A composition for creating a coating on the body of a metal casting mold or core that releases formaldehyde when heated.

Abstract

The present invention relates to a composition for producing a coating on the body of a metal casting mold or core that releases formaldehyde when heated, wherein the coating forms the surface of the mold or core that comes into contact with the molten metal during the casting process, and the composition comprises (a) one or more refractory particles, (b) at least one ammonium salt [compound (b)], wherein the total mass of compound (b) is 0.1% to 10% by weight based on the total mass of the refractory particles (a), and (c) a carrier liquid selected from the group consisting of water, alkanols, and mixtures thereof.

Description

[Technical Field]

[0001] [Background technology]

[0002] The use of certain compounds as formaldehyde scavengers in coatings on the bodies of metal casting molds or cores that release formaldehyde when heated, wherein the coating forms the surface of the mold or core that comes into contact with the molten metal during the casting process, and the use of compositions containing one or more of these compounds for the preparation of coatings on the bodies of metal casting molds or cores that release formaldehyde when heated, wherein the coating forms the surface of the mold or core that comes into contact with the molten metal during the casting process. The corresponding molds and cores, as well as their preparation, are also described.

[0003] Metal casting molds and cores are produced by molding a molding material mixture containing a mold base material (e.g., sand) and a binder, and then curing the molded molding material mixture. This often involves using an organic binder that releases formaldehyde when heated, such as polyurethane formed by polyaddition of phenol-formaldehyde resin and polyisocyanate, or a formaldehyde condensation resin, such as a formaldehyde condensation resin from the group consisting of phenol-formaldehyde resin, furan-formaldehyde resin, urea-formaldehyde resin, and melamine-formaldehyde resin.

[0004] A mold is a negative mold that encloses the cavity to be cast, resulting in the production of a casting. The internal contour of the casting may be formed by a core. In the manufacture of the mold, it is possible to mold the cavity into the molding material using a model of the casting to be produced. The core is usually molded within a core box.

[0005] Typically, in the production of molds and cores for metal casting, by molding a mixture of molding materials (as described above) and then curing the molded mixture, a mold or core body is first formed, already having the desired mold or core contour. In particular, in steel and iron casting, a coating is typically fabricated on this thus formed body, and the coating forms the surface of the mold or core that comes into contact with the molten metal during the casting process. Such a coating is typically referred to as a refractory coating. In the context of this application, the terms “mold” or “core” refer, respectively, to the entire mold or core body and the coating (refractory coating) placed on this body. This coating functions as an interface and / or barrier layer between the core or mold body and the casting metal, and, in particular, functions for the controlled suppression of the mechanism of casting defect formation at the interface between the metal and the core / mold, or for the utilization of metallurgical effects. Generally, a refractory coating in casting technology should perform the following functions, known to those skilled in the art: - To improve the smoothness of the casting surface, and / or - To prevent chemical reactions between the components of the molding material mixture and the molten metal, and thus facilitate separation between the mold / core and the casting, and / or - To prevent surface defects on castings, such as bubbles, penetration, leaf vein, and / or scab.

[0006] Ready-to-use compositions for coating mold and core bodies are typically suspensions of fine particles that are fire-resistant to highly refractory inorganic materials (refractories) in a carrier liquid (e.g., water, alkanols, or mixtures thereof), with further components being suspended or dissolved in the carrier liquid. The refractory coating composition is applied to the body in a suitable manner, and then the carrier liquid is removed by drying to form a coating on the body. Drying is typically carried out at temperatures above 40°C, preferably in the range of 50°C to 200°C. At these temperatures, the mold or core body releases a considerable amount of formaldehyde. Such releases result in considerable contamination of the workplace.

[0007] DE10 2008 025 311(A1) discloses a mold for metal casting in which a layer of contaminant-absorbing material is placed in at least a portion of the mold's gas outlet region. The gas outlet region is understood to mean the region of the mold from which gas components can escape during the casting operation. The gas outlet region may correspond to the entire outer surface of the mold, or only a portion of the outer surface of the mold may be used for the release of gas components. For example, in in-box metal casting, the box is used for the structure of the mold that covers the bottom and sides of the mold. In this case, essentially only the top surface of the mold is available for the release of gas components. The outer surface of the mold is understood to mean the surface from which off-gases formed during the casting operation can escape from the mold. This outer surface is visible when viewing the mold from the outside and does not come into contact with the liquid metal during the casting operation. In contrast, the inner surface is understood to mean, for example, the surface of the mold cavity surrounded by the mold.

[0008] Materials that combine with formaldehyde through chemical reactions to produce non-volatile reaction products are not disclosed in DE10 2008 025 311(A1).

[0009] EP0 012 169(A1) discloses a particleboard or fiberboard bonded primarily with amino resins, characterized in that a portion of the board's surface area, preferably an intermediate layer, contains at least partially a binder that is not part of the amino resin group, and simultaneously allows the introduction of a certain amount of formaldehyde-reactive material that reacts with or can bind to formaldehyde under the action of moisture heat. [Overview of the Initiative]

[0010] The object of the present invention is to reduce the release of formaldehyde that occurs during the drying of a refractory coating on a mold or core that releases formaldehyde when heated.

[0011] In a first aspect of the present invention, the objective is to produce a coating on the body of a metal casting mold or core that releases formaldehyde when heated, -(a) One or more refractory particles, (b) at least one ammonium salt [compound (b)], The total mass of compound (b) is 0.1% to 10% by weight, preferably 0.1% to 5% by weight, based on the total mass of the refractory particles (a), and is an ammonium salt. -(c) optionally achieved by using a composition comprising a carrier liquid selected from the group consisting of water, alkanols, and mixtures thereof, The coating forms the surface of the mold or core that comes into contact with the molten metal during the casting process. Preferably, the coating extends not only to the surface of the mold or core that comes into contact with the molten metal during the casting process, but also to further areas of the mold or core. Preferably, the coating extends over 50%, more preferably 70%, more preferably 80%, particularly preferably 90%, and especially particularly 95% of the surface of the mold or core. Most preferably, the coating extends over the entire surface of the mold or core. [Modes for carrying out the invention]

[0012] The mold or core body in this specification is typically formed from a mixture of molding materials bound together with a binder that releases formaldehyde when heated, the binder is preferably -Polyurethane formed by polyaddition of phenol-formaldehyde resin and polyisocyanate. - Preferably, the formaldehyde condensation resin is selected from the group consisting of phenol-formaldehyde resin, furan-formaldehyde resin, urea-formaldehyde resin, and melamine-formaldehyde resin.

[0013] More preferably, the mold or core body is formed from a mixture of molding materials bound together with a binder that releases formaldehyde when heated, the binder is -Polyurethane formed by polyaddition of phenol-formaldehyde resin and polyisocyanate. -phenol-formaldehyde resin, and - Selected from the group consisting of furan-formaldehyde resins.

[0014] The binder is present in a hardened state within the mold or core body.

[0015] Surprisingly, in the case of molds and cores that release formaldehyde when heated, it has been found that the amount of formaldehyde released into the environment during the drying process of the refractory coating is significantly reduced when the refractory coating is made using the composition defined above. Currently, it is assumed that compound (b) can bind to formaldehyde through a chemical reaction that forms a non-volatile reaction product, thus resulting in less formaldehyde escaping into the environment from the core or mold. Therefore, compound (b) is referred to herein as a formaldehyde scavenger.

[0016] In addition to the ability to irreversibly bind the non-volatile reaction product to formaldehyde, several further criteria should be noted in the selection of compound (b). For example, compound (b) itself should not be volatile and should not decompose at the temperature at which the mold and core are dried. Therefore, the decomposition temperature must be higher than the temperature at which the mold and core are dried (50 °C to 200 °C, preferably 100 °C to 180 °C). Therefore, compound (b), which is a solid with a low vapor pressure or a high-boiling liquid, is preferred. In addition, compound (b) must be soluble in the carrier liquid (c) in a sufficient amount.

[0017] Furthermore, compound (b) should not be toxic as far as possible, should not require specific occupational protection and safety precautions, and should be reliably available on the market under acceptable conditions.

[0018] Compound (b) is preferably a compound that is soluble in the carrier liquid (c).

[0019] In the context of the present invention, the expression "at least one ammonium salt" is intended to indicate one or more ammonium salts. Mixtures of ammonium salts can also be used for the purposes of the present invention. In the remainder of this specification, the expression "ammonium salt" is understood in both the plural and the singular for the purposes of the present invention. In the context of the present invention, the ammonium salt is preferably an ammonium slat of the formula (R)4N + A - wherein R is hydrogen, C 1-4Selected from the group consisting of alkyl and phenyl, and A is a suitable counter ion (also called an anion). Preferably, R is hydrogen. The term "alkyl alone" or "in combination" means, unless otherwise specified, a radical derived from an alkane containing 1 to 4 carbon atoms. For example, CF-G alkyl defines a linear or branched alkyl radical having F to G carbon atoms. For example, C1-4 alkyl defines a linear or branched alkyl radical having 1 to 4 carbon atoms, such as methyl, ethyl, 1-propyl, 2-propyl, 1-butyl, 2-butyl, 2-methyl-1-propyl, etc. The alkyl group can be a linear alkyl or a branched alkyl. Suitable anions A can be organic or inorganic.

[0020] Suitable anions A include, for example, trifluoroacetate, acetate, benzenesulfonate, benzoate, bicarbonate, hydrogen tartrate, bromide, carbonate, chloride, citrate, dihydrochloride, formate, hydrobromide, hydrochloride, methylsulfate, nitrate, oxalate, phosphate, sulfate, etc.

[0021] Advantageously, the ammonium salt is selected from the group consisting of ammonium acetate, ammonium citrate, ammonium formate, ammonium oxalate, and ammonium chloride. In particular, ammonium chloride and ammonium citrate are preferred.

[0022] In the compositions for use according to the present invention, the total mass of compound (b) is 0.1% or more, preferably 0.5% or more, more preferably 1.0% or more, based on the total mass of refractory particles (a). It is further understood that the upper limit of the total mass of compound (b) is 10% by weight or less, preferably 9% by weight or less, more preferably 8% by weight or less, even more preferably 7% by weight or less, even more preferably 6% by weight or less, and even more preferably 5% by weight or less, based on the total mass of refractory particles (a). In one embodiment of the composition of the present invention, the total mass of compound (b) is 0.1% to 10% by weight, preferably 0.1% to 9% by weight, even more preferably 0.1% to 8% by weight, even more preferably 0.1% to 7% by weight, even more preferably 0.1% to 6% by weight, and particularly preferably 0.1% to 5% by weight, based on the total mass of refractory particles (a). If the amount of compound (b) is small, a significant reduction in formaldehyde emissions is not achieved. A larger amount of compound (b) may affect the quality of the resulting coating.

[0023] According to the typical understanding of those skilled in the art (see DIN 51060:2000-06), “refractories” refer to lumps, materials, and minerals that can withstand, at least for a short time, the thermal stress of casting or solidifying molten iron, and usually cast iron. “High refractories” refer to lumps, materials, and minerals that can withstand, for a short time, the heat of casting molten steel. The temperatures that can occur in casting molten steel are usually higher than the temperatures that can occur in casting molten iron or cast iron. Refractory lumps, materials, and minerals (refractories) and high refractory lumps, materials, and minerals are known to those skilled in the art, for example, from DIN 51060:2000-06. Unless otherwise specified, powdered refractories have an average particle size in the range of 0.1 to 500 μm, preferably in the range of 1 to 200 μm (preferably measured by light scattering according to ISO 13320:2009-10). A suitable refractory material is one that has a melting point at least 200°C above the temperature of the molten metal used in each case, and / or does not react with the molten metal in any way.

[0024] As used herein, the term "refractory material" (a) also includes highly refractory materials.

[0025] Refractory material (a) is selected from refractory materials typically used in refractory coatings, such as quartz, alumina, zirconia, aluminum silicate, non-swelling layered silicates, zirconium silicate, olivine, talc, mica, graphite, coke, feldspar, diatomaceous earth, kaolin, calcined kaolin, metakaolinite, iron oxide, and bauxite.

[0026] The refractory material (a) preferably comprises one or more refractory materials selected from the group consisting of quartz, alumina, zirconia, aluminum silicate, non-swelling layered silicate, zirconium silicate, olivine, talc, mica, graphite, coke, feldspar, diatomaceous earth, kaolin, calcined kaolin, metakaolinite, iron oxide, and bauxite.

[0027] Refractory material (a) is more preferably, -(i) One or more refractories selected from the group consisting of quartz, alumina, zirconia, aluminum silicate, non-swelling layered silicates, zirconium silicate, olivine, talc, mica, graphite, coke, feldspar, diatomaceous earth, kaolin, calcined kaolin, metakaolinite, iron oxide, and bauxite, -(ii) comprising one or more refractories selected from the group consisting of swollen layered silicates and zeolites.

[0028] Swellable layered silicates also function as rheological additives (inorganic thickeners). The swelling layered silicates are preferably selected from the group consisting of smectite, hectorite, saponite, nontronite, vermiculite, and montmorillonite.

[0029] The zeolite may be natural or synthetic.

[0030] The mass ratio of refractory material (i) to refractory material (ii) is preferably in the range of 20:1 to 5:1, more preferably in the range of 15:1 to 7:1.

[0031] For example, refractory material (a) is, -(i) One or more refractories selected from the group consisting of quartz, alumina, zirconia, aluminum silicate, non-swelling layered silicates, zirconium silicate, olivine, talc, mica, graphite, coke, feldspar, diatomaceous earth, kaolin, calcined kaolin, metakaolinite, iron oxide, and bauxite, -(ii) comprising one or more refractories selected from the group of swollen layered silicates.

[0032] For example, refractory material (a) is, -(i) One or more refractories selected from the group consisting of quartz, alumina, zirconia, aluminum silicate, non-swelling layered silicates, zirconium silicate, olivine, talc, mica, graphite, coke, feldspar, diatomaceous earth, kaolin, calcined kaolin, metakaolinite, iron oxide, and bauxite, -(ii) comprising one or more refractories selected from the group of zeolites.

[0033] Refractory material (a) is more preferably, -(i) One or more refractories selected from the group consisting of quartz, alumina, zirconia, aluminum silicate, non-swelling layered silicates, zirconium silicate, olivine, talc, mica, graphite, coke, feldspar, diatomaceous earth, kaolin, calcined kaolin, metakaolinite, iron oxide, and bauxite, -(ii) comprising one or more refractories selected from the group of swollen layered silicates, and one or more refractories selected from the group of zeolites.

[0034] Surprisingly, it has been found that refractories (a), and one or more refractories (i) as defined above, comprising one or more refractories (ii) selected from the group of swollen layered silicates and zeolites, wherein compositions in which the swollen layered silicates are preferably selected from the group of smectite, hectorite, saponite, nontronite, vermiculite, and montmorillonite, achieve a particularly significant reduction in formaldehyde emissions. This was unexpected, as all of the descriptions of some representative refractories (ii) above have so far been for their function as rheological additives.

[0035] In certain cases, or under specific experimental conditions, it is even possible to achieve a significant reduction in formaldehyde emissions using a refractory coating composition that includes the above-described combination of refractories (i) and (ii) but does not contain compound (b) as defined above. See comparative examples using comparative refractory coating compositions that include the above-described combination of refractories (i) and (ii) but do not contain compound (b) as defined above. The mass ratio of refractory (i) to refractory (ii) is preferably in the range of 20:1 to 5:1, more preferably in the range of 15:1 to 7:1.

[0036] Therefore, for the production of a coating on the body of a metal casting mold or core that releases formaldehyde when heated, -(a) One or more refractory particles, wherein refractory material (a) is -(i) One or more refractories selected from the group consisting of quartz, alumina, zirconia, aluminum silicate, non-swelling layered silicates, zirconium silicate, olivine, talc, mica, graphite, coke, feldspar, diatomaceous earth, kaolin, calcined kaolin, metakaolinite, iron oxide, and bauxite. Furthermore -(ii) One or more refractory particles comprising one or more refractory materials selected from the group of swellable layered silicates and zeolites, -(c) The use of a composition comprising, optionally, a carrier liquid selected from the group consisting of water, alkanols, and mixtures thereof, is also described herein. The coating forms the surface of the mold or core that comes into contact with the molten metal during the casting process.

[0037] The carrier liquid (c) simply functions as a vehicle for coating the core or mold body with a suspended and dissolved substance, and is removed during the drying process. The carrier liquid is in liquid form under standard conditions (20°C and 10¹³.25 hPa) and is evaporable at standard pressure (10¹³.25 hPa) at temperatures ranging from 50°C to 200°C. The carrier liquid (c) is preferably selected from the group consisting of water, methanol, ethanol, and isopropanol.

[0038] Compositions for producing fire-resistant coatings are often, -(d) Wetting agent, -(e) Rheological additives, -(f) binder, -(g) Suspension aid, -(h) Contains further components such as biocides.

[0039] Suitable wetting agents (d), rheological additives (e), binders (f), suspension aids (g), and biocides (h), as well as their functions and effects, are known to those skilled in the art.

[0040] The wetting agent (d) used is preferably anionic, cationic, and nonionic surfactants. The wetting agent (d) is preferably selected from the group consisting of surfactants, and more preferably from alkyne diols and their derivatives.

[0041] The rheological additives used are, for example, organic thickeners. These are preferably selected from the group consisting of polysaccharides, proteins, and cellulose ethers. It is also possible to use inorganic thickeners from the group consisting of band silicates such as swollen clay minerals, e.g., palygorskite (atapulgite), and fumed silica. The above-mentioned swollen layered silicates and zeolites also function as inorganic thickeners. However, such inorganic thickeners are refractory and are therefore assigned to component (a) in terms of concentration values.

[0042] The binder (f) used is either a self-curing binder in air or a binder that dries upon removal of the carrier liquid (c). Preferred binders (f) are selected from the group consisting of polyvinyl alcohol, polyacrylate, polyvinyl acetate, copolymers of the aforementioned polymers, natural resins, dextrin, starch, and peptides.

[0043] The suspension aid (g) is preferably selected from the group consisting of salts of metals soluble in the carrier liquid (c), including alkali metals, alkaline earth metals, iron, and aluminum, as well as mixtures thereof.

[0044] The compositions for use according to the present invention include, as described above, a ready-to-use fire-resistant coating composition and a precursor for forming a ready-to-use fire-resistant coating composition. The ready-to-use fire-resistant coating compositions have a sufficiently high content of carrier liquid so that they can be applied directly to a body to form a coating. In the ready-to-use fire-resistant coating composition, the mass of carrier liquid (c) is preferably 60% to 80% by weight, based on the total mass of the composition. The precursor for making a ready-to-use fire-resistant coating composition contains no carrier liquid (c) (solid mixture) or contains a significantly smaller amount of carrier liquid (c) compared to the ready-to-use fire-resistant coating composition (concentrate). In the concentrate, the total mass of carrier liquid (c) is 40% to 65% by weight, preferably 40% to 59% by weight, in each case, based on the total mass of the composition.

[0045] Ready-to-use fire-resistant coating compositions can be obtained by suspending a solid mixture in a carrier liquid (c) (involving the dissolution of components of the solid mixture that are soluble in the carrier liquid (c)), or by diluting a concentrate with a carrier liquid (c). The concentrate is typically diluted using a carrier liquid (c) having the same composition as the carrier liquid (c) of the concentrate. Therefore, ready-to-use fire-resistant coating compositions are obtained by: - The step of preparing or providing a solid mixture or concentrate as defined above, -This can be produced by a process comprising the step of adding a carrier liquid (c) selected from the group consisting of water, alkanols, and mixtures thereof, wherein the amount of carrier liquid (c) added is such that the total amount of carrier liquid (c) is 60% to 80% by weight, based on the total mass of the resulting composition.

[0046] The above annotations regarding preferred and desirable components (a) to (h) are applicable to concentrates as well as to ready-to-use refractory coating compositions. Regarding solid mixtures, the above annotations regarding preferred and desirable refractories (a), and regarding preferred and desirable components (b) and (d) to (h), are applicable as long as they are solids.

[0047] A second aspect of the present invention relates to a composition for producing a coating on the body of a metal casting mold or core that releases formaldehyde when heated, the coating forming a surface of the mold or core that comes into contact with the molten metal during the casting process. The composition of the present invention is -(a) One or more refractory particles, -(b) at least one ammonium salt [compound (b)], The total mass of compound (b) is 0.1% to 10% by weight, preferably 0.1% to 9% by weight, more preferably 0.1% to 8% by weight, even more preferably 0.1% to 7% by weight, even more preferably 0.1% to 6% by weight, and particularly preferably 0.1% to 5% by weight, based on the total mass of the refractory particles (a), and the compound, -(c) A carrier liquid selected from the group consisting of water, alkanols, and mixtures thereof, wherein the total mass of carrier liquid (c) is 40% to 80% by weight based on the total mass of the composition.

[0048] The same applies to the selection of the refractory material (a), compound (b), carrier liquid (c), and further components (d) and (h) as defined above, as described above, with respect to the first aspect of the present invention. A composition is preferred in which components (a) to (h) are selected from components (a) to (h) that have been identified as preferred with respect to the first aspect of the present invention.

[0049] The compositions of the present invention include a ready-to-use fire-resistant coating composition (as described above in the context of the first aspect of the present invention) and a concentrate for forming a ready-to-use fire-resistant coating composition (as described above in the context of the first aspect of the present invention).

[0050] A further aspect of the present invention relates to a mold or core for metal casting. The mold or core of the present invention is - The main body releases formaldehyde when heated, - A coating disposed on the main body that forms the surface of the mold or core that comes into contact with the molten metal during the casting process, wherein the coating is -(a) One or more refractory particles, -(b) at least one ammonium salt [compound (b)], -and / or its reaction product with formaldehyde, - The total mass of the free compound (b) in the coating and the compound bonded in the reaction product with formaldehyde is 0.1% to 10% by weight, preferably 0.1% to 9% by weight, more preferably 0.1% to 8% by weight, even more preferably 0.1% to 7% by weight, even more preferably 0.1% to 6% by weight, and particularly preferably 0.1% to 5% by weight, based on the total mass of the refractory particles (a).

[0051] The mold or core of the present invention comprises a body and a coating disposed on the body comprising a non-volatile component of the composition for use according to the present invention in a first aspect of the present invention. The same applies to the selection of the refractory material (a) and compound (b) as defined above, as described above, with respect to a first aspect of the present invention. A mold and core having the above-defined coating is preferred, and the refractory material (a) and compound (b) are selected from the components (a) and (b) specified above as preferred for a first aspect of the present invention.

[0052] This coating forms the surface of the mold or core that comes into contact with the molten metal during the casting process. Preferably, the coating has a thickness in the range of 0.05 mm to 0.6 mm, more preferably 0.05 to 0.4 mm, and more preferably 0.1 to 0.3 mm.

[0053] Preferably, the coating not only forms the surface of the mold or core that comes into contact with the molten metal during the casting process, but also extends further over a wider area of ​​the mold or core. Preferably, the coating extends over 50% or more of the surface of the mold or core, more preferably 70% or more, more preferably 80% or more, particularly preferably 90% or more, and especially particularly 95% or more. Most preferably, the coating extends over the entire surface of the mold or core.

[0054] The mold or core body of the present invention releases formaldehyde when heated. At least a significant proportion of the formaldehyde released by the body is combined with compound (b) present in the coating to form a non-volatile reaction product. Thus, the coating contains compound (b) (particularly before drying) and / or its reaction product with formaldehyde (formed during drying).

[0055] The mold or core body is typically formed from a mixture of molding materials bound together with a binder that releases formaldehyde when heated. The binder is present in a cured form in the mold or core body. The same applies to the selection of the binder as described above with respect to the first aspect of the present invention. A binder selected from the binders identified as preferred with respect to the first aspect of the present invention is preferred. The binder is more preferably, -Polyurethane formed by polyaddition of phenol-formaldehyde resin and polyisocyanate. -Phenol-formaldehyde resin, -Fran-formaldehyde resin, -Urea-formaldehyde resin, - Melamine-formaldehyde resin, - Selected from the group consisting of any combination mentioned above.

[0056] A fourth aspect of the present invention relates to a process for producing a mold or core of the present invention for metal casting. The process is as follows: - Steps of manufacturing or providing the main body, - The step of preparing or providing a ready-to-use fire-resistant coating composition as defined above, - The process includes the steps of applying a ready-to-use fire-resistant coating composition to the body and then drying it to form a coating on the body, wherein the coating forms the surface of the mold or core that comes into contact with the molten metal during the casting process.

[0057] In the process of the present invention, a coating containing the non-volatile components of the composition for use according to the present invention in a first aspect of the present invention is fabricated on the body of the mold or core. This coating forms the surface of the mold or core that comes into contact with the molten metal during the casting process.

[0058] Preferably, the coating not only forms the surface of the mold or core that comes into contact with the molten metal during the casting process, but also extends further over a wider area of ​​the mold or core. Preferably, the coating extends over 50% or more of the surface of the mold or core, more preferably 70% or more, more preferably 80% or more, particularly preferably 90% or more, and especially particularly 95% or more. Most preferably, the coating extends over the entire surface of the mold or core.

[0059] The fabrication of the mold or core body typically involves the following steps: - A step of preparing or providing a molding material mixture comprising one or more mold base materials and a binder that releases formaldehyde when heated, - A step of molding the molding material mixture, - A step of curing the binder in the molded molding material mixture to form the body of the mold or core.

[0060] Corresponding molding material mixtures, molding methods, and curing methods are known to those skilled in the art.

[0061] The binder in the molding material mixture is preferably, - A two-component system comprising a phenol-formaldehyde resin and a polyisocyanate for forming polyurethane. -A two-component system comprising an aqueous solution of alkaline phenol-formaldehyde resin and an ester-based liquid curing agent. - Preferably, the formaldehyde condensation resin is selected from the group consisting of phenol-formaldehyde resin, furan-formaldehyde resin, urea-formaldehyde resin, and melamine-formaldehyde resin, or any combination thereof.

[0062] The binder is more preferably, -Polyurethane formed by polyaddition of phenol-formaldehyde resin and polyisocyanate. -Phenol-formaldehyde resin, -Fran-formaldehyde resin, -Urea-formaldehyde resin, - Melamine-formaldehyde resin, - Selected from the group consisting of any combination mentioned above.

[0063] The process of the present invention is preferred in which the core or mold body is manufactured by a cold box process. The cold box process is known to those skilled in the art. This process uses a two-component system comprising a phenol-formaldehyde resin and a polyisocyanate as a binder. The binder components come into contact with each other only during the manufacturing process of the molding material mixture, forming polyurethane in the molded molding material mixture. The binder in the molded molding material mixture is cured by contacting the molded molding material mixture with a gaseous tertiary amine or a mixture of two or more gaseous tertiary amines.

[0064] The ready-to-use fire-resistant coating composition used in the process of the present invention is preferably selected from ready-to-use fire-resistant coating compositions containing preferred components (a) to (c) in the first aspect of the present invention, and optionally, preferred components (d) to (h) in the first aspect of the present invention.

[0065] Ready-to-use fire-resistant coating compositions are typically applied to the body by a process selected from the group consisting of spraying, dipping, flow coating, and painting, preferably by dipping. This is because this process is particularly suitable for forming a coating that extends over the entire surface of the mold or core, or at least a large portion of the entire surface of the mold or core.

[0066] The fire-resistant coating composition to be applied is dried at a temperature of 40°C or higher, preferably in the range of 50°C to 200°C, and preferably in the range of 100°C to 150°C.

[0067] The mold or core body releases formaldehyde during drying. At least a significant proportion of the formaldehyde released by the body is bound by compound (b) present in the coating to form a non-volatile reaction product, thus significantly reducing the amount of formaldehyde released into the environment during the drying process of the mold or core.

[0068] A fifth aspect of the present invention relates to the use of at least one ammonium salt (compound (b)) as a formaldehyde scavenger in a coating on the body of a mold or core for metal casting that releases formaldehyde when heated, wherein the coating forms a surface of the mold or core that comes into contact with a molten metal during the casting process, or to a composition for making such a coating (a ready-to-use refractory coating composition as described above in the context of the first aspect of the present invention), or to a composition for making such a composition.

[0069] Preferably, the coating not only forms the surface of the mold or core that comes into contact with the molten metal during the casting process, but also extends further over a wider area of ​​the mold or core. Preferably, the coating extends over 50% or more of the surface of the mold or core, more preferably 70% or more, more preferably 80% or more, particularly preferably 90% or more, and especially particularly 95% or more. Most preferably, the coating extends over the entire surface of the mold or core.

[0070] A formaldehyde scavenger is understood to mean a compound that can react with formaldehyde to produce non-volatile reaction products, and thus reduce the release of formaldehyde into the environment.

[0071] The same applies to the selection of compound (b) as defined above, as described above with respect to the first aspect of the present invention. Compound (b) selected from the above compound (b) identified as preferred with respect to the first aspect of the present invention is preferred.

[0072] In the case of the use of compound (b) in a fifth aspect of the present invention, the coating or composition for producing such coating is -(i) One or more refractories selected from the group consisting of quartz, alumina, zirconia, aluminum silicate, non-swelling layered silicates, zirconium silicate, olivine, talc, mica, graphite, coke, feldspar, diatomaceous earth, kaolin, calcined kaolin, metakaolinite, iron oxide, and bauxite, -(ii) Preferably, optionally further comprising one or more refractories selected from the group consisting of swollen layered silicates and zeolites.

[0073] The same applies to the selection of refractories (i) and (ii) as described above with respect to the first aspect of the present invention.

[0074] A sixth aspect of the present invention relates to a kit for making a mold or core for metal casting, according to the third aspect of the present invention as defined above. The kit of the present invention is -(A) A composition described above with respect to a first aspect of the present invention, preferably a solid mixture described above in the context of a first aspect of the present invention or a concentrate described above in the context of a first aspect of the present invention, -(B) A binder that releases formaldehyde when heated, Components (A) and (B) are separated from each other within the kit.

[0075] In the kit of the present invention, there is no possibility of the components of component (A) coming into contact with the components of component (B), for example, component (A) is provided in one container and component (B) in the other, in separate containers, or component (A) is provided in one container and component (B) in the other, in separate chambers of a container.

[0076] In the kit of the present invention, composition (A) is preferably selected from solid mixtures and concentrates containing preferred components (a) and (b) in the first embodiment of the present invention, and optionally (c) to (h).

[0077] In the kit of the present invention, the binder (B) is preferably, - A two-component system comprising a phenol-formaldehyde resin and a polyisocyanate for forming polyurethane. -A two-component system comprising an aqueous solution of alkaline phenol-formaldehyde resin and an ester-based liquid curing agent. - Preferably, the formaldehyde condensation resin is selected from the group consisting of phenol-formaldehyde resin, furan-formaldehyde resin, urea-formaldehyde resin, and melamine-formaldehyde resin, or any combination thereof.

[0078] The binder is more preferably, -Polyurethane formed by polyaddition of phenol-formaldehyde resin and polyisocyanate. -phenol-formaldehyde resin, and - Selected from the group consisting of furan-formaldehyde resins.

[0079] The present invention will be described below with reference to examples. [Examples]

[0080] Herein, the present invention will be described in more detail with reference to the following examples, which are merely illustrative and not intended to limit the scope of the invention. The following coating compositions are described in terms of their application to cores, for the sake of ease of testing. The coating compositions exhibit the same performance when applied to molds.

[0081] Measurement of formaldehyde content As detailed below, the coating composition was applied to the core to form a coating. Subsequently, the core was dried at a temperature of 250°C in a drying cabinet (Heraeus T5028 oven).

[0082] During drying, samples were taken from the oven air at specific times using a probe, and their formaldehyde content was determined by the Gasmet and Hach Lange methods. This method is further outlined below.

[0083] The formaldehyde content was measured using a Gasmet analyzer, which determines and quantifies the components in the gas stream at the oven's exhaust. The smoke released from the oven during drying was collected in two gas washing bottles, each filled with 50 ml of demineralized water, and the concentration was measured from a total of 100 ml. The maximum temperature of the gas stream was 180°C.

[0084] In the experiments conducted, each measurement lasted approximately 60 minutes, and the measured temperature was 150°C.

[0085] If necessary, use the following formula to determine the result obtained in ppm as mg / m³ 3 It can be converted to:

[0086] Conversion from ppm to mg / m 3 to [mg / m 3 = [ppm] * Mw * 0.0409 [mg / m 3 = mg / m 3 concentration at [ppm] = concentration in ppm, Mw = molar mass of the relevant gas in g / mol 0.0409 = conversion factor to m of air moles 3

[0087] Next, convert the gas concentration to the gas concentration per gram of sample 1 by plotting a graph of the concentration per gram of sample 1 against time. Then, the average gas concentration per gram of sample 1 and the maximum gas concentration per gram of sample 1 over the desired time frame can be determined.

[0088] Calculation of the total amount of emitted gas m(gas) = average [mg / m 3 g] * test time * flow rate / 1000 m(gas) = mass of emitted gas per gram of sample 1 average [mg / m 3 g] = average concentration per gram of sample 1 test time = (minutes) flow rate = 4 L / min conversion of liters to m 3 = 1000

[0089] <000037​​​​​​​​​​​​​​​The following sections detail how the coating compositions according to the present invention were prepared. Table 1 shows the various component parts (a-h) in the compositions of the present invention and their respective amounts. The examples relate to the preparation of cores, but they can equally be applied to the preparation of molds. [Table 1] [Table 2] [Table 3]

[0092] In each of Examples E3 to E9c, the layer thickness of the coating composition applied to the core was between 225 μm and 278 μm. If the thickness was less than 225 μm, the coating contained too much carrier liquid (e.g., water) and needed to be more concentrated. If the thickness was greater than 278 μm, more carrier liquid was required. The applicant noted that the coatings prepared with ammonium chloride and ammonium citrate remained unchanged even after 6 months.

[0093] Table 3 shows a comparative overview of the layer thickness and formaldehyde concentration of the compositions of the present invention (E8a to E9c) and comparative examples (E1 to E7). [Table 4]

[0094] These results demonstrate that the NH2 group functions as an effective formaldehyde scavenger. In this specification, the applicant has found that ammonium citrate and ammonium chloride yield comparable, if not superior, results in reducing formaldehyde production during combustion compared to prior art and commercially available formaldehyde scavengers. E8a (ammonium citrate) and E9a (ammonium chloride) are present at 0.03 and 0.04 mg / m³ at 3.9% by weight, respectively. 3It produces 0.04 mg / m³ of formaldehyde, but Examples E5-E7 produce 0.04-0.09 mg / m³ of formaldehyde with the same weight % of scavenger component. 3 It produces 0.g of formaldehyde. Furthermore, the applicant found that when ammonium citrate or ammonium chloride is used as a formaldehyde scavenger in coatings for cores or molds, there are no casting defects compared to coatings using prior art or commercially available formaldehyde scavengers.

[0095] It appears that higher concentrations of ammonium citrate or ammonium chloride increase formaldehyde removal, and therefore, lower concentrations of formaldehyde produced.

[0096] Ammonium chloride as a scavenger yields particularly interesting results, especially in terms of price. Both ammonium chloride and ammonium citrate are significantly cheaper than other scavengers currently available. Therefore, even though more ammonium chloride or ammonium citrate may be needed to achieve the same level of formaldehyde removal, they remain inexpensive alternatives compared to other prior art or commercially available formaldehyde scavengers. More importantly, ammonium chloride and ammonium citrate have low toxicity during use and thus reduce the health risk to users.

[0097] The applicant found that by using ammonium chloride or ammonium citrate as a formaldehyde scavenger, comparable, if not superior, results can be achieved to those of prior art or commercially available scavengers. Furthermore, the applicant found that ammonium chloride and ammonium citrate provide a longer-lasting coating and, therefore, a longer-lasting scavenging effect. Thus, the applicant has found alternative formaldehyde scavengers that offer significant advantages over the current state of affairs in the art. These alternative scavengers help reduce formaldehyde concentrations to the lowest levels currently known, but are less expensive, longer-lasting, and more user-friendly.

[0098] The use of certain compounds as formaldehyde scavengers in coatings on the bodies of metal casting molds or cores that release formaldehyde when heated, wherein the coating forms the surface of the mold or core that comes into contact with the molten metal during the casting process, and the use of compositions comprising one or more of these compounds for the preparation of coatings on the bodies of metal casting molds or cores that release formaldehyde when heated, wherein the coating forms the surface of the mold or core that comes into contact with the molten metal during the casting process, are described herein and illustrated by the above examples. Corresponding molds and cores, as well as their preparation, are also described.

Claims

1. A composition for creating a coating on the body of a metal casting mold or core that releases formaldehyde when heated, wherein the coating forms the surface of the mold or core that comes into contact with the molten metal during the casting process, and the composition (a) One or more refractory particles, (b) at least one ammonium salt [compound (b)], The total mass of compound (b) is 0.1% by weight to 10% by weight, based on the total mass of the refractory particles (a), and (c) A composition comprising, optionally, a carrier liquid selected from the group consisting of water, alkanols, and mixtures thereof.

2. The composition according to claim 1, wherein the total mass of the carrier liquid (c) is 40% by weight to 80% by weight, based on the total mass of the composition.

3. The above at least one ammonium salt is of formula (R) ４ N ＋ A － It is an ammonium salt of, where R is hydrogen, C １－４ The composition according to claim 1 or 2, wherein A is an anion selected from the group consisting of alkyl and phenyl, and A is an anion selected from the group consisting of trifluoroacetate, acetate, benzenesulfonate, benzoate, bicarbonate, bitartrate, bromide, carbonate, chloride, citrate, dihydrochloride, formate, hydrobromide, hydrochloride, methyl sulfate, nitrate, oxalate, phosphate, and sulfate.

4. The aforementioned refractory material (a) (i) One or more refractories selected from the group consisting of quartz, alumina, zirconia, aluminum silicate, non-swelling layered silicates, zirconium silicate, olivine, talc, mica, graphite, coke, feldspar, diatomaceous earth, kaolin, calcined kaolin, metakaolinite, iron oxide and bauxite, (ii) comprising one or more refractories selected from the group consisting of swellable layered silicates and zeolites, and / or The composition according to any one of claims 1 to 3, wherein the carrier liquid (c) is selected from the group consisting of water, methanol, ethanol, isopropanol, and mixtures thereof.

5. A mold or core for metal casting, comprising a body that releases formaldehyde when heated, and a coating disposed on the body that forms the surface of the mold or core that comes into contact with molten metal during the casting process, wherein the coating is (a) One or more refractory particles, (b) at least one ammonium salt [compound (b)], and / or its reaction product with formaldehyde, A mold or core for metal casting, wherein the total mass of the free compound (b) in the coating and the compound bonded in the reaction product with formaldehyde is 0.1% to 10% by weight, based on the total mass of the particles (a) in the refractory material.

6. The above at least one ammonium salt is of formula (R) ４ N ＋ A － It is an ammonium salt of, where R is hydrogen, C １－４ A metal casting mold or core according to claim 5, wherein A is an anion selected from the group consisting of alkyl and phenyl, and A is an anion selected from the group consisting of trifluoroacetate, acetate, benzenesulfonate, benzoate, bicarbonate, bitartrate, bromide, carbonate, chloride, citrate, dihydrochloride, formate, hydrobromide, hydrochloride, methyl sulfate, nitrate, oxalate, phosphate, and sulfate.

7. The aforementioned refractory material (a) (i) One or more refractories selected from the group consisting of quartz, alumina, zirconia, aluminum silicate, non-swelling layered silicates, zirconium silicate, olivine, talc, mica, graphite, coke, feldspar, diatomaceous earth, kaolin, calcined kaolin, metakaolinite, iron oxide and bauxite, (ii) A mold or core for metal casting according to claim 5 or 6, comprising one or more refractories selected from the group consisting of swellable layered silicates and zeolites.

8. The mold or core body is formed from a molding material mixture bonded with at least one binder that releases formaldehyde when heated, and the binder is - A polyurethane formed by polyaddition of phenol-formaldehyde resin and polyisocyanate, and A mold or core for metal casting according to any one of claims 5 to 7, selected from the group consisting of phenol-formaldehyde resin, furan-formaldehyde resin, urea-formaldehyde resin, and melamine-formaldehyde resin, or any combination thereof, a formaldehyde condensation resin.

9. The mold or core for metal casting according to any one of claims 5 to 8, wherein the coating has a thickness in the range of 0.05 mm to 0.6 mm.

10. A method for producing a coating on the body of a mold or core for metal casting, On the main body of the metal casting mold or core, (a) One or more refractory particles, (b) at least one ammonium salt [compound (b)], The total mass of compound (b) is 0.1% to 10% by weight, based on the total mass of the refractory particles (a), and is an ammonium salt. (c) optionally comprising applying a composition comprising a carrier liquid selected from the group consisting of water, alkanols, and mixtures thereof, The mold or core releases formaldehyde when heated, A method wherein the coating forms the surface of the mold or core that comes into contact with the molten metal during the casting process.

11. wherein the at least one ammonium salt has the formula (R) ４ N ＋ A － where R is selected from the group consisting of hydrogen, C １－４ alkyl, and phenyl, and A is an anion selected from the group consisting of trifluoroacetate, acetate, benzenesulfonate, benzoate, bicarbonate, hydrogen tartrate, bromide, carbonate, chloride, citrate, dihydrochloride, formate, hydrobromide, hydrochloride, methyl sulfate, nitrate, oxalate, phosphate, and sulfate, the method according to claim 10

12. The aforementioned refractory material (a) (i) One or more refractories selected from the group consisting of quartz, alumina, zirconia, aluminum silicate, non-swelling layered silicates, zirconium silicate, olivine, talc, mica, graphite, coke, feldspar, diatomaceous earth, kaolin, calcined kaolin, metakaolinite, iron oxide and bauxite, (ii) comprising one or more refractories selected from the group consisting of swellable layered silicates and zeolites, and / or The method according to claim 10 or 11, wherein the carrier liquid (c) is selected from the group consisting of water, methanol, ethanol, and isopropanol.

13. The method according to any one of claims 10 to 12, wherein the total mass of the carrier liquid (c) is 40% by weight to 80% by weight in each case, based on the total mass of the composition.

14. The mold or core body is formed from a molding material mixture bonded with at least one binder that releases formaldehyde when heated, and the binder is - A polyurethane formed by polyaddition of phenol-formaldehyde resin and polyisocyanate, and The method according to any one of claims 10 to 13, selected from the group consisting of phenol-formaldehyde resin, furan-formaldehyde resin, urea-formaldehyde resin, and melamine-formaldehyde resin.

15. The use of at least one ammonium salt (compound (b)) as a formaldehyde scavenger in a coating on the body of a metal casting mold or core that releases formaldehyde when heated, wherein the coating forms the surface of the mold or core that comes into contact with a molten metal during the casting process, or in a composition for making such a coating, or for making such a composition.

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