METHOD AND CHEMICAL AGENT FOR CLEANING AND SEALING INNER SPACE OF INSULATED ELECTRIC APPARATUS

摘要

A mineral oil extended polyurethane system comprises the reaction prod. of an isocyanate terminated prepolymer (I) with a polyol in the presence of a mineral oil and a liq. coupling agent for compatibilising the mineral oil with the polyurethane. The system contains 8-45 pts. wt. polyurethane, 25-75 pts. by wt. mineral oil and 10-35 pts. wt. coupling agent. (I) is derived from a cycloaliphatic, aliphatic or aromatic diisocyanate. The polyol is castor oil or a polyether. (I) or the polyol includes a hydroxy-bearing polybutadiene constituent. The coupling agent is a ketone or an ester of an organic diol or diacid. It has b. pt. >220 degrees F, a solubility parameter of 7.0-9.5 and a hydrogen bonding index number of 8.2-8.8 Contaminants such as water are removed from the interior free spaces of an insulated electrical device such as a multiconductor telephone cable by introducing the polyurethane system under pressure and curing it in situ. The system has the advantage that the mineral oil is retained within the cured polyurethane compsn. which has a gel-like consistency. The mineral oil cannot exude to damage the cable insulation.