Moulding material for producing a clay-bonded mould, and use thereof in a moulding material cycle

Abstract

The invention relates to a moulding material for producing a clay-bonded mould and to the use thereof in a moulding material cycle.

Description

[0001] Moulding material for the production of a clay-bound mould and its use in a moulding material cycle

[0002] The present invention relates to a molding material for producing a clay-bonded mold and its use in a molding material cycle.

[0003] Clays used for binding molding materials typically contain smectite. Examples of such smectite-containing clays are bentonites, particularly sodium and calcium bentonites, which contain sodium and calcium, respectively, along with the elements magnesium, aluminum, and silicon. Other smectite-containing clays include hectorite, saponite, nontronite, beidellite, and sauconite. Clays such as kaolinite or illite can be used as clay-containing binders in mixtures with smectite-containing clays.

[0004] The smectite-containing clay preferably has a montmorillonite content of 50 wt% or more, particularly preferably 60 wt% or more, and particularly preferably 70 wt% or more. If the montmorillonite content is too low in a naturally occurring smectite-containing clay, it can be increased by purification. This applies particularly to bentonite.

[0005] For example, sodium bentonite can contain 70 to 95 wt.% montmorillonite, with the remaining components being quartz, opal, cristoballite, feldspar, biotite, clinoptilite, calcite, gypsum, and others. Accordingly, in this document, the terms "smectite-bearing clays" and "bentonite" are used both to refer to corresponding clays extracted from natural deposits and to those produced by purifying naturally occurring clays.

[0006] In this document, the term "clay-bonded mold" is used, where appropriate, for casting molds bonded with a smectite-containing clay. This always refers to casting molds bonded with a smectite-containing clay. Smectite-containing clays in the form of sodium or calcium bentonite and / or mixtures thereof are preferred in the foundry industry. These mixtures are sometimes produced in situ by adding salts and resulting ion exchange.

[0007] Any sand that can form a foundry mold and retain its shape at high temperatures and in contact with hot metal can be used as a mold base material. Typical sands include silica sand, olivine sand, chromium ore sand, zircon sand, and artificially produced ceramic sands or mixtures of these sands. Typically, a mold contains at least 40% sand, preferably over 50% sand, particularly preferably over 60% sand, and most preferably over 70% sand.

[0008] In industrial practice, clay-bonded casting molds are typically made from a molding material that contains smectite-containing clay as a binding agent and the mold base material, as well as additives and water. Such molding materials are also referred to as "green sand" or "wet casting sand." Compaction of the molding material leads to solidification, thus ensuring sufficient dimensional stability.

[0009] In industrial practice, a molding material with smectite-containing clay as a binder is commonly used in a molding material cycle.

[0010] Molding material recycling, as defined in this disclosure, means that molding material from cast molds ("cast molding material," also referred to as used sand) is processed and used to produce new molding material, from which new molds are produced that are then cast. The molding base material contained in the molding material is therefore at least partially present as a component of processed molding material from at least one previously cast clay-bonded mold.

[0011] A molding material cycle within the meaning of the present disclosure consists of at least two chronologically consecutive cycles. Two (not necessarily directly consecutive) cycles of a molding material cycle can therefore be distinguished as an earlier cycle and a later cycle. If the molding material cycle consists of only two cycles, the first cycle in the chronological sequence is the earlier cycle, and the second cycle in the chronological sequence is the later cycle.

[0012] A cycle of this molding material cycle can be described by the following characteristic steps (see Figure 1 for the following designation of the steps):

[0013] (Step 1) Production of the moulding material, i.e. production of a moulding material comprising recycled moulding material from a previous cycle and aggregates (see below)

[0014] (Step 2) Making the mold, ie making a mold bound with smektite-containing clay from the molding material produced in step (1),

[0015] (Step 3) Casting, ie producing a casting by pouring the mold produced in step (2)

[0016] (Step 4) Separating, i.e. separating the casting produced in step (3) from the mold, resulting in a cast molding material comprising material from the cast mold

[0017] (Step 5) Preparation of the cast molding material, ie preparation of the cast molding material from step (4) so ​​that a first prepared molding material is obtained for producing a new molding material in step (1) of a later cycle.

[0018] In certain cases, it is preferred that one, several, or all cycles of the molding material cycle include additional steps, and / or that individual steps have additional features. Details of this can be found in the following description, as well as the appended claims and drawings.

[0019] In each cycle of the mold material cycle described above, step (3) involves the production of a casting by pouring the mold produced in step (2). The mold material undergoes significant material changes due to thermal and chemical stress during pouring (step (3) of the cycle). To enable a recycling of the mold material, the poured mold material must be processed.

[0020] In some cases, particularly for the production of castings with complex geometries, step (3) involves producing a casting by pouring the mold produced in step (2) with one or more inserted cores (see Figure 3). Cores used in clay-bonded molds are typically not clay-bonded. Typically, such cores are produced with an organic binder, e.g., a polyurethane or a phenolic resin, or with an inorganic binder that does not contain clay, e.g., a binder containing water glass. If the casting produced in step (3) is separated from the mold and cores in step (4), the result is usually a cast molding material that contains material from the cast cores (old core sand).

[0021] The processing of the cast molding material in step (5) results in a processed molding material that remains in the molding material cycle. Thus, a portion of the molding base material used (usually quartz sand) remains in the molding material cycle as a component of the processed cast molding material.

[0022] The processing regularly includes crushing the cast molding material (grain separation) and extensive removal of metal residues and other contaminants, for example contaminants in the form of auxiliary products from the casting process (core marks, feeder residues, etc.).

[0023] The thermal, mechanical and possibly also chemical stress during casting gives rise to wear products such as fine sand particles, inactive clay particles, decomposition products of the additives, in particular the lustrous carbon formers, reaction products of core binders, as well as oolitized grains of the mold base material.

[0024] To prevent such wear products from accumulating in the molding material cycle and / or to prevent the molding material properties from being negatively affected, or to prevent the required active components of the binder (smectite-containing clay) and additives from decreasing too much, additives are added in each subsequent cycle in step 1 during molding material production, i.e., the processed molding material is refreshed with the additives. To keep the mass of the molding material circulating in the cycle constant, a corresponding amount of molding material is removed from the molding material cycle. This can occur before refreshing with the additives (i.e., in step (5)) or after refreshing with the additives.

[0025] The aggregates typically include smectite-containing clay, water, additives (see below) and one or more raw materials from the group consisting of fresh molding material (new sand), second processed molding material produced by processing uncast molds and / or cores and / or parts thereof, third processed molding material produced by processing molds and / or cores and / or parts thereof that were produced and cast outside the considered molding material cycle.

[0026] Preferably, the additives (especially the bentonite) also contain water.

[0027] The molds and cores from which the second and third processed molding materials are obtained as defined above do not have to be clay-bonded. In particular, the cores are typically not clay-bonded, but rather are made with a conventional organic binder, e.g., polyurethane, particularly polyurethane formed in the cold-box process, or with a phenolic resin in the form of a resole, particularly those resoles used in the hot-box or warm-box process, or a novolak, particularly novolaks used in the Croning process or shell molding process.

[0028] In each cycle of an industrial molding material cycle, a substantially consistent quality of the castings should be achieved during casting. Through a controlled supply and removal of molding material components, essentially constant, optimal molding material properties can be achieved in the molding material cycle (molding material conditioning). In each cycle, the molding material is conditioned, i.e., optimally adjusted, by determining the required addition rates of smectite-containing clay (optional), additives, water, and new sand or second and third processed molding material as defined above, as well as by determining the amount of used sand to be removed and by specifying machine parameters such as mixing time or cooling intensity.

[0029] In industrial practice, molding materials for the production of clay-bonded casting molds usually contain additives in the form of so-called lustrous carbon formers.

[0030] Lustrous carbon formers (also known as lustrous carbon carriers, see https: / / www.giesserei-praxis.de / giesserei-lexikon / glossar / glanzkohlenstoff) are molding material additives capable of forming hydrocarbon-containing gases that are coked in the reducing atmosphere of the mold cavity during casting. This produces lustrous carbon. Commonly used lustrous carbon formers include coal dust, pitch, bitumen, resins, oils, plastics, and mixtures thereof. Lustrous carbon formers are particularly added to clay-bonded molding materials for iron casting. The lustrous carbon prevents wetting by the liquid casting material at the metal / mold interface. Lustrous carbon formers in the molding material can also buffer quartz expansion and prevent sand expansion defects.However, increasing proportions of coal dust or other lustrous carbon formers and higher proportions of the decomposition products (coke) of the lustrous carbon formers in the processed molding material increase the water requirement of the molding material. An increased amount of water in the molding material can lead to casting defects such as explosion penetrations.

[0031] Since lustrous carbon formers are thermally decomposed and coked during casting, the corresponding losses in the molding material cycle must be regularly replaced by adding fresh lustrous carbon formers in industrial practice. For this purpose, fresh lustrous carbon formers are added at least in some cycles, but preferably in all cycles, of the molding material cycle.

[0032] A major disadvantage of using lustrous carbon formers is the release of emissions, for example, in the form of CO, CO2, NOx, and volatile organic compounds, particularly aromatic hydrocarbons such as benzene, toluene, and xylenes ("BTX emissions"), but also polycyclic aromatics. In addition, volatile sulfur-containing compounds are usually also emitted, as lustrous carbon formers often contain sulfur and / or sulfur-containing impurities. A further problem is the considerable risk of dust explosions and spontaneous combustion when handling lustrous carbon formers. Therefore, in the production of clay-bound molds, lustrous carbon formers are typically used in industrial foundries in the form of a pre-mixed mixture with the smectite-containing clay, particularly bentonite, prepared by the supplier.

[0033] For the reasons mentioned above, it is desirable and necessary to restrict the use of lustrous carbon formers or to replace lustrous carbon formers, at least in a significant proportion, with suitable alternatives.

[0034] US 5,372,636 A discloses a molding material comprising sand, a sodium smectite clay (in particular sodium bentonite), and at least one oxide, salt (in particular carbonate), or hydroxide of a metal, e.g., aluminum, calcium, iron, sodium, magnesium, boron, or zinc. Recycling of the molding material is not disclosed. Thus, this document provides no information as to whether such molding materials are suitable for use in a molding material cycle. WO 03 / 066253 A1 describes a process for producing a molding material, in particular a recycled one, for foundry purposes, according to which a material that does not swell in water is added to a mixture of a granular mass and additives, such as a binder, e.g., bentonite, and water.As non-swellable porous material, framework or tectosilicates such as zeolites, pumice or pumice stones, allophane, imogolite, diatomaceous earth, polygarskite, sepiolite, diatomaceous earth, or clays (treated with acid and / or heat) are used in particular.

[0035] CN 108356214 discloses moulding material mixtures comprising sand, water, bentonite and an additive having the following composition

[0036] SiO250-85 wt%

[0037] Al2O3 9-45 wt%

[0038] MgO 0.2-3 wt%

[0039] Fe2O3 1-8 wt%

[0040] CaO 1-7 wt%

[0041] Fe3Ü4 0.4-8 wt%

[0042] The additive is produced by mixing the individual oxides. It is intended to replace lustrous carbon formers. Molding materials containing this additive are said to be easily recyclable. Sample molding materials were used for two to four months.

[0043] The primary objective of the present invention is to reduce carbon-based emissions and / or carbon-based casting defects. Carbon-based emissions include, for example, emissions in the form of CO, CO2, and volatile organic compounds, in particular aromatic hydrocarbons such as benzene, toluene, and xylenes ("BTX emissions"), but also polycyclic aromatics.

[0044] The primary object of the present invention is to provide a molding material for producing a clay-bonded mold that can be used in the molding material cycle, reducing carbon-based emissions and / or carbon-based casting defects.

[0045] This object is achieved by a molding material for producing a clay-bound mold, wherein the molding material comprises: a molding base material, a smectite-containing clay, in particular a bentonite, in a concentration of 4.5 to 16 wt%, preferably 6 to 12 wt%, and particularly preferably 7 to 10 wt%, based on the mass of the molding material, one or more dehydratable inorganic compounds which release water at a temperature of 150 °C or more, wherein the total concentration of said dehydratable inorganic compounds is 5 to 60 wt%, preferably 10 to 55 wt%, and particularly preferably 15 to 50 wt%, based on the mass of the smectite-containing clay,

[0046] Water in a concentration of 1.5 to 10 wt%, preferably 2 to 5 wt% based on the mass of the molding material,

[0047] Carbon in a concentration of 1.5 wt% or less, preferably 1 wt% or less, particularly preferably 0.5 wt% or less, most particularly preferably 0.3 wt% or less, based on the mass of the molding material.

[0048] The molding material cycle to which the invention relates is preferably an industrial molding material cycle in a foundry, preferably a foundry with at least one production line integrated into the molding material cycle and optionally at least one further production line in which molds and / or cores are produced and / or cast that are not clay-bound.

[0049] Further special features, details, advantages and preferred embodiments of the molding material according to the invention emerge from the following description as well as the appended claims and drawings.

[0050] The carbon content of a molding material is determined by elemental analysis and includes carbon components from organic carbon carriers as well as inorganic carbon carriers. Organic carbon carriers include, in particular, lustrous carbon formers, organic binders, organic additives, as well as residues or decomposition products of lustrous carbon formers, organic binders, and organic additives. Inorganic carbon carriers include, in particular, carbonates, which may be present as additives in the molding material.

[0051] In molding materials with smectite-containing clay as a binder, the carbon content can be reduced, particularly by reducing or avoiding the use of lustrous carbon formers. Reducing or even avoiding the use of lustrous carbon formers conserves fossil resources. Thus, a further object achieved by the present invention is to provide a molding material for a resource-saving molding material cycle.

[0052] By reducing or even eliminating the use of lustrous carbon formers, the risk of dust explosions and spontaneous combustion during transport, storage, and handling of the lustrous carbon formers is reduced or even eliminated. Thus, a further object achieved by the present invention is to reduce the risk of dust explosions and spontaneous combustion during transport, storage, and handling of the lustrous carbon formers.

[0053] By reducing or even eliminating the use of lustrous carbon formers, fewer pyrolysis products are produced during casting, which contaminate the cast molding material or the molding material discharged from the molding material cycle. The lower carbon and sulfur contents in the cast molding material associated with a reduction in the use of lustrous carbon formers are also advantageous for the landfilling of non-reusable molding material components. Thus, a further object achieved by the present invention is to facilitate the reuse or landfilling of cast molding material.

[0054] Further objects achieved by the present invention are to reduce sulfur-based emissions and NOx emissions during a molding material cycle comprising two or more cycles.

[0055] A further object solved by the present invention is to reduce the odor nuisance released during pouring.

[0056] The reduction in the proportion of lustrous carbon should not impair the properties of the molding material, the molds made from it, and the castings produced therefrom in an unacceptable manner.

[0057] The solution to the above-defined problems is based on the use of an additive that is similarly effective in preventing mold expansion defects, separating metal from the molding material, and promoting mold decomposition as the lustrous carbon formers used in the prior art. Surprisingly, it has been found that dehydratable inorganic compounds that release water at a temperature of 150 °C or more can be similarly effective in preventing mold expansion defects and promoting mold decomposition as the lustrous carbon formers used in the prior art.

[0058] Dehydration means the elimination of chemically (e.g. in the form of hydroxide ions) or physically (e.g. as water of crystallization in hydrates) bound water by heating.

[0059] The dehydratable inorganic compounds contained in the additive to be used according to the invention are preferably compounds from the group of hydroxides and hydrate salts of metals. The term hydroxides as used here also includes oxide hydroxides. Hydroxides and hydrate salts of metals in the +II or +III oxidation state are preferred, particularly preferred are hydroxides of metals in the +II or +III oxidation state. Magnesium hydroxide (particularly in the form of brucite) and aluminum hydroxide are especially preferred, with aluminum trihydroxide Al(OH)3 being most preferred. The aluminum trioxide can be present in various modifications, particularly as gibbsite, bayerite, or nordstrandite, as well as in minerals in combination with other hydroxides or oxides.

[0060] Preferably, the additive to be used according to the invention does not comprise carbon or carbon carriers.

[0061] Since the molding material according to the invention is used in a molding material cycle, the molding base material can be present in the molding material according to the invention at least partially as a component of processed molding material (as defined above). Preferably, the molding base material is present at least partially as a component of processed molding material from at least one previously cast mold bonded with smectite-containing clay.

[0062] Since the molding material according to the invention is used in a molding material cycle, it may contain one or more reaction products formed by water elimination from the said dehydratable inorganic compound(s), which are formed during casting from the additive defined above.

[0063] If the additive contains aluminum hydroxide, aluminum oxides are formed during pouring, with the loss of water. While some modifications of aluminum oxide, e.g., γ-aluminum oxide, can be converted back to aluminum hydroxide by adding water, at temperatures above 1000 °C, aluminum hydroxide is irreversibly converted to corundum (α-aluminum hydroxide), which cannot be converted back to aluminum hydroxide by adding water and is therefore no longer capable of functioning as an additive according to the invention as defined above.

[0064] Therefore, it is preferred that less than 50 wt%, preferably less than 25 wt% and particularly preferably less than 10 wt% of the AI2O3 contained in the molding material is in the form of corundum.

[0065] The mold base material is preferably selected from the group consisting of quartz sand, olivine sand, chromium ore sand, zircon sand, and artificially produced ceramic sands, and mixtures of these sands. Typically, a mold contains at least 40% sand, preferably over 50% sand, more preferably over 60% sand, and most preferably over 70% sand.

[0066] Since the molding material according to the invention is used in a molding material cycle, it may contain reaction products of the smectite-containing clay that cannot be reactivated by adding water. If bentonite is used as the smectite-containing clay, the temperatures during casting will cause chamotte (also known as hard bentonite or dead-burned bentonite), which is a component of the molding material.

[0067] The free water content in the molding material is determined by determining the mass loss after drying at 105 °C to constant mass according to VDG Data Sheet P32 (April 1997).

[0068] The smectite-containing clay is preferably a bentonite, particularly preferably selected from the group consisting of sodium bentonite and calcium bentonite and mixtures thereof.

[0069] A molding material according to the invention may also contain one or more clays from the group consisting of kaolinite and illite.

[0070] A preferred molding material according to the invention has one or more of the following parameters: a compressibility in the range of 25% to 55%, determined according to VDG Data Sheet P37 (April 1997), a green compressive strength in the range of 8 N / cm 2 up to 35 N / cm 2 , determined according to VDG data sheet P38 (May 1997) a wet tensile strength of 0.10 N / cm 2 up to 0.50 N / cm 2, determined according to VDG data sheet P38 (May 1997) a gas permeability of 70 to 200, determined according to BDG guideline P41 (October 2013) an active clay content of 4.5 to 16%, determined by the methylene blue method according to VDG data sheet P035 (October 1999) a flowability of 20% to 90%, determined according to Morek Multiserw, operational documentation pile driving device type LUA-2e with electric drive, page 7.

[0071] A molding material according to the invention particularly preferably has the following parameters: a compressibility in the range of 30% to 50%, determined according to VDG Data Sheet P37 (April 1997) and / or a green compressive strength in the range of 10 N / cm 2 up to 28 N / cm 2 , determined according to VDG Data Sheet P38 (May 1997) and / or a wet tensile strength of 0.20 N / cm 2 up to 0.45 N / cm 2, determined according to VDG Data Sheet P38 (May 1997) and / or a gas permeability of 90 to 160, determined according to BDG Guideline P41 (October 2013) and / or an active clay content of 6 to 12%, determined by the methylene blue method according to VDG Data Sheet P035 (October 1999) and / or a flowability of 50% to 90%, determined according to Morek Multiserw, Technical Operational Documentation for Piling Machine Type LUA-2e with Electric Drive, page 7.

[0072] Preferably, all of the above-mentioned parameters of the molding material are in the above-mentioned preferred, in particular in the above-mentioned particularly preferred ranges.

[0073] In certain cases, a molding material according to the invention comprises prepared molding material from at least one cast or uncast core. The cores are typically not clay-bonded, but rather bonded with an organic binder or with an inorganic binder that does not contain clay. Uncast molds and / or cores are molds and / or cores that were not cast for various reasons, e.g., due to processing errors or lack of dimensional accuracy.

[0074] In a molding material according to the invention which contains processed molding material from at least one cast or uncast core, the dehydratable inorganic compounds are preferably selected from the group consisting of aluminum hydroxide and magnesium hydroxide, wherein the proportion of aluminum hydroxide is at least 80%, preferably at least 90%, and particularly preferably at least 95%, very particularly preferably 99%, based on the total mass of aluminum hydroxide and magnesium hydroxide in the additive, wherein the aluminum hydroxide is preferably Al(OH)3.

[0075] In a first embodiment, the molding material according to the invention comprises processed molding material from at least one core or mold containing an inorganic binder and / or its reaction products formed during casting. The inorganic binder is preferably a binder containing water glass, in particular water glass hardened thermally and / or by gassing with CO2.

[0076] A preferred molding material according to this first embodiment has one or more of the following parameters a concentration of less than 1.5%, preferably less than 0.8% carbon, based on the mass of the molding material, determined by elemental analysis a concentration of less than 0.1%, preferably less than 0.05% nitrogen, based on the mass of the molding material, determined by elemental analysis a concentration of less than 0.05%, preferably less than 0.03% sulfur, based on the mass of the molding material, determined by elemental analysis a loss on ignition of at most 5%, preferably at most 3.5%, determined according to VDG Data Sheet P33 (April 1997).

[0077] A particularly preferred molding material according to this first embodiment has the following parameters: a concentration of less than 0.8%, preferably less than 0.4%, particularly preferably less than 0.2% carbon based on the mass of the molding material, determined by elemental analysis a concentration of less than 0.05%, preferably less than 0.03%, very particularly preferably less than 0.01% nitrogen based on the mass of the molding material, determined by elemental analysis a concentration of less than 0.03%, preferably less than 0.01%, very particularly preferably less than 0.005% sulfur, based on the mass of the molding material, determined by elemental analysis a loss on ignition of at most 3.5%, preferably at most 3%, particularly preferably at most 2.5%, determined according to VDG Data Sheet P33 (April 1997).

[0078] Preferably, all of the above-mentioned parameters of the molding material are in the above-mentioned preferred, in particular in the above-mentioned particularly preferred ranges.

[0079] In a second embodiment, the molding material according to the invention comprises processed molding material from at least one mold or core containing an organic binder and / or its reaction products formed during casting. The organic binder is particularly preferably polyurethane, in particular polyurethane formed in the cold-box process, or a phenolic resin in the form of a novolak or a resol.

[0080] In this second embodiment, preferably at least 70% by weight, preferably at least 80% by weight, and particularly preferably at least 90% by weight, very particularly preferably 95% of the carbon contained in the molding material originates from the organic binder of cast and uncast cores and the reaction products of the binder.

[0081] A preferred molding material according to this second embodiment has one or more of the following parameters a concentration of less than 4%, preferably less than 3% carbon, particularly preferably less than 1.5%, based on the mass of the molding material, determined by elemental analysis a concentration of less than 0.2%, preferably less than 0.1% nitrogen, based on the mass of the molding material, determined by elemental analysis a concentration of less than 0.05%, preferably less than 0.03% sulfur, based on the mass of the molding material, determined by elemental analysis a loss on ignition of at most 5%, preferably at most 4%, determined according to

[0082] VDG Data Sheet P33 (April 1997) A particularly preferred molding material according to this embodiment has the following parameters a concentration of less than 3%, preferably less than 2.5%, particularly preferably less than 2%, very particularly preferably less than 1.5% by weight of carbon, based on the mass of the molding material, determined by elemental analysis a concentration of less than 0.1%, preferably less than 0.07%, particularly preferably less than 0.05% nitrogen, based on the mass of the molding material, determined by elemental analysis a concentration of less than 0.03%, preferably less than 0.01%, particularly preferably less than 0.05% sulfur, based on the mass of the molding material, determined by elemental analysis a loss on ignition of at most 4%, preferably at most 3.5%, particularly preferably less than 3%, determined according to VDG Data Sheet P33 (April 1997).

[0083] Preferably, all of the above-mentioned parameters of the molding material are in the above-mentioned preferred, in particular in the above-mentioned particularly preferred ranges.

[0084] A further aspect of the present disclosure relates to the use of the molding material defined above for producing a mold bonded with smectite-containing clay. The above statements apply to preferred molding materials.

[0085] A further aspect of the present disclosure relates to the use of the molding material defined above in a molding material cycle, in particular in a conditioned molding material cycle. The above statements apply to preferred molding materials.

[0086] A further aspect of the present disclosure concerns the use of the above-defined additive for producing a molding material according to the invention. The above statements apply to preferred additives.

[0087] A further aspect of the present disclosure relates to a method for guiding a molding material in a molding material cycle comprising two or more cycles, comprising the following steps: in an earlier cycle of said two or more cycles of the molding material cycle, casting in a mold comprising molding material bound with smectite-containing clay, resulting in a cast molding material, processing the cast molding material so that a first processed molding material results, in a later cycle of said two or more cycles of the molding material cycle, producing a molding material as defined above, comprising

[0088] (i) first processed molding material, and

[0089] (ii) Aggregates comprising one or more raw materials from the group consisting of

[0090] Mold base material, a second processed mold material produced by processing molds and / or cores cast outside the mold material cycle, a third processed mold material produced by processing mold material from uncast molds and / or cores, an additive which contains at least one dehydratable inorganic compound which releases water at a temperature of 150 °C or more, and optionally smectite-containing clay, preferably bentonite.

[0091] The additives preferably also include water.

[0092] The molding material cycle to which the method according to the invention relates is preferably an industrial molding material cycle in a foundry, preferably a foundry with at least one production line which is integrated into the molding material cycle, and optionally at least one further production line in which molds and / or cores which are not clay-bound are produced and / or cast.

[0093] In an earlier cycle of the two or more cycles of the molding material cycle, a mold comprising molding material bound with smectite-containing clay is cast, producing a casting. The casting of the mold results in a cast molding material. The cast molding material is processed as described above to produce a first processed molding material. To keep the mass of the molding material circulating in the cycle constant, a portion of the cast molding material may be removed during processing, resulting in a removed molding material.

[0094] In a later cycle of the molding material cycle, a molding material according to the invention is produced comprising (i) first prepared molding material as defined above, and (ii) additives. These additives comprise the additive as defined above and one or more raw materials from the group consisting of

[0095] Molding base material, in particular quartz sand, a second processed molding material produced by processing molding material from uncast molds and / or cores and / or parts thereof, a third processed molding material produced by processing molding material from molds and / or cores and / or parts thereof cast outside the molding material cycle, and optionally smectite-containing clay, preferably bentonite.

[0096] If a portion of the cast molding material has not already been discharged after processing, a portion of the produced molding material can now be discharged to keep the mass of the recirculated molding material constant, resulting in discharged molding material. However, this is not mandatory. The molding material cycle can include individual cycles in which no molding material is discharged.

[0097] The molding material according to the invention, produced in a later cycle of the molding material cycle, comprises one, several, or all of the aforementioned raw materials. The molding base material used as a raw material preferably comprises fresh quartz sand (new sand), or silica sand, olivine sand, chromium ore sand, zircon sand, or artificially produced ceramic sands, or mixtures of these sands.

[0098] The smectite-containing clay is preferably bentonite, in particular from the group consisting of sodium and calcium bentonite and their mixtures.

[0099] The second reprocessed molding material, as defined above, is produced by reprocessing molding material from uncast molds and / or cores and / or parts thereof. Uncast molds and / or cores are molds and / or cores that were not cast for various reasons, e.g., due to processing errors or lack of dimensional accuracy.

[0100] The third recycled molding material as defined above is produced by recycling molding material from molds and / or cores and / or parts thereof cast outside the considered molding material cycle, i.e. molds and cores cast, for example, in another production line.

[0101] The molds and cores from which the second and third processed molding materials are obtained as defined above must be non-clay-bound. In particular, the cores are typically not clay-bound. Typically, the second processed molding material is produced by processing molding material from uncast molds and / or cores and / or parts thereof, wherein the molds and cores are not clay-bound. Typically, the third processed molding material is produced by processing molding material from molds and / or cores and / or parts thereof cast outside the molding material cycle, wherein the molds and cores are not clay-bound. In these cases, said molds or cores contain a conventional organic binder, e.g. a phenolic resin or a polyurethane formed in a cold-box process and / or its reaction products formed during casting; or an inorganic binder, e.g.a binder containing water glass, and / or its reaction products formed during pouring.

[0102] In the method according to the invention, an earlier and a later, and preferably all cycles of the method according to the invention comprise the following steps (see Figure 2, the further features of which are not intended to be limiting):

[0103] (Step 1) Producing the molding material, ie producing a molding material comprising

[0104] (i) the first reprocessed moulding material produced by reprocessing the cast moulding material resulting from a previous cycle of the moulding material cycle as defined above and

[0105] (ii) Aggregates as defined above

[0106] (Step 2) Making the mold, i.e. making a mold bound with smectite-containing clay from the molding material produced in step (1) (Step 3) Casting, i.e. making a casting by casting the mold produced in step (2)

[0107] (Step 4) Separation, i.e. separation of the casting produced in step (3) from the mold, resulting in a cast molding material

[0108] (Step 5) Preparation, ie preparation of the cast molding material from step (4) so ​​that a first prepared molding material is obtained for producing a new molding material in step (1) of a later cycle, and optionally discharge of a part of the cast molding material so that discharged molding material results.

[0109] If part of the cast molding material has not already been discharged during processing in step (5), in order to keep the mass of the circulating molding material constant, part of the molding material produced in step (1) of the next cycle is discharged, resulting in discharged molding material.

[0110] In a specific embodiment of the method according to the invention, an earlier and a later, and preferably all cycles of the method according to the invention comprise the following steps (see Figure 4, the further features of which are not intended to be limiting):

[0111] (Step 1) Producing the molding material, ie producing a molding material comprising

[0112] (i) reprocessed moulding material produced by reprocessing the cast moulding material resulting from a previous cycle of the moulding material cycle as defined above and

[0113] (ii) Aggregates as defined above

[0114] (Step 1 a) Producing the core molding material, i.e. producing or providing a molding material for producing at least one core

[0115] (Step 2) Making the mold, i.e. making a mold bonded with smectite-containing clay from the molding material prepared in step (1)

[0116] (Step 2a) Producing the core, ie producing or providing at least one core and inserting the at least one core into the mold produced in step (2)

[0117] (Step 3) Casting, i.e. producing a casting by casting the mold produced in step (2) with the at least one core inserted in step (2a), (Step 4) Separating, i.e. separating the casting produced in step (3) from the mold and the at least one core, whereby a cast molding material containing material from the cast mold and from the cast core results

[0118] (Step 5) Preparation, ie preparation of the cast molding material from step (4) so ​​that a first prepared molding material is obtained for producing a new molding material in step (1) of a later cycle, and optionally discharge of a part of the cast molding material so that discharged molding material results.

[0119] If part of the cast molding material has not already been discharged during processing in step (5), in order to keep the mass of the circulating molding material constant, part of the molding material produced in step (1) of the next cycle is discharged, resulting in discharged molding material.

[0120] In certain cases, it is preferred that one, several, or all cycles of the molding material cycle include additional steps and / or that individual steps have additional features. Details of this can be found in the following description, as well as the appended claims and drawings.

[0121] During the production of the molding material, particularly in step (1) of the molding material cycle, the prepared molding material and the additives are preferably mixed. The additives preferably also include water.

[0122] Preferably, before separation in step (4), the mold with the casting and - if present - the at least one core is cooled.

[0123] Preferably, the cast molding material is cooled before processing.

[0124] Reprocessing typically involves extensive removal of metal residues and other contaminants, such as impurities from the casting process (core marks, riser residues, etc.), and comminution of the cast molding material (grain separation). Thermal, mechanical, and possibly chemical stress produce wear products such as sand fines, inactive clay particles, decomposition products of additives and / or lustrous carbon formers, or conversion products of core binders, as well as oolite grains of the molding base material.

[0125] To prevent such wear products from accumulating in the molding material cycle and / or to negatively influence the molding material properties and / or to prevent the required active proportions of the binder (smectite-containing clay) and of the additive to be used according to the invention from decreasing too much, additives are added to the molding material in a subsequent cycle, in particular in step (1), during the production of the molding material, i.e. the processed molding material is refreshed by the additives. To keep the mass of the molding material circulated constant, a corresponding amount of molding material is removed from the molding material cycle. This can take place before refreshing with the additives (in particular in step (5)), or after refreshing with the additives, i.e. after the molding material has been produced in a later cycle. In the latter case, the amount of additives added is kept as low as possible.

[0126] In some cases, step (5) therefore comprises the necessary discharge of cast molding material in the same amount as in step (1) of the next cycle, which is refreshed by additives comprising the additive to be used according to the invention; thus, it is possible to achieve a uniform property profile.

[0127] Preferably, in step (5) 0.5 wt% to 20 wt%, preferably 2 wt% to 15 wt%, particularly preferably 5 wt% to 10 wt% of the cast molding material is discharged (sand discharge) and in step (1) of the following cycle a corresponding amount of additives is added in order to keep the mass of the molding material circulated in the circuit constant.

[0128] If part of the cast molding material has not already been discharged in step (5), in order to keep the mass of the circulated molding material constant, 0.5 wt% to 20 wt%, preferably 2 wt% to 15 wt%, particularly preferably 5 wt% to 10 wt% of the molding material produced in step (1) is discharged.

[0129] The molding material cycle to which the process according to the invention relates preferably comprises at least 10 cycles, preferably at least 15 cycles, particularly preferably at least 30 cycles. The additive defined above is preferably added in each cycle of the molding material cycle.

[0130] The additive to be used according to the invention (as defined above) is preferably free-flowing and / or pourable. The additive is preferably in the form of a powder or granules. The additive is particularly preferably in the form of particles with a grain size of 20 μm to 200 μm, determined by laser granulometry.

[0131] The proportion of dehydratable inorganic compounds that release water at a temperature of 150°C or more is preferably 1% to 100%, based on the total mass of the additive as defined above. More preferably, the proportion of dehydratable inorganic compounds that release water at a temperature of 150°C or more is 20% to 100%, based on the total mass of the additive as defined above. Most preferably, the proportion of dehydratable inorganic compounds that release water at a temperature of 150°C or more is 30% to 100%, based on the total mass of the additive as defined above. Most preferably, the proportion of dehydratable inorganic compounds that release water at a temperature of 150°C or more is 50% to 100%, based on the total mass of the additive as defined above.

[0132] In certain cases, it is preferred that the additive to be used according to the invention contains, in addition to the said dehydratable inorganic compound(s), one or more components from the group consisting of inorganic carbonates

[0133] Lustrous carbon formers

[0134] It is clear to the person skilled in the art that the amount of carbon added to the molding material via the additive must be limited so that the concentration of carbon in the molding material is not higher than 1.5%.

[0135] The additive preferably contains aluminum hydroxide, whereby the aluminum hydroxide contained in the additive can have a water content in the range of 0.01% to 20%, preferably 0.01% to 12%. Particular preference is given to aluminum hydroxides with a water content of less than 1% (i.e., less than 1% water content), determined by thermogravimetric analysis in the temperature range up to 105°C. Therefore, no special effort is required to dry the aluminum hydroxide. The additive can contain aluminum hydroxide in a mixture with iron oxide and / or iron hydroxide, with the proportion of aluminum hydroxide being greater than 40%, based on the total mass of aluminum hydroxide, iron oxide, and / or iron hydroxide.

[0136] The additive to be used according to the invention preferably has a pH in the range of 7 to 14, determined according to DIN 19747:2009-07 (sample preparation), DIN EN 12457-1:2003-01 (leaching) and DIN EN ISO 10523:2012-04 (determination of the pH value).

[0137] The additive to be used according to the invention preferably contains one or more dehydratable inorganic compounds which release water in a temperature range from 150 °C to 850 °C.

[0138] Preferably, the total proportion of elements from the group consisting of Pb, Cd, Cr, Co, Cu, Mo, Ni, Hg, Se, Zn, P, As, F, Br and C1 is 1% by weight or less, preferably 0.5% by weight or less, particularly preferably 0.1% by weight, most particularly preferably 0.05% by weight, based on the total mass of the additive.

[0139] When producing the molding material (step (1)), the order in which the individual components are put together is flexible.

[0140] For example, the aggregates can be provided as a mixture.

[0141] Alternatively, the additive and smectite-containing clay can be provided as a mixture, and the other additives separately. This approach corresponds to the current practice of providing lustrous carbon formers in a pre-mixed mixture with smectite-containing clay. This allows existing storage and metering facilities in the foundry to continue to be used.

[0142] Alternatively, the additive can be provided separately from the other aggregates.

[0143] Alternatively, the additive and optionally the smectite-containing clay, or a premix of additive and smectite-containing clay, can first be mixed with the first prepared molding material, and then further raw materials are added as described above. Preferably, the total mass of the added raw materials from the group consisting of

[0144] Mould base material, second processed mould material produced by processing moulds and / or cores and / or parts thereof cast outside the mould material cycle, third processed mould material produced by processing mould material from uncast moulds and / or cores and / or parts thereof,

[0145] 0.5 to 10 wt%, preferably 1 to 8 wt%, particularly preferably 1.5 to 7 wt%, based on the total mass of the molding material to be produced.

[0146] The mass of the smectite-containing clay additive is preferably 0.1 to 1.5 wt%, more preferably 0.3 to 1.2 wt%, particularly preferably 0.5 to 1 wt%, based on the total mass of the molding material to be produced.

[0147] The total mass of the dehydratable inorganic compounds added as an aggregate with the additive (as defined above), which release water at a temperature of 150 °C or more, is 0.1 to 1 wt%, preferably 0.3 to 0.8 wt%, particularly preferably 0.4 to 0.7 wt%, based on the total mass of the molding material to be produced.

[0148] The smectite-containing clay to be used in the process according to the invention is preferably a bentonite selected from the group consisting of sodium bentonite, calcium bentonite and mixtures thereof.

[0149] The mold base material is preferably selected from the group consisting of quartz sand, olivine sand, chromium ore sand, zircon sand, and artificially produced ceramic sands, and mixtures of these sands. Typically, a mold contains at least 40% sand, preferably over 50% sand, more preferably over 60% sand, and most preferably over 70% sand.

[0150] In one embodiment of the process, casting takes place in the earlier cycle in a mold with at least one inserted core. The cast molding material resulting from the earlier cycle of the molding material cycle, and the resulting first processed molding material, thus contain material from at least one cast mold and from at least one cast core, which were cast in the same casting process. The material from the cast core comprises reaction products of the binder formed during casting.

[0151] Cores used in clay-bonded molds are typically not clay-bonded. Typically, such cores are made with an organic binder, such as a phenolic resin or a cold-box binder, or with a non-clay inorganic binder, such as a binder containing water glass.

[0152] In this embodiment of the method according to the invention, a second recycled molding material can be used, which contains material from uncast molds and / or cores and / or parts thereof, and / or a third recycled molding material, which contains material from cast molds and / or cores and / or parts thereof, wherein the molds and cores can each be produced with an organic binder, e.g. a phenolic resin or a cold-box binder, or with an inorganic binder containing no clay, e.g. a binder containing water glass. In these cases, the molding material produced in the later cycle of the molding material cycle therefore contains used core sand.

[0153] In this embodiment of the process according to the invention, an additive comprising aluminum hydroxide is preferably used, wherein the proportion of aluminum hydroxide is at least 80%, preferably at least 90%, and particularly preferably at least 95%, most preferably 99%, based on the total mass of aluminum hydroxide and magnesium hydroxide in the additive.

[0154] If the molding material produced in the later cycle contains carbon, at least 70 wt%, preferably at least 80 wt%, and more preferably at least 90 wt%, most preferably at least 95% of the carbon comes from the organic binder of cast and uncast cores.

[0155] In another embodiment of the method according to the invention, casting takes place in the earlier cycle in a mold without an inserted core, so that the first prepared molding material does not contain any material from cast cores.

[0156] The second processed molding material used for this embodiment of the method according to the invention is preferably produced by processing molding material exclusively from uncast clay-bonded molds and / or cores and / or parts thereof. The third processed molding material used for this embodiment of the method according to the invention is preferably produced by processing molding material exclusively from clay-bonded molds and / or cores and / or parts thereof cast outside the considered molding material cycle.

[0157] In this embodiment of the process according to the invention, an additive comprising one or both compounds from the group consisting of aluminum hydroxide and magnesium hydroxide is preferably used, wherein the proportion of magnesium hydroxide is 0 to 100%, based on the total mass of aluminum hydroxide and magnesium hydroxide in the additive.

[0158] Preferably, the process is designed such that at least 90% by weight of the molding material is exposed to a temperature of at most 1000 °C during casting in step (3). At temperatures above 1000 °C, aluminum hydroxide is irreversibly converted into corundum (α-aluminum hydroxide), which cannot be converted back into aluminum hydroxide in a later cycle upon addition of water in step (1) and is therefore no longer capable of acting as an additive according to the invention as defined above.

[0159] The process is preferably designed such that, during casting, no more than 50 wt.%, preferably no more than 25 wt.%, particularly preferably no more than 10 wt.% of the aluminum hydroxide contained in the mold is converted into corundum. The lower the proportion of aluminum hydroxide converted into corundum, the greater the proportion of aluminum oxides (especially γ-aluminum oxide) that can be converted back into aluminum hydroxide upon addition of water in step (1).

[0160] A further aspect of the present disclosure relates to the use of the molding material defined above in a molding material cycle. The above statements apply to preferred molding materials.

[0161] A further aspect of the present disclosure relates to the use of the above-defined additive for producing a molding material according to the invention. The above statements apply to preferred additives. The invention is described in more detail below with reference to the attached schematic figures. Herein:

[0162] Fig. 1 a molding material cycle (casting in coreless form) according to the state of the art

[0163] Fig. 2 a molding material cycle (casting in coreless form) according to the method according to the invention

[0164] Fig. 3 a molding material cycle (casting in mold with core) according to the state of the art

[0165] Fig. 4 a molding material cycle (casting in mold with core) according to the method according to the invention

[0166] A cycle of a molding material cycle, wherein the mold cast in step (3) does not contain an inserted core, comprises, according to Fig. 1 and Fig. 2, at least the steps (1) to (5) as defined above.

[0167] In step (1) a molding material is produced comprising

[0168] (i) the first reprocessed molding material produced by reprocessing the cast molding material resulting from a previous cycle of the molding material cycle, which does not comprise material from cast cores, and

[0169] (ii) Aggregates.

[0170] The aggregates comprise one or more raw materials from the group consisting of fresh molding material (new sand), as well as at least one processed molding material from the group consisting of a second processed molding material produced by processing uncast molds and / or cores and / or parts thereof, a third processed molding material produced by processing molds and / or cores and / or parts thereof which are outside the area shown in Fig.

[0171] 1 and Fig. 2, respectively, were produced and cast,

[0172] Smectite-containing clay, preferably bentonite

[0173] Water.

[0174] The second processed molding material contains material from uncast cores and / or molds and / or parts thereof, and / or the third processed molding material contains material from cast cores and / or molds and / or parts thereof.

[0175] In the process not according to the invention (Fig. 1), at least one lustrous carbon former is added as a further additive in step (1) during the production of the molding material.

[0176] In the process according to the invention (Fig. 2), the additive defined above is added as a further additive in step (1) during the production of the molding material according to the invention. The additive preferably contains or consists of magnesium hydroxide and / or aluminum trihydroxide.

[0177] The addition of lustrous carbon formers is not completely excluded in the process according to the invention, but the amount of carbon added to the molding material must be limited so that the concentration of carbon in the molding material is not higher than 1.5%.

[0178] In step (2), a mold bonded with smectite-containing clay is produced from the molding material produced in step (1).

[0179] In step (3), a casting is produced by pouring the mold created in step (2). The mold does not contain any inserted cores.

[0180] In step (4), the casting produced in step (3) is separated from the mold, resulting in a cast mold material that includes material from a cast mold but no material from cast cores. Preferably, the mold containing the casting is cooled before separation in step (4).

[0181] In step (5), the cast molding material from step (4) is processed to obtain a first processed molding material for producing a new molding material in step (1) of a later, particularly the next, cycle. Preferably, the cast molding material is cooled before processing in step (5). During processing, a portion of the cast molding material may be removed, resulting in a removed molding material.

[0182] If part of the cast molding material has not already been discharged during processing in step (5), in order to keep the mass of the circulating molding material constant, part of the molding material produced in step (1) of the next cycle is discharged, resulting in discharged molding material.

[0183] In step (1) of a later, in particular the next cycle, the first processed molding material resulting in step (5) of the earlier, in particular the previous cycle, is used to produce a new molding material as described above.

[0184] A cycle of a molding material cycle, wherein the mold cast in step (3) contains at least one inserted core, comprises, according to Fig. 3 and Fig. 4, at least the steps (1), (1 a), (2), (2a), (3), (4) and (5) as defined above.

[0185] In step (1) a molding material is produced comprising

[0186] (i) a first reprocessed molding material produced by reprocessing the cast molding material resulting from a previous cycle of the molding material cycle, which comprises material from cast cores and

[0187] (ii) Aggregates.

[0188] The additives comprise one or more raw materials from the group consisting of fresh molding material (new sand), as well as at least one processed molding material from the group consisting of a second processed molding material produced by processing uncast molds and / or cores and / or parts thereof, a third processed molding material produced by processing molds and / or cores and / or parts thereof that were produced and cast outside the molding material cycle shown in Fig. 3 or Fig. 4,

[0189] Smectite-containing clay, preferably bentonite

[0190] Water.

[0191] In the process not according to the invention (Fig. 3), at least one lustrous carbon former is added as a further additive in step (1) during the production of the molding material.

[0192] In the process according to the invention (Fig. 4), the additive defined above is added as a further additive in step (1) during the production of the molding material according to the invention. The additive preferably contains or consists of aluminum trihydroxide.

[0193] The addition of lustrous carbon formers is not completely excluded in the process according to the invention, but the amount of carbon added to the molding material must be limited so that the concentration of carbon in the molding material is not higher than 1.5%.

[0194] In step (1 a), a molding material for producing at least one core (core molding material) is produced or provided. This molding material comprises a molding base material, a clay-free binder, and optionally additives. Suitable additives for molding materials for producing cores are known from the prior art. The binder is an organic binder, e.g., a phenolic resin or a cold-box binder, or a clay-free inorganic binder, e.g., a binder containing water glass.

[0195] In step (2), a mold bound with smectite-containing clay is produced from the molding material produced in step (1).

[0196] In step (2a), at least one core is produced from the molding material (core molding material) produced or provided in step (1 a) and inserted into the mold produced in step (2).

[0197] In step (3), a casting is produced by pouring the mold produced in step (2) which contains at least one inserted core.

[0198] In step (4), the casting produced in step (3) is separated from the mold, resulting in a cast molding material which comprises material from the cast mold and material from the cast core. Preferably, the mold with the casting is cooled before separation in step (4). In step (5), the cast molding material from step (4) is processed to obtain a first processed molding material for producing a new molding material in step (1) of a later, in particular the next, cycle. Preferably, the cast molding material is cooled before processing in step (5). During processing, some of the cast molding material is possibly discharged, resulting in a discharged molding material.

[0199] If part of the cast molding material has not already been discharged during processing in step (5), in order to keep the mass of the molding material in the circuit constant, part of the molding material produced in step (1) of the next cycle is discharged, resulting in discharged molding material.

[0200] In step (1) of a later, in particular the next cycle, the first processed molding material resulting in step (5) of the earlier, in particular the previous cycle, is used to produce a new molding material as described above.

[0201] The invention is further described below by means of non-limiting examples.

[0202] 0. Test methods and molding materials

[0203] 0.1 Test methods

[0204] The following test methods (measurement methods) were used (Table 1)

[0205] Table 1: Measurement methods used

[0206] Sleeve and rib model devices are manufactured as described in (https: / / www.researchdisclosure.com / database / RD705032) and used in the following experiments.

[0207] 0.2 Materials used All information on raw material dosages refers to the pure raw material, i.e. as dry materials, i.e. without any moisture or hydration water that may be present.

[0208] As part of the investigations, a molding material (hereinafter also referred to as the starting molding material) from the conditioned molding material recycling system of a brake disc foundry was used as the starting material for experiments on converting molding material recycling systems containing lustrous carbon formers. The molding material can be described by the following data (Table 2). Table 2: Parameters of the starting molding material

[0209] For the experimental investigations, processed molding materials from core sands were used (second processed molding material as defined above). Cores were produced with an organic binder or an inorganic binder and then grated through a circular vibrating screen from Webac.

[0210] The starting material for a molding material produced with an organic binder is cores produced using the cold box process using the binder Biocure 8568P1 / Silcure 8431 P2 distributed by Hüttenes-Albertus Chemische Werke GmbH on a Laempe LL20 core shooter. For this purpose, a type H32 sand from Quarzwerke was used, and 0.7 parts by weight of the binder components were dosed to 100 parts by weight of sand. The cores were produced at a shooting pressure of 450 kPa (4.5 bar) and a shooting time of 1.5 seconds. Then, for 45 seconds at a gassing pressure of 200 kPa (2 bar), they were cured by flowing 10 g of dimethylpropylamine (N,N-dimethylpropylamine, catalyst GH6 from Hüttenes-Albertus Chemische Werke GmbH).The starting material for a molding material produced with an inorganic binder are cores that are produced using the Cordis 9477 / Anorgit 9476 binder system distributed by Hüttenes-Albertus Chemische Werke GmbH on a LL20 core shooter from Laempe. For this purpose, a type H32 sand from Quarzwerke is used, and 2.2 parts by weight of Cordis 9477 and 1.15 parts by weight of Anorgit 9476 of the binder components are dosed to 100 parts by weight of sand. The cores are produced with a shooting pressure of 450 kPa (4.5 bar) and a shooting time of 1.5 seconds in a core box heated to 180 °C. To cure, the cores are blown through with hot air at 120 °C at a pressure of 200 kPa (2 bar) for 1 minute.

[0211] The cores are grated using a circular vibrating screen (circular vibrating screen - 175056 test system, Webac). The resulting molding material has the properties shown in Table 3.

[0212] Table 3: Parameters of the processed molding materials from core sands

[0213] The abbreviation NG indicates that the measured values ​​are below the detection limit. The starting material for cores which do not disintegrate under the test conditions (i.e. cores which do not disintegrate during separation (step (4)), see below, point 3, test series A) is quartz sand of the type HAP 0.20 / 0.315 / 0.40 from HA Polska and an inorganic binder consisting of water glass of the type Steinex 48 / 50 Hüttenes-Albertus Chemische Werke GmbH in combination with Silica Fume Q1 -Plus from RW Silicium. 100 parts by weight of quartz sand were mixed with 1.1 parts by weight of Silica Fume Q1 -Plus and 3.4 parts by weight of Steinex48 / 50 and the mixture was shaped into the core in a loose core box. The core was then gassed with 100°C hot CO2 for 60s in a Morek laboratory core shooter at a gassing pressure of 150 kPa (1.5 bar) and thus cured.

[0214] 1 . Screening tests to identify suitable additives

[0215] 6 kg of quartz sand (H32, Quarzwerke) are mixed with 120 ml of water in a mixer (LM-2e pan mill mixer, Morek MULTISERW) for 2 minutes at a speed of 40 rpm. Then, 0.48 kg of bentonite (dry weight) (Natroben 25F, Clariant) and 0.30 kg of additive (dry weight) are added and mixed for 7 minutes at a speed of 40 rpm. The resulting mixture is sieved by hand through a sieve with a mesh size of 3 mm, and the compactability (VDK) of the material is determined (testing device type: PVG; ID No.: 1501, year of manufacture: 2000). If the VDK is greater than 46.0%, the mixture is sieved again and the VDK measurement is repeated. This process is repeated until the VDC is below 46.0%. If the VDC is less than 44.0%, 7-12 ml of water is added and mixed again for 1 minute, followed by sieving and VDC measurement.The addition of water is repeated until the VDK is above 44.0%.

[0216] As a reference for the molding material properties, 3 different mixtures with lustrous carbon formers according to the state of the art are used:

[0217] 1) a commercially available premix of 25% lustrous carbon former (“sea coal”) and 75% sodium bentonite (NEMIR 2575) from HA Italia SpA

[0218] 2) 5 parts by weight of coke flour (metallurgical coke) from LuxCarbon GmbH as lustrous carbon former and 8 parts by weight of bentonite (Natroben 25F, Clariant)

[0219] 3) 5 parts by weight of Carboluxon 100 / P from Hüttenes-Albertus France as a commercially available lustrous carbon former and 8 parts by weight of bentonite (Natroben 25F, Clariant). In addition to the mold material properties, the casting quality is also a decisive criterion for selecting suitable additives. For this purpose, i.e., to check the casting quality, castings are made using the sleeve pattern device described in (https: / / www.researchdisclosure.com / database / RD705032). This involves casting molds manufactured according to the sleeve pattern device described in (https: / / www.researchdisclosure.com / database / RD705032). The castings are then blasted, and the surface roughness is measured according to DIN EN ISO 4287 (R_ISO).Two castings were examined, with the surfaces measured three times each with a small, medium, and large spacing of the star-shaped ribs using a Mitutoyo SJ-500P surface measuring device over a measuring distance of 8 mm. No consistent trend could be determined with regard to the spacing of the ribs and the surface roughness; therefore, to simplify the evaluation, the average value of all measurements was used. This showed that the surface roughness of all castings obtained was within a range that allows for commercial use.

[0220] 1 .1 Various types of aluminum hydroxide and magnesium hydroxide as additives

[0221] For the investigation of aluminum hydroxides, AI(OH)3 of type SH500 (SH500 nuance-00, Alteo) and type SH950 (SH950 nuance-00, Alteo) are used.

[0222] For the investigation of magnesium hydroxides, Brucite Type 1, Brucite Type 2 and Brucite Type 3 from Ziegler & Co. GmbH are used (Table 4, all values ​​according to Ziegler's technical data sheet dated 10 / 2020).

[0223] Table 4: Parameters of the brucite types used as additives

[0224] Table 5 shows the mold material properties and the roughness of the casting when using various hydroxides and the lustrous carbon formers 1) to 3) used as reference. Dry compressive strengths (TDF) of <35 N / cm are considered particularly positive. 2 and water contents of <2.8%, while dry compressive strengths of >50 N / cm 2 are considered negative, as are water contents of >3.2%. Hydroxides, especially aluminum hydroxide AI(OH)3 and magnesium hydroxide Mg(OH)2, enable the production of molds and exhibit good molding material properties (see Table 5).

[0225] Table 5: Mould material properties and flatness of the casting when using different hydroxides or lustrous carbon formers as additives

[0226] 1 .2 Investigation of aluminum hydroxide AKOHh as an additive with addition of lustrous carbon formers

[0227] The good values ​​for hydroxides, especially aluminum hydroxide Al(OH)3, can be further improved by adding lustrous carbon formers such as Carboluxon 100 / P, see Table 6. In particular, the surface roughness of the castings is reduced by using Carboluxon 100 / P, although the values ​​obtained using pure aluminum hydroxide are also sufficient. Table 6: Mold material properties and flatness of the casting when using Al(OH)3

[0228] SH 950 as additive with addition of lustrous carbon former Carbo luxon 100 / P 1 .3 Investigations of various carbonates as comparison additives

[0229] While huntite (trade name UltraCarb D98, supplied by LKAB Minerals) does not achieve sufficiently good molding material values, dolomite and manganese carbonate (supplied by TROPAG GmbH) show quite acceptable molding material values ​​(Table 7).

[0230] The dolomites used were Bianco Zandobbio 0 / 50 micron from Ziegler and PE-DOL 90 from Possehl Erzkontor. Overall, the molding material properties are somewhat worse than those using the hydroxides described above. Nevertheless, the values ​​allow the materials to be used as a replacement for traditional lustrous carbon formers. However, carbonates have the disadvantage of containing carbon.

[0231] Table 7: Moulding material properties when using various carbonates or lustrous carbon formers as additives

[0232]

[0233] The mold material properties can be improved by mixing the carbonates with hydroxides (Table 8). MixMag is a 50% / 50% mixture of brucite (93% Mg(OH)2) with raw magnesite (92% MgCO3), which was purchased from Possehl Erzkontor GmbH & Co. KG, and Dolomag is a 50% / 50% mixture of brucite (93% Mg(OH)2) and dolomite (95% CaMg(CO3)2), which was also purchased from Possehl Erzkontor.

[0234] Table 8: Mold material properties and flatness of the casting when using different carbonate-hydroxide mixtures

[0235] If a state-of-the-art lustrous carbon former such as Carboluxon 100 / P is added to a mixture of hydroxide and carbonate, the molding material values ​​can be further improved (Table 9).

[0236] Table 9: Moulding material properties when using various carbonate-hydroxide mixtures with the addition of Carboluxon 100 / P as lustrous carbon former

[0237] 1 .4 Emissions from the bentonite and additives used

[0238] Table 10 shows emission measurements of the bentonite and additives used. The emission measurements were conducted at the Foundry Institute of the University of Freiberg. The materials were placed in a tube furnace at 900°C, and the resulting emissions were measured using online FT-IR. Calibration was performed using test gases.

[0239] The emissions of the additives used according to the invention are significantly lower than those of conventional lustrous carbon formers, such as the coke meal from LuxCarbon described above or the product Carboluxon 100 / P. Carbonates (not according to the invention) such as manganese carbonate reduce emissions of hydrocarbons, especially benzene, toluene, and xylene, but, as expected, lead to significantly increased CO2 emissions compared to hydroxides such as Al(OH)3. According to the invention, carbonates are therefore preferably used in combination with hydroxides. Table 10: Results of emission measurements using different additives (all data in mg / kg, i.e., mg of the respective emission per kg of material)

[0240] 2. Production and testing of molding materials in the cycle

[0241] The goal of these experiments is to cast and recycle a specific amount of molding material several times. As is common practice in industrial foundries, the molding material is recycled. During each reprocessing of the molding material, additives are added, which increase with each cycle. Components present in the initial molding material but no longer added decrease, i.e., the proportions of components that are no longer added in subsequent cycles decrease. The total amount of molding material in the cycle remains constant at approximately 8 kg. Two molds are produced and cast per cycle according to the sleeve pattern setup described in (https: / / www.researchdisclosure.com / database / RD705032).

[0242] To illustrate the test procedure, reference is made to the molding material cycle in Fig. 2.

[0243] The cycles of the molding material cycle include the following steps:

[0244] Production of the molding material (step (1), first cycle)

[0245] Test series 2.1 , 2.2.1 , 2.2.2, 2.3.1 , 2.3.2 as described below

[0246] In the first cycle, 6 kg of quartz sand, type H32, from Quarzwerke is used. The mold base material is then mixed with 480 g of sodium bentonite (Natroben 25F, HA ITALIA SpA, a Na bentonite produced by activating a natural Ca bentonite), 300 g of the respective additive, and 120 ml of water in a Morek Multiserw pan mill mixer for 1 minute without water, and then mixed again 7 minutes after the water has been added. To do this, the mold base material is first mixed with 120 ml of water in a Morek Multiserw pan mill mixer for 1 minute, and then, after adding 480 g of sodium bentonite (Natroben 25F, HA ITALIA SpA) and 300 g of the respective additive, mixed again for 7 minutes in a Morek Multiserw pan mill mixer. - M -

[0247] Test series 2.4-2.6 as described below

[0248] In the first cycle, 3.7 kg of quartz sand type H32 from Quarzwerke are used. The mold base material is then mixed with 322 g of Volclay (GEKO™ V foundry bentonite from Clariant Deutschland GmbH, a naturally occurring sodium bentonite), 207 g of the respective additive, and 130 ml of water in a Morek Multiserw pan mill mixer for 1 minute without water, and then mixed again 7 minutes after the water has been added. To do this, the mold base material is first mixed with 130 ml of water in a Morek Multiserw pan mill mixer for 1 minute, and then mixed again for 7 minutes after the water has been added in a Morek Multiserw pan mill mixer. After adding 322 g of Volclay and 207 g of the respective additive, the mixture is mixed again for 7 minutes in a Morek Multiserw pan mill mixer.

[0249] The following statements apply to all test series 2.1 to 2.6 (unless otherwise stated).

[0250] During each molding material production (step (1)), additives are added, which increase with each cycle. By removing a portion of the cast molding material in step (5) or in step (1) of the next cycle (see Figure 2), the proportion of components that are present in the initial molding material but are no longer added decreases.

[0251] Making the mold (step (2) in all cycles)

[0252] For this purpose, the molding material is poured into the mold of the sleeve pattern device 3 minutes after mixing and compacted in two pressing processes (filling, pressing, refilling, pressing). The process is completed in another 3 minutes. Two molds are produced per test.

[0253] Drain (step (3) in all cycles)

[0254] After a 30-minute waiting period, the molds are poured one after the other. The mold is poured with liquid metal of the GJL 250 alloy at 1450 °C using a ladle. The poured mold is left to stand overnight until separation. The casting cools during this time, and the mold material first heats up and cools overnight in the mold. Separation (step (4) in all cycles)

[0255] The casting and the cast molding material are separated.

[0256] Processing (step (5) in all cycles)

[0257] The molding material is poured into a storage container, and the molding material lumps are crushed. Metal residues are removed.

[0258] Production of the molding material (step (1) in the 2nd and each subsequent cycle)

[0259] A new molding material is produced by refreshing the processed molding material from the previous cycle (first processed molding material) by adding bentonite, water, additive (as defined above) and fresh molding material (new sand) or a second processed molding material produced by processing cores (see below for details).

[0260] Fresh mold base material or a second processed mold material, produced by processing cores (see below for details), is added to the processed mold material from the previous cycle and mixed with 120 ml of water for 1 minute, and then after adding sodium bentonite (Natroben 25F, HA ITALIA SpA, test series 2.1, 2.2.1, 2.2.2, 2.3.1, 2.3.2) or Volclay (foundry bentonite GEKO™ V from Clariant Deutschland GmbH, test series 2.4, 2.5 and 2.6) and the respective additive (see below for quantities of bentonite and additive), the mixture is mixed again for 7 minutes on a Morek Multiserw pan mill mixer.

[0261] The increase in the quantity of molding material due to additions in the mixer, ie the increase in the quantity of molding material resulting from the addition defined above, is regulated by removing the same quantity of ready-mixed molding material in each cycle.

[0262] During each production (step (1)) of the molding material, additives are added, which accumulate with each cycle. By discharging a portion of the cast molding material, the proportion of components present in the initial molding material, but no longer added in subsequent cycles, decreases. 2.1 Additive Al(OH)3 or Mg(OH)3 when adding fresh molding material in subsequent cycles.

[0263] Ten cycles (0-9) are carried out using the sleeve model device described in (https: / / www.researchdisclosure.com / database / RD705032), whereby the first test is carried out with 100% fresh mold base material of type H32 from Quarzwerke.

[0264] In all subsequent cycles 1 to 9, 4 kg of the used molding material from the previous casting is used and refreshed with 400 g of mold base material (fresh mold base material), as well as 64 g of bentonite and 20 g of the respective additive.

[0265] The aluminum hydroxide additive used is SH950 nuance-00 from Alteo. The results of the tests with AI(OH)3 are presented in Table 11.

[0266] Brucite Type 3 from Ziegler & Co. GmbH is used as the magnesium hydroxide additive Mg(OH)2. The results of the tests with Mg(OH)2 are presented in Table 12.

[0267] Both additives show good molding properties and a comparable surface quality when using fresh mold base material as additive (see Figure 2, step (1)), which can be seen from the measured roughness of the castings.

[0268] Al(OH)3 as an additive results in a higher active clay content and significantly lower loss on ignition. For both Al(OH)3 and Mg(OH)2, the mold material properties and the castings are of good quality. The surface roughness of the castings is correspondingly low.

[0269] Table 11 : Characteristic values ​​of samples taken in the respective cycles to determine the mold material properties with AljOHjs as additive, and surface roughness of the casting

[0270] Table 12: Characteristic values ​​of samples taken in the respective cycles to determine the mold material properties with Mg(OH)2 as an additive, and surface roughness of the casting

[0271] 2.2 Al(OH)3 and MqfOHh when adding ColdBox core sand in the subsequent cycles. 31 cycles (0-30) are carried out using the sleeve model device described in (https: / / www.researchdisclosure.com / database / RD705032). The test procedure and measurement of the molding material and casting properties are carried out as described in Chapter 2.1, but in the subsequent cycles, a second prepared molding material (see Fig. 2, step (1)) prepared by preparing uncast cores is added instead of fresh molding material.

[0272] (For the proportion of the produced molding material, see Tables 13 and 16, respectively), which were produced with cold-box binder ("cold-box core sand"). 2.2.1 Aluminum hydroxide AKOHh when adding cold-box core sand in the following cycles

[0273] When using aluminum hydroxide AI(OH)3, the molding material properties with a 5% ColdBox core sand additive are so stable that, starting in cycle 15, the additive is increased to 10% ColdBox core sand (Tables 13 and 14). The molding material properties remained stable.

[0274] Table 13: Composition and compactability of the molding material mixture in the individual cycles

[0275]

[0276] Table 14: Characteristic values ​​of samples taken in the respective cycles

[0277] The CNS analysis data of the mold materials from the various cycles show an increase in the carbon and nitrogen content resulting from the addition of cold-box core sand. The surface roughness of the castings is improved compared to the test series with the addition of new sand (see 2.1 above) instead of cold-box core sand; this can be attributed to the addition of core sand (Table 15).

[0278] Table 15: CNS analysis of selected cycles and surface roughness of the corresponding castings

[0279] (1) The abbreviation NG indicates that the measured values ​​are below the detection limit 2.2.2 MqfOHh when adding ColdBox core sand in the following cycles

[0280] With magnesium hydroxide Mg(OH)2 in the form of brucite type 3 as an additive, it becomes apparent after just a few cycles that the properties of the molding material cannot be maintained at a stable level. Therefore, the bentonite content of the molding material is increased in cycles 8 and 14 (Table 16). Nevertheless, the molding material properties do not stabilize (Table 17). In particular, the wet tensile strength decreases with increasing cycles, and this trend can only be counteracted in the short term by adding more fresh bentonite.

[0281] Table 16: Composition and compactability of the molding material mixture in the individual cycles

[0282]

[0283] Table 17: Characteristic values ​​of samples taken in the respective cycles

[0284] As expected, the carbon content and, to a limited extent, the nitrogen content of the molding material increase with the addition of ColdBox core sand (Table 18). The surface roughness of the castings is good and not negatively affected. However, in contrast to aluminum hydroxide Al(OH)3 (see test series 2.2.1 above), magnesium hydroxide Mg(OH)2 does not allow for a molding material cycle with stable molding material properties when organic core sand is used (i.e., ColdBox core sand, see above) (Table 17).

[0285] Table 18: CNS analysis of selected cycles and surface roughness of the corresponding castings

[0286] (1) The abbreviation NG indicates that the measured values ​​are below the detection limit 2.3 AI(OH)3 and MgfOHh when adding inorganically bound core sand to the

[0287] Subsequent cycles

[0288] 31 cycles (0-30) are conducted using the sleeve model facility described in (https: / / www.researchdisclosure.com / database / RD705032). The test procedure and measurement of the molding material and casting properties are carried out as described in Chapter 2.1. However, in subsequent cycles, instead of fresh molding material, a second prepared molding material (see Fig. 2, step (1)) is added. This second prepared molding material is prepared by processing uncast cores (for the proportion of the produced molding material, see Tables 19 and 22) that were produced with an inorganic binder (water glass) ("1OB core sand"). This is therefore an inorganic molding material cycle with regard to all binders used.

[0289] 2.3.1 Aluminium hydroxide AKOHh as an additive when adding inorganically bound core sand in subsequent cycles

[0290] Even when adding lOB core sand, a molding material cycle with stable molding material properties is obtained when using aluminum hydroxide AI(OH)3, so that the addition of lOB core sand is increased to 10% from cycle 15 onwards (Tables 19 and 20).

[0291] Table 19: Composition and compactability of the molding material mixtures in the individual cycles Table 20: Characteristic values ​​of samples taken in the respective cycles

[0292] The molding material analyses (Table 21) show that there is no significant accumulation of carbon, nitrogen, or sulfur in the molding material; C-containing (carbon-containing) components from the inorganic binder (such as surfactants) are of minor importance. The low C (carbon) load is one of the major advantages of this inorganic molding material cycle, as very low emissions are to be expected (see below). Despite the lower carbon content, the obtained surface roughness values ​​(Table 21) are very close to those of the tests with coldbox core sand aggregate (test series 2.2.1).

[0293] Table 21: CNS analysis of selected cycles and surface roughness of the corresponding castings

[0294] (1) The abbreviation NG indicates that the measured values ​​are below the detection limit

[0295] 2.3.2 Magnesium hydroxide MqfOHh with addition of inorganically bound

[0296] Core sand in the Folqe cycles

[0297] With magnesium hydroxide Mg(OH)2 in the form of brucite type 3 as an additive, it becomes apparent after just a few cycles that the properties of the molding material cannot be maintained at a stable level. Therefore, the bentonite content of the molding material is increased in cycles 8 and 15 (Table 22). Nevertheless, the molding material properties do not stabilize. In particular, the wet tensile strength decreases with increasing cycles, and this trend can only be counteracted temporarily by adding more fresh bentonite (Table 23).

[0298] Similar to the addition of ColdBox core sand (test series 2.2.2), the addition of Mg(OH)2 as an additive does not result in a molding material cycle with stable molding material properties. The water requirement of the mix increases significantly, and the other molding material parameters also show instability (Table 23). The water requirement of a molding material corresponds to the water content of the molding material mixture in its mold-correct state (target compactability). The active clay content and wet tensile strength show a significant decrease with increasing cycles. Although this can be compensated for by adding bentonite, overall the molding material cycle does not have stable molding material properties. Table 22: Composition and compactability of the molding material mixture in the individual cycles Table 23: Characteristic values ​​of samples taken in the respective cycles

[0299] Analysis of selected mold material samples (Table 24) shows a slight increase in carbon content for high cycle numbers, presumably due to the addition of bentonite; Ca bentonites are treated with carbonates during activation. The surface roughness of the castings is always acceptable, i.e., good to very good.

[0300] Table 24: CNS analysis of selected cycles and surface roughness of the corresponding castings (1) The abbreviation NG indicates that the measured values ​​are below the detection limit

[0301] 2.4 Additive AKOHh when adding fresh molding material in the following cycles

[0302] Eleven cycles (0-10) are carried out using the sleeve model device described in (https: / / www.researchdisclosure.com / database / RD705032), whereby the first test is carried out with 100% fresh mold base material of type H32 from Quarzwerke.

[0303] In all subsequent cycles 1 to 10, 3.7 kg of the used mold material from the previous casting is used and refreshed with 185 g of mold base material (fresh mold base material), 26 g of bentonite, and 23 g of the respective additive (Table 25). SH950 nuance-00 aluminum hydroxide from Alteo is used as the additive. Stable mold material properties were achieved (Table 26). Using fresh mold base material as the additive (see Figure 2, step (1)), good mold properties and a good to very good surface quality are achieved, which can be seen from the measured roughness of the castings. As expected, the CNS analysis after 11 cycles shows no significant carbon and nitrogen contents, since only inorganic materials were used (see Table 27).

[0304] Table 25: Composition and compactability of the molding material mixture in the individual cycles

[0305]

[0306] (1) The abbreviation NG indicates that the measured values ​​are below the detection limit

[0307] 2.5 AI(OH)3 when adding cold box core sand in the following cycles

[0308] Eleven cycles (0-10) were conducted using the sleeve model device described in (https: / / www.researchdisclosure.com / database / RD705032). The test procedure and measurement of the molding material and casting properties were carried out as described in Chapter 2.4. However, in subsequent cycles, instead of fresh molding material, a second prepared molding material (see Fig. 2, step (1)) was added. This second prepared molding material was prepared by processing uncast cores (for the proportion of the produced molding material, see Table 28) that had been produced with cold-box binder ("cold-box core sand"). Stable molding material properties were achieved (Table 29).

[0309] Table 28: Composition and compactability of the molding material mixture in the individual cycles

[0310] Table 29: Characteristic values ​​of samples taken in the respective cycles

[0311] The data of the CNS analysis of the molding material after 11 cycles shows, especially in comparison to the test series with new sand feed, significant carbon and nitrogen contents originating from the addition of ColdBox core sand (Table 30).

[0312] Table 30: CNS analysis of selected cycles and surface roughness of the corresponding castings

[0313] (1) The abbreviation NG indicates that the measured values ​​are below the detection limit

[0314] 2.6 AI(OH)3 when adding inorganically bound core sand in the following cycles

[0315] Eleven cycles (0-10) are conducted using the sleeve model facility described in (https: / / www.researchdisclosure.com / database / RD705032). The test procedure and measurement of the molding material and casting properties are carried out as described in Chapter 2.4. However, in subsequent cycles, instead of fresh molding material, a second prepared molding material (see Fig. 2, step (1)) is added. This second prepared molding material is produced by processing uncast cores (for the proportion of the produced molding material, see Table 31) that were produced with an inorganic binder (water glass) ("1OB core sand"). This is therefore an inorganic molding material cycle with regard to all binders used. Stable molding material properties were achieved (Table 32).

[0316] Table 31: Composition and compactability of the molding material mixtures in the individual cycles

[0317] The molding material analyses (Table 33) show that there is no significant accumulation of carbon, nitrogen, or sulfur in the molding material; C-containing (carbon-containing) components from the inorganic binder (such as surfactants) are of minor importance. The low C (carbon) load is one of the major advantages of this inorganic molding material cycle, as very low emissions are to be expected (see below). Despite the lower carbon content, the obtained surface roughness values ​​(Table 33) are comparable to those of the tests with coldbox core sand aggregate (test series 2.5).

[0318] Table 33: CNS analysis of selected cycles and surface roughness of the corresponding castings

[0319] (1) The abbreviation NG indicates that the measured values ​​are below the detection limit 3. Moulding material cycle with successive reduction of the carbon content in the moulding material

[0320] The goal of these experiments is to cast and reprocess a specific amount of prepared molding material several times, particularly with a gradual reduction in the carbon content of the molding material. As is common practice in industrial foundries, the molding material is recycled. During each reprocessing of the molding material, additives are added, which increase with each cycle. Components present in the initial molding material but no longer added decrease, i.e., the proportions of components that are no longer added in subsequent cycles decrease. The total amount of molding material remains constant at approximately 1,200 kg. Four molds are produced and cast per cycle according to the rib pattern setup described in (https: / / www.researchdisclosure.com / database / RD705032).

[0321] To illustrate the test procedure, reference is made to the molding material cycle in Fig. 4.

[0322] The cycles of the molding material cycle include the following steps:

[0323] Production of the molding material (step (1), first cycle)

[0324] In the first cycle, processed molding material (starting molding material) from the molding material cycle of a brake disc foundry is used (see point 0.2).

[0325] The prepared molding material is conveyed from a big bag into a hopper in front of the Eirich mixer (Eirich Intensive Mixer R09 with a capacity of 150 liters, max. 240 kg, batch operation under normal atmosphere) using a big bag unloading station and two conveyor belts. The previously weighed additives (additional materials) – bentonite, mold base or core material, and the additive – are added to the hopper discharge belt. Al(OH)3 type SH950 (SH950 nuance -00, Alteo) is used as the additive.

[0326] During each production (step (1), see Figure 4) of a molding material, additives are added that increase with each cycle. By discharging a portion of the cast molding material in step (5) or in step (1) of the next cycle (see Figure 4), the proportion of components that are present in the initial molding material but are no longer added is reduced. The molding material is withdrawn from the hopper and transported to the mixer together with the additives. The mixing process starts, water is dosed automatically, and after the mixing process is complete, the finished molding material is emptied from the mixer into a transport container. The transport container is transported to the molding line.The mixer program is selected between a mixing sequence without intermediate stops (Table 35) and a mixing sequence with intermediate stops (Table 34) depending on the situation (depending on the water content of the mix), and the desired compaction is set to 40% + / - 5% by monitoring the water content. The desired compaction is set by monitoring the compactability. Compactability changes with the water content of the molding material. The water content was determined for each mix. Since the necessary water addition to achieve the target compactability is unknown, the intermediate stop in the mixing sequence makes it easier to determine the required amount of water, and subsequent mixes can be produced without intermediate stops.

[0327] Table 34: Mixing process with intermediate stop Table 35: Mixing process without intermediate stop

[0328] Making the mold (step (2) in all cycles)

[0329] To do this, first fill a portion of the lower box of the mold with a layer of screened molding material from the transport container. Sufficient molding material is screened out so that the contour of the rib pattern is no longer visible (this corresponds to a height of 80 mm in the lower box and 50 mm in the upper box). Then, the remaining volume of the lower box is filled with unscreened molding material. The screen has a mesh size of 2 mm.

[0330] The lower box (i.e., the molding material in the lower box) is compacted in the HWS HSP-1 D molding system using a Seiatsu airflow compression molding process with the specified parameters (Table 36, mold box size of 700 x 500 x 200 / 200 mm, pattern plate size of 650 x 450 x 30 mm). The time during which an airflow is directed through the molding material in the mold box to fluidize it is referred to as the Seiatsu time. The Seiatsu time can be set independently for the cope and lower boxes. The molding material is then pressed.

[0331] Table 36: Compaction parameters

[0332] The lower box is pulled flat by hand and transported by crane to the loading station. The cope box is filled, compacted, pulled off, and transported in the same way. A previously manufactured core (step (1a), see Fig. 4) is inserted into the lower box (step (2a), see Fig. 4). The mold is loaded, clamped, and transported to the casting station.

[0333] Drain (step (3) in all cycles)

[0334] The mold is cast with liquid metal of the alloy GJL 250 at 1450 °C using a pouring ladle in a support iron with one-sided shears.

[0335] The next molds are made (step (2), (2a)) and cast.

[0336] The cast mold is left to stand for four hours before separation. During this time, the casting cools and the mold material heats up.

[0337] Separation (step (4) in all cycles)

[0338] The upper and lower boxes are opened. The casting and the poured molding material are separated. In the three molding material cycles investigated, the core sand is handled differently:

[0339] 1. In test series A, in which new sand is used as the added molding material, a core bonded with CO2-hardened water glass (see point 0.2 above) is used, which does not disintegrate during separation and is completely removed at this point in the cycle.

[0340] 2. In test series B, in which ColdBox cores were used, the core completely disintegrated in the center and could no longer be separated from the molding material. The core marks do not disintegrate and cannot be easily crushed. Therefore, the core marks are removed at this point in the cycle. 3. In test series C, in which inorganically bonded cores (binder Cordis 9477 / Anorgit 9476, see section 0.2) were used, these only disintegrated in the surface layer but could be easily crushed by hand. Therefore, the IOB core sand is not removed.

[0341] Processing (step (5) in all cycles)

[0342] The molding material is spread out on the floor and lumps are crushed with a shovel. The meta-urea residue is removed. The molding material is left on the hall floor to cool for at least three hours. After cooling, the molding material is scooped back into a big bag.

[0343] Production of the molding material (step (1) in the 2nd and each subsequent cycle)

[0344] A new molding material is produced by refreshing the prepared molding material from the previous cycle (first prepared molding material) by adding bentonite, water, an additive (as defined above), and fresh molding material (new sand, test series A) or a second prepared molding material produced by preparing cores (test series B and C, see below for details). For the mixing process, see the information above for step (1) of the first cycle.

[0345] The increase in the quantity of molding material due to additions in the mixer, ie the increase in the quantity of molding material resulting from the addition defined above, is regulated by removing the same quantity of ready-mixed molding material in each cycle.

[0346] During each molding process (step (1)), additives are added, which increase with each cycle. By removing a portion of the cast molding material, the proportion of components present in the initial molding material but no longer added in subsequent cycles decreases.

[0347] 3.1 Test series with addition of fresh moulding material (new sand) in step (1) (Test series A)

[0348] When manufacturing the mold (see step (2)), water glass-bonded cores are used, which do not disintegrate after casting (see point 0.2 above) and are removed as described above in step (4). In a test series with 30 cycles (A1-A30, see Table 37), the prepared molding material from the previous cycle (first prepared molding material) is refreshed in each subsequent cycle with molding material of the type Grudzen Laz. 0.20 / 0.315 / 0.40 (coarse quartz sand of class 1 K) from Quarzwerke. Table 37: Composition and compactability of the molding material mixture in the individual cycles

[0349] (1) “First recycled moulding material” refers here to the quantity of moulding material from the previous cycle that was reused after recycling

[0350] (2) Addition of water

[0351] (3) Measured water content of the mixture Table 38: Characteristic values ​​of samples taken in the respective cycles to determine the molding material properties

[0352] Table 39: Analysis of samples from individual cycles

[0353] As expected, a gradual decrease in the loss on ignition of the samples can be observed, as the number of cycles decreases in the organic material in the molding material. This is also demonstrated by the gradual decrease in the carbon, nitrogen, and sulfur contents (Table 39). The molding material properties remain essentially unchanged (Table 38).

[0354] Despite the decreasing carbon content, no casting defects were observed, and the surface roughness of the castings did not change significantly as a result of the reduction in carbon content (Table 40). Table 40: Surface roughnesses of castings produced during test series A

[0355] 3.2 Test series with the addition of organically bound core sand (test series B) When manufacturing the mold (see step (2)), ColdBox cores (see point 0.2 above) are inserted, which completely disintegrate in the middle and can no longer be separated from the molding material.

[0356] In this test series with 30 cycles (B1-B30, see Table 41), starting from the above-described prepared starting molding material from a brake disc foundry, a second prepared molding material (see Fig. 4) produced by preparing cores that had been produced with cold-box binder was added; i.e., in each subsequent cycle, the prepared molding material from the previous cycle (first prepared molding material) was refreshed with a second prepared molding material produced by preparing cores that had been produced with cold-box binder. Table 41: Composition and compactability of the molding material mixture in the individual cycles

[0357] (1) “First recycled moulding material” refers here to the quantity of moulding material from the previous cycle that was reused after recycling

[0358] (2) Addition of water

[0359] (3) Measured water content of the mixture Table 42: Characteristic values ​​of samples taken in the respective cycles to determine the molding material properties

[0360]

[0361] The molding material analysis (Table 43) shows that the loss on ignition of the molding material decreases with increasing cycle number. At the same time, the carbon (C), sulfur, and nitrogen (N) content decreases, with the C and N content approaching limit values ​​determined by the addition of cold box-bonded core sand. The molding material properties remain essentially unchanged (Table 42).

[0362] In this series of tests, the surface roughness of the castings was also determined (Table 44). It was observed that good surfaces were obtained despite the decreasing carbon content in the mold material. No casting defects were observed.

[0363] Table 44: Surface roughness of castings produced during test series B 3.3 Test series with addition of inorganically bound core sand

[0364] (Test series C)

[0365] When producing the mold (see step (2)), inorganically bound cores (binder Cordis 9477 / Anorgit 9476, see point 0.2 above) are used, which only disintegrate in the surface layer but can be easily crushed by hand.

[0366] In this test series with 30 cycles (C1-C30, see Table 45), a second processed molding material (see Fig. 4) produced by processing cores that had been produced with water glass binder (Anorgit / Cordis system) was added to the above-described processed starting molding material from a brake disc foundry (point 0.2); ie in each subsequent cycle, the processed molding material from the previous cycle (first processed molding material) is refreshed with a second processed molding material produced by processing cores that had been produced with water glass binder (Anorgit / Cordis system).

[0367] Table 45: Composition and compactability of the molding material mixture in the individual cycles

[0368]

[0369] (1) “First recycled moulding material” refers here to the quantity of moulding material from the previous cycle that was reused after recycling

[0370] (2) Addition of water

[0371] (3) Measured water content of the mixture Table 46: Characteristic values ​​of samples taken in the respective cycles to determine the molding material properties

[0372] The tests clearly demonstrate the gradual decrease in loss on ignition and the carbon, nitrogen, and sulfur contents with increasing molding material exchange (Table 47). The molding material properties remain essentially unchanged (Table 46).

[0373] Despite decreasing carbon content, no casting defects were observed and the surface roughness of the castings did not change due to the reduction in carbon content (Table 48).

[0374] Table 48: Surface roughness of castings produced during the test series

[0375] 3.4 Landfill class of the processed molding material

[0376] From all three test series, the processed molding material was examined after the 30th cycle (A-30, B-30, or C-30), and the obtained values ​​were compared with those of the original molding material (Table 49; the abbreviation NG indicates that the measured values ​​are below the detection limit). The following was determined:

[0377] According to the German Ordinance on Landfills and Long-Term Storage (Landfill Ordinance) of July 4, 2020, the processed molding material (source sand) is classified as landfill class II due to its loss on ignition, TOC (Total Organic Carbon) value, and phenol index. The processed molding material from test series B has a TOC value that is only slightly too high for classification in landfill class I and is therefore classified as landfill class II. However, a further reduction in the TOC value is possible through continued replacement or the use of a different cold box binder. The processed molding materials from test series A and C fall into landfill class I.

[0378] Table 49 (The abbreviation NG indicates that the measured values ​​are below the detection limit)

[0379] 1 . Determined according to DIN EN 14346: 2007-03

[0380] 2. Determined according to DIN EN 15169: 2007-05

[0381] 3. Determined according to DIN EN 15936: 2012-11 (AN,L8: Ver.A; FG,F5:Ver.B)

[0382] 4. Determined according to the communication of the State Working Group on Waste Communication 35 short: KW / 04: 2019-09

[0383] 5. Determined according to DIN EN ISO 10523 (C5): 2012-04

[0384] 6. Determined according to DIN EN 15216: 2008-01

[0385] 7. Determined according to DIN EN ISO 10304-1 (D20): 2009-07

[0386] 8. Determined according to DIN EN ISO 14403-2: 2012-10

[0387] 9. Determined according to DIN EN ISO 17294-2 (E29): 2017-01

[0388] 10. Determined according to DIN EN ISO 12846 (E12): 2012-08

[0389] 11 . Determined according to DIN EN 1484: 2019-04

[0390] 12. Determined according to DIN EN ISO 14402 (H37): 1999-12

[0391] 3.5 BTX emission potential of the processed molding material

[0392] The starting molding material from the brake disc foundry's conditioned molding material cycle and the molding materials from cycles A-30, B-30, and C-30 were analyzed for their BTX emission potential. For this purpose, the samples were dried at 105°C and ground in a planetary ball mill (Retsch Planetary Ball Mill PM100CM) for 2 minutes at 300 rpm under cold conditions (vessel: 150 ml stainless steel bowl with stainless steel balls). The sample was cooled to -20°C for at least 12 hours, i.e., the grinding bowl of the planetary ball mill was stored at -20°C for at least 12 hours before use to prevent excessive heating of the sample during the grinding process. Subsequently, 10 mg of sample was weighed into a pyrolysis tube. A duplicate determination was performed for each sample. The measurements were performed using the following equipment: • GERSTEL MPS

[0393] • GERSTEL TDU 2 with pyrolysis module

[0394] • Agilent 8890B gas chromatograph with Agilent 5977 mass spectrometer

[0395] • Capillary column RESTEK 13868 RXI-624SÜ MS, -60 °C-300 °C (320 °C): 30 mx 250 pm x 1 .4 0.25 mm • Stainless steel grinding bowl 150 mL and stainless steel grinding balls

[0396] • Hamilton electronic holder (VWR Art. No. HAMIDS86200)

[0397] • Hamilton 1 pL syringe (VWR Art. No. 549-1224)

[0398] • Carbotrap B packaged glass inlet liners (450 °C upper temperature limit) (Gerstel Art. No. 013248-005-00) • Quartz pyrolysis tubes (Gerstel Art. No. 018437-020-00)

[0399] • Adsorbent Matrix Carbopack™ B, 60-80 mesh (VWR Art. No. SUPL20273)

[0400] • Glass wool, silanized (VWR Art. No. SERA22367.01)

[0401] The following conditions are observed:

[0402] Gas Chromatography (GC) Parameters KAS parameters

[0403] (KAS = cold feed system - , ie the sample is pyrolyzed, the pyrolysis gases are condensed and then evaporated for the GC measurement)

[0404] Calibration method: MSD parameters (MSD = Mass Spectrometric Detector)

[0405] TDU parameters (TDU = Thermal Desorption Unit) Pyrolysis parameters

[0406] Calibration was performed using standards based on benzene, toluene; m- and p-xylene; styrene; o-xylene, ethylbenzene, and cumene.

[0407] Sample method: MSD parameters

[0408] TDU parameters Pyrolysis parameters

[0409] Key figures of the method

[0410] The evaluation was carried out using the MassHunter software.

[0411] The results presented in Table 50 clearly demonstrate that pollutant emissions can be significantly reduced by using an additive according to the invention. The emission potential is significantly reduced, particularly in conjunction with inorganic cores or when fresh mold base material (new sand) is added to the mold material cycle. A significant effect is also observed when cold box core sand is added. The emission potential is reduced by over 45% in the model case.

[0412] Table 50: Pyrolysis (GC-MS) of the molding materials after 30 cycles compared to the initial molding material (all data as mg emission / kg sample material) In Table 50, information “<” means that the content of the corresponding BTEX compound is below its detection limit.

[0413] The following applies to the value ranges in the line “BTEX at 900 °C”:

[0414] The lower limit corresponds to the sum of the levels of BTEX compounds that are above the respective detection limit, allowing a value to be determined (in the case of the starting molding material, these are benzene, toluene, ethylbenzene, and m- and p-xylene). The upper limit corresponds to the sum of the lower limit and the detection limits of each BTEX compound whose level is below the respective detection limit (in the case of the starting molding material, these are o-xylene, styrene, and cumene).

Claims

Moulding material for producing a clay-bound mould, the moulding material comprising: a moulding base material, a smectite-containing clay in a concentration of 4.5 to 16% by weight based on the mass of the moulding material, one or more dehydratable inorganic compounds which release water at a temperature of 150°C or more, the total concentration of said dehydratable inorganic compounds being 5 to 60% by weight based on the mass of the smectite-containing clay, Water in a concentration of 1.5 to 10 wt%, based on the mass of the molding material, Carbon in a concentration of 1.5% by weight or less based on the mass of the molding material. Molding material according to claim 1, wherein the mold base material is at least partially present as a component of processed molding material, preferably of processed molding material from at least one already cast mold bound with smectite-containing clay. Molding material according to one of claims 1 or 2, further comprising one or more reaction products formed by elimination of water from the said dehydratable inorganic compound(s), reaction products of the smectite-containing clay that cannot be reactivated by adding water. Molding material according to one of claims 1 to 3, wherein the smectite-containing clay is a bentonite, preferably selected from the group consisting of sodium bentonite and calcium bentonite and mixtures thereof. Molding material according to one of claims 1 to 4, further comprising one or more clays from the group consisting of kaolinite and illite.

6. Molding material according to one of the preceding claims, wherein one, several or all dehydratable inorganic compounds are selected from the group consisting of aluminum hydroxide and magnesium hydroxide.

7. Molding material according to claim 6, wherein the aluminum hydroxide is Al(OH)3 and / or the magnesium hydroxide is brucite.

8. Moulding material according to one of claims 6 and 7, wherein less than 50 wt%, preferably less than 25 wt% and particularly preferably less than 10 wt% of the Al2O3 contained in the moulding material is in the form of corundum.

9. Moulding material according to one of the preceding claims, wherein the moulding material has one or more of the following parameters: a compressibility in the range of 25% to 55%, determined according to VDG leaflet P37 (April 1997) a green compressive strength in the range of 8 N / cm 2 up to 35 N / cm 2 , determined according to VDG data sheet P38 (May 1997) a wet tensile strength of 0.10 N / cm 2 up to 0.50 N / cm2 , determined according to VDG data sheet P38 (May 1997) a gas permeability of 70 to 200, determined according to BDG guideline P41 (October 2013) an active clay content of 4.5 to 16%, determined by the methylene blue method according to VDG data sheet P035 (October 1999) a flowability of 20% to 90%, determined according to Morek Multiserw, operational documentation pile driving device type LUA-2e with electric drive, page 7.

10. Molding material according to one of claims 1 to 9, further comprising processed molding material from at least one cast or uncast core.

11. Molding material according to claim 10, wherein the dehydratable inorganic compounds are selected from the group consisting of aluminum hydroxide and Magnesium hydroxide, wherein the proportion of aluminum hydroxide is at least 80%, preferably at least 90%, more preferably at least 95% and particularly preferably at least 99%, based on the total mass of aluminum hydroxide and magnesium hydroxide, wherein the aluminum hydroxide is preferably Al(OH)3.

12. Molding material according to claim 10 or 11, wherein the prepared molding material from at least one core contains an inorganic binder and / or its reaction products formed during casting.

13. Molding material according to claim 12, wherein the molding material has one or more of the following parameters a concentration of less than 1.5%, preferably less than 0.8% carbon, based on the mass of the molding material, determined by elemental analysis a concentration of less than 0.1%, preferably less than 0.05% nitrogen, based on the mass of the molding material, determined by elemental analysis a concentration of less than 0.05%, preferably less than 0.03% sulfur, based on the mass of the molding material, determined by elemental analysis a loss on ignition of at most 5%, preferably at most 3.5%, determined according to VDG Data Sheet P33 (April 1997). 14 Molding material according to claim 10, wherein the prepared molding material from at least one core contains an organic binder and / or its reaction products formed during casting.

15. Molding material according to claim 14, wherein the molding material has one or more of the following parameters: a concentration of less than 0.2%, preferably less than 0.1% nitrogen, based on the mass of the molding material, determined by elemental analysis a concentration of less than 0.05%, preferably less than 0.03% sulphur, based on the mass of the moulding material, determined by elemental analysis, a loss on ignition of not more than 5%, preferably not more than 4%, determined according to VDG leaflet P33 (April 1997) 16. Molding material according to claim 14 or 15, wherein at least 70% by weight, preferably at least 80% by weight, more preferably at least 90% by weight and particularly preferably at least 95% by weight of the carbon contained in the molding material originates from processed molding material from at least one core which contains an organic binder and / or its reaction products formed during casting.

17. Use of a molding material according to one of claims 1 to 16 for producing a mold bonded with smectite-containing clay.

18. Use of a molding material according to one of claims 1 to 16 in a molding material cycle.

19. Use of the additive as defined in claim 1 for producing a molding material according to any one of claims 1 to 16.

20. A method for guiding a molding material in a molding material cycle comprising two or more cycles, comprising the following steps: in an earlier cycle of said two or more cycles of the molding material cycle, casting in a mold comprising smectite-containing clay-bound molding material, resulting in a cast molding material, Processing the cast molding material to result in a first processed molding material, in a later cycle of said two or more cycles of the molding material cycle. Producing a molding material according to one of claims 1 to 16 comprising (i) first processed molding material, and (ii) aggregates comprising one or more raw materials from the group consisting of Mold base material, a second processed mold material produced by processing molds and / or cores cast outside the mold material cycle, a third processed mold material produced by processing mold material from uncast molds and / or cores and / or parts thereof, an additive containing at least one dehydratable inorganic compound which releases water at a temperature of 150 °C or more, and optionally smectite-containing clay, preferably bentonite.

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