WO2024121197A1 - Method for guiding a moulding material in a moulding material cycle comprising two or more cycles - Google Patents

Abstract

The invention relates to a method for guiding a moulding material in a moulding material cycle comprising two or more cycles.

Description

Method for guiding a molding material in a molding material circuit comprising two or more cycles

The present invention relates to a method for guiding a molding material in a molding material circuit comprising two or more cycles.

Clays used to bind molding materials typically contain smectite. Examples of such smectite-containing clays are bentonites, particularly sodium and calcium bentonites, which contain sodium and calcium respectively, as well as the elements magnesium, aluminum and silicon. Other smectite-containing clays are hectorite, saponite, nontronite, beidellite or sauconite. Clays such as kaolinite or illite can be used as clay-containing binding agents in a mixture with smectite-containing clays.

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

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-containing clays” and “bentonite” are used both for corresponding clays obtained from natural deposits and for those produced by purification of naturally occurring clays.

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

Any sand that can form a foundry mold and can hold this shape at high temperatures and in contact with hot metal can be used as the mold base material. Typical sands are silica sand, olivine sand, chrome ore sand, zircon sand, as well as 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 particularly preferably over 70% sand.

In industrial practice, clay-bonded casting molds are usually 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". The compaction of the molding material leads to solidification and thus ensures sufficient dimensional stability.

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

Molding material cycle in the sense of the present 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 molds are again produced that are 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 clay-bound mold that has already been cast.

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

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):

(Step 1) Production of the moulding material, i.e. production of a moulding material comprising reprocessed moulding material from a previous cycle and additives (see below)

(Step 2) Making the mold, i.e. making a mold bound with smectic clay from the molding material produced in step (1),

(Step 3) Casting, i.e. producing a casting by pouring the mold made in step (2)

(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

(Step 5) Reprocessing the cast molding material, i.e. reprocessing the cast molding material from step (4) so that a first processed molding material is obtained for producing a new molding material in step (1) of a later cycle.

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

In each cycle of the molding material cycle described above, a casting is produced in step (3) by pouring the mold produced in step (2). The molding material is significantly changed by thermal and chemical stress during pouring (step (3) of the cycle). In order to enable the molding material to be recycled, the poured molding material must be processed.

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

The processing of the cast molding material in step (5) results in a processed molding material that remains in the molding material cycle. A part of the molding base material used (usually quartz sand) remains in the molding material cycle as a component of the processed cast molding material.

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.).

The thermal, mechanical and possibly 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 oolite grains of the mold base material.

To ensure that such wear products do not accumulate in the molding material cycle and/or that the molding material properties are not negatively affected or that the required active proportions of the binding agent (smectite-containing clay) and the additives do not drop too much, additives are added in a subsequent cycle in step (1) during the production of the molding material, i.e. the processed molding material is refreshed using the additives. In order to keep the mass of the molding material in the cycle constant, a corresponding amount of molding material is removed from the molding material cycle. This can take place before refreshing using the additives (i.e. in step (5)), or after refreshing using the additives.

The additives usually include smectite-containing clay, water, additives (see below) and one or more raw materials from the group consisting of fresh moulding material (new sand), second processed moulding material produced by processing uncast moulds and/or cores and/or parts thereof; third processed moulding material produced by processing moulds and/or cores and/or parts thereof that were produced and cast outside the moulding material cycle under consideration.

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

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

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 components of the molding material, essentially constant, optimal molding material properties can be achieved in the molding material cycle (molding material conditioning). The molding material is conditioned, i.e. optimally adjusted, in each cycle by determining the required addition rates of smectite-containing clay (addition 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 determining machine parameters such as mixing time or cooling intensity.

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.

Lustrous carbon formers (also known as lustrous carbon carriers, see https://www.giesserei-praxis.de/giesserei-lexikon/glossar/glanzkohlenstoff) are molding material additives with the ability to form hydrocarbon-containing gases that are coked in the reducing atmosphere of the mold cavity during casting. This produces lustrous carbon. Lustrous carbon formers commonly used include hard coal dust, pitch, bitumen, resins, oils, plastics and mixtures thereof. Lustrous carbon formers are added in particular to clay-bound molding materials for iron casting. The lustrous carbon prevents wetting by the liquid casting material at the metal/mold interface. In addition, lustrous carbon formers in the molding material can buffer quartz expansion and prevent sand expansion defects. However, increasing proportions of hard 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.

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

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, in particular aromatic hydrocarbons such as benzene, toluene and xylenes ("BTX emissions"), but also polycyclic aromatics. In addition, volatile sulphur-containing compounds are usually also emitted, since lustrous carbon formers often contain sulphur and/or sulphur-containing impurities. Another problem is the considerable risk of dust explosions and spontaneous combustion when handling lustrous carbon formers. Therefore, in industrial foundries, lustrous carbon formers are typically used in the form of a mixture pre-made by the supplier with the smectite-containing clay, in particular bentonite.

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

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. A circulation of the molding material is not disclosed. This document therefore does not provide any information as to whether such molding materials are suitable for use in a molding material circulation. WO 03/066253 A1 describes a method for producing a molding material for foundry purposes, in particular one that is recycled, 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 binding agent, e.g. bentonite, and water. In particular, framework or tectosilicates, such as zeolites, pumice or pumice stones, allophane, imogolite, diatomaceous earth, polygarskites, sepiolites, diatomaceous earth, or clays (treated with acid and/or heat) are used as non-swellable porous materials.

CN 108356214 discloses moulding material mixtures comprising sand, water, bentonite and an additive with the following composition

SiO2 _50-85 wt%

Al2O3 9-45 wt%

MgO 0.2-3 wt%

Fe ₂ O3 1 -8 wt%

CaO 1 -7 wt%

Fe3Ü4 0.4-8 wt%

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. Example molding materials were used for two to four months.

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, CO ₂ , and volatile organic compounds, in particular aromatic hydrocarbons such as benzene, toluene and xylenes ("BTX emissions"), but also polycyclic aromatics.

This object is achieved by a method for guiding a molding material in a molding material cycle comprising two or more cycles, with the following steps: in an earlier cycle of said two or more cycles of the molding material cycle, pouring in a mold comprising molding material bound with smectite-containing clay, resulting in a poured molding material,

Preparing the cast molding material so that a first prepared molding material results, in a later cycle of said two or more cycles of the molding material cycle, producing a molding material 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 mold material from uncast molds and/or cores and/or parts thereof, a third processed mold material produced by processing mold material from molds and/or cores and/or parts thereof cast outside the mold material cycle, - an additive which contains at least one dehydratable inorganic compound which splits off water at a temperature of 150 °C or more, and optionally smectite-containing clay, preferably bentonite, wherein at least one of the processed mold materials comprises material from cores which were produced with an organic binder and/or parts thereof, wherein the mold material produced in the later cycle contains carbon, wherein at least 70% by weight, preferably at least 80% by weight, and particularly preferably at least 90% by weight, very particularly preferably at least 95% of the carbon comes from the organic binder of cast and uncast cores and the reaction products of the binder.

Preferably, the additives also contain water.

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. It is not absolutely necessary that the additive defined above be added in every cycle of the molding material cycle. A molding material cycle according to the invention can comprise individual cycles in which this additive is not added.

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

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 are 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 are in particular carbonates, which can be contained in the molding material.

By specifying that at least 70% by weight, preferably at least 80% by weight, and particularly preferably at least 90% by weight, preferably at least 95% by weight, and particularly preferably at least 99% by weight of the carbon contained in the molding material produced in the later cycle comes from the organic binder, the proportion of other carbon carriers, in particular lustrous carbon formers, in the molding material is limited.

In molding materials with smectite-containing clay as a binder, the carbon content can be reduced in particular by reducing or avoiding the use of lustrous carbon formers.

By reducing or even avoiding the use of lustrous carbon formers, fossil resources are conserved. Thus, a further object that is achieved by the present invention is to provide a resource-saving molding material cycle.

By reducing or even avoiding 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. closed. 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.

By reducing or even avoiding 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 disposal of non-reusable molding material components. Thus, a further object that is achieved by the present invention is to facilitate the further use or disposal of cast molding material.

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.

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

The reduction in the proportion of lustrous carbon should not impair the properties of the moulding material, the moulds made from it and the castings produced therefrom in an unacceptable manner.

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

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. 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 oxidation state +II or +III are preferred, hydroxides of metals in the oxidation state +II or +III are particularly preferred. Magnesium hydroxide (in particular in the form of brucite) and aluminum hydroxide are particularly preferred, aluminum trihydroxide Al(OH)3 is most preferred. The aluminum trioxide can be present in various modifications, in particular as gibbsite, bayerite or nordstrandite, as well as in minerals in combination with other hydroxides or oxides.

The additive preferably contains one or both compounds from the group consisting of aluminum hydroxide and magnesium hydroxide. The proportion of aluminum hydroxide is preferably 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.

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

In the method according to the invention, 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 cast part. Casting the mold results in a cast molding material. The cast molding material is processed in the manner described above, so that a first processed molding material results. In order to keep the mass of the molding material circulated constant, part of the cast molding material is discharged during processing if necessary, so that discharged molding material results.

However, it is not absolutely necessary that processed molding material is discharged in each cycle of the molding material cycle. A molding material cycle according to the invention can comprise individual cycles in which no processed molding material is discharged.

In a later cycle of the molding material cycle, a molding material is produced comprising (i) first processed 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

Molding 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.

If part of the cast molding material has not already been discharged after processing, part of the molding material produced can now be discharged in order to keep the mass of the molding material in the circuit constant, so that discharged molding material results. However, this is not absolutely necessary. A molding material cycle according to the invention can include individual cycles in which no molding material is discharged.

At least one of the prepared molding materials used in the process according to the invention (first, second and third prepared molding material as defined above) comprises organic binder and/or reaction products thereof. The organic binder is preferably polyurethane, in particular polyurethane formed in the cold box process, or a phenolic resin in the form of a resol or a novolak. Cast cores or molds contain reaction products of the organic binder formed during casting.

The molding material produced in a later cycle of the molding material cycle comprises one, several or all of the raw materials mentioned above. The molding material used as a raw material preferably comprises fresh quartz sand (new sand), or silica sand, olivine sand, chrome ore sand, zircon sand, or ceramic sands that have been artificially produced, or mixtures of these sands.

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

The second reprocessed molding material as defined above is produced by reprocessing molding material from uncast molds and/or cores and/or parts thereof. The 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.

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 molding material cycle under consideration, i.e. molds and cores that were cast, for example, in another production line.

Preferably, the molding material produced in the later cycle has one or more of the following parameters: a concentration of less than 4%, preferably less than 3% carbon, 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 VDG data sheet P33 (April 1997)

The molding material produced in the later cycle particularly preferably has one or more of the following parameters: a concentration of less than 3%, preferably less than 2.5%, particularly preferably less than 2% 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) Preferably, all of the above-mentioned parameters of the molding material are in the above-mentioned preferred ranges, in particular in the above-mentioned particularly preferred ranges.

In one embodiment of the method according to the invention, casting takes place in the earlier cycle in a mold with at least one inserted core that was produced with an organic binder. This results in a cast molding material that comprises material from the cast mold and material from the cast core. The material from the cast core comprises reaction products of the organic binder formed during casting.

Cores that are used in clay-bonded molds are typically not clay-bonded. In the embodiment of the method according to the invention described here, these cores are produced with an organic binder. Preferably, the organic binder is polyurethane, in particular polyurethane formed in the cold box process, or the organic binder is a phenolic resin in the form of a resol or a novolak. The cast molding material resulting in 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.

In this embodiment of the method according to the invention, a second processed molding material can be used which contains material from uncast molds and/or cores and/or parts thereof, wherein the molds and/or cores are preferably produced with an organic binder, e.g. a cold box binder, or a phenolic resin in the form of a resol or a novolak, and/or a third processed molding material which contains material from cast molds and/or cores and/or parts thereof, wherein the molds and/or cores are preferably produced with an organic binder, e.g. a cold box binder, or a phenolic resin in the form of a resol or a novolak.

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. In this embodiment of the method according to the invention, the second prepared molding material contains material from uncast cores and/or molds and/or parts thereof, the molds and/or cores having been produced with an organic binder, and/or the third prepared molding material contains material from cast molds and/or cores and/ or parts thereof, wherein the molds and/or cores were produced with an organic binder. Preferably, the organic binder is polyurethane, in particular polyurethane formed in the cold box process, or the organic binder is a phenolic resin in the form of a resol or a novolak. Material from cast molds and cores comprises reaction products of the organic binder formed during casting.

In the process according to the invention, the circulated molding material is preferably used to produce molds for iron casting.

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

(Step 1) Manufacturing the molding material, i.e. manufacturing a molding material comprising

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

(ii) Aggregates as defined above

(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. producing a casting by pouring the mold made in step (2)

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

(Step 5) Processing of the cast molding material, i.e. processing the cast molding material from step (4) so that a first processed molding material is obtained for producing a new molding material in step (1) of a later cycle, and optionally discharging a part of the cast molding material so that discharged molding material results.

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 circulated constant, part of the molding material produced in step (1) of the next cycle can be discharged, resulting in discharged molding material. 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 preferably comprise the following steps (cf. Figure 4, the further features of which are not intended to be limiting):

(Step 1) Manufacturing the molding material, i.e. manufacturing a molding material comprising

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

(ii) Aggregates as defined above

(Step 1 a) Producing the core molding material, i.e. producing or providing a molding material for producing at least one core, wherein the molding material contains an organic binder, preferably a coldbox binder or a phenolic resin in the form of a resol or a novolak

(Step 2) Making the mold, i.e. making a mold bound with smectite-containing clay from the molding material produced in step (1)

(Step 2a) Producing the core, i.e. producing at least one core and inserting the at least one core into the mold produced in step (2)

(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

(Step 5) Preparation, i.e. 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 if necessary, discharging a part of the cast molding material so that discharged molding material results.

If part of the cast molding material has not already been removed during the preparation in step (5), in order to keep the mass of the molding material in the circuit constant, hold, a part of the molding material produced in step (1) of the next cycle is discharged, so that discharged molding material results.

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

When producing the molding material, in particular in step (1) of the molding material cycle, the prepared molding material and the additives are preferably mixed. The additives added in step (1) preferably also include water.

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

Preferably, the cast molding material is cooled before processing.

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

The thermal, mechanical and, if applicable, chemical stress results in the formation of wear products such as fine sand particles, inactive clay particles, decomposition products of the additives and/or the lustrous carbon formers or reaction products of core binders, as well as oolite grains of the mold base material.

In order to prevent such wear products from accumulating in the molding material cycle and/or to prevent the molding material properties from being negatively affected and/or to prevent the required active proportions of the binding agent (smectite-containing clay) and the additive to be used according to the invention from falling too low, additives are added to the molding material in a subsequent cycle, in particular in step (1), during the manufacture of the molding material, i.e. the processed molding material is refreshed by the additives. In order to keep the mass of the molding material in the cycle constant, a corresponding amount of molding material is removed from the molding material cycle. This can be done before refreshing with the additives (in particular in step (5)), or after refreshing. see through the additives, ie after the moulding material has been produced in the later cycle. In the latter case, the amount of additives added is kept as low as possible.

In some cases, step (5) therefore comprises the necessary discharge of cast molding material in the same amount as is refreshed in step (1) of the next cycle by additives comprising the additive to be used according to the invention; in this way it is possible to achieve a uniform level of properties.

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.

If part of the cast molding material has not already been discharged in step (5), in order to keep the mass of the molding material circulated 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.

Preferably, the molding material cycle to which the method according to the invention relates comprises at least 10 cycles, preferably at least 15 cycles, particularly preferably at least 30 cycles.

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 pm to 200 pm, determined by means of laser granulometry.

Preferably, the proportion of dehydratable inorganic compounds which release water at a temperature of 150°C or more is 1% to 100%, based on the total mass of the additive as defined above. Particularly preferably, the proportion of dehydratable inorganic compounds which 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. Very particularly preferably, the proportion of dehydratable inorganic compounds which 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. The proportion of dehydratable inorganic compounds which release water at a temperature of 150°C or more is particularly preferably 50% to 100%, based on the total mass of the additive as defined above.

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

Lustrous carbon formers

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 4% by weight, preferably not higher than 2.5% by weight, more preferably not higher than 2.0% by weight, particularly preferably not higher than 1.5% by weight.

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 at least 70% by weight, preferably at least 80% by weight, and particularly preferably at least 95% by weight of the carbon contained in the molding material produced in the subsequent cycle comes from the organic binder.

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%. Particularly preferred are 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. No special effort is therefore required for drying the aluminum hydroxide.

In the additive, aluminium hydroxide may be present in a mixture with iron oxide and/or iron hydroxide, whereby the proportion of aluminium hydroxide is greater than 40%, based on the total mass of aluminium hydroxide, iron oxide and/or iron hydroxide.

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). 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.

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, very particularly preferably 0.05% by weight, based on the total mass of the additive.

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

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

Alternatively, the additive and smectite-containing clay can be provided as a mixture, and the other additives separately. This procedure corresponds to the current standard of providing lustrous carbon images in a pre-made mixture with smectite-containing clays. This means that existing storage and dosing equipment in the foundry can continue to be used.

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

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 raw materials from the group consisting of

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

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. 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 1.0 wt.%, based on the total mass of the molding material to be produced.

The total mass of the dehydratable inorganic compounds introduced as an additive, 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.

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

The mold base material is preferably selected from the group consisting of quartz sand, olivine sand, chrome ore sand, zircon sand, and ceramic sands that have been artificially produced, and mixtures of these sands. Typically, a clay-bound mold contains at least 40% sand, preferably over 50% sand, particularly preferably over 60% sand, and most particularly preferably over 70% sand.

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. At temperatures above 1000 °C, aluminum hydroxide is irreversibly converted into corundum (a-aluminum hydroxide), which cannot be converted back into aluminum hydroxide in a later cycle by adding water and is therefore no longer able to act as an additive to be used according to the invention as defined above.

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.

Preferably, the molding material produced in the later cycle of the process according to the invention has the following parameters: a compressibility in the range of 25% to 55%, determined according to VDG data sheet P37 (April 1997), and/or a green compressive strength in the range of 8 N/cm ² to 35 N/cm ² , determined according to VDG data sheet P38 (May 1997) and/or a wet tensile strength of 0.10 N/cm ² to 0.50 N/cm ² , determined according to VDG data sheet P38 (May 1997) and/or a gas permeability of 70 to 200, determined according to BDG guideline P41 (October 2013) and/or an active clay content of 4.5 to 16%, determined by the methylene blue method according to VDG data sheet P035 (October 1999) and/or a flowability of 20% to 90%, determined according to Morek Multiserw, operational documentation for piling rig type LUA-2e with electric drive, page 7.

The molding material produced in the later cycle of the process 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 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 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 according to the methylene blue method according to VDG data sheet P035 (October 1999) and/or a flowability from 50% to 90%, determined according to Morek Multiserw, Operational documentation of pile driver type LUA-2e with electric drive, page 7.

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.

A further aspect of the present disclosure relates to the use of the additive defined above in a process according to the invention as defined above. The above statements apply with regard to additives to be used with preference and preferred process designs. The invention is described in more detail below with reference to the attached schematic figures.

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

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

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

Fig. 4 a molding material cycle (casting in mold with core) according to the inventive method

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.

In step (1) a molding material is produced comprising

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

(ii) Aggregates.

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

1 and Fig. 2, respectively, were produced and cast,

Smectite-containing clay, preferably bentonite

Water.

The second processed molding material contains material from uncast molds, cores and/or parts thereof, wherein the molds and/or cores were produced with an organic binder, and/or the third processed molding material contains material from cast molds, cores and/or parts thereof, wherein the molds and/or cores were produced with an organic binder. The organic binder is preferably polyurethane, in particular polyurethane formed in the cold box process, or a phenolic resin in the form of a resol or a novolak. The material from the cast molds and core comprises reaction products of the organic binder formed during casting.

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

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. The additive preferably contains aluminum trihydroxide or consists thereof.

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

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

In step (4), the casting produced in step (3) is separated from the mold, resulting in a cast molding material which comprises material from a cast mold but no material from cast cores. 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 so that a first processed molding material is obtained for producing a new molding material in step (1) a later cycle, in particular the next cycle. Preferably, the cast molding material is cooled before processing in step (5). During processing, part of the cast molding material may be discharged, resulting in a discharged molding material.

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 circulated constant, part of the molding material produced in step (1) of the next cycle is discharged, resulting in discharged molding material.

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.

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), (1a), (2), (2a), (3), (4) and (5) as defined above.

In step (1) a molding material is produced comprising

(i) a first reconditioned moulding material produced by reprocessing the cast moulding material resulting from a previous cycle of the moulding material cycle, which comprises material from cast cores produced with an organic binder and

(ii) Aggregates.

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. 3 and Fig. 4 respectively, were produced and cast,

Smectite-containing clay, preferably bentonite

Water.

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

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. The additive preferably contains aluminum trihydroxide or consists thereof.

In step (1 a), a molding material for producing at least one core (core molding material) is produced or provided. This molding material comprises my molding base material, an organic binder and optionally additives. Suitable additives for molding materials for producing cores are known from the prior art. The binder is a conventional organic binder, e.g. a coldbox binder, or the organic binder is a phenolic resin in the form of a resol or a novolak.

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

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

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

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. The material from the cast core comprises reaction products of the binder formed during casting.

Preferably, the mould with the casting is cooled before separation in step (4). In step (5), the cast molding material from step (4) is processed so that a first processed molding material is obtained for producing a new molding material in step (1) of a later cycle, in particular the next cycle. Preferably, the cast molding material is cooled before processing in step (5). During processing, part of the cast molding material may be discharged so that a discharged molding material results.

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 circulated constant, part of the molding material produced in step (1) of the next cycle is discharged, resulting in discharged molding material.

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.

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

0. Test methods and moulding materials

0.1 Test methods

The following test methods (measurement methods) were used (Table 1)

Table 1: Measurement methods used

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

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 it may contain.

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

As part of the experimental investigations, processed molding materials from core sands were used (second processed molding material as defined above). For this purpose, cores were produced with an organic binder or an inorganic binder and then grated using a circular vibrating screen from Webac.

The starting material for a molding material made with an organic binder is cores produced using the cold box process, which are produced using the binder Biocure 8568P1 / Silcure 8431 P2 distributed by Hüttenes-Albertus Chemische Werke GmbH on a core shooting machine LL20 from Laempe. For this purpose, a sand of type H32 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 Shooting pressure of 450 kPa (4.5 bar) and a shooting time of 1.5 seconds and then 10 g of dimethylpropylamine (N,N-dimethylpropylamine, catalyst GH6 from Hütten es- Albertus Chemische Werke GmbH) are flowed through for 45 s at a gassing pressure of 200 kPa (2 bar) to harden it. The starting material for a molding material produced with an inorganic binder is cores which are produced using the binder system Cordis 9477 / Anorgit 9476 distributed by Hüttenes-Albertus Chemische Werke GmbH on an LL20 core shooting machine from Laempe. For this purpose, 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 per 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 harden the cores, hot air at 120 °C was blown through them for 1 minute at a gassing pressure of 200 kPa (2 bar).

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

Table 3: Parameters of the processed moulding materials from core sands

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 on 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 shaped into the core in a loose core box. The core was then gassed with 100°C hot CO2 for 60s in a laboratory core shooting machine from Morek at a gassing pressure of 150 kPa (1.5 bar) and thus hardened.

1 . Screening tests to identify suitable additives

6 kg of quartz sand (H32, Quarzwerke) are mixed in a mixer (pan mill mixer LM-2e, Morek MULTISERW) with 120 ml of water 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 mixture thus obtained is sieved by hand through a sieve with a mesh size of 3 mm, and then the compressibility (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 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 min, then sieving and VDC measurement are repeated. The addition of water is repeated until the VDC is above 44.0%.

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

1) a commercially available premix of 25% lustrous carbon former (“sea coal”) and 75% sodium bentonite (NEMIR 2575) from HA Italia S.p.A.

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

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, casting is carried out using the sleeve model device described in (https://www.researchdisclosure.com/database/RD705032), i.e. molds manufactured according to the sleeve model device as described in (https://www.researchdisclosure.com/database/RD705032) are cast, the castings are then blasted and the surface roughness is measured in accordance with DIN EN ISO 4287 (R_ISO). 2 castings are examined at a time, and the surfaces are measured three times with a Mitutoyo SJ-500P surface measuring device at small, medium and large distances between the star-shaped ribs, each over a measuring distance of 8 mm. No uniform trend can be determined with regard to the distance between the ribs and the surface roughness, so the average value of all measurements taken is used to simplify the evaluation. This shows that the surface roughness of all the castings obtained is in a range that allows commercial use.

1 .1 Various types of aluminium hydroxide and magnesium hydroxide as additives

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

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 the technical data sheet of Ziegler from 10/2020).

Table 4: Parameters of the brucite types used as additives

Table 5 shows the molding 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 ² and water contents of <2.8% are considered particularly positive, while dry compressive strengths of >50 N/cm ² are rated as negative, as are water contents of >3.2%. Hydroxides, in particular aluminum hydroxide AI(OH)3 and magnesium hydroxide Mg(OH)2, enable the production of molds and show good molding material properties (see Table 5).

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

1 .2 Investigation of aluminium hydroxide AKOHh as an additive with addition of lustrous carbon formers

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

1 .3 Untersuchungen verschiedener Carbonate als Vergleichs-Additive SH 950 as additive with addition of lustrous carbon former Carbo luxon 100/P

1 .3 Investigations of various carbonates as comparative additives

While huntite (trade name UltraCarb D98, purchased from LKAB Minerals) does not achieve sufficiently good molding material values, dolomite and manganese carbonate (purchased from TROPAG GmbH) show quite acceptable molding material values (Table 7).

Bianco Zandobbio 0/50 micron from Ziegler and PE-DOL 90 from Possehl Erzkontor were used as dolomites. Overall, the molding material properties are somewhat worse than those when using the hydroxides described above. The values nevertheless allow the materials to be used as a replacement for classic lustrous carbon material formers. However, carbonates have the disadvantage that they contain carbon.

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

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.

Table 8: Mould material properties and flatness of the casting when using different carbonate-hydroxide mixtures

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

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

1 .4 Emissions from the bentonite and additives used

Table 10 shows emission measurements of the bentonite and additives used. The emission measurements were carried out 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 carried out using test gases.

The emissions of the additives to be used according to the invention are significantly lower than the emissions 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 the emissions of hydrocarbons, in particular benzene, toluene, 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 when using different additives (all figures in mg/kg, i.e. mg of the relevant emission / kg of material)

2. Production and testing of molding materials in the cycle

The aim of these tests is to cast and reprocess a certain amount of molding material several times. As is usual in industrial foundries, the molding material is circulated. Each time the molding material is processed, additives are added, which increase with each cycle. Components that are present in the initial molding material but are 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 is constant and amounts to around 8 kg. Two molds are produced and cast per cycle according to the sleeve model setup as described in (https://www.researchdisclosure.com/database/RD705032).

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

The cycles of the molding material cycle include the following steps:

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

Test series 2.1 , 2.2.1 , 2.2.2, 2.3.1 , 2.3.2 as described below

The first cycle uses 6 kg of H32 quartz sand from Quarzwerke. The molding base is then mixed with 480 g of sodium bentonite (Natroben 25F, HA ITALIA SpA, which is a Na-bentonite produced by activating a natural Ca-bentonite) and 300 g of the respective additive as well as 120 ml of water on 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 molding base is first mixed with 120 ml of water on a Morek Multiserw pan mill mixer for 1 minute and then mixed again for 7 minutes after the water has been added. Test series 2.4-2.6 as described below

In the first cycle, 3.7 kg of type H32 quartz sand from Quarzwerke is used. The molding base material is then mixed with 322 g of Volclay (GEKO™ V foundry bentonite from Clariant Deutschland GmbH, which is a naturally occurring sodium bentonite) and 207 g of the respective additive as well as 130 ml of water on 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 molding base material is first mixed with 130 ml of water on a Morek Multiserw pan mill mixer for 1 minute and then mixed again for 7 minutes after adding 322 g of Volclay and 207 g of the respective additive on a Morek Multiserw pan mill mixer.

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

Each time the molding material is produced (step (1)), additives are added that increase with each cycle. By discharging part 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 is reduced.

Making the mold (step (2) in all cycles)

For this purpose, the molding material is filled into the mold of the sleeve model device 3 minutes after mixing and compacted in 2 pressing processes (filling, pressing, refilling, pressing). The process is completed in a further 3 minutes. 2 molds are produced per test.

Drain (step (3) in all cycles)

The molds are poured one after the other after a 30-minute waiting period. The mold is poured with liquid metal of the alloy GJL 250 at 1450 °C using a pouring ladle. The poured mold is left overnight until it is separated. The casting cools down during this process and the molding material first heats up and then cools down overnight in the mold. Separation (step (4) in all cycles)

The casting and the cast molding material are separated.

Processing (step (5) in all cycles)

The molding material is filled into a storage container and the molding material lumps are crushed. Metal residues are removed.

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

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).

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 S.p.A., 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 for a further 7 minutes on a Morek Multiserw pan mill mixer.

The increase in the quantity of the moulding material due to additions in the mixer, i.e. the increase in the quantity of the moulding material resulting from the addition defined above, is regulated by removing the same quantity of ready-mixed moulding material in each cycle.

Each time the molding material is manufactured (step (1)), additives are added that increase with each cycle. By removing part of the cast molding material, the proportion of components that are present in the initial molding material but are no longer added in subsequent cycles is reduced. 2.1 Additive AI(OH)3 or MqfOHh when adding fresh molding material to the

Folqecycles (not according to the invention)

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 molding material of type H32 from Quarzwerke.

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.

SH950 nuance-00 from Alteo is used as the aluminium hydroxide AI(OH)3 additive. The results of the tests with AI(OH)3 are shown in Table 1 1.

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

When using fresh molding material as additive (see Figure 2, step (1)), both additives show good molding properties and a comparable surface quality, which can be seen from the measured roughness of the castings.

AI(OH)3 as an additive results in a higher active clay content and a significantly lower loss on ignition. For both AI(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.

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

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

2.2 AI(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 is carried out and the molding material and casting properties are measured as described in Chapter 2.1, but in the subsequent cycles, instead of fresh molding material, a second prepared molding material (see Fig. 2, step (1)) produced by preparing uncast cores is added.

(Quantity share of the produced molding material see Tables 13 and 16) which had been produced with cold-box binder (“ColdBox core sand”). 2.2.1 Aluminium hydroxide AKOHh when adding cold box core sand in the following cycles

When using aluminum hydroxide AI(OH)3, the molding material properties with 5% addition of ColdBox core sand are so stable that from cycle 15 onwards the addition is increased to 10% ColdBox core sand (Tables 13 and 14). The molding material properties remain stable.

Table 13: Composition and compactability of the moulding material mixture in the individual cycles

Table 14: Characteristic values of samples taken in the respective cycles

The data from the CNS analysis of the molding materials from the different cycles show the increase in the carbon and nitrogen content resulting from the addition of ColdBox core sand. The surface roughness of the castings is improved compared to the test series with the addition of new sand (see above 2.1) instead of ColdBox core sand, this is attributable to the addition of core sand (Table 15).

Table 15: 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 2.2.2 MqfOHh when adding ColdBox core sand in the subsequent cycles

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 kept stable. Therefore, the bentonite content of the molding material is increased in cycles 8 and 14 (Table 16). Despite this, there is no stabilization of the molding material properties (Table 17). In particular, the wet tensile strength decreases with increasing number of cycles and this trend can only be counteracted in the short term by adding more fresh bentonite.

Table 16: Composition and compactability of the moulding material mixture in the individual cycles

Table 17: Characteristic values of samples taken in the respective cycles

As expected, the carbon content and, to a limited extent, the nitrogen content of the molding material increases when ColdBox core sand is added (Table 18). The surface roughness of the castings is good and is not negatively affected. In contrast to aluminum hydroxide AI(OH)3 (see test series 2.2.1 above), magnesium hydroxide Mg(OH)2 does not enable a molding material cycle with stable molding material properties when organic core sand is added (i.e. ColdBox core sand, see above) (Table 17).

Table 18: 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 2.3 AI(OH)3 and MgfOHh when inorganically bound core sand is added to the

Subsequent cycles (not according to the invention)

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

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

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

Tabelle 20: Kennwerte von Proben, die in den jeweiligen Zyklen entnommen wurden

Table 19: Composition and compactability of the moulding material mixtures in the individual cycles

Table 20: Characteristic values of samples taken in the respective cycles

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 surface roughnesses obtained (Table 21) are very close to those of the tests with the addition of coldbox core sand (test series 2.2.1).

Table 21: 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

2.3.2 Magnesium hydroxide MqfOHh with addition of inorganically bound

Core sand in the Folqe cycles

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 kept stable. Therefore, the bentonite content of the molding material is increased in cycles 8 and 15 (Table 22). Despite this, there is no stabilization of the molding material properties. In particular, the wet tensile strength decreases with increasing number of cycles and this trend can only be counteracted in the short term by adding more fresh bentonite (Table 23).

Tabelle 23: Kennwerte von Proben, die in den jeweiligen Zyklen entnommen wurden

Die Analyse von ausgewählten Formstoffproben (Tabelle 24) zeigt für hohe Zyklenzahlen ein leichtes Ansteigen des Kohlenstoff-Gehalts, was vermutlich aus der Zudosierung des Bentonits herrührt; Ca-Bentonite werden bei der Aktivierung mit Carbonaten behandelt. Die Oberflächenrauheiten der Gussstücke sind stets akzeptabel, d.h. gut bis sehr gut. Tabelle 24: CNS-Analyse von ausgewählten Zyklen und Oberflächenrauheit der zugehörigen Gussteile

Similar to the addition of ColdBox core sand (test series 2.2.2), no molding material cycle with stable molding material properties is obtained here with Mg(OH)2 as an additive, the water requirement of the mixture 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 the correct state (target compactability). The active clay content and the wet tensile strength show a clear decrease with an increasing number of cycles. This can be compensated by adding bentonite, but overall there is no molding material cycle with stable molding material properties. Table 22: Composition and compactability of the moulding material mixture in the individual cycles

Table 23: Characteristic values of samples taken in the respective cycles

The analysis of selected mold material samples (Table 24) shows a slight increase in the carbon content for high numbers of cycles, which is probably due to the addition of bentonite; Ca-bentonites are treated with carbonates during activation. The surface roughness of the castings is always acceptable, ie good to very good. 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

2.4 Additive AI(OH)3 when adding fresh molding material in the subsequent cycles (not according to the invention) 11 cycles (0-10) are carried out using the sleeve model device described in (https://www.researchdisclosure.com/database/RD705032), whereby in the first test 100% fresh molding material of type H32 from Quarzwerke is used.

In all subsequent cycles 1 to 10, 3.7 kg of the used molding material from the previous casting are used and refreshed with 185 g of molding material (fresh molding material), as well as 26 g of bentonite and 23 g of the respective additive (Table 25). Additive aluminium hydroxide AI(OH)3 SH950 nuance-00 from Alteo is used. Stable moulding material properties were achieved (Table 26).

When using fresh mold base material as an 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).

Table 25: Composition and compactability of the moulding material mixture in the individual cycles

(1) The abbreviation NG indicates that the measured values are below the detection limit

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

11 cycles (0-10) are carried out using the sleeve model device described in (https://www.researchdisclosure.com/database/RD705032). The test is carried out and the molding material and casting properties are measured as described in Chapter 2.4, but in the subsequent cycles, instead of fresh molding material, a second prepared molding material (see Fig. 2, step (1)) is added, prepared by preparing uncast cores (for the proportion of the molding material produced, see Table 28), which had been produced with cold-box binder ("cold-box core sand"). Stable molding material properties were achieved (Table 29).

Table 28: Composition and compactability of the moulding material mixture in the individual cycles

Table 29: Characteristic values of samples taken in the respective cycles

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).

Table 30: 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

2.6 AI(OH)3 when adding inorganically bound core sand in subsequent cycles

(not according to the invention)

11 cycles (0-10) are carried out using the sleeve model device described in (https://www.research- disclosure.com/database/RD705032). The test is carried out and the properties of the molding material and casting are measured as described in Chapter 2.4, but in the subsequent cycles, instead of fresh molding material, a second processed molding material (see Fig. 2, step (1)) is added, produced by processing uncast cores (for the proportion of the molding material produced, see Table 31), which had been produced with an inorganic binder (water glass) ("lOB core sand"). This is therefore an inorganic molding material cycle with regard to all binders used. Stable molding material properties were achieved (Table 32).

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

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 surface roughnesses obtained (Table 33) are comparable to those of the tests with the addition of coldbox core sand (test series 2.5).

Table 33: 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 3. Moulding material cycle with successive reduction of the carbon content in the moulding material

The aim of these tests is to cast and reprocess a certain amount of processed molding material several times, in particular with a gradual reduction in the carbon content in the molding material. As is usual in industrial foundries, the molding material is circulated. Each time the molding material is processed, additives are added, which increase with each cycle. Components that are present in the initial molding material but are 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 is constant and amounts to around 1,200 kg. Four molds are produced and cast per cycle according to the rib pattern setup as described in (https://www.researchdisclosure.com/database/RD705032).

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

The cycles of the molding material cycle include the following steps:

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

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 above).

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

Each time a molding material is produced (step (1), see Figure 4), additives are added that increase with each cycle. By removing part 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 bunker and transported to the mixer together with the additives. The mixing process starts, water is automatically dosed and the finished molding material is emptied from the mixer into a transport container after the mixing process has ended. The transport container is transported to the molding system. The mixer program is selected between a mixing process without an intermediate stop (Table 35) and a mixing process with an intermediate stop (Table 34) depending on the situation (depending on the water content of the mixture) and the desired compaction is set to 40% +/- 5% by checking the water content. The desired compaction is set by checking the compactability. The compactability changes with the water content of the molding material. The water content was determined for each mixture. Since the necessary water addition to achieve the target compactability is not known, the intermediate stop in the mixing process makes it easier to determine the amount of water required and the following mixtures can be produced without an intermediate stop.

Tabelle 35: Mischablauf ohne Zwischenstopp

Table 34: Mixing sequence with intermediate stop

Table 35: Mixing process without intermediate stop

Making the mold (step (2) in all cycles)

To do this, a partial volume of the lower box of the mold is first filled with a layer of sieved molding material from the transport container; so much molding material is sieved that the contour of the rib model is no longer visible (this corresponds to 80 mm height in the lower box and 50 mm height in the upper box). The remaining volume of the lower box is then filled with unsieved molding material. The sieve has a clear mesh size of 2 mm.

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

Table 36: Compaction parameters

The lower box is pulled off by hand and transported to the loading station by crane. The upper box is filled, compacted, pulled off and transported in the same way. A previously manufactured core (step (1 a), see Fig. 4) is placed in the lower box (step (2a), see Fig. 4). The mold is placed, clamped and transported to the casting station.

Drain (step (3) in all cycles)

The mould 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.

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

The cast mold is left to stand for 4 hours before being separated. The casting cools down and the molding material heats up.

Separation (step (4) in all cycles)

The upper and lower boxes are opened. The casting and the poured molding material are separated. In the three molding material cycles that were examined, the core sand is handled differently:

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.

2. In test series B, in which ColdBox cores are used, the core completely disintegrates in the middle and can 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 bound cores (binder Cordis 9477 / Anorgit 9476, see point 0.2) were used, these only disintegrate in the surface layer, but can be easily crushed by hand. Therefore, the IOB core sand is not removed.

Processing (step (5) in all cycles)

The molding material is spread out on the floor and molding material lumps are crushed using a shovel. The meta-urea residues are removed. The molding material is left on the hall floor for at least 3 hours to cool. After cooling, the molding material is filled back into a big bag using shovels.

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

A new molding material is produced by refreshing the prepared molding material from the previous cycle (first prepared molding material) by adding bentonite, water, 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, for details see below). For the mixing process, see the information on step (1) of the first cycle above.

The increase in the quantity of the moulding material due to additions in the mixer, i.e. the increase in the quantity of the moulding material resulting from the addition defined above, is regulated by removing the same quantity of ready-mixed moulding material in each cycle.

Each time the molding material is manufactured (step (1)), additives are added that increase with each cycle. By removing part of the cast molding material, the proportion of components that are present in the initial molding material but are no longer added in subsequent cycles is reduced.

3.1 Test series with addition of fresh moulding material (new sand) in step (1) (test series A, not according to the invention)

When making 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 in step (4) as described above. 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

(1) “First reprocessed moulding material” refers to the amount of moulding material from the previous cycle that was reused after reprocessing

(2) Addition of water

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

Table 39: Analysis of samples from individual cycles

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

Despite decreasing carbon content, no casting defects are observed and the surface roughness of the castings does not change significantly by reducing the carbon content (Table 40). Table 40: Surface roughness of castings produced during test series A

3.2 Test series with addition of organically bound core sand (test series B) When producing the mold (see step (2) above), 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.

In this test series with 30 cycles (B1-B30, see Table 41), starting from the above-described prepared starting molding material from a brake disk foundry, a second prepared molding material (see Fig. 4) was added, produced by preparing cores that had been produced with cold-box binder; ie 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

(1) “First reprocessed moulding material” refers to the amount of moulding material from the previous cycle that was reused after reprocessing

(2) Addition of water

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

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

The surface roughness of the castings is also determined in this series of tests (Table 44). It is observed that good surfaces are obtained despite the decreasing proportion of carbon in the molding material. No casting defects can be observed.

3.3 Versuchsreihe mit Zuschlag von anorganisch gebundenem KernsandTable 44: Surface roughness of castings produced during test series B

3.3 Test series with addition of inorganically bound core sand

(Test series C, not according to the invention)

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

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 manufactured with water glass binder (Anorgit/Cordis system) was added to the above-described processed initial molding material from a brake disk foundry (point 0.2); i.e. 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 manufactured with water glass binder (Anorgit/Cordis system).

Table 45: Composition and compactability of the moulding material mixture in the individual cycles

(1) “First reprocessed moulding material” refers to the amount of moulding material from the previous cycle that was reused after reprocessing

(2) Addition of water

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

The tests clearly show the gradual decrease in the loss on ignition and the contents of carbon, nitrogen and sulphur with increasing exchange of the moulding material (Table 47). The moulding material properties remain essentially unchanged (Table 46).

Despite decreasing carbon content, no casting defects were observed and the surface roughness of the castings did not change by reducing the carbon content (Table 48).

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

3.4 Landfill class of the processed molding material

From all three test series, the processed molding material is examined after the 30th cycle (A-30, B-30 or C-30) and the values obtained are 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:

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

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

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

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

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

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

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

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

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

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

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

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

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

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

3.5 BTX emission potential of the processed molding material

The initial molding material from the conditioned molding material cycle of the brake disc foundry and the molding materials from cycles A-30, B-30 and C-30 were examined for their BTX emission potential. For this purpose, the samples are dried at 105°C and then 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 cup with stainless steel balls). It is cooled for at least 12 hours at -20°C, ie the grinding cup of the planetary ball mill was stored for at least 12 hours at -20°C before use in order to to avoid excessive heating of the sample during the grinding process. Then 10 mg of sample is weighed into a pyrolysis tube. Each sample is determined in duplicate. The measurements are carried out using the following equipment: • GERSTEL MPS

• GERSTEL TDU 2 with pyrolysis module

• Agilent 8890B gas chromatograph with Agilent 5977 mass spectrometer

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

• Hamilton electronic holder (VWR Art. No. HAMIDS86200)

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

• 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)

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

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

The following conditions are met:

KAS Parameter Gas Chromatography (GC) Parameters

KAS Parameter

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

Calibration method: MSD parameters (MSD = mass spectrometric detector)

Pyrolyse Parameter

TDU parameters (TDU = Thermal Desorption Unit)

Pyrolysis parameters

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

Sample method: MSD Parameter

Pyrolyse Parameter

TDU Parameter

Pyrolysis parameters

Key figures of the method

The evaluation was carried out using the MassHunter software.

The results shown in Table 50 clearly show 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 clear effect is also observed when ColdBox core sand is added. The emission potential is reduced by over 45% in the model case.

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, values “< ...” mean that the content of the corresponding BTEX compound is below its detection limit.

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

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

Claims

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, pouring in a mold comprising molding material bound with smectic clay, resulting in a poured molding material, Processing the cast molding material to produce a first processed molding material, in a later cycle of said two or more cycles of the molding material cycle, producing a molding material 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 mold material from uncast molds and/or cores and/or parts thereof, a third processed mold material produced by processing mold material from molds and/or cores and/or parts thereof cast outside the mold material cycle, an additive which contains at least one dehydratable inorganic compound which splits off water at a temperature of 150 °C or more, and optionally smectite-containing clay, wherein at least one of the processed mold materials contains organic binder and/or reaction products thereof, wherein the mold material produced in the later cycle contains carbon, wherein at least 70% by weight of this carbon originates from the organic binder and the reaction products. 2. The method according to claim 1, wherein the casting is carried out in a mold with at least one inserted core which was produced with an organic binder, resulting in a cast molding material which comprises material from the cast mold and material from the cast core. 3. A process according to claim 1 or 2, wherein the smectite-containing clay is bentonite. 4. Process according to one of the preceding claims, wherein the additive contains one or both compounds from the group consisting of aluminum hydroxide and magnesium hydroxide, wherein the proportion of aluminum hydroxide is preferably 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 in the additive. 5. A method according to any one of the preceding claims, wherein the casting of the mold is carried out with iron. 6. A method according to any one of the preceding claims, wherein the molding material produced in the later cycle has one or more of the following parameters - a concentration of less than 4%, preferably less than 3% carbon, 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% 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 Data Sheet P33 (April 1997). 7. Process according to one of claims 1 to 6, wherein the molding material produced in the later cycle contains carbon, wherein at least 80% by weight, preferably at least 90 and particularly preferably at least 95% by weight of this carbon originates from the organic binder and the reaction products. 8. Use of the additive as in claim 1 in a process according to any one of claims 1 to 7.