What is described is the use of a particulate material comprising, as its sole constituent or as one of multiple constituents, a particulate synthetic amorphous silicon dioxide having a particle size distribution with a median in the range from 0.1 to 0.4 ?m, determined by means of laser scattering, as additive for a molding material mixture at least comprising: a refractory mold base material having an AFS grain fineness number in the range from 30 to 100, particulate amorphous silicon dioxide having a particle size distribution with a median in the range from 0.7 to 1.5 ?m, determined by means of laser scattering, and water glass, for increasing the moisture resistance of a molding producible by hot curing of the molding material mixture. Also described are corresponding processes, mixtures and kits.

The invention relates to core-shell particles for use as a filler for feeder compositions for producing feeders, comprising (a) a core which possesses one or more cavities and a wall surrounding these cavities, where the core (a) has an average diameter in the range from 0.15 to 0.45 mm, (b) a shell enclosing the core and consisting of or comprising (b1) particles comprising or consisting of a material from the group consisting of calcined kaolin or cordierite, where the particles (b1) have a d10 of at least 0.05 m and a d90 of at most 45 m, and also (b2) a binder which binds the particles (b1) to one another and to the core (a).

A foundry sand comprises a blend that includes a silica sand and a zircon aggregate. The zircon aggregate exhibiting a sharp rise in linear thermal expansion coefficient in a temperature band above 1200 C. A method of casting an article in molten metal at a temperature above 1200 C. includes forming a single or multi-part mold for the article from the above-described foundry sand, admitting molten metal to the mold at a temperature such that at least one or more regions of the foundry sand in contact with the admitted metal are heated to a temperature within the temperature band, and cooling the mold and metal to obtain a cast article.

A foundry sand comprises a blend that includes a silica sand and a zircon aggregate. The zircon aggregate exhibiting a sharp rise in linear thermal expansion coefficient in a temperature band above 1200 C. A method of casting an article in molten metal at a temperature above 1200 C. includes forming a single or multi-part mold for the article from the above-described foundry sand, admitting molten metal to the mold at a temperature such that at least one or more regions of the foundry sand in contact with the admitted metal are heated to a temperature within the temperature band, and cooling the mold and metal to obtain a cast article.

Compositions useful for foundry processes such as green sand casting are discussed. The compositions may comprise an aggregate, at least one inorganic binding agent, and at least one high aspect ratio silicate. For example, the composition may comprise sand, one or more clay materials serving as a binding agent, and a high aspect ratio silicate chosen from mica, talc, or a combination thereof. The composition may be formed into a green sand mold for use in casting molded articles. Incorporation of the high aspect ratio silicate may help to improve the quality of the casted article.

Compositions useful for foundry processes such as green sand casting are discussed. The compositions may comprise an aggregate, at least one inorganic binding agent, and at least one high aspect ratio silicate. For example, the composition may comprise sand, one or more clay materials serving as a binding agent, and a high aspect ratio silicate chosen from mica, talc, or a combination thereof. The composition may be formed into a green sand mold for use in casting molded articles. Incorporation of the high aspect ratio silicate may help to improve the quality of the casted article.

A surfactant composition for a formed sand, said surfactant composition contains a compound (A) represented by the following formula (1) and a compound (B) represented by the following formula (2). The content of the compound (A) is 25 to 85 mass % and content of the compound (B) is 15 to 75 mass %, provided that a total mass of the compound (A) and compound (B) is defined as 100 mass %:

R.sup.1O-(EO).sub.aSO.sub.3M.sup.1(1)

wherein R.sup.1 represents a hydrocarbon group having 6 to 22 carbon atoms, EO represents oxyethylene group, a is 1 to 10, and M1 represents an alkali metal, alkaline earth metal, ammonium or an organic ammonium,

R.sup.2CONR.sub.3C.sub.2H.sub.4SO.sub.3M.sup.2(2)

wherein R.sup.2CO represents a fatty acyl group having 6 to 22 carbon atoms, R.sup.3 represents hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and M.sup.2 represents an alkali metal, an alkaline earth metal, ammonium or an organic ammonium.

A surfactant composition for a formed sand, said surfactant composition contains a compound (A) represented by the following formula (1) and a compound (B) represented by the following formula (2). The content of the compound (A) is 25 to 85 mass % and content of the compound (B) is 15 to 75 mass %, provided that a total mass of the compound (A) and compound (B) is defined as 100 mass %:

R.sup.1O-(EO).sub.aSO.sub.3M.sup.1(1)

wherein R.sup.1 represents a hydrocarbon group having 6 to 22 carbon atoms, EO represents oxyethylene group, a is 1 to 10, and M1 represents an alkali metal, alkaline earth metal, ammonium or an organic ammonium,

R.sup.2CONR.sub.3C.sub.2H.sub.4SO.sub.3M.sup.2(2)

wherein R.sup.2CO represents a fatty acyl group having 6 to 22 carbon atoms, R.sup.3 represents hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and M.sup.2 represents an alkali metal, an alkaline earth metal, ammonium or an organic ammonium.

The present invention relates to the use of closed-pore microspheres of expanded perlite as a filler for producing moldings for the foundry industry, to a composition for producing moldings for the foundry industry, comprising closed-pore microspheres of expanded perlite as a filler, and a binder, the binder being selected from the group consisting of water glass, phenol-formaldehyde resins, two-component systems comprising as reactants a polyisocyanate and a polyol component containing free hydroxyl groups (OH groups), and starch, and also to moldings for the foundry industry and to a process for producing a molding for the foundry industry.

The present invention relates to the use of closed-pore microspheres of expanded perlite as a filler for producing moldings for the foundry industry, to a composition for producing moldings for the foundry industry, comprising closed-pore microspheres of expanded perlite as a filler, and a binder, the binder being selected from the group consisting of water glass, phenol-formaldehyde resins, two-component systems comprising as reactants a polyisocyanate and a polyol component containing free hydroxyl groups (OH groups), and starch, and also to moldings for the foundry industry and to a process for producing a molding for the foundry industry.