Method for guiding molding material in molding material cycle comprising two or more percycles

Abstract

A method for guiding a molding material in a molding material cycle comprising two or more cycles is described.

Description

Technical Field

[0001] The invention relates to a method for guiding molding material in a molding material circulation comprising two or more cycles. Background Art

[0002] Clays used to bind molding materials often contain smectite. Examples of such smectite-containing clays are bentonites, particularly sodium and calcium bentonites, which contain sodium or calcium in addition to 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 mixed with smectite-containing clays to serve as clay-containing binders.

[0003] The smectite-containing clay preferably has a montmorillonite content of 50% by weight or more, particularly preferably 60% by weight or more, and particularly preferably 70% by weight or more. If the montmorillonite content of the naturally occurring smectite-containing clay is too low, it can be increased by purification. This applies in particular to bentonite.

[0004] Sodium bentonite can contain, for example, 70 to 95% by weight of montmorillonite, with the remaining components being quartz, opal, cristobalite, feldspar, biotite, clinoptilolite, calcite, gypsum, and the like.

[0005] Correspondingly, in this document, the terms "smectite-containing clay" and "bentonite" are used both for the corresponding clays obtained from naturally occurring sources and for clays produced by purifying naturally occurring clays.

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

[0007] Suitable molding materials include any sand that can be molded and retain its shape at high temperatures and in contact with hot metal. Typical sands are silica sand, olivine sand, chromium ore sand, zircon sand, and artificial ceramic sand, or mixtures of these sands. The mold typically contains at least 40% sand, preferably more than 50%, particularly preferably more than 60%, and most preferably more than 70%.

[0008] In industrial practice, clay-bonded casting molds are typically made from a molding material that contains, in addition to a smectite-containing clay as a binder and a molding base, additives and water. This molding material is also known as "green sand" or "green sand." Compacting the molding material causes consolidation, thereby ensuring sufficient dimensional stability.

[0009] In industrial practice, molding materials having smectite-containing clay as a binder are often used for molding material circulation.

[0010] For the purposes of the present disclosure, molding material recycling means that molding material is recycled from a cast mold ("cast molding material," also called used sand) and used to produce new molding material, from which a cast mold is in turn produced. Thus, the molding base material contained in the molding material is at least partially present as a component of the molding material recycled from at least one already cast clay-bonded mold.

[0011] A molding material cycle, as used herein, consists of at least two temporally consecutive cycles. Thus, two (not necessarily directly consecutive) cycles of a molding material cycle can be classified as an earlier cycle and a later cycle. If a molding material cycle consists of only two cycles, the first cycle in temporal order is the earlier cycle, and the second cycle in temporal order is the later cycle.

[0012] The cycle of the molding material cycle can be described by the following characteristic steps (the following steps are named in Figure 1 ):

[0013] (Step 1) producing a molding material, i.e. producing a molding material comprising recycled molding material from an earlier cycle and additives (see below),

[0014] (Step 2) manufacturing a mold, that is, a mold made of the molding material manufactured in step (1) and bonded by clay containing smectite,

[0015] (Step 3) casting, i.e., producing a casting by casting into the mold produced in step (2), (Step 4) separation, i.e., separating the casting produced in step (3) from the mold, wherein a cast molding material is obtained, the molding material including material from the cast mold,

[0016] (Step 5) Regenerating the cast molding material, that is, regenerating the cast molding material in step (4) so that a regenerated first molding material is obtained to manufacture a new molding material in step (1) of a later cycle.

[0017] In certain cases it is preferred that one, more or all cycles of the molding material cycle include further steps and / or that each of the steps has further characteristics. Details on this will be found in the following description as well as in the appended claims and drawings.

[0018] In each cycle of the molding material circulation described above, a casting is produced in step (3) by casting the mold produced in step (2). During casting (step (3) of the cycle), the molding material undergoes significant material changes due to thermal and chemical stresses. To achieve the recycling of the molding material, the cast molding material must be regenerated.

[0019] In some cases, in particular for the production of castings with complex geometries, the mold produced in step (2) is cast in step (3) with one or more inserted cores (cf. Figure 3 ) mold to produce the casting. The core inserted into the clay-bonded mold is usually not bonded with clay. Such cores are usually made with an organic binder, such as polyurethane or phenolic resin, or with an inorganic binder that does not contain clay, such as a binder containing water glass. If the casting produced in step (3) is separated from the mold and core in step (4), a cast molding material is usually obtained, which contains material from the cast core (old core sand).

[0020] The regeneration of the cast molding material in step (5) results in regenerated molding material, which remains in the molding material circuit. Thus, part of the used molding base material (usually quartz sand) remains in the molding material circuit as a component of the regenerated cast molding material.

[0021] Regeneration generally involves comminuting the cast molding material (particle separation) and removing as much as possible metal residues and other impurities, for example in the form of secondary products from the casting process (core heads, feeder residues, etc.).

[0022] Thermal, mechanical and possibly chemical stresses during casting produce wear products such as fine sand fractions, inert clay fractions, decomposition products of additives, in particular bright carbon formers, reaction products of core binders and oolitic particles of the molding base.

[0023] In order to prevent such wear products from accumulating in the molding material cycle and / or from adversely affecting the molding material properties, or to prevent a significant reduction in the required active content of the binder (smectite-containing clay) and additives, in the corresponding subsequent cycle, an additive is added during the production of the molding material in step (1), i.e., the regenerated molding material is repaired by the additive. In order to maintain a constant quality of the molding material conducted in the cycle, a corresponding amount of molding material is removed from the molding material cycle. This can be done before the repair by the additive (i.e., in step (5)) or after the repair by the additive.

[0024] The feedstock typically includes smectite-containing clay, water, additives (see below), and one or more raw materials from the following groups:

[0025] - new molding substrate (new sand),

[0026] a recycled second moulding material produced by recycling uncast moulds and / or cores and / or parts thereof,

[0027] A recycled third molding material, which is produced by recycling molds and / or cores and / or parts thereof which were produced and cast outside the molding material cycle in question.

[0028] Preferably, the additive (especially bentonite) also includes water.

[0029] The molds and cores for obtaining the regenerated second and third molding materials defined above do not necessarily have to be made of clay. In particular, the cores are usually not made of clay, but are instead made of conventional organic binders, such as polyurethane, in particular polyurethane formed in the cold box process, or phenolic resins in the form of resols or novolacs, in particular resols used in the hot box or warm box process, in particular novolacs used in the cloning process or the screen molding process.

[0030] In each cycle of an industrial molding material circulation system, a substantially constant quality of the casting should be achieved during casting. By controlling the supply and removal of the molding material components, substantially constant, optimal molding material properties can be achieved during the molding material circulation system (molding material conditioning). The molding material is regulated, i.e., optimally set, in each cycle by determining the required addition rates of smectite-containing clay (optionally added), additives, water, and new sand or the regenerated second and third molding materials 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.

[0031] Moulding materials for producing clay-bonded casting moulds frequently contain additives in the form of so-called bright carbon formers in industrial practice.

[0032] Bright carbon former (also called bright carbon carrier See https: / / www.giesserei-praxis.de / giesserei-lexikon / glossar / glanzkohlenstoff ) are molding material additives that have the ability to form hydrocarbon-containing gases. During casting, these additives carbonize in the reducing atmosphere of the mold cavity. This produces bright carbon. Commonly used bright carbon formers include coal dust, wood pitch, bitumen, resins, oils, plastics, and mixtures thereof.

[0033] In particular, bright carbon formers are added to clay-bonded molding materials for cast iron. Bright carbon prevents wetting by the liquid casting material at the metal / mold interface. Furthermore, bright carbon formers in the molding material can dampen quartz expansion and prevent sand expansion defects. However, an increased content of coal dust or other bright carbon formers in the recycled molding material, or a higher content of bright carbon former decomposition products (coke), increases the water requirement of the molding material. This increased water content in the molding material can lead to casting defects, such as cracking and penetration.

[0034] Since the bright carbon former undergoes thermal decomposition and carbonization during casting, in industrial practice, the corresponding loss in the molding material circulation must be replaced regularly by supplying new bright carbon former. To this end, the bright carbon former is added freshly at least in some cycles of the molding material circulation, preferably in all cycles.

[0035] A substantial disadvantage of using bright carbon formers is the release of emissions such as CO, CO2, NO x These emissions occur in the form of volatile organic compounds, particularly aromatic hydrocarbons such as benzene, toluene, and xylene ("BTX emissions"), as well as polycyclic aromatic hydrocarbons. Additionally, volatile sulfur compounds are often emitted, as bright carbon formers often contain sulfur and / or sulfur-containing impurities. Another problem is the significant risk of dust explosions and spontaneous combustion when handling bright carbon formers. Therefore, in industrial foundry operations, when producing clay-bonded molds, bright carbon formers are often used in the form of prefabricated supplier-prepared mixtures with smectite-containing clays, particularly bentonite.

[0036] For the reasons stated, it is desirable and necessary to limit the use of bright carbon formers or to replace at least a significant portion of bright carbon formers by suitable alternatives.

[0037] US Pat. No. 5,372,636 A discloses a molding material comprising sand, sodium montmorillonite clay (especially sodium bentonite), and at least one oxide, salt (especially carbonate), or hydroxide of a metal, such as aluminum, calcium, iron, sodium, magnesium, boron, or zinc. The use of the molding material in a recycling process is not disclosed. Therefore, the document provides no information on whether the molding material is suitable for molding material recycling.

[0038] WO 03 / 066253 A1 describes a method for producing a molding material, particularly one for casting purposes, which is circulated in a circuit, wherein a material that does not swell in water is added to a mixture of granular material, additives, such as a binder (e.g., bentonite), and water. In particular, framework or tectosilicates, such as zeolite, pumice, allophane, imogolite, diatomaceous earth, hydrated aluminum magnesium silicate, sepiolite, diatomite, or (acid- and / or heat-treated) clay, are used as the non-swellable porous material.

[0039] CN 108356214 discloses a molding material mixture comprising sand, water, bentonite and an additive having the following composition

[0040] SiO2 50 wt%-85 wt%

[0041] Al2O3 9 wt%-45 wt%

[0042] MgO 0.2 wt%-3 wt%

[0043] Fe2O3 1 wt%-8 wt%

[0044] CaO 1 wt%-7 wt%

[0045] Fe3O4 0.4 wt%-8 wt%

[0046] The additive is produced by mixing individual oxides. The additive should replace the bright carbon former. The molding material containing the additive should be easily recyclable. Exemplary molding materials have been in use for more than two to four months. Summary of the Invention

[0047] This object is achieved by a method for guiding molding material in a molding material circulation comprising two or more cycles, the method comprising the following steps:

[0048] - casting in a mould comprising the moulding material bound with a smectite-containing clay during an earlier one of said two or more cycles of the moulding material circulation,

[0049] - regenerating the cast molding material so as to obtain a regenerated first molding material,

[0050] - producing, in a later cycle of said two or more cycles of said molding material circulation, a molding material comprising:

[0051] (i) a recycled first molding material,

[0052] as well as

[0053] (ii) Additives, including

[0054] an additive containing at least one dehydratable inorganic compound which separates water at a temperature of 150° C. or higher,

[0055] - one or more raw materials from the following groups

[0056] - a molded substrate,

[0057] a recycled second molding material produced by recycling molding material from an uncast mold and / or core and / or parts thereof,

[0058] a recycled third molding material produced by recycling molds and / or cores and / or parts thereof cast outside the molding material circulation,

[0059] - and optionally, a smectite-containing clay, preferably bentonite,

[0060] In this case, the total proportion of material from the mold and the core formed by the molding material bonded by a binder other than the smectite-containing clay in the produced molding material is less than 10% by weight.

[0061] Preferably, the additive also includes water.

[0062] Preferably, the total proportion of material from the mold and the core formed from the molding material bonded by a binder other than the smectite-containing clay in the produced molding material is less than 5% by weight, particularly preferably less than 1% by weight.

[0063] Preferably, at least 90% by weight, preferably at least 99% by weight and particularly preferably 100% by weight of the recycled second molding material and the recycled third molding material come from molds and / or cores bonded with smectite-containing clay.

[0064] Preferably, at most 10% by weight, preferably at most 1% by weight and particularly preferably 0% by weight, of the recycled second molding material and the recycled third molding material come from molds and / or cores produced with a binder other than smectite-containing clay.

[0065] Preferred is a method in which a cast molding material is obtained during casting that does not contain material from the cast core. This is achieved by separating the cast molding material from the cast core molding material (old core sand) when separating the produced casting from the mold and at least one core, or by using a mold without a core.

[0066] Preferably, the casting is carried out in a mold without a core.

[0067] Likewise preferred is casting in a mold having a core, wherein the core is bonded with a smectite-containing clay.

[0068] Preferably, the recycled molding material contains no organic binders, preferably no organic material at all. Preferably, the recycled molding material contains no carbon and no carbon carrier.

[0069] Preferably, no carbon and no carbon carrier are added during the production of the molding material (as described above).

[0070] This means that there is a molding material cycle that is as inorganic as possible.

[0071] The carbon content of the molding material is determined by elemental analysis and includes the carbon content originating from the organic carbon carrier and the carbon content originating from the inorganic carbon carrier. The organic carbon carrier is, in particular, a bright carbon former, an organic binder, an organic additive, and residues or decomposition products of the bright carbon former, the organic binder, and the organic additive. The inorganic carbon carrier is, in particular, carbonates that may be present in the molding material.

[0072] In particular, in molding materials having smectite-containing clays as binders, the carbon content can be reduced by reducing or avoiding the use of bright carbon formers.

[0073] By reducing or even avoiding the use of bright carbon formers, fossil resources are conserved. Therefore, a further object achieved by the present invention is to provide a resource-saving molding material cycle.

[0074] By reducing or even avoiding the use of bright carbon forming agents, the risk of dust explosions and spontaneous combustion during the transportation, storage, and handling of bright carbon forming agents is reduced or even eliminated. Therefore, another object achieved by the present invention is to reduce the risk of dust explosions and spontaneous combustion during the transportation, storage, and handling of bright carbon forming agents.

[0075] By reducing or even eliminating the use of bright carbon formers, fewer pyrolysis products are produced during casting that could contaminate the cast molding material or be removed from the molding material cycle. The lower carbon and sulfur content in the molding material, resulting from the reduced use of bright carbon formers, also facilitates the landfilling of non-reusable molding material portions. Therefore, another object achieved by the present invention is to simplify the reuse or landfilling of cast molding material.

[0076] A further object achieved by the present invention is therefore to reduce sulfur-based emissions and NOx emissions during a molding material circulation comprising two or more cycles.

[0077] Another object achieved by the present invention is to reduce odor pollution released during casting.

[0078] The reduction in the bright carbon content should not lead to unacceptable impairment of the properties of the molding material, the casting mold produced from the molding material, and the casting produced therefrom.

[0079] The molding material circuit relevant for the method of the invention is preferably an industrial molding material circuit of a foundry, preferably with at least one production line integrated into the molding material circuit and optionally with at least one further production line.

[0080] Further features, details, advantages and preferred embodiments of the method of the invention are described in the following description as well as in the appended claims and drawings.

[0081] The solution to the object defined above is based on the use of an additive that has an effect similar to that of the bright carbon formers used in the prior art with respect to avoiding mold expansion defects, with respect to separation between metal and molding material, and with respect to promoting mold decomposition. Surprisingly, it has been found that dehydratable inorganic compounds that separate water at temperatures of 150° C. or higher can achieve an effect similar to that of the bright carbon formers used in the prior art with respect to avoiding mold expansion defects and promoting mold decomposition.

[0082] Dehydration means separating chemically (for example in the form of hydroxide ions) or physically (for example as water of crystallization in hydrates) bound water by heating.

[0083] The dehydratable inorganic compound contained in the additive to be used according to the invention is preferably a compound from the group of metal hydroxides and hydrated salts. The term hydroxide, as used herein, also includes oxyhydroxides. Preference is given to metal hydroxides and hydrated salts in the +II or +III oxidation state, particularly preferred to metal hydroxides in the +II or +III oxidation state. Particularly preferred are magnesium hydroxide (especially in the form of brucite) and aluminum hydroxide, most preferred being aluminum oxide trihydrate Al(OH)3. Aluminum oxide can be present in various modified forms, especially as gibbsite, bayerite, or nordstrandite, and in combination with other hydroxides or oxides in minerals.

[0084] Preferably, the additive contains one or two compounds from the group consisting of aluminum hydroxide and magnesium hydroxide. With respect to the total mass of aluminum hydroxide and magnesium hydroxide in the additive, the proportion of magnesium hydroxide is 0 to 100%.

[0085] The additives to be used according to the invention preferably do not comprise carbon or carbon supports.

[0086] In the preferred embodiment of the method according to the present invention, in an earlier cycle of two or more cycles of the molding material circulation, a mold bonded with smectite-containing clay is cast, producing a casting. Casting the mold yields a cast molding material. The cast molding material is regenerated in the aforementioned manner to yield a regenerated first molding material. To maintain a constant quality of the molding material conducted through the circulation, a portion of the cast molding material may optionally be removed during regeneration to yield a removed molding material.

[0087] However, it is not mandatory to remove the regenerated molding material in every cycle of the molding material circulation. The molding material circulation according to the invention may include individual cycles in which the regenerated molding material is not removed.

[0088] In a later period of the molding material cycle, a molding material is produced, said molding material comprising (i) the recycled first molding material as defined above, and (ii) an additional material.

[0089] - additives as defined above,

[0090] - and one or more raw materials from the following groups,

[0091] - mold base material, especially quartz sand,

[0092] a recycled second molding material produced by recycling molding material from an uncast mold and / or core and / or parts thereof,

[0093] a recycled third molding material produced by recycling molding material from molds and / or cores and / or parts thereof cast outside of the molding material circuit,

[0094] - and preferably a smectite-containing clay, preferably a bentonite.

[0095] If a portion of the cast molding material is not removed after regeneration, then in order to maintain a constant quality of the molding material conducted in the cycle, a portion of the produced molding material can be removed, resulting in a removed molding material. However, this is not absolutely necessary. The molding material circulation according to the invention can include individual cycles in which no molding material is removed.

[0096] The molding material produced in a later cycle of the molding material cycle comprises one, more or all of the above raw materials. The molding substrate used as raw material preferably comprises new molding substrate (new sand).

[0097] The smectite-containing clay is preferably a bentonite, in particular a bentonite from the group consisting of sodium bentonite and calcium bentonite and mixtures thereof.

[0098] The regenerated second molding material as defined above is produced by regenerating molding material from uncast molds and / or cores and / or parts thereof. Uncast molds and / or cores are molds and / or cores that have not been cast for various reasons, such as due to machining defects or insufficient dimensional accuracy.

[0099] The recycled third 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 in question, ie molds and cores cast in another production line, for example.

[0100] Preferably, no recycled molding material is used which contains material from cast or uncast molds and / or cores and / or parts thereof, wherein the molds and / or cores are produced with organic binders or inorganic binders without clay, such as binders containing water glass.

[0101] Molded materials manufactured in later cycles have one or more of the following parameters:

[0102] - a carbon concentration of less than 1.5%, preferably less than 0.8%, based on the mass of the molding material, determined by means of elemental analysis

[0103] - a nitrogen concentration of less than 0.1%, preferably less than 0.05%, based on the mass of the molding material, determined by means of elemental analysis

[0104] - a sulfur concentration of less than 0.05%, preferably less than 0.03%, based on the mass of the molding material, determined by means of elemental analysis

[0105] - a ignition loss of at most 5%, preferably at most 3.5%, determined in accordance with VDG Practice Specification P33 (April 1997).

[0106] Particularly preferably, the molding material produced in the later cycle has one or more of the following parameters:

[0107] a carbon concentration of less than 0.8%, preferably less than 0.4%, particularly preferably less than 0.2%, based on the mass of the molding material, determined by means of elemental analysis,

[0108] a nitrogen concentration of less than 0.05%, preferably less than 0.03%, particularly preferably less than 0.01%, based on the mass of the molding material, as determined by means of elemental analysis,

[0109] a sulfur concentration of less than 0.03%, preferably less than 0.01%, more particularly preferably less than 0.005%, based on the mass of the molding material, as determined by means of elemental analysis,

[0110] - a ignition loss of at most 3.5%, preferably at most 3%, particularly preferably at most 2.5%, determined in accordance with VDG Practice Specification P33 (April 1997).

[0111] Preferably, all the above-mentioned parameters of the molding material are within the above-mentioned preferred, especially the above-mentioned particularly preferred, ranges.

[0112] In one embodiment of the method according to the invention, casting is performed in an early cycle in a mold having at least one inserted core. Cores inserted into clay-bonded molds are typically not bonded with clay. Such cores are typically made with an organic binder, such as a cold box binder, or with an inorganic binder other than smectite-containing clays, such as a binder containing water glass. When the produced casting is separated from the mold and the at least one core, the cast molding material is separated from the cast core molding material (used sand).

[0113] In one embodiment of the method of the present invention, in an earlier cycle, casting is performed in a mold into which at least one clay-bonded core is inserted. Thus, the cast molding material contains material from the cast clay-bonded mold and the cast clay-bonded core.

[0114] In a further particularly preferred embodiment of the method according to the invention, in an early cycle, casting takes place in a mold without an inserted core, so that the regenerated first molding material contains no material from the cast core.

[0115] In all the above-described embodiments of the method according to the invention, preferably at least 90% by weight, preferably at least 99% by weight and particularly preferably 100% by weight of the recycled second molding material and the recycled third molding material (as defined above) come from clay-bound molds and / or cores. In this embodiment of the method according to the invention, preferably at most 10% by weight, preferably at most 1% by weight and particularly preferably 0% by weight of the recycled second molding material and the recycled third molding material come from molds and / or cores produced with a binder other than smectite-containing clay.

[0116] More particularly preferably, no recycled molding material is used which contains material from cast or uncast molds and / or cores and / or parts thereof, wherein the molds and / or cores were produced with an organic binder or with an inorganic binder that does not contain clay, for example a binder containing water glass.

[0117] In the method according to the invention, the molding material guided in circulation is preferably used to produce a mold for cast iron, ie the mold is cast with iron.

[0118] In the method according to the invention, earlier and later cycles, and preferably all cycles, of the method according to the invention preferably comprise the following steps (cf. Figure 2 , whose other characteristics shall not have a limiting effect):

[0119] (Step 1) Manufacturing a molding material, i.e., manufacturing a molding material comprising:

[0120] (i) a recycled first molding material as defined above which is produced by recycling a cast molding material obtained in an earlier cycle of the molding material cycle,

[0121] as well as

[0122] (ii) additives as defined above,

[0123] (Step 2) manufacturing a mold, that is, manufacturing a mold bonded with smectite-containing clay from the molding material manufactured in step (1),

[0124] (Step 3) casting, i.e., producing a casting by casting in the mold produced in step (2), wherein the casting is performed in the mold without inserting a core,

[0125] (Step 4) separation, i.e. separation of the casting produced in step (3) from the mold, wherein a cast molding material is obtained,

[0126] (Step 5) Regenerating the cast molding material, i.e., regenerating the cast molding material in step (4) to obtain a regenerated first molding material to manufacture a new molding material in step (1) of a later cycle, and optionally removing a portion of the cast molding material to obtain a molding material that has been removed.

[0127] If part of the cast molding material is not removed during the regeneration in step (5), then in order to keep the mass of the molding material conducted in the cycle constant, part of the molding material produced in step (1) of the next cycle is removed, so that a molding material that has been removed is obtained.

[0128] In a particular embodiment of the method according to the invention, the earlier and later cycles and preferably all cycles of the method according to the invention preferably comprise the following steps (cf. Figure 4 , whose other characteristics shall not have a limiting effect):

[0129] (Step 1) manufacturing a molding material, that is, manufacturing a molding material comprising the following,

[0130] (i) recycled moulding material as defined above which is produced by recycling cast moulding material obtained in an earlier cycle of the moulding material cycle,

[0131] as well as

[0132] (ii) additives as defined above,

[0133] (Step 1a) producing a core molding material, i.e. producing or providing a molding material for producing at least one core, preferably with smectite-containing clay as a binder,

[0134] (Step 2) Manufacturing a mold, that is, manufacturing a mold bonded with smectite-containing clay from the molding material manufactured in step (1)

[0135] (Step 2a) manufacturing a core, i.e., manufacturing at least one core and inserting the at least one core into the mold manufactured in step (2),

[0136] (Step 3) Casting, i.e., producing a casting by casting the mold produced in step (2) with at least one core inserted in step (2a),

[0137] (Step 4) separation, i.e. separation of the casting produced in step (3) from the mold and at least one core, wherein the cast molding material is separated from the cast core molding material (used sand) without the core being bonded with clay,

[0138] (Step 5) Regenerating the cast molding material, i.e., regenerating the cast molding material in step (4) to obtain a regenerated first molding material for manufacturing a new molding material in step (1) of a later cycle, and optionally removing a portion of the cast molding material to obtain a molding material that has been removed.

[0139] If part of the cast molding material is not removed during the regeneration in step (5), then in order to keep the mass of the molding material conducted in the cycle constant, part of the molding material produced in step (1) of the next cycle is removed, so that a molding material that has been removed is obtained.

[0140] In certain cases, it is preferred that one, more or all cycles of the molding material cycle include further steps and / or that individual ones of the steps have further characteristics. Details on this can be found in the following description as well as in the appended claims and the drawings.

[0141] In particular, when producing the molding material in step (1) of the molding material recycling, the recycled molding material is preferably mixed with an additive. Preferably, the additive also includes water.

[0142] Preferably, the mould with the casting and, if present, the at least one core is cooled before separation in step (4).

[0143] Preferably, the cast molding material is cooled before regeneration.

[0144] Regeneration generally involves the removal of metal residues and other impurities, such as those resulting from secondary products of the casting process (core heads, riser residues, etc.), as well as the comminution of the cast molding material (particle separation).

[0145] Thermal, mechanical and possibly chemical stresses generate wear products such as fine sand fractions, inert clay fractions, decomposition products of additives and / or bright carbon formers, or reaction products of core binders and oolitic particles of the molding base.

[0146] In order to prevent such wear products from accumulating in the molding material cycle and / or from adversely affecting the molding material properties and / or in order to prevent a sharp reduction in the required active ingredients of the binder (smectite-containing clay) and the additive to be used according to the invention, in the corresponding subsequent cycle, in particular in step (1), during the production of the molding material, an additive is added to the molding material, i.e., the regenerated molding material is repaired by the additive. In order to keep the quality of the molding material guided in the cycle constant, a corresponding amount of molding material is removed from the molding material cycle. This can be done before the repair by the additive (i.e., in particular in step (5)), or after the repair by the additive, i.e., after the molding material is produced in a later cycle. In the latter case, the amount of additive added is kept as low as possible.

[0147] Therefore, in some cases, step (5) involves: necessarily removing the same amount of cast molding material as is repaired in step (1) of the next cycle by the addition of material including the additive to be used according to the invention; it is possible in this way to achieve a uniform level of properties.

[0148] Preferably, in step (5), 0.5% to 20% by weight, preferably 2% to 15% by weight, particularly preferably 5% to 10% by weight of the cast molding material is removed (sand removal), and a corresponding amount of additive is added in step (1) of the next cycle in order to keep the mass of the molding material conducted in the cycle constant.

[0149] If no part of the cast molding material is removed in step (5), then in order to keep the mass of the molding material guided in the circuit constant, 0.5% to 20% by weight, preferably 2% to 15% by weight, particularly preferably 5% to 10% by weight of the molding material produced in step (1) is removed.

[0150] The molded material removed during the recycling in step (5) preferably meets the requirements of landfill class DKI according to Annex 3 of the Landfill and Long-term Storage Ordinance of April 27, 2009 (Landfill Ordinance - DepV).

[0151] The molding material circulation involved in the method according to the invention preferably comprises at least 10 cycles, preferably at least 15 cycles, particularly preferably at least 30 cycles.

[0152] The additive to be used according to the invention (as defined above) is preferably free-flowing and / or pourable. The additive is preferably present in the form of a powder or granules. The additive is particularly preferably present in the form of granules having a particle size of 20 to 200 μm, as determined by a laser particle size analyzer.

[0153] Preferably, the fraction of the dehydratable inorganic compound that separates out water at a temperature of 150° C. or higher, based on the total mass of the additive as defined above, is 1% to 100%. Particularly preferably, the fraction of the dehydratable inorganic compound that separates out water at a temperature of 150° C. or higher, based on the total mass of the additive as defined above, is 20% to 100%. More particularly preferably, the fraction of the dehydratable inorganic compound that separates out water at a temperature of 150° C. or higher, based on the total mass of the additive as defined above, is 30% to 100%. Particularly preferably, the fraction of the dehydratable inorganic compound that separates out water at a temperature of 150° C. or higher, based on the total mass of the additive as defined above, is 50% to 100%.

[0154] The additive preferably contains aluminum hydroxide, wherein 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 is aluminum hydroxide having a water content of less than 1% (i.e., a water content of less than 1%) as determined by thermogravimetric analysis in a temperature range of up to 105° C. Thus, drying the aluminum hydroxide does not require a particularly high level of effort.

[0155] In the additive, the aluminum hydroxide can be present in the form of a mixture with iron oxide and / or iron hydroxide, wherein the proportion of the aluminum hydroxide is greater than 40%, based on the total mass of the aluminum hydroxide, iron oxide and / or iron hydroxide.

[0156] The pH value of the additive to be used according to the invention is preferably in the range from 7 to 14, as determined in accordance with DIN 19747:2009-07 (sample preparation), DIN EN 12457-1:2003-01 (leaching) and DIN EN ISO 10523:2012-04 (pH determination).

[0157] Preferably, the additive to be used according to the invention contains one or more dehydratable inorganic compounds which separate out water in the temperature range from 150°C to 850°C.

[0158] 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 Cl, based on the total mass of the additive, is 1 weight % or less, preferably 0.5 weight % or less, particularly preferably 0.1 weight % and more particularly preferably 0.05 weight %.

[0159] When manufacturing the molding material, the order in which the individual components are added together is flexible.

[0160] The additive can be provided, for example, as a mixture.

[0161] Alternatively, the additives, i.e., the additive and the smectite-containing clay, can be provided as a mixture, and the other additives can be provided separately. This corresponds to the currently common practice of providing the bright carbon former in a prefabricated mixture with the smectite-containing clay. Thus, existing foundry equipment can continue to be used for storage and dosing.

[0162] Alternatively, the additive can be provided separately from the other additives.

[0163] Alternatively, the additive and optionally the smectite-containing clay, or a premix of the additive and the smectite-containing clay, can first be mixed with the recycled first molding material and the further raw materials as described above can then be added.

[0164] Preferably, based on the total mass of the molding material to be produced,

[0165] - a molded substrate,

[0166] a recycled second molding material produced by recycling molding material from an uncast mold and / or core and / or parts thereof,

[0167] a recycled third molding material produced by recycling molds and / or cores and / or parts thereof cast outside the molding material circulation,

[0168] The total mass of the raw materials in the constituted group is 0.5% by weight to 10% by weight, preferably 1% by weight to 8% by weight, and particularly preferably 1.5% by weight to 7% by weight.

[0169] The mass of the smectite-containing clay fed as an 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.

[0170] The total mass of the dehydratable inorganic compound that separates water at a temperature of 150° C. or higher, which is added as an additive, is 0.1 to 1% by weight, preferably 0.3 to 0.8% by weight, and particularly preferably 0.4 to 0.7% by weight, based on the total mass of the molding material to be produced.

[0171] The smectite-containing clay to be used in the process according to the invention is preferably a bentonite, particularly preferably selected from the group consisting of sodium bentonite, calcium bentonite and mixtures thereof.

[0172] Preferably, the molding substrate is selected from the group consisting of quartz sand, olivine sand, chromium ore sand, zircon sand and artificial ceramic sand, and mixtures of said sands. Clay-bonded molds typically contain at least 40% sand, preferably more than 50% sand, particularly preferably more than 60% sand, and very particularly preferably more than 70% sand.

[0173] The method is preferably designed such that at least 90% by weight of the molding material is subjected to temperatures of up to 1000° C. during casting. At temperatures above 1000° C., aluminum hydroxide is irreversibly converted into corundum (α-aluminum hydroxide), which cannot be converted back into aluminum hydroxide in a later cycle by adding water in step (1) and is therefore no longer able to act as an additive according to the invention as defined above.

[0174] It is therefore preferred that less than 50% by weight, preferably less than 25% by weight and particularly preferably less than 10% by weight of the Al 2 O 3 contained in the molding material is present in the form of corundum.

[0175] Preferably, the molding material produced in a later cycle of the method according to the invention has the following parameters:

[0176] - a degree of compaction in the range of 25% to 55%, determined in accordance with VDG Practice Guidelines P37 (April 1997), and / or

[0177] - at 8N / cm 2 Up to 35N / cm 2 Wet compressive strength within the range, determined according to VDG Practice P38 (May 1997), and / or

[0178] - at 0.10N / cm 2 Up to 0.50N / cm 2 Wet tensile strength within the range, determined according to VDG Practice P38 (May 1997), and / or

[0179] - an air permeability in the range of 70 to 200, determined according to BDG Guideline P41 (October 2013), and / or

[0180] - an active clay content in the range of 6% to 14%, determined by the methylene blue method according to VDG Practice P035 (October 1999), and / or

[0181] - 20% to 90% mobility, determined according to the technical documentation on the operation of the Morek Multiserw, LUA-2e type pile driver with electric drive, page 7.

[0182] Particularly preferably, the molding material produced in a later cycle of the method according to the invention has the following parameters:

[0183] - a degree of compaction in the range of 30% to 50%, determined in accordance with VDG Practice Guidelines P37 (April 1997), and / or

[0184] - at 10N / cm 2 Up to 28N / cm 2 Wet compressive strength within the range, determined according to VDG Practice P38 (May 1997), and / or

[0185] - at 0.20N / cm 2 Up to 0.45N / cm 2 Wet tensile strength within the range, determined according to VDG Practice P38 (May 1997), and / or

[0186] - an air permeability in the range of 90 to 160, determined according to BDG Guideline P41 (October 2013), and / or

[0187] - an active clay content in the range of 6% to 14%, determined by the methylene blue method according to VDG Practice P035 (October 1999), and / or

[0188] - 50% to 90% mobility, as determined on page 7 of the Morek Multiserw, technical documentation on the operation of pile drivers with electric drive, type LUA-2e.

[0189] Preferably, all the above parameters of the molding material are within the above preferred ranges, in particular within the above particularly preferred ranges.

[0190] Another aspect of the present disclosure relates to the use of the additives defined above in the method according to the invention as defined above.With regard to the additives preferably to be used and the preferred method configurations, the above embodiments apply. BRIEF DESCRIPTION OF THE DRAWINGS

[0191] The present invention will be described in detail below based on the schematic drawings.

[0192] Figure 1 Shows the molding material circulation according to the prior art (casting in a coreless mold)

[0193] Figure 2 Illustration of the molding material circulation according to the method of the invention (casting in a coreless mold)

[0194] Figure 3 Shows the molding material circulation according to the prior art (casting in a mold with a core)

[0195] Figure 4Figure 2 shows the molding material circulation according to the method according to the invention (casting in a mold with a clay-bonded core) DETAILED DESCRIPTION

[0196] The cycle of molding material circulation is based on Figure 1 and Figure 2 At least steps (1) to (5) as defined above are included, wherein the mold for casting in step (3) does not contain an inserted core.

[0197] In step (1), a molding material is produced, the molding material comprising:

[0198] (i) a recycled first molding material produced by recycling cast molding material obtained in an earlier cycle of the molding material cycle, said recycled first molding material containing no material from the cast cores,

[0199] as well as

[0200] (ii) Additives.

[0201] Additives include:

[0202] - one or more raw materials from the following groups

[0203] - New molding substrate (new sand),

[0204] - and at least one recycled molding material from the group consisting of

[0205] a recycled second moulding material produced by recycling uncast moulds and / or cores and / or parts thereof,

[0206] - Recycled third molding material, which is recycled in Figure 1 or Figure 2 The molding material shown is produced outside the cycle and is produced by casting molds and / or cores and / or parts thereof,

[0207] - smectite-containing clay, preferably bentonite,

[0208] -water.

[0209] Preferably, at least 90% by weight, preferably at least 99% by weight, and particularly preferably 100% by weight of the recycled second molding material and the recycled third molding material come from clay-bound molds and / or cores. In this embodiment of the method according to the invention, at most 10% by weight, preferably at most 1% by weight, and particularly preferably 0% by weight of the recycled second molding material and the recycled third molding material come from molds and / or cores produced with a binder other than smectite-containing clay.

[0210] In a method not according to the invention ( Figure 1 ), in step (1) at least one bright carbon former is added as a further additive during the production of the molding material.

[0211] In the method according to the present invention ( Figure 2 ), in step (1), when producing the molding material, the additive defined above is added as another additive. Preferably, the additive comprises magnesium hydroxide and / or aluminum trihydrate or consists of magnesium hydroxide and / or aluminum trihydrate. Preferably, (as described above) when producing the molding material, no carbon and carbon carrier are added. That is, in the method according to the present invention ( Figure 2 ) in which there is a cycle of molding material that is as inorganic as possible.

[0212] In step (2), a mold bonded with smectite-containing clay is manufactured from the molding material manufactured in step (1).

[0213] In step (3), a casting is produced by casting into the mold produced in step (2). The mold does not contain an inserted core.

[0214] In step (4), the casting produced in step (3) is separated from the mold, resulting in a cast molding material that contains material from the cast mold but does not contain material from the cast core. The mold with the casting is preferably cooled before separation in step (4).

[0215] In step (5), the cast molding material from step (4) is regenerated to obtain a regenerated first molding material for producing new molding material in a later step, in particular, in the next cycle, step (1). Preferably, the cast molding material is cooled before the regeneration in step (5). During the regeneration, a portion of the cast molding material may be removed to obtain a removed molding material.

[0216] If part of the cast molding material is not removed during the regeneration in step (5), then in order to keep the mass of the molding material guided in the cycle constant, part of the molding material produced in step (1) of the next cycle is removed, so that a molding material that has been removed is obtained.

[0217] In a later, in particular next cycle, step (1), the recycled first molding material obtained in an earlier, in particular previous cycle, step (5) is used to produce new molding material in the manner described above.

[0218] One cycle of the molding material cycle is based on Figure 3 and Figure 4The method comprises at least steps (1), (1a), (2), (2a), (3), (4) and (5) as defined above, wherein the mold for casting in step (3) comprises at least one core bonded with clay containing smectite.

[0219] The step (1) of producing a molding material comprises:

[0220] (i) a recycled first molding material produced by recycling cast molding material obtained in an earlier cycle of the molding material cycle, the recycled first molding material comprising material from the cast cores,

[0221] as well as,

[0222] (ii) Additives.

[0223] Additives include:

[0224] - One or more raw materials from the following groups:

[0225] - New molding substrate (new sand),

[0226] - and at least one recycled molding material from the following group:

[0227] - Regenerated second molding material, which is recycled in Figure 3 or Figure 4 The mold and / or core and / or parts thereof are produced outside the molding material cycle and are cast,

[0228] a recycled third molding material produced by recycling uncast molds and / or cores and / or parts thereof,

[0229] - smectite-containing clay, preferably bentonite,

[0230] -water.

[0231] Preferably, at least 90% by weight, preferably at least 99% by weight, and particularly preferably 100% by weight of the recycled second molding material and the recycled third molding material originate from clay-bound molds and / or cores. In this embodiment of the method according to the invention, at most 10% by weight, preferably at most 1% by weight, and particularly preferably 0% by weight of the recycled second molding material and the recycled third molding material originate from molds and / or cores produced with a binder other than smectite-containing clay.

[0232] In a method not according to the invention ( Figure 3 ), in step (1) at least one bright carbon former is added as a further additive during the production of the molding material.

[0233] In the method according to the present invention ( Figure 4), in step (1), when producing the molding material, the additive defined above is added as another additive. Preferably, the additive contains aluminum trihydrate and / or magnesium hydroxide or consists of aluminum trihydrate and / or magnesium hydroxide. Preferably, (as described above) no carbon and carbon carrier are added when producing the molding material. That is, in the method according to the present invention ( Figure 4 ) in which there is a cycle of molding material that is as inorganic as possible.

[0234] In step (1a), a molding material (core molding material) for producing at least one core is produced or provided. The molding material comprises a molding base material, a smectite-containing clay as a binder, and any additives. Additives suitable for producing core molding materials are known from the prior art.

[0235] In step (2), a mold bonded with smectite-containing clay is manufactured from the molding material manufactured in step (1).

[0236] In step (2a), at least one core is manufactured from the molding material (core molding material) manufactured or provided in step (1a), and inserted into the mold manufactured in step (2).

[0237] In step (3), a casting is produced by casting into the mold produced in step (2), said mold including at least one inserted core.

[0238] In step (4), the casting produced in step (3) is separated from the mold, whereby a cast molding material is obtained, which includes material from the cast clay-bonded mold and material from the cast clay-bonded core.

[0239] Preferably, the mold with the casting is cooled before separation in step (4).

[0240] In step (5), the cast molding material from step (4) is regenerated to obtain a regenerated first molding material for producing new molding material in a later step, in particular, in the next cycle, step (1). Preferably, the cast molding material is cooled before the regeneration in step (5). During the regeneration, a portion of the cast molding material is removed, if necessary, to obtain a removed molding material.

[0241] If part of the cast molding material is not removed during the regeneration in step (5), then in order to keep the mass of the molding material guided in the cycle constant, part of the molding material produced in step (1) of the next cycle is removed, so that a molding material that has been removed is obtained.

[0242] In a later, in particular next cycle, step (1), the recycled first molding material obtained in an earlier, in particular previous cycle, step (5) is used to produce new molding material in the manner described above.

[0243] The present invention is further described below by way of non-limiting examples.

[0244] 0. Test methods and molding materials

[0245] 0.1 Test Method

[0246] The following test methods (measurement methods) were used (Table 1)

[0247] Table 1: Measurement methods used

[0248]

[0249]

[0250] The sleeve and fin model apparatus was fabricated as described in (https: / / www.researchdisclosure.com / database / RD705032) and used for the following experiments.

[0251] 0.2 Materials used

[0252] All specifications for the dosage of the raw materials relate in each case to the pure raw materials, ie dry materials, ie without any moisture or water of crystallization present.

[0253] In the test, molding material from a regulated molding material circulation system at a brake disc foundry (hereinafter also referred to as starting molding material) was used as the starting material for the test of converting a molding material circulation system containing a bright carbon former. This molding material can be described by the following data (Table 2).

[0254] Table 2: Parameters of starting molding materials

[0255]

[0256]

[0257] In the experimental investigations, a regenerated molding material from core sand (the regenerated second molding material defined above) was used. For this purpose, cores were produced with an organic or inorganic binder and subsequently ground using a circular vibrating screen from Webac.

[0258] The starting material for the molding material produced using an organic binder was a core produced using the cold-box process. This core was produced using the binder Biocure 8568P1 / Silcure 8431P2 sold by Hüttenes-Albertus Chemische Werke GmbH (Germany) on a core shooter LL20 from Laempe. Quarzwerke H32 molding sand was used, with 0.7 parts by weight of the binder component per 100 parts by weight of sand. The core was produced using a shot pressure of 450 kPa (4.5 bar) and a shot time of 1.5 seconds. Subsequently, 10 g of dimethylpropylamine (N,N-dimethylpropylamine, catalyst GH6 from Hüttenes-Albertus Chemische Werke GmbH, Germany) was passed through for 45 seconds at a supply pressure of 200 kPa (2 bar) for curing.

[0259] The starting material for the molding material produced using an inorganic binder is a core produced on a Laempe coreshooter LL20 using the binder system Cordis 9477 / Anorgit 9476, marketed by Eurochemie GmbH. Quarzwerke H32 molding sand was used, and the binder composition consisted of 2.2 parts by weight of Cordis 9477 and 1.15 parts by weight of Anorgit 9476 per 100 parts by weight of sand. The cores were produced in a core box conditioned to 180°C using a shot pressure of 450 kPa (4.5 bar) and a shot time of 1.5 seconds. To cure, hot air at 120°C was passed through the core at a supply pressure of 200 kPa (2 bar) for one minute.

[0260] The cores were ground using a circular vibrating sieve (Kreisschwingsieb-175056 testing machine from Webac). The resulting molding material had the properties listed in Table 3.

[0261] Table 3: Parameters of the recycled molding material from core sand

[0262]

[0263] The abbreviation NG indicates that the measured value is below the detection limit

[0264] The starting materials for the cores that did not decompose under the test conditions (i.e., the cores that did not decompose during the separation (step (4)), see below, point 3, test series A) were 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 from Eurochem GmbH combined with silica fume Q1-Plus from RW Silicium. 1.1 parts by weight of silica fume Q1-Plus and 3.4 parts by weight of Steinex 48 / 50 were mixed with 100 parts by weight of quartz sand and formed into the shape of the core in a core box. Subsequently, the cores were supplied with hot CO2 at 100° C. for 60 seconds using a supply pressure of 150 kPa (1.5 bar) in a laboratory core shooter from Morek, thereby solidifying the cores.

[0265] 1. Screening tests to identify suitable additives

[0266] 6 kg of quartz sand (H32 from Quarzwerke) was mixed with 120 ml of water in a mixer (LM-2e roller mixer from Morek MULTISERW) at 40 rpm for 2 minutes. Subsequently, 0.48 kg of bentonite (Natroben 25F, Clariant) and 0.30 kg of additive (dry weight) were added and mixed at 40 rpm for 7 minutes. The resulting mixture was manually sieved through a 3 mm mesh sieve, and the material's compactibility (VDK) was determined (test equipment model: PVG; ID No. 1501, year of manufacture: 2000). If the VDK was greater than 46.0%, the mixture was sieved again and the VDK measurement was repeated. This process was repeated until the VDK was below 46.0%. If the VDK was less than 44.0%, 7-12 ml of water was added and mixed for an additional minute, followed by repeated sieving and VDK measurement. The addition of water was repeated until the VDK exceeded 44.0%.

[0267] Three different mixtures containing bright carbon formers according to the prior art were used as references for the properties of the molding materials:

[0268] 1) A commercial premix consisting of 25% of a bright carbon former ("sea coal") and 75% of sodium bentonite (NEMIR 2575) from HA Italia SpA

[0269] 2) 5 parts by weight of coke powder (metallurgical coke) from LuxCarbon GmbH as a bright carbon former, and 8 parts by weight of bentonite (Natroben 25F, Clariant)

[0270] 3) 5 parts by weight of Carboluxon 100 / P from Hüttenes-Albertus France as a commercially available bright carbon former, and 8 parts by weight of bentonite (Natroben 25F, Clariant).

[0271] In addition to the molding material's properties, casting quality is also a crucial criterion for selecting suitable additives. To test the casting quality, casting was performed using the sleeve mold apparatus described in (https: / / www.researchdisclosure.com / database / RD705032). This involves casting molds manufactured using the sleeve mold apparatus described in (https: / / www.researchdisclosure.com / database / RD705032). The castings were subsequently shot peened, and the surface roughness was measured according to DIN EN ISO 4287 (R_ISO). Two castings were studied, with the surface measured three times using a Mitutoyo SJ-500P surface measuring instrument at a measuring distance of 8 mm each, with small, medium, and large spacings between the fins arranged in a star shape. Since no consistent trends could be observed regarding the fin spacing and surface roughness, the average value of all measurements was used to simplify the evaluation. This confirmed that the surface roughness of all the resulting castings was within the commercially acceptable range.

[0272] 1.1 Different types of aluminum hydroxide and magnesium hydroxide as additives

[0273] SH500 type (SH500 nuance-00, Alteo) and SH950 type (SH950 nuance-00, Alteo) Al(OH)3 were used for the study of aluminum hydroxide.

[0274] Type 1 brucite (Brucit), type 2 brucite and type 3 brucite of Ziegler & Co. GmbH were used for the study of magnesium hydroxide (Table 4, all values are from the technical data sheet of Ziegler in October 2020).

[0275] Table 4: Parameters of brucite types used as additives

[0276]

[0277] Table 5 shows the molding material properties and roughness of the castings when using different hydroxides and the bright carbon formers 1) to 3) used as references. Dry compressive strength (TDF) <35 N / cm 2A moisture content of <2.8% is considered particularly advantageous, while a dry compressive strength (TDF) of >50 N / cm 2 A water content of >3.2% is considered unfavorable. Hydroxides, especially aluminum hydroxide Al(OH) 3 and magnesium hydroxide Mg(OH) 2 , enable the production of molds and exhibit good molding material properties (see Table 5).

[0278] Table 5: Molded material properties and roughness of castings when using different hydroxides or bright carbon formers as additives

[0279]

[0280] 1.2 Study on Aluminum Hydroxide Al(OH)3 as an Additive with Bright Carbon Forming Agent

[0281] The good values of hydroxides, especially aluminum hydroxide Al(OH)3, can be further improved by adding bright carbon formers such as Carboluxon 100 / P, see Table 6. The surface roughness of the castings is reduced in particular by using Carboluxon 100 / P, but the values obtained when using pure aluminum hydroxide are sufficient.

[0282] Table 6: Molded material properties and roughness of castings using aluminum hydroxide Al(OH)3SH 950 with the addition of the bright carbon former Carboluxon 100 / P as an additive

[0283]

[0284] 1.3 Study of different carbonates as comparative additives

[0285] While sufficiently good molding material values could not be achieved with Huntit (commercial name UltraCarb D98, available from LKAB Minerals), dolomite and manganese carbonate (commercially available from TROPAG GmbH) exhibited quite acceptable molding material values (Table 7).

[0286] Bianco Zandobbio 0 / 50 micron from Ziegler and PE-DOL 90 from Possehl Erzkontor were used as dolomite. Overall, the molding material values were slightly inferior to those obtained when using the aforementioned hydroxides. However, these values still allow the materials to be used as alternatives to conventional bright carbon formers. However, carbonates have the disadvantage of containing carbon.

[0287] Table 7: Properties of the molded materials when using different carbonates or bright carbon formers as additives

[0288]

[0289] The molding material properties can be improved by mixing carbonates with hydroxides (Table 8). MixMag is a 50% / 50% mixture of brucite (93% Mg(OH)2) and raw magnesite (92% MgCO3) 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), also purchased from Possehl Erzkontor.

[0290] Table 8: Molded material properties and roughness of castings when using different carbonate-hydroxide mixtures

[0291]

[0292] If a bright carbon former according to the prior art, such as Carboluxon 100 / P, is additionally added to the mixture of hydroxide and carbonate, the molding material values can be further improved (Table 9).

[0293] Table 9: Properties of molded materials using different carbonate-hydroxide mixtures with addition of Carboluxon 100 / P as bright carbon former

[0294]

[0295]

[0296] 1.4 Emissions of used bentonite and used additives

[0297] Table 10 shows the emission measurements of the bentonite used and the additives used. The emission measurements were carried out at the Foundry Institute of the University of Freiberg; for this purpose, the material was introduced into a tube furnace at 900° C. and the resulting emissions were measured by means of online FT-IR; calibration was carried out via test gas.

[0298] The emissions of the additives used according to the present invention are significantly lower than those of conventional bright carbon formers, such as the coke powder from LuxCarbon described above or the product Carboluxon 100 / P. While carbonates (not according to the present invention), such as manganese carbonate, reduce hydrocarbon emissions, especially benzene, toluene, and xylene, they are expected to significantly increase CO emissions compared to hydroxides, such as Al(OH)3. Therefore, according to the present invention, it is preferred to use carbonates in combination with hydroxides.

[0299] Table 10: Results of emission measurements using different additives (all data in mg / kg, ie mg of relevant emissions per kg of material)

[0300]

[0301]

[0302] 2. Manufacturing and testing of in-cycle molding materials

[0303] The purpose of the experiment was to cast a specific amount of molding material multiple times and regenerate it. As is common in industrial casting, the molding material was routed in a loop. An additive was added each time the molding material was regenerated, and this additive accumulated with each cycle. The components present in the starting molding material that were not added were reduced, meaning that the proportion of components not added in subsequent cycles decreased. The total amount of molding material in the cycle was constant at approximately 8 kg. Two molds were produced and cast per cycle using a sleeve mold system as described in (https: / / www.researchdisclosure.com / database / RD705032).

[0304] For instructions on how to perform the test, see Figure 2 Molding material circulation in.

[0305] The cycle of molding material circulation includes the following steps:

[0306] Making molding material (step (1), first cycle)

[0307] Test series 2.1, 2.2.1, 2.2.2, 2.3.1, 2.3.2 are as follows

[0308] In the first cycle, 6 kg of quartz sand of type H32 from Quarzwerke were used. The molding substrate was then mixed with 480 g of sodium bentonite (Natroben 25F, HAITALIA SpA, produced by activating natural calcium bentonite) and 300 g of the corresponding additives and 120 ml of water on a Morek Multiserw wheel mixer for 1 minute without water and then, after adding the water, mixed again for 7 minutes. To this end, the molding substrate was first mixed with 120 ml of water on a Morek Multiserw wheel mixer for 1 minute and then, after adding 480 g of sodium bentonite (Natroben 25F, HAITALIA SpA) and 300 g of the corresponding additives, mixed again on a Morek Multiserw wheel mixer for 7 minutes.

[0309] Test series 2.4-2.6 are as follows

[0310] In the first cycle, 3.7 kg of H32 quartz sand from Quarzwerke were used. Subsequently, the molded substrate was mixed with 322 g of Volclay (foundry bentonite GEKO from Clariant GmbH, Germany). TM V, which is naturally occurring sodium bentonite) and 207 g of the corresponding additives and 130 ml of water were mixed dry on a Morek Multiserw wheel mixer for 1 minute and then, after adding water, mixed again for 7 minutes. For this purpose, the molding substrate was first mixed with 130 ml of water on a Morek Multiserw wheel mixer for 1 minute and then, after adding 322 g of Volclay and 207 g of the corresponding additives, mixed again on a Morek Multiserw wheel mixer for 7 minutes.

[0311] The other embodiments apply to all test series 2.1 to 2.6 (unless otherwise stated).

[0312] The additive is fed each time the molding material is produced (step (1)) and accumulates with each cycle. By removing a portion of the cast molding material in step (5) or in step (1) of the next cycle (see Figure 2 ), the proportion of components present in the starting molding material and no longer added will be reduced.

[0313] Make the mold (step (2) in all cycles)

[0314] To this end, the molding material was filled into the mold of a sleeve mold apparatus after 3 minutes of mixing and compacted in two pressing steps (filling, pressing, refilling, pressing). This process was completed within a further 3 minutes. Two molds were produced for each test.

[0315] Casting (step (3) in all cycles)

[0316] After a 30-minute waiting period, the molds were poured in succession. Using a ladle, the molds were filled with liquid metal of alloy GJL 250 at 1450°C. The poured molds were left overnight until separation. The casting cooled, while the molded material was first heated and then cooled in the mold overnight.

[0317] Separation (step (4) in all cycles)

[0318] The casting is separated from the cast molding material.

[0319] Regeneration (step (5) in all cycles)

[0320] The molding material is filled into a storage container and the molding material blocks are crushed. The metal residues are removed.

[0321] Making molding material (step (1) in cycle 2 and each subsequent cycle)

[0322] New molding material is produced by refurbishing the recycled molding material from the previous cycle (recycled first molding material) by adding bentonite, water, additives (as defined above) and a new molding base material (new sand) or a recycled second molding material produced by regenerating cores (details see below).

[0323] New molding base material or a second molding material produced by recycling the cores (see below for details) was added to the recycled molding material from the previous cycle and mixed with 120 ml of water for 1 minute, and then sodium bentonite (Natroben 25F, HAITALIA SpA, test series 2.1, 2.2.1, 2.2.2, 2.3.1, 2.3.2) or Volclay (foundry bentonite GEKO from Clariant GmbH, Germany) was added. TM V, test series 2.4, 2.5 and 2.6) and the corresponding additives (for information on the amounts of bentonite and additives see below) and mixed again on a Morek Multiserw roller mixer for 7 minutes.

[0324] The increase in the amount of molding material caused by addition in the mixer, ie the increase in the amount of molding material caused by addition as defined above, is regulated in that the same amount of fully mixed molding material is removed in each cycle.

[0325] Each time the molding material is produced (step (1)), additives are added, which accumulate with each cycle. By removing a portion of the cast molding material, the proportion of components present in the starting molding material and no longer added in subsequent cycles is reduced.

[0326] 2.1 Additives Al(OH)3 or Mg(OH)2 when adding new molding substrate in subsequent cycles

[0327] Use in ( https: / / www.researchdisclosure.com / database / RD705032 ) were run for 10 cycles (0-9), wherein in the first test a 100% new H32 molding substrate from Quarzwerke was used.

[0328] In all subsequent cycles 1 to 9, 4 kg of used molding material from the previous casting was used and regenerated by 400 g of molding substrate (new molding substrate) as well as 64 g of bentonite and 20 g of the corresponding additives.

[0329] Alteo's SH950 nuance-00 was used as the additive aluminum hydroxide Al(OH) 3 . The test results using Al(OH) 3 are shown in Table 11.

[0330] Magnesium hydroxide Mg(OH) 2 was used as the additive, brucite type 3 from Ziegler & Co. GmbH. The test results using Mg(OH) 2 are shown in Table 12.

[0331] When using new molding base materials as additives (see Figure 2 , step (1)), both additives showed good molding properties and comparable surface quality, which can be seen from the measured roughness of the castings.

[0332] The addition of Al(OH)3 results in a higher active clay content and significantly lower ignition losses. Both Al(OH)3 and Mg(OH)2 exhibit good mold base properties and casting quality. The surface roughness of the castings is correspondingly low.

[0333] Table 11: Characteristic values of samples taken in the corresponding cycles to determine the properties of the molding material with Al(OH)3 as additive, and the surface roughness of the castings

[0334]

[0335] Table 12: Characteristic values of samples taken in the corresponding cycles to determine the properties of the molding material with Mg(OH)2 as additive, and the surface roughness of the castings

[0336]

[0337]

[0338] 2.2 Al(OH)3 and Mg(OH)2 when adding cold box sand in subsequent cycles (not according to the invention)

[0339] 31 cycles (0-30) were performed using the sleeve mold apparatus described in (https: / / www.researchdisclosure.com / database / RD705032). The experiments were performed and the molding material properties and casting properties were measured as described in Chapter 2.1, but in the subsequent cycles, instead of new molding base material, a second recycled molding material produced by recycling uncast cores was added (see Figure 2 , step (1)) (see Table 13 or 16 for the quantitative proportion of the produced molding material), the core is produced by a cold box binder ("cold box core sand").

[0340] 2.2.1 Aluminum hydroxide Al(OH)3 when adding cold box core sand in subsequent cycles

[0341] In the case of using aluminum hydroxide Al(OH)3, the molding material properties showed stability when adding 5% cold box core sand, so that the addition of cold box core sand was increased to 10% from cycle 15 (Tables 13 and 14). In addition, the molding material properties remained stable.

[0342] Table 13: Composition and compaction of the molding material mixture in each cycle

[0343]

[0344]

[0345] Table 14: Characteristic values of samples taken in the corresponding cycles

[0346]

[0347]

[0348] The data from the CNS analysis of the molding materials during the different cycles showed an increase in the carbon and nitrogen content from the addition of cold box core sand. Compared to the test series in which new sand (see 2.1 above) was added instead of cold box core sand, the surface roughness of the castings improved, which is due to the addition of core sand (Table 15).

[0349] Table 15: CNS analysis of selected cycles and corresponding casting surface roughness

[0350]

[0351]

[0352] (1) The abbreviation NG means that the measured value is below the detection limit.

[0353] 2.2.2 Mg(OH)2 when adding cold box core sand in subsequent cycles

[0354] Even after several cycles, the properties of the molding material could not be stably maintained using magnesium hydroxide Mg(OH)2 in the form of Type 3 brucite as an additive. Therefore, the bentonite content of the molding material was increased in cycles 8 and 14 (Table 16). Despite this, no stabilization of the molding material's characteristic values was achieved (Table 17). In particular, the wet tensile strength decreased with increasing cycle number, and this trend could only be temporarily counteracted by adding further bentonite.

[0355] Table 16: Composition and compaction of the molding material mixture in each cycle

[0356]

[0357]

[0358] Table 17: Characteristic values of samples taken in the corresponding cycles

[0359]

[0360] As expected, the carbon content of the molding material increased with the addition of cold-box core sand, and the nitrogen content also increased to a limited extent (Table 18). The surface roughness of the castings was good and not negatively affected. However, unlike aluminum hydroxide Al(OH)3 (see Test Series 2.2.1 above), magnesium hydroxide Mg(OH)2 was unable to achieve a molding material cycle with stable molding material properties with the addition of organic core sand (i.e., cold-box core sand, see above) (Table 17).

[0361] Table 18: CNS analysis of selected cycles and the corresponding casting surface roughness

[0362]

[0363] (1) The abbreviation NG means that the measured value is below the detection limit.

[0364] 2.3 Al(OH)3 and Mg(OH)2 when adding inorganically bonded core sand in subsequent cycles (not according to the invention)

[0365] 31 cycles (0-30) were performed using the sleeve mold apparatus described in (https: / / www.researchdisclosure.com / database / RD705032). The tests and the measurement of the molding material properties and the casting properties were performed as described in Chapter 2.1, but in the subsequent cycles, instead of the new molding base material, a recycled second molding material produced by recycling the uncast core was added (see Figure 2 , step (1)) (for the quantitative proportions of the produced molding materials, see Tables 19 or 22), the core is produced ("IOB core sand") using an inorganic binder (water glass). This is therefore an inorganic molding material cycle with respect to all the binders used.

[0366] 2.3.1 Aluminum hydroxide Al(OH)3 when inorganically bonded core sand is added in subsequent cycles

[0367] Even with the addition of IOB core sand, molding material cycles with stable molding material properties were obtained when using aluminum hydroxide Al(OH) 3 , so that the addition of IOB core sand was increased to 10% from the 15th cycle (Tables 19 and 20).

[0368] Table 19: Composition and compaction of the molding material mixture in each cycle

[0369]

[0370]

[0371] Table 20: Characteristic values of samples taken in the corresponding cycles

[0372]

[0373]

[0374] Analysis of the molded material (Table 21) shows no significant accumulation of carbon, nitrogen, or sulfur in the molded material, with C-containing (carbon-containing) components from inorganic binders (e.g., surfactants) being of minor importance. The low C loading (carbon load) is one of the major advantages of recycling the inorganic molded material, as extremely low emissions can be expected (see below). Despite the low carbon content, the surface roughness achieved (Table 21) is still very close to that of the tests with the addition of cold box core sand (Test Series 2.2.1).

[0375] Table 21: CNS analysis of selected cycles and the corresponding casting surface roughness

[0376]

[0377] (1) The abbreviation NG means that the measured value is below the detection limit.

[0378] 2.3.2 Magnesium hydroxide Mg(OH)2 when inorganically bonded core sand is added in subsequent cycles

[0379] Even after several cycles, the properties of the molding material could not be stably maintained using magnesium hydroxide Mg(OH)2 in the form of Type 3 brucite as an additive. Therefore, the bentonite content of the molding material was increased in cycles 8 and 15 (Table 22). Despite this, the characteristic values of the molding material did not stabilize. In particular, the wet tensile strength decreased with increasing cycles, and this trend could only be temporarily counteracted by adding further bentonite (Table 23).

[0380] This means that, similar to the addition of cold-box core sand (Test Series 2.2.2), even with the addition of Mg(OH)2, a molding material cycle with stable molding material properties was not achieved. The water requirement of the mixture increased significantly, and other molding material characteristics also showed instabilities (Table 23). The molding material water requirement corresponds to the water content of the molding material mixture in the specified form (target compaction). The active clay content and the wet tensile strength decreased significantly with increasing cycle number. This could be compensated by adding bentonite, but overall, a molding material cycle with stable molding material properties was not achieved.

[0381] Table 22: Composition and compaction of the molding material mixture in each cycle

[0382]

[0383] Table 23: Characteristic values of samples taken in the corresponding cycles

[0384]

[0385]

[0386] Analysis of selected samples of the molding material (Table 24) shows that for high cycle numbers, the carbon content increases slightly, which is probably caused by the addition of bentonite; the Ca bentonite is treated with carbonate during activation. The surface roughness of the castings is always acceptable, i.e. good to excellent.

[0387] Table 24: CNS analysis of selected cycles and corresponding casting surface roughness

[0388]

[0389] (1) The abbreviation NG means that the measured value is below the detection limit.

[0390] 2.4 Additive Al(OH)3 when adding new molding substrate in subsequent cycles

[0391] In use in ( https: / / www.researchdisclosure.com / database / RD705032 ), 11 cycles (0-10) were carried out using the sleeve mold apparatus described in ), wherein in the first test a 100% new H32 molding substrate from Quarzwerke was used.

[0392] In all subsequent cycles 1 to 10, 3.7 kg of used molding material from the previous casting was used and refurbished with 185 g of molding base material (new molding base material), 26 g of bentonite, and 23 g of the corresponding additives (Table 25). Alteo's SH950 nuance-00 was used as the additive, aluminum hydroxide Al(OH) 3. Stable molding material properties were achieved (Table 26).

[0393] When using new molding base materials as additives (see Figure 2 In the case of step (1), good molding properties and good to excellent surface quality are achieved, as can be seen from the measured roughness of the castings. As expected, CNS analysis gave insignificant carbon and nitrogen contents after 11 cycles, since only inorganic materials were used (see Table 27).

[0394] Table 25: Composition and compaction of the molding material mixture in each cycle

[0395]

[0396] Table 26: Characteristic values of samples taken in the corresponding cycles

[0397]

[0398]

[0399] Table 27: CNS analysis of selected cycles and the corresponding casting surface roughness

[0400]

[0401] (1) The abbreviation NG means that the measured value is below the detection limit.

[0402] 2.5 Al(OH)3 when adding cold box sand in subsequent cycles (not according to the invention)

[0403] 11 cycles (0-10) were performed using the sleeve mold apparatus described in (https: / / www.researchdisclosure.com / database / RD705032). The tests and the measurement of the molding material properties and casting properties were performed as described in Chapter 2.4, but in the subsequent cycles, instead of a new molding base material, a recycled second molding material produced by recycling an uncast core was added (see Figure 2 , step (1)) (for the quantitative proportions of the produced molding materials, see Table 28), the cores were produced with the aid of a cold box binder ("cold box core sand"). Stable molding material properties were achieved (Table 29).

[0404] Table 28: Composition and compaction of the molding material mixture in each cycle

[0405]

[0406] Table 29: Characteristic values of samples taken in the corresponding cycles

[0407]

[0408]

[0409] The data from the CNS analysis of the molding material after 11 cycles show that the carbon and nitrogen contributions from the cold box core sand addition are significant, especially compared to the test series with new sand addition (Table 30).

[0410] Table 30: CNS analysis of selected cycles and the corresponding casting surface roughness

[0411]

[0412] (1) The abbreviation NG means that the measured value is below the detection limit.

[0413] 2.6 Al(OH)3 when inorganically bonded core sand is added in a subsequent cycle (not according to the invention)

[0414] 11 cycles (0-10) were performed using the sleeve mold apparatus described in (https: / / www.researchdisclosure.com / database / RD705032). The tests and the measurement of the molding material properties and casting properties were performed as described in Chapter 2.4, but in the subsequent cycles, instead of a new molding base material, a recycled second molding material produced by recycling an uncast core was added (see Figure 2 , step (1)) (for the quantitative proportions of the produced molding material, see Table 31), the cores were produced ("IOB core sand") using an inorganic binder (water glass). This therefore represents an inorganic molding material cycle with respect to all the binders used. Stable molding material properties were achieved (Table 32).

[0415] Table 31: Composition and compaction of the molding material mixture in each cycle

[0416]

[0417] Table 32: Characteristic values of samples taken in the corresponding cycles

[0418]

[0419] Analysis of the molding material (Table 33) shows that carbon, nitrogen, or sulfur do not accumulate significantly in the molding material; C-containing (carbon-containing) components from inorganic binders (e.g., surfactants) are of minor importance. The low C (carbon) loading is one of the major advantages of recycling the inorganic molding material, as only very low emissions are expected (see below). Despite the lower carbon content, the surface roughness achieved (Table 33) is comparable to that of tests with cold box core sand (Test Series 2.5).

[0420] Table 33: CNS analysis of selected cycles and surface roughness of the corresponding castings

[0421]

[0422] (1) The abbreviation NG means that the measured value is below the detection limit.

[0423] 3. Molding material cycle with gradually decreasing carbon content in the molding material

[0424] The purpose of this experiment was to repeatedly cast and regenerate a specific amount of recycled molding material, particularly as the carbon content in the molding material gradually decreased. As is common in industrial casting, the molding material was circulated. Additives were introduced during each recycling of the molding material, which accumulated with each cycle. The components present in the starting molding material that were not added were reduced, meaning that the proportion of components not added in subsequent cycles decreased. The total amount of molding material was constant at approximately 1,200 kg. Four molds were produced and cast per cycle using a finned mold system as described in (http: / / www.reschdeotsue.com / DataBase / RD705032).

[0425] For illustration of the test execution, refer to Figure 4 Molding material circulation in.

[0426] The cycle of molding material circulation includes the following steps:

[0427] Making molding material (step (1), first cycle)

[0428] In the first cycle, recycled molding material (starting molding material) from the molding material cycle of the brake disc foundry is used. (See point 0.2 above)

[0429] The recycled molding material is conveyed from the big bags to a silo in front of an Eirich mixer (Eirich intensive mixer R09 with a capacity of 150 liters and a maximum capacity of 240 kg, operated in batch mode at atmospheric pressure) using a BigBag unloading station and two conveyor belts. The previously weighed additives (additives), bentonite, base or core molding material, and additives are placed on the silo discharge belt. SH950 Al(OH)3 (SH950 nunce-00, Alteo) is used as the additive.

[0430] In each manufacturing (step (1), see Figure 4 ) is added to the molding material, said additive accumulating with each cycle. By removing a portion of the cast molding material in step (5) or in step (1) of the next cycle (see Figure 4 ), the proportion of components present in the starting molding material and no longer added is reduced.

[0431] The molding material is removed from the silo and transported to the mixer along with the additives. The mixing process begins, water is automatically metered, and after the mixing process is complete, the finished molding material is emptied from the mixer into a transport container. The transport container is then transported to the molding facility.

[0432] The mixer program was selected as appropriate (depending on the water content of the mixture) between a mixing process without intermediate stops (Table 35) and a mixing process with intermediate stops (Table 34), and the desired compaction rate was set to 40% + / - 5% by controlling the water content. The desired compaction rate was set by controlling the degree of compaction. The degree of compaction varied with the water content of the molding material. The water content of each mixture was determined. Since the amount of water required to achieve the target degree of compaction was not known, intermediate stops in the mixing process made it easier to determine the required amount of water and to produce the subsequent mixture without intermediate stops.

[0433] Table 34: Mixing process with intermediate pauses

[0434]

[0435]

[0436] Table 35: Mixing process without intermediate stops

[0437]

[0438] Make the mold (step (2) in all cycles)

[0439] To do this, first fill part of the volume of the lower box of the mold with a layer of sieved molding material from the transport container. So much molding material is sieved that the outline of the fin pattern is no longer visible (this corresponds to a height of 80 mm in the lower box and 50 mm 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.

[0440] The lower box (i.e., the molding material in the lower box) was compacted using the Seiatsu air flow molding method in an HWS HSP-1D molding machine with the given parameters (Table 36, mold box dimensions: 700 × 500 × 200 / 200 mm, pattern plate dimensions: 650 × 450 × 30 mm). The time during which air flow is directed through the molding material in the mold box to fluidize it is called the Seiatsu time. The Seiatsu time can be set independently for the upper and lower boxes. The molding material is then pressed.

[0441] Table 36: Compaction parameters

[0442]

[0443]

[0444] The lower box is removed flat by hand and transported to the closing station (Zulegestion) by means of a crane. The upper box is filled, compacted, removed and transported in the same way. The previously produced (step (1a), see Figure 4 ) The core is placed in the lower box (step (2a), see Figure 4 ). The mold is closed, clamped and transported to the casting station.

[0445] Casting (step (3) in all cycles)

[0446] The mold was poured with liquid metal of alloy GJL 250 at 1450° C. using a casting ladle in carrier iron with a one-sided shear.

[0447] The next batch of moulds is manufactured (steps (2), (2a)) and cast.

[0448] The cast mold was left to stand for 4 hours until separation, during which the casting cooled and the molding material heated up.

[0449] Separation (step (4) in all cycles)

[0450] The upper and lower boxes are opened. The castings and the cast molding material are separated. The core sand is handled differently in the three molding material cycles studied:

[0451] 1. In test series A, in which fresh sand was used as the metered molding base, cores bonded with CO 2 -hardened water glass (see point 0.2 above) were used, which did not decompose during separation and were completely removed at this point in the cycle.

[0452] 2. In test series B, which used a cold box core, the core completely disintegrated in the center and could no longer be separated from the molding material. The core head did not disintegrate and could not be easily crushed. Therefore, the core head was removed at this point in the cycle.

[0453] 3. In test series C, which used an inorganically bonded core (binder Cordis 9477 / Anorgit 9476, see point 0.2), the core disintegrated only in the edge layer but could not be crushed very easily by hand. Therefore, the IOB core sand was not removed.

[0454] Regeneration (step (5) in all cycles)

[0455] Spread the molding material on the floor and crush any lumps with a shovel. Remove any metal residue. Let the molding material sit on the floor for at least three hours to cool. After cooling, fill the large bags with a shovel.

[0456] Making molding material (step (1) in cycle 2 and each subsequent cycle)

[0457] New molding material was produced by refurbishing the recycled molding material from the previous cycle (recycled first molding material) by adding bentonite, water, additives (as defined above) and a new molding base material (new sand, test series A) or a recycled second molding material produced by recycling the core (test series B and C, see below for details). The sequence of the mixing process is described above for step (1) of the first cycle.

[0458] The increase in the amount of molding material caused by addition in the mixer, ie the increase in the amount of molding material caused by addition as defined above, is regulated in that the same amount of fully mixed molding material is removed in each cycle.

[0459] During each production (step (1)) of the molding material, additives are added, which accumulate with each cycle. By removing a portion of the cast molding material, the proportion of components present in the starting molding material and no longer added in subsequent cycles is reduced.

[0460] 3.1 Test series in which new molding substrate (new sand) was added in step (1) (Test series A)

[0461] When producing the mold (see step (2) above), a water glass-bonded core is used, which does not decompose after casting (see point 0.2 above) and is removed in step (4) as described above.

[0462] In a test series with 30 cycles (A1-A30, see Table 37), the recycled molding material from the previous cycle (recycled first molding material) was refurbished in each subsequent cycle using a molding base material of the Grudzen Laz. 0.20 / 0.315 / 0.40 type (coarse quartz sand grade 1K) from Quarzwerke.

[0463] Table 37: Composition and compaction of the molding material mixture in each cycle

[0464]

[0465]

[0466] (1) “Regenerated first molding material” here means the amount of molding material from the respectively preceding cycle which is used again after the regeneration,

[0467] (2) Add water

[0468] (3) Measured water content of the mixture

[0469] Table 38: Characteristic values of the samples taken in the corresponding cycles to determine the properties of the molding material

[0470]

[0471]

[0472] Table 39: Analysis of samples from various cycles

[0473]

[0474]

[0475] As expected, a gradual decrease in the ignition loss of the samples can be observed, as less organic material is present in the molded material with increasing cycle number. This is also reflected in the gradual reduction in the carbon, nitrogen, and sulfur contents (Table 39). The molded material properties remain essentially unchanged (Table 38).

[0476] Despite the reduction in the carbon content, no casting defects were observed, and the surface roughness of the castings did not change significantly due to the reduction in the carbon content (Table 40).

[0477] Table 40: Surface roughness of castings produced during test series A

[0478]

[0479] 3.2 Test series with added organic binder core sand (Test series B, not according to the invention) )

[0480] During the production of the mold (see step (2) above), a cold box core is inserted (see point 0.2 above), which is completely disintegrated in the center and can no longer be separated from the molding material.

[0481] In the test series with 30 cycles (B1-B30, see Table 41), based on the above-mentioned recycled starting molding material from the brake disc foundry, a recycled second molding material produced by recycled cores (see Figure 4 ), the core is made by means of a cold box binder; i.e., in each subsequent cycle, the recycled molding material (recycled first molding material) from the previous cycle is refurbished by means of a recycled second molding material produced by regenerating the core made by means of a cold box binder.

[0482] Table 41: Composition and compaction of the molding material mixture in each cycle

[0483]

[0484] (1) “Regenerated first molding material” here means the amount of molding material from the respectively preceding cycle which is used again after regeneration,

[0485] (2) Add water

[0486] (3) Measured water content of the mixture

[0487] Table 42: Characteristic values for determining the properties of the molding material of the samples taken in the corresponding cycles

[0488]

[0489]

[0490] Table 43: Analysis of molded material samples from selected cycles

[0491]

[0492] The molded material analysis (Table 43) shows that the ignition loss of the molded material decreases with the number of cycles. At the same time, the carbon (C), sulfur, and nitrogen (N) contents decrease, with the C and N contents approaching the limit values determined by adding cold-box bonded core sand. The molded material properties remain essentially unchanged (Table 42).

[0493] In this test series, the surface roughness of the castings was also determined (Table 44). It was observed that despite the reduced carbon content in the molding material, a good surface was obtained. No casting defects were observed.

[0494] Table 44: Surface roughness of castings produced during experimental series B

[0495]

[0496] 3.3 Test series with addition of inorganic binder core sand (test series C, not according to the invention)

[0497] When producing the mold (see step (2) above), an inorganic binder core is used (binder Cordis 9477 / Anorgit 9476, see point 0.2 above), which only decomposes in the edge layer but cannot be crushed very easily by hand.

[0498] In the test series with 30 cycles (C1-C30, see Table 45), the recycled second molding material produced by recycled cores (see Figure 4 ), the core being manufactured with the aid of a water glass binder (Anorgit / Cordis system); i.e., in each subsequent cycle, the recycled molding material (recycled first molding material) from the previous cycle is refurbished with the aid of a recycled second molding material which is manufactured by recycling the core manufactured with the aid of a water glass binder (Anorgit / Cordis system).

[0499] Table 45: Composition and compaction of the molding material mixture in each cycle

[0500]

[0501]

[0502] (1) "Regenerated first molding material" here means the amount of molding material from the respective previous cycle that is used again after regeneration

[0503] (2) Add water

[0504] (3) Measured water content of the mixture

[0505] Table 46: Characteristic values of the samples taken in the corresponding cycles to determine the properties of the molding material

[0506]

[0507]

[0508] Table 47: Analysis of samples from selected cycles

[0509]

[0510] The tests clearly show that the ignition loss and the carbon, nitrogen and sulfur contents gradually decrease with increasing changes in the molding material (Table 47). The molding material properties remain essentially unchanged (Table 46).

[0511] Despite the reduction in the carbon content, no casting defects were observed, and the surface roughness of the castings did not change due to the reduction in the carbon content (Table 48).

[0512] Table 48: Surface roughness of castings produced during the test series

[0513]

[0514] 3.4 Landfill levels of recycled molding materials

[0515] From all three test series, the regenerated molding material was investigated after the 30th cycle (A-30, B-30, or C-30), and the values obtained were compared with those of the starting molding material (Table 49, the abbreviation NG indicates that the measured value was below the detection limit). The following was determined:

[0516] According to the German Landfill and Long-Term Storage Ordinance (Landfill Ordinance) of July 4, 2020, the recycled starting molding material (starting sand) is assigned to landfill category II due to its ignition loss, TOC value (Total Organic Carbon), and phenol coefficient. The recycled molding material from test series B had only slightly too high a TOC value for classification into landfill category I and should therefore be assigned to landfill category II, although the TOC value could be further reduced due to the progress of replacement or the use of a different cold box adhesive.

[0517] The recycled material in test series A and C was classified as landfill class I.

[0518] Table 49 (The abbreviation NG indicates that the measured value is below the detection limit)

[0519]

[0520]

[0521] 1. Determined according to DIN EN 14346:2007-03

[0522] 2. Determined according to DIN EN 15169:2007-05

[0523] 3. Determined according to DIN EN 15936:2012-11 (AN, L8: Version A; FG, F5: Version B)

[0524] 4. According to the National Waste Task Force ( Abfall) Notice No. 35, abbreviated as: KW / 04:2019-09 confirmed

[0525] 5. Determined according to DIN EN ISO 10523(C5):2012-04

[0526] 6. Determined according to DIN EN 15216:2008-01

[0527] 7. Determined according to DIN EN ISO 10304-1(D20):2009-07(D20)

[0528] 8. Determined according to DIN EN ISO 14403-2:2012-10

[0529] 9. Determined according to DIN EN ISO 17294-2(E29):2017-01(E29)

[0530] 10. Determined according to DIN EN ISO 12846 (E12): 2012-08

[0531] 11. Determined according to DIN EN 1484:2019-04

[0532] 12. Determined according to DIN EN ISO 14402 (H37): 1999-12

[0533] 3.5 BTX emission potential of recycled molding materials

[0534] Starting molding materials from a regulated molding material cycle at a brake disc foundry, as well as molding materials from cycles A-30, B-30, and C-30, were investigated for their BTX emission potential. To this end, after drying at 105°C, the samples were ground cold in a planetary ball mill (Retsch Planetary Ball Mill PM100CM) at 300 rpm for 2 minutes (container: 150 ml stainless steel cup with stainless steel balls). Cooling at -20°C for at least 12 hours, i.e., the mortar of the planetary ball mill was stored at -20°C for at least 12 hours before use, was done to prevent overheating of the sample during the grinding process. Subsequently, 10 mg of sample was weighed into a pyrolysis tube. A duplicate determination was performed for each sample. The measurements were performed using the following instruments:

[0535] ·GERSTEL MPS

[0536] GERSTEL TDU 2 with pyrolysis module

[0537] Agilent 8890B gas chromatograph and Agilent 5977 mass spectrometer

[0538] RESTEK 13868RXI-624Sil MS capillary column, -60°C-300°C (320°C): 30m × 250μm × 1.4 0.25mm

[0539] 150ml stainless steel mortar and stainless steel grinding balls

[0540] Hamilton electronic retainer (VWR Part No. HAMIDS86200)

[0541] Hamilton 1 μL syringe (VWR Catalog No. 549-1224)

[0542] Carbotrap B-packaged Glass Inlet Liner (temperature limit 450°C) (Gerstel Part No. 013248-005-00)

[0543] Quartz pyrolysis tube (Gerstel product number 018437-020-00)

[0544] Adsorbent matrix Carbopack TM B, 60-80 mesh (VWR Product No. SUPL20273)

[0545] Silanized glass wool (VWR Part No. SERA22367.01)

[0546] The following conditions apply:

[0547] Gas chromatography (GC) parameters

[0548]

[0549]

[0550] KAS parameters

[0551] (KAS = Cold Feed System - i.e. the sample is pyrolyzed, the pyrolysis gases are condensed and then volatilized for GC measurement

[0552]

[0553] Calibration method:

[0554] MSD parameters (MSD = Mass Spectrometric Detector)

[0555]

[0556] TDU parameter (TDU = Thermal Desorption Unit)

[0557]

[0558] Pyrolysis parameters

[0559]

[0560]

[0561] Calibration was performed with standards based on benzene, toluene; m-xylene and p-xylene; styrene; o-xylene, ethylbenzene, and cumene.

[0562] Sample method:

[0563] MSD parameters

[0564]

[0565] TDU parameters

[0566]

[0567] Pyrolysis parameters

[0568]

[0569] Characteristic value of a method

[0570]

[0571]

[0572] The evaluation was performed with the aid of the MassHunter software.

[0573] The results shown in Table 50 clearly demonstrate that the use of the additive according to the invention can significantly reduce harmful emissions. Emission potential is particularly significantly reduced when inorganic cores are incorporated or when new molding substrate (fresh sand) is added to the molding material cycle. Significant effects are also observed when cold box core sand is added. In the model example, the emission potential is reduced by more than 45%.

[0574] Table 50: Pyrolysis (GC-MS) of the molded material after 30 cycles compared to the starting molded material (all indications are mg emissions / kg sample material)

[0575]

[0576] In Table 50, the description “<…” indicates that the content of the corresponding BTEX compound is below its detection limit.

[0577] For the value ranges in the row "BTEX at 900°C" the following applies:

[0578] The lower limit value corresponds to the sum of the contents of BTEX compounds above the corresponding detection limit, making it possible to determine the value (in the case of the starting molding material, this is benzene, toluene, styrene and m-xylene, p-xylene).

[0579] The upper limit value corresponds to the sum of the lower limit value and the detection limit for each BTEX compound whose content is below the corresponding detection limit (in the case of the starting molding material, this is o-xylene, styrene and cumene).

Claims

1. A method for guiding a molding material in a molding material circulation comprising two or more cycles, the method comprising the following steps: - casting in a mould comprising moulding material bound with smectite-containing clay during an earlier one of said two or more cycles of circulation of said moulding material, - regenerating the cast molding material so as to obtain a regenerated first molding material, - in a later cycle of said two or more cycles of said molding material circulation, producing a molding material comprising: (i) a recycled first molding material, as well as (ii) additives, comprising: - an additive containing at least one dehydratable inorganic compound that separates water at a temperature of 150° C. or higher, - One or more raw materials from the following groups: - a molded substrate, a recycled second molding material produced by recycling molding material from an uncast mold and / or core and / or parts thereof, a recycled third molding material produced by recycling molds and / or cores and / or parts thereof cast outside the molding material circulation, - and optionally, a smectite-containing clay, preferably bentonite, In this case, the total proportion of material from the mold and the core formed from the molding material bonded with a binder other than the smectite-containing clay in the produced molding material is less than 10% by weight.

2. The method according to claim 1 , wherein at least 90% by weight, preferably at least 99% by weight and particularly preferably 100% by weight of the recycled second molding material and the recycled third molding material come from molds and / or cores bonded with smectite-containing clay.

3. The method according to claim 1 or 2, wherein the smectite-containing clay is bentonite.

4. The method according to claim 1 , wherein at most 10% by weight, preferably at most 1% by weight and particularly preferably 0% by weight, of the second and third molding materials come from molds and / or cores produced with a binder other than smectite-containing clay. 5 . The method according to claim 1 , wherein during the casting process a cast molding material is obtained which contains no material from the cast core.

6. The method according to claim 1, wherein the casting is carried out in a mold without a core or in a mold with a core bonded with a smectite-containing clay.

7. The method according to any one of the preceding claims, wherein the additive contains one or both compounds from the group consisting of aluminum hydroxide and magnesium hydroxide.

8. A method according to any one of the preceding claims, wherein the moulding material produced in the later cycle has one or more of the following parameters: a carbon concentration of less than 1.5%, preferably less than 0.8%, based on the mass of the molding material, as determined by means of elemental analysis, a nitrogen concentration of less than 0.1%, preferably less than 0.05%, based on the mass of the molding material, as determined by means of elemental analysis, a sulfur concentration of less than 0.05%, preferably less than 0.03%, based on the mass of the molding material, as determined by means of elemental analysis, - a ignition loss of at most 5%, preferably at most 3.5%, determined in accordance with VDG Practice Specification P33 (April 1997).

9. The method according to claim 1, wherein the molding material removed during recycling meets the requirements of landfill class DKI according to Annex 3 of the Landfill and Long-term Storage Ordinance of April 27, 2009 (Landfill Ordinance - DepV).

10. The method according to any one of the preceding claims, wherein the mould is cast in iron.

11. Use of an additive as defined in claim 1 in a method according to any one of claims 1 to 10.

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