Low foaming waterborne coating composition and use thereof
The present disclosure is directed to a waterborne coating composition having neutral pH that is low foaming and forms dry coating layer that has high hardness and high gloss. This disclosure is further directed to a coating composition comprising a crosslinking component comprising: (a) one or more alkylated melamines that are essentially unreactive to a polyisocyanate; and (b) a polyisocyanate. The coating composition can be particularly suitable for vehicle coatings and other industrial or consumer applications.
1. A process for forming a coating layer over a substrate, said process comprising the steps of:
A) providing a crosslinkable component comprising a film forming polymer having a crosslinkable functional group, wherein the crosslinkable functional group is a hydroxyl group, and wherein the crosslinkable component comprises in a range of from about 20% to about 80% of water, percent based on the total weight of the crosslinkable component;
B) providing a crosslinking component comprising: (a) an alkylated melamine that is essentially free from isocyanate reactive hydrogen such that the alkylated melamine is essentially unreactive to a polyisocyanate; and (b) a polyisocyanate having two or more free isocyanate crosslinking functional groups;
C) mixing said crosslinkable component with said crosslinking component to form a coating composition, wherein said coating composition is essentially free from acid catalyst;
D) applying said coating composition over said substrate to form a wet coating layer thereon; and
E) curing said wet coating layer at a temperature in a range of from about 80° C. to about 200° C. to form said coating layer.
2. The process of claim 1 , wherein the film forming polymer is selected from acrylic polymers, polyester polymers, polyurethane polymers, alkyd resins, or a combination thereof.
3. The process of claim 1 , wherein the alkylated melamine comprises an alkylation group selected from C1-C10 alkyls.
4. The process of claim 1 further comprising the steps of mixing a pigment, a solvent, an ultraviolet light stabilizer, an ultraviolet light absorber, an antioxidant, a hindered amine light stabilizer, a leveling agent, a rheological agent, a thickener, an antifoaming agent, a wetting agent, or a combination thereof, into said crosslinkable component or said coating composition.
5. The process of claim 1 , wherein said coating composition is at a pH in a range of from about 6.9 to about 8.1.
6. The process of claim 1 , wherein the weight ratio of melamine:polyisocyanate is in a range of from about 1:0.1 to about 1:10.
7. A coating composition comprising:
a) a crosslinkable component comprising a film forming polymers having a crosslinkable functional group, wherein the crosslinkable functional group is a hydroxyl group, and wherein the crosslinkable component comprises in a range of from about 20% to about 80% of water, percent based on the total weight of the crosslinkable component; and
b) a crosslinking component comprising: (a) an alkylated melamine that is essentially free from isocyanate reactive hydrogen such that the alkylated melamine is essentially unreactive to a polyisocyanate, and (b) a polyisocyanate having two or more free isocyanate crosslinking functional groups;
wherein the coating composition is essentially free from acid catalyst.
8. The coating composition of claim 7 , wherein the film forming polymer is selected from acrylic polymers, polyester polymers, polyurethane polymers, alkyd resins, or a combination thereof.
9. The coating composition of claim 7 , wherein the alkylated melamine comprises an alkylation group selected from C1-C10 alkyls.
10. The coating composition of claim 7 further comprising a pigment, a solvent, an ultraviolet light stabilizer, an ultraviolet light absorber, an antioxidant, a hindered amine light stabilizer, a leveling agent, a rheological agent, a thickener, an antifoaming agent, a wetting agent, or a combination thereof.
11. The coating composition of claim 7 , wherein the coating composition is at a pH in a range of from about 6.9 to about 8.1.
12. The coating composition of claim 7 , wherein the weight ratio of melamine:polyisocyanate is in a range of from about 1:0.1 to about 1:10.