Abstract: A mold for casting particularly a core, is produced by mixing refractory particles with colloidal alumina to give a slurry, filling said slurry in a pattern having water absorption properties, solidifying the slurry, followed by drying and firing. The resulting mold, particularly core, has high dimensional accuracy with no cracks.

Abstract: A method of producing a vibration attenuating material having the steps of forming a multiplicity of grooves in the surface of a ductile raw material and subjecting the raw material to a drawing or rolling work to form a multiplicity of minute friction interfaces in the surface region of the vibration attenuating material. An improved vibration attenuating performance is ensured by a suitable selection of numerical values of factors such as relationship between the maximum depth of the friction interface and the thickness of the vibration attenuating material, pitch of the friction interfaces and so forth.

Abstract: In a mold to be hardened by a CO.sub.2 gas, a mold binder material comprising a combination of polymers containing carboxyl groups, at least one of multi-valent metal oxides and multi-valent metal hydroxides, and resins of polyvinyl alcohol group, and at least one of sodium salt of gluconic acid and polyhydric alcohols or a mold binder material comprising a combination of polymers having carboxyl groups, at least one of multi-valent metal oxides and multi-valent metal hydroxides, and at least one of sodium salt of gluconic acid and polyhydric alcohols is provided.

Abstract: A mold with an increased compression strength and a good collapsibility is prepared with a good efficiency by mixing refractory particles with a binder material comprising a caustic alkali-neutralized product of a copolymer containing a carboxyl group and calcium hydroxide, thereby preparing molding materials, filling the molding materials around a pattern, and blowing CO.sub.2 gas into the mold sand, thereby hardening the molding materials. Polyvinyl alcohol, calcium oxide, at least one hydroxide of zinc, aluminum, barium, magnesium, and iron, SBR latex, etc. can be added to the binder material, when desired.

Abstract: Particulate material for forming molds produced by mixing particulate refractory material with one material selected from the group consisting of colloidal silica, colloidal alumina, colloidal zirconia and ethyl silicate, drying the mixture and allowing same to set, and crushing the dried mixture into particulate form again. The particulate material includes refractory particles provided with a coat of silica or alumina or zirconia on the surface and increases the strength and surface precision of a mold.