Method for making an object comprising a refractory mold substrate and a resol into a layered structure, a three-dimensional object manufactured using the method, and a binder for an object having a three-dimensional structure

Abstract

The object of the present disclosure is a method for layering an object comprising a refractory mold base and a resole resin as binder having, in addition to phenol, ortho- and / or para-substituted phenols as monomeric constituents, a three-dimensional object produced by this method, and a binder for three-dimensionally constructed objects, in particular molds and cores for metal casting.

Description

Technical Field

[0001] The present disclosure relates to a method of forming an object comprising a refractory mold substrate and a resol resin as a binder having ortho-substituted and / or para-substituted phenols as monomeric components into a layered structure, a three-dimensional object produced by the method, and a three-dimensionally constructed object, particularly a mold for metal casting and a binder for cores.

Background Art

[0002] Various methods for manufacturing three-dimensional objects by a layered structure are known under the name of rapid prototyping. The advantage of the method is that it provides an option for manufacturing complex objects consisting of one part including undercuts and hollow spaces. Using conventional methods, the object needs to be joined from several separately manufactured parts. A further advantage is that the method is highly automated and the object can be manufactured directly from CAD data in a computer-controlled manner without casting tools.

[0003] Various designs are known for methods of manufacturing a mold body in layers. According to the design, suitable mold substrates, for example, free grains of quartz sand to form a three-dimensional object, are applied in layers and a hardening agent is selectively applied layer by layer by providing a binder, or the binder itself is selectively applied to each layer, for example, in each case, by a thin spray or a bundle of thin sprays, in a manner similar to the operating mode of an inkjet printer. Hardening can be carried out in the layer, for example, when a hardening agent corresponding to the mold substrate is provided, or when all the layers required for manufacturing the three-dimensional object are completed. According to the design, the hardening reaction can be initiated thermally or, for example, by flooding the entire component with a gaseous hardening agent.

[0004] Patent Document 1 discloses a method of making an object containing a refractory mold substrate and a resol into a layered structure. The alkaline resol resin is cured by an ester during this method, is applied in layers together with the mold substrate, and is selectively applied via a print head.

[0005] Resols or resol resins are each phenolic resins and belong to the classification of phenol-formaldehyde resins. Resols or resol resins are produced by the condensation of a hydroxyaromatic compound and an aldehyde, particularly formaldehyde, in the presence of an alkaline catalyst. For the production of an alkaline resol resin, formaldehyde and phenol are usually used as monomers and are subjected to a polycondensation reaction. Since the amount of formaldehyde is used in a mostly (e.g., up to 2.5:1) superstoichiometric manner, ether groups are further formed in addition to methyl groups for linking purposes.

[0006] It is known to those skilled in the art that in addition to phenol, alkylphenols, such as xylenol or cresol, can be further used as components of the monomers for the production of resols. However, resols in the form of an aqueous alkaline solution as a binder for the production of casting molds and cores have an adverse effect on price and odor and are therefore usually not used together with cresol as an additional monomer component.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Patent Document 6

[0008] When using phenol, it has been shown that there is a problem that the viscosity of the alkaline resol resin increases strongly over time, resulting in a decrease in the printability of the binder over time. In particular, due to the increase in viscosity, there is a decrease in the flow rate of the resol resin passing through the print head up to the failure point of the print head. Furthermore, there is a problem that the reactivity of the resol resin increases over time. The increase in reactivity results in a decrease in the level of stability of the bonded casting mold. The increase in reactivity is particularly manifested in the shortening of the gelation time. The increase in reactivity and the increase in viscosity have an adverse effect on the uniformity of the printing process and reduce the stability of the resol resin over time during the printing process.

[0009] An object of the present disclosure is to further provide a storage-stable resol resin, in which the viscosity of the resol resin is further stable over time and the decrease in the gelation time is further reduced, thereby ensuring the long-term printability of a binder made of the resol resin. The binder can further achieve sufficient stability of the bonded casting mold. [Means for Solving the Problems]

[0010] The object of the present invention is to provide a method for forming an object having the features of claim 1 into a layered structure or a binder as described in claim 2 3 to solve the problem, and further effective development forms are the subject matter of the dependent claims or will be described hereinafter. Use The method for forming an object into a layered structure is as follows:

[0011] (a) collecting one or more refractory mold substrates and one or more esters to obtain a mixture of mold materials impregnated with esters; (b) applying a thin layer having a layer thickness of 1 to 6 grains, preferably 1 to 5 grains, particularly preferably 1 to 3 grains, to the mixture of mold materials impregnated with esters; (c) brushing a selected area of the thin layer with a binder containing an alkaline resol resin for curing the area; (d) repeating steps (b) and (c) a plurality of times for finishing at least a partially cured three-dimensional object. The alkaline resol resin can be obtained by the conversion of formaldehyde with at least phenol and at least ortho-substituted and / or para-substituted phenols. The substituents (in each case) are aliphatic, branched or unbranched, saturated or unsaturated hydrocarbon radicals having 1 to 15 carbon atoms, particularly 1 to 4 carbon atoms, and the molar ratio of at least ortho-substituted and / or para-substituted phenol (A) to phenol (B) is 1:1.5 to 1:15 (A:B). The mold and the core for metal casting are three-dimensionally constructed using a binder containing one or more alkaline resol resins (in particular consisting of the resol resin), at least

[0012] a. phenol, and b. phenol having at least one substituent, preferably one substituent, at the ortho and / or para positions It can be obtained by the conversion, and the substituents are, in each case (optionally different), aliphatic, branched or unbranched, or saturated or unsaturated hydrocarbon radicals having 1 to 15 carbon atoms, At one or two of the remaining positions (2, 4, 6, or ortho / para, respectively), there are bonds to further structural units of resorcinol that are not bonds to hydrogen, c. Formaldehyde It contains.

[0013] The polymer is formed by connecting the nuclear part of phenol containing at least phenol and substituted phenols (ortho-substituted and / or para-substituted phenols) via methylene groups and / or ether bridges (-CH2-OOOA-).

Mode for Carrying Out the Invention

[0014] As the refractory mold base material (hereinafter may be abbreviated as mold base material) for the production of a casting mold, conventional and known materials can be used. Suitable ones include, for example, quartz sand, zircon sand, or chromite sand, cordierite, vermiculite, bauxite, chamotte, and synthetic mold base materials based on, for example, mullite (sintered mullite). In particular, quartz sand exceeding 50 weight percent based on the refractory mold base material is suitable. The mold base material is understood to be a substance with a high melting point (melting temperature). The melting point of the refractory mold base material is preferably above 600°C, preferably above 900°C, particularly preferably above 1200°C, and particularly preferably above 1500°C. The refractory mold base material has a free-flowing state.

[0015] The mold base material preferably occupies more than 80 weight percent, particularly more than 90 weight percent, and particularly preferably more than 95 weight percent of the mold material mixture.

[0016] The average diameter of the refractory mold base material is usually 80 μm to 600 μm, preferably 100 μm to 400 μm, and particularly preferably 120 μm to 300 μm. The particle size can be determined, for example, by sieving according to DIN ISO3310. A particle shape in which the ratio of the maximum length range to the minimum length range (perpendicular to each other and in each case with respect to all directions in space) is 1:1 to 1:5 or 1:1 to 1:3, that is, for example, not fibrous, is particularly preferred.

[0017] Special chromite sand is particularly preferred and is sold under the name "Spherichrome" by Oregon Resources (ORC). In Europe, Spherichrome is sold by Possehl Erzkontor in Lübeck. Spherichrom is different from the currently known South African chromite ore in terms of particle shape. In contrast to the latter, most of the particles of Spherichrome are circular. According to a preferred embodiment, Spherichrom does not have to occupy 100 weight percent of the mold base material, and mixtures with other mold base materials, particularly quartz sand, are further possible. The respective distortion of the casting mold is determined by the mixing ratio. However, the latter generally should contain 20 weight percent or more, preferably 40 weight percent or more, and particularly preferably 60 weight percent or more of Spherichrom when using quartz sand. Apart from the above, the particle shape of the mold base material of Spherichrom has a ratio (average value) of the maximum length range to the minimum length range (perpendicular to each other and in each case with respect to all directions in space) of particularly 1:1 to 1:3, and particularly preferably 1:1 to 1:3.

[0018] The binder consists of an alkaline resol resin. The resol resin according to the present disclosure is produced by the condensation of at least phenol, ortho-substituted phenol, or para-substituted phenol, and formaldehyde in the presence of an alkaline catalyst.

[0019] According to one embodiment of the present disclosure, the resol exists in the form of an aqueous alkali solution, preferably having a solid content of 20 to 75 weight percent, preferably having a pH exceeding 11, and particularly preferably exceeding 12 (measured at 25 °C).

[0020] The resol resin is effectively used at a concentration of 0.8 weight percent to 8 weight percent, preferably 1 to 7 weight percent, and particularly preferably 1.5 to 5 weight percent, respectively, based on the mold substrate. As described above, the concentration of the binder can be varied in the casting mold. In the case of a thicker partial region of the mold, the ratio of the binder can actually be smaller than described above, but in thin and complex parts, the content of the binder can exceed the above-mentioned limit values.

[0021] The resol according to the present disclosure is an aromatic compound that is bonded to each other via a methylene group (-CH2-) group and / or an ether bridge (particularly -CH2-OOOA-), and in each case has one or more -OH groups (hydroxyaromatic compound).

[0022] The ortho-substituted and / or para-substituted phenol is understood to be a compound substituted with one or more aliphatic, branched or unbranched, saturated or unsaturated hydrocarbon radicals having 1 to 15 carbon atoms, particularly 1 to 4 carbon atoms, based on the phenol at the ortho position and / or para position (2, 4, 6), preferably based on the ortho position, and having a maximum of two free radicals / substituents. The aliphatic radical is preferably unbranched and saturated. Particularly preferably, the substituted phenol is orthocresol or paracresol, and more preferably orthocresol.

[0023] The hydrocarbon radicals of at least ortho-substituted and / or para-substituted phenols are in particular one or several methyl groups, and the ortho-substituted and / or para-substituted phenols are in particular selected from the group consisting of, for example, o-cresol, p-cresol, 2,4-xylenol, 2,6-xylenol, 2,3-xylenol, 2,5-xylenol, 3,4-xylenol, and mixtures thereof, in particular those containing o-cresol. The ortho-substituted and / or para-substituted phenols can furthermore be meta-substituted.

[0024] In particular, in the case of resol resins, more than 90 mol% of the hydroxyaromatic compounds, in particular more than 95 mol% of the hydroxyaromatic compounds, or all of the hydroxyaromatic compounds are phenol and ortho-substituted and / or para-substituted phenols respectively, or are based on their monomeric components.

[0025] Formaldehyde can be used in various forms, for example in the form of a formalin solution (aqueous solution of formaldehyde) or paraformaldehyde. Substantially, only formaldehyde is preferably used as the aldehyde.

[0026] Surprisingly, it has been shown that when the resol is produced from at least phenol and ortho-substituted or para-substituted phenol, the storage or viscosity and reaction stability of the alkaline resol resin can be significantly increased. As described above, a specific ratio of phenol to ortho-substituted or para-substituted phenol is necessary on the one hand to achieve a sufficient level of stability of the casting mold bonded by the binder, and on the other hand to ensure an increase in the storage stability of the binder.

[0027] The molar ratio of the ortho-substituted and / or para-substituted phenols (total) (A) to phenol (B) in the alkaline resol resin is from 1:1.5 (A:B) to 1:15, preferably from 1:2 to 1:10, and particularly preferably from 1:4 to 1:6.

[0028] The molar ratio of the hydroxyaromatic compound to formaldehyde can be varied between 1:1 and 1:3, preferably between 1:1.2 and 1:2.6, and particularly preferably between 1:1.3 and 1:2.5.

[0029] The hydroxyaromatic compound is preferably essentially exclusively formed by phenol, ortho-substituted phenol, para-substituted phenol, and ortho- and para-substituted phenols, i.e., ortho-substituted and / or para-substituted phenols.

[0030] The above-mentioned resol is suitable as part of an alkaline resol resin, and the nearby hydroxyaromatic compounds are each linked to the ortho position and / or para position via a methylene bridge and / or an ether bridge (with respect to the introduced phenolic / aromatic hydroxyl group), i.e., a plurality of linkages occur at the para position and / or ortho position.

[0031] Organic bases such as amines or ammonium compounds, and inorganic bases such as alkali metal hydroxides can be used as alkaline catalysts. Alkali metal hydroxides, particularly preferably sodium hydroxide and / or potassium hydroxide in the form of an aqueous solution, are preferably used. A mixture of alkaline catalysts can likewise be used.

[0032] The molar ratio of the hydroxyaromatic compound (e.g., phenol, similarly introduced) to hydroxide ions in the binder system is preferably 1:0.4 to 1:1.2, and preferably 1:0.5 to 1:1.0.

[0033] The total amount of the base does not need to be added in advance at the start of the condensation, and usually, by adding in two or several sub-steps, a part can be added only at the end of the manufacturing process.

[0034] The content of compounds with a molecular weight exceeding 5000 daltons (g / mol) in the resol resin is preferably at most 3% by weight, and particularly preferably at most 1% by weight.

[0035] The average molecular weight (weight average) of the resol resin is particularly less than 1500 Daltons (g / mol), preferably less than 1400 Daltons (g / mol), and particularly preferably less than 1300 Daltons (g / mol).

[0036] The polydispersity D = Mw (weight average) / Mn (number average) of the resol resin is particularly 1.1 - 4, preferably 1.2 - 3.5, and particularly preferably 1.5 - 3.

[0037] The specific molecular weight was determined by gel permeation chromatography. For calibration, the above - mentioned molecular weight is equivalent to the molecular weight of pullulan - dextran. The following parameters were used.

[0038] Eluent: 0.5 M KOH Pre - column: PSS MCX, 5 μm, guard column, ID 8.0 mm x 50 mm Column: PSS MCX, 5 μm, 500 Å, ID 8.0 mm x 300 mm Pump: PSS SECurity 1260 HPLC pump Flow rate: 5 mL / min Injection system: PSS SECurity 1260 autosampler (20 μL) Sample concentration: 1 g / l Temperature: Injection volume 35 °C Detector: PSS SECurity 1260 UV / VIS (254 nm) Evaluation: PSS WinGC UniChrom version 8.31 Calibration: Molecular weight standard of pullulan - dextran (Mp 180 - 45900 Daltons)

[0039] The production of resol is disclosed, for example, in Patent Documents 2 and 3. Further, resol-based binders are described, for example, in Patent Documents 4 and 5. In the three patents, the resol is cured with the aid of an ester, and the curing is carried out by adding a liquid curing agent, such as lactone (Patent Document 4) or triacetin (Patent Document 5), respectively.

[0040] In addition to the components described above, the resol preferably contains moisture in an amount of 25% to 75% by weight based on the weight of the composition. On the one hand, the water can be derived from the aqueous solution used in the production of the binder (other than the water generated by polycondensation), while on the other hand, it can be added separately to the binder.

[0041] In addition to its function as a solvent, water is provided, for example, for the purpose of giving the binder a coating viscosity of, in particular, 3 mPas to 100 mPas, preferably 4 mPas to 50 mPas, and particularly preferably 5 mPas to 20 mPas. The viscosity is measured at 100 U / min and 25 °C using a Brookfield rotational viscometer, a small sample, and a spindle No. 21.

[0042] The binder can further contain additives, such as alcohols, glycols, surfactants, and silanes, up to about 50% by weight. With the aid of the above-mentioned additives, the wettability of the mold material can be increased, for example, by the binder on the mold material and its adhesion, and further, it can lead to an improvement in stability and an increase in moisture resistance. Regarding the above, adding silanes, such as γ-aminopropyltriethoxysilane or γ-glycidoxypropyltrimethoxysilane, in each case, in an amount of 0.1% to 1.5% by weight, preferably 0.2% to 1.3% by weight, and particularly preferably 0.2 to 1.0% by weight based on the weight of the composition has particularly effective effects.

[0043] Esters suitable for the curing of resol (hereinafter sometimes referred to as curing agents) are known to those skilled in the art from, for example, Patent Document 4, Patent Document 5, and Patent Document 6. In many cases, they include lactones, organic carbonates, and esters of monocarboxylic acids and polycarboxylic acids having 1 to 10 carbon atoms and monoalcohols and polyalcohols having 1 to 10 carbon atoms.

[0044] γ-Butyrolactone, propylene carbonate, ethylene glycol diacetate, monoacetin, diacetin, and triacetin, and dimethyl esters of succinic acid, glutaric acid, and adipic acid (including their mixtures known under the name DBE) are suitable examples of such esters or curing agents. Since the rate of alkaline hydrolysis of individual esters varies, the curing rate of resol proceeds at different rates depending on the ester used, which can also affect stability. By mixing two or several esters, the desired curing time can be varied over a wide range.

[0045] Options for improving the ester component are, based on the ester component, to add benzyl ester resin according to Patent Document 7, epoxy compound according to Patent Document 6, and / or polyphenol resin according to Patent Document 8, in each case in an amount of up to about 40 weight percent.

[0046] The ester component can further contain additional components up to about 50 weight percent, such as alcohols, glycols, surfactants, and silanes, which have already been mentioned among the binders.

[0047] The addition amount of the curing agent is usually 5 weight percent to 50 weight percent, preferably 5 weight percent to 40 weight percent, particularly preferably 5 weight percent to 30 weight percent, and in each case, based on the mold substrate, it is used at a concentration of 0.04 weight percent to 4.0 weight percent, preferably 0.05 weight percent to 3.5 weight percent, particularly preferably 0.08 weight percent to 2.5 weight percent.

[0048] According to a further embodiment, the mixture of mold materials can include some amorphous SiO2. In particular, it is particulate amorphous SiO2. Synthetically produced granular amorphous silicon dioxide is particularly suitable.

[0049] The amorphous SiO2 can be of the following types in particular. (a) Amorphous SiO2 obtained by precipitation from an alkali silicate solution (b) Amorphous SiO2 obtained by flame hydrolysis of SiCl4 (c) Amorphous SiO2 obtained by reducing quartz sand with coke or anthracite to silicon monoxide and then oxidizing it to SiO2 (d) Amorphous SiO2 obtained during the thermal decomposition of ZrSiO4 to SiO2 and ZrO2 (e) Amorphous SiO2 obtained by oxidation of metallic Si with an oxygen-containing gas (f) Amorphous SiO2 obtained by rapid cooling after melting of crystalline quartz

[0050] The above (c) includes the treatment when amorphous SiO2 is specifically produced as the main product and also when it is produced as a by-product such as the production of silicon or ferrosilicon.

[0051] Synthetically produced silica and naturally occurring silica can be used as amorphous SiO2. The latter is known, for example, from Patent Document 9, but generally contains a considerable crystalline portion and is classified as carcinogenic and thus not suitable.

[0052] The composition is understood not to be naturally occurring amorphous SiO2. In other words, the production of the composition involves intentionally carried out chemical reactions initiated by humans, such as the production of silica sol by an ion exchange process from an alkali silicate solution, precipitation from an alkali silicate solution, flame hydrolysis of silicon tetrachloride, reduction of quartz sand with coke in an electric arc furnace during the production of ferrosilicon and silicon. The amorphous SiO2 produced by the last two methods mentioned is called calcined SiO2.

[0053] The synthesized amorphous silicon dioxide is sometimes understood to be merely precipitated silica (CAS No. 112926-00-8) and flame hydrolysis-produced SiO2 (fumed silica, CAS No. 112945-52-5). However, the products generated during the production of ferrosilicon or silicon are each merely referred to as amorphous silicon dioxide (silica fume, microsilica, CAS No. 69012-64-12). For the purposes of the present disclosure, the products produced during the production of ferrosilicon or silicon are also understood to be further amorphous SiO2.

[0054] Precipitated silica and fumed silica, i.e., silicon dioxide produced by flame hydrolysis or an electric arc, are preferably used. Amorphous silicon dioxide produced by thermal decomposition of ZrSiO4 (described in Patent Document 10) and SiO2 produced by oxidizing metallic Si with an oxygen-containing gas (described in Patent Document 11) are particularly preferably used. Furthermore, quartz glass powder (mainly amorphous silicon dioxide) produced by melting and rapid recooling from crystalline quartz is suitable because the particles are spherical and not in the form of flakes (described in Patent Document 12).

[0055] The average primary particle size of particulate amorphous silicon dioxide can be 0.05 μm to 10 μm, particularly 0.1 μm to 5 μm, and particularly preferably 0.1 μm to 2 μm. The primary particle size can be determined, for example, with the aid of dynamic light scattering (e.g., Horiba LA950) and verified by an image of a scanning electron microscope (e.g., an SEM image by FEI's Nova NanoSEM 230).

[0056] With the aid of an SEM image, the details of the primary particle form with a size of up to 0.01 μm can be made more visible. The silicon dioxide sample is dispersed in distilled water for SEM measurement, then applied to an aluminum holder, and after applying a copper strip, the moisture is evaporated.

[0057] The specific surface area of the particulate amorphous silicon dioxide was further measured with the assistance of gas adsorption measurement (BET method) according to DIN66131. The specific surface area of the particulate amorphous SiO2 is 1 to 200 m 2 / g, particularly 1 to 50 m 2 / g, particularly preferably less than 17 m 2 / g, or further less than 15 m 2 / g. The product can be selectively mixed, for example, to specifically obtain a mixture having a specific particle size distribution.

[0058] The particulate amorphous SiO2 may contain various amounts of by-products. The following are described by way of example. · Carbon when reducing quartz sand with coke or anthracite · Iron oxide and / or silicon during the production of silicon or ferrosilicon · ZrO2 when thermally decomposing ZrSiO4 into ZrO2 or SiO2 Further by-products can be, for example, Al2O3, P2O5, HfO2, TiO2, CaO, Na2O, and K2O.

[0059] The amount of amorphous SiO2 added to the mixture of the mold material according to the present disclosure is, in each case, between 0.05 weight percent and 3 weight percent, preferably between 0.1 weight percent and 2.5 weight percent, particularly preferably between 0.1 weight percent and 2 weight percent, based on the mold substrate.

[0060] The addition of amorphous SiO2 to the mold substrate can be carried out as a suspension in water, or as a dry powder, in the form of an aqueous paste. Therefore, the latter is preferred. The particulate amorphous silicon dioxide is preferably used as a powder (including dust). The water content of the particulate amorphous silicon dioxide preferably used according to the present disclosure is less than 15 weight percent, particularly less than 5 weight percent, and particularly preferably less than 1 weight percent.

[0061] Amorphous SiO₂ is preferably in a particulate state. The particle size of the particulate amorphous silicon dioxide is preferably less than 300 μm, preferably less than 200 μm, particularly preferably less than 100 μm, and for example, has an average primary particle size (primary particle size determined by dynamic light scattering) of 0.05 μm to 10 μm.

[0062] When passing through a sieve with a mesh width of 125 μm (120 mesh), the sieve residue of the particulate amorphous SiO₂ is preferably 10 wt% or less, particularly preferably 5 wt% or less, and most preferably 2 wt% or less. Separately from the above, the sieve residue on a sieve with a mesh width of 63 μm is less than 10 wt%, preferably less than 8 wt%. The measurement of the sieve residue is carried out by the sieving method of the apparatus described in DIN66165 (Part 2), and a chain ring is further used as a sieve auxiliary material.

[0063] The order of addition of amorphous SiO₂ to the binder and / or the mold substrate is irrelevant. The addition can be carried out before or after the binder or simultaneously with the binder. Preferably, the addition of amorphous SiO₂ is carried out first, and then the addition of the binder is carried out.

[0064] Furthermore, additional common additives in the casting industry, such as ground wood fibers or mineral additives such as iron oxide, etc., can be selectively mixed with the mold substrate material, and the proportion is usually 0 wt% to 6 wt%, preferably 0 wt% to 5 wt%, particularly preferably 0 wt% to 4 wt% based on the mold substrate.

[0065] The present disclosure is a method for manufacturing a casting mold or a core (or generally an object), comprising (a) mixing a refractory mold substrate with an ester component, optionally an inorganic additive, and optionally an additional additive to obtain a mixture of mold materials; (b) applying a thin layer of the mixture of mold materials produced in step (a), having a layer thickness of 1 to about 6, preferably 1 to about 5, particularly preferably 1 to 3 grains, to a defined working surface. (c) A step of selectively brushing the thin layer of the mixture of the mold material at the positions specified by the CAD data with the binder, wherein the binder is at least partially cured by contact with the ester; (d) A step of repeating steps (b) and (c) a plurality of times until the mold is completed; (e1) A step of post-curing the at least partially cured mold in a furnace or by microwaves without previously removing the mixture of the unbonded mold material; and alternatively to step (e1), (e2) A step of removing the unbonded molding material mixture from the at least partially cured mold and including.

[0066] If stability is recognized, immediately following step (e1), the mixture of the unbonded mold material can be removed from the casting mold, and the casting mold can be supplied for further processing, such as preparation for metal casting.

[0067] Following step (e2), the casting mold can be post-cured by conventional means such as storage at an elevated temperature or by microwaves, if necessary. If stability is recognized, immediately the casting mold can be supplied for further processing, such as preparation for metal casting.

[0068] In both alternative examples, the mixture of the unbonded mold material can be supplied to a further casting mold after being removed from the at least partially cured casting mold.

[0069] The present disclosure will be described in more detail based on the following examples, but is not limited thereto.

[0070] Alkaline resol resins containing various contents of phenol and o-cresol were first manufactured. To more clearly emphasize the effects on stability, storage stability, and reactivity, the alkaline resol resins were set in the viscosity range of 40 to 60 mPas. For use in rapid prototyping (3D printing), the resol can be set to a working viscosity of 5 to 20 mPas with a suitable solvent, such as ethanol and water.

[0071] The influence of the proportion of o-cresol in the resol was later tested regarding stability based on a conventional test specimen, the so-called Georg-Fischer test bar.

[0072] The influence of the percentage of o-cresol in the resol on storage stability and reactivity was tested for storage cycles based on viscosity measurement and gelation time measurement.

[0073] [Test Example] 1. Manufacture of Resol Resin Resin 1 contained only phenol as a monomer component of the hydroxyaromatic compound.

[0074] Resins 2 to 6 contained 12 to 51 weight percent of o-cresol based on the total amount of phenol and o-cresol.

[0075] [Example 1] Resin 1 The formulation is as follows.

[0076]

Table 1

[0077] [Manufacturing Specifications] · Raw materials 1, 2, and 3 were loaded into the reflux condenser, thermometer, dropping funnel, and stirrer of the laboratory reactor. · The stirrer was started, and further stirring was carried out during the subsequent steps. · The preparation was heated to 75°C. · Raw material 4 was continuously loaded at 75 °C · The preparation was heated to 85 °C and held for 2 hours · The preparation was cooled to 70 °C and held for 1.5 hours · Raw material 5 was continuously loaded at a temperature below 30 °C · Raw material 6 was loaded and homogenized for 15 minutes

[0078] The resin was obtained as a clear solution and had a viscosity of 49 mPas (Brookfield rotational viscometer, small sample, spindle No. 21, 100 U / min and 25 °C).

[0079] [Example 2] Resin 2 The formulation is as follows.

[0080]

Table 2

[0081] [Manufacturing specifications] · Raw materials 1, 2, 3, and 4 were loaded into the reflux condenser, thermometer, dropping funnel, and stirrer of the laboratory reactor · The stirrer was started and further stirring was carried out during the next step · The preparation was heated to 75 °C · Raw material 5 was continuously loaded at 75 °C · The preparation was heated to 85 °C and held for 1.75 hours · The preparation was cooled to 70 °C and held for 2 hours · Raw material 6 was continuously loaded at a temperature below 30 °C · Raw material 7 was loaded and homogenized for 15 minutes

[0082] The resin was obtained as a clear solution and had a viscosity of 47 mPas (Brookfield rotational viscometer, small sample, spindle No. 21, 100 U / min and 25 °C).

[0083] [Example 3] Resin 3 The formulation is as follows.

[0084] [Table 3]

[0085] [Manufacturing Specifications] · Raw materials 1, 2, 3, and 4 were loaded into the reflux condenser, thermometer, dropping funnel, and stirrer of the laboratory reactor. · The stirrer was started and further stirring was carried out during the following steps. · The preparation was heated to 75 °C. · Raw material 5 was continuously loaded at 75 °C. · The preparation was heated to 85 °C and held for 1.5 hours. · The preparation was cooled to 70 °C and raw material 6 was continuously loaded. · The preparation was heated to 80 °C and held for 1 hour. · The preparation was cooled to a temperature below 30 °C. · Raw material 7 was loaded and homogenized for 15 minutes.

[0086] The resin was obtained as a clear solution and had a viscosity of 51 mPas (Brookfield rotational viscometer, small sample, spindle number 21, 100 U / min and 25 °C).

[0087] [Example 4] Resin 4 The formulation is as follows.

[0088] [Table 4]

[0089] [Manufacturing Specifications] · Raw materials 1, 2, 3, and 4 were loaded into the reflux condenser, thermometer, dropping funnel, and stirrer of the laboratory reactor. · The stirrer was started and further stirring was carried out during the following steps. · The preparation was heated to 75 °C. · Raw material 5 was continuously loaded at 75 °C. · The preparation was heated to 85 °C and held for 1.75 hours. · The preparation was cooled to 70 °C, and raw material 6 was continuously loaded. · The preparation was heated to 80 °C and held for 1.5 hours. · The preparation was cooled to a temperature below 30 °C. · Raw material 7 was loaded and homogenized for 15 minutes.

[0090] The resin was obtained as a transparent solution and had a viscosity of 51 mPas (Brookfield rotational viscometer, small sample, spindle No. 21, 100 U / min and 25 °C).

[0091] [Example 5] Resin 5 The formulation is as follows.

[0092]

Table 5

[0093] [Manufacturing specifications] · Raw materials 1, 2, 3, and 4 were loaded into the reflux condenser, thermometer, dropping funnel, and stirrer of the laboratory reactor. · The stirrer was started, and further stirring was carried out during the next step. · The preparation was heated to 75 °C. · Raw material 5 was continuously loaded at 75 °C. · The preparation was heated to 85 °C and held for 1.25 hours. · The preparation was cooled to 70 °C, and raw material 6 was continuously loaded. · The preparation was heated to 80 °C and held for 1 hour. · The preparation was cooled to a temperature below 30 °C. · Raw material 7 was loaded and homogenized for 15 minutes.

[0094] The resin was obtained as a transparent solution and had a viscosity of 51 mPas (Brookfield rotational viscometer, small sample, spindle No. 21, 100 U / min and 25 °C).

[0095] [Example 6] Resin 6 The formulation is as follows.

[0096]

Table 6

[0097] [Manufacturing Specifications] · Raw materials 1, 2, 3, and 4 were loaded into the reflux condenser, thermometer, dropping funnel, and stirrer of the laboratory reactor · The stirrer was started and further stirring was carried out during the next process · The preparation was heated to 75 °C · Raw material 5 was continuously loaded at 75 °C · The preparation was heated to 85 °C and held for 1.25 hours · The preparation was cooled to 70 °C and raw material 6 was continuously loaded · The preparation was heated to 80 °C and held for 0.5 hour · The preparation was cooled to a temperature below 30 °C · Raw material 7 was loaded and homogenized for 15 minutes

[0098] The resin was obtained as a clear solution and had a viscosity of 51 mPas (Brookfield rotational viscometer, small sample, spindle no. 21, 100 U / min and 25 °C).

[0099] 2. Generation of Test Specimens 2.1 Manufacture of Mixture of Molding Materials The molding materials were filled into the bowl of a stirrer (type Beba, L7). By stirring, the curing agent was added first, and then the binder was added, and in each case, it was intensively mixed with the molding base material for 1 minute.

[0100] The types of the molding base material, curing agent, and binder, as well as the addition amount of each, are listed in Table 7.

[0101]

Table 7

[0102] 2.2 Generation of test pieces Cube-shaped test bars (so-called Georg-Fischer bars) with dimensions of 172 mm × 22.36 mm × 22.36 mm were generated for testing the object. A part of the mixture generated according to 2.1 was introduced into the casting tool 12 having engraving, compressed by vibration on a vibration table (Morek, multi-saw type LUZ-2e), and removed from the casting tool after the release time ended.

[0103] The processing time (VZ), that is, the time during which the mixture can be compressed without problems, was visually determined. Since the mixture does not flow freely but is wound up in lumps, an excess of the processing time can be recognized. The processing times of the individual mixtures are specified in Table 8.

[0104] To determine the release time (AZ), that is, after the mixture had solidified to the extent that it could be removed from the casting tool, the second part of each mixture was manually filled into a round shape with a height of 100 mm and a diameter of 100 mm and compressed by a pressing plate.

[0105] Subsequently, the surface hardness of the compressed mixture was tested at regular intervals using the green hardness "B" scale of a surface hardness tester by Dietert (model number 473). Since the mixture is very hard, the release time is reached as soon as the scale reaches a value of 95 or more. The release times of the individual mixtures are specified in Table 8.

[0106] 3. Test of flexural strength To determine the flexural strength, the test bar was inserted into a stability testing device (Jung Instruments, model SJ1) equipped with a three-point bending device, the force was measured, and the test bar was caused to break. The flexural strength was determined by the following method. · 1 hour after forming · 2 hours after forming · 4 hours after forming · 24 hours after forming

[0107] The results are shown in Table 8.

[0108]

Table 8

[0109] 4. Storage stability test To evaluate the storage stability, the resol resins 1 to 5 described in 1 were stored at room temperature. The viscosity and gelation time were tested at regular intervals immediately after production and after storage. Resol resin 6 was classified as having no advantages because of its long release period and low bending strength, was determined at the 3rd point, and no further analysis was performed.

[0110] 4.1 Viscosity test The viscosity of the resol resin was measured at 100 U / min and 25 °C using a Brookfield rotational viscometer, small sample, and spindle No. 21.

[0111] The results are shown in Table 9.

[0112]

Table 9

[0113] 4.2 Gelation time test The gelation time of the resol resin was measured at 25 °C using a Gelnorm Geltimer by Gel Instrumente (Geltimer-m type and ST1 type). For this purpose, 18 g of resol resin and 2 g of catalyst 5090 (ASK Chemicals) in triacetin were mixed in a test tube in each case, and the time until the mixture hardened was measured as the gelation time.

[0114] The results are shown in Table 10.

[0115]

Table 10

[0116] 5. Evaluation The evaluation can be understood from Tables 8 to 10

[0117] · The mold material mixture produced from resol resins 2 to 5 was manufactured using o-cresol, comparable to the mold material mixture produced from the comparative resol resin 1 without using o-cresol, and showed effective processing time and demolding time · The test bars produced from resol resins 2 to 5 containing o-cresol and phenol showed higher stability than the test bars produced from the comparative resol resin 1 without o-cresol · The mold material mixture produced from resol resin 6 with a large amount of o-cresol showed a further delayed demolding period. The test bars produced from the mold material mixture showed lower stability. Resol resin 6 is not very suitable for use · The resol resins 2 to 5 produced using o-cresol had a lower viscosity increase after storage and a longer gelation time than the comparative resol resin 1 produced without using o-cresol

Claims

1. A method of forming an object into a layered structure, comprising: (a) collecting one or more refractory mold substrates and one or more esters to obtain a mixture of mold materials impregnated with an ester; (b) applying a thin layer of the mixture of mold materials impregnated with an ester, the layer thickness of which is 1 to 6 grains; (c) brushing a selected area of the thin layer with a binder containing an alkaline resol resin that cures the area; (d) repeating steps (b) and (c) a plurality of times for finishing at least a partially cured three-dimensional object and at least including, the alkaline resol resin can be obtained by the conversion of formaldehyde with at least phenol and at least ortho-substituted and / or para-substituted phenols, the substituent is an aliphatic, branched or unbranched, or saturated or unsaturated hydrocarbon radical having 1 to 4 carbon atoms, and the molar ratio of the ortho-substituted and / or para-substituted phenol (A) to the phenol (B) is 1:1.5 to 1:15 (A:B), the viscosity of the binder is 3 mPa·s to 100 mPa·s and can be determined at 100 U / min and 25 °C with the aid of a Brookfield rotational viscometer, spindle No. 21 Method.

2. The molar ratio of at least the ortho-substituted and / or para-substituted phenol to the phenol (B) is 1:2 to 1:10 The method according to claim 1.

3. The hydrocarbon radical of at least the ortho-substituted and / or para-substituted phenol is one or more methyl groups The method according to claim 1 or 2.

4. The ortho-substituted and / or para-substituted phenol is selected from the group consisting of o-cresol, p-cresol, 2,4-xylenol, 2,6-xylenol, 2,3-xylenol, 2,5-xylenol, 3,4-xylenol, and mixtures thereof The method according to claim 1 or 2.

5. (e1) removing the unbonded mixture of mold materials from at least a partially cured casting mold and at least further including, optionally, (e2) post-curing the at least partially cured three-dimensional object in a furnace or by microwave and at least further including, The steps are carried out in the order of step (e1), step (e2), or in the order of step (e2), step (e1). The method according to any one of claims 1 to 4.

6. The refractory mold base material includes quartz sand, zircon sand, or chromite sand, sillimanite, vermiculite, bauxite, chamotte, glass beads, glass granules, hollow microbeads of aluminum silicate, synthetic mold base materials based on mullite, and mixtures thereof. The method according to any one of claims 1 to 5.

7. More than 80 weight percent of the mixture of the mold material is a refractory mold base material. The method according to any one of claims 1 to 6.

8. The average particle size of the refractory mold base material is 80 μm to 600 μm, and is determined by sieve analysis. The method according to any one of claims 1 to 7.

9. In particular, amorphous silicon dioxide with an area of 1 to 200 m ２ / g is further added to the mixture of the mold material, and the area is determined by BET The method according to any one of claims 1 to 8.

10. More than 90 mol% of the hydroxyaromatic compounds in the resol resin, or all of the hydroxyaromatic compounds, are phenol and ortho-substituted and / or para-substituted phenols, respectively, or are based on the monomer components thereof. The method according to any one of claims 1 to 9.

11. In each case, the resol resin is used in an amount of 0.8 to 8 weight percent based on the weight of the refractory mold base material. The method according to any one of claims 1 to 10.

12. The object is CO ２ retrogradely cured by The method according to any one of claims 1 to 11.

13. The mixture of the mold material contains an alkali hydroxide. The method according to any one of claims 1 to 12.

14. The resol resin is used in the form of an alkaline aqueous solution, the solid content is 20 to 75 weight percent, and the pH value exceeds 11 when measured at 25 °C. The method according to any one of claims 1 to 13.

15. The ester is an ester compound capable of alkaline hydrolysis or a phosphate ester compound. The method according to any one of claims 1 to 14.

16. The ester is selected from lactones, organic carbonates, and esters of monocarboxylic acids and polycarboxylic acids having 1 to 10 carbon atoms and monoalcohols and polyalcohols having 1 to 10 carbon atoms. The method according to any one of claims 1 to 15.

17. The ester is (a) In each case, in an amount of 5 weight percent to 50 weight percent, based on the binder, and / or (b) In each case, in an amount of 0.04 weight percent to 4.0 weight percent, based on the mold substrate (used) The method according to any one of claims 1 to 16.

18. The object obtained by the method of forming the object into the layered structure is a mold or a core used in metal casting The method according to any one of claims 1 to 17.

19. The brushing is performed by a print head having a plurality of ejection ports The method according to any one of claims 1 to 18.

20. The print head is at least movable in one or more planes controlled by a computer, and the ejection ports apply the liquid binder layer by layer The method according to claim 19.

21. The print head is a drop-on-demand type print head including bubble jet technology or piezo technology The method according to claim 19 or 20.

22. The viscosity of the binder is 4 mPas to 50 mPas The method according to any one of claims 1 to 21.

23. Use of a binder for binding a mixture of a mold material impregnated with an ester, wherein the binder contains an alkaline resol resin, the alkaline resol resin is obtainable from the conversion of formaldehyde with at least phenol and at least ortho-substituted and / or para-substituted phenols, the substituents are aliphatic, branched or unbranched, or saturated or unsaturated hydrocarbon radicals having 1 to 4 carbon atoms, and the molar ratio of the ortho-substituted and / or para-substituted phenol (A) to the phenol (B) is 1:1.5 to 1:15 (A:B), the viscosity of the binder is 3 mPas to 100 mPas, determined at 100 U / min and 25 °C with a Brookfield rotational viscometer, spindle No. 21 (Use)

24. The molar ratio of at least the ortho-substituted and / or para-substituted phenol (A) to the phenol (B) is 1:2 to 1:10 The use according to claim 23. **Claim 25**: The ortho-substituted and / or para-substituted phenol is selected from the group consisting of o-cresol, p-cresol, 2,4-xylenol, 2,6-xylenol, 2,3-xylenol, 2,5-xylenol, 3,4-xylenol, and mixtures thereof. The use according to claim 23 or 24. **Claim 26** In the resol resin, more than 90 mol% of the hydroxyaromatic compounds are each phenol and / or ortho-substituted and / or para-substituted phenol, or are based on the monomer components thereof. The use according to any one of claims 23 to 25. **Claim 27** The resol resin is present in the form of an alkaline aqueous solution, and when measured at 25 °C, the pH value exceeds 11. The use according to any one of claims 23 to 26. **Claim 28** The resol resin is present in the form of an alkaline aqueous solution, and in the binder, the solid content is 20 to 75 weight percent. The use according to any one of claims 23 to 27. **Claim 29** The viscosity of the binder is 4 mPas to 50 mPas. The use according to any one of claims 23 to 28.

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