Water based printable coatings
View Patent ↗Various aqueous top coat compositions are described. The compositions include one or more polyurethane dispersions, silica, crosslinker(s), acrylic polymers, and an optional water soluble polyester. The compositions can be used to form top coats which exhibit good resistance to scratches and solvents, and improved ink retention.
1. An aqueous top coat composition comprising:
10 to 85 parts by weight of polyurethanes; wherein the polyurethanes include a hard polyurethane component and a soft polyurethane component;
10 to 60 parts by weight of one or more water soluble linear polyesters, wherein the water soluble linear polyester is a linear polyester prepared from the polycondensation of glycols and dicarboxylic acids and has a molecular weight from 5,000 to 20,000 and wherein the water soluble linear polyester has a glass transition temperature from 36° C. to 52° C.;
0 to 80 parts by weight of one or more acrylic polymers;
0.01 to 3 parts by weight of silica; and
0.05 to 3 parts by weight crosslinker for crosslinking at least the polyurethane components.
2. The top coat composition of claim 1 wherein the silica is amorphous silica.
3. The top coat composition of claim 1 wherein the silica has an average particle size of from 4 μm to 6 μm.
4. The top coat composition of claim 1 wherein the crosslinker includes an aziridine crosslinker.
5. The top coat composition of claim 1 wherein the composition comprises from 15 to 80 parts of polyurethanes and 10 to 70 parts of one or more acrylic polymers.
6. The top coat composition of claim 1 wherein the composition comprises from 15 to 25 parts by weight of water soluble linear polyesters.
7. The top coat composition of claim 1 wherein the composition comprises from 0.01 to 2 parts by weight silica.
8. The top coat composition of claim 1 wherein the composition comprises from 0.10 to 1 part by weight crosslinker.
9. The top coat composition of claim 1 further comprising at least one additional component selected from the group consisting of an antiblock agent, an acrylic polymer, and combinations thereof.
10. The top coat composition of claim 1 wherein at least one of the polyurethanes or the one or more water soluble polyesters comprise water, and further wherein the top coat composition comprises additional water added as a separate component.
11. A top coated substrate comprising:
a polymeric substrate; and
a top coat disposed on the substrate, the top coat being formed from an aqueous top coat composition including 10 to 85 parts by weight polyurethanes, wherein the polyurethanes include a hard polyurethane component and a soft polyurethane component, 0 to 80 parts by weight of one or more acrylic polymers and 10 to 60 parts by weight of one or more water soluble polyesters, wherein the water soluble linear polyester is a linear polyester prepared from the polycondensation of glycols and dicarboxylic acids and has a molecular weight from 5,000 to 20,000 and wherein the water soluble linear polyester has a glass transition temperature from 36° C. to 52° C., 0.01 to 3 parts by weight of silica, and 0.05 to 3 parts by weight crosslinkers for crosslinking at least the polyurethane component.
12. The top coated substrate of claim 11 wherein the substrate is bi-axially oriented polypropylene (BOPP).
13. The top coated substrate of claim 11 wherein the substrate is machine direction orientation (MDO) film.
14. The top coated substrate of claim 11 wherein the substrate is polyester film.
15. The top coated substrate of claim 11 wherein the silica is amorphous silica.
16. The top coated substrate of claim 11 wherein the silica has an average particle size of from 4 μm to 6 μm.
17. The top coated substrate of claim 11 wherein the crosslinker includes an aziridine crosslinker.
18. The top coated substrate of claim 11 wherein the composition comprises from 12 to 27 parts by weight of polyurethanes.
19. The top coated substrate of claim 11 wherein the composition comprises from 15 to 25 parts by weight of water soluble linear polyesters.
20. The top coated substrate of claim 11 wherein the composition comprises from 0.01 to 2 parts by weight silica.
21. The top coated substrate of claim 11 wherein the composition comprises from 0.05 to 1 part by weight crosslinker.