Elimination of application streaks of coatings using short fibers
Waterborne polyurethane coating compositions comprising a polyol, an isocyanate crosslinker, and a small amount of thermoplastic microfibers, e.g., polyolefin microfibers, having a length of less than 1 mm, exhibit a much less sag, roller lines and other surface imperfections upon application to a substrate, in particular a vertical substrate such as a wall, than analogous water borne polyurethane compositions that lack the microfibers.
1. A waterborne polyurethane coating composition comprising, by weight based on the total weight of the waterborne polyurethane coating composition: 10 to 60%, of a polyol, 5 to 60%, of an isocyanate crosslinker, 0.1 to 5.0%, thermoplastic microfibers having a fiber length of 1 mm or less and a diameter of from 0.001 to 0.025 mm, 10 to 40% TiO 2 , and 10 to 60% water, wherein the thermoplastic microfibers are polyolefin microfibers.
2. The waterborne polyurethane coating composition according to claim 1 wherein the polyol is a polymeric resin comprising hydroxy groups and the isocyanate crosslinker is an aliphatic isocyanate crosslinker.
3. The waterborne polyurethane coating composition according to claim 1 comprising, by weight based on the total weight of the waterborne polyurethane coating composition: 10 to 35% of a polymeric resin comprising hydroxyl groups, which resin comprises one or more acrylate and/or methacrylate polymer or co-polymer comprising a plurality of free hydroxyl groups, 10 to 35% of an aliphatic isocyanate crosslinker, 0.1 to 5.0%, polyolefin microfibers having a fiber length of 1 mm or less and a diameter of from 0.001 to 0.025 mm, 15 to 40% TiO 2 , and 15 to 50% water.
4. The waterborne polyurethane coating composition according to claim 3 wherein the polyolefin microfibers comprise high density polyethylene and/or low density polyethylene microfibers.
5. The waterborne polyurethane coating composition according to claim 3 wherein the polyolefin microfibers have a fiber length of 0.005 to 0.50 mm and a diameter of from 0.001 to 0.010 mm.
6. The waterborne polyurethane coating composition according to claim 5 wherein the polyolefin microfibers have a fiber length of from 0.010 to 0.25 mm, and a diameter of from 0.002 to 0.007 mm.
7. The waterborne polyurethane coating composition according to claim 1 wherein the isocyanate crosslinker comprises hexamethylene diisocyanate, hexamethylene diisocyanate dimer, hexamethylene diisocyanate trimer, and/or hexamethylene diisocyanate oligomers derived from 4 or more hexamethylene diisocyanate units.
8. The waterborne polyurethane coating composition according to claim 3 wherein the aliphatic isocyanate crosslinker comprises hexamethylene diisocyanate, hexamethylene diisocyanate dimer, hexamethylene diisocyanate trimer, and/or hexamethylene diisocyanate oligomers derived from 4 or more hexamethylene diisocyanate units.
9. The waterborne polyurethane coating composition according to claim 8 comprising: 15 to 25% of the polymeric resin comprising hydroxyl groups, 15 to 25% of the aliphatic isocyanate crosslinker, 0.2 to 3.0% of the polyolefin microfibers, 15 to 35% TiO.sub.2, 25 to 45% water, and 0 to 25% total of pigments, surfactants, dispersants, rheology modifiers, leveling agents, anti-foaming agents, other reactive or non-reactive resins, hardeners, cure accelerators, catalysts, delaying or blocking agent, solvents, reactive diluents, wetting agents, stabilizers, inhibitors, reinforcing agents, cement, sand, quartz silica, CaCO 3 , CaSO 4 , BaSO 4 , detergents, antistatic material, anti-slip agent, matting agent, UV blockers, hindered amine light stabilizers and/or antioxidants.
10. The waterborne polyurethane coating composition according to claim 9 comprising, 3 to 20% total of pigments, surfactants, dispersants, rheology modifiers, leveling agents, anti-foaming agents, other reactive or non-reactive resins, hardeners, cure accelerators, catalysts, delaying or blocking agent, solvents, reactive diluents, wetting agents, stabilizers, inhibitors, reinforcing agents, cement, sand, quartz silica, CaCO 3 , CaSO 4 , BaSO 4 , detergents, antistatic material, anti-slip agent, matting agent, UV blockers, hindered amine light stabilizers and/or antioxidants.
11. The waterborne polyurethane coating composition according to claim 9 wherein the polyolefin microfibers have a fiber length of 0.005 to 0.50 m, a diameter of from 0.001 to 0.010 mm and comprise high density polyethylene and/or low density polyethylene microfibers.
12. The waterborne polyurethane coating composition according to claim 1 , which is a wall coating composition.