Compositions of crosslinkable polyurethanes

1. Compositions comprising anionic ionomeric polyurethanes crosslinkable in a wide temperature range from 10° C. up to 200° C., said compositions comprising the following components:

I) an aqueous dispersion of a linear crosslinkable ionomeric polyurethane, containing carboxylic groups and having perfluoropolyether structure;

II) a crosslinking agent;

 the ratio between the equivalents of the functional groups of the crosslinking agent and of the carboxylic groups of component I) being at least 0.7 up to 1.5 said crosslinking agent being dispersible and/or soluble in the dispersion component I).

2. Compositions according to claim 1 , wherein the aqueous dispersion component I) has a dry residue from 20% to 40% by weight.

3. Compositions according to claim 1 , wherein the (per)fluoropolyether ionomeric polyurethanes of the dispersion component I) are obtained by reaction of the following monomers and macromers:

a) (per)fluoropolyether diols having a number average molecular weight from 400 to 5,000;

b) diisocyanates selected from one or more of the following:

OCN—R—NCO  (IA)

 wherein R has the following meanings:

C 2 –C 12 aliphatic bifunctional radical;

C 6 –C 18 cycloaliphatic or alkylen-cycloaliphatic, wherein optionally the cycloaliphatic ring can be substituted with one or more C 1 –C 3 alkyl groups,

 or

 R contains two cycloaliphatic rings, comprising each one NCO group joined by a C 1 –C 6 alkylene chain;

 C 6 –C 18 aromatic bifunctional radical, wherein the aromatic ring can be substituted with one or more C 1 –C 3 alkyl groups, or

 R contains two aromatic rings, each comprising one NCO group, joined by a C 1 –C 6 alkylene chain;

c) ionomeric diols, having a carboxylic function, of the following general formula:

 wherein:

T is a linear or branched C 2 –C 20 trivalent aliphatic radical;

the two hydroxyls can substitute also two different aliphatic chains, and are never on the same carbon atom;

optionally one or more of the following components:

d) hydrazine and/or C 2 –C 6 aliphatic diamines;

e) linear or branched C 2 –C 6 hydrogenated diols optionally containing one cycloaliphatic or aromatic ring having 6 carbon atoms and/or one or two oxygen atoms;

 in said polyurethane the equivalents of the —NCO groups are equal to the sum of the equivalents of the alcoholic —OH groups, optionally summed to the —NH 2 groups when the component d) is present.

4. Compositions according to claim 3 , wherein the amounts of the components in the polymer I), expressed in percentages by weight are the following:

component a) 60%–85%;

component b) 10%–35%;

component c) 3%–10%;

component d) and/or e) 0–10%,

 the total sum of the components being 100%; the carboxylic equivalent weight ranging from 2,000 to 6,000 g/eq.

5. Compositions according to claim 1 , wherein the bifunctional (per)fluoropolyethers indicated in a) have one or more of the following units statistically distributed along the chain: (CF 2 CF(CF 3 )O); (CF(CF 3 )CF 2 O); (CFYO) wherein Y is F or CF 3 ; (CF 2 CF 2 O); (CF 2 (CF 2 ) x′ CF 2 O) wherein x′ is an integer equal to 1 or 2; (CR 4 R 5 CF 2 CF 2 O) wherein: R 4 and R 5 are equal or different the one from the other and selected from H, Cl, and one fluorine atom of the perfluoromethylene unit can optionally be substituted with H, Cl or (per)fluoroalkyl.

6. Compositions according to claim 5 , wherein the bifunctional compounds a) have a number average molecular weight from 400 to 5,000 and are selected from the following with the perfluorooxyalkylene units statistically distributed along the chain:

—CF 2 —O—(CF 2 CF 2 O) P′ (CF 2 O) q′ —CF 2 —  (a′)

wherein:

p′ and q′ are numbers such that the q′/p′ ratio is comprised between 0.2 and 4, p′ being different from zero; and the number average molecular weight is in the above range;

—CFY—O—(CF 2 CF(CF 3 )O) r′ —(CF 2 CF 2 O) s′ —(CFYO) t′ —CFY—  (b′)

wherein:

Y is as above; r′, s′ and t′ are numbers such that r′+s′ is in the range 1–50, the t′/(r′+s′) ratio is comprised between 0.01 and 0.05, r′+s′ being different from zero, and the molecular weight is in the above range;

—CF(CF 3 )(OCF 2 CF(CF 3 )) u′ —OR′ f O—(CF(CF 3 )CF 2 O) u′ (CF(CF 3 )—  (c′)

wherein:

R′ f is a C 1 –C 3 perfluoroalkyl bifunctional radical; u′ is a number such that the number average molecular weight is in the above range;

CFYO—(CFYO) t′ —((CF 3 )CFCF 2 O) r′ —R′ f O—(CF 2 CF(CF 3 )O) r′ —(CFYO) t′ —CFY—  (c″)

wherein:

R′ f is a C 1 –C 3 perfluoroalkyl bifunctional radical;

r′, t′ and Y are as above; r′ and t′ such that the number average molecular weight is in the above range;

—CF 2 CF 2 O—(CF 2 (CF 2 ) x′ CF 2 O) v′ —CF 2 CF 2 —  (d′)

wherein:

v′ is a number such that the molecular weight is in the above range;

x′ is an integer equal to 1 or 2;

—CF 2 CH 2 —(OCF 2 CF 2 CH 2 ) w′ —OR′ f O—(CH 2 CF 2 CF 2 O) w′ —CH 2 CF 2 —  (e′)

wherein:

R′ f is as above; w′ is a number such that the number average molecular weight is in the above range;

the end groups of the bifunctional perfluoropolyethers component a) being of the —CH 2 —(OCH 2 CH 2 ) k′ —OH type, wherein k′ is a number comprised between 0 and 2.

7. Compositions according to claim 3 , wherein the diisocyanates b) are selected from the following: hexamethylendiisocyanate (HDI), trimethylhexamethylenediisocyanate, isophorone diisocyanate (IPDI), 4,4′-methylenebis (cyclohexylisocyanate) (H12-MDI), cyclohexyl-1,4-diisocyanate, 4,4′-methylenebis (phenylisocyanate) (MDI) or its isomers, toluene 2,4-diisocyanate (TDI) or its isomers, xylylene diisocyanate, naphthalene-1,5-diisocyanate, p-phenylen-diisocyanate.

8. Compositions according to claim 3 , wherein component c) is the 2,2-dimethyloipropionic acid having the following formula:

9. Compositions according to claim 3 , wherein the optional compounds d) are selected from ethylendiamine, hexamethylendiamine; the optional compounds e) are selected from 1,4-butandiol, 1,4-cyclohexylendimethylol, hydroquinone bis(2-hydroxyethylether).

10. Compositions according to claim 1 , containing organic solvents in an amount lower than or equal to 7% by weight.

11. Compositions according to claim 1 , wherein the crosslinking agent component II) has functionality≧2 and is selected from polyfunctional aziridines, methoxy-methylolated melamines, intermediates for ureic resins, carbodiimides, hydrodispersible or water-soluble blocked isocyanates, hydrodispersible epoxy- alkoxysilanes, hydro-dispersible zirconium salts.

12. Compositions according to claim 1 , comprising organic or inorganic additives selected from opacifying agents and pigments, selected from silicas, metal oxides, in particular titanium dioxide, and solid lubricants.

13. Crosslinked compositions according to claim 1 .

14. A method of preparing coatings on substrata by spraying, dipping, filmspreading bar, brush or other known conventional technique comprising utilizing the compositions of claim 1 .

15. The method according to claim 14 , wherein the compositions are applied to surface of plastic material or skins.

16. The method according to claim 14 , wherein the compositions are applied on flexible substrata having a low hardness.