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

Abstract

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

Description

Technical Field

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

[0002] Clays for binding molding materials usually contain smectite. Examples of such smectite-containing clays are bentonites, especially sodium bentonite and calcium bentonite, which contain sodium or calcium in addition to the elements magnesium, aluminum, and silicon. Other smectite-containing clays are hectorite, soapstone, nontronite, beidellite, or zinc soapstone. Clays such as kaolinite or illite can be mixed with smectite-containing clays and used as clay binders.

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

[0004] Sodium bentonite can contain, for example, 70 to 95 wt% of montmorillonite, with quartz, opal, cristobalite, feldspar, biotite, clinoptilolite, calcite, gypsum, etc. as the remaining components.

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

[0006] In this document, the term "clay-bonded mold" is used, where appropriate, for a casting mold bonded by a smectite-containing clay. Here, it always refers to a casting mold bonded by a smectite-containing clay. Preferably, in the foundry industry, smectite-containing clays in the form of sodium bentonite or calcium bentonite and / or mixtures thereof are used, where the mixture is partially formed in situ by adding salts and the resulting ion exchange.

[0007] Considered as molding substrates are each of the following sands, which can be casting molds and can maintain their shape when in contact with hot metal at high temperatures. Typical sands are silica sand, olivine sand, chromite sand, zircon sand, and artificial ceramic sand, or mixtures of such sands. The mold usually contains at least 40% sand, preferably more than 50% sand, particularly preferably more than 60% sand, and very particularly preferably more than 70% sand.

[0008] In industrial practice, clay-bonded casting molds are usually made from a molding material that contains, in addition to a smectite-containing clay as a binder and a molding substrate, additives and water. Such a molding material is also referred to as "green sand" or "wet molding sand". Compaction of the molding material causes reinforcement, thus ensuring sufficient shape stability.

[0009] In industrial practice, molding materials with smectite-containing clay as a binder are generally used in the molding material cycle.

[0010] The molding material cycle in the context of the present disclosure means that the molding material is regenerated from the cast mold ("cast molding material", also known as used sand) and used to manufacture new molding material, and the cast mold is again manufactured from the new molding material. Thus, the molding substrate contained in the molding material is present at least in part as a component of the molding material regenerated from at least one already cast clay-bonded mold.

[0011] The molding material cycle in the context of the present disclosure consists of at least two temporally successive cycles. Thus, two (not necessarily directly successive) cycles of the molding material cycle can be divided into an earlier cycle and a later cycle. If the molding material cycle consists of only two cycles, then the first cycle in chronological order is the earlier cycle and the second cycle in chronological order is the later cycle.

[0012] The cycles of the molding material cycle can be described by the following characteristic steps (for the following step names, see Figure 1 ):

[0013] (Step 1) Manufacture of the molding material, i.e., manufacture of the molding material including the regenerated molding material from the earlier cycle and additives (see below),

[0014] (Step 2) Manufacture of the mold, i.e., a mold bonded by smectite-containing clay made from the molding material manufactured in step (1),

[0015] (Step 3) Casting, i.e., manufacture of a casting by casting the mold manufactured in step (2), (Step 4) Separation, i.e., separation of the casting manufactured in step (3) from the mold, where the cast molding material is obtained, the molding material including the material from the cast mold,

[0016] (Step 5) Regeneration of the cast molding material, i.e., regeneration of the cast molding material in step (4) such that regenerated first molding material is obtained for use in manufacturing new molding material in step (1) of the later cycle.

[0017] In certain cases, it is preferred that one, more or all cycles of the molding material cycle include additional steps, and / or each of the steps has additional features. Details regarding this are derived from the following description, the appended claims and the drawings.

[0018] In each cycle of the above-mentioned molding material cycle, in step (3), a casting is produced by casting the mold produced in step (2). Here, when casting (step (3) of the cycle), the molding material undergoes significant changes on the material due to thermal stress and chemical stress. In order to implement the cycle of the molding material, the cast molding material must be regenerated.

[0019] In some cases, especially for producing castings with complex geometries, in step (3), a casting is produced by casting a mold produced in step (2) with one or more inserted cores (see Figure 3 ). Cores inserted into a clay-bonded mold are usually not clay-bonded. Such cores are usually made of an organic binder such as polyurethane or phenolic resin or an inorganic binder without clay such as a binder containing water glass. If, in step (4), the casting produced in step (3) is separated from the mold and the cores, then generally the cast molding material is obtained, which contains material from the cast cores (old core sand).

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

[0021] Regeneration generally includes crushing the cast molding material (particle separation) and removing as much as possible metal residues and other impurities such as impurities in the form of auxiliary products from the casting process (core heads, riser residues (Speiserreste), etc.).

[0022] Wear products are generated by thermal stress, mechanical stress, and possibly also chemical stress during casting, such as fines sand fraction, inert clay fraction, decomposition products of additives especially bright carbon formers, reaction products of core binders, and oolitic grains of the molding substrate.

[0023] In order not to enrich such wear products in the molding material cycle and / or not to have an adverse effect on the properties of the molding material, or in order not to sharply reduce the required active fraction of the binder (montmorillonite-containing clay) and additives, in the corresponding subsequent cycles, additives are added in step (1) when producing the molding material, that is, the regenerated molding material is repaired by the additives. In order to keep the quality of the molding material guided in the cycle constant, a corresponding amount of the molding material is removed from the molding material cycle. This can be done before the repair by the additives (i.e., in step (5)) or after the repair by the additives.

[0024] The additive usually includes clay containing montmorillonite, water, additives (see below), and one or more raw materials from the group consisting of the following components:

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

[0026] - Regenerated second molding material, which is manufactured by regenerating uncast molds and / or cores and / or parts thereof,

[0027] - Regenerated third molding material, which is manufactured by regenerating molds and / or cores and / or parts thereof that are manufactured and cast outside the observed molding material cycle.

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

[0029] The molds and cores used to obtain the regenerated second and third molding materials as defined above are not necessarily clay-bonded. In particular, cores are usually not clay-bonded, but are made of common organic binders such as polyurethanes, especially polyurethanes formed in cold box processes, or are made of phenolic resins in the form of novolac resins or phenolic varnishes, especially novolac resins used in hot box or warm box methods, and especially phenolic varnishes used in cloning methods or shielding molding methods.

[0030] In each cycle of the industrial molding material cycle, the quality of the castings should be basically kept unchanged during casting. By regulating the conveyance and discharge of the molding material components, basically constant and optimal molding material properties (molding material regulation) can be achieved in the molding material cycle. Here, in each cycle, the required addition rates of clay containing montmorillonite (selective addition), additives, water, and new sand or the regenerated second and third molding materials as defined above are determined, and the amount of used sand to be discharged is determined and the machine parameters such as mixing time or cooling intensity are determined to adjust, that is, optimally set the molding material.

[0031] The molding material for manufacturing clay-bonded molds usually contains additives in the form of so-called bright carbon formers in industrial practice.

[0032] Bright carbon former (also called bright carbon carrier A bright carbon former (see https: / / www.giesserei-praxis.de / giesserei-lexikon / glossar / glanzkohlenstoff) is a molding material additive capable of forming hydrocarbon-containing gases. During casting, the molding material additive cokes in the reducing atmosphere of the mold cavity. Bright carbon is produced here. Commonly used bright carbon formers are, for example, coal dust, wood tar (Peche), bitumens, resins, oils, plastics, and their mixtures.

[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. Additionally, the bright carbon former in the molding material can buffer quartz expansion and prevent sand expansion defects. However, an increased share of coal dust or other bright carbon formers in the recycled molding material or a higher share of the decomposition products (coke) of the bright carbon former increases the water requirement of the molding material. An increase in the water content in the molding material can lead to casting defects such as blowhole penetration.

[0034] Since the bright carbon former undergoes thermal decomposition and coking during casting, in industrial practice, the corresponding losses in the molding material cycle must be replaced regularly by feeding in new bright carbon former. For this purpose, new bright carbon former is added at least in several cycles of the molding material cycle, preferably in all cycles.

[0035] A substantial disadvantage of using bright carbon formers is the release of emissions, which are, for example, in the form of CO, CO2, NO x and volatile organic compounds, especially aromatic hydrocarbons such as benzene, toluene, and xylene ("BTX emissions") as well as polycyclic aromatic hydrocarbons. Additionally, volatile sulfur-containing compounds are usually also emitted because bright carbon formers usually contain sulfur and / or sulfur-containing impurities. Another problem is that there is a significant risk of dust explosion and spontaneous combustion during the handling of bright carbon formers. Therefore, in industrial casting operations, when manufacturing clay-bonded molds, bright carbon formers are used in the form of mixtures that are usually prefabricated by suppliers and contain smectite-containing clays, especially bentonite.

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

[0037] US 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 metal hydroxide, such as aluminum, calcium, iron, sodium, magnesium, boron, or zinc. The guidance of the molding material in a cycle is not disclosed. Accordingly, this document does not introduce information on whether such a molding material is suitable for the molding material cycle.

[0038] WO 03 / 066253 A1 describes a method for manufacturing a molding material for casting purposes, especially for guidance in a cycle, according to which a material that cannot swell in water is added to a mixture consisting of particulate matter and additives such as a binder (such as bentonite) and water. Especially framework silicates or network silicates, such as zeolites, pumice or volcanic rock, allophane, imogolite, diatomaceous earth (Kieselgur), hydrated magnesium aluminum silicate, sepiolite, diatomaceous earth (Diatomenerde), or (acid- and / or heat-treated) clay are used as non-swelling porous materials.

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

[0047] The main object of the present invention is to reduce carbon-based emissions and / or carbon-based casting defects. Here, carbon-based emissions include, for example, emissions in the form of CO, CO2, and volatile organic compounds, especially aromatic hydrocarbons such as benzene, toluene, and xylene ("BTX emissions"), as well as polycyclic aromatic hydrocarbons.

[0048] This object is achieved by a method for guiding a molding material in a molding material comprising two or more cycles, the method having the following steps:

[0049] - In an earlier cycle of said two or more cycles of the molding material cycle, casting is carried out in a mold containing a molding material bonded with smectite-containing clay, wherein a cast molding material is obtained.

[0050] - Regenerate the cast molding material so as to obtain a regenerated first molding material.

[0051] - In a later cycle of said two or more cycles of the molding material cycle, a molding material is manufactured, said molding material comprising

[0052] (i) the regenerated first molding material,

[0053] and

[0054] (ii) additives, including

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

[0056] - a molding substrate,

[0057] - a regenerated second molding material, which is manufactured by regenerating a molding material from an uncast mold and / or core and / or part thereof.

[0058] - a regenerated third molding material, which is manufactured by regenerating a molding material from a mold and / or core and / or part thereof that has been cast outside said molding material cycle.

[0059] - an additive, said additive containing at least one dehydratable inorganic compound that separates water at a temperature of 150 ° C or higher.

[0060] - and optionally, smectite-containing clay, preferably bentonite.

[0061] wherein at least one of the regenerated molding materials in the regenerated molding material comprises a material from a core and / or part thereof, said core having been made by an organic binder.

[0062] wherein the molding material manufactured in the later cycle contains carbon, wherein at least 70% by weight, preferably at least 80% by weight and particularly preferably at least 90% by weight, and most particularly preferably at least 95% by weight of the carbon is from the reaction product of the organic binder and binder of the cast and uncast cores.

[0063] Preferably, the additives also include water.

[0064] The molding material cycle involved in the method according to the invention is preferably an industrial molding material cycle in a foundry, preferably a foundry having at least one production line incorporated into the molding material cycle and optionally at least another production line for producing and / or casting molds and / or cores not bonded with clay.

[0065] It is not necessarily required to add the additives defined above in each cycle of the molding material cycle. The molding material cycle according to the invention can include individual cycles without adding said additives.

[0066] Other features, details, advantages and preferred embodiments of the method according to the invention result from the following description and the appended claims and drawings.

[0067] The carbon content of the molding material is determined by elemental analysis and includes the carbon fractions from organic carbon carriers and from inorganic carbon carriers. The organic carbon carriers are in particular bright carbon formers, organic binders, organic additives and the residues or decomposition products of bright carbon formers, organic binders, organic additives. The inorganic carbon carriers are in particular carbonates that may be contained in the molding material.

[0068] By stipulating that at least 70% by weight, preferably at least 80% by weight and particularly preferably at least 90% by weight, preferably at least 95% by weight and particularly preferably 99% of the carbon contained in the molding material manufactured in a later cycle is from the organic binder, the proportion of other carbon carriers in the molding material, in particular bright carbon formers, is restricted.

[0069] In molding materials having smectite-containing clay as a binder, the carbon content can in particular be reduced by reducing or avoiding the use of bright carbon formers.

[0070] By reducing or even avoiding the use of bright carbon formers, fossil resources are protected. Therefore, another object achieved by the present invention is to provide a resource-saving molding material cycle.

[0071] By reducing or even avoiding the use of bright carbon formers, the risk of dust explosion and spontaneous combustion during the transportation, storage and handling of bright carbon formers is reduced or even eliminated. Therefore, another object achieved by the present invention is to reduce the risk of dust explosion and spontaneous combustion during the transportation, storage and handling of bright carbon formers.

[0072] By reducing or even avoiding the use of bright carbon formers, there are fewer pyrolysis products generated during casting that would contaminate the cast molding material or the molding material recycled from the cast molding material. The lower carbon and sulfur content in the molding material with the reduction in the use of bright carbon formers is also beneficial for the landfill of the non-reusable share of the molding material. Thus, another object achieved by the present invention is to simplify the reuse or landfill of the cast molding material.

[0073] Thus, other objects achieved by the present invention are to reduce sulfur-based emissions and NOx emissions during the recycling of the molding material including two or more cycles.

[0074] Another object achieved by the present invention is to reduce the odor pollution released during casting.

[0075] The reduction in the bright carbon share should not cause unacceptable damage to the properties of the molding material, the mold made from the molding material, and the castings made therefrom.

[0076] The solution to the objects defined above is based on the use of additives which are similar in effect to the bright carbon formers used in the prior art in terms of avoiding mold expansion defects, separation between the metal and the molding material, and promoting mold decomposition. It has surprisingly been found that dehydratable inorganic compounds which separate water at a temperature of 150 °C or higher can be similar in effect to the bright carbon formers used in the prior art in terms of avoiding mold expansion defects and promoting mold decomposition.

[0077] Dehydration means the separation of chemically (e.g., in the form of hydroxide ions) or physically (e.g., as crystal water in a hydrate) bound water by heating.

[0078] The dehydratable inorganic compounds contained in the additives to be used according to the present invention preferably relate to compounds from the group of metal hydroxides and hydrated salts. As used herein, the term hydroxide also includes oxidhydroxide. Preferred are hydroxides and hydrated salts of metals in the +II or +III oxidation state, particularly preferred are hydroxides of metals in the +II or +III oxidation state. Particularly preferred are magnesium hydroxide (especially in the form of brucite) and aluminum hydroxide, and most preferred is aluminum trihydroxide Al(OH)3. Here, aluminum trihydroxide can exist in different polymorphic forms, especially as gibbsite, bayerite or nordstrandite, and can also exist in minerals in combination with other hydroxides or oxides.

[0079] Preferably, the additive comprises one or two compounds from the group consisting of aluminium hydroxide and magnesium hydroxide. Preferably, based on the total mass of aluminium hydroxide and magnesium hydroxide in the additive, the share of aluminium hydroxide is at least 80%, preferably at least 90% and particularly preferably at least 95%, more particularly preferably 99%.

[0080] The additive to be used according to the invention preferably does not include carbon or a carbon carrier.

[0081] In the preferred embodiment of the method according to the invention, in an earlier cycle of two or more cycles of the moulding material cycle, casting is carried out on a mould bonded with smectite clay, wherein a casting is produced. The cast moulding material is obtained from the casting of the mould. The cast moulding material is regenerated in the above-mentioned manner such that a first regenerated moulding material is obtained. In order to keep the quality of the moulding material guided in the cycle constant, optionally a part of the cast moulding material is removed during regeneration such that a moulding material that has undergone removal is obtained.

[0082] However, it is not mandatory to remove the regenerated moulding material in each cycle of the moulding material cycle. The moulding material cycle according to the invention may include individual cycles in which the regenerated moulding material is not removed.

[0083] In a later cycle of the moulding material cycle, a moulding material is produced, which comprises (i) the first regenerated moulding material as defined above, and (ii) an additive. The additive comprises

[0084] - an additive as defined above,

[0085] - and one or more raw materials from the following group,

[0086] - a mould substrate, in particular quartz sand,

[0087] - a second regenerated moulding material, which is produced by regenerating a moulding material from an uncast mould and / or core and / or a part thereof,

[0088] - a third regenerated moulding material, which is produced by regenerating a moulding material from a mould and / or core and / or a part thereof cast outside the moulding material cycle,

[0089] - and optionally, a smectite-containing clay, preferably bentonite.

[0090] If a part of the cast molded material is not removed after regeneration, then in order to keep the quality of the molded material guided in the cycle constant, a part of the manufactured molded material can now be removed so that the molded material after removal is obtained. However, this is not necessarily required. The molded material cycle according to the invention can include individual cycles in which no removal of the molded material is carried out.

[0091] At least one of the regenerated molded materials (such as the first, second, and third regenerated materials defined above) used in the method according to the invention includes an organic binder and / or its reaction product. The organic binder is preferably: polyurethane, especially polyurethane formed in the cold box process; or a phenolic resin in the form of a novolac resin or a phenolic varnish. The cast core or mold contains the reaction product of the organic binder during casting.

[0092] The molded material manufactured in a later cycle of the molded material cycle includes one, more, or all of the above raw materials. The molded substrate used as a raw material preferably includes new quartz sand (new sand), or silica sand, olivine sand, chromite sand, zircon sand, or artificial ceramic sand, or a mixture of said sands.

[0093] The smectite-containing clay is preferably bentonite, especially bentonite from the group consisting of sodium bentonite, calcium bentonite, and mixtures thereof.

[0094] The regenerated second molded material defined above is manufactured by regenerating the molded material from an uncast mold and / or core and / or a part thereof. The uncast mold and / or core refers to a mold and / or core that has not been cast for various reasons, such as due to processing defects or insufficient dimensional accuracy.

[0095] The regenerated third molded material defined above is manufactured by regenerating the molded material from a mold and / or core and / or a part thereof that has been cast outside the observed molded material cycle, that is, for example, a mold and core cast in another production line.

[0096] Preferably, the molded material manufactured in the later cycle has one or more of the following parameters:

[0097] - A carbon concentration of less than 4%, preferably less than 3%, by mass of the molded material, determined by elemental analysis,

[0098] - A nitrogen concentration of less than 0.2%, preferably less than 0.1%, by mass of the molded material, determined by elemental analysis,

[0099] - A sulfur concentration of less than 0.05%, preferably less than 0.03%, by mass of the molded material, determined by elemental analysis,

[0100] - A burning loss of at most 5%, preferably at most 4%, determined according to the VDG operating specification P33 (April 1997).

[0101] Particularly preferably, the molded material produced in a later cycle has one or more of the following parameters:

[0102] - A carbon concentration of less than 3%, preferably less than 2.5%, particularly preferably less than 2%, by mass of the molded material, determined by elemental analysis,

[0103] - A nitrogen concentration of less than 0.1%, preferably less than 0.07%, particularly preferably less than 0.05%, by mass of the molded material, determined by elemental analysis,

[0104] - A sulfur concentration of less than 0.03%, preferably less than 0.01%, particularly preferably less than 0.05%, by mass of the molded material, determined by elemental analysis,

[0105] - A burning loss of at most 4%, preferably at most 3.5%, particularly preferably at most 3%, determined according to the VDG operating specification P33 (April 1997).

[0106] Preferably, all of the above parameters of the molded material are within the above - preferred, particularly the above - particularly - preferred ranges.

[0107] In one embodiment of the method according to the invention, in an earlier cycle, casting is carried out in a mold having at least one inserted core, which has been produced with an organic binder. Here, a cast molded material is obtained, which comprises the material from the cast mold and the material from the cast core. The material from the cast core comprises the reaction products formed during casting of the organic binder.

[0108] Cores inserted into clay - bonded molds are generally not clay - bonded. In the embodiment described here of the method according to the invention, the core is produced with an organic binder. Preferably, the organic binder is polyurethane, particularly polyurethane formed in a cold - box process, or the organic binder is a phenolic resin in the form of a resol or a novolak. Thus, the cast molded material obtained in an earlier cycle of the molding material cycle and the resulting recycled first molded material contain the materials from at least one cast mold and at least one cast core cast in the same casting process.

[0109] In the described embodiment of the method according to the invention, it is possible to use a regenerated second molding material containing material from an uncast mold and / or core and / or parts thereof, where the mold and / or core is preferably made of an organic binder, such as a cold box binder, or made of a phenolic resin in the form of a resole or a novolak; and / or it is possible to use a regenerated third molding material containing material from a cast mold and / or core and / or parts thereof, where the mold and / or core is preferably made of an organic binder, such as a cold box binder, or made of a phenolic resin in the form of a resole or a novolak.

[0110] In another embodiment of the method according to the invention, in an earlier cycle, casting is carried out in a mold without inserting a core, so that the regenerated first molding material does not contain material from a cast core. In the described embodiment of the method according to the invention, the regenerated second molding material includes material from an uncast core and / or mold and / or parts thereof, where the mold and / or core is made of an organic binder; and / or the regenerated third molding material contains material from a cast mold and / or core and / or parts thereof, where the mold and / or core is made of an organic binder. Preferably, the organic binder is a polyurethane, especially a polyurethane formed in a cold box process, or a phenolic resin in the form of a resole or a novolak. The material from the cast mold and core includes the reaction products of the organic binder during casting.

[0111] In the method according to the invention, the molding material guided in a cycle is preferably used for manufacturing a mold for cast iron.

[0112] In the method according to the invention, the earlier and later cycles of the method according to the invention and preferably all cycles preferably include the following steps (see Figure 2 , the other features of which should not be restrictive):

[0113] (Step 1) Manufacturing the molding material, i.e., manufacturing a molding material including:

[0114] (i) A regenerated first molding material manufactured by regenerating a cast molding material obtained in an earlier cycle of the molding material cycle as defined above,

[0115] And

[0116] (ii) Additives as defined above,

[0117] (Step 2) Manufacturing the mold, i.e., manufacturing a mold bonded with montmorillonite-containing clay from the molding material manufactured in step (1),

[0118] (Step 3) Casting, i.e., manufacturing a casting by casting the mold manufactured in step (2),

[0119] (Step 4) Separation, i.e., separating the casting produced in step (3) from the mold, where the cast molding material is obtained.

[0120] (Step 5) Recycling the cast molding material, i.e., recycling the cast molding material in step (4) such that a recycled first molding material is obtained for manufacturing a new molding material in step (1) of a later cycle, and optionally removing a part of the cast molding material such that a molding material after removal is obtained.

[0121] If a part of the cast molding material is not removed during recycling in step (5), then in order to keep the quality of the molding material guided in the cycle constant, a part of the molding material manufactured in step (1) of the next cycle can be removed such that a molding material after removal is obtained.

[0122] In a specific 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 include the following steps (see Figure 4 , the other features of which should not be restrictive):

[0123] (Step 1) Manufacturing a molding material, i.e., manufacturing a molding material comprising

[0124] (i) a recycled molding material manufactured by recycling the cast molding material obtained in an earlier cycle of the molding material cycle as defined above,

[0125] and

[0126] (ii) additives as defined above,

[0127] (Step 1a) Manufacturing a core molding material, i.e., manufacturing or providing a molding material for manufacturing at least one core, where the molding material contains an organic binder, preferably a cold box binder, or contains a phenolic resin in the form of a resole or a novolak.

[0128] (Step 2) Manufacturing a mold, i.e., manufacturing a mold bonded with montmorillonite-containing clay from the molding material manufactured in step (1).

[0129] (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).

[0130] (Step 3) Casting, i.e., manufacturing a casting by casting the mold manufactured in step (2) with at least one core inserted in step (2a).

[0131] (Step 4) Separation, i.e., separating the casting produced in step (3) from the mold and at least one core, whereupon the cast molding material is obtained, the molding material containing material from the cast mold and the cast core,

[0132] (Step 5) Recycling, i.e., recycling the cast molding material in step (4) such that recycled first molding material is obtained for producing new molding material in step (1) of a later cycle, and optionally removing a portion of the cast molding material such that the molded material after removal is obtained.

[0133] If no portion of the cast molding material is removed during recycling in step (5), then in order to keep the quality of the molding material guided in the cycle constant, a portion of the molding material produced in step (1) of the next cycle is removed such that the molded material after removal is obtained.

[0134] In certain cases, preferably, one, several or all cycles of the molding material cycle include other steps, and / or individual steps among said steps have other features. Details regarding this are derived from the following description as well as the appended claims and drawings.

[0135] Particularly when producing the molding material in step (1) of the molding material cycle, preferably the recycled molding material is mixed with additives. Preferably, the additives also include water added in step (1).

[0136] Preferably, the mold with the casting and (if any) at least one core is cooled before separation in step (4).

[0137] Preferably, the cast molding material is cooled before recycling.

[0138] Recycling generally includes removing as much as possible metal residues and other impurities, such as impurities caused by auxiliary products (core heads, riser residues, etc.) during the casting process, and comminuting (particle separation) the cast molding material.

[0139] Wear products are generated by thermal, mechanical and possibly chemical loads, such as fines sand fraction, inert clay fraction, decomposition products of additives and / or bright carbon formers, or reaction products of core binders and oolitic particles of the molding substrate.

[0140] In order not to allow such wear products to accumulate in the molding material cycle, and / or not to have an adverse effect on the properties of the molding material, and / or in order not to cause a sharp reduction in the required active ingredients of the binder (smectite-containing clay) and the additives to be used according to the invention, in the corresponding subsequent cycles, in particular in step (1) when manufacturing the molding material, an additive is added to the molding material, i.e., the recycled 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 the molding material is removed from the molding material cycle. This can be done before the repair with the additive (i.e., in particular in step (5)), or after the repair with the additive, i.e., after manufacturing the molding material in a later cycle. In the latter case, the amount of the additive added is kept as low as possible.

[0141] Therefore, in some cases, step (5) includes: necessarily removing the same amount of the cast molding material as that repaired by the additive including the additive to be used according to the invention in step (1) of the next cycle; it is feasible to achieve a uniform property level in this way.

[0142] Preferably, in step (5), 0.5 wt% to 20 wt%, preferably 2 wt% to 15 wt%, particularly preferably 5 wt% to 10 wt% of the cast molding material (sand discharge) is removed, and in step (1) of the next cycle, a corresponding amount of the additive is added in order to keep the quality of the molding material guided in the cycle constant.

[0143] If a part of the cast molding material is not removed in step (5), then in order to keep the quality of the molding material guided in the cycle constant, 0.5 wt% to 20 wt%, preferably 2 wt% to 15 wt%, particularly preferably 5 wt% to 10 wt% of the molding material manufactured in step (1) is removed.

[0144] The molding material cycle involved in the method according to the invention preferably includes at least 10 cycles, preferably at least 15 cycles, particularly preferably at least 30 cycles.

[0145] The additive to be used according to the invention (as defined above) is preferably free-flowing and / or pourable. The additive preferably exists in the form of a powder or granules. The additive particularly preferably exists in the form of particles with a particle size of 20 μm to 200 μm determined by means of a laser particle size analyzer.

[0146] Preferably, based on the total mass of the additives defined above, the share of the dehydratable inorganic compounds from which water is separated at a temperature of 150 °C or higher is from 1% to 100%. Particularly preferably, based on the total mass of the additives defined above, the share of the dehydratable inorganic compounds from which water is separated at a temperature of 150 °C or higher is from 20% to 100%. Even more particularly preferably, based on the total mass of the additives defined above, the share of the dehydratable inorganic compounds from which water is separated at a temperature of 150 °C or higher is from 30% to 100%. Especially preferably, based on the total mass of the additives defined above, the share of the dehydratable inorganic compounds from which water is separated at a temperature of 150 °C or higher is from 50% to 100%.

[0147] In some cases it is preferred that the additives to be used according to the invention, in addition to one or more of the said dehydratable inorganic compounds, contain one or more constituents from the group consisting of:

[0148] - inorganic carbonates,

[0149] - bright carbon formers.

[0150] It is clear to the person skilled in the art here that the amount of carbon added to the moulding material via the additive should be limited such that the carbon concentration in the moulding material is not higher than 4% by weight, preferably not higher than 2.5% by weight, more preferably not higher than 2.0% by weight, and particularly preferably not higher than 1.5% by weight.

[0151] It is clear to the person skilled in the art here that the amount of carbon added to the moulding material via the additive should be limited such that at least 70% by weight, preferably at least 80% by weight, and particularly preferably at least 95% by weight of the carbon contained in the moulding material produced in a later cycle is derived from the organic binder.

[0152] Preferably, the additive contains aluminium hydroxide, wherein the aluminium hydroxide contained in the additive can have a water content in the range from 0.01% to 20%, preferably from 0.01% to 12%. Particularly preferred is aluminium hydroxide with a water content below 1% (i.e. a water content of less than 1%) determined by thermogravimetric analysis in the temperature range up to 105 °C. It is thus not necessary to expend particularly large amounts to dry the aluminium hydroxide.

[0153] In the additive, the aluminium hydroxide can be present in the form of a mixture with iron oxide and / or iron hydroxide, wherein, based on the total mass of the aluminium hydroxide, iron oxide and / or iron hydroxide, the share of the aluminium hydroxide is greater than 40%.

[0154] The pH value of the additive to be used according to the invention is preferably in the range from 7 to 14, which is determined in accordance with DIN 19747:2009-07 (Sample preparation), DIN EN 12457-1:2003-01 (Leaching) and DIN EN ISO 10523:2012-04 (Determination of the pH value).

[0155] 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.

[0156] Preferably, based on the total mass of the additive, the total share of the elements from the group consisting of Pb, Cd, Cr, Co, Cu, Mo, Ni, Hg, Se, Zn, P, As, F, Br and Cl is 1 wt% or less, preferably 0.5 wt% or less, particularly preferably 0.1 wt% and very particularly preferably 0.05 wt%.

[0157] In the production of the moulding material (step (1)), the order in which the individual components are added together is flexible.

[0158] The additives can for example be provided as a mixture.

[0159] Alternatively, the additives, i.e. the additive and the smectite-containing clay, can be provided as a mixture and the other additives separately therefrom. This corresponds to the currently common provision of bright carbon formers in a pre-mixture with smectite-containing clay. Existing equipment in the foundry can thus continue to be used for storage and metering.

[0160] Alternatively, the additive can be provided separately from the other additives.

[0161] Alternatively, the additive and the optional smectite-containing clay, or the pre-mixture consisting of the additive and the smectite-containing clay, can first be mixed with the recycled first moulding material and subsequently the other starting materials described above can be added.

[0162] Preferably, based on the total mass of the moulding material to be produced, consisting of

[0163] - a moulding substrate,

[0164] - a recycled second moulding material which is produced by recycling the moulding material from uncast moulds and / or cores and / or parts thereof,

[0165] - a recycled third moulding material which is produced by recycling moulds and / or cores and / or parts thereof which have been cast outside the moulding material cycle,

[0166] The total mass of the raw materials in the composition is from 0.5% by weight to 10% by weight, preferably from 1% by weight to 8% by weight, particularly preferably from 1.5% by weight to 7% by weight.

[0167] Based on the total mass of the molding material to be produced, the mass of the additive, i.e., the clay containing smectite, is preferably from 0.1% by weight to 1.5% by weight, more preferably from 0.3% by weight to 1.2% by weight, particularly preferably from 0.5% by weight to 1.0% by weight.

[0168] Based on the total mass of the molding material to be produced, the total mass of the dehydratable inorganic compound that separates out water at a temperature of 150 °C or higher and is input as an additive is from 0.1% by weight to 1% by weight, preferably from 0.3% by weight to 0.8% by weight, particularly preferably from 0.4% by weight to 0.7% by weight.

[0169] The clay containing smectite to be used in the process according to the invention is preferably bentonite, particularly preferably selected from the group consisting of sodium bentonite, calcium bentonite and mixtures thereof.

[0170] Preferably, the molding substrate is selected from the group consisting of quartz sand, olivine sand, chromite sand, zircon sand and artificial ceramic sand, and mixtures of said sands. A clay-bonded mold typically contains at least 40% sand, preferably more than 50% sand, particularly preferably more than 60% sand, and most particularly preferably more than 70% sand.

[0171] The process is preferably designed such that at least 90% by weight of the molding material is subjected to a temperature of at most 1000 °C during casting. At temperatures above 1000 °C, aluminum hydroxide irreversibly converts to corundum (α-aluminum hydroxide), which cannot be converted back to aluminum hydroxide by adding water in a later cycle and thus can no longer function as an additive to be used according to the invention as defined above.

[0172] Therefore, it is preferred that less than 50% by weight, preferably less than 25% by weight, particularly preferably less than 10% by weight of the Al2O3 contained in the molding material is present in the form of corundum.

[0173] Preferably, the molding material produced in a later cycle of the process according to the invention has the following parameters:

[0174] - A degree of compaction in the range of 25% to 55%, determined according to VDG operating specification P37 (April 1997), and / or

[0175] - A wet compressive strength in the range of 8 N / cm 2 to 35 N / cm 2 determined according to VDG operating specification P38 (May 1997), and / or

[0176] - Wet tensile strength in the range of 0.10 N / cm 2 to 0.50 N / cm 2 is determined according to VDG operating specification P38 (May 1997), and / or

[0177] - Air permeability in the range of 70 to 200 is determined according to BDG guideline P41 (October 2013), and / or

[0178] - Active clay content in the range of 4.5% to 16% is determined by the methylene blue method according to VDG operating specification P035 (October 1999), and / or

[0179] - Fluidity of 20% to 90% is determined according to the operating technical document of Morek Multiserw, type LUA - 2e power - driven pile driver, page 7.

[0180] Particularly preferably, the molded material manufactured in a later cycle of the method according to the invention has the following parameters:

[0181] - Compaction degree in the range of 30% to 50% is determined according to VDG operating specification P37 (April 1997), and / or

[0182] - Wet compressive strength in the range of 10 N / cm 2 to 28 N / cm 2 is determined according to VDG operating specification P38 (May 1997), and / or

[0183] - Wet tensile strength in the range of 0.20 N / cm 2 to 0.45 N / cm 2 is determined according to VDG operating specification P38 (May 1997), and / or

[0184] - Air permeability in the range of 90 to 160 is determined according to BDG guideline P41 (October 2013), and / or

[0185] - Active clay content in the range of 6% to 12% is determined by the methylene blue method according to VDG operating specification P035 (October 1999), and / or

[0186] - Fluidity of 50% to 90% is determined according to the operating technical document of Morek Multiserw, type LUA - 2e power - driven pile driver, page 7.

[0187] Preferably, all of the above parameters of the molded material are within the above - preferred ranges, especially within the above - particularly - preferred ranges.

[0188] Another aspect of the present disclosure relates to the use of the additives defined above in the process according to the invention as defined above. The above-described embodiments apply to the additives that are preferably to be used and the preferred process designs. BRIEF DESCRIPTION OF THE DRAWINGS

[0189] The present invention will be described in detail below with reference to the schematic drawings. Shown herein are:

[0190] Figure 1 Showing the molding material cycle according to the prior art (casting in a coreless mold)

[0191] Figure 2 Showing the molding material cycle according to the method of the present invention (casting in a coreless mold)

[0192] Figure 3 Showing the molding material cycle according to the prior art (casting in a mold with a core)

[0193] Figure 4 Showing the molding material cycle according to the method of the present invention (casting in a mold with a core) DETAILED DESCRIPTION

[0194] The period of the molding material cycle depends on Figure 1 and Figure 2 at least includes steps (1) to (5) as defined above, wherein the mold cast in step (3) does not contain the inserted core.

[0195] In step (1), a molding material is produced, the molding material comprising:

[0196] (i) a regenerated first molding material produced by regenerating the cast molding material obtained in an earlier cycle of the molding material cycle, the regenerated first molding material not containing material from the cast core,

[0197] and

[0198] (ii) additives.

[0199] The additives comprise:

[0200] - one or more raw materials from the following group

[0201] - new molding base material (new sand),

[0202] - and at least one regenerated molding material from the following group

[0203] - a regenerated second molding material produced by regenerating an uncast mold and / or core and / or parts thereof,

[0204] - A recycled third molding material, which is manufactured by recycling molds and / or cores and / or parts thereof that are manufactured outside the molding material cycle shown in Figure 1 or Figure 2 and are cast,

[0205] - Montmorillonite-containing clay, preferably bentonite,

[0206] - Water.

[0207] Here, the recycled second molding material contains materials from uncast molds, cores, and / or parts thereof, where the molds and / or cores are manufactured with an organic binder; and / or the recycled third molding material contains materials from cast molds, cores, and / or parts thereof, where the molds and / or cores are manufactured with an organic binder. The organic binder is preferably polyurethane, especially polyurethane formed in the cold box process, or a phenolic resin in the form of a novolac resin or a phenolic varnish. The materials from the cast molds and cores include the reaction products of the organic binder during casting.

[0208] In a method not according to the invention ( Figure 1 ), during the manufacture of the molding material in step (1), at least one bright carbon former is added as another additive.

[0209] In the method according to the invention ( Figure 2 ), during the manufacture of the molding material in step (1), the additives defined above are added as another additive. Preferably, the additive contains or consists of aluminum trihydroxide.

[0210] In step (2), a mold bonded with montmorillonite-containing clay is manufactured from the molding material manufactured in step (1).

[0211] In step (3), a casting is manufactured by casting the mold manufactured in step (2). The mold does not contain an inserted core.

[0212] In step (4), the casting manufactured in step (3) is separated from the mold, where a cast molding material is obtained, and the cast molding material contains materials from the cast mold but does not include materials from the cast core. Preferably, the mold with the casting is cooled before separation in step (4).

[0213] In step (5), the cast molding material from step (4) is recycled to obtain a recycled first molding material for manufacturing a new molding material in a later step (1), particularly in the next cycle. Preferably, the cast molding material is cooled before recycling in step (5). Optionally, a portion of the cast molding material is removed during recycling to obtain the molding material from which the portion has been removed.

[0214] If no portion of the cast molding material is removed during recycling in step (5), then in order to keep the quality of the molding material circulated in the cycle constant, a portion of the molding material manufactured in step (1) of the next cycle is removed to obtain the molding material from which the portion has been removed.

[0215] In a later step (1), particularly in the next cycle, the recycled first molding material obtained in an earlier step (5), particularly in the previous cycle, is used to manufacture a new molding material in the manner described above.

[0216] One cycle of the molding material cycle depends on Figure 3 and Figure 4 at least includes steps (1), (1a), (2), (2a), (3), (4) and (5) defined above, wherein the mold cast in step (3) contains at least one inserted core.

[0217] Manufacturing the molding material in step (1) includes:

[0218] (i) a recycled first molding material manufactured by recycling the cast molding material obtained in an earlier cycle of the molding material cycle, the recycled first molding material including the material from the cast core, the material being manufactured with an organic binder,

[0219] and,

[0220] (ii) additives.

[0221] The additives include:

[0222] - one or more raw materials from the following group:

[0223] - new molding substrate (new sand),

[0224] - and at least one recycled molding material from the following group:

[0225] - a recycled second molding material manufactured by recycling an uncast mold and / or core and / or a portion thereof,

[0226] - a recycled third molding material manufactured by recycling in Figure 3 or Figure 4manufactured from a mold and / or core and / or part thereof that is manufactured outside the molding material cycle shown,

[0227] - montmorillonite-containing clay, preferably bentonite,

[0228] - water.

[0229] In a method not according to the invention ( Figure 3 ), when manufacturing the molding material in step (1), at least one bright carbon former is added as another additive.

[0230] In the method according to the invention ( Figure 4 ), when manufacturing the molding material in step (1), the additives defined above are added as another additive. Preferably, the additive contains or consists of aluminum trihydroxide.

[0231] In step (1a), a molding material (core molding material) for manufacturing at least one core is manufactured or provided. The molding material includes a molding substrate, an organic binder, and optionally additives. Additives for molding materials suitable for manufacturing cores are known from the prior art. The binder is a conventional organic binder, such as a cold box binder, or the organic binder is a phenolic resin in the form of a resol or novolak.

[0232] In step (2), a mold bonded with montmorillonite-containing clay is manufactured from the molding material manufactured in step (1).

[0233] 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).

[0234] In step (3), a casting is manufactured by casting the mold manufactured in step (2), the mold containing at least one inserted core.

[0235] In step (4), the casting manufactured in step (3) is separated from the mold, where a cast molding material is obtained, the molding material including the material from the cast mold and the material from the cast core. The material from the cast core includes the reaction product of the binder formed during casting.

[0236] Preferably, the mold with the casting is cooled before separation in step (4).

[0237] In step (5), the cast molding material from step (4) is recycled so as to obtain a recycled first molding material for manufacturing a new molding material in a later step (1), in particular in the next cycle. Preferably, the cast molding material is cooled before recycling in step (5). When recycling, a part of the cast molding material is removed if necessary so as to obtain a molding material from which the removal has been carried out.

[0238] If no part of the cast molding material is removed when recycling in step (5), then in order to keep the quality of the molding material guided in the cycle constant, a part of the molding material manufactured in step (1) of the next cycle is removed so as to obtain a molding material from which the removal has been carried out.

[0239] In a later step (1), in particular in the next cycle, the recycled first molding material obtained in an earlier step (5), in particular in the previous cycle, is used to manufacture a new molding material in the manner described above.

[0240] The present invention is further described below by way of non-limiting examples.

[0241] 0. Testing methods and molding materials

[0242] 0.1 Testing methods

[0243] The following test methods (measurement methods) are used (Table 1) Table 1: Measurement methods used

[0244]

[0245]

[0246] The sleeve and fin model device is manufactured as described in (https: / / www.researchdisclosure.com / database / RD705032) and used for the following tests.

[0247] 0.2 Materials used

[0248] All specifications of the raw material dosages relate respectively to pure raw materials, i.e. dry materials, i.e. without any possible moisture or water of crystallization.

[0249] In the scope of the tests, the molding material from the conditioned molding material circulation system of the brake disc foundry (hereinafter also referred to as the starting molding material) is used as the starting material for the tests to convert the molding material circulation system containing a bright carbon former. The molding material can be described by the following data (Table 2).

[0250] Table 2: Parameters of the starting molding material

[0251]

[0252]

[0253] Within the scope of the experimental study, recycled molding materials from core sand (the recycled second molding material defined above) are used. For this purpose, cores are manufactured with an organic binder or an inorganic binder and subsequently ground using a circular vibrating screen from Webac.

[0254] The starting material for the molding material made with an organic binder is a core manufactured by the cold box process. The core is manufactured on a core shooter LL20 from Laempe using the binders Biocure 8568P1 / Silcure 8431P2 sold by Hüttenes-Albertus Chemische Werke GmbH. For this purpose, sand type H32 from Quartzwerke is used, and 0.7 parts by weight of the binder component is dosed per 100 parts by weight of sand. Cores are manufactured with a sand injection pressure of 450 kPa (4.5 bar) and a sand injection time of 1.5 seconds. Subsequently, 10 g of dimethylpropylamine (N,N-dimethylpropylamine, catalyst GH6 from Hüttenes-Albertus Chemische Werke GmbH) is passed through for 45 s at a supply pressure of 200 kPa (2 bar) for curing.

[0255] The starting material for the molding material made with an inorganic binder is a core manufactured on a core shooter LL20 from Laempe using the binder system Cordis 9477 / Anorgit 9476 sold by Hüttenes-Albertus Chemische Werke GmbH. For this purpose, sand type H32 from Quartzwerke is used, and 2.2 parts by weight of Cordis 9477 and 1.15 parts by weight of Anorgit 9476 of the binder component are dosed per 100 parts by weight of sand. Cores are manufactured in a core box heated to 180 °C with a sand injection pressure of 450 kPa (4.5 bar) and a sand injection time of 1.5 seconds. For curing, the core is passed through hot air at 120 °C for 1 minute at a supply pressure of 200 kPa (2 bar).

[0256] The cores are ground using a circular vibrating screen (test equipment Kreisschwingsieb-175056 from Webac). The resulting molding material has the properties listed in Table 3.

[0257] Table 3: Parameters of the recycled molding material from core sand

[0258]

[0259]

[0260] The abbreviation NG indicates that the measured value is below the detection limit.

[0261] The starting materials for the cores that were not decomposed under the test conditions (i.e., the cores that were not decomposed during separation (step (4)), see point 3 below, test series A) were quartz sand of type HAP 0.20 / 0.315 / 0.40 from HA Polska, and an inorganic binder consisting of sodium silicate Steinex 48 / 50 from Eurochemie GmbH and 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 into 100 parts by weight of quartz sand, and the shape of the core was formed in a Schüttkernkasten. Subsequently, hot CO2 at 100 °C was supplied to the core for 60 s with a supply pressure of 150 kPa (1.5 bar) in a laboratory core shooter from Morek to cure the core.

[0262] 1. Screening tests for identifying suitable additives

[0263] 6 kg of quartz sand (H32 from Quarzwerke) was mixed with 120 ml of water in a mixer (pan mill LM-2e from Morek MULTISERW) at a speed of 40 rpm for 2 min. Subsequently, 0.48 Kg of bentonite (dry weight) (Natroben 25F, Clariant) and 0.30 Kg of additive (dry weight) were added and mixed at a speed of 40 rpm for 7 min. The mixture thus obtained was manually sieved through a sieve with a mesh width of 3 mm, and then the compactness (VDK) of the material (testing equipment model: PVG; ID No: 1501, manufacturing year: 2000) was determined. If the VDK was greater than 46.0%, the mixture was sieved again and the measurement of the VDK 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 another 1 min, and then sieving and measurement of the VDK were repeated. Water addition was repeated until the VDK exceeded 44.0%.

[0264] Three different mixtures containing a bright carbon former according to the prior art were used as references for the properties of the molding material:

[0265] 1) A commercially available premix consisting of 25% bright carbon former (“sea coal”) and 75% sodium bentonite (NEMIR 2575) from HA Italia S.p.A.,

[0266] 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)

[0267] 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).

[0268] In addition to the molded material property values, the casting quality is also a decisive criterion for the selection of suitable additives. For this purpose, i.e., to test the casting quality, casting is carried out by means of the sleeve mold device described in (https: / / www.researchdisclosure.com / database / RD705032), i.e., a mold manufactured according to the sleeve mold device described in (https: / / www.researchdisclosure.com / database / RD705032) is cast, then the castings are shot-peened, and the surface roughness is measured according to DIN EN ISO 4287 (R_ISO). Two castings are studied respectively. Here, the surface is measured 3 times respectively at small, medium, and large distances of the star-shaped ribs at a measurement distance of 8 mm each by means of a surface measuring instrument Mitutoyo SJ-500P. No unified trend could be determined regarding the distance between the ribs and the surface roughness. Therefore, for the sake of simplicity in evaluation, the average value of all the measurements performed is taken. It is confirmed here that the surface roughness in all the obtained castings is within the range allowed for commercial use.

[0269] 1.1 Different types of aluminum hydroxide and magnesium hydroxide as additives

[0270] SH500 type (SH500 nuance-00, Alteo) and SH950 type (SH950 nuance-00, Alteo) Al(OH)3 are used for the study of aluminum hydroxide.

[0271] Type 1 brucite, type 2 brucite, and type 3 brucite from Ziegler&Co.GmbH are used for the study of magnesium hydroxide (Table 4, all values are from the technical data sheet of Ziegler Company in October 2020).

[0272] Table 4: Parameters of the brucite types used as additives

[0273]

[0274]

[0275] Table 5 shows the molding material properties and roughness of the casting when different hydroxides and bright carbon formers 1) to 3) used as references are applied. The dry compressive strength (TDF) < 35 N / cm 2 and the water content < 2.8% are regarded as particularly advantageous, while the dry compressive strength (TDF) > 50 N / cm 2 and the water content > 3.2% are evaluated as disadvantageous. Hydroxides, especially aluminum hydroxide Al(OH)3 and magnesium hydroxide Mg(OH)2, can be used to manufacture molds and show good molding material characteristic values (see Table 5).

[0276] Table 5: Molding material properties and roughness of the casting when different hydroxides or bright carbon formers are used as additives

[0277]

[0278] 1.2 Study of aluminum hydroxide Al(OH)3 as an additive with the addition of bright carbon former

[0279] The good values of hydroxides, especially aluminum hydroxide Al(OH)3, can be further improved by adding a bright carbon former such as Carboluxon 100 / P, see Table 6. In particular, the surface roughness of the casting can be reduced by using Carboluxon 100 / P, but the values obtained when using pure aluminum hydroxide are sufficient.

[0280] Table 6: Molding material properties and roughness of the casting when using aluminum hydroxide Al(OH)3 SH 950 with the addition of the bright carbon former Carboluxon 100 / P as an additive

[0281]

[0282] 1.3 Study of different carbonates as comparative additives

[0283] Sufficiently good molding material values cannot be achieved by huntite (Huntit) (trade name UltraCarb D98, purchased from LKAB Minerals), while dolomite and manganese carbonate (purchased from TROPAG GmbH) show fully acceptable molding material values (Table 7).

[0284] Dolomite from Bianco Zandobbio 0 / 50 micron of Ziegler company and PE-DOL 90 from Possehl Erzkontor company were used. Generally speaking, the values of the molding materials are slightly worse compared with those of the molding materials when the above-mentioned hydroxides are applied. However, these values still allow the materials to be used as a substitute for traditional bright carbon formers. However, the disadvantage of the carbonate is that it contains carbon.

[0285] Table 7: Molding material properties when different carbonates or bright carbon formers are applied as additives

[0286]

[0287] The molding material properties can be improved by mixing carbonates and hydroxides (Table 8). Here, MixMag is a 50% / 50% mixture of brucite (93% Mg(OH)2) and magnesite ore (92% MgCO3) purchased from Possehl Erzkontor GmbH&Co.KG company, and Dolomag is a 50% / 50% mixture of brucite (93% Mg(OH)2) and dolomite (95% CaMg(CO3)2) also purchased from Possehl Erzkontor company.

[0288] Table 8: Molding material properties and roughness of castings when different carbonate-hydroxide mixtures are applied

[0289]

[0290] 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 values of the molding materials can be further improved (Table 9).

[0291] Table 9: Molding material properties when different carbonate-hydroxide mixtures with Carboluxon 100 / P added as a bright carbon former are used

[0292]

[0293] 1.4 Emissions of bentonite used and additives used

[0294] 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 Freiberg University; for this purpose, the materials were introduced into a tube furnace at 900 °C, and the emissions generated were measured by means of on-line FT-IR; calibration was carried out via test gases.

[0295] The emissions of the additives to be used according to the invention are significantly lower than those of traditional bright carbon formers, such as the coke powder of LuxCarbon or the product Carboluxon 100 / P described above. Although carbonates (not according to the invention), such as manganese carbonate, reduce the emissions of hydrocarbons, especially benzene, toluene, and xylene, they are expected to cause a significant increase in CO2 emissions compared to hydroxides, such as Al(OH)3. Therefore, according to the invention, it is preferred to use carbonates in combination with hydroxides.

[0296] Table 10: Results of emission measurements with different additives (all data in mg / kg, i.e., relevant emissions in mg / kg of material)

[0297]

[0298] 2. Manufacture and testing of molding materials in the cycle

[0299] The purpose of the test was to cast a specific amount of molding material multiple times and regenerate it. As is common in industrial casting, the molding material is led in a cycle here. An additive is fed during each regeneration of the molding material, and the additive accumulates with each cycle. The components that were present in the starting molding material and are no longer added decrease, i.e., the share of the components that are not added in subsequent cycles decreases. The total amount of molding material in the cycle is constant, at approximately 8 kg. Two molds are fabricated and cast per cycle according to the sleeve model device as described in (https: / / www.researchdisclosure.com / database / RD705032).

[0300] For instructions on the test execution, see Figure 2 the molding material cycle in

[0301] The cycle of the molding material cycle includes the following steps:

[0302] Manufacture of molding materials (step (1), first cycle)

[0303] Test series 2.1, 2.2.1, 2.2.2, 2.3.1, 2.3.2 are as follows

[0304] In the first cycle, 6 kg of quartz sand of type H32 from Quartzwerke was used. Subsequently, the molded substrate was combined with 480 g of sodium bentonite (Natroben 25F, HITALIA S.p.A., a sodium bentonite manufactured by activating natural calcium bentonite), and 300 g of the corresponding additives and 120 ml of water were mixed anhydrously for 1 minute on a pan mixer from Morek Multiserw, and then mixed again for 7 minutes after adding water. For this purpose, first the molded substrate was mixed with 120 ml of water on a pan mixer from Morek Multiserw for 1 minute, and then mixed again for 7 minutes on a pan mixer from Morek Multiserw after adding 480 g of sodium bentonite (Natroben 25F, HITALIA S.p.A.) and 300 g of the corresponding additives.

[0305] Test series 2.4 - 2.6 are as follows

[0306] In the first cycle, 3.7 kg of quartz sand of type H32 from Quartzwerke was used. Subsequently, the molded substrate was combined with 322 g of Volclay (foundry bentonite GEKO V from Clariant GmbH, Germany, which is a naturally occurring sodium bentonite) and 207 g of the corresponding additives and 130 ml of water were mixed anhydrously for 1 minute on a pan mixer from Morek Multiserw, and then mixed again for 7 minutes after adding water. For this purpose, first the molded substrate was mixed with 130 ml of water on a pan mixer from Morek Multiserw for 1 minute, and then mixed again for 7 minutes on a pan mixer from Morek Multiserw after adding 322 g of Volclay and 207 g of the corresponding additives. TM V, which is a naturally occurring sodium bentonite) and 207 g of the corresponding additives and 130 ml of water were mixed anhydrously for 1 minute on a pan mixer from Morek Multiserw, and then mixed again for 7 minutes after adding water. For this purpose, first the molded substrate was mixed with 130 ml of water on a pan mixer from Morek Multiserw for 1 minute, and then mixed again for 7 minutes on a pan mixer from Morek Multiserw after adding 322 g of Volclay and 207 g of the corresponding additives.

[0307] Other embodiments apply to all test series 2.1 to 2.6 (unless otherwise stated).

[0308] The additive is conveyed during each manufacture (step (1)) of the molding material, and the additive accumulates with each cycle. By removing a portion of the cast molding material in step (5) or step (1) of the next cycle (see Figure 2 ), the share of the components present in the starting molding material and no longer added is reduced.

[0309] Manufacture of molds (step (2) in all cycles)

[0310] For this purpose, the molding material is filled into the mold of the sleeve molding device after 3 minutes of mixing, and compacted (filled, pressed, refilled, pressed) during 2 pressing processes. This process is completed within another 3 minutes. 2 molds are manufactured for each test.

[0311] Casting (step (3) in all cycles)

[0312] After a waiting time of 30 minutes, the molds are cast in sequence. The molds are cast with the liquid metal of alloy GJL 250 at 1450 °C by means of a casting ladle. The cast molds are left overnight until separation. Here, the casting cools, and the molding material first warms up and cools overnight in the mold.

[0313] Separation (step (4) in all cycles)

[0314] The casting is separated from the cast molding material.

[0315] Regeneration (step (5) in all cycles)

[0316] The molding material is filled into a storage container, and the molding material blocks are crushed. The metal residues are removed.

[0317] Manufacture of molding materials (step (1) in the second cycle and each subsequent cycle)

[0318] New molding material is manufactured by adding bentonite, water, additives (as defined above) and a new molding base material (new sand) or a regenerated second molding material (details see below) manufactured by regenerating the core, and renovating the regenerated molding material (regenerated first molding material) from the previous cycle.

[0319] A new molding base material or a regenerated second molding material (details see below) manufactured by regenerating the core is added to the regenerated molding material from the previous cycle, and mixed with 120 ml of water for 1 minute, and then after adding sodium bentonite (Natroben 25F, HA ITALIAS.p.A., test series 2.1, 2.2.1, 2.2.2, 2.3.1, 2.3.2) or Volclay (foundry bentonite GEKO V of Clariant GmbH, Germany, test series 2.4, 2.5 and 2.6) and the corresponding additives (for the amounts of bentonite and additives see below), it is mixed again for 7 minutes on a Morek Multiserw pan mixer. TM V, test series 2.4, 2.5 and 2.6) and the corresponding additives (for the amounts of bentonite and additives see below), it is mixed again for 7 minutes on a Morek Multiserw pan mixer.

[0320] Adjust the increase in the amount of the molding material caused by the addition in the mixer, i.e., the increase in the amount of the molding material caused by the addition defined above, by removing the same amount of the completely mixed molding material in each cycle.

[0321] The additive is conveyed each time the molding material is produced (step (1)), and the additive accumulates with each cycle. By removing a part of the cast molding material, the share of the components present in the starting molding material and not added in subsequent cycles is reduced.

[0322] 2.1 Addition of additive Al(OH)3 or Mg(OH)2 when adding new molding substrate in subsequent cycles (not according to the present invention) invention

[0323] Use the sleeve model device described in ( https: / / www.researchdisclosure.com / database / RD705032 ) to perform 10 cycles (0 - 9) respectively, where 100% new molding substrate of type H32 from Quartzwerke is used in the first test.

[0324] In all subsequent cycles 1 to 9, 4 kg of used molding material from the previous casting is used respectively, and regeneration is carried out with 400 g of molding substrate (new molding substrate), 64 g of bentonite, and 20 g of the corresponding additive.

[0325] Use SH950 nuance - 00 of Alteo as the additive aluminum hydroxide Al(OH)3. The test results with Al(OH)3 are shown in Table 11.

[0326] Use brucite type 3 of Ziegler&Co.GmbH as the additive magnesium hydroxide Mg(OH)2. The test results with Mg(OH)2 are shown in Table 12.

[0327] In the case of using the new molding substrate as the additive (see Figure 2 , step (1)), both additives show good molding properties and comparable surface quality, which can be seen from the measured roughness of the castings.

[0328] Al(OH)3 as an additive results in a higher active clay content and significantly lower ignition loss. For both Al(OH)3 and Mg(OH)2, the molding substrate properties and the castings have good quality. Correspondingly, the surface roughness of the castings is low.

[0329] Table 11: Characteristic values of the samples taken in the corresponding cycles to determine the properties of the molding material with Al(OH)3 as the additive, and the surface roughness of the castings

[0330]

[0331] Table 12: Eigenvalues of samples taken in the respective cycles to determine the properties of the molding material with Mg(OH)2 as an additive, and surface roughness of the casting

[0332]

[0333] 2.2 Al(OH)3 and Mg(OH)2 when adding cold box core sand in subsequent cycles

[0334] 31 cycles (0 - 30) are carried out separately in the case of using the sleeve model device described in (https: / / www.researchdisclosure.com / database / RD705032). The test execution and the measurement of the molding material properties and the casting properties are carried out as described in Chapter 2.1, but in subsequent cycles, instead of a new molding substrate, a second recycled molding material (see Figure 2 , step (1)) (for the amount fraction of the molding material produced, see Table 13 or 16) is added, which is produced by recycling the uncast cores, and the cores are produced with cold box binder (“cold box core sand”).

[0335] 2.2.1 Aluminum hydroxide Al(OH)3 when adding cold box core sand in subsequent cycles

[0336] In the case of using aluminum hydroxide Al(OH)3, the properties of the molding material show stability when adding 5% of cold box core sand, so that starting from the 15th cycle, the addition of cold box core sand is increased to 10% (Tables 13 and 14). In addition, the properties of the molding material remain stable.

[0337] Table 13: Composition and compaction of the molding material mixture in each cycle

[0338]

[0339]

[0340] Table 14: Eigenvalues of samples taken in the respective cycles

[0341]

[0342]

[0343] Data on the CNS analysis of the molding material in different cycles show an increase in the carbon and nitrogen fractions originating from the addition of cold box core sand. Compared with the test series with the addition of new sand (see 2.1 above) instead of cold box core sand, the surface roughness of the casting is improved due to the addition of the core sand (Table 15).

[0344] Table 15: CNS analysis of selected cycles and surface roughness of the castings belonging thereto

[0345]

[0346]

[0347] (1) The abbreviation NG means that the measured value is below the detection limit.

[0348] 2.2.2 Mg(OH)2 when adding cold box core sand in subsequent cycles

[0349] Using magnesium hydroxide Mg(OH)2 in the form of brucite type 3 as an additive has shown that after several cycles, the properties of the molding material cannot be stably maintained. Therefore, the bentonite content of the molding material was increased in cycles 8 and 14 (Table 16). Nevertheless, no stabilization of the characteristic values of the molding material was achieved (Table 17). In particular, the wet tensile strength decreases with increasing number of cycles, and this trend can only be countered temporarily by adding additional fresh bentonite.

[0350] Table 16: Composition and compactness of the molding material mixture in each cycle

[0351]

[0352]

[0353] Table 17: Characteristic values of the samples taken in the corresponding cycles

[0354]

[0355] As expected, in the case of adding cold box core sand, the carbon content of the molding material increases, and the nitrogen content also increases to a limited extent (Table 18). The surface roughness of the castings is good and not negatively affected. However, different from aluminum hydroxide Al(OH)3 (see test series 2.2.1 above), in the case of adding organic core sand (i.e., cold box core sand, see above), magnesium hydroxide Mg(OH)2 cannot achieve a molding material cycle with stable molding material properties (Table 17).

[0356] Table 18: CNS analysis of selected cycles and surface roughness of the castings belonging thereto

[0357]

[0358] (1) The abbreviation NG means that the measured value is below the detection limit.

[0359] 2.3 Al(OH)3 and Mg(OH)2 when adding inorganically bonded core sand in subsequent cycles (not according to the present invention)

[0360] 31 cycles (0 - 30) were carried out separately in the case of using the sleeve model device described in (https: / / www.researchdisclosure.com / database / RD705032). The tests were carried out and the properties of the molding material and the casting were measured as described in Chapter 2.1. However, in subsequent cycles, instead of a new molding substrate, a recycled second molding material manufactured by recycling uncast cores was added (see Figure 2 , step (1)) (for the amount fraction of the molding material manufactured, see Table 19 or 22), and the cores were manufactured with an inorganic binder (sodium silicate) (“IOB core sand”). Therefore, this is an inorganic molding material cycle for all binders used.

[0361] 2.3.1 Aluminum hydroxide Al(OH)3 when adding inorganically bonded core sand in subsequent cycles

[0362] Even when IOB core sand was added, a molding material cycle with stable molding material properties was obtained when using aluminum hydroxide Al(OH)3, such that the addition of IOB core sand was increased to 10% starting from cycle 15 (Tables 19 and 20).

[0363] Table 19: Composition and compactness of the molding material mixture in each cycle

[0364]

[0365]

[0366] Table 20: Characteristic values of the samples taken in the respective cycles

[0367]

[0368]

[0369] The molding material analysis (Table 21) shows that carbon, nitrogen, or sulfur did not accumulate significantly in the molding material, and the C (carbon-containing) components from inorganic binders (such as surfactants) were minor. The low C load (carbon load) is one of the significant advantages of the inorganic molding material cycle because extremely low emissions can be expected (see below). Despite the low carbon content, the surface roughness obtained (Table 21) is still very close to the surface roughness of the tests with cold box core sand added (test series 2.2.1).

[0370] Table 21: CNS analysis of the selected cycles and surface roughness of the castings belonging thereto

[0371]

[0372] (1) The abbreviation NG means that the measured value is below the detection limit.

[0373] 2.3.2 Magnesium hydroxide Mg(OH)2 when adding inorganically bonded core sand in subsequent cycles

[0374] Magnesium hydroxide Mg(OH)₂ in the form of brucite in a 3 shape as an additive has shown after several cycles that the properties of the molded material cannot be stably maintained. Therefore, the bentonite content of the molded material was increased in cycles 8 and 15 (Table 22). Nevertheless, no stabilization of the characteristic values of the molded material was achieved. In particular, the wet tensile strength decreased with increasing number of cycles, and this trend could only be countered temporarily by adding additional fresh bentonite (Table 23).

[0375] That is, similar to adding cold box core sand (test series 2.2.2), no cycle of molded materials with stable molded material properties was obtained here either with Mg(OH)₂ as an additive, the water requirement of the mixture increased significantly, and other characteristic values of the molded material also showed instability (Table 23). The water requirement of the molded material corresponds to the water content of the molded material mixture in the state in the prescribed form (target degree of compaction). The active clay content and the wet tensile strength decreased significantly with increasing number of cycles. This could be compensated for by dosing bentonite, but overall there was no cycle of molded materials with stable molded material properties.

[0376] Table 22: Composition and degree of compaction of the molded material mixture in each cycle

[0377]

[0378] Table 23: Characteristic values of the samples taken in the corresponding cycles

[0379]

[0380]

[0381] Analysis of the selected molded material samples (Table 24) shows that for high numbers of cycles, the carbon content increased slightly, which may be caused by dosing bentonite; Ca bentonite was treated with carbonate during activation. The surface roughness of the castings was always acceptable, i.e., good to excellent.

[0382] Table 24: CNS analysis of the selected cycles and the surface roughness of the associated castings

[0383]

[0384] (1) The abbreviation NG means that the measured value is below the detection limit.

[0385] 2.4 Additive Al(OH)3 when adding new molding substrate in subsequent cycles (not according to the present invention)

[0386] In the case of using the sleeve model device described in ( https: / / www.researchdisclosure.com / database / RD705032 ), 11 cycles (0 - 10) are carried out, where in the first test, a 100% new H32 type molded substrate from Quartzwerke is used.

[0387] In all subsequent cycles 1 to 10, 3.7 kg of used molding material from the previous casting is used respectively, and it is refurbished with 185 g of molding substrate (new molding substrate) and 26 g of bentonite and 23 g of the corresponding additives (Table 25). Alteo's SH950 nuance - 00 is used as the additive aluminum hydroxide Al(OH)3. Stable molding material properties are achieved (Table 26).

[0388] In the case of using the new molding substrate as an additive (see Figure 2 , step (1)), good molding properties and good to excellent surface quality are achieved, which can be seen from the measured roughness of the casting. As expected, CNS analysis shows non - significant carbon and nitrogen contents after 11 cycles because only inorganic materials are used (see Table 27).

[0389] Table 25: Composition and compactness of the molding material mixture in each cycle

[0390]

[0391] Table 26: Characteristic values of the samples taken in the corresponding cycles

[0392]

[0393]

[0394] Table 27: CNS analysis of the selected cycles and surface roughness of the belonging castings

[0395]

[0396] (1) The abbreviation NG means that the measured value is below the detection limit.

[0397] 2.5 Al(OH)3 when adding cold box core sand in subsequent cycles

[0398] 11 cycles (0 - 10) are carried out in the case of using the sleeve model device described in (https: / / www.researchdisclosure.com / database / RD705032). The tests are carried out and the molding material properties and casting properties are measured as described in Chapter 2.4. However, in subsequent cycles, instead of a new molding substrate, a recycled second molding material manufactured by recycling uncast cores is added (seeFigure 2 , step (1)) (see Table 28 for the amount fraction of the molded material produced), and the core is made using a cold box binder ("cold box core sand"). Stable molded material properties are achieved (Table 29).

[0399] Table 28: Composition and compaction of the molded material mixture in each cycle

[0400]

[0401] Table 29: Eigenvalues of the samples taken in the respective cycles

[0402]

[0403]

[0404] Data from the CNS analysis of the molded material after 11 cycles shows that the carbon and nitrogen fractions from the addition of cold box core sand are significant, especially compared to the test series with the addition of new sand (Table 30).

[0405] Table 30: CNS analysis of the selected cycles and surface roughness of the castings belonging thereto

[0406]

[0407] (1) The abbreviation NG means that the measured value is below the detection limit.

[0408] 2.6 Al(OH)3 when adding inorganically bonded core sand in subsequent cycles (not according to the present invention)

[0409] 11 cycles (0 - 10) are carried out using the sleeve model device described in (https: / / www.researchdisclosure.com / database / RD705032). The tests are carried out and the molded material properties and casting properties are measured as described in Chapter 2.4. However, in subsequent cycles, instead of a new molded substrate, a recycled second molded material produced by recycling uncast cores is added (see Figure 2 , step (1)) (see Table 31 for the amount fraction of the molded material produced), and the core is made using an inorganic binder (sodium silicate) ("IOB core sand"). Thus, this is an inorganic molded material cycle for all binders used. Stable molded material properties are achieved (Table 32).

[0410] Table 31: Composition and compaction of the molded material mixture in each cycle

[0411]

[0412] Table 32: Eigenvalues of the samples taken in the corresponding cycles

[0413]

[0414]

[0415] The analysis of the molding material (Table 33) shows that carbon, nitrogen, or sulfur does not accumulate significantly in the molding material, and the C (carbon-containing) components from the inorganic binder (such as surfactants) are minor. The low C load (carbon load) is one of the major advantages of the inorganic molding material cycle because only very low emissions are expected (see below). Despite the low carbon content, the resulting surface roughness (Table 33) is still comparable to that of the tests with the addition of Coldbox core sand (test series 2.5).

[0416] Table 33: CNS analysis of the selected cycles and the surface roughness of the castings concerned

[0417]

[0418] (1) The abbreviation NG indicates that the measured value is below the detection limit.

[0419] 3. Molding material cycle with gradually decreasing carbon content in the molding material

[0420] The test has the following objectives: casting and regenerating a specific amount of recycled molding material multiple times, especially as the carbon content in the molding material gradually decreases. As is common in industrial casting, the molding material is led in a cycle here. An additive is introduced each time the molding material is regenerated, and the additive accumulates with each cycle. The components that are present in the starting molding material and are no longer added decrease, i.e., the share of the components that are no longer added in subsequent cycles decreases. The total amount of the molding material is constant and is approximately 1200 kg. Four molds are manufactured and cast per cycle according to the fin model device as described in (http: / ww, reschdeotsue, com / DataBase / RD 705032).

[0421] For the illustration of the test execution, refer to Figure 4 the molding material cycle therein.

[0422] The cycles of the molding material cycle include the following steps:

[0423] Manufacture of molding materials (step (1), first cycle)

[0424] 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)

[0425] The recycled molding material is conveyed from the BigBag to the silo in front of an Eirich mixer (Eirich intensive mixer R09 with a capacity of 150 liters and a maximum of 240 kg, operating batchwise at normal pressure) by means of a BigBag unloading station and two conveyor belts. The previously weighed additives (additive materials), bentonite, molding base materials or core molding materials, and additives are placed on the silo discharge belt. SH950 type Al(OH)3 (SH950 nunce - 00, Alteo) is used as an additive.

[0426] The additive is conveyed during each production (step (1), see Figure 4 ), and the additive accumulates with each cycle. By removing a portion of the cast molding material in step (5) or step (1) of the next cycle (see Figure 4 ), the share of the components present in the starting molding material and no longer added is reduced.

[0427] The molding material is removed from the silo and transported together with the additive material to the mixer. The mixing process starts, water is automatically metered, and after the mixing process is completed, the produced molding material is emptied from the mixer into a transport container. The transport container is transported to the molding equipment.

[0428] Depending on the water content of the mixture, the mixer program is selected between a mixing process without intermediate pause (Table 35) and a mixing process with intermediate pause (Table 34), and the desired compaction rate is set to 40% + / - 5% by controlling the water content. The desired compaction rate is set by controlling the degree of compaction. The degree of compaction changes with the water content of the molding material. The water content of each mixture is determined. Since the water addition required to achieve the target degree of compaction is not known, the required amount of water can be more easily determined by means of an intermediate pause in the mixing process, and subsequent mixtures are produced without intermediate pause.

[0429] Table 34: Mixing process with intermediate pause

[0430]

[0431]

[0432] Table 35: Mixing process without intermediate pause

[0433]

[0434] Manufacture of molds (step (2) in all cycles)

[0435] For this purpose, first, a partial volume of the lower mold box is filled with a sieved layer of molding material from the transport container; so much molding material is sieved that the contour of the fin model is no longer visible (this corresponds to a height of 80 mm in the lower mold box and 50 mm in the upper mold box). Subsequently, the remaining volume of the lower mold box is filled with unsieved molding material. The sieve has a net sieve hole size of 2 mm.

[0436] The lower mold box (i.e., the molding material in the lower mold box) is compacted in a molding device HWS HSP-1D with the given parameters (Table 36, mold box size 700×500×200 / 200 mm, model plate size 650×450×30 mm) by means of a static pressure (Seiatsu) air flow molding method. The time for guiding the air flow through the molding material in the mold box to fluidize the molding material is called the static pressure time. The static pressure time can be set independently for the upper and lower mold boxes. Subsequently, the molding material is pressed.

[0437] Table 36: Compaction parameters

[0438]

[0439]

[0440] The lower mold box is removed horizontally by hand and transported to the clamping station (Zulegestation) by means of a crane. The upper mold box is filled, compacted, removed, and transported in the same way. The previously manufactured (step (1a), see Figure 4 ) core is placed in the lower mold box (step (2a), see Figure 4 ). The mold is closed, clamped, and transported to the casting station.

[0441] Casting (step (3) in all cycles)

[0442] The mold is cast with the liquid metal of alloy GJL 250 at 1450 °C by means of a pouring ladle in a carrier iron with a single-sided shearing machine.

[0443] Manufacture (steps (2), (2a)) and cast the next batch of molds.

[0444] The cast mold is left to stand for 4 hours until separation. The casting cools here and the molding material heats up.

[0445] Separation (step (4) in all cycles)

[0446] The upper and lower mold boxes are opened. The casting and the cast molding material are separated. In the three molding material cycles studied, the core sand is treated in different ways:

[0447] 1. In test series A of the molding substrate where new sand is used as a measured addition, cores bonded with sodium silicate hardened by means of CO2 (see point 0.2 above) are used. The cores do not decompose upon separation and are completely removed at that point in the cycle.

[0448] 2. In test series B using cold box cores, the cores decompose completely in the center and can no longer be separated from the molding material. The core heads do not decompose and cannot be simply crushed either. Therefore, the core heads are removed at that point in the cycle.

[0449] 3. In test series C using inorganically bonded cores (binder Cordis 9477 / Anorgit 9476, see point 0.2), the cores decompose only in the edge layer, but cannot be very easily crushed by hand. Therefore, the IOB core sand is not removed.

[0450] Regeneration (step (5) in all cycles)

[0451] The molding material is spread on the ground and the molding material blocks are crushed with a shovel. The metal residues are removed. The molding material is left stationary on the workshop floor for at least 3 hours to cool. After cooling, the molding material is filled back into the big bags with a shovel.

[0452] Manufacture of molding materials (step (1) in the second cycle and each subsequent cycle)

[0453] New molding material is produced by adding bentonite, water, additives (as defined above) and a new molding substrate (new sand, test series A) or by regenerating the cores to produce a regenerated second molding material (test series B and C, details see below), and renovating the regenerated molding material from the previous cycle (regenerated first molding material). See the description of step (1) of the first cycle above for the process flow of the mixing process.

[0454] Adjust the increase in the amount of molding material caused by the addition in the mixer, i.e., the increase in the amount of molding material caused by the addition defined above, by taking out the same amount of the completely mixed molding material in each cycle.

[0455] The additives are conveyed each time the molding material is produced (step (1)), and the additives accumulate with each cycle. By removing a part of the cast molding material, the share of the components present in the starting molding material and not added in subsequent cycles is reduced.

[0456] 3.1 Test series for adding new molding substrate (new sand) in step (1) (test series A, not according to the present invention) invention

[0457] When manufacturing the mold (see step (2) above), a core bonded with sodium silicate is used, which does not decompose after casting (see point 0.2 above) and is removed in step (4) as described above.

[0458] In a test series with 30 cycles (A1 - A30, see Table 37), in each successive cycle, the recycled molding material (recycled first molding material) from the previous cycle is refurbished with a molding substrate of type Grudzen Laz.0.20 / 0.315 / 0.40 from Quartzwerke GmbH (coarse quartz sand of class 1K).

[0459] Table 37: Composition and compactness of the molding material mixture in each cycle

[0460]

[0461]

[0462] (1) "Recycled first molding material" hereby refers to the amount of molding material that is reused after recycling from the respective previous cycle.

[0463] (2) Dosage of water added

[0464] (3) Measured water content of the mixture

[0465] Table 38: Eigenvalues of the samples taken in the respective cycles to determine the molding material properties

[0466]

[0467]

[0468] Table 39: Analysis of the samples from each cycle

[0469]

[0470]

[0471] As expected, it can be observed that the ignition loss of the samples gradually decreases because with the increase in the number of cycles, there is less organic material in the molding material. This also shows that the contents of carbon, nitrogen, and sulfur gradually decrease (Table 39). Here, the molding material properties basically remain unchanged (Table 38).

[0472] Despite the decrease in the carbon fraction, no casting defects are observed, and the surface roughness of the castings does not change significantly due to the decrease in the carbon fraction (Table 40).

[0473] Table 40: Surface roughness of the castings manufactured during the test series A

[0474]

[0475] 3.2 Test series for adding organically bonded core sand (test series B)

[0476] When manufacturing the mold (see step (2) above), place the cold-box core (see point 0.2 above). The cold-box core decomposes completely in the center and can no longer be separated from the molding material.

[0477] In the test series with 30 cycles (B1 - B30, see Table 41), based on the above-mentioned starting molding material regenerated from the brake disc foundry, add the regenerated second molding material manufactured from the regenerated core (see Figure 4 ), where the core is made with a cold-box binder; that is, in each successive cycle, the regenerated molding material (regenerated first molding material) from the previous cycle is refurbished with the regenerated second molding material manufactured from the core made with a cold-box binder by regeneration.

[0478] Table 41: Composition and Compaction Degree of the Molding Material Mixture in Each Cycle

[0479]

[0480] (1) "Regenerated first molding material" here means the amount of molding material reused after regeneration from the respective previous cycle,

[0481] (2) The dosage of water is added

[0482] (3) The measured water content of the mixture

[0483] Table 42: Characteristic Values for Determining the Molding Material Properties of the Samples Taken in the Respective Cycles

[0484]

[0485]

[0486] Table 43: Analysis of the Molding Material Samples from the Selected Cycles

[0487]

[0488] The molding material analysis (Table 43) shows that the ignition loss of the molding material decreases with the progress of the number of cycles. At the same time, the contents of carbon (C), sulfur, and nitrogen (N) decrease, where the C and N contents approach the limit values determined by adding cold-box-bonded core sand. Here, the molding material properties basically remain unchanged (Table 42).

[0489] In the series of tests, the surface roughness of the castings was also determined (Table 44). It was observed that despite the reduced share of carbon in the molding material, a good surface was obtained. No casting defects were observed.

[0490] Table 44: Surface roughness of the castings produced during experimental series B

[0491]

[0492] 3.3 Test series for adding inorganically bonded core sand (test series C, not according to the present invention)

[0493] When manufacturing the mold (see step (2) above), an inorganic-bonded core was used (binder Cordis 9477 / Anorgit 9476, see point 0.2 above), and the inorganic-bonded core decomposed only in the edge layer but could not be easily crushed by hand.

[0494] In the series of tests with 30 cycles (C1 - C30, see Table 45), a regenerated second molding material produced from regenerated cores was added to the above-mentioned regenerated starting molding material from the brake disc foundry (point 0.2) (see Figure 4 ), and the cores were produced with a sodium silicate binder (Anorgit / Cordis system); that is, in each successive cycle, the regenerated molding material from the previous cycle (regenerated first molding material) was refurbished with a regenerated second molding material produced from regenerated cores produced with a sodium silicate binder (Anorgit / Cordis system).

[0495] Table 45: Composition and degree of compaction of the molding material mixture in each cycle

[0496]

[0497]

[0498] (1) "Regenerated first molding material" here means the amount of molding material that was reused after regeneration from the respective previous cycle

[0499] (2) Addition of the metered amount of water

[0500] (3) Measured water content of the mixture

[0501] Table 46: Characteristic values of the samples taken in the respective cycles to determine the properties of the molding material

[0502]

[0503]

[0504] Table 47: Analysis of Samples from the Selected Cycles

[0505]

[0506] The tests clearly show that as the moulding material is replaced more and more, the ignition loss and the contents of carbon, nitrogen and sulphur decrease gradually (Table 47). Here, the characteristics of the moulding material remain essentially unchanged (Table 46).

[0507] Despite the decreasing share of carbon, no casting defects were observed and the surface roughness of the castings did not change due to the decreasing carbon share (Table 48).

[0508] Table 48: Surface Roughness of the Castings Produced during the Test Series

[0509]

[0510] 3.4 Landfill Classification of the Recycled Moulding Material

[0511] From all three test series, the recycled moulding 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 moulding material (Table 49, the abbreviation NG means that the measured value is below the detection limit). Here, the following was determined:

[0512] According to the German landfill and long-term storage regulations of 4 July 2020 (landfill regulations), the starting recycled moulding material (starting sand) is associated with landfill class II due to its ignition loss, TOC value (Total Organic Carbon) and its phenol coefficient. The recycled moulding material of test series B only has a TOC value that is slightly too high for classification into landfill class I and should thus be associated with landfill class II, but the TOC value can be further reduced due to the progress of the replacement or the use of another cold-box binder.

[0513] The recycled materials in test series A and C belong to landfill class I.

[0514] Table 49 (the abbreviation NG means that the measured value is below the detection limit)

[0515]

[0516]

[0517] 1. Determined in accordance with DIN EN 14346:2007-03

[0518] 2. Determined in accordance with DIN EN 15169:2007-05

[0519] 3. Determined in accordance with DIN EN 15936:2012-11 (AN, L8: Edition A; FG, F5: Edition B)

[0520] 4. Determined in accordance with the notification of the National Working Group on Waste Issues ( Abfall), Notification No. 35, Abbreviation: KW / 04:2019-09

[0521] 5. Determined in accordance with DIN EN ISO 10523 (C5):2012-04

[0522] 6. Determined in accordance with DIN EN 15216:2008-01

[0523] 7. Determined in accordance with DIN EN ISO 10304-1 (D20):2009-07 (D20)

[0524] 8. Determined in accordance with DIN EN ISO 14403-2:2012-10

[0525] 9. Determined in accordance with DIN EN ISO 17294-2 (E29):2017-01 (E29)

[0526] 10. Determined in accordance with DIN EN ISO 12846 (E12):2012-08

[0527] 11. Determined in accordance with DIN EN 1484:2019-04

[0528] 12. Determined in accordance with DIN EN ISO 14402 (H37):1999-12

[0529] 3.5 BTX emission potential of the regenerated molding material

[0530] The starting molding materials of the conditioned molding material cycle from the brake disc foundry and the molding materials from cycles A-30, B-30, and C-30 were studied for their BTX emission potential. For this purpose, after drying at 105 °C, the samples were ground in a planetary ball mill (Retsch Planetary Ball Mill PM100CM) under cold conditions at 300 revolutions per minute for 2 minutes (container: 150 ml stainless steel cup with stainless steel balls). They were cooled 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 to avoid overheating of the samples during the grinding process. Subsequently, 10 mg of the sample was weighed into a pyrolysis tube. Double determination was performed for each sample. The measurements were carried out using the following instruments:

[0531] ·GERSTEL MPS

[0532] ·GERSTEL TDU 2 with pyrolysis module

[0533] ·Agilent 8890B gas chromatograph and Agilent 5977 mass spectrometer

[0534] ·RESTEK 13868RXI-624Sil MS capillary column, -60 °C - 300 °C (320 °C): 30 m × 250 μm × 1.4 0.25 mm

[0535] ·150 ml stainless steel mortar and stainless steel grinding balls

[0536] ·Hamilton electronic holder (VWR part number HAMIDS86200)

[0537] ·Hamilton 1 μL syringe (VWR part number 549-1224)

[0538] ·Carbotrap B packed Glass Inlet Liner (temperature limit 450 °C) (Gerstel part number 013248-005-00)

[0539] ·Quartz pyrolysis tube (Gerstel part number 018437-020-00)

[0540] ·Adsorbent matrix Carbopack TM B, 60 - 80 mesh (VWR part number SUPL20273)

[0541] ·Silanized glass wool (VWR part number SERA22367.01)

[0542] Subject to the following conditions:

[0543] Gas chromatography (GC) parameters

[0544]

[0545]

[0546] KAS parameters

[0547] (KAS = cold feed system - the sample is pyrolyzed, the pyrolysis gas is condensed and then volatilized for GC measurement

[0548]

[0549] Calibration method:

[0550] MSD parameters (MSD = mass spectrometry detector)

[0551]

[0552] TDU parameters (TDU = thermal desorption unit)

[0553]

[0554] Pyrolysis parameters

[0555]

[0556]

[0557] Calibrated based on the standards of benzene, toluene, m - xylene and p - xylene, styrene, o - xylene, ethylbenzene, cumene.

[0558] Specimen method:

[0559] MSD parameters

[0560]

[0561] TDU parameters

[0562]

[0563] Pyrolysis parameters

[0564]

[0565] Characteristic values of the method

[0566]

[0567]

[0568] Evaluated by means of the software MassHunter.

[0569] The results shown in Table 50 clearly show that the use of the additive according to the invention can significantly reduce the emissions of harmful substances. Especially when combined with inorganic cores or when adding new molding substrates (new sand) to the molding material cycle, the emission potential is significantly reduced. A significant effect is also observed when adding cold - box core sand. The emission potential is reduced by more than 45% in the model case.

[0570] Table 50: Comparison of pyrolysis (GC - MS) of molding materials after 30 cycles with the starting molding materials (all descriptions are in mg emissions / kg sample material)

[0571]

[0572] In Table 50, the indication “<…” means that the content of the corresponding BTEX compound is below its detection limit.

[0573] This applies to the value range for the line “BTEX in 900 °C”:

[0574] The lower limit value corresponds to the sum of the contents of the BTEX compounds that are above the respective detection limits, such that it is possible to determine the values (in the case of the starting moulding material, these are benzene, toluene, styrene and m-xylene, p-xylene).

[0575] The upper limit value corresponds to the sum of the lower limit value and the detection limit of each BTEX compound whose content is below the respective detection limit (in the case of the starting moulding material, these are o-xylene, styrene and cumene).

Claims

1. A method for guiding molding material in a molding material cycle comprising two or more cycles, having the following steps: - In an earlier cycle of the two or more cycles of the molding material cycle, casting is carried out in a mold comprising molding material bonded with montmorillonite-containing clay, wherein the cast molding material is obtained, - The cast molding material is regenerated such that a regenerated first molding material is obtained, - In a later cycle of the two or more cycles of the molding material cycle, molding material is manufactured, the molding material comprising (i) the regenerated first molding material, and (ii) additives, the additives comprising: - one or more raw materials from the following group: - molding substrates, - regenerated second molding material, which is manufactured by regenerating molding material from an uncast mold and / or core and / or parts thereof, - regenerated third molding material, which is manufactured by regenerating molding material from a mold and / or core and / or parts thereof cast outside the molding material cycle, - additives, the additives containing at least one dehydratable inorganic compound, the dehydratable inorganic compound separating out water at a temperature of 150 °C or higher, - and optionally, montmorillonite-containing clay, wherein at least one of the regenerated molding materials in the regenerated molding material contains an organic binder and / or its reaction product, wherein the molding material manufactured in the later cycle contains carbon, wherein at least 70% by weight of the carbon is derived from the organic binder and the reaction product.

2. The method according to claim 1, wherein casting is carried out in a mold having at least one inserted core, the core being manufactured by an organic binder, wherein the cast molding material is obtained, the molding material comprising material from the cast mold and material from the cast core.

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

4. The method according to any one of the above claims, wherein the additive comprises one compound from the group consisting of aluminum hydroxide and magnesium hydroxide or both of these compounds, wherein preferably, based on the total mass of aluminum hydroxide and magnesium hydroxide in the additive, the share of aluminum hydroxide is at least 80%, preferably at least 90%, more preferably at least 95% and particularly preferably 99%.

5. The method according to any one of the above claims, wherein the mold is cast with iron.

6. The method according to any one of the above claims, wherein the molding material manufactured in the later cycle has one or more of the following parameters: - a carbon concentration of less than 4%, preferably less than 3%, by mass of the molding material, determined by elemental analysis, - a nitrogen concentration of less than 0.2%, preferably less than 0.1%, by mass of the molding material, determined by elemental analysis, - a sulfur concentration of less than 0.05%, preferably less than 0.03%, by mass of the molding material, determined by elemental analysis, - A burning loss of at most 5%, preferably at most 4%, determined according to VDG operating specification P33 (April 1997).

7. The method according to any one of claims 1 to 6, wherein the moulding material produced in the later cycle contains carbon, at least 80% by weight, preferably at least 90% by weight and particularly preferably at least 95% by weight of which is derived from the organic binder and the reaction product.

8. Use of an additive as claimed in claim 1 in a method according to any one of claims 1 to 7.

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