Investment casting shell composition binders comprising hydrophilic fibrils having an average diameter between about 1 nm and about less than 1 μm can be used for the preparation of investment casting shell compositions or slurries. The investment casting shell binders and compositions can be used in an investment casting process to produce investment casting shells with improved shell build thickness and strength.

Molding material mixes that contain a polyurethane binder based on phenolic resins of the benzyl ether type and polyisocyanates are characterized by the inclusion of a polybutadiene derivative. In one case, the polybutadiene derivative has epoxide groups and hydroxyl groups. In another case, the polybutadiene derivative has succinic acid anhydride groups. Molds, cores and risers are produced using these molding material mixes. Inclusion of the polybutadiene derivatives results in a reduction of sand adhesions in the molding process.

Molding material mixes that contain a polyurethane binder based on phenolic resins of the benzyl ether type and polyisocyanates are characterized by the inclusion of a polybutadiene derivative. In one case, the polybutadiene derivative has epoxide groups and hydroxyl groups. In another case, the polybutadiene derivative has succinic acid anhydride groups. Molds, cores and risers are produced using these molding material mixes. Inclusion of the polybutadiene derivatives results in a reduction of sand adhesions in the molding process.

Investment casting shell composition binders comprising hydrophilic fibrils having an average diameter between about 1 nm and about less than 1 ?m can be used for the preparation of investment casting shell compositions or slurries. The investment casting shell binders and compositions can be used in an investment casting process to produce investment casting shells with improved shell build thickness and strength.