Mould material mixture having improved flowability

A process for producing a casting mould or a casting core for metal processing comprising at least the following steps:

• providing a refractory base moulding material;
• providing a binder by dissolving at least one anionic surfactant in water glass, wherein the anionic surfactant comprises a non-polar, hydrophobic portion and a sulphate group, wherein the non-polar, hydrophobic portion is an alkyl group having more than 6 carbon atoms;
• providing separate from the binder a particulate metal oxide comprising amorphous silicon dioxide;
• obtaining a mould material mixture by mixing at least the refractory base moulding material, the binder and the particulate metal oxide, wherein the anionic surfactant is contained in the mould material mixture from 0.001 to 1% by weight relative to the weight of the refractory base moulding material;
• transferring the mould material mixture into a core shooting machine;
• moulding of the mould material mixture into a shape in the core shooting machine to form a moulded mould material mixture;
• and
• curing of the moulded mould material mixture by heating the moulded mould material mixture in the core shooting machine by blowing heated air into the core shooting machine to obtain the casting mould or the casting core having a flexural hot strength increased by at least 10%, a flexural strength after storage under humid atmosphere increased by at least 20%, and a compaction core weight increased by at least 1%, when compared to a cured casting mould or casting core produced by the same process but without both anionic surfactant and amorphous silicon dioxide.