Silicic ester modified phenol/formaldehyde novolaks and their use for the production of resin coated substrates

摘要

This invention relates to a resin preparable by reaction of a phenol/formaldehyde novolak with tetraethyl orthosilicate in a mass ratio above 28 : 1, wherein the phenol of the phenol/formaldehyde novolak is substituted or unsubstituted hydroxybenzene or a mixture of two or more such phenols, and to a particulate material coated with said resin. Said particles can be used e.g. in the shell molding process for the production of shell molds and shell cores; and as proppants for use in the hydraulic fracturing process.