Self-lubricating coating composition
The invention pertains to compositions comprising at least one polymer or precursors thereof, at least one liquid medium and a plurality of microcapsules having a cross-linked polymeric shell and a core containing at least one (per)fuoropolyether compound comprising a (per)fluoropolyoxyalkylene chain being a sequence of recurring units having at least one catenary ether bond and at least one fluorocarbon moiety.
1. A coating composition [composition (C)] comprising:
at least one polymer [polymer (A)] or precursors (P) of said polymer (A),
a liquid medium [medium (E)] and
a plurality of microcapsules [capsules (M)], said capsules (M) having a cross-linked polymeric shell and a core containing at least one (per) fuoropolyether compound [compound (PFPE)] comprising a (per) fluoropolyoxyalkylene chain [chain (Rf)], said chain (Rf) being a sequence of recurring units having at least one catenary ether bond and at least one fluorocarbon moiety,
wherein an amount of the at least one polymer [polymer (A)] in the composition (C) is provided in a greater amount than both of an amount of the liquid medium [medium (E)] and an amount of the plurality of microcapsules capsules (M)]; and
wherein the amounts of the liquid medium [medium (E)] and the plurality of microcapsules [capsules (M)] are relative to the amount of the at least one polymer [polymer (A)].
2. The composition (C) according to claim 1 , wherein said compound (PFPE) complies with formula (I):
Y # —(CFX # ) m —O(R f )(CFX*) n —Y* (I)
wherein:
Y # and Y*, equal to or different from each other, are selected from the group consisting of F, Cl, and a C 1 -C 3 perfluoroalkyl group;
m and n, equal to or different from each other, are integers equal to or greater than 1;
X # and X*, equal to or different from each other, are selected from the group consisting of F and a C 1 -C 3 perfluoroalkyl group;
Rf is said chain (Rf).
3. The composition (C) according to claim 1 , wherein said chain (Rf) is a sequence of recurring units comprising repeating units independently selected from the group consisting of:
—CFXO—, wherein X is F or CF 3 ;
—CFXCFXO—, wherein X, equal or different at each occurrence, is F or CF 3 , with the proviso that at least one of X is —F;
—CF 2 CF 2 CW 2 O—, wherein each of W, equal or different from each other, are F, Cl, H;
—CF 2 CF 2 CF 2 CF 2 O—;
—(CF 2 ) j —CFZ—O— wherein j is an integer from 0 to 3 and Z is a group of general formula —O—R (f-a) -T, wherein R( f-a ) is a fluoropolyoxyalkylene chain comprising a number of repeating units from 0 to 10, said recurring units being chosen among the following: —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 being a C 1 -C 3 perfluoroalkyl group.
4. The composition (C) according to claim 1 , comprising at least one polyisocyanate and at least one polyol as precursors (P) of a polyurethane.
5. The composition (C) according to claim 4 , wherein said at least one polyisocyanate is selected among polyisocyanurates and biurets and adducts of diisocyanates.
6. The composition according to claim 5 , wherein said at least one polyisocyanate is a trimer of hexamethylendiisocyanate (HDI) or a trimer of isophorone diisocyanate (IPDI).
7. The composition (C) according to claim 4 , wherein said at least one polyol is selected among polyacrylate, polyester, polyether and polycarbonate polyols.
8. The composition according to claim 7 , wherein said at least one polyol is solvent borne or water borne.
9. The composition according to claim 1 , wherein said medium (E) comprises at least one organic solvent.
10. The composition (C) according to claim 1 , wherein the amount of said medium (E) ranges from 5 to 50 phr, based on 100 weight part of the polymer (A).
11. The composition (C) according to claim 1 , wherein the amount of said capsules (M) ranges from 0.1 to 50 phr, based on 100 weight part of the polymer (A).
12. The composition (C) according to claim 1 , wherein said capsules (M) have an average diameter ranging from 4 μm to 8 μm.
13. The composition (C) according to claim 1 , wherein the weight ratio between the core and the cross-linked polymeric shell of said capsules (M) ranges from 20/80 to 80/20.
14. The composition (C) according to claim 1 , wherein the cross-linked polymeric shell of said capsules (M) has an average thickness ranging from 0.1 μm to 1.5 μm.
15. The composition (C) according to claim 1 , wherein said cross-linked polymeric shell is obtained by cross-linking at least one monomer or polymer, or a mixture of monomers or polymers, when polymerized, said monomer(s) bearing at least one reactive function selected from the group consisting of acrylate, methacrylate, vinyl ether, N-vinyl-ether, mercaptoester, thiolen, siloxane, epoxy, oxetan, urethane, isocyanate, and peroxide, said polymer(s) being selected among: polyethers, polyesters, polyurethanes, polyureas, polyethylene glycols, polypropylene glycols, polyamides, polyacetals, polyimides, polyolefins, polysulfides, and polydimethylsiloxanes, said polymers bearing at least one reactive function selected from the group consisting of acrylate; methacrylate; vinyl ether; N-vinyl ether; mercaptoester; thiolen; siloxane; epoxy; oxetan; urethane; isocyanate; and peroxide.
16. Process for preparing the coating composition (C) according to claim 1 , comprising mixing said at least one polymer (A), or precursors thereof (P), and said capsules (M) into said at least one medium (E).
17. Method for forming an assembly comprising a substrate(S) and a coating layer [layer (L)] adhered to at least part of said substrate(S), said method comprising: coating at least part of said substrate(S) with the above identified composition (C), thus obtaining a wet coating layer [wet layer (WL)], and subsequently drying said wet layer (WL), thus obtaining the layer (L).
18. An assembly including a substrate(S) and a coating layer [layer (L)] adhered to at least a part of said substrate(S), wherein said layer (L) is made from composition (C) according to claim 1 .