Paper heat-sealing barrier

The present invention relates to a paper comprising: - a fibrous substrate, - a pre-layer comprising a binder and a filler mixture (s) lamellar (s) form factor of at least 15 and filler (s) finer (s ) whose particle size is 80% by weight less than 2 microns (measured by the method Sedigraph ISO13317-3), - at least one cover layer applied on the base coat, the paper having a permeability to water vapor at most 150 g / m2 / 24h and preferably less than 100g / m2 / 24h, measured according to standard aS TM F1249 in so-called tropical conditions of 38 ° C and 90% relative humidity