Use of composition based on at least one polyorganosiloxane cross-linkable by cationic process under UV radiation and an onium borate type photoinitiator as impregnation or anti-adhesive coating on gaskets at engine block/cylinder head interface

摘要

The present invention relates to the use of cross-linkable silicone compositions for fast, economical and simple impregnation and/or varnishing of flat joints such as cylinder head gaskets. More precisely, it relates to the use of silicone compositions cross-linkable under UV radiation, by cationic process and in the presence of specific photoinitiators selected from onium borates or organometallic complexes, of which the borate counter-anions contain at least a boron atom bound to at least a substituted phenyl (Me, F). The silicone liquid precursor is represented by a polydimethylsiloxane (PDMS) substituted with cross-linking functional groups, by cationic process (Gifip) under UV radiation of the epoxy of vinyloxy type. These Gifip are present in the amount of 0.15 to 2.0 equivalents per kg of the PDMS. The invention also relates to the method of impregnating/varnishing flat joints such as cylinder head gaskets using the specific PDMS composition + the photoinitiator of borate type as well as the treated joints and the composition themselves.