Process for producing a metallic casting or a cured shaped part using aliphatic polymers comprising hydroxy groups

A process (i) for producing a metallic casting or (ii) for producing a cured shaped part selected from the group consisting of casting mould, core and feeder for use in the casting of metallic castings, comprising:

• provision or production of a base mould material,
• provision or production of (a) an aqueous mixture comprising one or more aliphatic polymers in each case comprising structural units containing hydroxy groups and having the formula (I)
• —CH2—CH(OH)— (I),
• provision or production of (b) an aqueous mixture comprising one or more acids and/or one or more heat-labile acid precursors as catalyst for etherification of the hydroxy groups of the aliphatic polymer or polymers,
• combining of the base mould material with (a) the aqueous mixture comprising one or more aliphatic polymers and (b) with the aqueous mixture comprising one or more acids and/or one or more heat-labile acid precursors to give a mould material mixture,
• wherein the mould material mixture is free of aromatics and free of phenolic resins,
• shaping of the mould material mixture and
• to effect curing of the shaped mould material mixture to give the cured shaped part,
• heating of the shaped mould material mixture so that
• heat-labile acid precursors present in the mould material mixture decompose with liberation of acid
• and/or
• hydroxy groups of the aliphatic polymer or polymers crosslink with one another in the presence of the acid or acids with etherification of the hydroxy groups,
• and
• removal of water from the heated shaped mould material mixture,
• wherein
• the one or more acids and/or the one or more heat-labile acid precursors are selected from the group consisting of:
• inorganic prone acids which have a pKa of ≤7,
• monoprotic organic protic acids, which have a pKa of ≤7,
• Lewis acids, selected from the group consisting of boron trifluoride and the chlorides and bromides of boron, aluminium, phosphorus, antimony, arsenic, iron, zinc, and tin, and
• salts which can be thermally decomposed to acids, selected from the group consisting of:
• ammonium salts of mineral acids,
• and
• sulphuric acid salts of alkanolamines.