110mm soil pipe

Got a toilet which has 110mm soil pipe going outside the exterior wall. The hole on the inner wall is oversized and needs filling. Can I stick expanding foam into this hole? Does expanding foam degrade the soil pipe wall?

With reference to the attached picture, if the adaptor is pushed all the way down then it is around 15mm below the top of the pipe, slightly exposing the rubber seal. Of course i can lift the adaptor up so that it is level, but wonder if this movement is an issue? TIA