Method for reducing carbon-based emissions and / or carbon-based casting defects during molded material cycling comprising two or morted material cycling comprising

Abstract

A method for reducing carbon-based emissions and / or carbon-based casting defects during molding material cycles comprising two or more cycles of molding material containing smectite clay is described.

Description

Technical Field

[0001] The present invention relates to a method for reducing carbon-based emissions and / or carbon-based casting defects during a molding material cycle comprising two or more cycles of a molding material containing smectite clay. Background Art

[0002] Clays used 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, saponite, nontronite, beidellite, or zinc saponite. 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, it can be increased by purification. This applies in particular to bentonite.

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

[0005] Correspondingly, in the present context, the terms "smectite-containing clay" and "bentonite" are used not only for the corresponding clays obtained from natural occurrences, but also for clays produced by purifying naturally occurring clays.

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

[0007] Any sand that can be used as a molding substrate for casting molds and that can maintain its shape at high temperatures and in contact with hot metal can be used. Typical sands are silica sand, olivine sand, chromite sand, zircon sand, and artificial ceramic sand, or mixtures of these sands. The mold usually contains at least 40% sand, preferably more than 50% sand, particularly preferably more than 60% sand, and most particularly preferably more than 70% sand.

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

[0009] In industrial practice, molding materials containing montmorillonite clay are commonly used as binders in the molding material cycle.

[0010] The molding material cycle in the sense of the present disclosure means that the molding material is regenerated from the cast mold ("cast molding material", also known as used sand) and is used to manufacture new molding material, and the cast mold is remanufactured 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 sense 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, 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 and additives (see below) in the earlier cycle

[0014] (Step 2) Manufacture of the mold, i.e., manufacture of the mold bonded with montmorillonite clay from the molding material manufactured in step (1).

[0015] (Step 3) Casting, i.e., manufacture of the casting by casting the mold manufactured in step (2).

[0016] (Step 4) Separation, i.e., separation of the casting manufactured in step (3) from the mold, wherein the cast molding material is obtained, and the cast molding material includes the material from the cast mold.

[0017] (Step 5) Regeneration of the cast molding material, i.e., regeneration of the cast molding material in step (4) such that the first regenerated molding material is obtained for manufacturing new molding material in step (1) of the later cycle.

[0018] In certain cases, it is preferred that one, more or all cycles of the molding material cycle include other steps, and / or each of the steps has other features. Details regarding this are derived from the following description, the appended claims and the drawings.

[0019] In each cycle of the above-mentioned molding material cycle, castings are produced in step (3) by casting the mold produced in step (2). Here, when casting (step (3) of the cycle), the molding material undergoes significant changes in terms of material due to thermal stress and chemical stress. In order to enable the recycling of the molding material, the cast molding material must be regenerated.

[0020] In some cases, especially for producing castings with complex geometries, in step (3) the casting is produced by casting a mold produced in step (2) with one or more inserted cores (see Figure 3 ). Cores inserted into the clay-bonded mold are usually not clay-bonded. Such cores are usually produced with the aid of organic binders, such as polyurethanes or phenolic resins, or with the aid of inorganic binders without clay, such as binders 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).

[0021] Regenerating 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.

[0022] 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 in the casting process (core heads, riser residues (Speiserreste), etc.).

[0023] Wear products are generated by thermal stress, mechanical stress and possibly also chemical stress during casting, such as fine sand fractions, inactive clay fractions, decomposition products of additives (especially bright carbon formers), reaction products of core binders, and ooliths of the molding substrate.

[0024] In order that such wear products do not accumulate in the molding material cycle and / or do not have an adverse effect on the molding material properties, or in order that the required active fractions of the binder (containing montmorillonite clay) and the additives do not decrease too strongly, additives are added in step (1) during the production of the molding material in the corresponding subsequent cycles, i.e., the regenerated molding material is refreshed 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 refreshment by the additives (i.e., in step (5)), or after the refreshment by the additives.

[0025] The additive usually includes montmorillonite clay-containing, water, additives (see below) and one or more raw materials from the following groups:

[0026] - New molding substrate (new sand),

[0027] - Recycled second molding material, which is manufactured by recycling uncast molds and / or cores and / or parts thereof,

[0028] - Recycled third molding material, which is manufactured by recycling molds and / or cores and / or parts thereof that are manufactured outside the observed molding material cycle and cast.

[0029] The additive (especially bentonite) preferably also includes water.

[0030] The molds and cores from which the recycled second and third molding materials as defined above are obtained must not be clay-bonded. In particular, the cores are usually not clay-bonded, but are manufactured with common organic binders, such as polyurethanes, especially polyurethanes formed in the cold box process, or phenol resins in the form of novolacs, especially novolacs suitable for hot box or warm box methods, or phenolic varnishes, especially phenolic varnishes used in the Croning process or shell molding process.

[0031] In each cycle of the industrial molding material cycle, a substantially constant casting quality should be achieved during casting. By regulating the introduction and export of the components of the molding material, substantially constant and optimal molding material properties (molding material regulation) can be achieved in the molding material cycle. Here, in each cycle, the addition rates of montmorillonite clay (selective addition), additives, water, and new sand or the recycled second and third molding materials as defined above are determined, and the amount of old sand to be exported is determined, and the molding material is adjusted, i.e., optimally set, by determining machine parameters such as mixing time or cooling intensity.

[0032] The molding material for manufacturing clay-bonded molds usually contains additives in the form of so-called bright carbon formers in industrial practice.

[0033] Bright carbon formers (also called bright carbon carriers See https: / / www.giesserei-praxis.de / giesserei-lexikon / glossar / glanzkohlenstoff) are molding material additives capable of forming hydrocarbon-containing gases, and the molding material additives are coked in the reducing atmosphere of the cavity during casting. Here, bright carbon is produced. Commonly used bright carbon formers are, for example, coal dust, wood tar (Peche), bitumen (Bitumina), resins, oils, plastics and their mixtures.

[0034] In particular, a bright carbon former is added to the clay-bonded molding material for cast iron. The 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, the increased share of coal dust or other bright carbon formers and the higher share of decomposition products (coke) of the bright carbon former in the recycled molding material increase the water requirement of the molding material. The increased water content in the molding material can lead to casting defects, such as blowhole penetration.

[0035] 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 compensated regularly by introducing 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.

[0036] An important disadvantage of using bright carbon formers is the release of emissions in the form of, for example, 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 the high risk of dust explosion and spontaneous combustion when handling bright carbon formers. Therefore, in industrial casting operations, when manufacturing clay-bonded molds, bright carbon formers are used in the form of a mixture prefabricated by the supplier with smectite clay, especially bentonite.

[0037] For the reasons stated, it is desirable and necessary to limit the use of bright carbon formers or to replace the bright carbon formers at least in a significant share by suitable alternatives.

[0038] US 5,372,636 A discloses a molding material that includes sand, sodium smectite 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 the cycle is not disclosed. Therefore, this document does not provide information on whether this molding material is suitable for the molding material cycle.

[0039] WO 03 / 066253 A1 describes a method for manufacturing a molding material, especially for use in a cycle and for casting purposes, according to which a material that does not swell in water is added to a mixture consisting of particulate matter and additives such as binders (e.g., bentonite) and water. In particular, framework silicates or network silicates such as zeolites, pumice or volcanic rock, allophane, imogolite, diatomaceous earth (Kieselgur), hydrotalcite, sepiolite, diatomaceous earth (Diatomenerde) or (acid- and / or heat-treated) clay are used as non-swelling porous materials.

[0040] CN 108356214 discloses a molding material mixture comprising sand, water, bentonite and an additive comprising the following components

[0041] SiO2 50 - 85 wt%

[0042] Al2O3 9 - 45 wt%

[0043] MgO 0.2 - 3 wt%

[0044] Fe2O3 1 - 8 wt%

[0045] CaO 1 - 7 wt%

[0046] Fe3O4 0.4 - 8 wt%

[0047] The additive is manufactured by mixing the individual oxides. The additive is supposed to replace bright carbon formers. The molding material containing the additive should be easy to recycle. Exemplary molding materials have been used for more than two to four months. Summary of the Invention

[0048] 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"), and polycyclic aromatic hydrocarbons.

[0049] This object is achieved by a method for reducing carbon-based emissions and / or carbon-based casting defects during a molding material cycle comprising two or more cycles, which contains a molding material containing smectite clay, wherein the method comprises:

[0050] - reducing the carbon content in the molding material such that the molding material produced in a later cycle has a lower carbon content compared to the molding material produced in an earlier cycle,

[0051] and

[0052] -Introduce the additive in one or more later cycles of the two or more cycles of the molding material cycle, the additive containing at least one dehydratable inorganic compound that separates water at a temperature of 150 °C or higher.

[0053] The method according to the invention can achieve a reduction in carbon-based emissions and / or carbon-based casting defects during the molding material cycle of a molding material containing montmorillonite clay that includes two or more cycles, i.e., during continuous operation, without interrupting the molding material cycle and / or immediately significantly changing the formulation of the molding material. Instead, the method according to the invention allows for a gradual reduction in the carbon content in the molding material during continuous operation under the condition of continuously using the existing facilities. Thus, a production line using a molding material containing a conventional bright carbon former can be gradually converted to use a molding material with a significantly reduced carbon content.

[0054] Therefore, the method according to the invention achieves the purpose of converting an existing stable (first) molding material cycle system into another (second) molding material cycle system, the other (second) molding material cycle system being characterized by reduced carbon-based emissions and / or reduced carbon-based casting defects. Here, stable means that within the first and second molding material cycle systems, the molding material guided in the cycle always has the characteristic features required for the corresponding application situation, including acceptable deviations for the application situation. Parameters important for the characteristic features are in particular the compactness, wet compressive strength, wet tensile strength, air permeability, active clay content, and fluidity of the molding material.

[0055] The method according to the invention (as defined above and in claim 1) includes operating measures for achieving the said purpose. The earlier cycles mentioned above are part of the stable first molding material cycle system, and the later cycles mentioned above are part of the stable second molding material cycle system.

[0056] According to the invention, it is not required that the carbon content in each molding material produced in the later cycle is less than the carbon content in each molding material produced in the earlier cycle. What is decisive is that the carbon content in the molding material is reduced such that during the molding material cycle including two or more cycles, the carbon-based emissions are reduced from the earlier cycle to the later cycle of the molding material cycle.

[0057] The molding material cycle related to 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 integrated into the molding material cycle and optionally having at least another production line for manufacturing and / or casting molds and / or cores that are not clay-bonded.

[0058] It is not mandatory to add the additives as defined above in each cycle of the molding material cycle. The molding material cycle according to the invention may include cycles in which the additives are not added.

[0059] 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.

[0060] The carbon content of the molding material is determined by elemental analysis and includes the carbon fractions from the organic carbon carriers and from the inorganic carbon carriers. The organic carbon carriers are in particular bright carbon formers, organic binders, organic additives and residues or decomposition products of bright carbon formers, organic binders and organic additives. The inorganic carbon carriers are in particular carbonates that may be contained in the molding material.

[0061] In a molding material with smectite clay as binder, the carbon content can be reduced in particular by reducing or avoiding the use of bright carbon formers.

[0062] By reducing or even avoiding the use of bright carbon formers, fossil resources are conserved. Another object achieved by the invention is therefore to provide a resource-saving molding material cycle.

[0063] By reducing or even avoiding the use of bright carbon formers, the risk of dust explosion and spontaneous combustion during the transport, storage and handling of bright carbon formers is reduced or even eliminated. Another object achieved by the invention is therefore to reduce the risk of dust explosion and spontaneous combustion during the transport, storage and handling of bright carbon formers.

[0064] By reducing or even avoiding the use of bright carbon formers, fewer pyrolysis products are produced during casting that would contaminate the cast molding material or the molding material removed from the molding material cycle. The lower carbon and sulfur content in the cast molding material with the reduction in the use of bright carbon formers is also beneficial for the landfill of the non-reusable molding material fraction. Another object achieved by the invention is therefore to simplify the reuse or landfill of the cast molding material.

[0065] Other objects achieved by the invention are therefore to reduce sulfur-based emissions and NOx emissions during a molding material cycle comprising two or more cycles.

[0066] The object of reducing sulfur-based emissions is achieved by a method as defined above, which further comprises

[0067] - reducing the sulfur content in the molding material such that the molding material produced in a later cycle has a lower sulfur content than the molding material produced in an earlier cycle.

[0068] The present invention does not require that the sulfur content in each molded material manufactured in a later cycle be less than the sulfur content in each molded material manufactured in an earlier cycle. What is decisive is that the sulfur content in the molded material is reduced such that during a molded material cycle comprising two or more cycles, sulfur-based emissions are reduced from an earlier cycle to a later cycle of the molded material cycle.

[0069] Another object achieved by the present invention is to reduce the odor pollution released during casting.

[0070] The reduction of the bright carbon fraction should not cause an unacceptable impairment of the properties of the molded material, the mold cast from the molded material, and the castings made thereby.

[0071] The solution to the object 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 avoiding mold expansion defects, separation between the metal and the molded material, and promoting mold decomposition. It has surprisingly been found that dehydratable inorganic compounds which release 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 avoiding mold expansion defects and promoting mold decomposition.

[0072] Dehydration means the separation of chemically (e.g. in the form of hydroxide ions) or physically (e.g. as water of crystallization in a hydrate) bound water by heating.

[0073] The dehydratable inorganic compounds contained in the additives to be used according to the present invention preferably relate to compounds from the group of hydroxides and hydrated salts of metals. The term hydroxide as used herein also includes oxidhydroxides. Preferred are hydroxides and hydrated salts of metals in the +II or +III oxidation state, particularly preferably 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 preferably aluminum trihydroxide Al(OH)3. Here, aluminum trihydroxide can exist in different polymorphic forms, especially as gibbsite, bayerite or nordstrandite, and also in combination with other hydroxides or oxides in minerals.

[0074] The additives to be used according to the present invention preferably do not include carbon or carbon carriers.

[0075] A preferred embodiment of the method according to the present invention is a method having the following steps:

[0076] - In an earlier cycle of the two or more cycles of the molded material cycle, casting is carried out in a mold containing a molded material bonded with montmorillonite clay, wherein a cast molded material is obtained,

[0077] - Recycling the molded material cast in an earlier cycle, wherein the recycled molded material contains carbon, so as to obtain a first recycled molded material,

[0078] - In a later cycle of the two or more cycles of the molded material cycle, manufacturing a molded material, the molded material including

[0079] (i) The first recycled molded material as defined above,

[0080] and

[0081] (ii) Additives, the additives including

[0082] - Additives as defined above

[0083] - And one or more raw materials in the following group

[0084] - Molded base materials,

[0085] - A second recycled molded material, which is manufactured by recycling the molded material from an uncast mold and / or core and / or parts thereof,

[0086] - A third recycled molded material, which is manufactured by recycling a mold and / or core and / or parts thereof cast outside the molded material cycle,

[0087] - And optionally smectite clay, preferably bentonite,

[0088] wherein the molded material is manufactured such that it has a lower carbon concentration compared to the molded material manufactured in an earlier cycle.

[0089] In the preferred embodiment of the method according to the invention, in an earlier cycle of the two or more cycles of the molded material cycle, a mold bonded with smectite clay is cast, wherein a casting is produced. The cast molded material is obtained from the casting of the mold. The cast molded material is recycled in the above manner so as to obtain a first recycled molded material. In order to keep the quality of the molded material guided in the cycle constant, if necessary, a part of the cast molded material is removed during recycling, so as to obtain the molded material after removal.

[0090] However, it is not mandatory to remove the recycled molded material in each cycle of the molded material cycle. The molded material cycle according to the invention may include individual cycles in which the recycled molded material is not removed.

[0091] In a later cycle of the molded material cycle, manufacturing a molded material, the molded material including (i) the first recycled molded material as defined above, and (ii) additives. The additives include

[0092] - An additive as defined above

[0093] - And one or more raw materials from the following group

[0094] - A mold substrate, especially quartz sand

[0095] - A regenerated second molding material, which is manufactured by regenerating the molding material from uncast molds and / or cores and / or parts thereof,

[0096] - A regenerated third molding material, which is manufactured by regenerating the molding material from molds and / or cores and / or parts thereof cast outside the molding material cycle,

[0097] - And preferably smectite clay, preferably bentonite.

[0098] The additive preferably also includes water.

[0099] If a part of the cast molding material is not removed after regeneration, then in order to keep the quality of the molding material guided in the cycle constant, now a part of the manufactured molding material can be removed so that the molding material obtained is the one after removal. But this is not necessarily required. The molding material cycle according to the invention can include individual cycles in which no removal of the molding material is carried out.

[0100] The molding material manufactured in a later cycle of the molding material cycle includes one, more or all of the above raw materials. The mold 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 the above sands.

[0101] The smectite clay-containing material is preferably bentonite, especially bentonite from the group consisting of sodium bentonite, calcium bentonite and mixtures thereof.

[0102] The regenerated second molding material as defined above is manufactured by regenerating the molding material from uncast molds and / or cores and / or parts thereof. The uncast molds and / or cores refer to molds and / or cores that are not cast for various reasons, such as due to processing defects or insufficient dimensional accuracy.

[0103] The regenerated third molding material as defined above is manufactured by regenerating the molding material from molds and / or cores and / or parts thereof cast outside the observed molding material cycle, that is, for example, molds and cores cast in another production line.

[0104] The molds and cores for obtaining the regenerated second and third molding materials as defined above must not be clay-bonded. In particular, the cores are generally not clay-bonded. The regenerated second molding material is generally produced by regenerating molding material from uncast molds and / or cores and / or parts thereof, where the molds and cores are not clay-bonded. The regenerated third molding material is generally produced by regenerating molding material from cast molds and / or cores and / or parts thereof outside the molding material cycle, where the molds and cores are not clay-bonded. In such cases, the mold or core contains a common organic binder, such as phenolic resin or polyurethane formed by the cold box process, and / or reaction products thereof during casting; or an inorganic binder, such as a binder containing water glass, and / or reaction products thereof during casting.

[0105] The molding material is manufactured in a later cycle such that the manufactured molding material has a lower carbon concentration compared to the molding material in an earlier cycle. This is achieved in particular by adding less bright carbon former compared to the earlier cycle, preferably by omitting the addition of bright carbon former as much as possible or completely. This is achieved by using additives as defined above, which are similar in effect to the bright carbon formers used in the prior art in avoiding mold expansion defects and promoting mold decomposition. Here, the additive preferably comprises one or two compounds from the group consisting of aluminum hydroxide and magnesium hydroxide. Preferably, the molding material is manufactured in a later cycle such that the manufactured molding material has a higher total concentration of aluminum hydroxide and magnesium hydroxide compared to the regenerated first molding material in the earlier cycle.

[0106] The regenerated molding material (the regenerated first molding material as defined above) from an earlier cycle of the molding material cycle to which the method according to the invention is applied generally contains at least one bright carbon former and / or its carbon-containing reaction products during casting.

[0107] According to the invention, preferably no bright carbon is added for manufacturing the molding material in a later cycle. Alternatively, according to the invention, one or more bright carbon formers are added as other additives for manufacturing the molding material in a later cycle, where the total mass of carbon introduced by the bright carbon former is less than the total mass of carbon removed by emissions and molding material removal in the earlier cycle. Thus, the amount of bright carbon former input into the molding material in the later cycle is not sufficient to achieve the same high carbon concentration in the molding material manufactured in the later cycle as in the molding material manufactured in the earlier cycle.

[0108] Here, it is clear to those skilled in the art that omitting the addition of bright carbon former or reducing the input of bright carbon former does not allow over-compensation by excessively high input of organic binders and their reaction products via the first, second or third regenerated molding materials.

[0109] The method according to the invention is preferred, wherein the carbon content in the molding material gradually decreases over 2 cycles, preferably over at least 10 cycles, particularly preferably over at least 20 cycles.

[0110] If no new carbon is introduced over a plurality of cycles, the carbon concentration in the molding material decreases with each cycle, wherein the decrease in the carbon concentration slows down as the number of cycles increases, and the carbon concentration decreases asymptotically.

[0111] In one embodiment of the method according to the invention, in an earlier cycle, casting is carried out in a mold with at least one inserted core. Thus, the cast molding material obtained in an earlier cycle of the molding material cycle and the resulting recycled first molding material contain materials from at least one cast mold and at least one cast core cast in the same casting process. The material from the cast core contains reaction products of the binder formed during casting.

[0112] The cores inserted into the clay-bonded molds are generally not clay-bonded. Such cores are generally manufactured with an organic binder, such as a cold-box binder or a phenolic resin, or with a clay-free inorganic binder, such as a binder based on water glass.

[0113] In the said embodiment of the method according to the invention, recycled second molding materials containing materials from uncast molds and / or cores and / or parts thereof, and / or recycled third molding materials containing materials from cast molds and / or cores and / or parts thereof can be used, wherein the molds and cores can be manufactured with an organic binder, such as a cold-box binder or a phenolic resin, or with a clay-free inorganic binder, such as a binder based on water glass. Thus, in such cases, the molding materials manufactured in a later cycle of the molding material cycle contain core sand.

[0114] In the said embodiment of the method according to the invention, an additive containing aluminum hydroxide is preferably used, wherein the share of aluminum hydroxide is at least 80%, preferably at least 90%, particularly preferably at least 95%, and most particularly preferably 99% by the total mass of aluminum hydroxide and magnesium hydroxide in the additive.

[0115] If the molding material manufactured in a later cycle contains carbon, 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% of the carbon comes from the reaction products of the organic binders and binders of the cast and uncast cores.

[0116] 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 molded material does not contain material from the cast core.

[0117] The regenerated second molded material for the embodiment of the method according to the invention is preferably manufactured by regenerating only the molded material from the uncast clay-bonded mold and / or core and / or parts thereof. The regenerated third molded material for the embodiment of the method according to the invention is preferably manufactured by regenerating only the molded material from the clay-bonded mold and / or core and / or parts thereof cast outside the observed molded material cycle.

[0118] In the embodiment of the method according to the invention, an additive comprising one or two compounds from the group consisting of aluminum hydroxide and magnesium hydroxide is preferably used, wherein the share of magnesium hydroxide is 0 to 100% by the total mass of aluminum hydroxide and magnesium hydroxide in the additive.

[0119] In the method according to the invention, the molded material guided in the cycle is preferably used to manufacture a mold for cast iron.

[0120] 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):

[0121] (Step 1) Manufacturing a molded material, that is, manufacturing a molded material including the following

[0122] (i) The regenerated first molded material manufactured by regenerating the cast molded material obtained in an earlier cycle of the molded material cycle as defined above

[0123] And

[0124] (ii) The additive as defined above

[0125] (Step 2) Manufacturing a mold, that is, manufacturing a mold bonded with montmorillonite clay from the molded material manufactured in step (1)

[0126] (Step 3) Casting, that is, manufacturing a casting by casting the mold manufactured in step (2)

[0127] (Step 4) Separating, that is, separating the casting manufactured in step (3) from the mold, wherein the cast molded material is obtained

[0128] (Step 5) Recycling, that is, recycling the cast molded material in step (4) to obtain a recycled first molded material for manufacturing a new molded material in step (1) of a later cycle, and, if necessary, removing a part of the cast molded material to obtain a molded material from which the removal has been carried out.

[0129] If a part of the cast molded material is not removed during recycling in step (5), then, in order to keep the quality of the molded material guided in the cycle constant, a part of the molded material manufactured in step (1) of the next cycle is removed to obtain a molded material from which the removal has been carried out.

[0130] 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):

[0131] (Step 1) Manufacturing a molded material, that is, manufacturing a molded material including

[0132] (i) a recycled molded material manufactured by recycling the cast molded material obtained in an earlier cycle of the molded material cycle as defined above

[0133] and

[0134] (ii) an additive as defined above

[0135] (Step 1a) Manufacturing a core molded material, that is, manufacturing or providing a molded material for manufacturing at least one core

[0136] (Step 2) Manufacturing a mold, that is, manufacturing a mold bonded by montmorillonite clay from the molded material manufactured in step (1)

[0137] (Step 2a) Manufacturing a core, that is, manufacturing or providing at least one core and inserting the at least one core into the mold manufactured in step (2)

[0138] (Step 3) Casting, that is, manufacturing a casting by casting the mold manufactured in step (2) having at least one core inserted in step (2a)

[0139] (Step 4) Separating, that is, separating the casting manufactured in step (3) from the mold and at least one core, wherein a cast molded material is obtained, the molded material containing materials from the cast mold and the cast core

[0140] (Step 5) Recycling, i.e., recycling the cast molding material in step (4) to obtain a recycled first molding material for manufacturing a new molding material in step (1) of a later cycle, and, if necessary, removing a part of the cast molding material to obtain a molding material from which the removal has been carried out.

[0141] 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 is removed to obtain a molding material from which the removal has been carried out.

[0142] In certain cases, preferably, one, more than one or all cycles of the molding material cycle include other steps, and / or, individual steps in said steps have other features. Details regarding this are derived from the following description, the appended claims and the drawings.

[0143] Especially when manufacturing the molding material in step (1) of the molding material cycle, preferably the recycled molding material is mixed with additives. The additives preferably also include water.

[0144] Preferably, the mold having the casting and, if any, at least one core is cooled before separation in step (4).

[0145] Preferably, the cast molding material is cooled before recycling.

[0146] 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 crushing (particle separation) the cast molding material.

[0147] Wear products are generated by thermal, mechanical and possibly chemical loads, such as minute fractions of sand, non-reactive clay fractions, decomposition products of additives and / or bright carbon formers, or reaction products of core binders and oolites of the molding substrate.

[0148] In order that such wear products do not accumulate in the molding material cycle, and / or do not have an adverse effect on the molding material properties, and / or in order that the required active fraction of the binder (containing smectite clay) and the additives to be used according to the invention does not decrease too strongly, 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 renovated 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 renovation by the additive (i.e., in particular in step (5)), or after renovation by 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.

[0149] Thus, in some cases, step (5) includes, if necessary, removing the same amount of the cast molding material as that renovated by the additive including the additives to be used according to the invention in step (1) of the next cycle; it is feasible to achieve uniform characteristic features in this way.

[0150] Preferably, 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 (Sandaustrag)) is removed in step (5), and a corresponding amount of the additive is added in step (1) of the next cycle in order to keep the quality of the molding material guided in the cycle constant.

[0151] 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.

[0152] The molding material removed during regeneration in step (5) preferably meets the requirements of landfill class DKI in Annex 3 of the "Landfill and Long-Term Storage Regulations" (the "Landfill Regulations - DepV") of April 27, 2009.

[0153] 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.

[0154] Preferably, the additives defined above are added in each cycle of the molding material cycle.

[0155] 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 having a particle size of 20 μm to 200 μm as determined by a laser particle size analyzer.

[0156] Preferably, based on the total mass of the additive as defined above, the share of the dehydratable inorganic compound that separates out water at a temperature of 150 °C or higher is from 1% to 100%. Particularly preferably, based on the total mass of the additive as defined above, the share of the dehydratable inorganic compound that separates out water at a temperature of 150 °C or higher is from 20% to 100%. Most particularly preferably, based on the total mass of the additive as defined above, the share of the dehydratable inorganic compound that separates out water at a temperature of 150 °C or higher is from 30% to 100%. Especially preferably, based on the total mass of the additive as defined above, the share of the dehydratable inorganic compound that separates out water at a temperature of 150 °C or higher is from 50% to 100%.

[0157] In certain cases it is preferred that the additive to be used according to the invention contains, in addition to one or more of the said dehydratable inorganic compounds, one or more components from the group consisting of

[0158] - inorganic carbonates

[0159] - bright carbon formers

[0160] It is clear to the person skilled in the art here that the amount of carbon introduced into the molding material via the additive should be limited such that the carbon content of the molding material produced in a later cycle is less than that of the molding material produced in an earlier cycle.

[0161] The additive preferably contains aluminum hydroxide, and the aluminum hydroxide contained in the additive may have a water content in the range of 0.01% to 20%, preferably 0.01% to 12%. Particularly preferred is aluminum hydroxide having a water content of less than 1% (i.e., a water content of less than 1%) determined by thermogravimetric analysis in the temperature range up to 105 °C. Thus, there is no particularly large expense for drying the aluminum hydroxide.

[0162] In the additive, the aluminum hydroxide may be present in a mixture with iron oxide and / or iron hydroxide, and based on the total mass of the aluminum hydroxide, iron oxide and / or iron hydroxide, the share of the aluminum hydroxide is greater than 40%.

[0163] 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 pH value).

[0164] The additive to be used according to the invention preferably contains one or more dehydratable inorganic compounds which separate out water in the temperature range from 150 °C to 850 °C.

[0165] 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 most particularly preferably 0.05 wt%.

[0166] When producing the moulding material, the order in which the individual components are added together is flexible.

[0167] The addition agent can for example be provided as a mixture.

[0168] Alternatively, the addition agent, i.e. the additive and the montmorillonite clay-containing material, can be provided as a mixture and the other addition agents separately therefrom. This corresponds to the currently common provision of bright carbon formers in a pre-mixture containing montmorillonite clay. Thus, the equipment available in the foundry can continue to be used for storage and metering.

[0169] Alternatively, the additive can be provided separately from the other addition agents.

[0170] Alternatively, the additive and the optional montmorillonite clay-containing material, or the pre-mixture consisting of the additive and the montmorillonite clay-containing material can first be mixed with the recycled first moulding material and subsequently the other starting materials described above can be added.

[0171] Preferably, based on the total mass of the moulding material to be produced, by

[0172] - the moulding substrate,

[0173] - the recycled second moulding material, which is produced by recycling moulds and / or cores and / or parts thereof which have been cast outside the moulding material cycle,

[0174] - the recycled third moulding material, which is produced by recycling moulding material from uncast moulds and / or cores and / or parts thereof,

[0175] The total mass of the input raw materials in the composition group is 0.5% to 10% by weight, preferably 1% to 8% by weight, and particularly preferably 1.5% to 7% by weight.

[0176] Based on the total mass of the molding material to be produced, the mass of the montmorillonite clay in the additive is preferably 0.1% to 1.5% by weight, more preferably 0.3% to 1.2% by weight, and particularly preferably 0.5% to 1% by weight.

[0177] 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 by means of the additive (as defined above) is 0.1% to 1% by weight, preferably 0.3% to 0.8% by weight, and particularly preferably 0.4% to 0.7% by weight.

[0178] The montmorillonite clay to be used in the method according to the invention is preferably bentonite, selected from the group consisting of sodium bentonite, calcium bentonite, and mixtures thereof.

[0179] The molding substrate is preferably selected from the group consisting of quartz sand, olivine sand, chromite sand, zircon sand, and artificial ceramic sand, and mixtures of said sands. The 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.

[0180] The method 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 act as an additive to be used according to the invention as defined above.

[0181] Therefore, it is preferred that less than 50% by weight, preferably less than 25% by weight, and particularly preferably less than 10% by weight of the Al2O3 contained in the molding material is present in the form of corundum.

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

[0183] - A degree of compaction in the range of 25% to 55%, determined according to VDG operating specification P37 (April 1997), and / or

[0184] - 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

[0185] - Wet tensile strength in the range of 0.10 N / cm 2 to 0.50 N / cm 2 is determined according to VDG working specification P38 (May 1997), and / or

[0186] - Air permeability in the range of 70 to 200 is determined according to BDG guideline P41 (October 2013), and / or

[0187] - Active clay content in the range of 4.5% to 16% is determined by the methylene blue method according to VDG working specification P035 (October 1999), and / or

[0188] - Fluidity of 20% to 90% is determined according to the operating technical document of Morek Multiserw, type LUA-2e pile driver with electric drive, page 7.

[0189] Particularly preferably, the molded material manufactured in a later cycle of the method according to the invention has the following parameters:

[0190] - Compaction degree in the range of 35% to 55% is determined according to VDG working specification P37 (April 1997), and / or

[0191] - Wet compressive strength in the range of 15 N / cm 2 to 30 N / cm 2 is determined according to VDG working specification P38 (May 1997), and / or

[0192] - Wet tensile strength in the range of 0.20 N / cm 2 to 0.50 N / cm 2 is determined according to VDG working specification P38 (May 1997), and / or

[0193] - Air permeability in the range of 100 to 200 is determined according to BDG guideline P41 (October 2013), and / or

[0194] - Active clay content in the range of 6% to 14% is determined by the methylene blue method according to VDG working specification P035 (October 1999), and / or

[0195] - Fluidity of 30% to 90% is determined according to the operating technical document of Morek Multiserw, type LUA-2e pile driver with electric drive, page 7.

[0196] Preferably, all of the above parameters of the molded material are within the above preferred ranges, especially within the above particularly preferred ranges.

[0197] The molding materials used in earlier cycles of the method according to the invention typically have one or more of the following parameters:

[0198] - a carbon concentration of less than 2% to 5% by mass of the molding material, determined by elemental analysis,

[0199] - a nitrogen concentration of less than 0.05% to 0.1% by mass of the molding material, determined by elemental analysis,

[0200] - a sulfur concentration of less than 0.02% to 0.07% by mass of the molding material, determined by elemental analysis,

[0201] - a loss on ignition of up to 3% to 6%, determined according to VDG operating specification P33 (April 1997).

[0202] The molding materials produced in later cycles of the method according to the invention particularly preferably have one or more of the following parameters:

[0203] - a carbon concentration of less than 4%, preferably less than 3% by mass of the molding material, determined by elemental analysis,

[0204] - a nitrogen concentration of less than 0.2%, preferably less than 0.1% by mass of the molding material, determined by elemental analysis,

[0205] - a sulfur concentration of less than 0.05%, preferably less than 0.03% by mass of the molding material, determined by elemental analysis,

[0206] - a loss on ignition of up to 5%, preferably up to 4%, determined according to VDG operating specification P33 (April 1997),

[0207] wherein the carbon content of the molding material produced in later cycles of the method according to the invention is less than the carbon content of the molding material used in earlier cycles of the method according to the invention. Preferably, the nitrogen content, sulfur content and loss on ignition of the molding material produced in later cycles of the method according to the invention are less than those of the molding material used in earlier cycles of the method according to the invention. Preferably, all of the above parameters of the molding material are within the above preferred ranges, especially within the above particularly preferred ranges.

[0208] Another aspect of the present disclosure relates to the use of the additives defined above in a method according to the invention for reducing carbon-based emissions and / or carbon-based casting defects during a molding material cycle comprising two or more cycles of a molding material containing smectite clay. The above embodiments apply with respect to the additives preferably to be used and the preferred method designs.

[0209] Another aspect of the present disclosure relates to the use of the additives defined above as an alternative or partial replacement for the bright carbon former in a bentonite clay-bonded mold for cast iron. The above-described embodiments apply with respect to the additives to be preferably used and the preferred method designs. Description of the Drawings

[0210] The present invention will be described in detail below with reference to the schematic drawings. Shown herein are:

[0211] Figure 1 Showing the molding material cycle according to the prior art (casting in a coreless mold)

[0212] Figure 2 Showing the molding material cycle according to the method of the present invention (casting in a coreless mold)

[0213] Figure 3 Showing the molding material cycle according to the prior art (casting in a mold with a core)

[0214] Figure 4 Showing the molding material cycle according to the method of the present invention (casting in a mold with a core) Detailed Description of the Invention

[0215] The cycle of the molding material production is based on Figure 1 and Figure 2 at least includes steps (1) to (5) defined above, wherein the mold cast in step (3) does not contain the inserted core.

[0216] In step (1), a molding material is produced, the molding material comprising:

[0217] (i) a first recycled molding material produced by recycling the cast molding material obtained in an earlier cycle of the molding material cycle, the first recycled molding material not containing material from the cast core,

[0218] and

[0219] (ii) additives.

[0220] The additives comprise:

[0221] - one or more raw materials from the following group

[0222] - a new molding substrate (new sand),

[0223] - and at least one recycled molding material from the following group

[0224] - a second recycled molding material produced by recycling an uncast mold and / or core and / or parts thereof,

[0225] - 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 and cast, Figure 1 or Figure 2 shown, and is cast,

[0226] - Optionally containing smectite clay, preferably bentonite,

[0227] - Water.

[0228] Here, the recycled second molding material contains materials from uncast molds and / or cores and / or parts thereof, and / or the recycled third molding material contains materials from cast molds and / or cores and / or parts thereof.

[0229] In a method not according to the present invention ( Figure 1 ), 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 present invention ( Figure 2 ), when manufacturing the molding material in step (1), the additives defined above are added as another additive. Preferably, the additive contains magnesium hydroxide and / or aluminum trihydroxide or consists of magnesium hydroxide and / or aluminum trihydroxide.

[0231] In the method according to the present invention, the addition of bright carbon formers is not completely excluded, but the amount of carbon added to the molding material should be limited such that the carbon content of the molding material manufactured in a later cycle is less than that of the molding material manufactured in an earlier cycle.

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

[0233] In step (3), a casting is manufactured by casting the mold manufactured in step (2). The mold does not contain an inserted core.

[0234] In step (4), the casting manufactured in step (3) is separated from the mold, and a cast molding material is obtained. 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).

[0235] 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). When recycling, a part of the cast molding material is removed if necessary to obtain the molding material after removal.

[0236] If no part of the cast molding material is removed during recycling in step (5), to keep the quality of the molding material circulated in the cycle constant, a part of the molding material manufactured in step (1) of the next cycle is removed to obtain the molding material after removal.

[0237] 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.

[0238] One cycle of the molding material cycle is based 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.

[0239] Manufacturing the molding material in step (1) includes:

[0240] (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

[0241] and,

[0242] (ii) additives.

[0243] The additives include:

[0244] - one or more raw materials from the following group:

[0245] - new molding substrate (new sand),

[0246] - and at least one recycled molding material from the following group

[0247] - a recycled second molding material manufactured by recycling an uncast mold and / or core and / or parts thereof,

[0248] - a recycled third molding material manufactured by recycling in Figure 3 or Figure 4Manufactured from molds and / or cores and / or parts thereof that are cast outside the molded material cycle shown,

[0249] - Optionally containing smectite clay, preferably bentonite,

[0250] - Water.

[0251] In a method not according to the present invention ( Figure 3 ), when manufacturing the molded material in step (1), at least one bright carbon former is added as another additive.

[0252] In the method according to the present invention ( Figure 4 ), when manufacturing the molded material in step (1), the additives defined above are added as another additive. Preferably, the additive contains or consists of aluminum trihydrate.

[0253] In the method according to the present invention, the addition of bright carbon formers is not completely excluded, but the amount of carbon introduced into the molded material needs to be limited such that the carbon content of the molded material manufactured in a later cycle is less than that of the molded material manufactured in an earlier cycle.

[0254] In step (1a), a molded material (core molded material) for manufacturing at least one core is manufactured or provided. The molded material includes a molded substrate, a clay-free binder, and possible additives. Additives suitable for the molded material for manufacturing cores are known from the prior art. The binder is a conventional organic binder, such as a cold box binder or a phenolic resin, or a clay-free inorganic binder, such as a binder containing water glass.

[0255] In step (2), a mold bonded with smectite clay is manufactured from the molded material manufactured in step (1).

[0256] In step (2a), at least one core is manufactured from the molded material (core molded material) manufactured or provided in step (1a), and inserted into the mold manufactured in step (2).

[0257] In step (3), a casting is manufactured by casting the mold manufactured in step (2), and the mold contains at least one inserted core.

[0258] In step (4), the casting manufactured in step (3) is separated from the mold, and a cast molded material is obtained. The cast molded material includes the material from the cast mold and the material from the cast core.

[0259] Preferably, the mold with the casting is cooled before separation in step (4).

[0260] 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.

[0261] If no part of the cast molding material is removed when recycling in step (5), 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.

[0262] 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.

[0263] The present invention will be further described below by way of non-limiting examples.

[0264] 0. Testing methods and molding materials

[0265] 0.1 Testing methods

[0266] The following test methods (measurement methods) are used (Table 1)

[0267] Table 1: Measurement methods used

[0268]

[0269]

[0270] The sleeve and fin model device is manufactured as described in (https: / / www.researchdisclosure.com / database / RD705032) and used for the following tests.

[0271] 0.2 Materials used

[0272] All specifications of the raw material dosages relate to the pure raw materials, i.e., the dry materials, i.e., without any possible moisture or water of crystallization.

[0273] In the scope of the tests, the molding material from the regulated 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).

[0274] Table 2: Parameters of the starting molding material

[0275]

[0276]

[0277] Within the scope of the experimental study, recycled molding material from core sand (the recycled second molding material defined above) is used. For this purpose, cores are manufactured with an organic binder or an inorganic binder and subsequently ground via a circular vibrating screen of Webac company.

[0278] The starting material of the molding material manufactured with an organic binder is a core manufactured by the cold box process. The core is manufactured on a core shooter LL20 of Laempe company with a binder Biocure 8568P1 / Silcure 8431P2 sold by Hüttenes-Albertus Chemische Werke GmbH. For this purpose, sand type H32 of Quartzwerke company is used, and 0.7 parts by weight of the binder component is dosed per 100 parts by weight of sand. The core is manufactured with a sand shooting pressure of 450 kPa (4.5 bar) and a sand shooting time of 1.5 seconds, and subsequently cured by passing through with 10 g of dimethylpropylamine (N,N-dimethylpropylamine, catalyst GH6 of Hüttenes-Albertus Chemische Werke GmbH of Germany) for 45 s under a supply air pressure of 200 kPa (2 bar).

[0279] The starting material of the molding material manufactured with an inorganic binder is a core manufactured on a core shooter LL20 of Laempe company with a binder system Cordis 9477 / Anorgit 9476 sold by Hüttenes-Albertus Chemische Werke GmbH. For this purpose, sand type H32 of Quartzwerke company 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. The core is manufactured in a core box heated to 180 °C with a sand shooting pressure of 450 kPa (4.5 bar) and a sand shooting time of 1.5 seconds. For curing, the core is passed through with hot air at 120 °C for 1 minute under a supply air pressure of 200 kPa (2 bar).

[0280] The core is ground with a circular vibrating screen (test equipment Kreisschwingsieb-175056 of Webac company). The resulting molding material has the characteristics listed in Table 3.

[0281] Table 3: Parameters of the recycled molding material from core sand

[0282]

[0283] The abbreviation NG indicates that the measured value is below the detection limit.

[0284] 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 water glass of type Steinex 48 / 50 from Eurochemie GmbH and silica fume Q1-Plus from RW Silicium. For 100 parts by weight of quartz sand, 1.1 parts by weight of silica fume Q1-Plus and 3.4 parts by weight of Steinex 48 / 50 were admixed, and the shape of the core was formed in a Schüttkernkasten. Subsequently, the core was cured in a laboratory core shooter from Morek by introducing hot CO2 at 100 °C for 60 s with a supply pressure of 150 kPa (1.5 bar).

[0285] 1. Screening tests to identify suitable additives

[0286] 6 kg of quartz sand (H32 from Quarzwerke) was mixed with 120 ml of water in a mixer (a pan mixer LM-2e from Morek MULTISERW) at a speed of 40 revolutions per minute 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 revolutions per minute for 7 min. The mixture thus obtained was manually screened through a sieve with a mesh size of 3 mm, and subsequently the compactness (VDK) of the material was determined (test equipment model: PVG; ID number: 1501, year of manufacture: 2000). If the VDK was greater than 46.0%, the mixture was screened again and the VDK measurement was repeated. This process was repeated until the VDK was below 46.0%. If the VDK was less than 44.0%, 7 - 12 ml of water was added and mixed again for 1 min, and subsequently the screening and VDK measurement were repeated. The addition of water was repeated until the VDK exceeded 44.0%.

[0287] Three different mixtures containing a bright carbon former according to the prior art were used as references for the properties of the molding material:

[0288] 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.

[0289] 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)

[0290] 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).

[0291] In addition to the characteristic values of the molding material, 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 with the aid of the sleeve mold device described in (https: / / www.researchdisclosure.com / database / RD705032), that is, a mold manufactured according to the sleeve mold device described in (https: / / www.researchdisclosure.com / database / RD705032) is cast, and then the castings are shot-peened, and the surface roughness is measured according to DIN EN ISO 4287 (R_ISO). Two castings are studied separately. Here, the surface is measured 3 times each with a surface measuring instrument Mitutoyo SJ-500P at small, medium, and large distances of the ribs arranged in a star shape on a measuring section of 8 mm each. No uniform 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 carried out is considered. It is confirmed here that the surface roughness in all the obtained castings is within the range allowed for commercial use.

[0292] 1.1 Different types of aluminum hydroxide and magnesium hydroxide as additives

[0293] SH500 type (SH500 nuance-00, Alteo) and SH950 type (SH950 nuance-00, Alteo) Al(OH)3 are used for the study of aluminum hydroxide.

[0294] 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).

[0295] Table 4: Parameters of the brucite types used as additives

[0296]

[0297]

[0298] Table 5 shows the molding material properties and roughness of the casting when different hydroxides and bright carbon formers 1) to 3) used as reference 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).

[0299] Table 5: Molding material properties and roughness of the casting when different hydroxides or bright carbon formers are used as additives

[0300]

[0301]

[0302] 1.2 Study of aluminum hydroxide Al(OH)3 as an additive with the addition of bright carbon former

[0303] The good values for 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 is reduced by using Carboluxon 100 / P, but the values obtained when using pure aluminum hydroxide are sufficient.

[0304] Table 6: Molding material properties and roughness of the casting when aluminum hydroxide Al(OH)3 SH 950 with the addition of the bright carbon former Carboluxon 100 / P is used as an additive

[0305]

[0306] 1.3 Study of different carbonates as comparative additives

[0307] Sufficiently good molding material values cannot be achieved with 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).

[0308] Dolomite from Bianco Zandobbio 0 / 50 micron of Ziegler company and PE-DOL 90 from Possehl Erzkontor company are used. Generally speaking, the values of the molding materials are slightly worse compared with those when applying the above-mentioned hydroxides. However, these values still allow the materials to be used as a substitute for traditional bright carbon formers. The disadvantage of carbonates is that they contain carbon.

[0309] Table 7: Molding material characteristics when applying different carbonates or bright carbon formers as additives

[0310]

[0311]

[0312] The molding material characteristics 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 raw 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.

[0313] Table 8: Molding material characteristics and roughness of castings when applying different carbonate-hydroxide mixtures

[0314]

[0315]

[0316] 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).

[0317] Table 9: Molding material characteristics when using different carbonate-hydroxide mixtures with Carboluxon 100 / P added as a bright carbon former

[0318]

[0319] 1.4 Emissions of bentonite used and additives used

[0320] Table 10 shows the emission measurements of the bentonite used and the additives used. The emission measurements were carried out at the Foundry Institute of the 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.

[0321] The emissions of the additives to be used according to the invention are significantly lower than those of conventional bright carbon formers, such as the coke powder of LuxCarbon GmbH or the product Carboluxon 100 / P described above. While carbonates (not according to the invention), such as manganese carbonate, reduce the emissions of hydrocarbons, especially benzene, toluene, 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, carbonates are preferably used in combination with hydroxides.

[0322] Table 10: Results of emission measurements with different additives used (all data in mg / kg, i.e. mg of relevant emissions / kg of material)

[0323]

[0324] 2. Manufacture and testing of molding materials in the cycle

[0325] The aim of the test was to cast a specific amount of molding material several times and regenerate it. 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 present in the starting molding material and no longer added decrease, i.e. the share of the components no longer added in subsequent cycles decreases. The total amount of molding material in the cycle is constant, at about 8 kg. Two molds are manufactured and cast per cycle according to the sleeve model device as described in (https: / / www.researchdisclosure.com / database / RD705032).

[0326] For an illustration of the test execution, see Figure 2 the molding material cycle in

[0327] The cycle of the molding material cycle comprises the following steps:

[0328] Manufacture of molding materials (step (1), first cycle)

[0329] Test series 2.1, 2.2.1, 2.2.2, 2.3.1, 2.3.2 are as described below

[0330] In the first cycle, 6 kg of quartz sand of type H32 from Quarzwerke were used. The molding substrate was then mixed with 480 g of sodium bentonite (Natroben 25F, HAITALIA SpA, which is a sodium bentonite produced by activation of natural calcium bentonite) and 300 g of the corresponding additives and 120 ml of water on a Morek Multiserw mill mixer for 1 minute without water and then again for 7 minutes after adding water. To this end, the molding substrate was first mixed with 120 ml of water on a Morek Multiserw mill mixer for 1 minute and then again for 7 minutes on a Morek Multiserw mill mixer after adding 480 g of sodium bentonite (Natroben 25F, HAITALIA SpA) and 300 g of the corresponding additives.

[0331] Test series 2.4-2.6 are as follows

[0332] In the first cycle, 3.7 kg of H32 quartz sand from Quarzwerke were used. Subsequently, the molded substrate was mixed with 322 g of Volclay (foundry bentonite GEKO from Clariant GmbH, Germany). TM V, which is naturally occurring sodium bentonite) and 207 g of the corresponding additive and 130 ml of water were mixed on a Morek Multiserw mill mixer without water for 1 minute and then mixed again for 7 minutes after adding water. For this purpose, the molding substrate was first mixed with 130 ml of water on a Morek Multiserw mill mixer for 1 minute and then, after adding 322 g of Volclay and 207 g of the corresponding additive, mixed again on a Morek Multiserw mill mixer for 7 minutes.

[0333] The other embodiments apply to all test series 2.1 to 2.6 (unless otherwise stated).

[0334] The additive is introduced each time the molding material is produced (step (1)), and the additive accumulates with each cycle. By removing a portion of the cast molding material in step (5) or in step (1) of the next cycle (see Figure 2 ), the proportion of components present in the starting molding material and no longer added is reduced.

[0335] Manufacture of molds (step (2) in all cycles)

[0336] For this purpose, the molding material is filled into the mold of the sleeve molding device after 3 minutes of mixing, and compacted in 2 pressing processes (filling, pressing, refilling, pressing). This process is completed within another 3 minutes. 2 molds are manufactured for each test.

[0337] Casting (step (3) in all cycles)

[0338] After a waiting time of 30 minutes, the molds are cast in sequence. The molds are cast with the liquid metal of alloy GJL250 at 1450 °C by means of a casting ladle. The cast molds are left overnight until separation. Here, the castings cool, and the molding material first warms up and cools overnight in the mold.

[0339] Separation (step (4) in all cycles)

[0340] The castings are separated from the cast molding material.

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

[0342] The molding material is filled into the storage container, and the molding material blocks are crushed. The metal residues are removed.

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

[0344] New molding material is manufactured by adding bentonite, water, additives (as defined above), and a new molding base material (new sand) or by regenerating the core to produce a regenerated second molding material (details see below), and renovating the regenerated molding material (regenerated first molding material) from the previous cycle.

[0345] Add a new molding base material or a regenerated second molding material (details see below) manufactured by regenerating the core to the regenerated molding material from the previous cycle, mix it with 120 ml of water for 1 minute, and then add sodium bentonite (Natroben 25F, HITALIA S.p.A., test series 2.1, 2.2.1, 2.2.2, 2.3.1, 2.3.2) or Volclay (foundry bentonite GEKO V 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), and mix again for 7 minutes on a Morek Multiserw roller 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), and mix again for 7 minutes on a Morek Multiserw roller mixer.

[0346] 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 as defined above, by removing the same amount of the completely mixed molding material in each cycle.

[0347] An additive is introduced each time the molding material is manufactured (step (1)), and the additive accumulates with each cycle. By removing a part of the cast molding material, the share of the components that are present in the starting molding material and are not added in subsequent cycles is reduced.

[0348] 2.1 Additive Al(OH)3 or Mg(OH)2 when adding new molding base material in subsequent cycles

[0349] 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.

[0350] In all subsequent cycles 1 to 9, 4 kg of the used molding material from the previous casting is used respectively, and it is refurbished with 400 g of molding substrate (new molding substrate), 64 g of bentonite, and 20 g of the corresponding additive.

[0351] Use SH950 nuance - 00 from Alteo as the additive aluminum hydroxide Al(OH)3. The results of the tests with Al(OH)3 are shown in Table 11.

[0352] Use brucite type 3 from Ziegler&Co.GmbH as the additive magnesium hydroxide Mg(OH)2. The results of the tests with Mg(OH)2 are shown in Table 12.

[0353] When using the new molding substrate as the additive (see Figure 2 , step (1)), both additives show good molding characteristics and comparable surface quality, which can be seen from the measured roughness of the castings.

[0354] 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 characteristics and the castings have good quality. Correspondingly, the surface roughness of the castings is low.

[0355] Table 11: Characteristic values of the samples taken in the corresponding cycles to determine the molding material characteristics with Al(OH)3 as the additive, and the surface roughness of the castings

[0356]

[0357] Table 12: Eigenvalues of samples taken in the respective cycles to determine the properties of the moulding material with Mg(OH)2 as an additive, and surface roughness of the castings

[0358]

[0359]

[0360] 2.2 Al(OH)3 and Mg(OH)2 when adding cold box core sand in subsequent cycles

[0361] 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 tests are carried out and the properties of the moulding material and the castings are measured as described in Chapter 2.1. However, in subsequent cycles, instead of a new moulding substrate, a recycled second moulding material (see Figure 2 , step (1)) (the share of the amount of moulding material produced is shown in Table 13 or 16) is added, which is produced by recycling the uncast cores. The cores are produced with cold box binder ("cold box core sand").

[0362] 2.2.1 Aluminum hydroxide Al(OH)3 when adding cold box core sand in subsequent cycles

[0363] In the case of using aluminium hydroxide Al(OH)3, the properties of the moulding material show stability when adding 5% of cold box core sand, such that from cycle 15 onwards, the addition is increased to 10% cold box core sand (Tables 13 and 14). In addition, the properties of the moulding material remain stable.

[0364] Table 13: Composition and compaction of the moulding material mixture in the respective cycles

[0365]

[0366]

[0367] Table 14: Eigenvalues of samples taken in the respective cycles

[0368]

[0369]

[0370] Data on the CNS analysis of the moulding material in different cycles show an increase in the share of carbon and nitrogen originating from the addition of cold box core sand. Compared to the test series with the addition of new sand (see 2.1 above) instead of cold box core sand, the surface roughness of the castings is improved due to the addition of the core sand (Table 15).

[0371] Table 15: CNS analysis of the selected cycles and surface roughness of the castings belonging thereto

[0372]

[0373] (1) The abbreviation NG indicates that the measured value is below the detection limit.

[0374] 2.2.2 Mg(OH)2 when adding cold box core sand in subsequent cycles

[0375] 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.

[0376] Table 16: Composition and compactness of the molding material mixture in each cycle

[0377]

[0378]

[0379] Table 17: Characteristic values of the samples taken in the corresponding cycles

[0380]

[0381]

[0382] 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).

[0383] Table 18: CNS analysis of the selected cycles and surface roughness of the castings belonging thereto

[0384]

[0385] (1) The abbreviation NG indicates that the measured value is below the detection limit.

[0386] 2.3 Al(OH)3 and Mg(OH)2 when adding inorganically bonded core sand in subsequent cycles

[0387] 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 moulding material and the casting were measured as described in Chapter 2.1. However, in subsequent cycles, instead of a new moulding substrate, a recycled second moulding material manufactured by recycling uncast cores was added (see Figure 2 , step (1)) (for the amount fraction of the moulding material produced, see Tables 19 or 22), the cores being manufactured with an inorganic binder (sodium silicate) (“IOB core sand”). Thus, this is an inorganic moulding material cycle for all binders used.

[0388] 2.3.1 Aluminum hydroxide Al(OH)3 when adding inorganically bonded core sand in subsequent cycles

[0389] Even when adding IOB core sand, a moulding material cycle with stable moulding material properties was obtained when using aluminium hydroxide Al(OH)3, such that the addition of IOB core sand was increased to 10% from cycle 15 (Tables 19 and 20).

[0390] Table 19: Composition and compaction of the moulding material mixture in each cycle

[0391]

[0392]

[0393] Table 20: Characteristic values of the samples taken in the respective cycles

[0394]

[0395]

[0396] The moulding material analysis (Table 21) shows that carbon, nitrogen or sulphur do not accumulate significantly in the moulding material and that the C (carbon-containing) components from inorganic binders (such as surfactants) are minor. The low C load (carbon load) is one of the major advantages of the inorganic moulding material cycle, as very low emissions can be expected (see below). Despite the low carbon content, the surface roughness obtained (Table 21) is still very close to that of the tests with cold box core sand added (test series 2.2.1).

[0397] Table 21: CNS analysis of the selected cycles and surface roughness of the castings belonging thereto

[0398]

[0399] (1) The abbreviation NG indicates that the measured value is below the detection limit.

[0400] 2.3.2 Magnesium hydroxide Mg(OH)2 when adding inorganically bonded core sand in subsequent cycles

[0401] Using magnesium hydroxide Mg(OH)₂ in the form of brucite as an additive has shown that after several cycles, 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).

[0402] That is, similar to adding cold box core sand (test series 2.2.2), using Mg(OH)₂ as an additive also did not result in a cycle of molded materials with stable molded material properties here. 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 of the prescribed form (target compaction). The active clay content and the wet tensile strength decreased significantly with increasing number of cycles. Although this could be compensated for by dosing bentonite, overall there was no cycle of molded materials with stable molded material properties.

[0403] Table 22: Composition and compaction of the molded material mixture in each cycle

[0404]

[0405] Table 23: Characteristic values of the samples taken in the respective cycles

[0406]

[0407] 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.

[0408] Table 24: CNS analysis of the selected cycles and surface roughness of the associated castings

[0409]

[0410]

[0411] (1) The abbreviation NG indicates that the measured value was below the detection limit.

[0412] 2.4 Additive Al(OH)3 when adding new molding base material in subsequent cycles

[0413] Eleven cycles (0 - 10) were carried out in the case of using the sleeve model device described in ( https: / / www.researchdisclosure.com / database / RD705032 ), where 100% new type H32 molded substrate from Quartzwerke was used in the first test.

[0414] In all subsequent cycles 1 to 10, 3.7 kg of used molding material from the previous casting was used respectively, and it was refurbished with 185 g of molding substrate (new molding substrate), 26 g of bentonite and 23 g of the corresponding additives (Table 25). SH950 nuance - 00 from Alteo was used as the additive aluminum hydroxide Al(OH)₃. Stable molding material properties were achieved (Table 26).

[0415] When using the new molding substrate as an additive (see Figure 2 , step (1)), good molding properties and good to excellent surface quality were achieved, which can be seen from the measured roughness of the castings. As expected, the CNS analysis showed non - significant carbon and nitrogen contents after 11 cycles because only inorganic materials were used (see Table 27).

[0416] Table 25: Composition and compactness of the molding material mixture in each cycle

[0417]

[0418]

[0419] Table 26: Characteristic values of the samples taken in the corresponding cycles

[0420]

[0421] Table 27: CNS analysis of the selected cycles and surface roughness of the belonging castings

[0422]

[0423]

[0424] (1) The abbreviation NG means that the measured value is below the detection limit.

[0425] 2.5 Al(OH)3 when adding cold box core sand in subsequent cycles

[0426] 11 cycles (0 - 10) were carried out 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 2.4. 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 quantity fraction of the molding material produced, see Table 28), and the cores were manufactured with a cold box binder ("cold box core sand"). Stable molding material properties were achieved (Table 29).

[0427] Table 28: Composition and compaction of the molding material mixture in each cycle

[0428]

[0429] Table 29: Characteristic values of the samples taken in the respective cycles

[0430]

[0431] The data of the CNS analysis of the molding material after 11 cycles showed a distinct carbon and nitrogen fraction originating from the cold box core sand addition, especially compared to the test series with the addition of new sand (Table 30).

[0432] Table 30: CNS analysis of the selected cycles and the surface roughness of the associated castings

[0433]

[0434]

[0435] (1) The abbreviation NG indicates that the measured value was below the detection limit.

[0436] 2.6 Al(OH)3 when adding inorganically bonded core sand in subsequent cycles

[0437] 11 cycles (0 - 10) were carried out 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 2.4. 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)) (see Table 31 for the amount fraction of the molded material produced), the core is made with an inorganic binder (sodium silicate) (“IOB core sand”). Thus, this is about the inorganic molding material cycle for all binders used. Stable molding material properties are achieved (Table 32).

[0438] Table 31: Composition and compaction of the molding material mixture in each cycle

[0439]

[0440] Table 32: Eigenvalues of the samples taken in the corresponding cycles

[0441]

[0442]

[0443] The molding material analysis (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 significant 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).

[0444] Table 33: CNS analysis of the selected cycles and surface roughness of the castings belonging thereto

[0445]

[0446] (1) The abbreviation NG means that the measured value is below the detection limit.

[0447] 3. Molding material cycle with gradually decreasing carbon content in the molding material

[0448] The purpose of the test is as follows: to cast and regenerate 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 guided 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 were 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).

[0449] For the illustration of the test execution, refer toFigure 4 The recycling of the molding material

[0450] The cycle of the molding material recycling includes the following steps:

[0451] Manufacture of molding materials (step (1), first cycle)

[0452] In the first cycle, the recycled molding material (starting molding material) of the molding material recycling from the brake disc foundry is used. (See point 0.2 above)

[0453] The recycled molding material is conveyed from the BigBag to the silo in front of the Eirich mixer (Eirich high-performance mixer R09 with a capacity of 150 liters and a maximum of 240 kg, operating in batches under normal pressure) by means of a BigBag unloading station and two conveyor belts. The previously weighed additives (additive materials) bentonite, molding base material or core molding material and additives are placed on the silo discharge belt. SH950 type Al(OH)3 (SH950 nunce - 00, Alteo) is used as the additive

[0454] In each production (step (1), see Figure 4 ), additives are introduced when the molding material is produced. The additives accumulate with each cycle. By removing a part of the cast molding material in step (5) or step (1) of the next cycle (see Figure 4 ), the share of the components that are present in the starting molding material and are no longer added is reduced

[0455] The molding material is taken from the silo and transported to the mixer together with the additive materials. 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 the transport container. The transport container is transported to the molding equipment

[0456] Depending on the water content of the mixture, the mixer program is selected between a mixing process without an intermediate pause (Table 35) and a mixing process with an 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 compaction degree is not known, the required amount of water can be more easily determined by an intermediate pause in the mixing process, and subsequent mixtures are produced without an intermediate pause

[0457] Table 34: Mixing process with an intermediate pause

[0458]

[0459] Table 35: Hybrid process without intermediate pauses

[0460]

[0461] Manufacture of molds (step (2) in all cycles)

[0462] 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.

[0463] 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 dimensions 700×500×200 / 200 mm, model plate dimensions 650×450×30 mm) by means of a static pressure (Seiatsu) air flow molding method. The time during which the air flow is guided 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.

[0464] Table 36: Compaction parameters

[0465] Lower box pressing pressure: <![CDATA[90N / cm 2 > Upper box pressing pressure: <![CDATA[80N / cm 2 > Lower box pressing time: 2000s Upper box pressing time: 2000s Lower box SEIATSU time (static pressure time): 0.50s Upper box SEIATSU time (static pressure time): 0.50s

[0466] 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.

[0467] Casting (step (3) in all cycles)

[0468] The mold is cast at 1450 °C with liquid metal of alloy GJL 250 by means of a pouring ladle in a carrier iron with a single-sided shear.

[0469] Manufacture (steps (2), (2a)) and cast the next mold.

[0470] The cast mold is left to stand for 4 hours until separation. The casting cools here and the molding material heats up.

[0471] Separation (step (4) in all cycles)

[0472] Open the upper and lower boxes. Separate the castings from the cast molding material. In the three molding material cycles studied, the core sand was treated in different ways:

[0473] 1. In test series A, where new sand was used as the dosing addition to the molding base material, cores bonded with sodium silicate hardened by means of CO2 (see point 0.2 above) were used, which did not decompose upon separation and were completely removed at that point in the cycle.

[0474] 2. In test series B, using cold box cores, the cores decomposed completely in the center and could no longer be separated from the molding material. The core heads did not decompose and could not be simply crushed either. Therefore, the core heads were removed at that point in the cycle.

[0475] 3. In test series C, using cores bonded with inorganic binder (binder Cordis 9477 / Anorgit 9476, see point 0.2), the cores decomposed only in the edge layer, but could not be very easily crushed by hand. Therefore, the IOB core sand was not removed.

[0476] Regeneration (step (5) in all cycles)

[0477] Spread the molding material on the ground and crush the molding material blocks with a shovel. Remove the metal residues. The molding material was left to rest on the workshop floor for at least 3 hours to cool. After cooling, the molding material was filled back into the large bags with a shovel.

[0478] Manufacture of molding materials (step (1) in the 2nd cycle and each subsequent cycle)

[0479] New molding material was produced by adding bentonite, water, additives (as defined above) and a new molding base material (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), renovating the regenerated molding material from the previous cycle (regenerated first molding material). The flow of the mixing process is as described in the above for step (1) of the first cycle.

[0480] 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 as defined above, by removing the same amount of the completed mixed molding material in each cycle.

[0481] An additive was introduced each time the molding material was produced (step (1)), and this additive accumulated with each cycle. By removing a portion of the cast molding material, the share of the components present in the starting molding material and not added in subsequent cycles decreased.

[0482] 3.1 Test series for adding new molding base material (new sand) in step (1) (Test series A)

[0483] When manufacturing the mold (see step (2) above), cores bonded with sodium silicate are used, which do not decompose after casting (see point 0.2 above) and are removed in step (4) as described above.

[0484] In a test series with 30 cycles (A1 - A30, see Table 37), in each successive cycle, the recycled molding material (the first recycled 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).

[0485] Table 37: Composition and degree of compaction of the molding material mixture in each cycle

[0486]

[0487] (1) "The first recycled molding material" here refers to the amount of molding material that is reused after recycling from the respective previous cycle.

[0488] (2) Dosage of water added

[0489] (3) Measured water content of the mixture

[0490] Table 38: Characteristic values of the samples taken in the respective cycles to determine the properties of the molding material

[0491]

[0492]

[0493] Table 39: Analysis of samples from each cycle

[0494]

[0495] 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 properties of the molding material basically remain unchanged (Table 38).

[0496] 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).

[0497] Table 40: Surface roughness of the castings manufactured during the test series A

[0498]

[0499] 3.2 Test series for adding organically bonded core sand (Test series B)

[0500] When manufacturing the mold (see step (2) above), a cold box core is placed (see point 0.2 above), and the cold box core decomposes completely in the center and can no longer be separated from the molding material.

[0501] In the test series with 30 cycles (B1 - B30, see Table 41), based on the above-mentioned regenerated starting molding material from the brake disc foundry, a regenerated second molding material manufactured from the regenerated core is added (see Figure 4 ), and the core is manufactured 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 regenerated with the cold box binder.

[0502] Table 41: Composition and compactness of the molding material mixture in each cycle

[0503]

[0504]

[0505] (1) "Regenerated first molding material" here means the amount of molding material reused after regeneration from the respective previous cycle,

[0506] (2) Dosage of water added

[0507] (3) Measured water content of the mixture

[0508] Table 42: Characteristic values of the samples taken in the corresponding cycles to determine the molding material properties

[0509]

[0510]

[0511] Table 43: Analysis of the molding material samples from the selected cycles

[0512]

[0513] 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, and 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).

[0514] In the series of tests, the surface roughness of the castings was also determined (Table 44). It was observed that good surfaces were obtained despite the decreasing share of carbon in the molding material. No casting defects were observed.

[0515] Table 44: Surface roughness of the castings produced during experimental series B

[0516]

[0517] 3.3 Test series for adding inorganically bonded core sand (Test series C)

[0518] When manufacturing the mold (see step (2) above), an inorganic bonded core was used (binder Cordis 9477 / Anorgit 9476, see point 0.2 above), which decomposes only in the edge layer and cannot be very easily crushed by hand.

[0519] 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 ), the cores being produced with a water glass binder (Anorgit / Cordis system); i.e., 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 a core produced with a water glass binder (Anorgit / Cordis system).

[0520] Table 45: Composition and degree of compaction of the molding material mixture in the individual cycles

[0521]

[0522]

[0523] (1) "Regenerated first molding material" here means the amount of molding material reused after regeneration from the respective previous cycle

[0524] (2) Dosage of water added

[0525] (3) Measured water content of the mixture

[0526] Table 46: Characteristic values of the samples taken in the respective cycles to determine the properties of the molding material

[0527]

[0528]

[0529] Table 47: Analysis of samples from the selected cycles

[0530]

[0531]

[0532] The tests clearly show that as the moulding material is replaced more and more, the ignition loss and the contents of carbon, nitrogen and sulfur decrease gradually (Table 47). Here, the properties of the moulding material remain basically unchanged (Table 46).

[0533] 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).

[0534] Table 48: Surface roughness of the castings manufactured during the test series

[0535]

[0536] 3.4 Landfill grade of recycled molding materials

[0537] From all three test series, the regenerated 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:

[0538] According to the German landfill and long-term storage regulations of July 4, 2020 (landfill regulations), the starting regenerated 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 regenerated moulding material of test series B only has a TOC value that is slightly too high for classification into landfill class I, so it should 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.

[0539] The regenerated materials in test series A and C belong to landfill class I.

[0540] Table 49 (the abbreviation NG means that the measured value is below the detection limit)

[0541]

[0542] 1. Determined according to DIN EN 14346:2007-03

[0543] 2. Determined according to DIN EN 15169:2007-05

[0544] 3. Determined in accordance with DIN EN 15936:2012-11 (AN, L8: Edition A; FG, F5: Edition B)

[0545] 4. Determined in accordance with the notice of the National Waste Working Group ( Abfall), Notice No. 35, Abbreviation: KW / 04:2019-09

[0546] 5. Determined in accordance with DIN EN ISO 10523 (C5):2012-04

[0547] 6. Determined in accordance with DIN EN 15216:2008-01

[0548] 7. Determined in accordance with DIN EN ISO 10304-1 (D20):2009-07 (D20)

[0549] 8. Determined in accordance with DIN EN ISO 14403-2:2012-10

[0550] 9. Determined in accordance with DIN EN ISO 17294-2 (E29):2017-01 (E29)

[0551] 10. Determined in accordance with DIN EN ISO 12846 (E12):2012-08

[0552] 11. Determined in accordance with DIN EN 1484:2019-04

[0553] 12. Determined in accordance with DIN EN ISO 14402 (H37):1999-12

[0554] 3.5 BTX Emission Potential of Recycled Molding Materials

[0555] The starting molding materials of the regulated molding material cycle from the brake disc foundry and the molding materials from cycles A-30, B-30, and C-30 are studied for their BTX emission potential. For this purpose, after drying at 105 °C, the samples are crushed 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). Cool at -20 °C for at least 12 hours, i.e., store the mortar of the planetary ball mill at -20 °C for at least 12 hours before use to avoid overheating of the samples during the grinding process. Subsequently, weigh 10 mg of the sample into the pyrolysis tube. Perform a double determination for each sample. The measurements are carried out with the following instruments:

[0556] ·GERSTEL MPS

[0557] ·GERSTEL TDU 2 with pyrolysis module

[0558] ·Agilent 8890B gas chromatograph and Agilent 5977 mass spectrometer

[0559] ·RESTEK 13868RXI - 624Sil MS capillary column, - 60°C - 300°C (320°C): 30m × 250μm × 1.4 0.25mm

[0560] ·150ml stainless steel mortar and stainless steel grinding balls

[0561] ·Hamilton electronic holder (VWR part number HAMIDS86200)

[0562] ·Hamilton 1μL syringe (VWR part number 549 - 1224)

[0563] ·Carbotrap B packed Glass Inlet Liner (temperature upper limit 450°C) (Gerstel part number 013248 - 005 - 00)

[0564] ·Quartz pyrolysis tube (Gerstel part number 018437 - 020 - 00)

[0565] ·Adsorbent matrix Carbopack TM B, 60 - 80 mesh (VWR part number SUPL20273)

[0566] ·Silanized glass wool (VWR part number SERA22367.01)

[0567] Subject to the following conditions:

[0568] Gas chromatography (GC) parameters

[0569]

[0570] KAS parameters

[0571] (KAS = cold feed system - pyrolyzing the sample, condensing the pyrolysis gas and then volatilizing it for GC measurement

[0572]

[0573] Calibration Method:

[0574] MSD parameters (MSD = mass spectrometry detector)

[0575]

[0576]

[0577] TDU parameters (TDU = thermal desorption unit)

[0578]

[0579] Pyrolysis parameters

[0580]

[0581] Calibrated based on the standards of benzene, toluene, m-xylene and p-xylene, styrene, o-xylene, ethylbenzene, cumene.

[0582] Specimen Method:

[0583] MSD parameters

[0584]

[0585] TDU parameters

[0586]

[0587]

[0588] Pyrolysis parameters

[0589]

[0590] Characteristic values of the method

[0591]

[0592]

[0593] Evaluated with the software MassHunter.

[0594] The results shown in Table 50 clearly show that the use of the additive according to the invention can significantly reduce the emission 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.

[0595] Table 50: Comparison of the pyrolysis (GC-MS) of the molding material after 30 cycles with the starting molding material (all statements are in mg emissions / kg sample material)

[0596]

[0597] In Table 50, the indication “<…” means that the content of the corresponding BTEX compound is below its detection limit.

[0598] The following applies to the value range of the line “BTEX at 900 °C”:

[0599] The lower limit value corresponds to the sum of the contents of the BTEX compounds above the respective detection limits, such that a value can be determined (in the case of the starting moulding material, these are benzene, toluene, styrene and m-xylene, p-xylene).

[0600] 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 reducing carbon-based emissions and / or carbon-based casting defects during a molding material cycle comprising two or more cycles of a molding material containing smectite clay-containing molding material, the method comprising: - reducing the carbon content in the molding material such that the molding material manufactured in a later cycle has a lower carbon content compared to the molding material manufactured in an earlier cycle, and - introducing an additive in one or more later cycles of the two or more cycles of the molding material cycle, the additive containing at least one dehydratable inorganic compound that separates water at a temperature of 150 °C or higher.

2. The method according to claim 1, having the following steps: - casting in a mold containing a molding material bonded by smectite clay in an earlier cycle of the two or more cycles of the molding material cycle, wherein a cast molding material is obtained, - regenerating the cast molding material in the earlier cycle, wherein the regenerated molding material contains carbon such that a first regenerated molding material is obtained, - manufacturing a molding material in a later cycle of the two or more cycles of the molding material cycle, the molding material comprising (i) the first regenerated molding material, and (ii) an additive material, the additive material comprising - the additive as defined in claim 1 - and one or more raw materials from the following group - a molding substrate, - a second regenerated molding material manufactured by regenerating a molding material from an uncast mold and / or core and / or a part thereof, - a third regenerated molding material manufactured by regenerating a molding material from a mold and / or core and / or a part thereof cast outside the molding material cycle, - and optionally smectite clay, wherein the molding material is manufactured such that it has a lower carbon concentration compared to the molding material manufactured in the earlier cycle.

3. The method according to any one of the preceding claims, wherein the additive contains one or two compounds from the group consisting of aluminum hydroxide and magnesium hydroxide, wherein preferably, the molding material is manufactured in the later cycle such that the manufactured molding material has a higher total concentration of aluminum hydroxide and / or magnesium hydroxide compared to the first regenerated molding material in the earlier cycle.

4. The method according to any one of the preceding claims, wherein the regenerated molding material in the earlier cycle contains at least one bright carbon former and / or its carbon-containing reaction product formed during casting.

5. The method according to any one of the preceding claims, wherein in the later cycle, in order to manufacture the molding material, carbon in the form of one or more bright carbon formers is added as an additional additive, wherein the total mass of carbon introduced by the bright carbon former is less than the total mass of carbon removed by emissions and molding material removal in the earlier cycle.

6. The method according to any one of the preceding claims, wherein the carbon content in the molding material is gradually reduced over 2 cycles, preferably over at least 10 cycles, particularly preferably over at least 15 cycles.

7. The method according to any one of the preceding claims, wherein in the earlier cycle, casting is carried out in a mold having at least one inserted core.

8. The method according to claim 7, wherein the core is made by means of an organic binder or by means of an inorganic binder.

9. The method according to any one of claims 7 and 8, wherein the core cast in the earlier cycle is made by means of an organic binder, and the molding material produced in the later cycle contains carbon, wherein at least 70% by weight, preferably at least 80% by weight, and particularly preferably at least 90% by weight, most particularly preferably at least 95% of the carbon is derived from the organic binder of the cast and non-cast cores.

10. The method according to any one of the preceding claims, wherein, based on the total mass of aluminum hydroxide and magnesium hydroxide in the additive, the proportion of aluminum hydroxide is at least 80%, preferably at least 90%, and particularly preferably at least 95%, most particularly preferably 99%.

11. The method according to any one of claims 1 to 6, wherein in the earlier cycle, casting is carried out in a mold without inserted cores.

12. The method according to any one of claims 1 to 11, wherein the molding material guided in the cycle is used for manufacturing a mold for cast iron.

13. The method according to any one of claims 1 to 12, comprising: - reducing the sulfur content in the molding material such that the molding material produced in the later cycle has a lower sulfur content than the molding material produced in the earlier cycle.

14. Use of an additive as defined in claim 1 in a method according to any one of claims 1 to 13.

15. Use of an additive as defined in claim 1 as an alternative to a bright carbon former in a mold bonded with montmorillonite clay for cast iron.

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