Method for transferring heat

1. A process for transferring heat from a heat source to a heat sink, said process comprising using as heat transfer medium a composition comprising:

at least one fluorinated ether fluid free from functional groups (fluid (H-1)), wherein the fluid H-1 is a hydrofluoropolyether fluid (fluid (HPFE)) or a perfluoropolyether fluid (fluid (PFPE)) having a viscosity at 20° C. of less than 10 cSt;

at least one functional (per)fluoropolyether (functional PFPE(1)) comprising recurring units (R1), said recurring units comprising at least one ether linkage in the main chain and at least one fluorine atom (fluoropolyoxyalkylene chain), and at least one functional end group selected from the group consisting of —COOH and —CONH 2 ; and

at least one functional (per)fluoropolyether (functional PFPE(2)) comprising recurring units (R1) as defined above and at least one functional end group selected from the group consisting of —COCF 3 and its hydroxylated derivative —C(OH) 2 CF 3 .

2. The process of claim 1 , wherein the fluorinated ether fluid free from functional groups (fluid (H-1)) complies with formula (I A) or (I B) here below:

RO—(R f ) r —R′  (I A)

RO-J-(O) j —R′  (I B)

wherein:

R and R′, equal or different from each other, are independently selected from the group consisting of —C m F 2m+1 , —C n F 2n+1-h H h , —C p F 2p+1-h X h′ , —C z F 2z OC y F 2y+1 , —C u F 2u-u′ H u′ OC w F 2w+1-w′ H w′ , and —C u F 2u-u′ H u′ OC y F 2y+1 groups, with m, n, p, u, w, y, z being integers from 1 to 8, h, h′, u′ and w′ being integers ≧1, chosen so that h≦2n+1, h′≦2p+1, u′≦2u, w′≦2w+1, X being a halogen atom selected from the group consisting of CI, Br, and I;

r is equal to 0 or 1; j is equal to 0 or 1;

R f is a fluoropolyoxyalkylene chain comprising recurring units R o , said recurring units being selected from the group consisting of:

(i) —CFXO—, wherein X is F or CF 3 ;

(ii) —CF 2 CFXO—, wherein X is F or CF 3 ;

(iii) —CF 2 CF 2 CF 2 O—;

(iv) —CF 2 CF 2 CF 2 CF 2 O—;

(v) —(CF 2 ) k —CFZ—O—, wherein k is an integer from 0 to 3, and Z is a group of general formula —OR F T 3 , wherein R F is a fluoropolyoxyalkylene chain comprising a number of recurring units from 0 to 10, said recurring units being selected from the group consisting of —CFXO—, —CF 2 CFXO—, —CF 2 CF 2 CF 2 O—, and —CF 2 CF 2 CF 2 CF 2 O—, with each of X being independently F or CF 3 , and T 3 is a C 1 -C 5 perfluoroalkyl group; and

mixtures thereof; and

J is a divalent hydrocarbon radical having 1 to 12 carbon atoms, linear or branched, aliphatic or aromatic.

3. The process of claim 1 , wherein the fluid (H-1) complies with formula (II A) or (II B) here below:

R*O—(R f ) r —R*′  (II A)

R*O-J-(O) j —R*′  (II B),

wherein:

R* and R*′, equal to or different from each other, are independently selected from the group consisting of —C m F 2m+1 , —C n F 2n+1-h H h , —C z F 2z OC y F 2y+1 , —C u F 2u-u′ H u′ OC w F 2w+1-w′ H w′ , and —C u F 2u-u′ H u′ OC y F 2y+1 groups, with m, u, w, y, z being integers from 1 to 8, h, u′ and w′ being integers ≧1, chosen so that h≦2n+1, u′≦2u, w′≦2w+1;

R f is a fluoropolyoxyalkylene chain comprising recurring units R o , said recurring units being selected from the group consisting of:

(i) —CFXO—, wherein X is F or CF 3 ;

(ii) —CF 2 CFXO—, wherein X is F or CF 3 ;

(iii) —CF 2 CF 2 CF 2 O—;

(iv) —CF 2 CF 2 CF 2 CF 2 O—;

(v) —(CF 2 ) k —CFZ—O—, wherein k is an integer from 0 to 3, and Z is a group of general formula —OR F T 3 , wherein R F is a fluoropolyoxyalkylene chain comprising a number of recurring units from 0 to 10, said recurring units being selected from the group consisting of —CFXO—, —CF 2 CFXO—, —CF 2 CF 2 CF 2 O—, and —CF 2 CF 2 CF 2 CF 2 O—, with each of X being independently F or CF 3 , and T 3 is a C 1 —O 5 perfluoroalkyl group; and

mixtures thereof;

J is a divalent hydrocarbon radical having 1 to 12 carbon atoms, linear or branched, aliphatic or aromatic;

r is equal to 0 or 1; and

j is equal to 0 or 1.

4. The process of claim 1 , wherein the fluid (HFPE) complies with formula (II A):

R*O—(R f ) r —R*′,

wherein:

R* and R*′, equal to or different from each other, are independently selected from the group consisting of —C m F 2m+1-h H h , —C u F 2u-u′ H u′ OC w F 2w+1-w′ H w′ , and —C u F 2u-u′ H u′ OC y F 2y+1 groups, with m, n, u, w, y being integers from 1 to 8, h, u′ and w′ being integers ≧1, chosen so that h≦2n+1, u′≦2u, w′≦2w+1, with the proviso that at least one of R* and R*′ is a —C n F 2n+1-h H h group;

R f is a fluoropolyoxyalkylene chain comprising recurring units R o , said recurring units being selected from the group consisting of:

(i) —CFXO—, wherein X is F or CF 3 ;

(ii) —CF 2 CFXO—, wherein X is F or CF 3 ;

(iii) —CF 2 CF 2 CF 2 O—;

(iv) —CF 2 CF 2 CF 2 CF 2 O—;

(v) —(CF 2 ) k —CFZ—O—, wherein k is an integer from 0 to 3, and Z is a group of general formula —OR F T 3 , wherein R F is a fluoropolyoxyalkylene chain comprising a number of recurring units from 0 to 10, said recurring units being selected from the group consisting of —CFXO—, —CF 2 CFXO—, —CF 2 CF 2 CF 2 O—, and —CF 2 CF 2 CF 2 CF 2 O—, with each of X being independently F or CF 3 , and T 3 is a C 1 —O 5 perfluoroalkyl group; and

mixtures thereof; and

r is equal to 1.

5. The process of claim 1 , wherein the fluid (PFPE) complies with formula (II A):

R*O—(R f ) r —R*′,

wherein:

R* and R*′, equal to or different from each other, are independently selected from the group consisting of —C—F 2m+1 groups, with m being integers from 1 to 8;

R f is a fluoropolyoxyalkylene chain comprising recurring units R o , said recurring units being selected from the group consisting of:

(i) —CFXO—, wherein X is F or CF 3 ;

(ii) —CF 2 CFXO—, wherein X is F or CF 3 ;

(iii) —CF 2 CF 2 CF 2 O—;

(iv) —CF 2 CF 2 CF 2 CF 2 O—;

(v) —(CF 2 ) k —CFZ—O—, wherein k is an integer from 0 to 3, and Z is a group of general formula —OR F T 3 , wherein R F is a fluoropolyoxyalkylene chain comprising a number of recurring units from 0 to 10, said recurring units being selected from the group consisting of —CFXO—, —CF 2 CFXO—, —CF 2 CF 2 CF 2 O—, and —CF 2 CF 2 CF 2 CF 2 O—, with each of X being independently F or CF 3 , and T 3 is a C 1 —O 5 perfluoroalkyl group; and

mixtures thereof; and

r is equal to 1.

6. The process of claim 1 , wherein the functional PFPE(1) and the functional PFPE(2), comply with formula (IV) here below:

T 1 -(CFX) p —O—R f ″—(CFX) p′ -T 2   (IV)

wherein:

each of X is independently F or CF 3 ; when X is F, p and/or p′, equal to or different from each other, are integers up to 3; when X is CF 3 , p and/or p′ are equal to 1;

R f ″ is a fluoropolyoxyalkylene chain comprising recurring units R o′ , said recurring units being selected from the group consisting of:

(i) —CFXO—, wherein X is F or CF 3 ,

(ii) —CF 2 CFXO—, wherein X is F or CF 3 ,

(iii) —CF 2 CF 2 CF 2 O—,

(iv) —CF 2 CF 2 CF 2 CF 2 O—,

(v) —(CF 2 ) k —CFZ—O— wherein k is an integer from 0 to 3, and Z is a group of general formula —OR F T 3 , wherein R F is a fluoropolyoxyalkylene chain comprising a number of recurring units from 0 to 10, said recurring units being selected from the group consisting of —CFXO—, —CF 2 CFXO—, —CF 2 CF 2 CF 2 O—, and —CF 2 CF 2 CF 2 CF 2 O—, with each of X being independently F or CF 3 , and T 3 is a C 1 -C 3 perfluoroalkyl group; and

mixtures thereof;

in functional PFPE(1), at least one of T 1 and T 2 , which are the same or different from each other, is a functional end group selected from the group consisting of —COOH and —CONH 2 , the remaining T 1 or T 2 , if any, being a fluorine atom or a C 1 -C 3 (per)fluoroalkyl group optionally containing H or Cl; and

in functional PFPE(2), at least one of T 1 and T 2 , which are the same or different from each other, is a functional end group selected from the group consisting of —COCF 3 and its hydroxylated derivative —C(OH) 2 CF 3 , the remaining T 1 or T 2 , if any, being a fluorine atom or a C 1 -C 3 (per)fluoroalkyl group optionally containing H or Cl.

7. The process of claim 6 , wherein the functional PFPE(1) and the functional PFPE(2) comply with formula (V):

T 1 CF 2 O(CF 2 O) m (CF 2 CF 2 O) s (CF 2 CF(CF 3 )O) n (CF(CF 3 )O) r CF 2 T 2   (V)

wherein:

the perfluorooxyalkylene units with indexes m, n, r and s are randomly distributed along the chain, the values of m, n, r and s being such that the average molecular weight ranges from 400 to 20, 000.

8. The process of claim 1 , wherein the heat transfer medium comprises from 5 to 10% wt with respect to the total weight of the composition of a mixture of functional PFPE (1) and functional PFPE (2).

9. The process of claim 1 , wherein the heat sink is a primary refrigeration system.

10. The process of claim 1 , wherein the heat source is a primary heating system.

11. The process of claim 1 , wherein the heat source is a cooling compartment on board of aircrafts, vehicles or boats, while the heat sink is a primary refrigeration system.

12. The process of claim 1 , wherein the heat sink is a heating compartment on board of aircrafts, vehicles or boats, while the heat source is a primary heating system.

13. The process of claim 1 , wherein the functional PFPE(1) and the functional PFPE(2) are two distinct compounds.