To provide a binder composition for molding, by which a mold made of aggregate has an excellent resistance to moisture. The binder composition for molding contains a water-soluble binder and at least one kind of lithium salt that is selected from a group of lithium silicate, lithium oxide, lithium hydroxide, lithium carbonate, lithium bromide, lithium chloride, lithium nitrate, and lithium nitrite.

To provide a binder composition for molding, by which a mold made of aggregate has an excellent resistance to moisture. The binder composition for molding contains a water-soluble binder and at least one kind of lithium salt that is selected from a group of lithium silicate, lithium oxide, lithium hydroxide, lithium carbonate, lithium bromide, lithium chloride, lithium nitrate, and lithium nitrite.

A method of reusing core sand includes crushing a core used for casting into granules; heating the granules at a temperature of 300 C. to 550 C.; causing the heated granules to collide against each other such that water glass used as a binder detaches from the core sand; and blowing air into a mixture of the water glass and the core sand, which are detached from each other, such that the core sand is separated and collected from the mixture due to a difference in specific gravity between the water glass and the core sand.

The present invention provides a curing agent for casting a water glass, including an ester and an amorphous silicon dioxide obtained by a thermal decomposition of ZrSiO.sub.4; and the curing agent for casting the water glass does not contain water. According to the present invention, the curing agent for casting the water glass has a strong adhesion-enhancing effect and a long shelf life, and is easy to use.

A description is given of a method for producing a molding material mixture or for producing a molding material mixture and a molding therefrom, preferably casting molds or cores, for use in the foundry industry, where the molding material mixture comprises a mold base material and a solution or dispersion comprising lithium-containing waterglass, comprising the following steps: (1) producing or providing a kit at least comprising as separate components: (K1) an aqueous solution or dispersion comprising waterglass and (K2a) a first waterglass-free solution or dispersion comprising lithium ions in solution in water, and also preferably (K2b) a second waterglass-free solution or dispersion, preferably o comprising lithium ions in solution in water with a lower concentration than in component (K2a), and thereafter (2) producing a mixture of the mold base material with a fraction of component (K1) and with a fraction of component (K2a), and also optionally with a fraction of component (K2b). Further described is an aforementioned kit, more particularly for application in the method of the invention. An installation is specified as well for producing an intermediate solution or dispersion, comprising lithium-containing waterglass, for use in producing a molding material mixture or for producing a molding material mixture and a molding therefrom.

A description is given of a method for producing a molding material mixture or for producing a molding material mixture and a molding therefrom, preferably casting molds or cores, for use in the foundry industry, where the molding material mixture comprises a mold base material and a solution or dispersion comprising lithium-containing waterglass, comprising the following steps: (1) producing or providing a kit at least comprising as separate components: (K1) an aqueous solution or dispersion comprising waterglass and (K2a) a first waterglass-free solution or dispersion comprising lithium ions in solution in water, and also preferably (K2b) a second waterglass-free solution or dispersion, preferably o comprising lithium ions in solution in water with a lower concentration than in component (K2a), and thereafter (2) producing a mixture of the mold base material with a fraction of component (K1) and with a fraction of component (K2a), and also optionally with a fraction of component (K2b). Further described is an aforementioned kit, more particularly for application in the method of the invention. An installation is specified as well for producing an intermediate solution or dispersion, comprising lithium-containing waterglass, for use in producing a molding material mixture or for producing a molding material mixture and a molding therefrom.

A sand mold shaping material contains an aggregate comprising inorganic particles, and microcapsules enclosing a binder which causes the aggregate to bind. The binder is a liquid binder that is in a liquid phase at room temperature, and is enclosed in an outer shell comprising a resin that forms the microcapsule. The sand mold shaping material is in a dry state when used to fill a molding die for shaping.

A sand mold shaping material contains an aggregate comprising inorganic particles, and microcapsules enclosing a binder which causes the aggregate to bind. The binder is a liquid binder that is in a liquid phase at room temperature, and is enclosed in an outer shell comprising a resin that forms the microcapsule. The sand mold shaping material is in a dry state when used to fill a molding die for shaping.

A post-treatment process for increasing the hot strength of a formed part (100) made of particulate material and binder is disclosed, wherein the formed part (100) is formed a part manufactured by 3D printing (S72) and after its manufacture is heated (S30) using a heating device (40), and the heated formed part (100) is exposed (S50) to an atmosphere enriched with gaseous water generated by supplying water.

A post-treatment process for increasing the hot strength of a formed part (100) made of particulate material and binder is disclosed, wherein the formed part (100) is formed a part manufactured by 3D printing (S72) and after its manufacture is heated (S30) using a heating device (40), and the heated formed part (100) is exposed (S50) to an atmosphere enriched with gaseous water generated by supplying water.