 to 95% by weight, of colour pigment and 1 to 99% by weight, in particular 5 to 95% by weight, of solvent.

[0056] In particular, the colour pigments and / or the solvent are selected as described above in relation to the first aspect or the colour suspensions of the invention, respectively, although at least one colour suspension may differ from the colour suspension according to the first aspect.

[0057] Nevertheless, in one particularly preferred embodiment, at least one colour suspension used in the method of the invention is a colour suspension according to the first aspect of the invention described above.

[0058] The hardenable binder composition may be, for example, a reactive resin, a mineral binder composition, or a mixture thereof. Most preferably, the hardenable binder composition is a mineral binder composition.

[0059] Reactive resins are in particular liquid or liquefiable synthetic resins that cure by polymerization or polyaddition to form duromers, for example unsaturated polyester resins, vinyl ester resins, acrylic resins, epoxy resins, polyurethane resins, and / or silicone resins may be used.

[0060] The term "mineral binder" refers in particular to a binder that reacts in the presence of water in a hydration reaction to form a solid hydrate or hydrate phase, which can be, for example, a hydraulic binder (e.g., cement or hydraulic lime), a latent hydraulic binder (e.g., slag), a pozzolanic binder (e.g., fly ash), or a non-hydraulic binder (e.g., gypsum or white lime).

[0061] Thus, a "mineral binder composition" is a composition that contains at least one mineral binder. In particular, it contains a binder, aggregate, water, and optionally one or more additives. The aggregate may be, for example, aggregate, gravel, sand (natural and / or processed (e.g., crushed) form) and / or filler.

[0062] In particular, at least one colour suspension is added to a hardenable binder composition in a hardening stage. In the case of a mineral binder composition, the composition is in a hardening stage after mixing the mineral binder and optionally further components such as aggregates with mixing water. The expression "hardenable binder composition in a hardening stage" therefore means in particular a hardenable binder composition in a state in which the hardening of the binder in the hardenable binder composition has started but is not yet complete.

[0063] In particular, the curable binder composition is prepared in an ongoing curing state by mixing the components of the curable binder composition in a mixing unit. Most preferably, the curable binder composition is prepared in an ongoing curing state continuously, in particular during application of the curable binder composition.

[0064] Preferably, the at least one color suspension is added to the curable binder composition by means of a feed device and an inlet nozzle. Preferably, the feed device and / or the inlet nozzle are controllable, in particular by the control unit. This allows the dosage of the color suspension to be controlled.

[0065] More preferably, at least one colour suspension is added to the hardenable binder composition using a colour mixing device configured to separately add at least two, especially at least three, especially at least four different colour suspensions to the hardenable binder composition.

[0066] In particular, the control unit is connected to a flow meter, a pressure sensor and / or a dosing valve for controlling the flow rate or proportion of at least one color suspension. In case of more than one color suspension, the control unit is connected to at least one flow meter, a pressure sensor and / or a dosing valve for controlling the flow rate or proportion of each color suspension individually.

[0067] In a possible embodiment, each of the at least one color suspension is introduced separately into the hardenable binder composition without being premixed.

[0068] For example, the color mixing device may include a separate feeder and separate inlet nozzle for each of the color suspensions, which allows each of the color suspensions to be introduced separately into the curable binder composition without premixing.

[0069] In another highly preferred embodiment, all of said at least one colour suspension are premixed before said mixed colour suspensions are introduced into said hardenable binder composition.

[0070] Thereby, for example, the color mixing device comprises a manifold having separate inlet ports for each of the color suspensions and a common outlet port in fluid communication with a single inlet nozzle. This allows each of the color suspensions to be separately dosed into the manifold and the color suspensions to be premixed before the mixed color suspension is introduced into the curable binder composition through the single inlet nozzle. This has been found to be surprisingly beneficial in reducing dead volume in the printhead and reduces cleaning efforts. Furthermore, a more uniform distribution of the color pigments in the curable composition may be achieved.

[0071] Thus, in a preferred embodiment, at least two, in particular at least three, in particular at least four colour suspensions are added simultaneously and / or sequentially to the hardenable binder composition, whereby each of the at least two colour suspensions comprises a different colour pigment.

[0072] Preferably, the respective proportions of the at least one colour suspension, in particular the at least two colour suspensions, that are added to the hardenable binder composition are controlled by a control unit.

[0073] The control unit is preferably configured to control the proportions of the at least one pigmented suspension to obtain a pigmented curable binder composition having a preselected target color.

[0074] According to a preferred embodiment, in order to obtain a three-dimensional object having at least two different colors, in particular a plurality of different colors, the proportions of at least one colored suspension, in particular the respective proportions of at least two colored suspensions, are changed at least once, in particular a plurality of times, during the production of the three-dimensional object.

[0075] More preferably, the proportion of the at least one colour suspension is determined based on a pre-established relationship between the proportion of the at least one colour suspension in the hardenable binder composition and coordinates in a colour model, in particular the HSV model, representing the target colour.

[0076] In particular, for different types of hardenable binder compositions, individual relationships are established between the proportion of at least one color suspension in the hardenable binder composition and the coordinates in the color model, thereby improving the color fidelity of the three-dimensional object.

[0077] A color model is an abstract mathematical model that describes how to represent colors as a tuple of numerical values, usually three or four values ​​or color components. HSV stands for Hue, Saturation, and Lightness, which are cylindrical coordinates in the HSV color model. The H coordinate ranges from 0 to 360°, the S coordinate ranges from 0 to 100%, and the V coordinate ranges from 0 to 100%. The HSV color model represents an alternative representation of the RGB (Red, Green, Blue) color model.

[0078] In particular, the proportion of the at least one colour suspension is determined based on a pre-established relationship, in particular an experimentally determined relationship, between the proportion of the at least one colour suspension in the hardenable binder composition and coordinates in a colour model, in particular the HSV model, representing the target colour.

[0079] The pre-established relationship may be determined experimentally, for example, by adding a predetermined concentration of a color suspension to a test composition and determining the resulting color coordinates.

[0080] Thereby, preferably, when determining the proportion of the at least one color suspension, a pre-established relationship, in particular an experimentally determined relationship, between the proportions of at least two different color suspensions in the hardenable binder composition and at least one coordinate in a color model, in particular the H coordinate in the HSV model, is taken into account.

[0081] Further preferably, when determining the proportion of the at least one color suspension, a pre-established relationship between the total concentration of the at least two different color suspensions in the curable binder composition and at least one coordinate in a color model, in particular the S coordinate and / or the V coordinate in the HSV model, is taken into account, whereby preferably the at least one coordinate is different from the at least one coordinate of the last paragraph.

[0082] In particular, the proportions of the at least one coloured suspension are changed at least once, in particular at least twice, during the production of the three-dimensional object, in particular to obtain three-dimensional structures with different colours for different sections.

[0083] If the target color is changed at least once, in particular at least twice, during the production of the three-dimensional object, the proportions of the at least one colored suspension, in particular the respective proportions of the at least two colored suspensions, are preferably adjusted by a control unit in order to change the color of the colored curable binder composition accordingly.

[0084] More preferably, the respective proportions of the at least one colored suspension, in particular the at least two colored suspensions, added to the curable binder composition are determined taking into account the flow properties, e.g. the flow rate, of the curable material used in the additive manufacturing process. In particular, the flow properties are determined using a measuring unit comprising an ultrasonic transducer. The flow properties are preferably measured upstream of the print head, in particular in the supply line. In this case, the control unit is preferably configured to control the respective proportions of the at least one colored suspension, in particular the at least two colored suspensions accordingly.

[0085] In particular, the at least one colour suspension is added to the hardenable mineral binder composition in a proportion of 0.001 to 3% by weight, in particular 0.01 to 1.5% by weight, for example 0.1 to 1% by weight.

[0086] Preferably, the at least one color suspension is added in a section of the hardenable binder composition comprising the at least one color suspension such that the color pigment is uniformly distributed throughout the hardenable binder composition.

[0087] After the addition of at least one color suspension, the curable binder composition is preferably passed through at least one static and / or dynamic mixer, which allows for uniform dispersion of the color pigments in the curable binder composition. If more than one color suspension is added, the static and / or dynamic mixer effectively mixes the different color pigments to obtain a mixed color in the curable binder composition.

[0088] Preferably, the curable binder composition is applied by means of a printhead movable in at least one spatial direction to form a three-dimensional structure, whereby in particular the curable binder composition is applied layer by layer.

[0089] Preferably, at least one colour suspension is added to the hardenable binder composition after at least the mixing stage, in particular in the curing process.

[0090] In particular, at least one colour suspension is added to the curable binder composition in the printhead and / or in a supply line upstream of the printhead, in particular between at least one mixing stage and the printhead.

[0091] When present, the color mixing device described above is preferably located within the printhead and / or in the feed line upstream of the printhead.

[0092] In a further preferred embodiment, additives for controlling the chemical and / or physical properties of the curable binder composition in the curing process are added to the curable binder composition in the curing process in the print head, in the feed line upstream of the print head and / or together with the color suspension, in particular in the color mixing device, in particular via an additive feeder, optionally by means of an additive inlet nozzle, which additive feeder and / or additive inlet nozzle are preferably controllable, in particular by the abovementioned control unit.

[0093] The additives are preferably substances capable of controlling and / or modifying the flow properties and / or the hardening behavior of the hardenable binder composition. Preferably, the additives are selected from accelerators, retarders, rheological aids, surfactants and / or superplasticizers, especially in the case of mineral binder compositions.

[0094] In a possible embodiment, additives for controlling the chemical and / or physical properties of the curable binder composition are added to the curable binder composition separately from the at least one pigment suspension.

[0095] The surfactant may have the beneficial effect of stabilizing the pigment suspension when mixed with the curable binder composition during the curing process.

[0096] Surfactants are well known to experts and are summarized, for example, in "Surfactants and Polymers in aqueous solutions" (Wiley-VCH, K. Holmberg et al, 2nd Edition, 2007). Surfactants can be non-ionic, cationic, anionic or zwitterionic surfactants.

[0097] Suitable surfactants in the context of the present invention include lipids such as cholates, glycocholates, fatty acid salts, glycerides, glycolipids, and phospholipids. These may be naturally derived or synthetically produced. In certain embodiments, non-ionic lipids are preferred.

[0098] Suitable anionic surfactants include alkyl ether carboxylates, alkyl sulfates, alkyl ether sulfates, lauryl ether sulfonates, naphthalene sulfonates, alkyl sulfosuccinates, alkyl phosphates, alkyl ether phosphonates, and alkyl benzene sulfonates, among others.

[0099] Suitable nonionic surfactants are, in particular, alkylphenol alkoxylates, alkoxylated polysaccharides, fatty acid amide alkoxylates, alkoxylated alkylamines with alkyl radicals of 6 to 20 carbon atoms, alkyl glycosides, alkyl glucamides, hydrophobized starches and hydrophobized celluloses. Preferred alkoxylates in this context are, in particular, ethoxylates.

[0100] Suitable cationic surfactants in particular contain an ammonium group or a quaternary nitrogen atom and also have at least one long-chain alkyl radical. Examples of cationic surfactants are betaines, amidobetaines, imidazolines, and amine N-oxides.

[0101] In a further preferred embodiment, at least one color suspension and all of the additives for controlling the chemical and / or physical properties of the hardenable binder composition are premixed before introducing the mixture of color suspension and additives into the hardenable binder composition.

[0102] In particular, at least one, in particular two, three or four, colour suspensions are each provided in admixture with additives for controlling the chemical and / or physical properties of the curable binder composition, and these mixtures and optionally further additives can then be introduced into the curable binder composition either separately or after being mixed with one or more other colour suspensions and / or further additives.

[0103] Particularly preferably, additives for controlling the chemical and / or physical properties of the curable binder composition are added to the curable binder composition in the color mixing device, in particular via the manifold described above, whereby preferably the manifold comprises an inlet port for each of the color suspensions, at least one inlet port for the additives, and a common outlet port in fluid communication with a single inlet nozzle, thereby allowing the color suspensions and the additives to be separately fed into the manifold and the color suspensions and the additives to be premixed before introducing the mixture into the curable binder composition via the single inlet nozzle.

[0104] This further reduces the dead volume and cleaning effort in the printhead, and also makes it easier to achieve a uniform distribution of color pigments and additives in the curable composition.

[0105] A further preferred embodiment is a) after addition of at least one color suspension, in particular after addition of at least two color suspensions to the curable binder composition, measuring the color of the colored curable binder composition with a color measuring device before and / or during application in order to obtain the actual color of the colored curable binder composition; b) determining in the control unit the color deviation between the measured actual color and a preselected target color; c) adjusting the proportions of at least one color suspension, in particular the respective proportions of at least two color suspensions, taking into account the color deviations in order to correct the color deviations, in particular so that the actual color of the colored curable binder composition is adjusted to correspond to the selected target color; and steps a) to c) are repeated continuously, at least for a selected period of time, in particular permanently, during the production of the three-dimensional object.

[0106] Thereby, dolor deviations can be corrected in real time, which makes it possible to produce three-dimensional objects that actually have the desired target color.

[0107] In particular, a color measurement device is a device capable of measuring the color of an object and providing the color of the object in coordinates of a color model, such as, for example, the HSV color model.

[0108] In a further advantageous embodiment, after the curable binder composition is applied in an additive manufacturing process, the outer surface of the applied curable binder composition and / or the outer surface of the three-dimensional object produced in the additive manufacturing process is at least partially or completely hydrophobized.

[0109] Hydrophobization aids in preserving color, for example when weathered, especially for exterior surfaces that have a grayish and / or black color.

[0110] Thus, in a preferred embodiment, at least a portion of the outer surface having a greyish and / or black color is hydrophobized.

[0111] For example, hydrophobization can be achieved by applying, in particular by spraying, a hydrophobizing agent to the respective outer surface. The hydrophobizing agent can be selected, for example, from silane-, siloxane- and / or siliconate-based hydrophobizing agents. Such agents are, for example, commercially available under the trade name Sikaguard® from Sika Services AG (Switzerland). However, other agents can also be used, such as oil-, fat- or wax-based agents.

[0112] Another highly preferred aspect of the present invention relates to a method for producing a three-dimensional object having at least one desired target color, in particular two or more target colors, whereby said three-dimensional object is produced from a curable binder composition using an additive manufacturing apparatus, a) receiving a target color in a control unit of the additive manufacturing device, in particular from a user interface and / or a machine interface; b) determining, using the control unit of the additive manufacturing apparatus, the proportion of at least one color suspension, in particular the proportion of at least two color suspensions, in the curable binder composition necessary to obtain a colored curable binder composition having the desired target color, said determining being based on a predefined color model stored in a memory unit of the additive manufacturing apparatus; c) adding said at least one color suspension, in particular said at least two color suspensions, to said hardenable binder composition in said proportion determined in step b) by means of one or more inlet devices, in particular one or more actuators, controlled by said control unit; d) applying said pigmented curable binder composition by means of a printhead to form said three-dimensional object; wherein steps c) to d), in particular steps a) to d), are continuously repeated during the production of said three-dimensional object.

[0113] In particular, the method is a computer-implemented method.

[0114] The suspension used in this method may be the same as or different from that described above. Moreover, this method may further implement all of the features and steps of the method described above. Nevertheless, it is also possible to implement the method without this, if desired.

[0115] Preferably, in step b), the determination of the proportion of the at least one color suspension, in particular the proportion of the at least two color suspensions, in the curable binder composition necessary to obtain a colored curable binder composition with the desired target color is based on a pre-established relationship between the proportion of the at least one color suspension in the curable binder composition and the coordinates in a color model, in particular the HSV model, which represent the target color.

[0116] Thereby, preferably for different hardenable binder compositions, individual relationships between the proportion of at least one color suspension in the hardenable binder composition and the coordinates in the color model are established, which improves the color fidelity of the three-dimensional object.

[0117] In particular, at least two different target colours are received by the control unit in step a), in particular one after the other in time, and a three-dimensional object is produced having sections coloured in at least two different colours.

[0118] In particular, the target colors received by the control unit in step a) are pre-determined based on a data model of the three-dimensional object describing the three-dimensional object in terms of structure and color, thereby making it possible to automatically provide different sections of the three-dimensional object with desired target colors.

[0119] More preferably, the method comprises the steps of: a) measuring the color of the pigmented curable binder composition with a color measuring device before and / or during application to obtain the actual color of the pigmented curable binder composition; b) determining in the control unit the color deviation between the measured actual color and the preselected target color; c) adjusting the proportions of at least one color suspension, in particular the respective proportions of at least two color suspensions, taking into account the color deviations in order to correct the color deviations, in particular so that the actual color of the colored curable binder composition is adjusted to correspond to the selected target color; and steps a) to c) are repeated continuously, at least for a selected period of time, in particular permanently, during the production of the three-dimensional object.

[0120] In particular, all of the above methods may be carried out using an apparatus as described below. Thus, any feature described below in relation to an apparatus may be implemented in the above methods as appropriate.

[0121] In a further aspect, the present invention is directed to an additive manufacturing apparatus comprising means adapted to perform the above-mentioned method and / or to an apparatus for manufacturing three-dimensional objects from a curable binder composition using an additive manufacturing process, in particular a robotic system, whereby the apparatus comprises a feed device and an inlet nozzle for adding at least one colored suspension, in particular at least two or more colored suspensions, to the curable binder composition to obtain a colored curable binder composition, whereby the feed device and / or the inlet nozzle are controllable by a control unit, the control unit being configured to control the proportion of the at least one colored suspension in order to obtain a colored curable binder composition of a preselected target color.

[0122] In particular, the apparatus is configured to carry out the above method, and therefore all the functions described in relation to the above method may be implemented in the apparatus, as appropriate.

[0123] In particular, the apparatus comprises a flow meter, a pressure sensor and / or a dosing valve connected to the control unit for controlling the flow rate or proportion of at least one colour suspension. If the apparatus is configured to add more than one colour suspension to the curable binder composition, the apparatus preferably comprises a flow meter, a pressure sensor and / or a dosing valve connected to the control unit for each of the colour suspensions, thereby allowing the flow rate or proportion of the colour suspensions to be controlled individually.

[0124] The control unit is preferably configured such that the proportions of the at least one colour suspension are automatically determined based on the coordinates of a colour model, in particular the HSV model, which represents the desired target colour.

[0125] In particular, the control unit is configured such that the proportion of the at least one color suspension is determined based on a pre-established relationship, in particular an experimentally determined relationship, between the proportion of the at least one color suspension in the hardenable binder composition and coordinates in a color model, in particular the HSV model, representing the target color.

[0126] The pre-established relationship may be determined experimentally, for example, by adding a predetermined concentration of a color suspension to a test composition and determining the resulting color coordinates.

[0127] Thereby, preferably, the control unit is configured such that, when determining the proportion of the at least one color suspension, a pre-established relationship, in particular an experimentally determined relationship, between the proportions of the at least two different color suspensions in the hardenable binder composition and at least one coordinate in the color model, in particular the H coordinate in the HSV model, is taken into account.

[0128] Further preferably, the control unit is configured such that, when determining the proportion of the at least one color suspension, a pre-established relationship between the total concentration of the at least two different color suspensions in the curable binder composition and at least one coordinate in a color model, in particular the S coordinate and / or the V coordinate in the HSV model, is taken into account, whereby preferably the at least one coordinate is different from the at least one coordinate of the last paragraph.

[0129] In particular, the apparatus further comprises a colour mixing device configured to separately add at least two, in particular at least three, in particular at least four different colour suspensions to the curable binder composition.

[0130] In particular, in the first embodiment, the color mixing comprises a separate feeder and a separate inlet nozzle for each color suspension, in particular each separate feeder and / or each separate inlet nozzle being controllable by the control unit, which allows each of the color suspensions to be introduced separately into the curable binder composition without premixing.

[0131] In another highly preferred embodiment, the color mixing device includes a manifold having separate inlet ports for each color suspension and a common outlet port in fluid communication with a single inlet nozzle, allowing each of the color suspensions to be separately dosed into the manifold and the color suspensions to be premixed before the mixed color suspensions are introduced into the curable binder composition through the single inlet nozzle.

[0132] The apparatus preferably comprises a print head that is movable in at least one spatial direction to form a three-dimensional structure. The print head has a print head outlet, in particular an outlet nozzle, for applying the curable binder composition. If desired, the print head may comprise a controllable outlet, in particular in the form of an openable and closable outlet nozzle. In this case, the openable and closable outlet nozzle is preferably controllable by a control unit.

[0133] In particular, the apparatus includes a supply line for supplying a curable binder composition to a printhead.

[0134] Preferably, at least one mixing stage or mixing unit, in particular a static and / or dynamic mixer, is arranged upstream of the feed device and the inlet nozzle or upstream of the color mixing device, if present, In particular, the at least one mixing stage is arranged such that the curable binder composition is mixed before entering the feed line and / or as it passes through the feed line.

[0135] Preferably, the supply lines are in fluid communication with one or more receptacles containing the individual components of the hardenable binder composition, such as, for example, binder, water, aggregates and / or additives, which may be mixed in at least one mixing stage prior to and / or during entry into the supply lines.

[0136] In particular, the apparatus comprises at least one mixer, in particular a static mixer and / or a dynamic mixer, which is arranged downstream of the feed device and the inlet nozzle for adding at least one color suspension to the curable binder composition, or downstream of the color mixing device, if present. In particular, the at least one mixer is arranged between (i) the printhead outlet, in particular the outlet nozzle, and (ii) the feed device and the inlet nozzle for adding at least one color suspension to the curable binder composition, or between (i) the printhead outlet, in particular the outlet nozzle, and (ii) the color mixing device.

[0137] In particular, the feed device and the inlet nozzle for adding the at least one color suspension to the curable binder composition, or the color mixing device, are arranged so that the at least one color suspension can be added to the curable binder composition in the print head and / or in the feed line upstream of the print head, in particular between the at least one mixing stage and the print head.

[0138] In a further preferred embodiment, the apparatus comprises an additive feeder, optionally with an additive inlet nozzle, configured to add additives to the curable binder composition in the print head, in the mixing device and / or in the feed line upstream of the print head, additives for controlling the chemical and / or physical properties of the curable binder composition as described above. The additive feeder and / or the additive inlet nozzle are preferably controllable, in particular by the control unit as described above.

[0139] Particularly preferably, such manifolds are configured to additionally add additives to the curable binder composition to control the chemical and / or physical properties of the curable binder composition.

[0140] Thus, preferably, the mixing device comprises a manifold having an inlet port for each of the color suspensions, at least one inlet port for the additives, and a common outlet port in fluid communication with a single inlet nozzle, as explained above, which allows the color suspensions and additives to each be separately charged to the manifold and the color suspensions and additives to be premixed before introducing the mixture into the curable binder composition via the single inlet nozzle.

[0141] Further preferably, the device comprises a measuring unit, preferably arranged upstream of the print head, designed to determine the flow properties, for example the flow rate, of the curable binder composition in the curing stage in the supply line. In particular, the measuring unit comprises an ultrasonic transducer. The measuring unit is preferably connected to a control unit. In this case, the control unit is preferably configured to control the proportion of the at least one color suspension taking into account the flow properties of the curable binder composition in the curing stage in the supply line. According to a particularly preferred embodiment, the flow rate of the at least one color suspension or of the color suspension mixture is proportional to the flow rate of the binder composition in the curing stage.

[0142] Furthermore, the apparatus preferably comprises a color measurement device specifically configured to measure the color of the curable binder composition and provide the color of the curable binder composition in coordinates of a color model, such as the HSV color model. Such devices are commercially available.

[0143] For example, a color measurement device may be located within the printhead or at the printhead outlet, particularly the outlet nozzle, in which case the color of the curable binder composition may be measured immediately upon exiting the printhead.

[0144] In particular, the control unit of the device includes a processor, a memory unit, and a number of interfaces for receiving data and for controlling the individual components of the apparatus.

[0145] A further aspect of the invention is directed to a computer program comprising instructions for causing an apparatus as described above to carry out a method as described above.

[0146] Another aspect of the invention is directed to the use of a colour suspension as described above or a kit as described above for colouring a curable binder composition, in particular in an additive manufacturing process.

[0147] Further advantageous embodiments of the invention are evident from the exemplary embodiments.

[0148] The drawings used to explain the embodiments are as follows: [Brief description of the drawings]

[0149] [Figure 1] 1 is an exemplary system for producing a three-dimensional colored object by an additive manufacturing process from a curable binder composition configured to allow separate addition of a color suspension to the curable binder composition. [Diagram 2]FIG. 2 is another exemplary system for producing three-dimensional colored objects by an additive manufacturing process from a curable binder composition, the system including a manifold for premixing a color suspension prior to adding the mixed color suspension to a curable binder composition. [Figure 3a] 1 is a graph showing the H, S, and V coordinates versus concentration for each of four different colored suspensions. [Figure 3b] 1 is a graph showing the H, S, and V coordinates versus concentration for each of four different colored suspensions. [Figure 3c] 1 is a graph showing the H, S, and V coordinates versus concentration for each of four different colored suspensions. [Figure 4] Dependence of the H coordinate on the mixing ratio of blue and red colored suspensions (blue / red mix). [Diagram 5] Dependence of the S coordinate on the total concentration of the red / yellow mixture. [Figure 6] Dependence of the V coordinate on the total concentration of the red / blue and red / yellow mixtures. [Figure 7] Dependence of the V coordinate on the total concentration of the yellow / blue mixture. [Figure 8] The effect of black pigment on the V coordinate of different colors. [Figure 9] A user interface for selecting a target color. EXAMPLES

[0150] Colored Suspension The following color suspension was prepared by mixing the ingredients in a high speed mixer:

[0151] [Table 1]

[0152] Xfast Bl 7080, Xfast Yll 0962, and Xfast Red are organic pigments with the colours shown in Table 1, whereas Xfast Bk 0066 is a carbon black based pigment.

[0153] Testing with colored suspensions A comparison was made between the above colour suspension and a reference suspension in which an inorganic pigment (SikaColor® granules available from Sika USA) was used instead of the organic pigment, thereby colouring the colour suspension in a standard mortar.

[0154] It has been found that in comparison with a reference suspension based on inorganic SikaColor pigments, the suspension of the invention requires up to 10 times less product to reach the same color: for example, to obtain the same red mortar composition, 3% by weight of a suspension based on SikaColor was required, whereas only 0.3% by weight of the suspension of the invention was required.

[0155] Thus, the suspension of the present invention is highly effective.

[0156] Method and apparatus for additive manufacturing FIG. 1 illustrates generally an exemplary system 1 for producing three-dimensional colored objects from a curable binder composition using an additive manufacturing process.

[0157] The system 1 comprises a moving device 2 having a movable arm 2.1. A print head 3 is mounted at the free end of the arm 2.1 and can be moved in all three spatial dimensions by the arm 2.1. Thus, the print head 3 can be moved to any position within the working area of ​​the moving device 2.

[0158] Internally, the printhead 3 has a tubular passage 3.1 that runs from the end face facing the arm 2.1 (top in FIG. 1) to the opposite free end face. The tubular passage is configured to transport a curable binder composition. At the free end, the passage 3.1 opens into an outlet nozzle 4.

[0159] The print head 3 comprises a first inlet device 5, consisting of a feed device, for example a pump, and an inlet nozzle opening into the passage 3.1. Through the inlet nozzle of the inlet device 5, additives, such as for example rheological aids, surfactants and / or accelerators, can be added, if necessary, to the curable binder composition flowing through the passage 3.1.

[0160] Furthermore, the print head 3 comprises four additional inlet devices 7.1, 7.2, 7.3, 7.4, each comprising a separate reservoir containing a colour suspension (e.g. as described above), a supply device and an inlet nozzle opening into the passage 3.1. The inlet devices 7.1, 7.2, 7.3, 7.4 are configured to add the colour suspension contained in the reservoir individually to the passage 3.1 or to the curable binder composition, respectively.

[0161] Furthermore, inside the printhead 3, in the passage 3.1 downstream of the inlet device, a dynamic mixer 6 is arranged which further mixes the curable binder composition, the additives and the colour suspension.

[0162] The system 1 for applying a hardenable building material also has, on the input side, a supply device 9 corresponding to three containers 11.1, 11.2, 11.3 and an additive reservoir 11.4. The three containers 11.1, 11.2, 11.3 each contain one component of the hardenable building material. The first component present in the first container 11.1 is, for example, a dry mineral binder composition such as cement or dry mortar. The second component present in the second container 11.2 consists, for example, of water. The third component present in the third reservoir 11.3 is, for example, a superplasticizer in the form of a polycarboxylate ether. In the additive reservoir 11.4, a rheological assistant is present, for example in the form of modified cellulose and / or microbial polysaccharides.

[0163] On the output side, the feed device 9 has three independent outlets, each connected to one of the three inlets 10.1, 10.2, 10.3 of the mixer 10. The feed device 9 also has individually controllable metering devices (not shown in FIG. 1 ) by means of which the individual components in the individual containers 11.1, 11.2, 11.3 can be individually metered and fed to the mixer 10.

[0164] A further outlet of the feed device is connected to an inlet nozzle 5 (not shown in FIG. 1) by means of which additive can be fed from an additive reservoir 11.4 via a further metering device of the feed device 9 into the inlet nozzle 5.

[0165] The mixing device 10 is designed as a dynamic mixer and further comprises an integrated conveying device in the form of a screw conveyor. In the mixing device, the individually metered components are mixed and fed into a flexible line 12 attached to the outlet side of the mixing device 10. During operation, mixing and conveying of the curable binder composition can take place continuously.

[0166] The curable binder composition is delivered to the printhead 3 via a flexible line 12 which opens into the tubular passage 3.1 and can be applied continuously through an outlet nozzle 4.

[0167] Also part of the system 1 is a measurement unit 13 integrated into the supply line 12 in the area between the mixing device 10 and the print head 3. The measurement unit includes, for example, an ultrasonic transducer designed to determine the flow properties of the curable material.

[0168] A central control unit 14 of the system 1 includes a processor, a memory unit, and a number of interfaces for receiving data and for controlling the individual components of the system 1 .

[0169] In this regard, the mixing device 10 is connected to the control unit 14 via a first control line 15a, while the feeding device 9 is connected to the control unit 14 via a second control line 15b. As a result, the individual components in the containers 11.1, 11.2, 11.3 are metered into the mixing device 10 via the central control unit according to a predefined recipe stored in the control unit and conveyed to the flexible line 12 at an adjustable conveying speed.

[0170] The inlet devices 5, 7.1, 7.2, 7.3, 7.4 are similarly connected to the control unit 14 via separate control lines 15d, 15e, 15f, 15g, 15h, respectively, and can be controlled or monitored by the control unit 14.

[0171] The movement device 2 is also connected to the control unit 14 via another control line 15i. This means that the movement of the print head 3 can be controlled via the control unit 14.

[0172] Similarly, the measurement unit 13 is connected to the control unit 14 by a control line 15j so as to be able to transmit to the control unit 14 data characterising the flow properties recorded in the measurement unit.

[0173] Furthermore, the control unit 14 is connected to a selector unit 8 which has a user interface allowing the selection of a target colour.

[0174] The control unit 14 may, for example, (i) the addition rate of the three components of the hardenable building material by the feeding device 9 is controlled in response to the flow properties of the hardenable building material in the flexible line, determined via the measuring unit 13; (ii) the rate of addition of the additive via the inlet device 5 is controlled in response to the flow properties of the hardenable building material determined via the measuring unit 13 and the structure of the object to be produced; (iii) the position of the movement device 2, and thus the print head 3, is controlled as a function of a model of the production object stored in a data memory of the control unit 14; (iv) the memory unit contains a pre-established relationship between the proportion of the color suspension in the hardenable binder composition and the coordinates within a color model, in particular the HSV model, that represent a particular target color; (v) The rate and / or proportion of addition of the colour suspension via the inlet devices 7.1, 7.2, 7.3, 7.4 is individually controlled according to the target colour preselected in the selector unit 8 It is structured as follows.

[0175] FIG. 2 illustrates generally another exemplary system 1 for producing three-dimensional colored objects from a curable binder composition using an additive manufacturing process.

[0176] The system 1' is of essentially the same design as the system 1 of figure 1. However, the system 1' comprises a manifold M instead of the inlet device 5 and the four further intake devices 7.1, 7.2, 7.3, 7.4.

[0177] Specifically, manifold M has five separate inlet ports I1, I2, I3, I4, I5 leading to a common outlet port O having a single inlet nozzle opening into passage 3.1.

[0178] Each of the four first inlet ports I1, I2, I3, I4 is connected to an inlet device S1, S2, S3, S4, which comprises a separate reservoir with a colour suspension (e.g. as described above) and a supply device, e.g. a pump, configured to add the colour suspension contained in the reservoir to the respective inlet port I1, I2, I3, I4 individually.

[0179] The fifth inlet port I5 is connected to a further inlet device S5, which is equipped with a supply device, such as a pump, etc. The inlet device S5 is configured to supply an additive, such as a rheological aid, to the inlet port I5.

[0180] In operation, the color suspension supplied through inlet ports I1, I2, I3, I4 and the additive supplied through inlet port I5 are combined and mixed in manifold M. The mixture thus obtained is then fed into passage 3.1 through a common outlet O and a single inlet nozzle.

[0181] The inlet devices S1, S2, S3, S4, S5 are similarly connected to the control unit 14 via separate control lines 15c, 15d, 15e, 15f, 15g, 15h respectively and may be controlled or monitored by the control unit 14.

[0182] Similar to system 1, the control unit 14 of system 1′ may, for example, (i) the addition rate of the three components of the hardenable building material by the feeding device 9 is controlled in response to the flow properties of the hardenable building material in the flexible line, determined via the measuring unit 13; (ii) the rate of addition of the additive via the inlet device S5 is controlled depending on the flow properties of the hardenable building material determined via the measuring unit 13 and the structure of the object to be produced; (iii) the position of the movement device 2, and thus the print head 3, is controlled as a function of a model of the production object stored in a data memory of the control unit 14; (iv) the memory unit contains a pre-established relationship between the proportion of the color suspension in the hardenable binder composition and the coordinates within a color model, in particular the HSV model, that represent a particular target color; (v) The rate and / or proportion of addition of the colour suspension via the inlet devices S1, S2, S3, S4 is individually controlled according to the target colour preselected in the selector unit 8 It is structured as follows.

[0183] Coloring of mortar compositions In the cementitious mortar composition optimized for 3D printing, the relationship between the pigment proportions of each of the color suspensions (B, Y, R, and Bk; see Table 1) relative to the weight of the mortar and the color parameters of the HSV color model was established. The cementitious mortar composition used was similar to the composition described in WO 2020 / 187633 A1, page 39, line 9 to page 40, line 8.

[0184] Figures 3a-c show the corresponding graphs (the proportion of powder corresponds to the proportion of pigment). It is observed that the colored mortar compositions have a constant H (=hue) value, independent of the amount of pigment in the composition: red is 350°, blue is 200°, yellow is 50°. This observation is in agreement with the definition of the color space, where H indicates the hue of the pigment.

[0185] The coordinate S, i.e. the saturation value according to the HSV model, increases in different intensities for each color. Red and yellow have a similar progression of S, but blue is stronger, reaching almost 100% at the same concentration. On the other hand, the black pigment does not seem to affect saturation much.

[0186] The curves have been empirically fitted, allowing the desired saturation values ​​to be easily calculated from the densities.

[0187] Finally, for the coordinate V, i.e. the luminance value according to the HSV model, red and yellow also show a similar behavior, whereby V is essentially constant around a value of 80, regardless of the concentration. On the other hand, the addition of blue and black reduces V, but not to the same extent. In fact, black has a greater effect on V than blue. The progressions of both were fitted experimentally, using a linear function for blue and a logarithmic function for black.

[0188] The color combinations were characterized by the ratio of two different colored suspensions. Three mixtures were analyzed: red-yellow, red-blue, and yellow-blue. The first observation was that by changing the ratio of the two colored suspensions new shades or H values ​​were obtained, and the saturation increased with the total concentration of pigments. The obtained H values ​​were always between the corresponding H values ​​of the two primary colors. For example, in Figure 4, for red-blue mixtures, depending on the mixing ratio of the amount of red and blue pigments, all H values ​​increased within the H red =350° to H blue = 200°.

[0189] In a mixture, the S value is the total pigment concentration (C tot ), this progression can be fitted, for example, with a polynomial function, as shown in FIG. 5 for the red-yellow combination.

[0190] Finally, the V value depends on the nature of the mixture. For red-yellow, it was generally constant around 83%, as shown in Figure 6. In contrast, the V value decreases linearly for the other mixtures, depending on the total pigment concentration in the red-blue and yellow-blue mixtures (see Figures 6 and 7). Each of these progressions can be fitted experimentally to easily calculate the V coordinate.

[0191] Apparently, by combining the three primary color suspensions B, Y, and R, a wide color spectrum can be obtained (see Table 1).

[0192] Upon addition of the black pigment suspension Bk, the V values ​​of all colors and mixtures decrease significantly following a logarithmic trend, as shown in FIG.

[0193] Therefore, to obtain a mineral binder composition of a desired target color (eg, as specified in the HSV color model), it is possible to calculate the concentration of each color suspension based on the relationships described above.

[0194] For mortar compositions of different compositions, the relationship between the proportions of each pigment in the color suspension (B, Y, R, and Bk) and the color parameters of the HSV color model is preferably re-established in order to achieve the most accurate color fidelity possible.

[0195] Calculating Concentration Special software has been developed to calculate the concentration of each color suspension to obtain a mineral binder composition with a desired target color. The software may be implemented in the control unit 14 or in an external computing device. The target color may be set in a selector unit 8 having a user interface. An exemplary user interface is shown in FIG. 9. The software allows the user to input the desired target color and then determines the concentration of the color suspension based on a pre-determined relationship between the concentration of the color suspension and the color coordinates H, S, and V. Alternatively, the target color may be specified in the RAL system, whereby the RAL number is converted by the software into the corresponding HSV coordinates.

[0196] The calculations are divided into primary colors (ie, colors corresponding to the primary color suspensions B, Y, and R) and mixed colors (ie, mixtures of these primary colors).

[0197] For primary colors, the H value is a constant specific to each colored suspension, so only the required S value is used to estimate the concentration from the experimental fit.

[0198] For mixed colors, it is more difficult, since the calculation is different for each mixture. Thereby, the desired H value of the required target color can be obtained by controlling the ratio of the two color suspensions. This ratio can be calculated by solving the corresponding simultaneous equations (see, for example, Figure 4). Similarly, the S value of the required target color can be obtained by controlling the total concentration by solving the corresponding simultaneous equations (see, for example, Figure 5). From there, each concentration can be easily calculated. Finally, V is calculated from the obtained concentrations and compared with the V value of the required target color to estimate the amount of black to be added.

[0199] For example, if the user requests a brown with HSV=(30°, 50%, 60%), the software knows that H=30° can be obtained from a yellow-red mixture with a ratio of yellow / red = approximately 7.34, and for this same mixture, a total concentration of 0.33% will reach a saturation S of 50%. Then, based on the ratio and total concentration of yellow and red, the individual concentrations of the red and yellow pigments are calculated as C yellow = 0.29% and C red = 0.04%. Finally, since V = 83% for this mixture, to obtain the target of 60%, V needs to be reduced by 23%, which corresponds to a concentration of 0.025% black pigment.

[0200] Printing Test Tests using the above-mentioned device and method have shown that the colored suspension of the present invention is very suitable for coloring three-dimensional structures in additive manufacturing. Since the required concentration is quite low, additional water introduced into the hardening mineral binder composition in the print head does not significantly affect the rheology and hardening behavior of the composition. It is therefore possible to print three-dimensional structures of various colors without the need to adjust the printing process or the hardening mineral binder composition.

[0201] It will be understood by those skilled in the art that the present invention may be embodied in other specific forms without departing from its spirit or essential characteristics, and the embodiment or embodiments disclosed herein are therefore considered in all respects to be illustrative and not restrictive.

Claims

1. 1. A method for producing a three-dimensional object by means of an additive manufacturing process from a curable binder composition, comprising adding at least one, such as at least two, in particular at least three, in particular at least four, coloring suspensions comprising color pigments and a solvent, in particular water, to said curable binder composition prior to application of said curable binder composition in order to color said curable binder composition.

2. 2. The method according to claim 1, wherein the hardenable binder composition is prepared in an advanced hardening state by mixing the components of the mineral binder composition, in particular in a mixing unit, before adding the at least one colour suspension.

3. 3. The method according to claim 1 or 2, wherein at least two, in particular at least three, in particular at least four colour suspensions are added simultaneously and / or sequentially to the curable binder composition, each of said at least two colour suspensions comprising a different colour pigment.

4. The method according to any one of claims 1 to 3, wherein all of said at least one colour suspension are premixed before introducing said mixed colour suspensions into said hardenable binder composition.

5. 5. The method according to claim 1, wherein the proportion of the at least one colour suspension, in particular the proportion of each of the at least two colour suspensions, added to the curable binder composition is controlled by a control unit, the control unit being configured to control the proportion of the at least one colour suspension to obtain a coloured curable binder composition having a preselected target colour.

6. 6. The method according to claim 5, wherein the proportion of the at least one color suspension is determined based on a pre-established relationship between the proportion of the at least one color suspension in the curable binder composition and coordinates in a color model, in particular the HSV model, representing the target color.

7. 7. The method according to any one of claims 1 to 6, wherein the curable binder composition is applied to form the three-dimensional structure by means of a printhead movable in at least one spatial direction, in particular the curable binder composition is applied layer by layer.

8. 8. The method of claim 7, wherein the at least one color suspension is added to the mineral binder composition in the print head and / or in a supply line upstream of the print head.

9. a) measuring the color of the pigmented curable binder composition with a color measuring device before and / or during application to obtain the actual color of the pigmented curable binder composition; b) determining in said control unit a color deviation between said measured actual color and said preselected target color; c) adjusting the proportions of the at least one color suspension, in particular the respective proportions of the at least two color suspensions, taking into account said color deviations in order to correct said color deviations, in particular so that the actual color of the colored curable binder composition is adjusted to correspond to the selected target color; The method according to any one of claims 6 to 8, wherein steps a) to c) are repeated continuously, at least for a selected period of time, in particular permanently, during the production of the three-dimensional object.

10. 10. A method according to any one of claims 1 to 9 for producing a three-dimensional object having at least one desired target color, in particular two or more target colors, wherein the three-dimensional object is produced from a curable binder composition by means of an additive manufacturing apparatus, the method comprising the steps of: a) receiving a target color in a control unit of the additive manufacturing device, in particular from a user interface and / or a machine interface; b) determining, using the control unit of the additive manufacturing apparatus, the proportion of at least one color suspension, in particular the proportion of at least two color suspensions, in the curable binder composition necessary to obtain a colored curable binder composition having the desired target color, said determining being based on a predefined color model stored in a memory unit of the additive manufacturing apparatus; c) adding said at least one color suspension, in particular said at least two color suspensions, to said hardenable binder composition in said proportion determined in step b) by means of one or more inlet devices, in particular one or more actuators, controlled by said control unit; d) applying said pigmented curable binder composition by means of a printhead to form said three-dimensional object; wherein steps c) to d), in particular steps a) to d), are repeated continuously during the production of said three-dimensional object.

11. 11. The method according to claim 10, wherein in step b) the determination of the proportion of the at least one color suspension, in particular the proportions of the at least two color suspensions, in the curable binder composition necessary to obtain a colored curable binder composition having the desired target color is based on a pre-established relationship between the proportion of the at least one color suspension in the curable binder composition and coordinates in a color model, in particular the HSV model, representing the target color.

12. 12. The method according to claim 10 or 11, wherein at least two different target colors are received by the control unit, in particular one after the other in time, for producing a three-dimensional object having sections colored in at least two different colors.

13. 13. The method according to any one of claims 10 to 12, wherein the target color received by the control unit in step a) is determined based on a data model of the three-dimensional object describing the three-dimensional object in terms of structure and color.

14. a) measuring the color of the pigmented curable binder composition with a color measuring device before and / or during application to obtain the actual color of the pigmented curable binder composition; b) determining in said control unit a color deviation between said measured actual color and said preselected target color; c) adjusting the proportions of the at least one color suspension, in particular the respective proportions of the at least two color suspensions, taking into account said color deviations in order to correct said color deviations, in particular so that the actual color of the colored curable binder composition is adjusted to correspond to the selected target color; The method according to any one of claims 10 to 13, wherein steps a) to c) are repeated continuously, at least for a selected period of time, in particular permanently, during the production of the three-dimensional object.

15. 15. The method according to any one of claims 1 to 14, wherein additives for controlling the chemical and / or physical properties of the curable binder composition in the curing process are added to the curing binder composition in the printhead, in a supply line upstream of the printhead and / or together with the colour suspension, said additives being selected from accelerators, retarders, rheological aids, surfactants and / or superplasticisers.

16. An additive manufacturing apparatus having means adapted to carry out the steps of the method according to any one of the preceding claims.

17. A computer program comprising instructions for causing an apparatus according to claim 16 to carry out the method according to any one of claims 1 to 15.

18. a) 5 to 70% by weight, preferably 25 to 70% by weight, of a color pigment, chosen in particular from organic pigments and carbon black; b) 25 to 70% by weight of a solvent, in particular water; and c) optionally, 0.001 to 30% by weight, preferably 0.001 to 5% by weight, of a defoaming agent; and all percentages are given relative to the total weight of the colour suspension.

19. 19. A liquid coloured suspension according to claim 18, wherein said coloured pigment is selected from organic pigments and carbon black, preferably said organic pigment is selected from red, blue, green, magenta and / or yellow pigments.

20. 20. A liquid coloured suspension according to claim 18 or 19, wherein the coloured pigment is a mixture of organic and inorganic pigments.

21. 21. A liquid coloured suspension according to any one of claims 18 to 20, wherein the organic pigment is a material selected from phthalocyanine dyes, quinophthalone dyes, naphthol dyes, diketopyrrolopyrrole dyes, quinacridone dyes, dioxazine dyes, arylide dyes and / or pyrazoloquinazolone dyes.

22. 22. A liquid colour suspension according to any one of claims 18 to 21, wherein the suspension comprises less than 1% by weight, in particular less than 0.1% by weight, preferably less than 0.01% by weight, of inorganic pigments other than carbon black, in particular oxide-based pigments, relative to the total weight of the colour suspension.

23. 23. A liquid colour suspension according to any one of claims 18 to 22, wherein the defoaming agent is selected from water-insoluble compounds.

24. The defoaming agent is selected from the group consisting of kerosene, liquid paraffin, animal oil, vegetable oil, sesame oil, castor oil, alkylene oxide adducts thereof, oleic acid, stearic acid and alkylene oxide adducts thereof, diethylene glycol laurate, glycerin monoricinoleate, alkenylsuccinic acid derivatives, sorbitol monolaurate, sorbitol trioleate, polyoxyethylene monolaurate, polyoxyethylene sorbitol monolaurate, natural waxes, linear or branched fatty alcohols and alkoxylated versions thereof.

24. The liquid colour suspension according to any one of claims 18 to 23, wherein the polyoxyethylene terephthalate derivatives are selected from octyl alcohol, hexadecyl alcohol, acetylenic alcohol, glycols, polyoxyalkylene glycols, polyoxyalkylene amides, polyamine acrylates, tributyl phosphate, sodium octyl phosphate; aluminium stearate, calcium oleate, silicone oils, silicone pastes, silicone emulsions, organomodified polysiloxanes, fluorosilicone oils; and polyoxyethylene polyoxypropylene adducts.

25. A kit comprising at least two, in particular at least three, in particular at least four colour suspensions according to any one of claims 18 to 24, wherein each of said at least two colour suspensions comprises a different colour pigment.

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