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EP-4739450-A1 - BUILDING MATERIAL MIXTURES CONTAINING ONE OR MORE ALKALINE-EARTH METAL COMPOUNDS AND METHOD FOR THE PRODUCTION OF MOLDS AND CORES

EP4739450A1EP 4739450 A1EP4739450 A1EP 4739450A1EP-4739450-A1

Abstract

The invention relates to building material mixtures comprising a primary building material, water glass, amorphous silicon dioxide and one or more alkaline-earth metal compounds, and to the production of molds and cores, in particular for metal casting.

Inventors

  • CHAMBERLAIN, Sebastian
  • OBERLEITER, MARTIN
  • MÜLLER, RONJA
  • VORRATH, Dennis
  • Jonek, Markus

Assignees

  • ASK Chemicals GmbH

Dates

Publication Date
20260513
Application Date
20240702

Claims (20)

  1. 1. Mixture as building material mixture for the production of molded bodies comprising: - at least 90% by weight of a refractory building material, based on the building material mixture, - 0.1 to 2 wt.%, preferably 0.2 wt.% to 1.0 wt.%, of an amorphous silicon dioxide, based on the refractory building material; and - 0.001 to 0.2% by weight, preferably 0.005 to 0.1% by weight, of an alkaline earth metal compound, based on the refractory building material, wherein the alkaline earth metal compound is selected from the group: Calcium chloride, calcium oxide, calcium hydroxide, calcium sulfate, magnesium sulfate and their mixtures.
  2. 2. Mixture as a building material mixture for the production of molded bodies, comprising: - at least 80% by weight of a refractory building material, based on the building material mixture, - 0.1 to 2% by weight, preferably 0.2 to 1.0% by weight, of an amorphous silicon dioxide, based on the refractory building material; - 0.001 to 0.2% by weight, preferably 0.005 to 0.1% by weight, of an alkaline earth metal compound, based on the refractory building material, wherein the alkaline earth metal compound is selected from the group: Calcium chloride, calcium oxide, calcium hydroxide, calcium sulfate, magnesium sulfate and mixtures thereof; and - a binder comprising water glass.
  3. 3. Kit for the preparation of a building material mixture comprising the following components separately: (B1) a binder, wherein the binder is an aqueous binder comprising at least water glass; and (C1 ) a solid additive package, wherein the solid additive package (C1 ) comprises: - an amorphous silicon dioxide and - an alkaline earth metal compound, wherein the alkaline earth metal compound is selected from the group: Calcium chloride, calcium oxide, calcium hydroxide, calcium sulfate, magnesium sulfate and mixtures thereof in a weight ratio of amorphous silicon dioxide to alkaline earth metal compound of 1:2 to 2000:1, preferably 2:1 to 200:1, wherein the amorphous silicon dioxide and the alkaline earth metal compound are each present as particulate solids in free-flowing form in the solid additive package (C1). or (B2) a binder, wherein the binder is an aqueous binder comprising at least - water glass and - 0.05 to 10 wt.%, preferably 0.25 to 5 wt.%, of an alkaline earth metal compound, based on the binder, wherein the alkaline earth metal compound is selected from the group: calcium chloride, calcium oxide, calcium hydroxide, calcium sulfate, magnesium sulfate and mixtures thereof; and (C2) a solid additive package comprising an amorphous silicon dioxide, wherein the amorphous silicon dioxide is present as a particulate solid in free-flowing form in the solid additive package C2.
  4. 4. Kit according to claim 3 comprising separately further (A) a refractory building material;
  5. 5. Mixture according to at least one of the preceding claims 1 or 2, wherein - the refractory building material, the amorphous silicon dioxide and the alkaline earth metal compound are each present or added as particulate solids in free-flowing form.
  6. 6. Mixture or kit according to at least one of the preceding claims, wherein the components of the refractory building material each have a melting point of greater than 600°C.
  7. 7. Mixture or kit according to at least one of the preceding claims, wherein the refractory building material has a particle size of less than or equal to 600 pm, preferably less than or equal to 500 pm, determined by sieving according to DIN 66165 Part 2.
  8. 8. Mixture or kit according to at least one of the preceding claims, wherein the alkaline earth metal compound has a particle size of less than or equal to 1 mm, preferably less than or equal to 0.5 mm, particularly preferably less than or equal to 0.25 mm, determined by sieving according to DIN 66165 Part 2.
  9. 9. Mixture or kit according to at least one of the preceding claims, wherein the amorphous silicon dioxide has a particle size of less than 300 pm, preferably less than 200 pm, determined by sieving according to DIN 66165 Part 2.
  10. 10. Mixture or kit according to at least one of the preceding claims, wherein the amorphous silicon dioxide has an average primary particle size D50 of 0.05 pm to 10 pm, in particular of 0.1 pm to 5 pm, preferably of 0.1 pm to 2 pm, determined by dynamic light scattering.
  11. 11. Mixture or kit according to at least one of the preceding claims, wherein the amorphous silicon dioxide has a specific surface area of 1 to 200 m 2 /g, preferably of 1 to 50 m 2 /g, particularly preferably of 1 to 30 m 2 /g.
  12. 12. Mixture or kit according to at least one of the preceding claims, wherein the mixture or kit further contains graphite, preferably between 0.1 wt.% and 1.0 wt.%, preferably between 0.15 wt.% and 2 wt.%, based on the refractory building material; and/or between 0.1 wt.% and 1.0 wt.%, preferably 0.15 wt.% and 2 wt.%, based on the binder.
  13. 13. Mixture or kit according to claim 12, wherein the graphite has a particle size of less than or equal to 300 pm, preferably less than or equal to 200 pm, particularly preferably less than or equal to 100 pm, determined by sieving according to DIN 66165 Part 2.
  14. 14. Mixture or kit according to at least one of the preceding claims, wherein the mixture or kit contains a maximum of 0.2 wt.% organic compounds.
  15. 15. Mixture or kit according to at least one of the preceding claims, wherein the water glass has a molar modulus SiO2/M2O of 1.6 to 4.0, preferably 2.0 to less than 3.5, with M equal to lithium, sodium and potassium.
  16. 16. Mixture or kit according to at least one of the preceding claims, wherein the mixture or kit contains 0.5 to 5 wt.% water glass, preferably 1 to 3.5 wt.% water glass, based on the building material, wherein the solids content of the water glass is 25 to 65 wt.%, preferably 30 to 60 wt.%.
  17. 17. Mixture or kit according to at least one of the preceding claims, wherein the mixture or kit further contains surfactants, preferably anionic surfactants and in particular a C6- to C18-alkyl sulfate and/or C6- to C18-alkyl sulfonate.
  18. 18. Mixture or kit according to claim 17, wherein the surfactant is contained in a proportion of 0.001 to 1 wt.%, particularly preferably 0.01 to 0.2 wt.%, based on the weight of the refractory building material.
  19. 19. Mixture or kit according to at least one of the preceding claims, wherein the mixture or kit further contains at least one phosphorus-containing compound, preferably between 0.05 and 1.0% by weight, particularly preferably between 0.1 and 0.5% by weight, based on the weight of the refractory building material.
  20. 20. A process for producing casting moulds or cores comprising: • Providing the mixture or a kit from which the mixture is produced, optionally with the addition of building material, in each case according to at least one of the preceding claims, • Placing the building material mixture into a mold, and • Curing of the building material mixture.

Description

Building material mixtures containing one or more alkaline earth metal compounds and processes for the production of molds and cores The invention relates to building material mixtures for the foundry industry, among others, comprising one or more alkaline earth metal compounds in combination with refractory building materials, amorphous silicon dioxide and water glass, in particular for producing cast pieces made of aluminum. Furthermore, a building material mixture comprising the above components, excluding the water glass-based binder, and a kit comprising separately a liquid component with the water glass-based binder and a solid component comprising at least the amorphous silicon dioxide are the subject of the invention, wherein the alkaline earth metal compound is part of the liquid or the solid component. State of the art Casting molds are essentially made up of cores and molds, which represent the negative molds of the casting to be produced. These cores and molds consist of a refractory material, for example quartz sand, and a suitable binding agent, which gives the casting mold sufficient mechanical strength after it has been removed from the mold. For the sake of simplicity, cores and molds are referred to individually and collectively as casting mold or casting molds below. The building material mixture consisting of the building material and binding agent is preferably in a flowable form so that it can be filled into a suitable hollow mold and compacted there. The binding agent creates a firm bond between the particles of the building material so that the casting mold has the necessary mechanical stability. If the building material mixture, building material mixture or building material is introduced into a mold or mold tool to produce the casting mold, these are also called mold material mixture, mold base material mixture or mold base material. In this case, the term building material mixture, building base material mixture or building base material was chosen because the structure or the casting mold for metal casting can also be produced directly using 3D printing. In this respect, the term building material mixture includes the term molding material mixture, the term building base material mixture includes the term molding base material mixture and the term building base material includes the term molding base material. Casting molds must meet various requirements. During the casting process itself, they must first have sufficient strength and temperature resistance to be able to hold the liquid metal in the cavity formed by one or more casting (partial) molds. After the solidification process has begun, the mechanical stability of the casting is ensured by a solidified metal layer that forms along the walls of the casting mold. The material of the casting mold must now decompose under the influence of the heat given off by the metal in such a way that it loses its mechanical strength, i.e. the cohesion between individual particles of the refractory material is eliminated. Ideally, the casting mold disintegrates again into fine sand, which can be easily removed from the casting. Various methods for producing three-dimensional bodies (structures) by building them up layer by layer are known under the term "rapid prototyping". One advantage of these processes is the ability to produce complex, one-piece bodies with undercuts and cavities. With conventional methods, these bodies would have to be assembled from several individually manufactured parts. Another advantage is that 3D printers are able to produce the bodies directly from the CAD data without the need for molds. The 3-dimensional (3D) printing processes result in new requirements for binders that hold the mold together when the binder or a binder component is to be applied through the nozzles of a print head. The binders must not only lead to a sufficient level of strength and good disintegration properties after metal casting, as well as sufficient thermal and storage stability, but must also be "printable", i.e. on the one hand, the nozzles of the print head must not become clogged by the binder, and on the other hand, the binder should not be able to flow directly out of the print head, but rather form individual droplets. In addition, both process variants require that as few emissions as possible, e.g. in the form of CO2 or hydrocarbons, are generated during the manufacture of the casting molds and during the casting and cooling processes in order to protect the environment and limit the odor nuisance caused by hydrocarbons, mainly aromatic hydrocarbons. In order to meet these requirements, inorganic binders have been developed, the use of which means that emissions of CO2 and hydrocarbons can be avoided or at least significantly minimized during the manufacture of metal molds. However, the use of inorganic binders is often associated with other disadvantages. In comparison to organic binders, inorganic binders have the disad