Cyclic phosphazene compounds and use thereof as additives of perfluoropolyether oils

Cyclic phosphazene compounds of general formula (I):

• wherein:
• Q is a cyclic phosphazene structure
• wherein n′ is an integer equal to 3 or 4, ω=0 or 1, ε=4 or 6, γ=0 or 1, α and β are integers from 0 to 8, δ=0 or 1, with the proviso that:
• when n′=3 and γ=1 then ε=4, α and β are integers from 0 to 5, such that (α+β) is equal to 5;
• δ=1;
• when n′=3 and γ=1 then ε=4, α and β are integers from 0 to 6, such that (α+β) is equal to 6, ω and δ are equal to 0;
• when n′=4 and γ=1 then ε is equal to 6, α and β are integers from 0 to 7, such that (α+β) must be equal to 7 and δ=1;
• when n′=4 and γ=0 then ε is equal to 6, α and β are integers from 0 to 8, such that (α+β) must be equal to 8, ω and δ are equal to 0;
• A is an end group of the —OCF2X, —OC2F4X, —OC3F6X type, wherein X=F, Cl, H;
• Rf and R′f are (per)fluoropolyoxyalkylene chains having a number average molecular weight in the range 280-5,000, and comprising one or more repeating units statistically distributed along the chain selected from (C3F6O);
• (CFYO) wherein Y is F or CF3;
• (C2F4O);
• (CF2(CF2)x′CF2O) wherein x′ is an integer equal to 1 or 2;
• (CR4R5CF2O) wherein R4 and R5 are equal to or different the one from the other and selected between H, Cl and wherein one fluorine atom of the perfluoromethylene unit can optionally be substituted with H, Cl or (per)fluoroalkyl, preferably having from 1 to 4 carbon atoms, provided that when n′=3, γ=0, α=0, then
• the phosphazene compounds have general formula (IIA):
• wherein R′f has structure (a′)-(C3F6O)q(CFYO)r—, wherein q and r are integers and q/r≧2 and a number average molecular weight between 500 and 700, Y=—CF3 and A=—OC3F6Cl.