Core-sheath particle for use as a filler for feeder masses

Feeder comprising a cured feeder composition,

• said cured feeder composition comprising:
• a multitude of core-sheath particles being resistant up to a temperature of at least 1500° C.,
• wherein said core-sheath particles comprise:
• (a) a carrier core which has a size within a range of from 30 μm to 500 μm and is formed of a material which is resistant up to a temperature of at most 1400° C.
• and does not contain any polystyrene,
• wherein the carrier core (a) consists of glass material and
• wherein the carrier core (a) is a hollow sphere or a porous particle,
• (b) a sheath which encloses the core and consists of or comprises
• (b1) particles having a D50 value for the particle size of at most 10 μm,
• which are resistant up to a temperature of at least 1600° C.,
• wherein the particles (b1) consist of one or more materials selected from the group consisting of aluminum oxide, silicon carbide and mullite
• and
• (b2) a cured binder that binds the particles (b1) to one another and to the carrier core (a), wherein said binder is a polyurethane cold box binder
• and
• a cured binder binding the core-sheath particles together, wherein said binder is identical to the binder (b2).