Method for constructing molds and cores layer by layer by means of a binder containing water glass, and a binder containing water glass

A method for constructing bodies layer by layer, comprising at least the following steps:

• a) providing a refractory molding base material as a component of a construction material mixture;
• b) spreading a thin layer of the construction material mixture with a layer thickness of 0.05 mm to 3 mm;
• c) printing selected areas of the thin layer with a binder having a dynamic viscosity at 25° C. of greater than 1 mPas and less than 25 mPas, comprising
• water glass in the form of an aqueous alkali silicate solution, the water glass having a molar ratio of Na2O/M2O of greater than 0.4 and a molar modulus SiO2/M2O of greater 1.4 to less than 2.8, wherein M2O is the sum of the mass quantities of lithium, sodium and potassium calculated as oxide;
• and
• at least one phosphate dissolved in the water glass in the form of an aqueous alkali silicate solution, in a molar ratio of P2O5/SiO2 (calculated as P2O5 and relative to SiO2 in the binder) of greater than 0.01 and less than 0.5;
• and
• d) repeatedly repeating steps b) and c).