PRODUCTION OF ELECTRICALLY INSULATING RESIN VARNISH AND PRODUCTION OF INSULATED ELECTRIC/ELECTRONIC PART

PROBLEM TO BE SOLVED: To obtain the subject vanish excellent in heat resistance and capable of providing a set product suitable for e.g. a moisture preventing/electrically insulating use and low in hardness by blending a heat resistant resin obtained by reacting a hydroxy group-containing liquid hydrogenated polyisoprene with a α,β-unsaturated polybasic acid. SOLUTION: This vanish comprises a heat resistant resin obtain by reacting (A) a hydroxy group-containing liquid hydrogenated polyisoprene (pref. having a number average molecular weight of 1,000 to 5,000) with (B) a α,β-unsaturated polybasic acid (e.g. maleic acid or fumaric acid). Pref 0.8 to 1.2 equivalent of the component B is used based on 1 equivalent of hydroxy group of the component A. The heat resistant resin, pref. having an acid value of 5 to 15, is obtained by heating its raw material at 120 to 180 deg.C under the atmosphere of nitrogen. The vanish pref. contains no curing catalyst, and it is pref. mixed with the curing catalyst when used.