Method for protecting stone materials from atmospheric agents by means of perfluoropolyether derivatives

Claim 1

A process for protecting marble, stones, tiles, cement, and other similar materials utilized in particular in building works, from the degradation caused by atmospheric agents and pollutants, which process comprises applying to the surfaces of said materials a protective agent selected from perfluoropolyethers having functionalized end groups and belonging to one of the following two groups: (a) products of general formula: Rf--O--(C.sub.3 F.sub.6 O).sub.m (CFXO).sub.n --A (I) wherein Rf is a perfluoroalkyl group having 1 to 3 carbon atoms; (C 3 F 6 O) and (CFXO) are oxyperfluoroalkylene units statistically distributed along the chain, and X is F or CF 3 ; m and n are integers or n is 0, m being always different from 0, and m/n varies from 5 to 40 when n is different from 0; A is group --CFX--COY wherein X is F or CF 3 and Y is OH, OR', NR"R"', wherein R' may be an alkyl group with 1 to 8 carbon atoms, an aromatic or alkylaromatic group, or an aromatic group substituted by polyethoxy groups; R" may be H or an alkyl group containing from 1 to 8 carbon atoms, or a substituted phenyl group; R"' may be H or an alkyl group with 1 to 8 carbon atoms or a substituted phenyl group; the average molecular weight of said product of formula I being from 500 to 10,000; (b) products of general formula: A'--(C.sub.2 F.sub.4 O).sub.p (CF.sub.2 O).sub.q --A' wherein units (C 2 F 4 O) and (CF 2 O) are statistically distributed along the chain; p and q are such integers that p/q varies from 2 to 0.5; A' is --CF 2 --COY; Y is as defined hereinabove; the average molecular weight of the product of formula II being from 1,000 to 20,000.