Process for the protection of stone materials, marble, bricks and concrete from atmospheric agents and pollutants and for the protection of the surface of such materials from the decay caused by mural writings with paints, and the like

Process for protecting materials for building industry and linings, from paints, inks and the like, consisting essentially in applying to the surface of such materials having porosity values not higher than 40%, a coating constituted by a perfluoropolyether or a fluoropolyether having a chain end or both chain ends constituted by a functional group capable of forming a chemical and/or physical bond with the material to be protected;

• wherein such perfluoropolyether contains oxaperfluoroalkylene units selected from the following classes:
• (I) (CF.sub.2 --CF.sub.2 O) and (CF.sub.2 O), such units being randomly distributed throughout the perfluoropolyether chain;
• (II) ##STR37## and (CFXO) wherein X is either F or CF.sub.3, such units being randomly distributed throughout the perfluoropolyether chain;
• (III) (CF.sub.2 --CF.sub.2 O), ##STR38## and (CFXO) wherein X is either F or CF.sub.3, such units being randomly distributed throughout the perfluoropolyether chain
• (IV) ##STR39## (V) (CF.sub.2 --CF.sub.2 --CF.sub.O);
• (VI) ##STR40## wherein:
• R".sub.f is a fluoroalkylene group;
• n' is either 0 or 1;
• a' and b' are integers, and the sum of (a'+b') is equal to or higher than 2;
• (VII) (CF.sub.2 --CF.sub.2 O);
• (VIII) ##STR41## wherein the R'".sub.f groups, which may be either equal to or different from one another, are a fluorine atom or a perfluoroalkyl group;
• and
• (IX) (CF.sub.2 O--CF.sub.2 --CF.sub.2 O);
• and wherein the fluoropolyether contains the following units:
• (X) (CH.sub.2 --CF.sub.2 --CF.sub.O);
• or
• (XI) (CF.sub.2 --CF.sub.2 --CH.sub.2 O).sub.p '--R.sup.iv.sub.f --O--(CH.sub.2 CF.sub.2 --CF.sub.2 O).sub.q ' wherein:
• R.sup.iv.sub.f is a fluoroalkylene group, and p' and q' are zero or integers, and the sum of (p'+q') is equal to or higher than 2;
• such perfluoropolyether or fluoropolyether being used either alone or in admixture with a compound selected from one of the two following classes or with a compound from both these classes;
• (1) 2-30% by weight of polytetrafluoroethylene or a tetrafluoroethylene copolymer containing up to 12 mol % of other perfluorinated monomers, with said homopolymer or copolymer being used in a fine powder form;
• (2) 10-20% by weight of a perfluoropolyether having perfluoroalkyl end groups.